JP6121295B2 - Tire durability test method - Google Patents

Description

  The present invention relates to a tire durability test method. Specifically, the present invention relates to a method for durability test of a pneumatic tire belt.

  Pneumatic tires deteriorate with long-term use. This deterioration is promoted by heat generation, rubber oxidation, repeated strain, and the like. One of the problems caused by this deterioration is breaker edge loose (hereinafter referred to as BEL). This BEL is a phenomenon in which the end portion of the belt is repeatedly fatigued by strain and heat, and the top rubber (rubber member) is destroyed. This evaluation of BEL resistance is also evaluated using a deteriorated tire. Actually using and deteriorating the tire in order to obtain this deteriorated tire requires a long run and is not efficient.

  For this reason, pseudo deterioration methods such as a method of filling a tire with a gas having a high oxygen concentration and a method of exposing the tire to a high temperature atmosphere are used as a method of deteriorating the tire. Durability is evaluated by evaluating the tire thus deteriorated.

JP 2006-337100 A JP 2004-233218 A

  However, in the case of a tire that has been artificially deteriorated, it is not easy to similarly reproduce the damage that occurs in a tire in the market. In an evaluation test of BEL resistance using a pseudo-degraded tire, damage to the bead portion or tread often occurs before BEL occurs. It is not easy to experimentally reproduce BEL generated in tires on the market.

  An object of the present invention is to provide a method for evaluating a breaker edge loose resistance (BEL resistance) of a tire.

The pneumatic tire durability test method according to the present invention includes a deterioration process, a traveling process, and a determination process. In this deterioration process, the tire is deteriorated in an atmosphere at a temperature higher than normal temperature. In this running process, the tire that has undergone the degradation process is run. In this determination step, it is determined whether or not the breaker edge loose of the tire that has passed through the traveling step has occurred.
This tire includes a tread and a belt. This degradation process prior to the complex elastic modulus ^E * _{b 0} of the belt of the tire, loss tangent Tanderutabi _0, the complex elastic modulus ^E * _{t 0} and loss tangent Tanderutati ₀ of the tread, the complex elastic modulus of the belt after the degradation step ^{E *} b ₁ , loss tangent tan δb ₁ , tread complex elastic modulus E ^* t _1, loss tangent tan δt ₁ , belt complex elastic modulus E ^* b ₂ , loss tangent tan δb ₂ , tread complex elastic modulus E ^* T ₂ and loss tangent tan δt ₂
As for the test conditions of this deterioration process, the ratio of the belt (E ^* b ₁ / E ^* b ₀ ) is 1.25 or more and 1.35 or less in the room temperature, oxygen concentration, tire pressure, and holding period, and the ratio (tan δb ₁ / tan δb ₀ ) is 0.88 or more and 0.92 or less, the tread ratio (E ^* t ₁ / E ^* t ₀ ) is 1.15 or more and 1.25 or less, and the ratio (tan δt ₁ / tan δt ₀ ) Is set to 0.83 or more and 0.87 or less.

Preferably, the indoor temperature, tire air pressure, load and slip angle, which are test conditions of the running process, are such that the belt ratio (E ^* b ₂ / E ^* b ₀ ) is 1.15 or more and 1.20 or less. (tanδb ₂ / tanδb ₀₎ becomes 0.80 or more 0.86 or less, the ratio of tread _{^{(E * t 2 / E *}} t 0) becomes 1.25 or more 1.30 or less, the ratio (tanδt ₂ / tan δt ₀ ) is set to be 0.79 or more and 0.85 or less.

Preferably, the test conditions for the deterioration process are in the following ranges.
Indoor temperature: 65 ° C to 75 ° C Oxygen concentration: 85% to 95% Tire pressure: 180 kPa to 220 kPa Retention period: 12 days to 16 days

Preferably, in the traveling step, the tire is caused to travel on the drum road surface. The test conditions for this running process are in the following range.
Indoor temperature: 25 ° C. or more and 35 ° C. or less Tire pressure: 220 kPa or more and 260 kPa or less Load: Maximum applied capacity 80% or more and 100% or less Speed: 80 km / h or more and 120 km / h or less Slip angle: 1.3 ° or more and 1.7 ° or less

  In the tire durability test method according to the present invention, BEL generated in the market can be accurately reproduced. As a result, the BEL resistance of the tire can be evaluated with high accuracy by using the tire that has been artificially deteriorated.

