JP2013023062A - Tire remoldability determination method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine tire remoldability at an early stage and clearly by numerical evaluation.SOLUTION: A tire deformation promotion step is performed of exposing a tire filled with high pressure air, prepared by assembling a normal rim into a heavy duty tire and by filling the tire with air to a specified internal pressure higher than a normal internal pressure, in the atmosphere at a high temperature of 60-80C° during an exposure period in the range of 7-14 days. A tire axial direction distance L1 between bead toes and a radius R1 of the bead toe are measured in a non-rim-assembly state of the tire before the tire deformation promotion step. Then, the tire axial direction distance L2 between bead toes and the radius R2 of the bead toe are measured in a non-rim-assembly state of the tire after the tire deformation promotion step. The tire remoldability is determined based on a variation ΔL={(L2-L1)/L1} of the distances L1 and L2 and a variation ΔR={(R2-R1)/R1} of the radiuses R1 and R2.

Description

  The present invention relates to a tire retreading determination method that can determine tire retreading ability as to whether tire retreading is possible when a heavy-duty tire has finished its wear life, for example, at the time of tire formation.

  In heavy-duty tires for trucks and buses, it is widely practiced to recycle used tire tread rubber that has reached the end of its wear life and reuse it as retreaded tires.

  As this tire retreading method, a so-called precure method is widely adopted. In the above system, a tread affixing base is prepared by attaching a vulcanized precure tread rubber body via an unvulcanized cushion rubber to a buffing surface of a base tire that has been buffed by scraping off the tread rubber of a used tire. Form a tire. Then, after the tread-attached base tire is assembled into a rim and filled with an internal pressure, a retread tire in which the base tire and the precured tread rubber body are integrated by, for example, heat treatment in an oven pot (steam pot, etc.) Is forming.

  On the other hand, since heavy load tires are operated under severe conditions of high internal pressure and high load, a large tension force F acts on the carcass ply a as shown in FIG. At this time, both end portions of the carcass ply a are folded and locked around the bead core b. Therefore, a strong rotational moment M is generated around the bead core b by the tension force F, and the bead core b is deformed so as to rotate around the core center. Also, the bead portion c is deformed in such a direction that the bead toe BT is lifted from the rim sheet J1 by being dragged.

 The bead deformation becomes larger as the tire usage period increases and becomes permanent deformation, and does not return to its original shape after being removed from the rim. For this reason, in a tire with a particularly large bead deformation, when the tire is rehabilitated by the precure method, there is a problem that the air filled during rim assembling leaks from the bead toe BT side, making the rim assembling difficult and the tire rehabilitation impossible. Arise.

  Therefore, when designing and developing a tire, it is important to determine whether the developed tire is a tire that can be rehabilitated, that is, whether the tire is excellent in tire rehabilitation. However, in the past, the developed tires were actually driven to near the wear life under actual usage conditions and then re-rim assembled to evaluate tire retreading. Therefore, for example, a long development period of 1 to 2 years is required.

  In order to shorten the tire development period, the following Patent Document 1 proposes performing a deterioration promoting process under a predetermined condition prior to the durability test in the tire durability test method. However, the conventional process for promoting deterioration deteriorates the strength of rubber, the adhesiveness between rubber and cord, and the adhesiveness between rubbers, and cannot be used for judging tire retreading. Furthermore, when the rim is actually assembled and the tire retreading property is judged based on the air-in property at that time, the rim assembling work is complicated and affected by the work variation, so it cannot be clearly determined by quantification. .

JP 2006-337100 A

  Therefore, the present invention basically promotes tire permanent deformation under a predetermined condition, and determines tire rehabilitation based on the amount of change in the distance between the bead toes and the amount of change in the radius of the bead toe before and after the permanent deformation. Therefore, it is an object of the present invention to provide a tire retreading determination method that can determine tire retreading property early and clearly in numerical form.

