JP6516329B2 - Tire evaluation method - Google Patents

Description

  The present invention relates to a method of evaluating a tire. In particular, it relates to a method of evaluating the flowability of the sealant material after the tire has run.

  The tire may be provided with a sealant layer to increase the puncture resistance. The sealant layer is formed by applying a flowable sealant material to the inner surface of the tire. The sealant layer is provided radially inward of the tread. When a hole is made in the tire by the tire stepping on a nail or the like, the sealant material enters the hole from the inside of the tire. Sealing of the holes by the sealant material maintains the tightness of the tire.

  Because the sealant material is fluid, when the tire rotates at high speed, centrifugal force causes the sealant material to flow toward the center of the tread. This reduces the thickness of the sealant layer at the shoulder portion. In this sealant layer, it may happen that the hole formed in the shoulder can not be sufficiently closed. Furthermore, since the thickness of the sealant layer differs between the center portion and the shoulder portion of the tire, the uniformity may be affected. Because the thickness of the sealant layer is increased at the center of the tire, heat generation at this portion is increased. This can affect the high speed durability of the tire. The examination for suppressing the flow of the sealant material at the time of a run is reported by JP 2009-274530 A and JP 2011-37399 A.

JP, 2009-274530, A JP, 2011-37399, A

  Until now, in order to know the state of flow of the sealant material, a tire was mounted on a vehicle, and the vehicle actually traveled. For this tire, it has been performed to measure the thickness of the sealant layer at a predetermined place (for example, one center part and one shoulder part). In order to effectively control the flow of the sealant material, it is important to know in more detail how the sealant material flows. For this purpose, it is necessary to measure the thickness of the sealant layer from the center to the shoulder of the tire. In order to measure the thickness of the sealant layer from the center portion to the shoulder portion, it is conceivable to cut the tire after traveling in the direction perpendicular to the circumferential direction and observe the cross section. However, when the tire is cut, the sealant layer may be broken. If the sealant layer breaks down, the thickness of the sealant layer can not be accurately measured.

  An object of the present invention is to provide an evaluation method for accurately measuring the thickness of the sealant layer from the center portion to the shoulder portion.

  The present invention relates to a method of evaluating a tire provided with a sealant layer on its inner surface. This evaluation method includes the steps of storing the tire in a refrigerator, cutting the tire in a direction perpendicular to the circumferential direction, and measuring the thickness of the sealant layer in the cut cross section.

  Preferably, the evaluation method further includes the step of running the tire on a traveling test machine before the step of storing the tire in a refrigerator.

  Preferably, in the step of running the tire, the running speed and the running time of the tire are determined such that the temperature of the sealant layer is 80 ° C. or more and 95 ° C. or less.

  Preferably, the running speed of the tire in the step of running the tire is 180 km / h or more and 220 km / h or less, and the running time is 30 minutes or more.

  Preferably, the temperature in the refrigerator in the step of storing the tire in the refrigerator is -45 ° C or more and -35 ° C or less.

  Preferably, the storage time of the tire in the step of storing the tire in a refrigerator is 2 hours or more.

  Preferably, the time interval between removing the tire from the refrigerator and cutting the tire is within 15 minutes.

  This evaluation method includes the step of storing the tire in a refrigerator. The sealant material cures at low temperatures. The sealant layer whose thickness has changed due to the flow of the sealant material hardens in that state. In this evaluation method, the tire is cut in the direction perpendicular to the circumferential direction. The cured sealant layer is resistant to breakage even when cut. The thickness of the sealant layer is measured using this cross section. Thus, the thickness of the sealant layer from the center to the shoulder of the tire can be accurately measured.

FIG. 1 is a cross-sectional view of a tire provided with a sealant layer. FIG. 2 is a diagram schematically showing the state of a test according to a test method according to an embodiment of the present invention.

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

  FIG. 1 is a cross-sectional view of a tire 2 provided with a sealant layer. In this figure, the vertical direction is the radial direction of the tire 2, the lateral direction is the axial direction of the tire 2, and the perpendicular direction to the paper is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equatorial plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equatorial plane except for the tread pattern.

