JPS611983A - Controller for degree of vacuum - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling the degree of vacuum in a vacuum drying tank such as a vacuum drying device or a freeze vacuum drying device.

[Conventional technology]

Conventional vacuum control methods of this type include the barrier pull leak method, which controls the vacuum inside the vacuum drying tank by introducing outside air into the vacuum pump suction side, and the barrier pull leak method, which controls the vacuum inside the vacuum drying tank by introducing a resistor between the drying tank and the cold trap. There is a conductance method that controls the degree of vacuum in a vacuum drying tank.

As the conductance method, there is a control method in which a second flow path is provided as shown in FIG. 4 (Japanese Unexamined Patent Publication No. 52-44408) in order to improve control accuracy. In the figure, (1
) is the vacuum chamber that stores the object to be processed, (2) is the vacuum chamber (1)
0υ is the main butterfly type control valve, Q gong is the stop valve, 031 is the second pipe installed in parallel with the pipe (2), a4) is the second butterfly type control valve, ( 1. A nine-stop valve is installed in the second conduit 03.

Next, the operation will be explained. As the drying process progresses, the degree of vacuum in the vacuum chamber (1) is controlled by gradually decreasing the degree of opening of the main butterfly type control valve 01), and at the end of the drying, the degree of opening reaches a predetermined value. When it decreases, the limit switch is activated to stop inputting the control signal from the vacuum controller to the main butterfly type control valve 0υ, and the second
A predetermined control accuracy can be obtained by operating only the butterfly type control valve (14) and adjusting the conductance of the second pipe 0, which has a small area, in accordance with the decrease in the amount of discharge from the object to be treated. can.

There is also a structure in which the resistance valve itself is opened and closed in two stages, as shown in FIG. 5 (Japanese Patent Laid-Open No. 52-44408). In the figure, (2) is the exhaust pipe connecting the vacuum chamber (1) to the vacuum pump, (16m) is the main butterfly type control valve installed in the pipe (2), and (16II) is the butterfly type control valve. The small diameter secondary butterfly type control valve (16h) is installed in the center of the valve (16m), and the main butterfly type control valve (16h) is opened and closed by the secondary butterfly type control valve (1611).
6m). The resistance valve (16) formed in this way first operates the main butterfly type control valve (16m) using the control signal from the vacuum degree controller to control the degree of vacuum, thereby reducing the amount of radiation emitted from the workpiece. When the control valve (16m) moves in the opposite direction, and reaches a predetermined angle, the main butterfly type control valve (16m) stops operating with a signal from a limit switch, etc., and after that, the sub butterfly type control valve (16m) stops operating with a control signal.
) is activated, and the pressure inside the vacuum chamber, which has a reduced amount of radiation, can be controlled with high precision using a small-diameter, small-area secondary butterfly type control valve (16 m).

[Problem that the invention seeks to solve]

In vacuum drying and freeze-vacuum drying, the degree of vacuum within the vacuum drying tank has a large effect on the drying time and product quality of the processed material. In particular, in freeze-vacuum drying, when shelf heating is performed with the temperature of the frozen processed material and the degree of vacuum in equilibrium, 0) if the pressure inside the drying tank increases, heat conduction through voids, etc. will improve. This increases the heat flow into the workpiece and increases the drying rate. Then, the temperature of the object to be treated rises to a temperature corresponding to the pressure inside the tank.

(b) On the other hand, when the pressure inside the drying tank decreases, the flow of heat into the material to be processed decreases, the drying speed decreases, and the product temperature drops to a temperature corresponding to the pressure inside the tank.

(c) When the product temperature rises, the frozen material may melt or the frozen structure may collapse, resulting in deterioration of product quality.

Therefore, in freeze-drying, the pressure must be as high as possible without causing the frozen material to melt or the frozen structure to collapse.
It is desirable to process at product temperature, and for this reason, it is necessary to reliably and accurately control the degree of vacuum.

In order to perform this high-precision control, control methods with the structure described above have been proposed, but all of them require a complicated structure due to the installation of double butterfly valves and the provision of bypass pipes. Cost increases. Further, there are problems such as temporary disturbance input to the control system when switching from the main valve to the sub-valve, and the pressure of vacuum drying transiently fluctuating, which affects the object to be processed.

[Means to solve the problem]

This invention was made in order to solve the problems of the conventional ones as described above, and it involves interposing one flow control valve in the exhaust path from the vacuum chamber, and adjusting the operating speed according to the amount of deviation. The purpose of the present invention is to provide a vacuum degree control device that can simplify the configuration, simplify the control system, and improve control accuracy by controlling the degree of vacuum by changing the degree of vacuum.

As a means of simplifying the configuration, it is effective to use a butterfly type damper and change its operating speed according to the above deviation amount.Also, in order to compensate for the conductance characteristics of the butterfly type damper itself, it is effective to change its opening degree. It is also effective to change the operating speed accordingly. Of course, it is more preferable to apply pressure to change the operating speed based on the relationship between the deviation amount and the opening degree.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In Fig. 1, (1) is a vacuum drying tank for storing objects to be processed, (2) is an exhaust path, (3) is a butterfly type control valve, (
4) is a cold trap, (5) is a vacuum pump, (6)
is a Virani vacuum gauge that detects the degree of vacuum in the vacuum chamber (1), (
7) is the output of the non-linear vacuum gauge (6) (0 to 10 mVD,
C) is a linearizer, and (8) is a PID type (proportional ten integrator differential operation) pressure indicating controller, which adjusts the set value and p.
A mechanism is provided that generates a speed setting signal to switch the opening/closing operation speed of the butterfly type control valve (3) when the deviation amount from the v value reaches a predetermined value. (9) is the drive motor for operating the butterfly type control valve (3).
It has a variable speed controller. The member is a speed controller that adjusts the speed of the motor (9) to a predetermined speed in response to a speed setting signal.