In order to solve the above problem, the invention of claim 1 of the present application is a tire retreading determination method for determining tire retreading in a heavy duty tire,
A first measurement for measuring a tire axial distance L1 between bead toes of bead portions on both sides facing each other via a tire equatorial plane and a bead toe radius R1 centering on the tire axis with respect to a heavy load tire before assembling the rim. Process,
A high-pressure filled tire in which a heavy load tire is assembled on a regular rim and filled with a specified internal pressure higher than the normal internal pressure is left in a high temperature atmosphere at a temperature of 60 to 80 ° C. for a period of 7 to 14 days. Tire deformation promotion process,
A second measuring step of measuring a tire axial distance L2 between bead toes and a bead toe radius R2 with respect to the heavy duty tire removed from the regular rim after the tire deformation promoting step;
In addition, the change amounts ΔL = {(L2−L1) / L1} of the tire axial distances L1 and L2 between the bead toes and the change amounts ΔR = {(R2−R1) / R1} of the radiuses R1 and R2 of the bead toes. It is characterized by comprising a determination step for determining tire retreading.

  According to a second aspect of the present invention, the specified internal pressure is in a range of 1.1 to 1.3 times the normal internal pressure.

According to a third aspect of the present invention, the determining step determines tire rehabilitation based on an index value K defined by the following equation (1).
K = ΔR + a × ΔL ---- (1)
(A is a coefficient smaller than 1.0)

  According to a fourth aspect of the present invention, the determination step determines that the tire has tire retreading properties when the index value K is equal to or less than a preset reference value.

  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 means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Means “INFLATION PRESSURE”, but in the case of passenger car tires, it is 200 kPa.

  As described above, the present invention relates to a tire deformation acceleration process in which a high-pressure filled tire filled with a specified internal pressure higher than the normal internal pressure is left in a high temperature atmosphere at a temperature of 60 to 80 ° C. for a leaving period of 7 to 14 days. I do. By this process, tire deformation can be promoted, and the permanently deformed state of the tire when used near the wear life can be reproduced.

  Then, a change amount ΔL of the distance between the bead toes of the tire due to the permanent deformation and a change amount ΔR of the radius of the bead toe are obtained, and based on this, the tire retreading property is determined.

  In the permanent deformation, the hindrance to tire regeneration is mainly a deformation in which the bead toe is lifted from the rim seat due to the rotational moment around the bead core. As the amount of deformation increases, the air filled during rim assembly leaks from the bead toe side, making rim assembly more difficult, and tire regeneration cannot be performed. Further, the air leakage from the bead toe side is related to both the change amount ΔL of the distance between the bead toes and the change amount ΔR of the radius of the bead toe. By using these change amounts ΔL and ΔR, the air leakage Therefore, the tire rehabilitation property can be numerically determined.

It is sectional drawing which shows an example of the tire for heavy loads determined by the tire retreading determination method of this invention. It is sectional drawing which expands and shows a bead part. It is the graph which plotted the evaluation by change amount (DELTA) R, (DELTA) L on a horizontal axis, and evaluated by the actual re-rim assembly on the vertical axis. It is sectional drawing which shows the deformation | transformation of the bead part in connection with tire retreading.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a cross-sectional view showing an example of a heavy load tire whose tire retreadability is determined by the tire retreading determination method of the present invention.

  In the figure, as is well known, a heavy load tire 1 includes a tread portion 2 having a tire tread surface 2S, a pair of sidewall portions 3 extending from both ends in the tire axial direction toward the inside in the tire radial direction, and And a bead portion 4 located at the radially inner end. The heavy load tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the radial direction and inside the tread portion 2. Reinforced by the containing cord reinforcement layer.

  The carcass 6 is composed of one or more radial structures in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. Both ends of the carcass ply 6 </ b> A are folded back from the inner side to the outer side in the tire axial direction around the bead core 5, thereby being locked to the bead core 5.

  As shown in an enlarged view in FIG. 2, the bead core 5 has a ring shape in which, for example, steel bead wires 5w are wound in multiple rows and stages, and those having a hexagonal cross section are widely employed. In this example, the bead core 5 has a flat hexagonal cross section in which the radially inner circumferential surface SL is inclined substantially parallel to the rim sheet J1 of the regular rim J, thereby providing a fitting force between the bead portion 4 and the rim sheet J1. Increased over a wide range. In this example, the regular rim J is a 15 ° deep bottom rim for a tubeless tire, and the radially inner peripheral surface SL and the outer peripheral surface SU of the bead core 5 are both approximately 15 ° with respect to the tire axial line. Is inclined at an angle θ1.