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of beads 8, a carcass 10, a belt 12, a band 14, an inner liner 16 and a sealant layer 18. Each sidewall 6 extends radially inward from the end of the tread 4. Each bead 8 is located radially inward of the sidewall 6. The carcass 10 is bridged between the beads 8. The belt 12 is located radially inward of the tread 4 and laminated with the carcass 10. The band 14 is laminated on the radially outer side of the belt 12. The inner liner 16 is located inside the carcass 10 and joined to the inner surface of the carcass 10. The sealant layer 18 is located inside the inner liner 16. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car. In FIG. 1, only the outline of the cross section of components other than the sealant layer 18 is shown.

  As shown in FIG. 1, the sealant layer 18 is located radially inward of the tread 4. The sealant layer 18 extends from the inside of one shoulder of the tread 4 to the inside of the other shoulder. A sealant layer 18 exists radially inward of a portion of the tread 4 in contact with the ground when the vehicle on which the tire 2 is mounted travels in a straight line and turns.

  The sealant layer 18 is formed by applying a flowable sealant material to the inner surface of the inner liner 16. The composition of this sealant material may be a general one based on butyl rubber and polybutene. When the tire 2 steps on a nail or the like, the tire 2 may have holes penetrating from the tread surface 20 to the inner surface of the inner liner 16. At this time, the sealant material enters the hole from the inside of the tire 2. The airtightness of the tire 2 is maintained by the sealant material closing the hole. Even if the tire 2 has a hole, the tire 2 can travel. The sealant layer 18 contributes to the improvement of the puncture resistance of the tire 2.

In this embodiment, the method of evaluating the thickness of the sealant layer 18 is
(1) a step of running the tire 2 on a running test machine,
(2) a step of storing the tire 2 in a refrigerator,
(3) cutting the tire 2 in a direction perpendicular to the circumferential direction; and (4) measuring the thickness of the sealant layer 18 in the cut cross section.

  In the step (1), the tire 2 is run on a running test machine. The situation in which the tire 2 is traveled by the traveling test machine 22 is schematically shown in FIG. In this embodiment, a drum type traveling tester 22 is used. Only the tire 2 and the drum 24 of the drum type traveling tester 22 are shown in FIG. The tire 2 is mounted on a regular rim and filled with air.

  In this process, the tire 2 is set in the traveling test machine 22. Thereby, the tire 2 and the traveling surface 26 of the drum 24 come into contact with each other. The tire 2 is pressed against the running surface 26 of the drum 24. Arrow F in FIG. 2 is a load applied to the tire 2 at this time. The magnitude of the load F applied to the tire 2 is adjustable. A predetermined load is loaded on the tire 2. The drum 24 is rotated in the direction of arrow A. Along with this, the tire 2 rotates in the direction of the arrow B. Thus, the tire 2 travels on the traveling surface 26. The rotational speed of the drum 24 is adjustable. In other words, the traveling speed of the tire 2 can be adjusted. The tire 2 travels at a predetermined speed.

  In the step (2), the tire 2 is removed from the traveling test machine 22. The tire 2 is stored in a refrigerator. The tire 2 is cooled by a refrigerator. This cures the sealant material. This cold storage cures the sealant layer 18.

  In the step (3), the tire 2 is taken out of the refrigerator. The tire 2 is cut in the direction perpendicular to the circumferential direction. That is, the tire 2 is cut into round slices. For example, a wire-type tire cutter is used for this cutting.

  In the step (4), the thickness of the sealant layer 18 is measured for the cut cross section. The thickness of the sealant layer 18 is measured at a desired position from the center of the tire 2 to the shoulder portion. The distribution of the sealant material from the center of the tire 2 to the shoulder is measured. This measurement is performed using, for example, a straight measure.

  In this embodiment, a drum type traveling tester 22 is used as a traveling tester. The traveling test machine 22 is not limited to the drum type. A belt type traveling test machine may be used. Other driving test machines may be used. Furthermore, the traveling test machine may not be used. The tire may be mounted on a vehicle and run on the road.

