JPS6013250A - Controlling method of rubber vulcanization process - Google Patents

Abstract

PURPOSE:To elevate the control accuracy of the vulcanization process by controlling the vulcanization process depending on the equivalent vulcanization time and vulcanization level at a set point inside rubber from a detection value obtained when the temperature at a plurality of points of a rubber surface changing with time during the vulcanization is detected at a specified time interval. CONSTITUTION:At the step 1, the temperature at a plurality of point on the surface of a rubber 10 varying with time is detected at DELTAt interval. At the step 2, the temperature detected at the step 1 is used as restricting condition to compute the temperature at the set point inside a rubber after DELTAt time by the solution of heat diffusion. Then, at the step 3, the arithmetic processing is performed on the equivalent vulcanization time toi and the vulcanization level x1 at the set reference temperature T0 based on Arrhenius' equation from the temperature computed at the step 2. At the step 4, the computed value toi is compared with the set values toc and xc to judge. At the step 5, a control signal is outputted to a vulcanizer based on the results of the judgement at the step 4 and thus, a higher control accuracy is achieved.

Description

[Detailed description of the invention] The present invention relates to a method of controlling a rubber vulcanization process.

In controlling the vulcanization reaction of rubber according to its degree of vulcanization, a vulcanization totalizer using the Arrhenius equation has conventionally been employed to detect the degree of vulcanization. The principle of this vulcanization totalizer is as follows.

(a) Directly detect the rubber temperature during vulcanization using a thermocouple.

(mouth) Based on the Arrhenius formula (formula (1) described later),
The actual vulcanization time is converted into an equivalent vulcanization time to at a preset reference temperature TO and output.

(c) A control signal is output to the vulcanizer when the equivalent vulcanization time to reaches a set value.

B) Repeat steps (a) to (c) above at regular intervals during vulcanization.

k: reaction rate constant A: Frequency factor E: Activation energy R: gas constant T: reaction temperature If the reaction rate constant at reaction temperature To is ko, then -”L- kO=　A　−e　RT.

Therefore, the ratio of reaction rate constants is /ko.

Therefore, if equation (2) is integrated over the reaction time t at T, equation (3) is obtained.

The value to obtained by this formula is given at a certain temperature T
It represents how many times the amount of reaction occurs per unit time at o (hereinafter referred to as reference temperature), and is generally called equivalent vulcanization time.

In short, the conventional method described above does not measure temperature (
This method provides information only about the inside of the rubber and controls the vulcanizer using this information, and when applied to an actual vulcanization process, it has the following problems.

(a) The thermocouple for temperature detection remains inside the product, or even if it is pulled out, a hole remains in the part where it is pulled out, so the types of products to which it can be applied are limited.

(c) Attach a temperature detection terminal to the mold or heating plate,
It may be possible to control the vulcanization process based on the degree of vulcanization on the rubber surface, but the correspondence between the degree of vulcanization between the rubber surface and the inside of the rubber must be determined empirically. It is not possible to strictly control the process.

(C) In multi-cavity molds, a method is used in which a dummy cavity is provided to check the degree of vulcanization inside the rubber, but this increases material loss and lowers productivity.

In view of this, the present invention measures the temperature of the rubber surface using a temperature detection terminal attached to a mold, etc., calculates the temperature change inside the rubber based on the measured value, and calculates the calculated value. The purpose is to increase the degree of vulcanization based on the Arrhenius formula, and to control the rubber vulcanization process with high precision without damaging the product or creating a dummy cavity. be.

The present invention will be explained in detail below.

The method of controlling the rubber vulcanization process according to the present invention comprises j steps 5 as shown in FIG.

−Surface temperature detection step: This step measures the rubber surface temperature during vulcanization at predetermined time intervals Δ.
This step is to detect each time. This temperature detection is carried out by attaching a plurality of temperature detection terminals to the mold or heating plate of the vulcanizer. That is, during vulcanization, the temperature at multiple points on the rubber surface, which changes over time, is detected over time.

1. Internal temperature calculation step 2 - This step is a step of calculating the temperature at the set point inside the rubber after a time period of Δ using the temperature detected in step 1 as a constraint condition using a thermal diffusion solution method. As a method for solving thermal diffusion, a difference method or a modified version of the finite element method can be used.

To explain the case of using the difference method, as shown in Fig. 2, several nodes are set on the surface and inside of the rubber 10! The dimensions are determined under the conditions shown below.

a) The line connecting the nodes forms an acute or right triangle.

b) The line connecting the nodes becomes a rectangle or square.

C) The node is at the intersection of the concentric circles and the radial line.