  Further, the bead portion 4 of the present example has a bead bottom surface 4a substantially linear, and is inclined at an angle θ2 of, for example, about 20 to 30 ° with respect to the tire axial line. The angle θ2 is larger than the angle θ1 of the rim seat surface J1, and when the rim is assembled, the rubber between the bead core 5 and the bead bottom surface 4a is strongly compressed, thereby increasing the fitting pressure with the rim seat surface J1. sell.

  The bead bottom surface 4a may be formed of two surfaces having different angles θ2 as required. The outer end of the bead bottom surface 4a in the tire axial direction is connected to the bead outer surface 4b via the arc-shaped bead heel portion BH, and the inner end of the bead bottom surface 4a in the tire axial direction is connected to the bead outer surface 4c via the bead toe BT. It is a series.

  Reference numeral 8 in the figure denotes a bead apex rubber that rises from the bead core 5, and reference numeral 9 denotes a bead reinforcing cord layer disposed along the carcass 6, which reinforces the bead portion 4 to bead durability and control. Improves medium stability. The belt layer 7 is composed of two or more belt plies 7A to 7D in this example in which high strength belt cords such as steel cords are arranged at an angle of, for example, 10 to 75 ° with respect to the tire circumferential direction. The tread portion 2 is reinforced.

  Next, a tire regeneration determination method for determining tire regeneration in the heavy load tire 1 will be described below.

This tire retreading judgment method is
(A) For the heavy load tire 1 before assembling the rim, a bead toe BT centered on the tire axial center distance L1 between the bead toes BT of the bead parts 4 and 4 on both sides facing the tire equatorial plane Co, and the tire axial center. A first measuring step for measuring a radius R1 of
(A) a tire deformation promoting step for promoting tire deformation of the heavy load tire 1;
(C) a second measuring step of measuring the tire axial distance L2 between the bead toes BT and the radius R2 of the bead toes BT with respect to the heavy load tire 1 after the tire deformation promoting step;
(D) a determination step of determining tire retreading based on the change amount ΔL of the tire axial distances L1 and L2 and the change amount ΔR of the radii R1 and R2.
With

  In the first measurement step, the distance L1 between the bead toes BT and the radius R1 of the bead toes BT before the tire is deformed with time are measured in a non-rim assembled state. At this time, when the tire is measured in a horizontally placed state (with the tire axial center facing up and down), due to the weight of the tire, the portion from the sidewall portion 3 to the bead portion 4 is deformed, and an accurate measurement value is obtained. I can't. Therefore, in the first measurement step, measurement is performed in a vertically placed state in which the tire axis is oriented horizontally. The measurement is preferably performed at a plurality of positions in the circumferential direction of the tire, and the distance L1 between the bead toe BT and the radius R1 of the bead toe BT are obtained from the average value.

  Next, in the tire deformation promoting step, the high-pressure filled tire in which the heavy load tire 1 is assembled to the regular rim J and filled with a specified internal pressure higher than the normal internal pressure is placed in a high temperature atmosphere at a temperature of 60 to 80 ° C. Leave for a period of 7 to 14 days. This promotes tire deformation and reproduces the tire's permanent deformation state when used near the wear life.

  As described above, the tire deformation in the permanent deformation is hindered mainly by the deformation in the direction in which the bead toe BT is lifted from the rim sheet J1 due to the rotational moment around the bead core. Therefore, deformation of the bead toe BT is promoted by applying a large rotational moment using a specified internal pressure higher than the normal internal pressure. The specified internal pressure is preferably in the range of 1.1 to 1.3 times the normal internal pressure. When the specified internal pressure is 1.1 times or less, acceleration of deformation cannot be achieved. On the other hand, if it exceeds 1.3 times, the rotational moment becomes excessive, the cross-sectional shape of the bead core 5 is deformed, and the bead wire arrangement is disturbed to cause the core collapse. Will occur, making it impossible to reproduce the permanently deformed state of the tire. From such a viewpoint, the upper limit of the prescribed internal pressure is more preferably 1.2 times or less.