  In this embodiment, this evaluation method includes the above-mentioned step (1). This evaluation method may not have the step (1). The steps after the above (2) may be performed using a tire that has been used in the market. This makes it possible to measure the distribution of the sealant material in the tire after being used on the market. The above (2) and subsequent steps may be performed using an unused tire. Thereby, the distribution of the sealant material can be measured for the manufactured tire.

  Hereinafter, the operation and effect of the present invention will be described.

  In order to effectively control the flow of the sealant material, it is important to know in detail how the sealant material flows. For this purpose, it is necessary to measure the thickness of the sealant layer from the center to the shoulder of the tire. For this purpose, it is conceivable to cut the tire after traveling in a direction perpendicular to the circumferential direction and observe a cross section. However, since the sealant material has fluidity, the sealant layer may be broken when the tire is cut. If the sealant layer breaks down, the thickness of the sealant layer can not be accurately measured.

  This evaluation method includes the step of storing the tire 2 in a refrigerator. The sealant material cures at low temperatures. The sealant layer 18 whose thickness is changed by the flow of the sealant material hardens in that state by cooling the tire 2. In this evaluation method, the tire 2 is cut in the direction perpendicular to the circumferential direction. The cured sealant layer 18 is unlikely to collapse even if it is cut. The thickness of the sealant layer 18 is measured using this cross section. Thereby, the thickness of the sealant layer 18 from the center part of the tire 2 to the shoulder part can be accurately measured.

  As for temperature T of a refrigerator which cools tire 2 at a process of above (2), -35 ° C or less is preferred. By setting the temperature T to −35 ° C. or less, the sealant layer 18 is sufficiently cured. The sealant layer 18 is not easily broken even when the tire 2 is cut. The sealant layer 18 is suppressed from being broken when the tire 2 is cut. In this method, the thickness of the sealant layer 18 from the center portion to the shoulder portion can be accurately measured. From this viewpoint, the temperature T is more preferably −37 ° C. or less. As for temperature T of a refrigerator, -45 ° C or more is preferred. By setting the temperature T to −45 ° C. or more, generation of brittle fracture (for example, a crack in the tread) of the rubber constituting the tire 2 is prevented. From this viewpoint, the temperature T is more preferably −42 ° C. or more.

  The time H for storing the tire 2 in the refrigerator is preferably 2 hours or more. The sealant layer 18 is sufficiently cured by setting the storage time H to 2 hours or more. The sealant layer 18 is not easily broken even when the tire 2 is cut. The sealant layer 18 is prevented from being broken when the tire 2 is cut. In this method, the thickness of the sealant layer 18 from the center portion to the shoulder portion can be accurately measured. From this viewpoint, the storage period H is more preferably 3 hours or more. From the viewpoint of efficiently performing the evaluation, the storage period H is preferably 5 hours or less.

  As for the space | interval I of the time from taking out the tire 2 from a refrigerator to the process of said (3) until it cut | disconnects the tire 2, 15 minutes or less are preferable. By setting the interval I to 15 minutes or less, the sealant layer 18 maintains a hardness that is less likely to collapse even when the tire 2 is cut. The sealant layer 18 is prevented from being broken when the tire 2 is cut. In this method, the thickness of the sealant layer 18 from the center portion to the shoulder portion can be accurately measured. In this respect, the interval I is more preferably within 10 minutes.

  The flowability of the sealant material is highly correlated with the viscosity of the sealant material. The sealant material exhibits higher flowability as the viscosity is lower. In addition, the ordinary sealant material has a lower viscosity as the temperature is higher. That is, the sealant material is more likely to flow as the temperature is higher.

  When the tire 2 travels, the temperature of the tire 2 rises. As the tire 2 travels, the temperature of the sealant layer 18 rises. As a result, the sealant material in the shoulder portion is more likely to flow toward the center portion. Even when the tire 2 becomes hot due to running, the sealant layer 18 is required to close the hole in the shoulder portion. It is important to accurately measure the thickness of the sealant layer 18 when the tire 2 becomes hot by running.