FIG. 1 is a cross-sectional view showing a pneumatic tire evaluated by the tire durability test method according to the present invention. FIG. 2 is a flowchart of a tire durability test method according to the present invention.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view showing a part of a pneumatic tire 2. Taking the tire 2 as an example, the durability evaluation method of the present invention will be described.

  In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. An alternate long and short dash line CL in FIG. 1 represents the equator plane of the tire 2. The tire 2 has a substantially symmetrical shape with respect to the equator plane. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a band 14, an inner liner 16, and a chafer 18. The tire 2 is a tubeless type. The tire 2 is attached to a sports utility vehicle (SUV).

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 20. The tread surface 20 is in contact with the road surface. The tread 4 is made of a crosslinked rubber having excellent wear resistance.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, the sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 22 and an apex 24 that extends radially outward from the core 22. The core 22 has a ring shape. The core 22 includes a non-stretchable wire (typically a steel wire) wound in the circumferential direction. The apex 24 is tapered outward in the radial direction. The apex 24 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a first carcass ply 26 and a second carcass ply 28. The first carcass ply 26 and the second carcass ply 28 are spanned between the beads 8 on both sides, and are along the inside of the tread 4 and the sidewall 6. The first carcass ply 26 and the second carcass ply 28 are folded around the core 22 from the inner side to the outer side in the axial direction. Although not shown in figure, the 1st carcass ply 26 and the 2nd carcass ply 28 consist of many parallel cords and topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 10 having a bias structure may be employed.

  The belt 12 is located inside the tread 4. The belt 12 is located outside the carcass 10 in the radial direction. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes an inner layer 30 and an outer layer 32. The outer layer 32 is located on the radially outer side of the inner layer 30. In the tire 2, the axial width of the inner layer 30 is larger than the axial width of the outer layer 32. Although not shown, each of the inner layer 30 and the outer layer 32 includes a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is not less than 10 ° and not more than 35 °. The cord inclination direction of the inner layer 30 is opposite to the cord inclination direction of the outer layer 32. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The band 14 is located between the tread 4 and the belt 12. The band 14 includes a pair of edge bands 34. These edge bands 34 are spaced apart in the axial direction. The edge band 34 is located outside the belt 12 in the radial direction. In addition, this band 14 may be comprised from the full band extended from the axial direction one end side of the tread 4 to the other axial end side through the center.

  Although not shown, the edge band 34 is made of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally. The band 14 has a so-called jointless structure. The absolute value of the angle formed by the cord with respect to the circumferential direction is less than 2.0 °.

  The inner liner 16 is joined to the inner peripheral surface of the carcass 10. The inner liner 16 is made of a crosslinked rubber. For the inner liner 16, rubber having excellent air shielding properties is used. The inner liner 16 holds the internal pressure of the tire 2. The chafer 18 is located in the vicinity of the bead 8. When the tire 2 is incorporated into the rim, the chafer 18 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected. The chafer 18 is usually made of cloth and rubber impregnated in the cloth. A chafer 18 made of a single rubber may be used.

  FIG. 2 is a flowchart showing a durability evaluation method according to the present invention. With reference to FIG. 2, the durability evaluation method according to the present invention will be described using the tire 2 as an example. This durability evaluation method includes a deterioration process (STEP 1), a travel process (STEP 2), and a determination process (STEP 3). In this method, a tire 2 to be evaluated for the presence or absence of occurrence of BEL is prepared. This tire 2 is an unused tire.

  In the deterioration process of FIG. 2, the tire 2 is subjected to deterioration processing. In this deterioration process, the tire 2 is incorporated into a regular rim to obtain a tire assembly. The tire assembly is filled with air. The tire assembly is placed in a room where the temperature and oxygen concentration are controlled while being filled with air. The tire assembly is placed in this room for a predetermined holding period. In this deterioration process, the indoor temperature, the indoor oxygen concentration, the tire air pressure, and the indoor holding period mainly contribute to the promotion of the deterioration of the tire 2.

  By the deterioration process of this deterioration process, the tire 2 is brought close to the deterioration level of the tire 2 after running on the market. The deterioration level of the tire 2 after running on the market in the present invention means a limit level that can be used as a tire. That is, in this deterioration process, the tire 2 is deteriorated to a level close to that level that does not reach the limit level that can be used as a tire.