  Moreover, when the said high temperature atmosphere is less than 60 degreeC, it does not lead to permanent deformation, but when it removes from a rim | rim after a tire deformation | transformation acceleration | stimulation process, the tendency for a deformation | transformation to recover is invited. On the other hand, when the temperature exceeds 80 ° C., the side wall rubber and bead rubber are deteriorated by heat and hardened, and when the tire is not removed from the rim, the bead toe BT is notched or deformed so that proper evaluation cannot be performed. It becomes a trend.

  Further, even when the leaving period is less than 7 days, the deformation is not promoted sufficiently and permanent deformation is not caused, and when the tire is removed from the rim after the tire deformation promoting step, the deformation tends to be recovered. On the contrary, even if the leaving period exceeds 14 days, no significant progress of permanent deformation is observed, resulting in a waste of time and cost. In particular, as a result of experiments by the present inventor, it has been found that it is preferable to set the standing period longer within the above range because the tire is less likely to be deformed as the tire has a smaller flatness ratio. Therefore, in a tire having a flatness ratio of 90% or more, the leaving period is 7 to 14 days (more preferably 7 days), and in a tire having a flatness ratio of 80% or more and less than 90%, the leaving period is 10 to 14 days (more preferably). 10 days), and for a tire with a flatness ratio of less than 80%, the leaving period is preferably 14 days.

  In the second measurement step, the distance L2 between the bead toes and the radius R2 of the bead toe are measured for the heavy load tire 1 removed from the regular rim J after the tire deformation promoting step. In the second measurement step, as in the first measurement step, measurement is performed in a vertically placed state in which the tire axial center is oriented horizontally in order to avoid adverse effects due to the weight of the tire.

  Next, in the determination step, the change amounts ΔL = {(L2−L1) / L1} of the tire axial distances L1, L2 between the bead toes BT and the change amounts ΔR = {(of the radii R1, R2 of the bead toes BT. Based on R2-R1) / R1}, the tire retreading property is determined.

  Here, since the air to be filled at the time of assembling the rim is leaked from the bead toe BT side and the assembling of the rim becomes difficult, the tire cannot be rehabilitated. Therefore, in the present invention, the tire rehabilitation is based on the air leakage. To be judged. The air leakage is related to both the bead toe radius change ΔR and the bead toe distance change ΔL. That is, the smaller the amount of change ΔR, the smaller the rise of the bead toe BT from the rim sheet J1 and the better the air leakage, but the smaller the amount of change ΔL is, the smaller the protrusion of the sidewall portion 3 outward in the tire axial direction. In this case, the air leakage is reduced.

Therefore, in the present invention, the air leakage (tire regeneration) is determined on the basis of the two variations ΔR and ΔL. Of the amount of change ΔR, ΔL, the amount of change ΔR has a greater influence on air leakage (tire regeneration). Therefore, it is preferable to determine the tire retreading property based on the index value K defined by the following equation (1). Note that the symbol a is a coefficient smaller than 1.0 and is more preferably in the range of 0.3 ± 0.1.
K = ΔR + a × ΔL ---- (1)

  In this determination step, when the index value K is equal to or less than a preset reference value, it can be determined that the tire has tire retreading properties.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

(1)
In order to confirm the effect of the present invention, a heavy-duty tire (tire size 11R22.5) having the internal structure shown in FIG. 1 was prototyped, and as shown in Table 1, the conditions of the specified internal pressure, high-temperature atmosphere, and leaving period were changed. The tire deformation promoting step is performed, and the change amounts ΔL = {(L2−L1) / L1} of the tire axial distances L1 and L2 between the bead toes, and the change amounts ΔR = {(R2−R1) of the bead toe radii R1 and R2. / R1} was measured.

  In place of the tire deformation promotion step, the heavy duty tire is mounted on a test vehicle (domestic 10 ton truck 2-D4 vehicle) at a state close to actual use conditions, for example, at a normal internal pressure (700 kPa), and is in a half-loading state. The actual vehicle was run until it reached the wear life (loaded in front of the loading platform), and the changes ΔL ′ and ΔR ′ at that time were measured. The amount of change ΔL ′ due to actual vehicle travel was 0.071, and ΔR ′ was 0.0072.

