JPH01113211A - Measurement of internal temperature of vulcanized object and control of tire vulcanization - Google Patents

Abstract

PURPOSE:To measure accurately the internal temperature of a tire as well as to control exactly a tire vulcanization, by estimating said temperature from the temperature measured in the boundary between a mold unit and the tire and that measured in the center post assembly of a bladder unit. CONSTITUTION:A first temperature at least at one point in or near the boundary between a mold unit 7 and the tire is measured by means of first temperature sensors 4a-4c, during a tire vulcanization. A second temperature at the center bladder unit 8 is measured by means of second temperature sensors 5a during the tire vulcanization. The internal temperature distribution is calculated from the first and second temperatures and the distribution of degree of vulcanization on the inside of the tire is estimated. From said distribution, the minimum degree of vulcanization is detected, and according to it the timing to stop the heat supply form a vulcanizer is determined. In this way, the internal temperature of the tire can be accurately determined. Thus, it is possible to estimate very accurately the vulcanizing state in the tire and vulcanize the tire in the best condition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a technique for vulcanizing objects made of rubber or plastic, and in particular to a method for measuring the internal temperature of a rubber or plastic object during vulcanization. The present invention relates to a method for controlling vulcanization of a pneumatic tire.

(Prior Art) In the process of manufacturing pneumatic tires, green tires are placed inside a vulcanizer, heated and pressurized. In this case, in order to produce tires with the desired performance, it is necessary to control the vulcanization process accurately and reliably. In the conventional vulcanization method, the temperature of the vulcanization mold and the temperature and pressure inside the bladder are kept constant, and heating and pressurization are performed for a predetermined period of time. In reality, the temperature at various points inside the tire depends on the differences in the structure of the raw tire,
It will vary due to various factors such as mold temperature, pressure variations, etc. These fluctuations change from day to day and from season to season. Therefore, in conventional vulcanization methods, the vulcanization time is usually set longer than necessary to avoid insufficient vulcanization. Therefore, there is a risk that undesirable over-vulcanization may occur, and there is a risk that a tire with desired performance may not be obtained. Furthermore, if the vulcanization time is prolonged, manufacturing efficiency deteriorates and a larger amount of heating medium is required, resulting in higher costs.

(Problems to be Solved by the Invention) Various vulcanization control methods have been proposed to eliminate the above-mentioned drawbacks. For example, US Pat. No. 3,819°915 discloses that a thermometer is inserted into a tire set in a vulcanizer to measure the temperature inside the tire, and the vulcanization state of the tire is controlled based on this temperature. A tire vulcanization control method is described.

However, this method has the disadvantage that holes formed when the thermometer inserted into the tire is pulled out remain on the tire surface after vulcanization, which significantly impairs the commercial value of the tire.

Furthermore, even if a thermometer is inserted into the tire, it is difficult to accurately measure the internal temperature of the tire. In addition, since the temperature can only be measured at predetermined points inside the tire, it is not possible to know the temperature at the point inside the tire where vulcanization occurs slowest (minimum vulcanization point), and therefore vulcanization can be controlled with precision. There are some drawbacks that you cannot do. In addition, it is a troublesome task to insert and remove the thermometer from the tire, and the thermometer also has the disadvantage of being easily damaged. Furthermore, this known method requires that the thermometer be inserted through the outer surface of the tire, making it impossible to measure the temperature at various points inside the tire.

U.S. Patent No. 3,649,729 discloses that the temperature at the boundary between the tire and the mold and the temperature at the boundary between the tire and the bladder are measured, and the temperature inside the tire is calculated from these temperatures. A vulcanization control method is disclosed in which the degree of vulcanization is estimated from the following.

Although this known method requires the use of a temperature sensor that can be placed at the interface between the tire and the mold and bladder, it is practical to place a temperature sensor between the inner surface of the tire and the outer surface of the bladder. It is extremely difficult. When using a telescoping bladder, such as a rubber one, it is not possible to attach the temperature sensor to the surface of the bladder. Additionally, when using a foldable bladder, a temperature sensor can be attached to the outside surface of the bladder, but the bladder is generally replaced with a new one after being used for several days, so the temperature sensor also ends up being discarded. Become.

This known method therefore has the disadvantage that it is costly and the maintenance of the temperature sensor is very complicated.

In the two known methods described above, the degree of vulcanization is calculated according to the well-known Arlenius equation on the assumption that the minimum vulcanization point inside the tire is fixed at one point. However, since the minimum vulcanization point actually moves inside the tire during vulcanization, there is a fatal drawback in that the degree of vulcanization cannot be detected accurately.

Further, US Pat. No. 4,371,483 discloses a vulcanization control method in which the temperature distribution inside the tire is derived from the measured temperature and the minimum vulcanization point is determined from this. According to such a method, it is possible to track the minimum vulcanization point that moves inside the tire during vulcanization.

However, this method cannot accurately measure the temperature at the boundary between the tire, the mold, and the bladder. In other words, the temperature at the boundary between the mold and the tire outer surface is estimated by actually measuring the temperature of the outer mold surface, but since the temperature of the outer mold surface changes depending on the ambient temperature, does not reflect the temperature of the tire's outer surface. Furthermore, this known method estimates the temperature at the interface between the inner tire surface and the bladder from the temperature measured at the location of the supply pipe that supplies the heating medium inside the bladder or the exhaust pipe that discharges the heating medium from the bladder. However, the temperature outside the bladder does not represent the temperature at the boundary between the tire and the bladder. Particularly when steam or gas is used as the heating medium, it is impossible to know the temperature at the boundary between the tire and the bladder even if the temperature is measured with a pipe connected to the bladder. Thus, this known method does not allow accurate estimation of the temperature inside the tire;
There is a drawback that vulcanization cannot be precisely controlled.

