JPH05162137A - Control method of vulcanization of tire - Google Patents

Abstract

PURPOSE:To vulcanize an indivisual tire at the optimum and shortest time without injuring the tire, by a method wherein a temperature change within the tire until loss of flowability from a start of vulcanization is measured by a thermocouple, the thermocouple is pulled out and a necessary vulcanizing time is obtained by estimating a temperature rising state until completion of the vulcanization by an obtained initial temperature rising curve. CONSTITUTION:It is preferable that insertion of a temperature-sensing part such as a thermocouple into a tire is performed when a flow where an outer circumference of an unvulcanized tire is deformed along the inside of a mold is almost completed and measurement of at least one position is performed. Then a temperature rising pattern in a temperature region where it becomes a vulcanization starting temperature from the normal temperature is measured and the temperature-sensing part is pulled out. At this time, since rubber still has flowability, the tire is managed without being injured. An obtained initial temperature rising curve and an initial temperature rising part obtained by a reference curve are compared with each other and the temperature rising state up to completion of the vulcanization is estimated by a calculation formula of the temperature rising curve. A relation between a vulcanizing time and degree of vulcanization is calculated by the estimating curve and a necessary vulcanizing time is obtained. Then when this time is attained, a signal is given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a tire vulcanization control method.

[0002]

2. Description of the Related Art Conventionally, in order to produce a good quality tire in the shortest vulcanization time, the temperature of a green tire loaded in a mold is measured individually for each tire and the measured temperature A tire vulcanization control method has been proposed in which the vulcanization amount and vulcanization degree distribution are calculated to predict the end of vulcanization (Japanese Patent Laid-Open Nos. 54-18881 and 63-1570).
No. 8, JP-A-63-1710).

[0003]

However, JP-A-54-1
No. 8881 is a method in which, when actually measuring the vulcanization temperature, a temperature-sensitive part that changes the temperature of a thermocouple or the like into an electric signal is directly inserted into the tire until the end of vulcanization, so the temperature-sensitive part is removed after the end of vulcanization. At that time, there was a problem that scratches remained, which was not preferable as a product tire.

On the other hand, JP-A-63-15708 and 63
-17010 does not damage the product tire because the temperature-sensing part is installed not at the inside of the tire but at both the outer surface side and the inner surface side of the tire for actual measurement, but this method does not damage the product tire. Since the temperature distribution and the vulcanization degree distribution inside the tire are predicted by measuring only the surface, there is a problem that the actual internal heat history of each individual tire cannot be determined. In particular, the temperature-sensitive part on the inner surface of the tire is inevitably attached to the bladder or a position in the vicinity thereof due to the relationship with the bladder, which is difficult to attach, and there is a great problem in accuracy. Further, even if it is attached, there is a possibility that the bladder may be stretched during the vulcanization to cause a positional shift, which is also a problem in terms of accuracy. In addition, the repeated use may damage the temperature sensing part.

Therefore, the temperature sensitive parts are installed on both sides of the tire to measure the temperature, and the internal temperature distribution and the vulcanization degree distribution are calculated by the finite element method (FEM) or the difference method, and the vulcanization is performed. This kind of method of predicting the shortest time of vulcanization and controlling vulcanization is considered to have a problem in the tire temperature measuring means itself.

An object of the present invention is to provide a vulcanization control method for a tire, which can easily and accurately measure and estimate the temperature and vulcanization distribution inside the tire without damaging the tire and which has a high temperature history detection accuracy. Is in the point of providing.