The complex elastic modulus of the degradation process prior to the belt 12 the tire 2 and ^E * _{b 0,} a loss tangent and tanδb _0. The complex elastic modulus of the tread 4 and ^E * _{t 0,} the loss tangent and tanδt _0. The complex elastic modulus E ^* b ₁ of the belt 12 after this deterioration process is set, and the loss tangent is set to tan δb ₁ . The complex elastic modulus of the tread 4 is E ^* b ₁ , and the loss tangent is tan δt ₁ . At this time, the ratio (E ^* b ₁ / E ^* b ₀ ) of the indoor temperature, the indoor oxygen concentration, the tire air pressure, and the indoor holding period is 1.25 or more and 1.35 or less, and the ratio (tan δb ₁ / Tan δb ₀ ) is 0.88 or more and 0.92 or less, the ratio (E ^* t ₁ / E ^* t ₀ ) is 1.15 or more and 1.25 or less, and the ratio (tan δt ₁ / tan δt ₀ ) is 0. .83 or more and 0.87 or less.

The tire 2 is subjected to a deterioration process, for example, under the following conditions.
Indoor temperature: 65 ° C to 75 ° C Oxygen concentration: 85% to 95% Tire pressure: 180 kPa to 220 kPa Retention period: 12 days to 16 days

  In the traveling process of FIG. 2, the tire assembly that has undergone the deterioration process is attached to a drum testing machine. The tire 2 is run on the drum of a drum testing machine. The diameter of this drum is generally 1707.6 mm. In this traveling process, the room temperature, tire air pressure, load applied to the tire assembly, traveling speed, and slip angle mainly contribute to the generation of BEL.

The complex elastic modulus of the belt 12 after the travel path and ^E * _{b 2,} a loss tangent and tanδb _2. The complex elastic modulus of the tread 4 and ^E * _{b 2,} a loss tangent and tanδt _2. At this time, the ratio (E ^* b ₂ / E ^* b ₀ ) of the indoor temperature, tire air pressure, load, and slip angle is 1.15 or more and 1.20 or less, and the ratio (tan δb ₂ / tan δb ₀ ) is 0. 80 to 0.86, the ratio (E ^* t ₂ / E ^* t ₀ ) is 1.25 to 1.30, and the ratio (tan δt ₂ / tan δt ₀ ) is 0.79 to 0.85 It is set to be. Thereby, the tire 2 is brought to the deterioration level of the tire 2 after running on the market.

In this traveling process, the tire 2 is subjected to deterioration processing, for example, under the following conditions.
Indoor temperature: 25 ° C. or more and 35 ° C. or less Tire pressure: 220 kPa or more and 260 kPa or less Load: Maximum applied capacity 80% or more and 100% or less Speed: 80 km / h or more and 120 km / h or less Slip angle: 1.3 ° or more and 1.7 ° or less

  In this determination process, the tire 2 that has obtained the traveling process is inspected. The belt 12 is inspected for damage. If the belt 12 is not damaged at the deterioration level of the tire 2 after running on the market, a good determination is made. If the belt 12 is damaged, a failure is determined. Based on the determination result, the tire 2 can be further improved and a tire having excellent durability can be developed.

  In this method, the deterioration condition of the deterioration process is set so that the ratio of the complex elastic modulus and loss tangent before and after the deterioration process falls within a predetermined range. To be close to. Thereby, a tire for evaluating BEL resistance in the running process and the determination process can be obtained in a short period of time. Through this deterioration process, the occurrence of BEL can be accurately reproduced. Furthermore, the occurrence of BEL can be reproduced by a relatively short traveling test in the traveling process.

  Since the running condition of the running process is set so that the ratio between the complex elastic modulus before and after running and the loss tangent is in a predetermined range, the tire 2 is set to the deterioration level of the tire 2 after running on the market. Thereby, the presence or absence of generation | occurrence | production of BEL in the market of the tire 2 can be evaluated accurately.

  The deterioration process condition of this deterioration process and the determination method of the driving condition of a driving process are demonstrated to this tire 2 as an example.

A rubber test piece of the belt 12 of the unused tire 2 and a rubber test piece of the tread 4 are prepared. The complex elastic modulus E ^* b ₀ and the loss tangent tan δb _{0 of the} belt 12 are measured. The complex elastic modulus E ^* b ₀ and the loss tangent tan δb ₀ are obtained using this rubber test piece. The rubber test piece has a size of 40 mm × 4 mm × 2 mm. A sine wave amplitude is given to this rubber test piece, and the complex elastic modulus E ^* b ₀ and loss tangent tan δb _{0 of the} belt 12 are obtained from the stress. Similarly, the complex elastic modulus E ^* t ₀ and the loss tangent tan δt ₀ are obtained from the rubber test piece of the tread 4.