Furthermore, in the above-mentioned U.S. Patent No. 4,371,483, the vulcanization state of the tire shoulder is determined by calculation using a finite element method using a finite number of rules or procedures. It is necessary to calculate many formulas containing many coefficients for each of many types of tires, making the calculation work very tedious and time-consuming. would require a large computer, and the cost would be extremely high.

Furthermore, since the minimum vulcanization point is not always located at the tire shoulder, this method is applicable only to the vulcanization control of limited types of tires.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a method by which the internal temperature of rubber or plastic during vulcanization can be determined accurately and reliably.

Another object of the present invention is to prevent over-vulcanization as well as under-vulcanization, without being affected by various variables such as differences in green tire structure and tire type, mold temperature, bladder temperature and pressure variations. The present invention aims to provide a method that can effectively eliminate vulcanization and accurately control tire vulcanization.

(Means and effects for solving the problems) The temperature measuring method of the present invention includes a mode unit that heats a rubber or plastic object and defines its outer shape, a bladder that heats the object and presses it against a mold unit, and In measuring the temperature of at least one point inside an object to be vulcanized by a vulcanizer comprising a bladder unit having a centerbost assembly, a bladder unit disposed at or near the interface between the mold unit and the object. a temperature measuring step of determining a first temperature with a first temperature sensor; a temperature measuring step of determining a second temperature with a second temperature sensor disposed in a center post assembly of the bladder unit; The method is characterized by comprising the step of calculating the temperature of a point inside the object based on the second measured temperature.

Further, the tire vulcanization control method of the present invention controls tire vulcanization by controlling the supply of heat to a tire vulcanizer including a mold unit and a bladder unit having a bladder and a center post assembly. a step of measuring a first temperature at at least one point at or near the boundary between the mold unit and the tire with a first temperature sensor during tire vulcanization; a step of measuring a second temperature in the post assembly during tire vulcanization; a step of calculating a temperature distribution inside the tire from the first and second temperatures; and a step of calculating a degree of vulcanization distribution inside the tire from the temperature distribution. A step of estimating the degree of vulcanization, a step of detecting the minimum degree of vulcanization from the degree of vulcanization distribution inside the tire, and a step of determining the timing to stop supplying heat to the vulcanizer according to this minimum degree of vulcanization. It is characterized by having the following.

According to the method of the present invention, the temperature at the boundary between the tire and the bladder can be measured from the temperature measured by the second temperature sensor provided in the center post assembly of the bladder unit, or the temperature sensor can be installed inside the tire. The temperature inside the tire can be determined accurately by calculation without having to insert the tire.

Therefore, the vulcanization situation inside the tire can be estimated very accurately, the tire can be cured to the best condition, and therefore tires with desired performance can be manufactured with high reproducibility.

(Example) FIG. 1 shows an example of an apparatus for implementing the tire vulcanization control method according to the present invention. This device consists of a control unit 1, an input unit 2 including a keyboard, an input card, a display panel, etc. for manually inputting various data from the outside.
and a sensor unit 3. The sensor units 3 include a first temperature sensor unit 4 that measures the temperature at the boundary between the tire and the mold unit, a second temperature sensor unit 5 that measures the temperature of the center post assembly of the bladder unit, and a pressure inside the bladder. and a pressure sensor unit 6 for measuring the pressure.

FIG. 2 is a diagrammatic cross-sectional view showing the configuration of the vulcanizer. The vulcanizer comprises a mold unit 7 and a bladder unit 8 having a deformable bladder 8a. The mold unit 7 has upper and lower mold halves i7a and 7b. For heating the mold unit 7, upper and lower platens 9 and 10 are arranged above and below the upper and lower mold halves, respectively. These platens 9 and 10 have passages 9a and 1
0a, respectively, and the heating medium is configured to be circulated through these passages via the vibrator 11 as shown by the double-headed arrow in FIG. Bladder 8a is attached to upper and lower rings 12 and 13, and the upper ring is fixed to center post 14, which is movably supported by sleeve 15. Therefore, the bladder 8a can move according to the vertical movement of the center post 14. In the lower ring 13 there is a pipe 1 for circulating heating fluids such as steam, gas and hot water through the bladder 8a.
6 and 17 are connected.

The first temperature sensor unit 4 includes a plurality of temperature sensors 4a arranged at equal intervals along the shoulder part of the tire, a plurality of temperature sensors 4b arranged at equal intervals along the bead part,
It has a plurality of temperature sensors 4C arranged at equal intervals along the tread portion.

The second temperature sensor 5 includes one temperature sensor 5a for measuring the temperature of the heating medium inside the bladder 8a.

In the present invention, this temperature sensor 5a is attached to the center post assembly of the bladder unit 8, that is, the lower ring 13. The pressure sensor unit 6 also includes a pressure sensor 6a attached to the center post assembly.

