JP2016049928A - Pneumatic tire and method for determining deterioration of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that enables a more accurate grasp of a progression condition of deterioration, and a method for determining the deterioration of the pneumatic tire.SOLUTION: In a pneumatic tire having a plurality of belt layers 7 embedded in a tread part 1, a determining deterioration member 8 made of an oxidation-reduction indication body changing a color tone by oxidation reaction is provided in at least a part in rubber between an outer surface of the tread part 1 and the outermost belt layer 7o, positioned on the outermost peripheral side, of the plurality of belt layers 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire assumed to be reused as a retreaded tire and a method for determining deterioration thereof, and more particularly, a pneumatic tire capable of grasping the progress of deterioration more accurately and a deterioration determination thereof. Regarding the method.

  Conventionally, a tread surface of a pneumatic tire whose remaining groove in the tread has reached the end of its life is cut and buffed, and a new tread is pasted on the base tire made of the remaining tire body to be reused as a retread tire. There is a case. In such a case, it is extremely important to grasp the progress of deterioration of the base tire.

  In Patent Document 1, paying attention to the fact that the air filled in the tire permeates the inner liner layer little by little over time is the main cause of deterioration of the pneumatic tire, and according to the air permeation amount It has been proposed that a redox indicator that changes color is attached to the inner peripheral surface of the tire, and a change in the color tone of the redox indicator is used as an indicator of deterioration of the pneumatic tire.

  However, this method has a problem that the degree of deterioration of the tire component itself cannot be determined directly and accurately, and the degree of deterioration can only be grasped indirectly. In particular, since the oxidation-reduction indicator is attached to the tire inner peripheral surface and is always exposed to the air filled in the tire, the deterioration degree tends to be judged to be worse than actual, and accurate judgment is difficult. There is a problem.

JP 2010-179824 A

  An object of the present invention is to provide a pneumatic tire and a method for determining deterioration thereof, which can more accurately grasp the progress of deterioration in a pneumatic tire assumed to be reused as a retreaded tire. .

  In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which a plurality of belt layers are embedded in a tread portion, and the outermost belt layer located on the outermost peripheral side of the plurality of belt layers. A deterioration determining member including a redox indicator whose color tone changes due to an oxidation reaction is embedded in rubber between the outer surface of the tread portion and the outer surface of the tread portion.

  In the present invention, since the deterioration determining member is provided between the outermost belt layer and the outer surface of the tread portion, the deterioration degree of the portion close to the belt layer remaining as the base tire after cutting and buffing the tread portion is accurate. It becomes possible to judge well. In addition, since the deterioration determining member is embedded in this part, the deterioration determining member is exposed during the tread portion cutting and buffing operations in the retreaded tire manufacturing process, and the deterioration can be easily determined by visual inspection. It becomes possible.

  In the present invention, it is preferable that the deterioration determining member is disposed in a region of 1/4 of the tread width from the outer end in the tire width direction of the tread portion. Thereby, it is possible to reliably determine the degree of deterioration in the vicinity of the belt edge where the temperature rise in the tire is large and the amount of oxidation deterioration tends to be large. The outer end in the tire width direction is a tire on a contact surface with a flat surface when a normal load is applied by placing the tire perpendicular to the plane in a state where the tire is assembled on a normal rim and filled with a normal internal pressure. It is an end in the width direction. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is for JATA and the table “TIRE ROAD LIMITS AT VARIOUS” is for TRA. In the case of ETRTO, the maximum value described in “COLD INFORATION PRESSURES” is “INFLATION PRESSURE”. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. In the case of ETRTO, the maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY”.

  In the present invention, it is preferable that the deterioration determining member is disposed in a region within 10 mm from the outermost belt layer to the outer side in the tire radial direction. Thereby, it is possible to reliably determine the degree of deterioration in the vicinity of the belt for which the degree of deterioration is actually to be determined.

  In the present invention, the deterioration determining member is preferably composed of a redox indicator and a coating layer covering the redox indicator, and the coating layer is preferably composed of rubber or a thermoplastic elastomer having lower air permeability than the adjacent rubber. As a result, the amount of air that passes through the oxidation-reduction indicator can be adjusted to slow down the discoloration rate of the deterioration determining member, so that discoloration during manufacturing and storage before using the tire can be suppressed, or depending on the tire It is possible to set a threshold.