This rubber test piece is subjected to deterioration treatment in the deterioration process. The rubber test piece is subjected to a deterioration treatment by applying stress instead of air pressure. A rubber test piece of the belt 12 after the deterioration process and a rubber test piece of the tread 4 are prepared. From the rubber test piece of the belt 12, the complex elastic modulus E ^* b ₁ and the loss tangent tan δb ₁ are measured. From the rubber specimen of the tread 4, the complex elastic modulus E ^* t ₁ and the loss tangent tan δt ₁ are measured.

From the obtained complex elastic modulus E ^* b ₀ and loss tangent tan δb ₀ and the complex elastic modulus E ^* b ₁ and loss tangent tan δb ₁ , the ratio (E ^* b ₁ / E ^* b ₀ ) and ratio (tan δb ₁ / tan δb ₀ ) is calculated. It is determined whether the ratio (E ^* b ₁ / E ^* b ₀ ) is 1.25 or more and 1.35 or less and the ratio (tan δb ₁ / tan δb ₀ ) is 0.88 or more and 0.92 or less.

From the obtained complex elastic modulus E ^* t ₀ and loss tangent tan δt ₀ and the complex elastic modulus E ^* t ₁ and loss tangent tan δt ₁ , the ratio (E ^* t ₁ / E ^* t ₀ ) and ratio (tan δt ₁ / tan δt ₀ ) is calculated. It is determined whether the ratio (E ^* t ₁ / E ^* t ₀ ) is 1.15 or more and 1.25 or less and the ratio (tan δt ₁ / tan δt ₀ ) is 0.83 or more and 0.87 or less.

The ratio ^{_{(E * b 1 / E *}} b 0), the ratio (tanδb ₁ / tanδb _0), the ratio ^{_{(E * t 1 / E *}} t 0), the ratio (tanδt ₁ / tanδt ₀₎ is within said range If there is, the deterioration process conditions of the tire 2 are the room temperature, the oxygen concentration in the room, the air pressure of the tire, and the holding period in the room in the deterioration process.

The ratio ^{_{(E * b 1 / E *}} b 0), the ratio (tanδb ₁ / tanδb _0), the ratio either of the aforementioned ^{_{(E * t 1 / E *}} t 0) and the ratio (tanδt ₁ / tanδt ₀₎ When it is not in the range, the deterioration processing condition of the deterioration process is changed. In the degradation treatment conditions after the change, in the same manner, the ratio ^{_{(E * b 1 / E *}} b 0), the ratio (tanδb ₁ / tanδb _0), the ratio ^{_{(E * t 1 / E *}} t 0) and the ratio (Tanderutati ₁ / tan δt ₀ ). The ratio ^{_{(E * b 1 / E *}} b 0), the ratio (tanδb ₁ / tanδb _0), the ratio ^{_{(E * t 1 / E *}} t 0) and the ratio (tanδt ₁ / tanδt ₀₎ is in the range of above Until then, the deterioration processing conditions are changed to obtain these ratios. If these ratios fall within the above-mentioned range, the deterioration process condition is determined as the process condition of the deterioration process.

The traveling condition of the traveling process is also determined in the same manner as the determination of the deterioration processing condition. Specifically, a rubber test piece of the belt 12 of the tire 2 after the deterioration process and a rubber test piece of the tread 4 are prepared. From the rubber test piece of the belt 12, the complex elastic modulus E ^* b ₁ and the loss tangent tan δb ₁ are measured. From the rubber specimen of the tread 4, the complex elastic modulus E ^* t ₁ and the loss tangent tan δt ₁ are measured. The rubber test piece of the belt 12 and the rubber test piece of the tread 4 are prepared by cutting out from the tire 2 after the traveling process. From the rubber test piece of the belt 12, the complex elastic modulus E ^* b ₂ and the loss tangent tan δb ₂ are measured. From the rubber test piece of the tread 4, the complex elastic modulus E ^* t ₂ and the loss tangent tan δt ₂ are measured.

The ratio of belt 12 (E ^* b ₂ / E ^* b ₀ ) is 1.15 or more and 1.20 or less, and the ratio (tan δb ₂ / tan δb ₀ ) is 0.80 or more and 0.86 or less. It is determined whether the ratio (E ^* t ₂ / E ^* t ₀ ) is 1.25 or more and 1.30 or less and the ratio (tan δt ₂ / tan δt ₀ ) is 0.79 or more and 0.85 or less.