FIG. 3 is a sectional view showing the detailed structure of the vulcanizer, and particularly clearly shows the method of attaching the temperature sensor 5a to the center post assembly. The upper ring 12 is fixed to the tip of the center post 14 so that it can move up and down together with the center post. The upper edge of the bladder 8a fits between the upper ring 12 and the upper clamp ring 18, and the lower edge of the bladder 8a fits between the lower ring 13 and the lower clamp ring 19.
It fits between the

The lower ring 13 is secured to a manifold block 20 to which a sleeve 21 and a bag cylinder 22 are mounted. The pipe 17 is communicated with the interior space of the bladder 8a through a passage 20a formed in the manifold block 20. The temperature sensor 5a is a hole 21 formed in the sleeve 21.
a and the passage 20b formed in the manifold block 20.
Pass it through. Moreover, the pressure sensor 6a is also attached in the same manner.

Upper mold half 7a and upper platen 9 are connected to upper dome 23a, and lower dome 23b is attached to base 24 to which lower mold half 7b and lower platen 10 are also secured.

FIG. 4 shows in more detail the configuration in which the temperature sensor 5a is attached to the center post assembly. A manifold block 20 is welded to the bag cylinder 22, and a sleeve 21 is welded to this block.

A hole 21a is formed in the sleeve 21, and a bolt 25 is inserted into this hole. This bolt 25 is threaded into the manifold block 20. A ring 26 is welded to the lower end of the manifold block 20, and a bolt 27 is screwed into this ring. A through hole 27a is formed in this bolt 27 and communicated with a hole 20b formed in the manifold block 20. A bolt 28 is screwed onto the tip of the bolt 27 via a sealing ring 29. Temperature sensor 5a is POL)25.
It can be rigidly and airtightly attached to the center post of the bladder unit from the outside through the through holes drilled in holes 27 and 28 and the hole drilled in the manifold block 20, and in this case, there is no need to significantly change the existing bladder unit. do not have. Further, the temperature sensor 5a can be easily replaced without disassembling the bladder unit, and therefore its maintenance becomes very easy.

After placing the green tire 30 to be vulcanized into the vulcanizer, the upper and lower mold halves 7a and 7b are closed and the platen 9
A heating medium is passed through the passages 9a and 10a of 10 to heat the tire 30 from the outside. At the same time, a heating medium is circulated through the interior space of the bladder 8a via the pipes 16 and 17 to expand the bladder toward the mold unit 7 and heat the tire 30 from inside. When the bladder 8a expands, the tire 30 is pressed against the inner wall of the mold unit 7, thereby defining the outer shape of the tire.

In this embodiment, the temperature at the boundary between the tire 30 and the mold unit 7 and the temperature at the center post assembly of the bladder unit 8 are measured by the first and second temperature sensor units 4 and 5 during vulcanization. At the same time, the pressure sensor unit 6 measures the internal pressure of the bladder 8a. Signals C, , C2 and C3 representative of the temperature and pressure measured by these temperature sensor unit 4.5 and pressure sensor unit 6 are supplied to the control unit 1.

As shown in FIG. 1, the control unit 1 includes a CPU (central processing unit) 31 and a ROM (read only memory) 32.
, a RAM (random access memory) 33, an A/D converter 34, and an I10 port 35. C.P.
U31 inputs necessary data from I10 port 35 according to the program stored in ROM32, and
While exchanging data between the PU 31 and the RAM 33, various arithmetic operations are performed to derive various signals for controlling tire vulcanization. The signal thus determined is supplied to the I10 port 35.

Further, the A/D converter 34 converts the analog signal supplied to the I10 port 35 into a digital signal under instructions from the CPU 31. The ROM 32 stores operational programs necessary for the CPU 31, and the RAM 33 stores calculation programs and data in the form of a map.

Various initial data are input to the control unit 1 by a data input unit 2. That is, gauge data representing the thickness of the tire 30 and the bladder 8a, thermal diffusion coefficient data, and initial temperature data are input to the control unit 1 via the input unit 2.

The control unit 1 calculates the temperature distribution inside the tire 30 at predetermined time intervals and determines the minimum vulcanization point using a method described later. When a predetermined vulcanization is achieved, the control unit 1 supplies a control signal C4 to the vulcanization stop unit 36. Further, when the control unit 1 detects some kind of abnormality, it supplies a signal C5 to the alarm unit 37 to generate an alarm.

Next, a method for determining the temperature distribution inside the tire and the minimum vulcanization point will be explained.

FIG. 5 is a flowchart illustrating the sequential steps of such a method. Before actually performing vulcanization, step P,
As shown, data necessary for calculation and control is input to the control unit 1 through the input unit 2. That is,
The thickness and thermal diffusion coefficient of the tire, bladder and membrane layer and the initial temperature of the tire are entered as initial data. Furthermore, the identification data of the real-time control mode and the predictive control mode are read into the control unit)1. The temperature and pressure are actually measured from the start of vulcanization, and the elapsed time is measured.

In step P2, the tire is heated and vulcanized in real-time control mode. That is, the heating medium is placed between the platens 9 and 1.
0 to the passages 9a, 10a of the mold unit 7, and circulate heating fluids such as steam and gas under pressure through the bladder 8a to heat the tire 30 from inside and outside and press the tire against the inner wall of the mold unit 7. do.

During vulcanization, the temperature at the boundary between the mold unit 7 and the tire 30 and the temperature at the center post assembly of the bladder unit 8 are actually measured and input manually to the control unit 1 at every unit time interval Δθ. This unit time interval Δθ can be arbitrarily selected depending on the accuracy of control. In this example, tire 30
A temperature sensor 4a measures the temperature of the shoulder, bead, and tread portions of the vehicle.

Measured by 4b and 4C.

In step P3, the temperature at a point inside the tire 30 is determined by calculation, and the temperature distribution inside the tire at the shoulder, bead, and tread portions is determined at the starting instant of each time interval Δθ. Hereinafter, a method for determining the temperature distribution in the shoulder portion will be explained.