  In the step (1), the running speed V and the running time R when running the tire 2 with the running tester 22 are preferably determined so that the temperature of the sealant layer 18 is 80 ° C. or more and 95 ° C. or less. In the market where the tire 2 is used in a high temperature environment, the temperature of the tire 2 may rise from 80 ° C to 95 ° C. By accurately determining the traveling speed V and the traveling time R so that the temperature of the sealant layer 18 is 80 ° C. or more and 95 ° C. or less, the thickness of the sealant layer 18 when used in such a market can be accurately measured. Can.

  In addition to the traveling speed V and the traveling time R, there is a load F as a traveling condition when traveling the tire 2 by the traveling test device 22. Usually, in the market, since the passenger car tire 2 is used with the regular load F0 or less, the load F is set such that the ratio (F / F0) is 0.6 or more and 0.9 or less.

  Various methods for determining the traveling speed V and the traveling time R may be considered so that the temperature of the sealant layer 18 is 80 ° C. or more and 95 ° C. or less. In this embodiment, a button-type thermometer is disposed on the sealant layer 18. The thermometer is disposed radially inward of the shoulder portion where the temperature tends to rise. In this thermometer, the measured temperature is accumulated inside the thermometer. The traveling speed V and the traveling time R are variously changed to travel the tire 2. After traveling, by reading out the data of the temperature accumulated inside the thermometer, the traveling speed V and the traveling time R at which the temperature is 80 ° C. or more and 95 ° C. or less are confirmed.

  180 km / h or more is preferable and, as for the traveling speed V when making the tire 2 drive | work with the traveling test machine 22, 220 km / h or less is preferable. By setting the traveling speed V in this manner, the temperature of the sealant layer 18 can be 80 ° C. or more and 95 ° C. or less.

  30 minutes or more is preferable for traveling time R when making the tire 2 drive | work with the driving test machine 22. FIG. By setting the traveling time R to 30 minutes or more, the tire 2 is in an equilibrium state. Thereby, the temperature of the sealant layer 18 can be stabilized. The temperature of the sealant layer 18 can be stabilized at 80 ° C. or more and 95 ° C. or less.

  As described above, this test method is performed by the running test machine 22. The thickness of the sealant layer 18 can be evaluated with less effort in a short period of time as compared to the conventional method of mounting the tire 2 on a vehicle and actually traveling. Moreover, as described above, in this test method, by appropriately setting the traveling speed V and the traveling time R, the thickness of the sealant layer 18 when used in the market can be accurately measured.

  In the present specification, the normal rim means the rim defined in the standard on which the tire 2 is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims. The normal internal pressure as used herein means the internal pressure defined in the standard on which the tire 2 is based. The “maximum air pressure” in the JATMA standard, the “maximum value” published in the “TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES” in the TRA standard, and the “INFLATION PRESSURE” in the ETRTO standard are normal internal pressure. In the present specification, the normal load means the load defined in the standard on which the tire 2 is based. The "maximum load capacity" in the JATMA standard, the "maximum value" published in the "TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

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

[Tire preparation]
The tire whose size is "215/55 R17" was used for evaluation. As shown in FIG. 1, a sealant material was applied to the inside of the inner liner, radially inward of the tread. The axial width of the formed sealant layer was 182 mm, and the thickness was uniform 3 mm. The composition of the sealant material is generally based on butyl rubber and polybutene. A button-type thermometer was placed on the sealant layer near the radially inner side of the shoulder. The thermometer was taped on. This tire was incorporated into a regular rim (size: 17 × 17 J). The tire was filled with air, and the internal pressure was adjusted to 220 kPa.

Example 1
The thickness of the sealant layer was evaluated according to the steps (1) to (4) above. The above tire was run on a drum type running tester. The drum diameter of this evaluation machine is 1707 mm. The tire was loaded with 70% of the normal load (4.6 kN). Other driving conditions are as shown in Table 1. After running, the tires were stored in the refrigerator. The cooling temperature T and the storage time H at this time are as shown in Table 1. The tire was cut at two places after being taken out of the refrigerator. Thus, the tire was divided into two equal parts. The time interval I between removal from the refrigerator and disconnection was 15 minutes. For cutting, a wire cutter made by Shigaya Kogyo Co., Ltd. was used. From this cut surface, the thickness of the sealant layer was observed.