The ratio ^{_{(E * b 2 / E *}} b 0), the ratio (tanδb ₂ / tanδb _0), the ratio ^{_{(E * t 2 / E *}} t 0), the ratio (tanδt ₂ / tanδt ₀₎ is within said range If there is, the room temperature, tire pressure, load and slip angle in the running process are determined as the running conditions of the tire 2. If these ratios are not within the aforementioned range, the driving conditions are repeatedly changed until these ratios are within the aforementioned range. If these ratios are within the above-mentioned range, the traveling condition is determined as the traveling condition of the tire 2.

  The BEL resistance of the tire 2 is evaluated based on the deterioration process conditions of the deterioration process determined in this way and the travel conditions of the travel process.

  Here, a method in which the deterioration treatment condition is determined using a rubber test piece made of the same material as the tread 4 and a rubber test piece made of the same material as the topping rubber of the belt 12 is exemplified. Instead of the rubber test piece, the tire 2 may be used similarly to the running condition. A plurality of tires 2 may be prepared, rubber pieces may be cut out from the unused tire 2 and the tire 2 that has undergone the degradation process, and the complex elastic modulus and loss tangent may be measured.

In the present invention, the complex elastic modulus and loss tangent are measured according to the provisions of “JIS K 6394”. The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

In this invention, when the pressure Pt (Pa) of all the gases in the room and the partial pressure Ps (Pa) of oxygen in the room are used, the oxygen concentration (%) is calculated by the following formula.
(Ps / Pt) × 100

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Test 1]
[Example 1]
The tire shown in FIG. 1 was prepared. The tire size was “305 / 50R20 120H S / TZ04”. This tire was deteriorated in the deterioration process. The deterioration conditions of this deterioration process were an indoor temperature of 70 ° C., an oxygen concentration of 90%, a tire air pressure of 200 kPa, and a holding period of 14 days.

[Comparative Example 1-5]
A tire subjected to a deterioration process was obtained in the same manner as in Example 1 except that the holding period, the room temperature and the oxygen concentration were as shown in Table 1 below.

From these tires, a rubber test piece of a belt and a rubber test piece of a tread were cut out. From the rubber test piece of this belt, the complex elastic modulus E ^* b ₁ and the loss tangent tan δb ₁ after the deterioration process were measured. From the rubber specimen of the tread, the complex elastic modulus E ^* t ₁ and the loss tangent tan δt ₁ were measured. Complex modulus degradation step before these tires ^E * _{b 0,} a loss tangent Tanderutabi _0, complex elastic modulus ^E * _{t 0} and loss tangent Tanderutati ₀ Prefecture, the ratio _{^{(E * b 1 / E *}} b 0), the ratio (tanδb ₁ / tanδb _0), the ratio _{^{(E * t 1 / E *}} t 0) and the ratio (tanδt ₁ / tanδt ₀₎ was calculated. The results are shown in Table 1.

A tire of the same type as that of Example 1 was prepared after running on the market. This tire, the ratio ^{_{(E * b 2 / E *}} b 0), the ratio (tanδb ₂ / tanδb _0), the ratio ^{_{(E * t 2 / E *}} t 0) and the ratio (tanδt ₂ / tanδt ₀₎ is calculated It was. Considering deterioration in the running process described later, the ratio (E ^* b ₂ / E ^* b ₀ ), ratio (tan δb ₂ / tan δb ₀ ), ratio (E ^* t ₂ / E ^* t) after running on the market ₀₎ and the ratio (tanδt ₂ / tanδt _0), tire ratio after degradation treatment ^{_{(E * b 1 / E *}} b 0), the ratio (tanδb ₁ / tanδb _0), the ratio ^{(E _*} t 1 / E _* The standard values of t ₀ ) and ratio (tan δt ₁ / tan δt ₀ ) are set. A degradation processing condition that satisfies all of these standard values is searched. In Test 1, the deterioration condition of Example 1 was searched and selected as the deterioration processing condition.

[Test 2]
[Example 2]
The tire of Example 1 was prepared. This tire was run in the running process. The running conditions were an indoor temperature of 30 ° C., a tire air pressure of 240 kPa, a speed of 100 km / h, and a slip angle of 1.5 °. In this running, the tire was loaded with 90% of the maximum additional capacity. In this running process, the tire was run until damage could occur. The results are shown in Table 2.