In this example, the temperature at the boundary between the mold unit 7 and the tire 30 is measured by temperature sensors 4a and 4b placed at this boundary position.
, 4c. As a result of various experiments, the present inventor has confirmed that it is extremely difficult to accurately measure the true temperature at this boundary.

FIG. 6 is a graph showing variations in temperature measured when temperature sensors are placed at various positions. Place the temperature sensor at a distance of 0.5 mm from the inner surface of the mold.
Curve A1 in FIG. 6 shows the temperature change when the mold is retracted inward by n+m and placed in the mold. In FIG. 6, temperature T>1 is the initial mold temperature, TT is the initial tire temperature, t
C indicates the time when the mold was brought into contact with the tire.

On the other hand, a curve Aa shows the temperature change when the temperature sensor is placed in the mold so that its temperature sensing tip is aligned with the inner surface of the mold. Further, curve A3 shows the temperature change when the temperature sensor is attached to the tire so that its sensing tip is aligned with the inner wall surface of the mold. Further, curve A,
1 shows the temperature change when the temperature sensor is attached to the tire with its temperature sensing tip retracted 0.5 mm from the tire surface. Furthermore, in Figure 6, the true temperature change (estimated) at the boundary between the tire and the mold is shown.
is also shown by a dashed curve A. Generally, when a temperature sensor is attached to the mold side, the measured temperature will be higher than the true temperature.
It can be seen that when loaded into the tire, the temperature becomes lower than the true temperature. In any case, it is practically impossible to actually measure the true temperature at the boundary between the mold and the tire. Therefore, in this example, a membrane layer is introduced between the mold and the tire.

For the same reason, a membrane layer is also introduced between the temperature sensor 5a and the bladder 8a.

FIG. 7 is a diagram showing a heat transfer model that takes into account the membrane layer introduced as described above. That is, temperature sensor 4
A first membrane layer B1 is introduced between the tire 30 and the tire 30, and a second membrane layer B2 is introduced between the bladder 8a and the temperature sensor 5a. The thickness of the first membrane layer B1 is determined by the material of the mold unit 7, the type and sensitivity of the temperature sensor 4a, and the distance between the inner wall surface of the mold and the temperature sensing tip of the temperature sensor 4a. Further, the thickness of the second boundary film layer B2 is determined by the type, sensitivity, and position of the temperature sensor 5a, the state of the heated fluid, that is, the material, the degree of stirring, and the like. The thicknesses of such first and second membrane layers B and B2 can be determined experimentally in advance.

Next, in step P3, the temperature distribution inside the tire 30 is calculated and calculated based on thermal diffusion theory in consideration of the following elements a) to e).

Element a) Gauge Data The gauge, ie, the thickness, of the tire 30 and bladder 8a is determined by actual measurement or calculation. In addition, the gauges of the first and second film layers B1 and B2 are determined by the material of the mold, the type, sensitivity and position of the temperature sensors 4a and 5a, the type of heating fluid such as steam, gas, water, etc., supply time, and mixing. It can be determined by various factors such as the supply conditions of the heating fluid, such as the ratio.

In reality, the gauges of the membrane layers B, B2 are determined experimentally. These gauge data are input to the control unit 1 using the input unit 2.

Element b) Thermal Diffusion Coefficient Data As will be described later, the temperature inside the tire 30 is estimated by the finite difference method, but since the tire has a composite structure made up of multiple different materials, the finite difference method is used as is. Temperature distribution cannot be determined by the method. Therefore, in this example, an average thermal diffusion coefficient is introduced. In order to obtain this average thermal diffusion coefficient by calculation, the thermal diffusion coefficients of various materials constituting the tire are inputted to the control unit 1 by the operator 2. Now α1 to α5 and G+”G
s as a first film layer 61, a tire tread and a carcass;
Assuming that the thermal diffusivity and thickness of the bladder 8a and the second membrane layer B2 are respectively, the average thermal diffusivity can be calculated by the following equation.

Further, the thermal diffusion coefficient α1 can be calculated using the following equation.

K+ here, K1...Thermal conductivity CP□・・・Specific heat ρ1...density It is.

Element C) Initial Temperature Data Before performing vulcanization, the surface temperatures of the bladder 8a and the green tire 30 are measured using a non-contact infrared thermometer or a contact thermometer, and then sent to the control unit 1 via the input unit 2. Enter.

Element d) Measurement Data The temperature at the boundary between the mold unit 7 and the tire 30 and the temperature at the center post assembly of the bladder unit 8 are measured by temperature sensors 4a and 5a, and signals CI and C2 representing the measured temperatures are sent to the control unit. supply

In this example, a signal C3 representing the bladder internal pressure measured by the pressure sensor 6a is also supplied to the control unit)1.

Element e> Estimation of Tire Internal Temperature Based on the above-mentioned data input to the control unit 1, the control unit estimates the temperature distribution inside the tire 30. This operation can be performed by the finite element method (FBM) or the finite difference method (FDM).