Comparative Example 1
Comparative Example 1 is the same as Example 1 except that the step (2) is not performed.

[Example 2-5]
Except for setting the traveling speed V and the cooling temperature T to the values shown in Table 1, Example 2-5 is the same as Example 1.

[Example 6]
Example 6 is the same as Example 1 except that the storage time H is set to the value shown in Table 2.

[Example 7]
Example 7 is the same as Example 1 except that the interval I is set to the value shown in Table 2.

[Sealant layer collapse]
The state of the sealant layer was visually confirmed in the cross section obtained by cutting the tire. The results are shown in Table 1-2. In the table, "A" represents that the sealant layer collapse has not occurred. "B" indicates that the sealant layer collapses, but the degree is small. "C" represents that the sealant layer is broken to such an extent that measurement of thickness is difficult. "A", "B" and "C" are preferred in this order.

[Tread crack]
With regard to the tire taken out of the refrigerator, the occurrence of cracks in the tread was visually confirmed. The results are shown in Table 1-2.

[Sealant layer temperature]
The temperature was measured with a thermometer attached to the sealant layer. The results are shown in Table 1-2. This is the temperature at which the temperature of the sealant layer is stable. The temperature of the sealant layer is preferably 80 ° C. or more and 95 ° C. or less.

[Sealant layer thickness]
Of the measured sealant layer thicknesses, values at points A and B are shown in Table 1-2. Here, the point A is a point on the sealant layer whose axial distance from the equatorial plane is 90 mm as shown in FIG. The point B is a point on the sealant layer whose axial distance from the equatorial plane is 80 mm. These are the averages of the values measured on the two cross sections produced when the tire was divided into two equal parts. According to the conventional analysis, in the market where the tire is used in a high temperature environment, the thickness of the sealant layer at point A is 0.0 mm-0.5 mm, and the thickness of the sealant layer at point B is 1 It is confirmed to be .0 mm-2.0 mm. In this evaluation, if the measurement results at points A and B fall within these ranges, it can be said that the flow of the sealant material on this market can be reproduced by this evaluation.

  As shown in Table 1-2, the evaluation method of the example is superior to the evaluation method of the comparative example. The superiority of the present invention is clear from the evaluation results.

  The evaluation method described above can be applied to the evaluation of various tires provided with a sealant layer.

Reference Signs List 2 tire 4 tread 6 side wall 8 bead 10 carcass 12 belt 14 band 16 inner liner 18 sealant layer 20 · · Tread surface 22 · · · running test machine 24 · · · drum 26 · · · running surface

Claims (7)

It is an evaluation method of a tire provided with a sealant layer in the inside, and
Storing the tires in a refrigerator,
A method of evaluating a tire, comprising the steps of: cutting the tire in a direction perpendicular to the circumferential direction; and measuring the thickness of the sealant layer in the cut section. Before the step of storing the tire in the refrigerator,
The evaluation method according to claim 1, further comprising: running the tire on a running test machine.   The evaluation method according to claim 2, wherein in the step of running the tire, the running speed and the running time of the tire are determined so that the temperature of the sealant layer is 80 ° C. or more and 95 ° C. or less.   The evaluation method according to claim 2 or 3, wherein the running speed of the tire in the step of running the tire is 180 km / h or more and 220 km / h or less, and the running time is 30 minutes or more.   The evaluation method according to any one of claims 1 to 4, wherein the temperature in the refrigerator in the step of storing the tire in the refrigerator is -45 ° C or more and -35 ° C or less.   The evaluation method according to any one of claims 1 to 5, wherein the storage time of the tire in the step of storing the tire in a refrigerator is 2 hours or more.   The evaluation method according to any one of claims 1 to 6, wherein a time interval between removing the tire from the refrigerator and cutting the tire is within 15 minutes.

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