  At this time, it is also possible to use a specification in which a plurality of deterioration determining members having different discoloration speeds are used in combination by changing the thickness of the coating layer. This makes it possible to determine the degree of deterioration in stages.

  In the present invention, the deterioration determination member may be configured to include two or more types of redox indicators that are different in color after discoloration. This makes it possible to determine the degree of deterioration in stages.

  In the above-described method for determining the deterioration of a pneumatic tire, the degree of deterioration of the tire can be easily determined by grinding and removing the tread portion, exposing the deterioration determination member, and observing the change in the color tone.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is explanatory drawing which expands and shows the deterioration determination member of FIG. It is explanatory drawing which shows typically an example of the deterioration indicator of this invention. It is explanatory drawing which shows another example of the deterioration indicator of this invention typically. It is explanatory drawing which shows another example of the deterioration indicator of this invention typically. FIG. 3 is a meridian cross-sectional view showing a state where the tread portion of the pneumatic tire of the present invention is removed.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  In FIG. 1, the symbol CL represents the tire equator. The pneumatic tire T of the present invention includes a tread portion 1, a sidewall portion 2, and a bead portion 3. A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. Further, a bead filler 6 is disposed on the outer periphery of the bead core 5, and the folded end portion of the carcass layer 4 terminates in the middle of the bead filler 6. On the other hand, a plurality of layers (four layers in FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  In the pneumatic tire of the present invention, the rubber layer on the outer side in the tire radial direction from the outermost belt layer 7o located on the outermost peripheral side among the plurality of belt layers 7, that is, the outermost belt layer 7o and the tread portion 1 A deterioration determining member 8 is embedded in rubber between the outer surface. For example, as shown in an enlarged view in FIG. 2, the deterioration determining member 8 includes a redox indicator 9 whose color tone changes due to an oxidation reaction, and a coating layer 10 that covers the redox indicator 9. In the example of FIG. 1, the deterioration determining members 8 are provided at three locations in the tire width direction (below the land portion on the tire equator CL and below the outermost land portions in the left and right tire width directions).

  The oxidation-reduction indicator 9 is, for example, rubber containing a color indicator (oxidation-reduction indicator) having a different color tone between the oxidant and the reductant, paper, cloth, fiber, or the like impregnated with the oxidation-reduction indicator. When a solid is used as the redox indicator, the redox indicator itself may be used directly as the redox indicator 9. Since the performance of the tire itself is affected when the deterioration indicator member 8 is significantly different in nature from the surrounding rubber, it is preferable to use a rubber containing a redox indicator as the redox indicator 9. At this time, the rubber containing the redox indicator is preferably a white rubber so that the change in color tone of the redox indicator becomes clear. In this case, when the oxidative deterioration progresses, the white deterioration indicating member 8 (redox indicator 9) develops the color of the oxidant of the redox indicator.

  The type of oxidation-reduction indicator is not particularly limited, but it is preferable to use a material having excellent visibility because the color tone of the surrounding rubber (mainly black) and the oxidation-reduction indicator after discoloration (color tone of the oxidant) are different. For example, indigo carmine (reduced body color: colorless / oxidized body color: blue), indigo tetrasulfonic acid (reduced body color: colorless / oxidized body color: blue), methylene blue (reduced body color: colorless / oxidized body color: blue) Diphenylamine (reduced body color: colorless / oxidized body color: violet), diphenylbenzidine (reduced body color: colorless / oxidized body color: violet), diphenylamine sulfonic acid (reduced body color: colorless / oxidized body color: magenta), Examples include phenosafranine (reduced body color: colorless / oxidized body color: red). The redox indicator is used for the redox indicator 9 in a state where a corresponding reducing agent is allowed to act to make a colorless reductant as required.

  The covering layer 10 is made of, for example, rubber or a thermoplastic elastomer. The coating layer 10 is not necessarily provided, but can be used for the purpose of delaying the color change progress rate of the oxidation-reduction indicator 9 as described later.