The finite difference method will be explained below. In order to reduce the calculation time, we consider a one-dimensional model as shown in Figure 7,
The temperature at a finite number of points P InF3-m- inside the tire 30 is calculated. As shown in FIG. 7, these points are spaced apart from each other by a constant distance ΔX. In this example, the distance between the temperature sensors 4a and 5a is equally divided into 10 sections, and the temperature at the boundary of these sections is calculated at each starting instant of the unit time interval Δθ. This unit time interval Δθ is 0.
It can be set arbitrarily within the range of 5 to 10.0 seconds. The temperature t (X, θ+Δθ) at a point Pt, which is a distance X away from the first point P0, when a unit time interval Δθ has elapsed from time θ can be calculated using the following difference formula.

t(x, θ+Δθ) = t(x, θ) + C,
(t(X-ΔX, θ)-2t(x, θ)+t(X+
ΔX, θ)) where τ is the average thermal diffusivity.

In performing the above calculation, the initial temperatures of the points inside the tire and the points inside the first membrane layer B are set to the initial tire temperature, and the initial temperatures of the points inside the bladder and the second membrane layer B2 are set to the initial temperature of the points inside the tire and the points inside the first membrane layer B2. is set to the initial bladder temperature. As described above, these initial tire temperatures and initial bladder temperatures are manually input to the control unit 1 by the input unit 2 in advance.

In this way, the temperature distribution inside the tire 30 can be estimated at the starting instant of each unit time interval Δθ.

As is well known, the crosslinking reaction of rubber during vulcanization is an exothermic reaction, and the generated heat cannot be ignored in order to improve the accuracy of temperature estimation. The influence of this heat cannot be ignored, especially when the rubber is thin. However, general F
In DM, the heat generated cannot be taken into account in calculations. In this example, in order to eliminate the influence of heat generation, the value of the average thermal diffusivity coefficient is changed as vulcanization progresses. That is, by increasing the value of the average thermal diffusivity i as the degree of vulcanization V increases, it is possible to estimate a temperature distribution that more accurately represents the actual temperature distribution. In this example, the value of the average thermal diffusion coefficient 5 is changed according to the following equation.

2 = 1゜ (1 + cff)'') where 7xo = initial average thermal diffusion coefficient C, n: constant determined by the composition of the rubber V: calculated minimum vulcanization degree The value of d in the above-mentioned difference equation is calculated according to the above formula. By changing the temperature distribution, the temperature distribution inside the tire can be determined more accurately.

The effect of heat generated by the crosslinking reaction can be compensated for by various methods other than those described above.

For example, the change Δ in the minimum degree of vulcanization from the degree of vulcanization determined by calculation
Determine V, then calculate the reaction heat amount ΔQ from this ΔV, calculate the temperature rise Δt due to the reaction from this heat amount ΔQ, and correct the calculated temperature distribution by linear approximation using this Δt. can.

Moreover, the estimation of the temperature distribution inside the tire can also be performed by FEM instead of FDM, and similar results can be obtained in this case as well. However, since FBM requires more calculation steps than FDM, FDM is more desirable.

In step P, the minimum temperature inside the tire is compared with a predetermined limit temperature, for example 100° C., and when the minimum temperature exceeds the limit temperature, the vulcanization degree distribution is calculated from the temperature distribution in step P5. That is, the degree of vulcanization distribution is not determined while the temperature is low, but is determined after the temperature exceeds the limit temperature, thereby reducing the number of required calculation steps. As shown in Fig. 7, there are seven measurement points P2 to P2 in the tire gauge at the tire shoulder.
P8 is set, and the values of the degree of vulcanization at these points are calculated from the estimated temperatures at these points. That is, at the beginning of each unit time interval Δθ, the equivalent degree of vulcanization V at these points is calculated using the following Arrhenius equation.

Here, E: activation energy R: gas constant To: standard temperature T: reaction temperature θ: time. In this way, a vulcanization degree distribution as shown in FIG. 8 is obtained at the starting instant of each unit time interval Δθ. 8th
In the figure, the horizontal axis represents the position in the thickness direction of the tire, and the vertical axis represents the degree of vulcanization V. At the starting instant θ1 of the degree of vulcanization calculation step P5, the first degree of vulcanization distribution Mn
+ is obtained, and after the unit time interval Δθ has elapsed, the next vulcanization degree distribution M at time θ2. 2 is obtained. In this way, each time θ1° θ2. At θ3---, vulcanization degree distribution M
. l + M h 2 +! An3-1 will be obtained.

Next, in step P6, the minimum degree of vulcanization is calculated using the least squares method. How to determine this minimum degree of vulcanization will be explained next. Generally, the point where the minimum degree of vulcanization appears does not coincide with the temperature measurement point, so the minimum value among the degrees of vulcanization at each measurement point P2 to P8 cannot be used as the minimum degree of vulcanization. As shown in FIG. 8, the point at which the minimum degree of vulcanization appears is not constant, and shifts toward the mold side as time passes.

The minimum degree of vulcanization V T l in each degree of vulcanization distribution is calculated as follows using the method of least squares. In this example, it is assumed that the vulcanization degree distribution is expressed by the following quadratic function.

V=AX”+BX+C Coefficients A, B, and C are determined so that the error d1 from the quadratic curve of the degree of vulcanization value at each point is determined. Next, determine the minimum degree of vulcanization V t t and the position of that point. Find XTI as follows.

vTt・A(-8/2A)24 B(-8/2A)+
CXtt=-8/2A Of course, the value of the minimum degree of vulcanization can also be determined by the method of least squares using a function higher than a quadratic function.

As described above, the minimum degree of vulcanization is determined from the degree of vulcanization distribution at the start of each unit time interval Δθ. In this example, as mentioned above, the temperature is measured at multiple locations on the tire at the same time, so multiple minimum degrees of vulcanization are determined at each unit time interval Δθ. Select as the minimum degree of vulcanization inside the tire.

