JPH0357891A - Fixed quantity pump control circuit - Google Patents

Abstract

PURPOSE:To prevent the sudden change of a pouring in quantity even at the time of the change of the pouring in quantity of a fixed quantity pump and prevent the stress of the pump, by providing a revolution number control portion which controls the pump when the pouring in quantity of the fixed quantity pump is within a predetermined range, and a stroke control portion which conducts control when the pouring in quantity is out of the predetermined range. CONSTITUTION:When a pouring in quantity which is set is low, and a revolution number which is obtained by means of a fixed quantity pump 7 revolution number detector 8 is smaller than a predetermined value, a NOT circuit 13 outputs a revolution number control command, and actuates a revolution number control circuit 2, and at the same time, the PID control of the revolution number of the pump 7 is made. Next, the value of the pouring in set value is changed, and the revolution number obtained from the detector 8 of the pump 7 becomes larger than the predetermined value, and a stroke control commencement signal is outputted from a revolution number inspection circuit 10, then, an AND circuit 12 outputs a stroke commencement command. As a result, the NOT circuit 13 stops the action of the revolution number control circuit 2, and the revolution number of the pump 7 is fixed. Also, the pump 7 is changed over from the revolution number control to the stroke control or conversely, a hysteresis characteristic is had at the pump 7 at the time of changeover, and changeover is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a metering pump control circuit that performs rotation speed control and stroke control on a metering pump to control the injection amount.

(Prior Art) A circuit shown in FIG. 3 is conventionally known as a metering pump control circuit for controlling metering pumps used in various industries.

The metering pump control circuit shown in this figure consists of the injection amount calculation circuit 1
01, a rotation speed control circuit 102, and a stroke control signal switching circuit 103.
The rotation speed and stroke are controlled.

The injection amount calculation circuit 101 calculates the amount of the metering pump 104 based on the output (rotation speed) of the rotation speed detector 105 attached to the metering pump 104 and the output (stroke) of the stroke detector 106 attached to the metering pump 104. The injection amount is calculated and supplied to the rotation speed control circuit 102 and the stroke control signal switching circuit 103.

The rotation speed control circuit 102 generates a rotation speed control signal such that the injection amount outputted from the injection amount calculator 101 follows the injection amount setting value, and performs PID control on the rotation speed of the metering pump 104.

Further, the stroke control signal switching circuit 103 switches the fixed stroke value step by step in accordance with the injection amount output from the injection amount calculation circuit 101, and also generates a stroke control signal corresponding to this fixed stroke value to determine the fixed stroke value. The stroke of the pump 104 is switched and controlled.

Then, the value of the rotation speed control signal outputted from the rotation speed control circuit 102 as shown in FIG. 4 according to the injection amount setting value,
The injection amount of the metering pump 104 is controlled by changing the value of the stroke control signal output from the stroke control signal switching circuit 103.

In this way, in this metering pump control circuit, PID control is applied to rotation speed control, which has excellent controllability,
By performing stroke control as auxiliary control to this rotation speed control, resolution of controllability is increased in the overall injection amount, and control interference that occurs when both rotation speed and stroke are controlled by PID is prevented.

Furthermore, as a method of controlling the metering pump 104, in addition to such a control method, for example, a method shown in FIG. 5 is also known.

The control method shown in this figure is a method in which the rotational speed of the metering pump 104 is fixed at a constant value and the injection amount is controlled only by stroke control, and the metering pump 104, which has large injection amount fluctuations due to rotational speed control, is controlled. It is used only when controlling a metering pump 1o4 that has mechanical problems.

(Problems to be Solved by the Invention) However, the conventional control method described above has the following problems.

First, in the control shown in Fig. 4, when the rotation speed control is executed at a certain fixed stroke value, the rotation speed is 10
When the stroke value increases to nearly 0%, the stroke must be shifted to the next upper fixed stroke value, so the rotation speed control cannot follow the fixed stroke change and the injection amount temporarily deviates significantly from the injection setting value. If the amount of injection by the metering pump 104 becomes too large or too small due to such a deviation, it will have an adverse effect on the plant, and stress will be generated on the metering pump 104 due to steep control.

Further, in the control shown in FIG. 5, since the rotation speed is fixed, there is a problem that the injection amount cannot be lowered below a certain value.