Next, one operation will be explained. The degree of vacuum in the vacuum drying tank (1) is detected by the Virani vacuum gauge (6), and its nonlinear output is 0.
A signal of ~10 mVD, C is linearized by a linearizer (7) and input to a pressure indicating controller (8). Adjustment needle (8)
calculates a control signal with an optimally set proportional gain, integral time constant, and differential time according to the deviation between the input pv value and the set value, and drives the motor (9) according to the control signal. , the butterfly type control valve (3) is rotated to control the degree of vacuum in the vacuum drying tank (1) to match the set value. In this drying process, the amount of radiation from the object to be processed changes between the initial and final stages of drying, and also changes depending on the vacuum setting.

Therefore, the amount of deviation generated by the controller (8) is set to a predetermined value.

1L is set in advance, and as shown in FIG. 3, a signal is generated to switch the speed of the motor (9) between within and outside the set value range and is input to the speed controller αO. Here, the speed set by the speed controller α1 according to the speed switching signal, for example, a signal that drives the motor speed within the range of ~, ε1 at about 1/4 of the speed outside the range, is applied to the operating motor (9). 80R speed variable controller) a-ra, pv
When the value approaches the set value SP, the butterfly type control valve (3)
The rotational operation speed is reduced to about 1/4, that is, the amount of change in effective conductance of the unit control signal is reduced, thereby suppressing control overshoot and stabilizing the control system. On the other hand, if the amount of deviation is large, the operating speed of the butterfly type control valve (3) is fast, so the degree of vacuum may change during manual operation at the beginning of the drying process, when changing the settings of the controller (8), or due to external disturbances. There is no loss in followability when there is a large fluctuation. In this way, by providing only one normal butterfly type control valve with no special structure, stable and good control results can be obtained without causing hunting in the control system.

Further, in the above embodiment, the operating speed of the flow rate regulating valve is switched in accordance with the predetermined value of the deviation amount, but it may be switched in accordance with the opening degree of the regulating valve. For example, the characteristics of a butterfly type control valve are that, as shown in Figure 2, the ratio of effective conductance change/opening change is large on the low opening side, the drying load is small, and the operating vacuum pressure is high. When the opening degree is low, a signal from a doorway switch or the like that reaches a predetermined opening degree, for example, about 60 degrees, is input to the speed controller, and the operating speed is reduced by that signal. In this way, instability of the control system on the low opening side can be alleviated, and good control accuracy without hunting can be obtained. Furthermore, it goes without saying that even more precise and rapid vacuum control can be achieved by changing the damper operation speed according to the relationship between the deviation value between the set pressure and the detected pressure and the opening degree of the butterfly type control valve. In this case, the operating speed is controlled using, for example, the following matrix.

〔Effect of the invention〕

As described above, according to the present invention, the degree of vacuum is controlled by switching the operation speed of the butterfly type control valve according to the deviation or the pulp opening degree, or the relationship between the two, thereby stabilizing the control system. It is possible to obtain good table control accuracy without hunting, and since only one regular butterfly type control valve is required, the piping structure is simplified, equipment costs can be reduced, and maintenance is also easy. This effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a vacuum control device according to the present invention, Fig. 2 is an opening-effective conductance characteristic diagram of a butterfly-type control valve, and Fig. 3 is a diagram showing the relationship between deviation and operating speed of the butterfly-type control valve. , FIG. 4 is a block diagram of a conventional two-channel type control valve, and FIG. 5 is a block diagram of a conventional dual butterfly type control valve. (1)...Vacuum drying tank, (2)...Exhaust pipe, (3
)...Butterfly [11+11 section valve, (4)...Cold trap, (5)...Vacuum pump, (6)...
・Pirani vacuum gauge, (7)...linearizer, (8)・
・・Pressure indicating controller, (9) ・・・Drive motor for operation,
α1...Speed controller, (11)...1st
Butterfly type control valve, 03)...Second pipeline, along α...Second butterfly type control valve, (16)...Double butterfly type control valve, (16m)...Main butterfly Type control valve, (161)...Sub butterfly type control valve, (1
6h)...Butterfly valve hole.

Claims (3)

[Claims] (1) A flow rate control valve is interposed in the exhaust line that communicates from the vacuum chamber housing the workpiece to the vacuum source device, and the operating speed of the flow rate control valve is adjusted based on the setting value of the controller and the detected vacuum degree. A degree of vacuum control device, characterized in that the degree of vacuum is controlled by changing the degree of vacuum according to the correlation between the deviation amount of the flow rate control valve and the degree of opening of the flow control valve. (2) The vacuum degree control device according to claim 1, wherein the operating speed of the flow rate control valve becomes slower as the deviation between the set value of the controller and the detected vacuum degree becomes smaller. (3) The vacuum degree control device according to claim 1, wherein the operating speed of the flow rate control valve becomes slower as the opening degree of the flow rate control valve becomes smaller.