In step P7, it is determined at a predetermined timing θ7 whether the minimum degree of vulcanization v7 determined as described above is within a predetermined range.

That is, the minimum degree of vulcanization Vr is the maximum and minimum degree of vulcanization VM
Compare with AX and VMIN. At the same time, it is determined whether a predetermined pressure has been applied to the bladder for a predetermined period θa. Here v, AX > v, > v14. .

When it is confirmed that is satisfied and that a predetermined pressure is applied in the bladder for a predetermined period θ, the real-time mode is switched to the prediction mode in step P.

On the other hand, when V ) IAX > VT > Vll [11 is not satisfied, vulcanization control is performed in real-time mode only for a predetermined period as shown in step P3 in FIG.

According to the present invention, vulcanization can be stopped when the minimum degree of vulcanization reaches a predetermined value. However, in this example, in order to control the vulcanization state more accurately, a prediction mode is introduced in which the progress of vulcanization is predicted after the supply of heating medium to the vulcanizer is stopped. In other words, even after the supply of the pressurized heating fluid to the bladder is stopped at time θ1, the internal temperature of the tire is maintained at a high temperature as shown in FIG. 9, so vulcanization continues as shown in FIG. It will proceed further. In FIG. 9, the temperature at the minimum vulcanization point is shown, and the time at which the real time mode is switched to the prediction mode in normal vulcanization is shown as θ9. In this prediction mode,
The minimum degree of vulcanization is continuously predicted as shown in step Plo.

In the prediction mode, the minimum degree of vulcanization vk that will be reached after a time tk has elapsed since the supply of the heating fluid is stopped is determined by the minimum degree of vulcanization v1 at time θ, and n than this time θ. Time θl− when the previous sampling was performed
Predicted by linear extrapolation using the minimum degree of vulcanization vi-n at h. This linear extrapolation can be performed using the following equation.

k Vk-(Vt -Vt-h) + Vt here t,
= n·Δθ.

The predicted minimum degree of vulcanization vk is the desired degree of vulcanization V.

When reaching the temperature, the heating is stopped at time θ1 as indicated by step P1□. Next, in step P13, the vulcanization process is ended, and the prediction mode is switched to the real-time mode again. When the control unit )l detects the vulcanization stop command, it supplies a vulcanization stop signal C4 to the vulcanization stop unit 36. Thereby, the vulcanization stop unit 36 performs the cooling and removal process of the tire from the vulcanizer as usual. FIG. 9 shows changes in the pressure inside the bladder and changes in the temperature of the heating fluid supplied to the bladder. If an abnormality is detected, the real-time mode is forcibly selected and vulcanization is continued for a predetermined period of time.

As shown by curve A in FIG. 11, when the minimum degree of vulcanization exceeds the upper limit C1 at a predetermined time θ, an alarm is generated and vulcanization is stopped at a preset timing. In such a case, the real-time mode is not switched to the prediction mode.

As shown by curve B, when the minimum degree of vulcanization is between the upper and lower limit values C1 and C2 at a predetermined timing θ, an alarm is generated and control is continued in the prediction mode.

As shown by curve C, when the minimum degree of vulcanization is smaller than the lower limit C3 at the predetermined vulcanization stop time θ0, an alarm is generated and vulcanization is ended while remaining in the real-time mode.

Further, as shown by the curved line, if the minimum degree of vulcanization exceeds the lower limit value C2 at time θ0 but does not exceed the lower limit value C4, an alarm is generated and vulcanization is continued in the prediction mode. In FIG. 11, normal vulcanization operation is shown by curve E.

By introducing the above-mentioned prediction mode, vulcanization can be controlled with extremely high accuracy, under-vulcanization and over-vulcanization can be effectively prevented, and therefore vulcanization time can be shortened. If a prediction mode is not introduced, there is a risk that an error of V in the degree of vulcanization will occur as shown in FIG.

As described above, according to the vulcanization control method of the present invention, the temperature distribution inside the tire is estimated from the temperature at the boundary between the tire and the mold and the temperature of the center post assembly of the bladder unit, and from this estimated temperature distribution. The vulcanization degree distribution is calculated, and the minimum vulcanization degree is determined from this vulcanization degree distribution.

Therefore, even if the minimum vulcanization point moves in the direction of the tire gauge, the minimum degree of vulcanization can be accurately detected, and therefore vulcanization can be controlled accurately and with high reliability.

Furthermore, in this example, after the minimum degree of vulcanization reaches a predetermined value, the real-time mode is switched to the prediction mode, and the value of the minimum degree of vulcanization that will be reached after the supply of heating fluid is stopped is predicted. I try to do that.

By introducing such a predictive mode, the progress of vulcanization during cooling and removal of the tire from the mold can also be taken into account, thus allowing for more precise vulcanization control and effectively eliminating over-vulcanization. It can be prevented.

Therefore, according to the present invention, the vulcanization time can be minimized, the amount of heating medium can be significantly reduced, and the properties of the vulcanized tire can be accurately and reliably achieved as desired. be able to.

Furthermore, a temperature sensor 5 that measures the temperature inside the bladder 8a
Since the temperature sensor is attached to the center post assembly of the bladder unit, the temperature at the boundary between the tire and the bladder can be accurately estimated, and the temperature sensor is less likely to be damaged and maintenance is improved.

As a result of various experiments, the present inventors have found that when performing gas vulcanization using gas or steam as the heating fluid for the bladder unit, a temperature difference occurs not only in the circumferential direction of the tire but also in the axial direction. I confirmed that. In particular, a temperature difference of about 10° C. may appear in the axial direction of the tire. Therefore, the minimum vulcanization point will generally appear in the lower portion of the tire. In this case, the vulcanization time generally tends to be long, and the vulcanization process may not be sufficiently improved. In a preferred embodiment of the vulcanization control method according to the present invention, the above-mentioned problems can be easily solved.

FIG. 12 is a schematic cross-sectional view showing another example of the vulcanizer.

In this example, the same parts as those shown in FIG. 2 are denoted by the same reference numerals as in FIG. In this example, in order to reduce the temperature difference inside the bladder 8a, heating fluid is injected into the inside of the bladder from four jet nozzles 45. These nozzles 45 are mounted on a lower bladder ring assembly 46 spaced apart by 90 degrees from each other in the circumferential direction. As shown in FIG. 13, an injection nozzle 45 having a central hole 45a is threaded onto a mount 47 such that a passageway 47a formed therein communicates with a passageway 46a formed in a lower bladder ring assembly 46. weld to the assembly.

With this configuration, a heated fluid such as steam or gas is injected from the nozzle 45 over a diffusion angle β of approximately 30 to 45 degrees, and therefore the fluid is sufficiently stirred within the bladder. The temperature becomes uniform.

FIG. 14 is a graph showing the temperature difference between the upper part H and the lower part G of the bladder 8a. Curve A shows the conventional method;
The temperature difference in this case is greater than 10°C. On the other hand, in the present invention, as shown by curve B, the temperature difference can be significantly reduced.

FIG. 15 is a graph showing temperature changes in the tire bead and the center post assembly of the bladder unit in the method of the present invention. It can be seen that the difference in temperature between these parts is extremely small. Further, FIG. 16 shows the temperature difference between these parts in the conventional method, and a large temperature difference appears. The above-mentioned injection nozzle 4
By using No. 5, it was possible to significantly reduce the difference between the temperature of the tread and shoulder portions of the tire and the temperature of the center post assembly of the bladder unit.

Next, several examples of the vulcanization control method of the present invention when vulcanizing a PSR175R14 tire will be described together with comparative examples. In these examples, conditions other than vulcanization were the same. In addition, as for the quality performance of the tire, the durability performance of the tire belt and carcass was measured using an ordinary drum testing device. After rotating the tire at a predetermined speed and under a predetermined load for a predetermined period of time, whether or not delamination occurs at the edges of the belt and carcass, and if so, to what extent. Inspected. The results of this test are shown in the following table (■).

In Table I, the performance of tires manufactured by known methods is normalized to 100.

Table 2 As is clear from Table 2 above, according to the present invention, tires can be manufactured with high reproducibility, and the performance of the manufactured tires is extremely excellent.

The following table (1) shows some examples of the vulcanization control method according to the present invention, together with comparative examples using the conventional vulcanization control method.

In the above-mentioned Table (2), examples No. 11 to 30 are tires manufactured by the method of the present invention, and examples No. 4 to 12 are tires manufactured by the conventional method.

The temperature measurement points in Table H are as shown in FIG. Here, point A is the boundary between the mold and the tire, and point C is within the tire surface. Therefore, if the temperature is measured at point C, a small hole will remain on the tire surface, but such a small hole can be ignored in the tire.

According to the present invention, the temperature on the bladder side is measured at the center post position H of the bladder unit. Further, point M is inside the introduction pipe or the outlet pipe connected to the bladder unit. In order to obtain good tire performance, the temperature fluctuations on the tread surface and the minimum vulcanization point must be less than 1°C above, and the temperature difference between the plies must be less than 2°C above.
It needs to be smaller than ℃. Further, the variation in the minimum degree of vulcanization must be within ±0.5 when the ideal degree of vulcanization is 10.0. The vulcanization time is expressed as a percentage deviation from the ideal vulcanization time. This difference in vulcanization time must be within ±2.0%. When some of the above-mentioned parameters deviate from their respective limits, the accuracy and reliability of the control will deteriorate. As can be seen from the examples of k4.5 and 6, if a membrane layer is not introduced,
It is not possible to accurately estimate the temperature distribution inside the tire.
Therefore, a large error occurs in the degree of vulcanization. Also,
If the finite element method (FEM) is used as in example No. 11, temperature fluctuations can be suppressed to a small value, but the number of calculation steps becomes extremely large and it cannot be applied to actual manufacturing.

The present invention is not limited to the embodiments described above, but can be modified and modified in many ways.

In the above-described embodiment, the temperature at multiple points in the shoulder, bead, and tread portions of the tire was actually measured by the temperature sensors 4a, 4b, and 4C, but in the present invention, the temperature may be measured at at least one point. For example, it is sufficient to simply measure the temperature of the shoulder portion or the temperature of the shoulder portion and bead portion.

Further, in the embodiment described above, the second temperature sensor unit 5 only includes one temperature sensor disposed on the center post assembly, but a plurality of temperature sensors may be attached to the center post assembly. Good too.

Further, in the above embodiment, nine points P1 to P are allocated between the temperature sensors, but the number of points can be arbitrarily determined depending on the accuracy to be achieved and the calculation to be performed.

Further, in the above embodiment, the minimum degree of vulcanization vk after stopping the supply of heat to the vulcanizer was predicted by the linear approximation method, but it can also be predicted by other methods.