[0007]

[Means for Solving the Problems] When considering the factors of variation when vulcanizing a tire, first of all, there are variations in the temperature of the green tire and the bladder temperature. This fluctuates daily, daily, and seasonally, and is considered to mainly affect the initial vulcanization temperature. Secondly, the factors that affect the temperature during vulcanization are the thickness of the tire and the thickness of the bladder, which vary within the lot and between lots, and are mainly the temperature rise rate and temperature rise level of each part of the tire. It is considered to be a factor that affects the

Therefore, a change in the temperature rise pattern in each part inside the tire is reproduced by simulation calculation by the finite element method (FEM) when the temperature of the green tire and the bladder change and when the thickness of the tire and the bladder change. As a result, it was found that the actual fluctuation factors can be accurately reproduced by the temperature rise simulation. In addition, it was found from the temperature rise pattern of each part in the tire, particularly the latest part of vulcanization, that the vulcanization initial temperature has a very close relationship with the tire thickness, the bladder thickness, and these initial temperatures. Furthermore, this fact has been found that even when the vulcanization conditions of the tire (external pressure conditions such as temperature, internal pressure conditions such as steam, hot water temperature and time) are changed, a certain tendency occurs accurately. This was the same even if the vulcanization model was changed.

An important point is that the temperature fluctuation can be accurately grasped if the initial temperature rise pattern in the tire can be known. For example, if the initial temperature of the green tire or bladder is low, the rise of the temperature rise pattern in the early stage of vulcanization is slow, and if the tire thickness or the thickness of the bladder is thick, the angle of the temperature rise pattern in the early stage of vulcanization becomes dull. Therefore, if the external pressure and internal pressure (mold side temperature and internal pressure side pressure and temperature inside the tire) can be controlled to be constant, the vulcanization temperature based on the above-mentioned initial temperature rise pattern in the tire can be controlled. The temperature history of the lag part can be easily and accurately predicted.

In the meantime, when actually measuring the initial temperature rise pattern inside the tire, it is most preferable in terms of accuracy to insert the temperature sensitive portion at one or more positions inside the tire for actual measurement. Specifically, as shown in FIG. 1, the temperature sensitive part 3 can be freely projected to the bead thickest parts A and E, the shoulder thickest parts B and D, and the tread center part C of the upper mold 1 and the lower mold 2, respectively. Install in and measure. However, since the water vapor sent into the bladder (not shown) accumulates as a drain on the lower mold 2 side, the temperature rise on the lower mold 2 side is generally slower. It is desirable to install and measure in the thick portion E and the shoulder thickest portion D.

The problem in the actual measurement is the timing of the insertion of the temperature sensitive part. This is, for example, when a green tire is loaded in a mold, the green tire is inflated with a bladder filled with steam, and the upper and lower molds of the mold are inflated. There is a time when the rubber largely flows while the molds are brought close to each other and the molds are tightened, and the outer surface of the unvulcanized tire follows the shape of the inner surface of the mold. If the temperature sensing part is inserted inside the tire at that time, the temperature sensing part may be bent or scratched.Therefore, when the flow is almost stopped, insert the temperature sensing part inside the unvulcanized tire for positioning. It is desirable to do. This time is slightly different depending on the conditions, but the internal temperature of the tire is about 40-
It is around 50 ° C. In terms of time, it is roughly determined for each tire type and tire size, but about 120 seconds after the start of vulcanization by starting the closing of the kettle and introducing the internal pressure. Although it may be possible to determine the insertion time by the mold temperature, the mold temperature is 140 to 190 from the beginning in the tire manufacturing process.
Since the temperature reaches ℃, the timing of insertion cannot be controlled by temperature. It should be noted that the temperature-sensitive portion is preferably cylindrical, and the diameter is preferably as small as possible. This is because the temperature sensing unit itself affects the measured temperature and causes an error.

On the other hand, the vulcanization reaction of rubber is temperature-dependent, and at high temperatures the vulcanization reaction is completed quickly, and at low temperatures the vulcanization reaction is slow. However, even if it is heated at a high temperature, the vulcanization reaction does not immediately occur, and the compounding design is designed to have an introduction time until the vulcanization reaction starts. And 130
The vulcanization reaction gradually starts when the temperature reaches about ℃. FIG. 2 is a graph showing the relationship between the temperature rising curve and the vulcanization reaction rate in the thickest part D of the shoulder. The area surrounded by the vulcanization reaction rate curve and the X axis is the relative vulcanization reaction amount up to that time. Figure 2
From this, it is recognized that the vulcanization reaction hardly progresses until the temperature reaches 130 ° C. However, since the actual measurement point is the center position of the thickest part D of the shoulder, the closer the heat is to the mold surface, the more the vulcanization reaction has started on the mold surface, but the amount of vulcanization reaction does not hinder. Is.