[Example 3-4]
A tire after the traveling process was obtained in the same manner as in Example 2 except that the slip angle in the traveling process was as shown in Table 2 below. The tire was run until damage could occur. The results are shown in Table 2.

[Example 5-7]
A tire after the traveling process was obtained in the same manner as in Example 2 except that the retention period of the deterioration process and the slip angle of the traveling process were as shown in Table 2 below. The tire was run until damage could occur. The results are shown in Table 2.

  As shown in Table 2, in Example 4 and Example 7, chipping occurred in the shoulder portion of the tread before the occurrence of BEL. So-called chucking occurred. In Example 5 and Example 6, cracks occurred at the end of the belt between the belt and the carcass. In Example 2 and Example 3, cracks occurred at the end of the belt between the inner and outer layers of the belt. In Example 2 and Example 3, BEL seen in the tire after running on the market was reproduced. In the third embodiment, the traveling distance is longer, and the traveling time is shorter in the second embodiment. From this evaluation result, the superiority of the present invention is clear.

  The method described above can be widely applied to pneumatic tires as a method for evaluating BEL resistance.

2 ... tyre 4 ... tread 6 ... side wall 8 ... bead 10 ... carcass 12 ... belt 14 ... band 16 ... inner liner 18 ... chafer 20 ... .... Tread surface 22 ... Core 24 ... Apex 26 ... First carcass ply 28 ... Second carcass ply 30 ... Inner layer 32 ... Outer layer 34 ... Edge band

Claims (4)

It has a deterioration process, a traveling process, and a judgment process.
In this deterioration process, the tire is deteriorated in an atmosphere at a temperature higher than normal temperature,
In this running process, tires that have undergone a degradation process are run,
In this determination process, the presence or absence of occurrence of breaker edge looseness of the tire that has undergone the traveling process is determined,
This tire has a tread and a belt,
This degradation process prior to the complex elastic modulus ^E * _{b 0} of the belt of the tire, loss tangent Tanderutabi _0, the complex elastic modulus ^E * _{t 0} and loss tangent Tanderutati ₀ of the tread, the complex elastic modulus of the belt after the degradation step ^{E *} b ₁ , loss tangent tan δb ₁ , tread complex elastic modulus E ^* b _1, loss tangent tan δt ₁ , belt complex elastic modulus E ^* b ₂ , loss tangent tan δb ₂ , tread complex elastic modulus E ^{* When} t ₂ and loss tangent tan δt ₂
The indoor temperature, oxygen concentration, tire air pressure, and holding period, which are test conditions for the deterioration process, are such that the belt ratio (E ^* b ₁ / E ^* b ₀ ) is 1.25 or more and 1.35 or less, and the ratio (tan δb ₁ / tan δb ₀ ) is 0.88 or more and 0.92 or less, the tread ratio (E ^* t ₁ / E ^* t ₀ ) is 1.15 or more and 1.25 or less, and the ratio (tan δt ₁ / tan δt ₀ ) Is a durability test method for a pneumatic tire which is set to be 0.83 or more and 0.87 or less. The indoor temperature, tire air pressure, load, and slip angle, which are test conditions of the above-described running process, are such that the ratio of belts (E ^* b ₂ / E ^* b ₀ ) is 1.15 or more and 1.20 or less, and the ratio (tan δb ₂ / Tan δb ₀ ) is 0.80 or more and 0.86 or less, and the tread ratio (E ^* t ₂ / E ^* t ₀ ) is 1.25 or more and 1.30 or less, and the ratio (tan δt ₂ / tan δt ₀ ). The durability test method according to claim 1, which is set to be 0.79 or more and 0.85 or less. The durability test method according to claim 1 or 2, wherein the test conditions of the deterioration process are set to the following ranges.
Indoor temperature: 65 ° C to 75 ° C Oxygen concentration: 85% to 95% Tire pressure: 180 kPa to 220 kPa Retention period: 12 days to 16 days The durability test method according to claim 2 or 3, wherein the test conditions of the running process are set to the following range, and the tire is caused to run on the drum road surface.
Indoor temperature: 25 ° C. or more and 35 ° C. or less Tire pressure: 220 kPa or more and 260 kPa or less Load: Maximum applied capacity 80% or more and 100% or less Speed: 80 km / h or more and 120 km / h or less Slip angle: 1.3 ° or more and 1.7 ° or less

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