In view of the above circumstances, the present invention makes it possible to prevent the injection amount from changing suddenly even when changing the injection amount of the metering pump, thereby preventing an adverse effect on the plant, and making it possible to It is an object of the present invention to provide a metering pump control circuit that can prevent stress from occurring in the pump.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a metering pump control circuit according to the present invention provides a metering pump control circuit that controls the injection amount of the metering pump, in which the injection amount of the metering pump is within a predetermined range. a rotation speed control section that controls the metering pump by rotation speed control when the metering pump is in the predetermined range, and a stroke control section that controls the metering pump by stroke control when the injection amount of the metering pump is outside the predetermined range. It is characterized by

(Function) In the above structure, when the injection amount of the metering pump is within a predetermined range, the rotation speed of the metering pump is controlled by the rotation speed controller, and when the injection amount of the metering pump is outside the predetermined range, the rotation speed of the metering pump is controlled. The metering pump is stroke-controlled by the metering section.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a metering pump control circuit according to the present invention.

The metering pump control circuit shown in this figure consists of the injection amount calculation circuit 1
, a rotation speed control circuit 2, a rotation speed operation output switching circuit 3, a stroke control circuit 4, a stroke operation output switching circuit 5, and a switching control circuit 6, and the injection amount setting value is a predetermined value. When the injection amount is smaller, the rotation speed of the metering pump 7 is controlled by PID control to control the injection amount, and when the injection amount setting value is larger than a predetermined value, the stroke of the metering pump 7 is controlled by PID control to control the injection amount.

The injection amount calculation circuit 1 calculates the amount of injection into the metering pump 7 based on the output (rotation speed) of the rotation speed detector 8 attached to the metering pump 7 and the output (stroke) of the 7 stroke detector 9 attached to the metering pump 7. The injection amount is calculated and supplied to the rotation speed control circuit 2 and the stroke control circuit 4.

When the rotation speed control command is output from the switching control circuit 6, the rotation speed control circuit 2 performs PID calculation so that the injection amount output from the injection amount calculator 1 follows the injection amount setting value. A rotation speed control signal is generated and supplied to the rotation speed control output switching circuit 3.

The rotation speed control output switching circuit 3 selects the rotation speed control signal output from the rotation speed control circuit 2 and supplies it to the metering pump 7 when the rotation speed control command is output from the switching control circuit 6. Then, the rotation speed of this metering pump 7 is controlled by PID. Further, when the rotation speed control command is not output from the switching control circuit 6, the output (rotation speed) of the rotation speed detector 8 is selected and supplied to the metering pump 7. Maintain rotation speed.

Further, when the stroke start command is output from the switching control circuit 6, the stroke control circuit 4 performs PID calculation so that the injection amount output from the injection amount calculator 1 follows the injection amount setting value. A stroke control signal is generated and supplied to the stroke operation output switching circuit 5.

The stroke operation output switching circuit 5 selects the stroke control signal output from the stroke control circuit 4 when the stroke start command is output from the switching control circuit 6, and supplies it to the metering pump 7 to perform this metering operation. The stroke of the pump 7 is controlled by PID. Further, when the stroke start command is not output from the switching control circuit 6, a preset fixed stroke signal is selected to fix the stroke of the metering pump 7.

The switching control circuit 6 also includes a rotation speed detection circuit 10, a stroke detection circuit 11, an AND circuit 12, and a knot circuit 1.
3 and an off-delay circuit 14, when the rotation speed of the metering pump 7 is below a predetermined value, the rotation speed control circuit 2, the rotation speed manipulation output switching circuit 3, the stroke control circuit 4, and the stroke manipulation output switching circuit are provided. The rotation speed of the metering pump 7 is controlled by PID control by controlling the circuit 5, and when the rotation speed of the metering pump 7 is equal to or higher than a predetermined value, the rotation speed control circuit 2, the rotation speed operation output switching circuit 3, and the stroke control circuit 4. Control the stroke operation output switching circuit 5 to PID control the stroke of the metering pump 7.

The rotation speed detection circuit 10 has hysteresis characteristics,
When the rotational speed output from the rotational speed detector 8 exceeds a predetermined value, a stroke control start signal is generated and supplied to the AND circuit 12.

Further, the stroke detection circuit 11 includes the rotation speed detection circuit 1.
0, it has a hysteresis characteristic, and when the stroke output from the stroke detector 9 exceeds a predetermined value, it generates a stroke control start signal and supplies it to the AND circuit 12.

The AND circuit 12 detects when the stroke control start signal is output from the stroke detection circuit 11 and the rotation speed detection circuit 10, generates a stroke start command, and sends this to the stroke control circuit 4 and the knot circuit 13
and off-delay circuit 14, respectively.

When the stroke start command is not output from the AND circuit 12, the knot circuit 13 generates a rotation speed control command and supplies it to the rotation speed control circuit 2 and the rotation speed control output switching circuit 3.

Furthermore, when the stroke start command is being output from the AND circuit 12, generation of the rotation speed control command is stopped.