  As shown in Table 1, when the tire deformation promotion process is performed under the conditions where the specified internal pressure is 1.1 to 1.3 times the normal internal pressure, the high temperature atmosphere is 60 to 80 ° C., and the leaving period is 7 to 14 days, It can be confirmed that the permanent deformation state of the tire when the vehicle is actually driven can be almost reproduced.

In addition, the tires of Comparative Examples A1 to A7 and Examples A1 to A5 that were subjected to the tire deformation promotion step were actually re-assembled, and the air leakage from the bead toe BT side (air-in property) was Were evaluated in four stages (◎, ○, Δ, ×) and compared with the evaluation using the change amounts ΔR and ΔL. The results are shown in Table 1. The evaluation based on the change amounts ΔR and ΔL was performed using an index value K (coefficient a = 0.3) defined by the following equation (1). In the evaluation by the actual re-rim assembly, the filling internal pressure at the time of the re-rim assembly is set to 800 kPa.
◎ --- Air enters without leaking air.
○ --- Air moves when the tire is moved vertically.
△ --- Air moves when the tire is moved vertically and horizontally.
× --- Air does not enter.
K = ΔR + a × ΔL ---- (1)

(2)
Next, a heavy-duty tire (tire size 11R22.5) having the internal structure shown in FIG. 1 is prototyped based on the specifications shown in Table 2, and the tire retreading property of each sample tire is evaluated using the variations ΔR and ΔL. did. The tire deformation promoting step was performed under the conditions where the specified internal pressure was 1.1 times the normal internal pressure (700 kPa), the high temperature atmosphere was at 70 ° C., and the standing period was 7 days.

  Then, the tire was actually re-assembled, the air-in property at that time was evaluated in the above four steps (◎, ○, Δ, ×), and the index value K (coefficient a = 0.3).

  FIG. 3 is a graph in which the index value K is plotted in Tables 1 and 2 with the horizontal axis representing the index value K and the vertical axis representing evaluation (に よ る, ○, Δ, x) based on actual re-rim assembly. As shown in FIG. 3, by using the index value K, it can be confirmed that the air-in property, that is, the tire retreading property can be evaluated numerically without actually reassembling the tire.

1 Heavy load tire 4 Bead part BT Bead toe Co Tire equatorial plane J Regular rim

Claims (4)

A tire retreading determination method for determining tire retreading in a heavy duty tire,
A first measurement for measuring a tire axial distance L1 between bead toes of bead portions on both sides facing each other via a tire equatorial plane and a bead toe radius R1 centering on the tire axis with respect to a heavy load tire before assembling the rim. Process,
A high-pressure filled tire in which a heavy load tire is assembled on a regular rim and filled with a specified internal pressure higher than the normal internal pressure is left in a high temperature atmosphere at a temperature of 60 to 80 ° C. for a period of 7 to 14 days. Tire deformation promotion process,
A second measuring step of measuring a tire axial distance L2 between bead toes and a bead toe radius R2 with respect to the heavy duty tire removed from the regular rim after the tire deformation promoting step;
In addition, the change amounts ΔL = {(L2−L1) / L1} of the tire axial distances L1 and L2 between the bead toes and the change amounts ΔR = {(R2−R1) / R1} of the radiuses R1 and R2 of the bead toes. A tire rehabilitation determination method comprising a determination step of determining tire rehabilitation based on the method.   The tire rehabilitation determination method according to claim 1, wherein the specified internal pressure is in a range of 1.1 to 1.3 times the normal internal pressure. The tire retreading determination method according to claim 1 or 2, wherein in the determination step, tire retreading is determined based on an index value K defined by the following equation (1).
K = ΔR + a × ΔL ---- (1)
(A is a coefficient smaller than 1.0)
× 10 ^-3   4. The tire retreading determination method according to claim 3, wherein the determination step determines that the tire has tire retreading property when the index value K is equal to or less than a preset reference value.

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