WO2019116757A1

WO2019116757A1 - Pneumatic tire manufacturing method

Info

Publication number: WO2019116757A1
Application number: PCT/JP2018/040322
Authority: WO
Inventors: 倫一中山; 英樹島
Original assignee: ＴｏｙｏＴｉｒｅ株式会社
Priority date: 2017-12-15
Filing date: 2018-10-30
Publication date: 2019-06-20

Abstract

In this pneumatic tire manufacturing method, the vulcanization process involves a first stage in which a temperature measurement probe is embedded in the slowest-vulcanizing part of a green tire, a second stage in which, by means of the temperature measurement probe, time series data is acquired that includes a prescribed number of temperature values acquired at intervals 10 seconds or less, and a third stage in which the least-squares method is used to approximate the prescribed number of temperature values included in the time series data with a linear equation and the slope of the approximated linear equation is calculated for each time series data and a coefficient curve is created by plotting these against vulcanization time; the vulcanization process is ended at the time when the inflection point in the coefficient curve has been detected that occurs at the vulcanization time when the vicinity of a target vulcanization temperature is reached. Or, in the pneumatic tire manufacturing method, the vulcanization step involves a first stage in which a temperature measurement probe is embedded in the slowest-vulcanizing part of a green tire, a second stage in which, by means of the temperature measurement probe, time series data is acquired, at intervals 10 seconds or less, of the temperatures of the green tire being vulcanized, and a third stage in which, on the basis of the time series data, the vulcanization process is ended at the time point when heat absorption by the vulcanization reaction has been detected in the vicinity of the target vulcanization temperature.

Description

Method of manufacturing pneumatic tire

The present invention comprises a pair of bead portions, sidewall portions extending outward in the tire radial direction from each of the bead portions, and a tread portion connected to each tire radial direction outer end of the sidewall portions to constitute a tread surface The present invention relates to a method of manufacturing a pneumatic tire including a vulcanization step of heat-vulcanizing an unvulcanized green tire in a mold.

When manufacturing a pneumatic tire that is a rubber product, since the vulcanization process is the most time-consuming process, efforts are still being made to shorten the time of the vulcanization process. On the other hand, if the vulcanization of the rubber portion is insufficient in the vulcanization process, air generated by the vulcanization reaction of the rubber remains in the vulcanized rubber, and such residual air is the cause of tire failure at the product stage. It may be Therefore, in the normal tire production site, the overall variation in the vulcanization process is taken into consideration, for example, due to variations in the temperature of the unvulcanized raw tire, the temperature in the mold, the ambient temperature, etc. due to seasonal factors. The time required for the vulcanization process is set by adding the allowance time that takes into account.

However, setting of the spare time is not preferable from the viewpoint of improving the productivity of the tire, and it has been desired to determine the end of vulcanization for each tire and efficiently execute the vulcanization process.

In the following Patent Document 1, the impedance of the vulcanized sample is measured while the vulcanization process is in progress, and the point at which the increase rate of the polymer resistance value Rp of the vulcanized sample becomes extremely slow is the optimum vulcanization. A real-time cure control method for a vulcanized sample is described which provides a dwell time. However, in this method, it is necessary to measure the impedance measurement for the vulcanized sample by sandwiching the vulcanized sample between the two electrodes, and since the tire is usually a laminate of composite materials, It is difficult to apply to a tire at the time of tire vulcanization.

JP 2003-211459 A

The present invention has been made in view of the above-described circumstances, and an object thereof is to reduce the curing time by positively determining the end point of the curing process for each tire, and to significantly increase the productivity. A method of manufacturing a tire is provided.

The above object can be achieved by the present invention as described below. That is, according to the present invention, a pair of bead portions, sidewall portions extending outward in the tire radial direction from each of the bead portions, and a tread portion connected to each tire radial direction outer end of the sidewall portions to constitute a tread surface A method of manufacturing a pneumatic tire including a vulcanization step of heating and vulcanizing an unvulcanized green tire provided in the mold in a mold, wherein the vulcanization step is carried out at a vulcanization latest portion of the green tire. A first step of embedding a temperature measurement probe, a second step of acquiring a plurality of time series data including a predetermined number of temperature values acquired at intervals of 10 seconds or less by the temperature measurement probe, and a least squares method A coefficient curve is created by approximating a predetermined number of temperature values included in the time series data into a linear equation, calculating the slope of the approximated linear equation for each of the time series data, and plotting against the vulcanization time. And the third stage, The serial coefficient curve to a method for producing a pneumatic tire characterized by terminating the vulcanization step upon detecting an inflection point appearing in the vulcanization time to reach the target vulcanizing temperature near.

The present invention is characterized in the step of vulcanizing a pneumatic tire, and comprises at least first to third steps. First, a pair of bead portions, sidewall portions extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous with each tire radial direction outer end of the sidewall portions to form a tread surface A temperature measurement probe is embedded in the vulcanization latest part of a green tire (first stage), and time series data including a plurality of temperature values acquired at intervals of 10 seconds or less is acquired by the temperature measurement probe ( Second step). Then, the least squares method is used to approximate a predetermined number of temperature values included in time series data to a linear equation, and the inclination of the approximated linear equation is calculated for each time series data, and plotted against the vulcanization time Create a coefficient curve (step 3). Then, when the inflection point appearing in the vulcanization time to reach the vicinity of the target vulcanization temperature of the coefficient curve is detected, the vulcanization process is ended. Thus, the end point of vulcanization can be easily determined in the step of vulcanizing the pneumatic tire. As a result, it is unnecessary to set extra spare time, and the productivity of the pneumatic tire can be enhanced. In addition, since it can be confirmed that the vulcanization reaction is surely completed for each pneumatic tire, a quality assurance system can be established. Note that "around the target vulcanization temperature" preferably means a range of ± 20 ° C of the set target vulcanization temperature, and more preferably means a range of ± 10 ° C of the set target vulcanization temperature. It shall be.

In the method of manufacturing a pneumatic tire, an acquisition interval of temperature values in the time-series data is preferably 1 second or less, and the predetermined number is preferably 10 to 30. This makes it possible to more reliably determine the vulcanization end point of the pneumatic tire, and can further improve the productivity of the pneumatic tire.

In the method of manufacturing a pneumatic tire, it is preferable that the temperature measurement probe is a platinum resistance temperature detector. When the sensitivity of the temperature measurement probe is poor, detection of the end point of vulcanization based on detection of heat generation due to the vulcanization reaction in the vicinity of the target vulcanization temperature, and further, at the plotted vulcanization temperature curve, first in the vicinity of the target vulcanization temperature. In some cases, it may be difficult to detect the end point of vulcanization based on the upward convex inflection point. On the other hand, since the platinum resistance bulb has a very high sensitivity to temperature changes, the end point of vulcanization can be identified with certainty, and therefore the productivity of the pneumatic tire can be further enhanced.

In the method of manufacturing a pneumatic tire, it is preferable that the vulcanized slowest portion is a shoulder portion of the tread portion. This makes it possible to more reliably determine the vulcanization end point of the pneumatic tire, and can further improve the productivity of the pneumatic tire.

In the method of manufacturing a pneumatic tire, the target vulcanization temperature is preferably 120 to 200 ° C.

According to another aspect of the present invention, a tread surface is connected to a pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tire radial direction outer end of each sidewall portion. It is a manufacturing method of a pneumatic tire including a vulcanization process of heating and vulcanizing an unvulcanized green tire provided with a tread portion in a mold, wherein the vulcanization process is the highest curing of the green tire. A first step of embedding a temperature measurement probe in a late part, a second step of acquiring time series data of the temperature of the green tire during vulcanization by the temperature measurement probe at intervals of 10 seconds or less, and the time series The present invention relates to a method of manufacturing a pneumatic tire, comprising: a third step of terminating the vulcanization process when an endotherm due to a vulcanization reaction is detected in the vicinity of a target vulcanization temperature based on data.

The present invention is characterized in the step of vulcanizing a pneumatic tire, and comprises at least first to third steps. First, a pair of bead portions, sidewall portions extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous with each tire radial direction outer end of the sidewall portions to form a tread surface A temperature measurement probe is embedded in the vulcanization latest part of a green tire (first stage), and time series data of the temperature of the green tire during vulcanization is acquired by an interval of 10 seconds or less by the temperature measurement probe (Phase 2). Next, the end of the vulcanization process is ended when an endotherm due to the vulcanization reaction is detected in the vicinity of the target vulcanization temperature based on the time-series data (third stage). Thus, the end point of vulcanization can be easily determined in the step of vulcanizing the pneumatic tire. As a result, it is unnecessary to set extra spare time, and the productivity of the pneumatic tire can be enhanced. In addition, since it can be confirmed that the vulcanization reaction is surely completed for each pneumatic tire, a quality assurance system can be established. The term “near the target vulcanization temperature” preferably means a range of ± 10 ° C. of the set target vulcanization temperature.

In the method of manufacturing a pneumatic tire according to the third aspect of the present invention, the third step plots the vulcanization temperature curve showing the relationship between the temperature of the green tire and the vulcanization time based on the time-series data. Preferably, the method further comprises the step 3b of terminating the vulcanization process when a downward convex inflection point appears in the vicinity of the target vulcanization temperature in the vulcanization temperature curve. According to this configuration, since the downward convex inflection point appearing in the vicinity of the target vulcanization temperature in the vulcanization temperature curve plotted is taken as the vulcanization end point, it is easy and easy to identify. This makes it possible to more reliably determine the vulcanization end point of the pneumatic tire, and can further improve the productivity of the pneumatic tire.

In the method of manufacturing a pneumatic tire, it is preferable that the temperature measurement probe is a platinum resistance temperature detector. When the sensitivity of the temperature measurement probe is poor, detection of the end point of vulcanization based on detection of the endotherm due to the vulcanization reaction in the vicinity of the target vulcanization temperature and furthermore, it appears in the vicinity of the target vulcanization temperature in the plotted vulcanization temperature curve. It may be difficult to detect the end point of vulcanization based on the point of inflection which is downwardly convex. On the other hand, since the platinum resistance bulb has a very high sensitivity to temperature changes, the end point of vulcanization can be identified with certainty, and therefore the productivity of the pneumatic tire can be further enhanced.

In the method of manufacturing a pneumatic tire, the target vulcanization temperature is preferably 125 to 165 ° C., and more preferably 125 to 145 ° C. When the setting of the target vulcanization temperature is high, the vulcanization speed of the pneumatic tire is increased. Therefore, the end point of vulcanization is detected based on the detection of the heat absorption due to the vulcanization reaction, and further the target vulcanization temperature curve is plotted. It may be difficult to detect the end point of vulcanization based on the downward convex inflection point appearing near the vulcanization temperature. On the other hand, when the target vulcanization temperature is 125 to 165 ° C., particularly 125 to 145 ° C., the end point of vulcanization can be easily determined, and therefore the productivity of the pneumatic tire can be further enhanced. The case where the target vulcanization temperature is 125 to 145 ° C. is sometimes referred to as low temperature vulcanization of the pneumatic tire, but in the case of low temperature vulcanization, since the vulcanization speed of the pneumatic tire becomes slow, the conventional tire It was necessary to secure time longer than usual. For this reason, the merit of low temperature vulcanization, such as thermal deterioration suppression of the pneumatic tire under high temperature at the time of vulcanization, may be impaired by an increase in vulcanization time. However, in the present invention, even if the low temperature vulcanization (target vulcanization temperature is 125 to 145 ° C.), the margin time can be designed to be shorter than usual, so that the physical property deterioration of the pneumatic tire due to thermal deterioration is prevented. Can.

A tire meridional cross section showing an example of a tire according to the present invention Sectional view conceptually showing a mold used for vulcanizing a tire Example of coefficient curve and vulcanization temperature curve in one embodiment of the present invention An example of a graph showing a vulcanization temperature curve in another embodiment of the present invention

First Embodiment
A first embodiment of the present invention will be described with reference to the drawings. The green tire 9 shown in FIG. 1 is continued to the tire radial direction outer end of each of the pair of bead portions 1, the sidewall portion 2 extending outward from the bead portions 1 in the tire radial direction, and the sidewall portion 2 It is a pneumatic tire provided with the tread part 3 which constitutes a tread. An annular bead core 1 a is disposed in the bead portion 1.

The carcass layer 4 passes from the tread portion 3 through the sidewall portion 2 to the bead portion 1, and the end portion thereof is folded back via the bead core 1a. The carcass layer 4 is constituted by at least one carcass ply. The carcass ply is formed by covering a carcass cord extending at an angle of about 90 ° with the circumferential direction of the tire with a topping rubber.

The belt layer 5 is bonded to the outside of the carcass layer 4 in the tread portion 3 and is covered with the tread rubber 6 from the outside. The belt layer 5 is composed of a plurality of (two in the present embodiment) belt plies. Each belt ply is formed by covering a belt cord extending obliquely with respect to the tire circumferential direction with a topping rubber, and the belt cords are stacked so as to cross the plies in opposite directions.

The tread rubber 6 may be composed of only one layer, or may be composed of a so-called cap base structure having a base tread on the inner side in the tire radial direction and a cap tread located on the outer peripheral side thereof.

The green tire 9 shown in FIG. 1 is a green tire in an unvulcanized state, and is shaped into the shape of a product tire in a vulcanization step to be described later (see FIG. 2) and various treads on its tread surface A pattern is formed.

In vulcanization molding of the green tire 9, a mold 10 as shown in FIG. 2 is used. A green tire 9 is set in the mold 10 in an unvulcanized state, and the green tire 9 in the mold 10 is heated and pressurized to perform a vulcanization process.

The mold 10 includes a tread mold portion 11 in contact with the tread surface of the green tire 9, a lower mold portion 12 in contact with the tire outer surface facing downward, and an upper mold portion 13 in contact with the tire outer surface facing upward. These are configured to be displaceable between the mold clamping state and the mold opening state by an opening and closing mechanism (not shown) installed around the periphery, and the structure of such an opening and closing mechanism is known. The tread mold portion 11 is further divided into a plurality of parts in the circumferential direction, and is movable in the radial direction of the green tire 9 disposed in the mold 10. Further, the mold 10 is provided with a platen plate (not shown) having a heat source such as an electric heater or a steam jacket, thereby heating each mold portion.

A central mechanism 14 is provided coaxially with the tire at a central portion of the mold 10, and a tread mold portion 11, a lower mold portion 12 and an upper mold portion 13 are installed around this. The central mechanism 14 has a rubber bag-like bladder 15 and a center post 16 extending in the axial direction of the tire, and the center post 16 is provided with an upper clamp 17 and a lower clamp 18 for gripping the end of the bladder 15 ing.

In the central mechanism 14, a medium supply passage 21 for supplying a heating medium into the bladder 15 is vertically extended, and a jet outlet 22 is formed at the upper end of the medium supply passage 21. The medium supply passage 21 is connected to a supply pipe 24 through which the heating medium supplied from the heating medium supply source 23 and the pressurized medium supplied from the pressurized medium supply source 26 flow. The heating medium is supplied in response to the opening and closing operation of the valve 25, and the pressurized medium is supplied in response to the opening and closing operation of the valve 28.

Further, a medium discharge path 31 for discharging the high-temperature high-pressure fluid in which the heating medium and the pressure medium in the bladder 15 are mixed is vertically extended in the central mechanism 14, and the upper end of the medium discharge path 31 is A recovery port 32 is formed. A discharge pipe 34 through which a high temperature and high pressure fluid flows is connected to the medium discharge path 31, and a blow valve 33 for operating the opening and closing of the medium discharge path 31 is provided in the discharge pipe 34. The pump 35 may use a method of forcibly circulating the high-temperature high-pressure fluid so that the high-temperature high-pressure fluid passing through the medium discharge passage 31 is re-supplied to the inside of the bladder 15 via the medium supply passage 21.

Hereinafter, the vulcanization step in the production method of the present invention will be specifically described.

First, as shown in FIG. 2, the green tire 9 is set in the mold 10, and the green tire 9 is shaped close to the inner surface of the mold 10 by the inflated bladder 15. Thus, the green tire 9 is held by the bladder 15 and is applied to each of the tread mold portion 11, the lower mold portion 12 and the upper mold portion 13. At this time, a temperature measurement probe is embedded in the lowest cure part of the green tire 9 (first stage). The slowest vulcanization portion means a portion where the vulcanization of the tire is most difficult to progress, and usually means the shoulder portion of the tread portion 3. In particular, among the shoulder portions, it is preferable to set a position at which the thickness of the tread portion 3 is maximized, which is measured along the normal to the inner surface of the tread portion 3 after vulcanization, as the vulcanized slowest portion. In any case, in the present invention, in order to measure the vulcanization temperature at the slowest vulcanization portion, a temperature measurement probe is embedded in the slowest vulcanization portion of the green tire 9. As the embedding method, for example, when the temperature measurement probe is disposed at a position corresponding to the shoulder portion of the tread mold portion 11 and the tread mold portion 11 moves in the radial direction of the green tire 9, the green tire 9 is addressed It is conceivable to design the temperature measurement probe to be embedded while being pushed into the green tire 9. The temperature measurement probe embedded in the green tire 9 as described above measures the temperature of the green tire during the vulcanization process, and when the vulcanization process is finished, the tire is removed from the mold 10 including the tread mold portion 11. It is sufficient to simultaneously withdraw the temperature measurement probe from the slowest part of the vulcanization.

In the present invention, as a temperature measurement probe used when measuring the vulcanization temperature, a resistance temperature detector can be used which utilizes the property that the electric resistance of metal changes with temperature change. Such metals can be exemplified by platinum, nickel, copper and the like, but in the present invention, platinum temperature measurement with a large change in resistance (sensitivity) to temperature changes and as a result, the sensitivity to temperature changes is extremely high. A resistor can be used particularly preferably.

Subsequently, the mold 10 is heated to heat the tire 9 from the outer surface of the tire, and the heating medium is supplied to the bladder 15 in the mold 10 at a high temperature to heat the tire 9 from the inner surface. And heating is performed to cure the green tire 9. The mold 10 is preheated by the above-described steam jacket or the like, whereby the outside heating is performed. The inner heating is performed by supplying a heating medium into the bladder 15 through the medium supply passage 21 after shaping of the tire 9. After the heating medium is supplied for a predetermined time, a pressurized medium is subsequently supplied into the bladder 15 to press the tire 9 at a high pressure. For example, steam or high-temperature water is used as the heating medium, and an inert gas such as nitrogen gas or steam is used as the pressurizing medium.

The temperature measurement probe acquires time series data including a plurality of temperature values acquired at intervals of 10 seconds or less (second stage). For acquisition of such time series data, it is possible to use a high precision digital data logger (generally having a temperature resolution of about 0.001 ° C., an accuracy of about 0.005 ° C., a minimum acquisition interval of 1 second for temperature values) commonly available in the market. . In the second stage, when the data acquisition interval of the time series data of the temperature of the green tire during vulcanization is short, it is preferable because the final end point of vulcanization can be determined more accurately. Specifically, the acquisition interval of the temperature value in the time series data is preferably 5 seconds or less, and more preferably 1 second or less. On the other hand, if the data acquisition interval of the time-series data of the temperature of the green tire during vulcanization is too short, the noise may be rather large and it may be difficult to accurately determine the vulcanization end point. Therefore, the acquisition interval of the temperature value in the time series data is preferably 0.5 seconds or more.

After the second step, the least squares method is used to approximate a predetermined number of temperature values included in the time series data to a linear equation, and the value of the slope of the approximated linear equation is calculated for each time series data. A coefficient curve is created by plotting against (step 3). FIG. 3 shows an example of a coefficient curve and a vulcanization temperature curve in an embodiment of the present invention. In FIG. 3, the horizontal axis represents the time (seconds) when the end point of mold clamping of the mold 10 is the vulcanization start point, the vertical axis represents the temperature (° C.) of the green tire, A represents a vulcanization temperature curve, B Indicates a coefficient curve. In this embodiment, the acquisition interval of the temperature value is 1 second, and the temperature value included in one time series data is 20 ((predetermined number) = 20). Specifically, 20 temperature values acquired at 1-second intervals are grouped as one time-series data, the slope of this time-series data is calculated using the least squares method, and vulcanization time is calculated for each time-series data. On the other hand, the slope calculated in time series is plotted. In FIG. 3, the inclination calculated based on each time series data is plotted at a point with respect to the vulcanization time.

When approximating to a linear equation using the least squares method, the predetermined number of temperature values to be used is preferably 10 to 30 continuous in time series, and more preferably 15 to 25. If the predetermined number is 5 or less, the noise of the coefficient curve may be large, and detection of the inflection point may be difficult. If the predetermined number exceeds 30, the size of the inflection point may be reduced, which is also detected May be difficult.

In the present embodiment, when the target vulcanization temperature is set to 150 ° C., an inflection point P is observed around a portion where the vulcanization temperature curve exceeds 140 ° C. When this inflection point P is detected, the vulcanization process is ended. In the present invention, the target vulcanization temperature is preferably 120 to 200 ° C., and more preferably 140 to 180 ° C.

After completion of the vulcanization process, the temperature measurement probe disposed in the mold 10 is removed from the vulcanized tire while the mold 10 is in the released state. As a result, the end point of vulcanization can be determined for each tire, and the pneumatic tire can be manufactured while shortening the vulcanization time.

The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

Second Embodiment
A second embodiment of the present invention will be described with reference to the drawings. The green tire 9 shown in FIG. 1 is continued to the tire radial direction outer end of each of the pair of bead portions 1, the sidewall portion 2 extending outward from the bead portions 1 in the tire radial direction, and the sidewall portion 2 It is a pneumatic tire provided with the tread part 3 which constitutes a tread. An annular bead core 1 a is disposed in the bead portion 1.

The temperature measurement probe acquires time-series data of the temperature of the green tire during vulcanization at intervals of 10 seconds or less (second stage). For acquisition of such time series data, it is possible to use a high precision digital data logger (generally having a temperature resolution of about 0.001 ° C., an accuracy of about 0.005 ° C., a minimum acquisition interval of 1 second for temperature values) commonly available in the market. . In the second stage, when the data acquisition interval of the time series data of the temperature of the green tire during vulcanization is short, it is preferable because the final end point of vulcanization can be determined more accurately. Specifically, it is preferable to acquire time series data of the temperature of the green tire during vulcanization at intervals of 5 seconds or less, and it is preferable to acquire at intervals of 1 second or less. On the other hand, if the data acquisition interval of the time-series data of the temperature of the green tire during vulcanization is too short, the noise may be rather large and it may be difficult to accurately determine the vulcanization end point. For this reason, the data acquisition interval of the time-series data of the temperature of the green tire during vulcanization is preferably 0.5 seconds or more.

After the second stage, the end of the vulcanization process is ended when an endotherm due to the vulcanization reaction is detected in the vicinity of the target vulcanization temperature based on the time-series data (third stage). Thus, the end point of vulcanization can be easily determined in the step of vulcanizing the pneumatic tire. The target vulcanization temperature is preferably 125 ° C. to 165 ° C., more preferably 125 ° C. to 145 ° C., and particularly preferably 125 ° C. to 135 ° C., because this makes it easy to identify the vulcanization end point. . As a method of detecting the heat absorption due to the vulcanization reaction, the temperature change amount of the green tire in a predetermined period (for example, 1 second if the data acquisition interval is 1 second) is calculated in the vicinity of the target vulcanization temperature, and the temperature change amount It is possible to make a decision based on

In the present invention, the end point of vulcanization can be determined more simply by dividing the third step into two. First, based on the time series data, a vulcanization temperature curve showing the relationship between the temperature of the green tire and the vulcanization time is plotted (step 3a). FIG. 4 is an example of a graph showing a vulcanization temperature curve according to an embodiment of the present invention, where A is the temperature (° C.) of the green tire when the mold 10 completion point is the vulcanization start point. The vulcanization temperature curve which makes a vertical axis | shaft and time (seconds) a horizontal axis is shown. In this embodiment, a target vulcanizing temperature is set to 130 ° C., and a vulcanizing temperature curve A is shown when time-series data of the temperature of a green tire is acquired at one second intervals. The vulcanization temperature curve B is an enlarged view of the vicinity of the target vulcanization temperature (about 2000 seconds to about 8000 seconds before) of the vulcanization temperature curve A. After the step 3a, the vulcanization step is ended when a downwardly convex inflection point P appearing near the target vulcanization temperature is detected in the vulcanization temperature curve A plotted (step 3b). In the present embodiment, in the vulcanization temperature curve B, a point P corresponding to a downwardly convex inflection point appearing near the target vulcanization temperature (130 ° C.) can be easily detected, and this point P is detected. Vulcanization can be terminated with the time point of curing as the vulcanization end point.