(Effects of the Invention) According to the temperature measuring method of the present invention described above, the temperature inside the tire can be determined from the temperature measured at the boundary between the mold unit and the tire and the temperature measured at the centerbost assembly of the bladder unit. is estimated by calculation, so the temperature inside the tire can be measured accurately and reliably. Furthermore, since the temperature sensor is attached to the centerbost assembly of the bladder unit, the temperature sensor can be effectively protected from damage, and maintenance is also very easy, resulting in cost reduction.

Furthermore, according to the tire vulcanization control method of the present invention, after determining the temperature distribution inside the tire as described above, the vulcanization degree distribution inside the tire is determined from this, and then the minimum degree of vulcanization is determined from this, and this minimum Since the supply of heat to the vulcanizer is controlled based on the degree of vulcanization, even if the minimum vulcanization point moves inside the tire, the supply of heat can always be stopped at the correct timing. It is possible to manufacture tires with high reliability with high performance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an apparatus for carrying out the tire vulcanization control method according to the present invention, FIG. 2 is a diagrammatic sectional view showing the configuration of a vulcanizer, and FIG. 3 is a detailed diagram of the same. 4 is a sectional view showing the configuration of the centerbost assembly of the bladder unit. FIG. 5 is a flowchart showing the sequential steps of an embodiment of the tire vulcanization control method of the present invention. The figure is a graph showing temperature fluctuations when temperature sensors are placed at various locations, Figure 7 is a graph showing the thermal diffusion model introduced by the present invention, and Figure 8 is a graph showing changes in the degree of vulcanization distribution inside the tire. Figure 9 is a graph showing changes in minimum temperature; Figure 10 is a graph showing changes in minimum degree of vulcanization; Figure 11 is a graph showing changes in minimum degree of vulcanization under various abnormal conditions; Figure 12 is a cross-sectional view showing the configuration of another embodiment of the vulcanizer, Figure 13 is a cross-sectional view showing the configuration of the injection nozzle, Figure 14 is a graph showing the temperature difference inside the bladder, and Figure 15 is a graph showing the temperature difference inside the bladder. FIG. 16 is a graph showing the temperature difference inside the bladder in the method of the present invention, FIG. 16 is a graph showing the temperature difference inside the bladder in the conventional method, and FIG. 17 is a diagram showing various temperature measurement points. ■... Control unit 2... Crab knit 3.
...Sensor unit 4...First temperature sensor unit 5...Second temperature sensor unit 6...Pressure sensor unit 4a, 4b, 4c...Temperature sensor 5c...Temperature sensor 7...Mold Unit death... Bladder unit 8a... Bladder patent applicant Co., Ltd.
Bridgestone Fig. 1 Fig. 4 Fig. 5 Fig. 6 Ruff "Lag Σ" Fig. 9 Fig. 11 and V Snout Yuma θ Fig. 12 Fig. 13 Fig. 7,'' 46σ Fig. 14 O Yusen 9? Mu, Kibatsu Hidada's Power 3 Mui Husband 4 Son-in-law

Claims (1)

[Claims] 1. A mold unit that heats a rubber or plastic object and defines its outer shape, and a bladder unit that heats the object and presses the object against the mold unit and has a center post assembly. In measuring the temperature at at least one point inside the object to be vulcanized by the vulcanizer, the first temperature is determined by a first temperature sensor disposed at or near the interface between the mold unit and the object. a temperature measuring step; a temperature measuring step of determining a second temperature using a second temperature sensor disposed in a center post assembly of the bladder unit; and determining a point inside the object based on the first and second measured temperatures. A method for measuring the internal temperature of a vulcanized object, the method comprising: calculating the temperature of a vulcanized object. 2. In the calculation step, the temperature at a plurality of points along a straight line passing through the object is derived by calculation to determine the temperature distribution inside the object, and the first temperature sensor is located between the first temperature sensor and the object.
A second capillary layer is introduced between the second temperature sensor and the bladder, and the plurality of points are 2. The temperature measuring method according to claim 1, wherein the temperature of the temperature is determined by calculation. 3. The calculating step includes calculating an average thermal diffusivity from the thermal diffusivity and thickness of the object, the first and second membrane layers, and calculating the inside of the object by a finite element method using the average thermal diffusivity. 3. The temperature measuring method according to claim 2, further comprising the step of calculating and determining temperatures at a plurality of points. 4. In controlling tire vulcanization by controlling the supply of heat to a tire vulcanizer comprising a mold unit and a bladder unit having a bladder and a center post assembly, the first temperature sensor measuring a first temperature at at least one point at or near the boundary between the mold unit and the tire during tire vulcanization; and measuring a second temperature at the center post assembly of the bladder unit using a second temperature sensor; a step of measuring during vulcanization, a step of calculating a temperature distribution inside the tire from the first and second temperatures, a step of estimating a degree of vulcanization distribution inside the tire from the temperature distribution, and a step of vulcanizing the inside of the tire. A tire vulcanization method comprising the steps of: detecting the minimum degree of vulcanization from the sulfurity distribution; and determining the timing to stop supplying heat to the vulcanizer according to the minimum degree of vulcanization. Sulfur control method. 5. Cooling after switching the real-time control mode to the predictive control mode when the minimum degree of vulcanization falls within the range of the predetermined upper and lower limits of the degree of vulcanization, and stopping the supply of heat to the vulcanizer. predict the minimum degree of vulcanization that will be reached during the period and during which the tire will be removed from the vulcanizer, and when it is determined that this predicted minimum degree of vulcanization will reach the desired value, 5. The tire vulcanization control method according to claim 4, further comprising determining the timing at which the supply of heat is stopped.