From the above point, if the temperature rise pattern in the temperature range from room temperature to about 130 ° C. is actually measured and the temperature sensing part is pulled out when exceeding this temperature range, the fluidity is still maintained. , Rubber also flows to the part where the temperature sensing part is pulled out, so you do not have to damage the tire. Further, unless the temperature rise pattern up to at least about 100 ° C. is actually measured, it becomes difficult to accurately select the calculated similar pattern, and there is also a problem that it is difficult to make an accurate estimation. Further, when the tire type is different for trucks and buses and passenger cars, the temperature rising rate and the maximum temperature reached differ, so that it is necessary to secure sufficient measurement accuracy of the initial temperature rising pattern. Measure the initial temperature rise pattern up to about ℃ and use the finite element method (F
It is appropriate to determine the vulcanization end by analyzing and determining the variation factor of EM), calculating it, estimating the temperature rise pattern of the latest portion after that.

Based on the above findings, the present invention is capable of protruding to the inner surface of the mold when the flow period during which the rubber on the surface of the green tire filled in the mold flows and is deformed into a shape along the inner surface of the mold. The step of inserting the temperature-sensing part provided in the green tire to a predetermined depth, the step of measuring the internal temperature of the tire which changes until just before the vulcanization reaction of the rubber starts to lose fluidity, the predetermined When the temperature reaches the temperature, the step of retracting the temperature sensitive part to the inner surface of the mold, the initial temperature rise curve obtained by the temperature measurement above is compared and inquired with the initial temperature rise part calculated by the preset standard temperature rise curve. Then, the step of estimating the temperature rise state until the end of vulcanization by the temperature rise curve calculation formula is calculated, and the relationship between the vulcanization time and the vulcanization degree is calculated from the estimated temperature rise curve to calculate the required vulcanization time. Fixed That step, and it was adopted pressurized 硫制 control method of the tire, characterized in that comprising the step of issuing a signal to move to reaches if vulcanization end step between the required vulcanization.

The finite element method (FEM) or the difference method can be adopted as the calculation method of the thermal analysis.

[0016]

The present invention is based on the knowledge that the temperature variation of the tire during vulcanization can be sufficiently estimated by the initial temperature rise pattern in the tire, and the temperature-sensitive part is inserted into the tire at the early stage of vulcanization.
By extracting it at the start of vulcanization, each tire can be individually vulcanized in the optimum and shortest vulcanization time, so vulcanizing tires of the same type and same name with a uniform time setting The productivity is significantly improved as compared with the conventional method. In addition, each tire is individually vulcanized in the optimum and shortest vulcanization time, so over-vulcanization does not occur and vulcanization does not become insufficient. The property is improved.

Further, according to the present invention, since the temperature sensitive portion can be removed after the initial stage of vulcanization, there is no problem such as scratches or holes in the product tire after vulcanization as in the conventional case. In addition, it is possible to provide a tire that is excellent in terms of appearance and properties.

Further, in the method of the present invention, the temperature inside the tire is directly measured by inserting the temperature sensitive portion into the tire, so that the surface of the tire is measured, and thereby the thermal history inside the tire is estimated. Compared with the above, the accuracy is better, and since it is not necessary to install the temperature sensing part on the bladder side and insertion / extraction can be performed from the mold side, actual measurement is extremely easy.

[0019]

[Examples] The accuracy according to the present invention was examined for a truck-bus radial tire having a tire size of 1000R20 14PR and a radial tire for a passenger vehicle having a tire size of 195 / 70R14.