Further, when the stroke start command is output from the AND circuit 12, the off-delay circuit 14 supplies it to the stroke operation output switching circuit 5, and when the stroke start command is no longer output from the AND circuit 12, After a predetermined time delay, the supply of the stroke start command to the stroke operation output switching circuit 5 is stopped.

Next, the operation of this embodiment will be explained with reference to the schematic diagram shown in FIG.

First, when the injection set value is low and the rotation speed obtained by the rotation speed detector 8 attached to the metering pump 7 is smaller than a predetermined value, the rotation speed detection circuit 10 does not output a stroke control start signal, so the AND circuit 12 does not output a stroke start command.

Therefore, in this case, the knot circuit 13 outputs a rotation speed control command to operate the rotation speed control circuit 2, and also outputs a rotation speed control command to the rotation speed control circuit 2 to operate the rotation speed control circuit 2.
, and the rotation speed of the metering pump 7 is controlled by PID.

At this time, since the stroke start command is not outputted from the AND circuit 12, the off-delay circuit 14 causes the stroke operation output switching circuit 5 to select a fixed stroke value, thereby fixing the stroke of the metering pump 7.

In this state, the value of the injection setting value is changed and the metering pump 7
When the rotation speed obtained by the rotation speed detector 8 attached to the motor becomes larger than a predetermined value and the rotation speed detection circuit 10 outputs a stroke control start signal, the AND circuit 12 outputs a stroke start command.

As a result, the knot circuit 13 stops generating the rotation speed control command and stops the operation of the rotation speed control circuit 2, and also causes the rotation speed manipulation output switching circuit 3 to select the output of the rotation speed detector 8, thereby determining the rotation speed. The rotation speed of the pump 7 is fixed.

Further, the stroke control circuit 4 starts operating in response to the stroke start command output from the AND circuit 12, and the off-delay circuit 14 controls the stroke operation output switching circuit 5 to select the stroke control circuit 4. and the stroke of the metering pump 7 is PID
controlled.

In this state, if the value of the injection setting value is changed and the stroke output from the stroke detector 9 attached to the metering pump 7 becomes equal to or less than a predetermined value, a stroke control start signal is sent from the stroke detection circuit 11. is no longer output, and correspondingly, the AND circuit 12 stops generating the stroke start command.

As a result, the stroke control circuit 4 stops operating, and the off-delay circuit 14 causes the stroke operation output switching circuit 5 to select a fixed stroke value, thereby fixing the stroke of the metering pump 7.

At this time again, knot circuit! 3 outputs a rotation speed control command to operate the rotation speed control circuit 2, and causes the rotation speed operation output switching circuit 3 to select the output of the rotation speed control circuit 2, thereby controlling the rotation speed of the metering pump 7 by PID control. let

As described above, in this embodiment, when the injection amount of the metering pump 7 is smaller than a predetermined value, the rotation speed of the metering pump 7 is controlled by PID, and when the injection amount of the metering pump 7 is larger than a predetermined value, the metering pump 7 is controlled. PI stroke of 7
Since the injection volume of the metering pump 7 is changed to 8, it is possible to prevent the injection volume from changing suddenly. 7 can be prevented from causing stress.

In addition, in this embodiment, when switching the metering pump 7 from rotational speed control to stroke control,
Since a hysteresis characteristic is provided when switching from stroke control to rotation speed control, control switching can be stabilized, and the operation of metering pump 7 can be stabilized.

〔Effect of the invention〕

As explained above, according to the present invention, even when changing the injection amount of a metering pump, it is possible to prevent the injection amount from changing suddenly, thereby preventing an adverse effect on the plant. , it is possible to prevent stress from occurring in the metering pump.

4. Simplification of Drawings 111 / (Explanation) Figure 1 is a block diagram showing an embodiment of the metering pump control circuit by Masaaki Moto, Figure 2 is a schematic diagram showing an example of the operation of the same embodiment, and Figure 3 is a conventionally known block diagram. FIG. 4 is a schematic diagram showing an example of the operation of the metering pump control circuit shown in FIG. 3, and FIG. 5 is a block diagram showing an example of the metering pump control circuit shown in FIG. FIG. 2 is a schematic diagram showing an example of the operation.

2... Rotation speed control section (rotation speed control circuit) 4... Stroke control section (stroke control circuit) 6... Switching control circuit 7... Metering pump

Claims (1)

[Claims] (1) A metering pump control circuit that controls the injection amount of the metering pump, comprising: a rotation speed control section that controls the metering pump by rotation speed control when the injection amount of the metering pump is within a predetermined range; A metering pump control circuit comprising: a stroke control section that controls the metering pump by stroke control when the injection amount is outside the predetermined range.