  In the pneumatic tire, since the air filled in the tire permeates through the pneumatic tire itself with time, particularly the rubber or the like constituting the pneumatic tire is gradually oxidized and deteriorated, but the deterioration determining member 8 of the present invention. Is embedded in the rubber between the outermost belt layer 7o and the outer surface of the tread portion 1, so that the air passing through the pneumatic tire is received to the same extent as the surrounding rubber as described above. Therefore, the discoloration of the deterioration determining member 8 directly reflects the degree of deterioration of the surrounding rubber. Therefore, in the present invention, it is possible to determine the degree of deterioration of the pneumatic tire more accurately and directly than in the case where the deterioration determining member 8 is disposed on the tire inner peripheral surface as in the prior art. Further, the rubber between the outermost belt layer 7o in which the deterioration determining member 8 is embedded and the outer surface of the tread portion 1 is removed during the tread portion cutting and buffing operations in the retread tire manufacturing process. The deterioration determining member 8 is exposed during manufacturing, and it is possible to easily perform deterioration determination by visually observing this.

  The arrangement location of the deterioration determination member 8 is not particularly limited, and may be provided at least at a part between the outermost belt layer 7 o and the outer surface of the tread portion 1. For example, regarding the arrangement in the tire width direction, it may be arranged in only one place in the width direction, or may be arranged in a plurality of places as shown in FIG. Furthermore, you may make it provide in the whole surface of a tire width direction. About arrangement | positioning of a tire circumferential direction, you may arrange | position cyclically | annularly over a tire circumferential direction perimeter, arrange | position intermittently, or provide only in the predetermined | prescribed location of the circumferential direction. However, the deterioration determining member 8 tends to be different in nature from the surrounding rubber, and as the amount of embedment increases, the performance of the tire itself is affected. Therefore, the arrangement in the tire width direction is partially corresponding to the land portion, for example, It is good to have about 1 to 5 places. Regarding the arrangement in the circumferential direction, it may be provided locally as in the arrangement in the width direction, but in consideration of the uniformity over the entire circumference of the tire, it may be arranged intermittently at equal intervals or over the entire circumference. May be provided continuously. In the case where the deterioration determining member 8 is locally disposed at a predetermined position in the width direction and / or the circumferential direction, the position of the deterioration determining member 8 can be easily set during cutting and buffing of the tread portion in the retread tire manufacturing process. As can be confirmed, a mark indicating the embedment location of the deterioration determination member 8 may be attached to the portion remaining as the base tire.

  Regarding the disposition of the deterioration determining member 8 in the width direction, the deterioration determining member 8 further has a tread width TDW (distance between the tire width direction outer ends E on both sides in the tire width direction) from the tire width direction outer end E of the tread portion 1. Preferably, it is arranged within the region A of / 4. This region A includes the vicinity of the belt edge where the temperature rise and the amount of oxidative degradation in the tire tend to be large, and is suitable for judging the degree of degradation and the durability of the portion remaining as a base tire, and more effectively degrading. Judgment can be made. In addition, since asymmetrical deterioration (one-side deterioration) may occur in the tire width direction, it is more effective to dispose the deterioration determination members 8 in the regions A on both sides in the tire width direction.

  Among the outermost belt layer 7o and the outer surface of the tread portion 1, the deterioration determining member 8 is particularly preferably disposed in the region B within 10 mm on the outer side in the tire radial direction from the outermost belt layer 7o. By disposing the deterioration determining member 8 in such a region B, it is possible to reliably determine the degree of deterioration in the vicinity of the portion close to the belt layer 7, that is, the portion actually remaining as the base tire. In addition, when the width | variety of the outermost belt layer 7o is the smallest like the pneumatic tire illustrated in FIG.

  When the deterioration determining member 8 has the covering layer 10 as shown in FIG. 2, the air permeability of the rubber or the thermoplastic elastomer constituting the covering layer 10 is lower than the air permeability of the rubber adjacent to the covering layer 10 (surrounding rubber). Then, the amount of air reaching the redox indicator 9 that actually changes color due to oxidation can be reduced. Depending on the type of oxidation-reduction indicator 9 and the structure of the tire (particularly the material and thickness of the inner liner layer), discoloration of the oxidation-reduction indicator 9 is completed faster than the progress of deterioration of the pneumatic tire. Since there is a possibility, by adjusting the amount of air reaching the redox indicator 9 by the coating layer 10 as described above, the rate of color change of the redox indicator 9 can be slowed down and appropriate deterioration determination can be made. Can be. In particular, it is possible to prevent the oxidation-reduction indicator 9 from being oxidized first during the production of the pneumatic tire (particularly in the vulcanization process), and the deterioration degree of the pneumatic tire cannot be determined appropriately. Moreover, since the progress speed of the discoloration of the oxidation-reduction indicator 9 can be appropriately delayed depending on the material and thickness of the coating layer 10, it is possible to easily set a threshold value according to the pneumatic tire.

  By using a plurality of deterioration determining members 8 having different discoloration speeds in combination, it is possible to determine the degree of deterioration stepwise. For example, as shown in FIG. 3, three deterioration determination members 8a, 8b, and 8c are provided at one place, the color change speed of the deterioration determination member 8a is the fastest, and the color change speed of the deterioration determination member 8b is the second fastest, When the discoloration speed of the deterioration determining member 8c is the slowest, the discoloration is completed in the order of the deterioration determining member 8a, the deterioration determining member 8b, and the deterioration determining member 8c depending on the degree of oxidation (deterioration degree) (deterioration in FIG. 3). See levels 1-3). It is possible to determine the degree of deterioration step by step by checking the presence / absence of discoloration of each deterioration determining member 8a, 8b, 8c.

  When the discoloration speed is varied in this way, for example, as shown in FIG. 4, the discoloration speed is varied by changing the types of oxidation-reduction indicators 9a, 9b, 9c constituting the deterioration determination members 8a, 8b, 8c. Can be made. In the example of FIG. 4, each deterioration determination member 8a, 8b, 8c is composed of oxidation-reduction indicators 9a, 9b, 9c and coating layers 10a, 10b, 10c, respectively, but each deterioration determination member 8a, 8b and 8c may be composed of only the oxidation-reduction indicators 9a, 9b, and 9c, and the entire deterioration determination members 8a, 8b, and 8c may be covered with one coating layer 10.

  Alternatively, as shown in FIG. 5, the types of the oxidation-reduction indicators 9a, 9b, 9c constituting the deterioration determination members 8a, 8b, 8c are made common and the thicknesses of the coating layers 10a, 10b, 10c are made different. You may vary the discoloration speed. That is, in the example of FIG. 5, the coating layer 10a of the degradation determination member 8a is the thinnest, the coating layer 10b of the degradation determination member 8b is the second thinnest, and the coating layer 10c of the degradation determination member 8c is the thickest. As the coating layer 10 is thicker, air is less likely to reach the oxidation-reduction indicator 9, and as in the case of FIG. 3, the discoloration is completed in the order of the deterioration determination member 8a, the deterioration determination member 8b, and the deterioration determination member 8c. become.

  At this time, if the redox indicator 9 has the same color after discoloration (oxidant color), as shown in FIG. 3, the degree of deterioration is determined based on the size of the discolored portion. If a plurality of types of redox indicators 9 having different colors (colors of oxidized products) after the color change are used, the degree of deterioration can be more clearly determined step by step based on the difference in colors. That is, for example, in the example of FIG. 3 described above, the color of the redox indicator 9a is “blue”, the color of the redox indicator 9b is “red”, and the redox indicator 9c is the oxidized color of the redox indicator 9c. If the color is “violet”, the degradation level when only “blue” appears, the degradation level when “red” also appears, and further the degradation level when “violet” appears. Can be done clearly.

  When determining the deterioration of the pneumatic tire of the present invention, first, the rubber on the outer side in the tire radial direction from the outermost belt layer 7o of the tread portion 1 is ground and removed. Thereby, as illustrated in FIG. 4, the deterioration determining member 8 is exposed to the outside. Then, the degree of deterioration of the tire is determined by looking at the color of the exposed deterioration determining member 8. Grinding the tread part 1 is an essential process when reusing used tires as retreaded tires, so it is easy to determine the degree of deterioration during the retreaded tire manufacturing process and reliably select reusable base tires. It becomes possible to do.

  A deterioration determination member including deterioration determination members A to C shown in Table 1 and capable of determining the deterioration level in three stages (deterioration levels 1 to 3) was produced. Specifically, the deterioration level 1 is when the deterioration determining member A changes to red, the deterioration level 2 when the deterioration determining member B changes to violet, and the deterioration level 3 when the deterioration determining member C changes to blue. did. It means that the deterioration is progressing from the deterioration level 1 to the deterioration level 3.

  A tire A having a tire size of 275 / 70R22.5, having the cross-sectional structure shown in FIG. 1, including the above-described deterioration determining member, and having a different inner liner layer thickness (inner liner thickness: 1. 5 mm), tire B (inner liner thickness: 2.0 mm), and tire C (inner liner thickness: 2.5 mm), respectively. At this time, the arrangement of the deterioration determination member and the presence / absence of the coating layer of the deterioration determination member were changed as shown in Table 2 to obtain Comparative Example 1 and Examples 1-2.

  Each of these tires A to C is assembled to a wheel having a rim size of 22.5 × 7.50, filled with an air pressure of 900 kPa, mounted on a truck, traveled 200,000 km, and the tread portion is completely worn out. A buff treatment was performed, the deterioration determining member was visually confirmed, and the deterioration level of each tire was determined. The determination results are also shown in Table 2.

  On the other hand, belt rubber was extracted from each tire that was completely worn, and the elongation at break was measured according to JIS K6251 to obtain an index value with the value of the elongation at break of the belt rubber as new as 100. This index value is shown in Table 2 as a deterioration index indicating the actual deterioration degree of the tires A to C.

  As is clear from Table 2, Examples 1 and 2 were able to perform a deterioration determination that was highly correlated with the actual deterioration degree (deterioration index) with respect to Comparative Example 1. Specifically, in Comparative Example 1, since the deterioration determination member is disposed on the tire inner peripheral surface, the deterioration determination member is further oxidized, and the determination results of tires A to C are all “deterioration level 3”. It was. On the other hand, in Example 1, since the deterioration determination member is embedded in the tire, the air that passes through the tire is received to the same extent as the surrounding rubber, and the tire A corresponds to the actual deterioration degree (deterioration index). The determination result of “deterioration level 3”, the determination result of tire B was “deterioration level 2”, and the determination result of tire C was “deterioration level 1”. In the second embodiment in which the deterioration determining member is embedded in the tire but the deterioration determining member does not have a coating layer, the tires A and B are more than the tire C in correspondence with the actual deterioration degree (deterioration index). However, since the discoloration of the deterioration determination member progressed quickly, the determination result of the tire A and the determination result of the tire B became the same.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 7o Outermost belt layer 8 Deterioration judgment member 9 Redox indicator 10 Covering layer CL Tire equator

Claims (7)

In a pneumatic tire in which a plurality of belt layers are embedded in the tread portion,
A deterioration determining member including a redox indicator whose color tone is changed by an oxidation reaction in a rubber between an outermost belt layer located on the outermost peripheral side of the plurality of belt layers and an outer surface of the tread portion. A pneumatic tire characterized by being buried.   2. The pneumatic tire according to claim 1, wherein the deterioration determining member is disposed in a region of ¼ of the tread width from an outer end in a tire width direction of the tread portion.   3. The pneumatic tire according to claim 1, wherein the deterioration determining member is disposed in a region within 10 mm from the outermost belt layer to the outer side in the tire radial direction.   The deterioration determining member includes the oxidation-reduction indicator and a coating layer covering the oxidation-reduction indicator, and the coating layer is made of rubber or a thermoplastic elastomer having a lower air permeability than the adjacent rubber. The pneumatic tire according to any one of claims 1 to 3.   The pneumatic tire according to claim 4, wherein a plurality of the deterioration determining members having different discoloration speeds by changing the thickness of the coating layer are used in combination.   The pneumatic tire according to any one of claims 1 to 5, wherein the deterioration determining member includes two or more types of redox indicators that are different in color after discoloration.   The pneumatic tire according to claim 1, wherein the tread portion of the pneumatic tire is ground and removed, the deterioration determining member is exposed, and the deterioration degree of the tire is determined by observing a change in color tone. Deterioration judgment method for entering tires.

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