First Embodiment
Example 1, Comparative Example 1
In order to specifically show the constitution and effect of the present invention, the vulcanization of the sample tire (tire size: 275 / 70R22.5) was carried out using the vulcanization mold 10 described in FIG. At that time, a platinum RTD connected to a high precision digital data logger (manufactured by Fluke, trade name "1586A") in the mold 10 , It was disposed at a position corresponding to the shoulder portion of the pneumatic tire.

The vulcanization target temperature was set to 150 ° C., and the sample tire was heated and vulcanized so as to have a vulcanization temperature curve shown in FIG. In the comparative example 1, the vulcanization process is completed at the inflection start point time 57 minutes (= 3420 seconds) of the inflection point P, and in the example 1, the inflection end point time of the inflection point P is added at 59 minutes (= 3540 seconds) The vulcanization process was completed.

When the obtained sample tire was disassembled, in Comparative Example 1, air bubbles of 1 to 2 mm called blisters remained in the rubber portion in the vicinity of the tip of the probe. On the other hand, in Example 1, no blister remained in the rubber portion in the vicinity of the tip of the probe, and it was found that the vulcanization reaction was surely completed.

Claims

A pair of bead portions, sidewall portions extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous with each tire radial direction outer end of the sidewall portions to form a tread surface A method for producing a pneumatic tire, comprising a vulcanization step of heat-curing a green tire in a mold in a mold.
A time series including a predetermined number of temperature values acquired at intervals of 10 seconds or less by the first step of embedding a temperature measurement probe in the vulcanization latest portion of the green tire, and the first step of the vulcanization step; A predetermined number of temperature values included in the time series data are approximated to a linear equation using a second step of acquiring a plurality of data and a least squares method, and the slope of the approximated linear equation is calculated for each of the time sequential data , And a third step of creating a coefficient curve by plotting against the vulcanization time,
A method of manufacturing a pneumatic tire, comprising: terminating the vulcanization step when detecting an inflection point appearing in a vulcanization time for reaching near a target vulcanization temperature of the coefficient curve.
The method for manufacturing a pneumatic tire according to claim 1, wherein an acquisition interval of temperature values in the time-series data is 1 second or less.
The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein the predetermined number is 10 to 30.
The method for manufacturing a pneumatic tire according to any one of claims 1 to 3, wherein the temperature measurement probe is a platinum resistance temperature detector.
The method for manufacturing a pneumatic tire according to any one of claims 1 to 4, wherein the vulcanization latest portion is a shoulder portion of the tread portion.
The method for producing a pneumatic tire according to any one of claims 1 to 5, wherein the target vulcanization temperature is 120 to 200 属 C.
A pair of bead portions, sidewall portions extending outward in the tire radial direction from each of the bead portions, and a tread portion continuous with each tire radial direction outer end of the sidewall portions to form a tread surface A method for producing a pneumatic tire, comprising a vulcanization step of heat-curing a green tire in a mold in a mold.
The first step of embedding a temperature measurement probe in the vulcanization latest portion of the green tire, and the time-series data of the temperature of the green tire being vulcanized by the temperature measurement probe by the first step of embedding the temperature measurement probe in the last stage of vulcanization of the green tire And a third step of terminating the vulcanization process when an endotherm due to the vulcanization reaction is detected in the vicinity of the target vulcanization temperature based on the time-series data. And a method of manufacturing a pneumatic tire.
Furthermore, the third step is a step 3a of plotting a vulcanization temperature curve indicating the relationship between the temperature of the green tire and the vulcanization time based on the time series data, and the target by the vulcanization temperature curve plotted. The method for manufacturing a pneumatic tire according to claim 7, comprising the step 3b of terminating the vulcanization step when a downward convex inflection point appearing near the vulcanization temperature is detected.
The method for manufacturing a pneumatic tire according to claim 7, wherein the temperature measurement probe is a platinum resistance temperature detector.
The method for manufacturing a pneumatic tire according to any one of claims 7 to 9, wherein the vulcanization latest portion is a shoulder portion of the tread portion.
The method for producing a pneumatic tire according to any one of claims 7 to 10, wherein the target vulcanization temperature is 125 to 165 ° C.