JPH0210410A - Flow rate controller - Google Patents

Abstract

PURPOSE:To continuously control the flow rate of a fluid by controlling the opening/closing time of a cut-off valve which can be selectively switched to the open state or the close state. CONSTITUTION:The degree of cooling in a cooling part is controlled in accordance with the flow rate of a refrigerant in a flow passage L. A cut-off valve 1 is attached in the flow passage L and is selectively switched to two states, namely, the open state and the close state. A PID module (command means) 2 and an arithmetic module (arithmetic means) 3 are provided. The detected value of the temperature of the cooling part is inputted to the command means 2, and proportional integral and differential actions are performed to output a triangular wave corresponding to said detected value as a command signal C1. The arithmetic means 3 compares this command signal C1 with a certain threshold value S to output an opening/closing signal C2. Thus, the cut-off valve 1 is opened for a long time by actions of means 2 and 3 when the detected temperature of the cooling part is high.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a flow rate control device that controls the flow rate of fluid by selectively switching a shutoff valve between two states, open and closed, in response to a detected value.

[Prior Art] Conventionally, a control device that adjusts the flow rate of a cooling medium for temperature control, for example, has been equipped with a throttle valve installed in the flow path of the cooling medium, and the throttle valve is adjusted according to a detected temperature value. There is a flow rate control device that controls the flow rate of a cooling medium in an analog manner by steplessly adjusting the throttle.

[Problems to be Solved by the Invention] However, in the above-mentioned control device, the opening degree of the throttle valve is immediately reflected in the flow rate of the fluid, so it is necessary to delicately adjust the opening degree. Moreover, when controlling the flow rate of highly abrasive slurry, high viscosity fluid, etc., it is necessary to use an expensive throttle valve with excellent wear resistance.

The present invention aims to solve these problems and to provide a novel flow control device using a simple and inexpensive cutoff valve.

[Means for Solving the Problems] A flow rate control device of the present invention is a flow rate control device that controls the flow rate of a fluid in response to a detected value, and is installed in a flow path of the fluid to open or close a valve. a shutoff valve that can be selectively switched between two states; a command means that outputs a triangular wave corresponding to the detected value as a command signal; and a command means that outputs a triangular wave corresponding to the detected value as a command signal; The present invention is characterized by comprising a calculation means for outputting an opening/closing signal for the shutoff valve.

[Operation] The flow rate control device of the present invention controls the flow of fluid in the flow path to which the shutoff valve is attached by controlling the opening and closing time of the shutoff valve, which can be selectively switched between two states: open and closed. Control the flow rate.

[Example] Embodiments of the present invention will be described below based on the drawings.

1 to 3 are diagrams for explaining a first embodiment of the present invention.

In this example, ■ in the figure is the flow path of the cooling medium,
The degree of cooling in the cooling region is controlled according to the flow rate of the cooling medium in the flow path. A shutoff valve 1 is installed in this flow path. This shutoff valve 1 can be selectively switched between two states: open and closed.

Reference numeral 2 denotes a PID module (command means) which inputs a detected value of the temperature at the cooling part, performs proportional-integral-differential operation, and outputs a triangular wave corresponding to the detected value as a command signal Ct. The triangular wave has a constant period, and its duration becomes longer depending on the detected temperature. That is, when the detected temperature is high, as shown in FIG. 2(a),
A triangular wave that rises at a constant angle is repeatedly output for a relatively long period of time, while when the detected temperature is low, the waveform rises at a constant angle as shown in Figure 3 (a). Repeatedly output a triangular wave so that it lasts only a relatively short time.

3 is a calculation module (calculation means) which inputs the command signal Ct from the PID module 2 and outputs the command signal C1.
is compared with a certain threshold value S, and an opening/closing signal C2 is output. The opening/closing signal C2 is a rectangular wave with ON and OFF levels that opens and closes the shutoff valve 1, and when the command signal Ct exceeds the threshold value S, it becomes the ON level that opens the shutoff valve 1, and the command signal When C1 is less than the threshold value S, it becomes an OFF level that closes the shutoff valve l.

Therefore, when the command signal CI is as shown in FIG. 2(a), the ON level output time per predetermined unit time becomes relatively long as shown in FIG.
When is as shown in FIG. 3(a), the ON level output time per predetermined unit time is relatively short as shown in FIG. 3(b).

Such a PID module 2 and calculation module 3
Due to the operation, the shutoff valve 1 opens for a relatively long time per unit time when the detected temperature of the cooling part is high, and opens for a relatively short time per unit time when the detected temperature of the cooling part is low. It turns out. That is, the periodic opening and closing time of the cutoff valve 1 is adjusted according to the detected temperature. Therefore, in the former case, the flow rate M of the cooling medium in the flow path per unit time is relatively large, while in the latter case, the flow rate of the cooling medium in the flow path per unit time is relatively small. Become.

As a result, by simple switching control to open or close the shutoff valve l, the flow of cooling medium per unit time m
is automatically controlled according to the detected temperature, and the cooling part can be cooled to a predetermined temperature.

FIG. 4 is a diagram for explaining a second embodiment of the invention.