The node 11a on the rubber surface is the temperature detection position by the temperature detection terminal, and in this step, the node 11a inside the rubber
The temperature of 1b is determined by calculation.

As shown in Figure 3, each node 1 , 1 +/ + 1 +
-2゜ i + J, the formula for the heat balance in the m-gonal element 12 surrounded by the perpendicular bisector of the line segment connecting n % Formula % TJ: Temperature at the n-th node at time t = PΔt Ql)'
Volume C per unit thickness of the polygon including the nth node: Specific heat γ: Specific gravity q(j): Average heat flux An passing through the (ji)th side of the polygon, (i-1): The area per unit thickness of the (j-i)th side of a polygon, and the above average heat flux q(j) when a side of a polygon is in contact with another polygon is given by the following equation (II): It becomes like this.

q (j) −λ (T(j)−T(n))/Ln,
(j − i ) (II) λ: Thermal conductivity T (temperature Lzl of one node j, (ji − i): Distance between nodes j and n Put in.

In the case of adiabatic conditions q=o (When giving the decoy surface heat flux q=qo (b) In the case of linear heat transfer conditions q-α (Too-T (b)) (V) α: Heat transfer coefficient, Tc-o ; Ambient fluid temperature Re, Qll)
~ Substitute equation (V) into equation (1) L' -c Tff y
=- By extracting 〈p p p on the right side, T(1) r T(2) +...
..., T(c) to p+I p+I p+] Δ after time T(]), T(2) ......, T
(b) In other words, the temperature at each node can be calculated.

-Calculation processing step 6- This step is a step of calculating the equivalent vulcanization time 1o(i) and the degree of vulcanization χ(i) at the set reference temperature To from the temperature calculated in step 2 based on the Arrhenius equation. It is.

That is, the calculated temperature of each node is taken in at intervals of Δt, and Δ
Based on the Arrhenius equation with Δ1o(i) equivalent to t, fi o T (i) is the temperature at the number of times of intake i, that is, at t (i).

Then, the integrated value of Δi (o) i, that is, the equivalent vulcanization time to(i) is calculated.

Next, the degree of vulcanization χ(
i).

Comparison and Judgment Step 4 - This step let, the equivalent vulcanization time fo (i) obtained in step 6 or the equivalent vulcanization time toe which requires the output of the side leg signal in which the degree of vulcanization χ (i) is set in advance, or This is a step of comparing and determining whether the degree of vulcanization χC has been reached. In other words, whether fo(i)≧toe or not,
It is determined whether χ(i)≧χC. If this determination is negative, the process returns to surface temperature detection step 1, and step 4 is repeated at predetermined time intervals Δt.

1. Output step 5 - This step is a step of outputting a control signal to the vulcanizer based on the determination result in step 4.

That is, to(i)≧toc or χ(i)≧χ
If it is C, a command signal to stop vulcanization or change the vulcanization temperature is output to the vulcanizer.

Next, a case will be described in which the control method according to the present invention is applied to an actual vulcanization process using a computer.

FIG. 7 shows a flowchart of a conbeater implementing the method of the present invention. First, in step S1, the shape and physical constants (thermal conductivity, specific heat, and specific gravity) of the rubber to be vulcanized are determined, and in step S2, a heat conduction matrix (MJ) is created and stored in the storage section of the converter. .

This thermal conduction matrix fMJ will be described later.

In step S3, it is determined whether or not to start, that is, whether or not the thermal conduction matrix (M) has been created and the measurement of the rubber surface temperature can be started. In the case of YES, the process advances to step S4, and the measurement end of the rubber surface temperature is taken in at intervals of Δt.

Next, in step S5, the heat flux qo on the comb surface is calculated, and in step s6, the heat conduction matrix (M) is rewritten so that this heat flux (Io) becomes a constraint condition.

In step S7, each element temperature is calculated.

1Δt (T) = fM) The equivalent vulcanization time 1o(i) Δt and the degree of vulcanization χ(i) are calculated from (T) in step S7 above.

In step S9, the degree of vulcanization χ(i) at the set point is output, and in step SIO, the degree of vulcanization χ(i) set in advance is output.

and the degree of vulcanization χ(i) output in step s9,
In other words, it is determined whether χ(i)≧χC, and if YES, the process proceeds to step S and outputs a control signal to the vulcanizing device.
If No, return to step S4.

Here, the procedure for creating the thermal conduction matrix (M) will be explained based on the flowchart of FIG.
In step S03, the nodal relationship is read, and in step S03, the physical constants (thermal conductivity, specific heat, and specific gravity) of the rubber to be vulcanized are read.Then, in step S04, the amount of change in temperature ΔT is calculated for each side of the element. Then, in step 505, this amount of change Δt is written in a matrix of size (number of nodes x number of nodes) to create a heat conduction matrix (IJ) (M).

Next, examples of the present invention will be described in comparison with comparative examples.

When vulcanizing the rubber product 15 shown in FIG. 3 in a press, a comparison was made between the case where the temperature at the center point inside the rubber was seamed by the method of the present invention and the case where the center point temperature was actually measured with a thermocouple.

The length of rubber products is / , 20 + nm, and the width W is! ;
0ran, height h is 72m, the physical constants are specific heat C is θg2C resistance, specific gravity γ is //2q/anchor, thermal conductivity λ is l
,,,! ; X/θ-4Ca standing A seedling.

The mode of element division is shown in FIG. 7, in which the rubber was divided into rectangular elements in cross section. In Figure 7, 1]Wl
Ha, l! 6 Mrl, height h] is 2 blood, and 16 is a set point (a node located at the center inside the rubber). The temperature of the mold was 730° C., and the interval Δt for measuring the surface temperature in the method of the present invention was 0.2 minutes. The results of the comparative test are shown in Figure 2.

Figure 2 shows the relationship between rubber temperature and elapsed time.
Line A is the actual measured value of the rubber surface temperature, line B is the calculated value of the temperature at the center point inside the rubber obtained by the method of the present invention, and line C is the actual measured value of the temperature at the center point inside the rubber. As shown in FIG. 2, it can be seen that the calculated value of the temperature at the center point inside the rubber according to the method of the present invention substantially coincides with the actually measured value.

In addition, in calculating the equivalent vulcanization temperature and degree of vulcanization based on the Arrhenius equation, in the above explanation, the activation energy is assumed to be constant during the entire vulcanization reaction process, and the equivalent vulcanization time is assumed to be a value proportional to the degree of vulcanization. However, the accuracy of 1jlJ can also be improved by treating activation energy and degree of vulcanization as a relationship between heating time at a reference temperature.

That is, a continuous function χ-f+(to) is calculated in advance from multiple sets of data regarding the heating time to during the period from the start of heating to the end of heating at the reference temperature and the degree of vulcanization χ at that time to.

Regarding the activation energy E, we measured the heating time to reach a certain degree of vulcanization at a temperature other than the reference temperature, and the activation energy at χ at multiple points (3 or more points) from the start of vulcanization to the end of vulcanization. E is calculated using the Arrhenius equation, and this E
Taking the heating time to corresponding to the calculated χ, this E and t
A continuous function E=f' 2 (to) is calculated from multiple sets of data regarding o.

As described above, according to the present invention, the temperature at multiple points on the rubber surface that changes over time during rubber vulcanization is detected at predetermined intervals, and the temperature at the set point inside the rubber is determined from the detected value. Since the rubber vulcanization process is controlled by adjusting the equivalent vulcanization time or degree of vulcanization, problems such as the formation of cavities due to the insertion of thermocouples into the rubber, which were conventional, are eliminated.
The rubber vulcanization process can be controlled with high precision without providing a dummy cavity. Furthermore, since the method of the present invention allows the vulcanization state of the rubber to be known over time, it is particularly effective when performing so-called step vulcanization, in which the vulcanization temperature is controlled according to the degree of vulcanization or the vulcanization time. be.

[Brief explanation of drawings]

Fig. 1 is a flow diagram showing the configuration of the method of the present invention, Figs. 2 and 3 are explanatory diagrams of element division in the difference method, and Fig. 7 is a flow diagram when the method of the present invention is implemented with a conopter. Fig. 5 is a flow diagram for creating a thermal conduction matrix, Fig. 6 is a perspective view showing the sample material in the example, Fig. 7 is an explanatory diagram showing the aspect of element division in the example, The figure is a graph showing changes in rubber temperature over time. 1-5...Step, 10...Rubber,
11a111b...Node, 12...Element, 15...Rubber product, 16...Setting point Figure 5

Claims (1)

[Claims] (1) Temperature detection step that detects the rubber surface temperature during vulcanization at predetermined time intervals Δ. Using the detected temperature in the temperature detection step as a constraint condition, the temperature at the set point inside the rubber after Δ time is thermally diffused. A temperature calculation step that calculates the equivalent vulcanization time or degree of vulcanization at the reference temperature from the calculated temperature in the temperature calculation step using the solution method of JM! a calculation processing step to perform the calculation, a comparison judgment step to compare and judge whether or not the equivalent vulcanization time or degree of vulcanization in the calculation processing step has reached a preset value, based on the judgment result in the comparison judgment step. A method for controlling a rubber vulcanization process, comprising the step of outputting a control signal to send a control signal to a vulcanization device.