Table 1 shows the results. In the table,
The tire thickness indicates the thickness of the thickest part of the shoulder, and the confidence range at the end of vulcanization is the measured value of the temperature-sensitive part in the thickest part of the shoulder of each tire measured until the end of vulcanization, and only the initial vulcanization is measured. , The deviation of the estimated value (theoretical value) estimated by comparing and inquiring with a preset standard temperature rising curve, that is, the accuracy is shown. The standard temperature rise curve is the standard thickness of the thickest part of the shoulder 40, 40 ± 0.1, 40 ± 0.2, 40 ±
0.3 ... 40 ± 1.0, 40 ± 1.5, 40 ± 2.0 m
/ m, standard temperature of green tires 23 ± 1, 23 ± 2, 2
3 ± 3, ... 23 ± 10, 23 ± 15, 23 ± 20 ° C. were combined and measured values were created.

[0021]

[Table 1] From Table 1, the wider the measurement temperature range, the narrower the estimation range, and the lower the vulcanization temperature, the higher the estimation accuracy becomes.
In the step of determining the required vulcanization time, it is important to determine the time in consideration of the errors caused by these in accordance with the setting accuracy.

Next, with respect to a truck bus radial tire having a tire size of 1000R20 14PR, the shortest vulcanization time was determined using this method, and the conventional blow point method (Comparative Example 1) and the equivalent vulcanization time method (Comparative Example 2) were used. ) And examined. The standard temperature rising curve is similar to the above, and in this example, the temperature rises when the standard thickness of the thickest part of the shoulder is ± 0.1 mm and the standard temperature of the green tire is ± 10 ° C. It is decided by the curve. The calculation of the vulcanization end step is performed so that the equivalent vulcanization time at the temperature sensing portion position reaches a predetermined time at the time of venting pressure in the vulcanization step.

[0023]

[Table 2] From FIG. 3 and Table 2, according to the method of the present invention, the productivity is shortened by about 2 to 6 minutes as compared with the conventional blow point method and the equivalent vulcanization time method, and the productivity is significantly improved. Also, not only the shortest vulcanization but also the optimum vulcanization is performed, so the depolymerization of rubber molecules due to heating is reduced, the cornering power and rolling resistance are reduced due to overvulcanization, and the high speed durability is also reduced. Is suppressed.

[0024]

As described above, since the present invention is a method of predicting the optimum vulcanization end point by the initial temperature rise pattern in the tire at the early stage of vulcanization, the temperature-sensitive part damages the product tire. There is no fear, and the heat history inside the tire can be well estimated. Therefore, each green tire can be individually vulcanized in the optimum and shortest vulcanization time, and the productivity can be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an installation place of a temperature sensing unit.

FIG. 2 is a graph showing the relationship between the vulcanization reaction rate and the thickest part of the shoulder.

FIG. 3 is a graph showing a temperature rise curve in the thickest part of the shoulder.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location B29L 30:00 4F

Claims (1)

[Claims] 1. A temperature-sensing portion provided on the inner surface of a mold so as to project freely when the flow period during which the rubber on the surface portion of the green tire filled in the mold flows and is deformed into a shape along the inner surface of the mold. Inserting the tire to a predetermined depth in the green tire, measuring the internal temperature of the tire that changes until just before the rubber vulcanization reaction starts and loses fluidity, feel at the time of reaching the predetermined temperature The step of retracting the warm part to the inner surface of the mold, the initial temperature rising curve obtained by the temperature measurement is compared with the initial temperature rising part calculated by the preset standard temperature rising curve, and the temperature rising curve calculation formula is used. A step of estimating the temperature rising state until the end of vulcanization, a step of determining a required vulcanization time by calculating the relationship between the progress of vulcanization time and the degree of vulcanization from the estimated temperature rising curve,
And a method of controlling vulcanization of a tire, which includes a step of issuing a signal for shifting to a vulcanization ending step when a required vulcanization time is reached.