In the case of this embodiment, the PID module 2 outputs a triangular wave with a constant period whose slope varies depending on the detected temperature, and outputs it to the calculation module 3 as a specified value CI. That is, when the detected temperature is low, the designated value Ct repeatedly outputs a triangular wave with a relatively small slope as shown by the solid line in Figure 4 (a), while when the detected temperature is high, it outputs a triangular wave as shown in Figure 4 (a). As shown by the two-dot chain line in the middle, a triangular wave with a relatively large slope is repeatedly output. Such a command signal C1 takes a long time to exceed the threshold value S in the calculation module 3 when the slope of the triangular wave is small; on the other hand, when the slope of the triangle wave is large, it takes a long time to exceed the threshold value S in the calculation module It takes less time to cross. Therefore, in the former case, the output time of the ON signal of the opening/closing signal C2 per predetermined time becomes short, and the flow rate of the cooling medium becomes relatively small. On the other hand, in the latter case, the output time of the ON signal of the opening/closing signal c2 becomes longer per predetermined time, and the flow rate of the cooling medium becomes relatively large.

FIG. 5 and FIG. 6 are diagrams for explaining a third embodiment of the present invention.

In the case of this embodiment, the first . Second. Third three cutoff valves 1a, lb, and lc are installed in parallel, and the opening and closing of these cutoff valves 1a, lb, and lc are controlled in relation to each other by the PID module 2 and the calculation module 3. The PID module 2 outputs a command signal CI according to the detected temperature, as in the first embodiment or the second embodiment described above. The calculation module 3 converts the command signal CI into the first . Second. Third three thresholds Sa, S
b, Sc (Sa>Sb>Sc), when the command signal CI exceeds the threshold value Sa, the opening/closing signal C2-a for the first shutoff valve 1a is set to the ON level, and as shown in FIG.
), and when the command signal CI exceeds the threshold value sb, the opening/closing signal C2-b for the second shutoff valve 1b is turned ON.
level (see (C) in the same figure), and when the command signal C1 exceeds the threshold SC, the opening/closing signal C2-c for the third shutoff valve 1c is set to the ON level (see (d) in the same figure).
.

Therefore, when the command signal CI exceeds the threshold value Sa and is below the threshold value sb, only the first shutoff valve 1a opens; When it is less than the value Sc, the first. Second shutoff valve 1
Both valves a and 1b open, and the command signal CI reaches the threshold value S.
When it exceeds 1.c. Second. Third shutoff valve 1a, I
b, all valves 1C will be open. After all, the rangeability (control width) is wider depending on the relationship between the detected temperature and the command signal C1, which are correlated by the PID module 2, and the values of the threshold values Sa, Sb, and Sc set by the calculation module 3. This means that the flow rate can be controlled. By the way, in this embodiment, the arithmetic module 3 is divided into three parts, each of which individually compares the command signal CI with the first, second, and third three threshold values Sa, Sb, and Sc, and outputs the opening/closing signal. C2-a, C2-b, C2-c
It may also be possible to output .

Note that the PID module 2 only needs to output a triangular wave corresponding to the detected value as the command signal CI, and as in the above-mentioned embodiment, the extension time of the triangular wave of a constant period may be lengthened depending on the detected value. In addition to increasing the slope, the period of the triangular wave may be lengthened depending on the detected value, or a combination of these may be possible.

In addition, in the case of two consecutive embodiments, the PI as the command means
Since the D module 2 is used, the deviation from the control target value can be reduced by its proportional-integral-differential operation. In addition, non-linear control of the neutralization process etc. is also possible by using a geared I) ID adjustment module or the like.

Furthermore, it goes without saying that the object to be controlled is not specified by the flow rate of the cooling medium, and the detected value is not specified by the detected temperature.

[Effects] As described above, the original control device of the present invention includes a shutoff valve that can be switched between two states, open and closed, in a fluid flow path, and Since the structure controls the opening/closing time of the cutoff valve, the following effects can be achieved.

■Is it possible to continuously control the flow rate of fluid by simply controlling the opening and closing of a shutoff valve?

(2) Since a shutoff valve that can be switched to two states, open or closed, is used, a flow control device suitable for highly abrasive slurry, high viscosity fluid, etc. can be provided at a low cost. Moreover, it is also suitable as a control device that avoids pressure loss in a valve, such as for controlling the flow rate of a spray pipe.

■The range of flow rate control is wide because the opening/closing time of the shutoff valve is controlled per predetermined unit time. Moreover, by controlling the opening and closing of a plurality of shutoff valves installed in the fluid flow path, theoretically the rangeability becomes infinite.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining the first embodiment of the present invention, in which FIG. 1 is a schematic configuration diagram of the main parts, and FIG. 2 is the opening time of the shutoff valve per unit time. FIG. 3 is an explanatory diagram of the operation when the valve opening time per unit time of the shutoff valve is short. FIG. 4 is an explanatory diagram of the operation of the second embodiment of the present invention. 5 and 6 are diagrams for explaining the third embodiment of the present invention, in which FIG. 5 is a schematic diagram of the main part, and FIG. 6 is an explanatory diagram of the operation. 1...Shutoff valve, 2...PfD module (command means), 3...
... Arithmetic module (arithmetic means), L...
Fluid flow path.

Claims (1)

[Scope of Claims] A flow rate control device that controls the flow rate of fluid in response to a detected value, comprising: a shutoff that is installed in the fluid flow path and that can be selectively switched between two states: open or closed; a valve; a command means for outputting a triangular wave corresponding to the detected value as a command signal; and an arithmetic means for comparing the command signal with a certain threshold value and outputting an opening/closing signal for the shutoff valve in the form of a rectangular wave. A flow control device comprising: