JPH062650A - Measuring pumping device - Google Patents

Abstract

PURPOSE:To provide a measuring pumping plant that is manufacturable inexpensively, and able to simply and accurately actualize such various discharge operating modes as altering discharge at one time and doing split injection, etc., in addition to such advanced and diversified control as optionally altering a speed pattern of discharge flow. CONSTITUTION:This pumping device is provided with a screw feeding mechanism 20 reciprocating a plunger 12 of a plunger pump 10, a stepping motor 30 rotatively driving a feed screw 23 of this feeding mechanism, and a photoelectric sensor 41 detecting a fact that the plunger 12 is situated in a zero position at the advancing side. In addition it is provided with an open-loop type motor controller 50 which gives the number of driving pulses conformed to the specified inlet quantity to the motor 30, rotating it in reverse, and makes the plunger retreat from the zero position, and simultaneously it gives the number of driving pulses conformed to the specified discharge to the motor 30, rotating it forward and advancing the plunger ahead.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metering pump device using a plunger pump that sucks and discharges a very small amount of liquid, and more particularly to a metering pump device that can arbitrarily set the discharge amount.

[0002]

As is well known, a plunger pump adopted in a general metering pump device sucks an amount of liquid corresponding to the amount of retreat (stroke) by retracting a plunger in a cylinder. Then, by moving the plunger forward, the amount of liquid corresponding to the forward stroke is discharged. The amount of suction and the amount of discharge are precisely determined by the backward stroke and forward stroke of the plunger. As a mechanism for driving the plunger of this pump, a cam actuation type and a pneumatic actuation type are generally used.

In the cam actuated metering pump device, the stroke (discharging amount) of the plunger is precisely set in advance according to the shape of the cam and is used for the purpose of repeating the discharging operation of the same amount. Of course, it is possible to change the discharge amount by changing the cam, but it is very troublesome to manufacture a new cam and replace the cam, and for example, to change the discharge amount each time. It cannot be used for any purpose.

In the pneumatically operated metering pump device, the stroke of the plunger is set by a mechanical stopper,
The force of the pneumatic cylinder activates the plunger. And
The position of the stopper can be finely and precisely adjusted by a micrometer type operation mechanism, and thus the stroke of the plunger can be varied. By adjusting the dial of the micrometer mechanism, the discharge amount can be set arbitrarily.

[0005]

In the pneumatic actuation type metering pump device, the discharge amount can be varied relatively easily (compared with the cam actuation type) by adjusting the dial of the micrometer mechanism. It has the following problems. A precise micrometer mechanism for adjusting the plunger stroke is required, which makes the device expensive. Ancillary equipment such as a pneumatic cylinder mechanism for driving the plunger, a pneumatic pump mechanism, and a control valve mechanism for the pneumatic cylinder is indispensable, and the device becomes large and expensive. For example, it is not impossible to change the discharge amount each time, but it is not practical at all. In addition, it is not possible to accurately discharge a liquid that has once been inhaled in minute quantities (divided injection). By installing the speed controller of the pneumatic cylinder, adjust the operating speed of the plunger during discharge,
The liquid discharge flow rate can be adjusted according to the application.
However, it is very difficult to change the operating speed of the plunger within the stroke of one discharge operation to perform high-level control that arbitrarily changes the speed pattern of the discharge flow.

The present invention has been made to solve the above-mentioned problems of the conventional device, and its object is a small-sized metering pump device which can be manufactured at low cost, and which has a recent electronic technology and a computer. By adopting digital control, which can be performed very easily by technology, various discharge operation modes such as changing the discharge amount and split injection can be realized easily and accurately. It is an object of the present invention to provide a metering pump device capable of performing a variety of advanced controls that arbitrarily change the velocity pattern of the discharge flow.

[0007]

SUMMARY OF THE INVENTION A metering pump device according to the present invention includes a plunger pump which sucks in an amount of liquid corresponding to the amount of retreat of the plunger and discharges an amount of liquid corresponding to the amount of advance of the plunger. A screw feed mechanism that reciprocally drives the plunger of the pump, a stepping motor that rotationally drives a feed screw of the screw feed mechanism, and a drive pulse of a number corresponding to a designated suction amount are given to the motor to reverse the same. , An open-loop motor control means for moving the plunger backward, applying a number of drive pulses corresponding to a specified discharge amount to the motor to rotate the motor forward, and moving the plunger forward. is there.

[0008]

The stepping motor is accurately rotationally displaced by an angle corresponding to the number of driving pulses applied. The rotational displacement of the motor is proportionally and accurately converted into the linear displacement of the plunger by the screw feeding mechanism. Therefore, the stroke of the plunger, that is, the amount of suction and the amount of discharge can be variably controlled by simple digital control in which the number of drive pulses applied to the stepping motor is arbitrarily variably set. Further, the operation speed of the plunger can be arbitrarily controlled by the frequency of the drive pulse applied to the stepping motor, and thus the speed pattern of the discharge flow can be variously controlled.

[0009]

1 shows the schematic construction of a metering pump device according to an embodiment of the present invention. The mechanical configuration of this metering pump device is roughly divided into a plunger pump 10, a screw feed mechanism 20, and a stepping motor 30. The plunger pump 10 has a well-known structure, and the plunger 12 is fitted and inserted into the cylinder 11 so that the plunger 12 can smoothly slide back and forth in the axial direction. Further, the suction port 1 is connected so as to communicate with the space inside the cylinder 11 on the tip side of the plunger 12.
3 and the discharge port 14 are formed, and check valves 15 and 16 are attached to both ports, respectively. When the plunger 12 retracts to the right in the figure, the cylinder 11
And the liquid is sucked into the cylinder 11 through the suction port 13. When the plunger 12 moves leftward, the volume of the cylinder 11 is reduced and the liquid in the cylinder 11 is discharged from the discharge port 14.
And, as described above, the amount of liquid suction is
And the discharge amount is determined by the forward stroke amount of the plunger 12.

The screw feed mechanism 20 is arranged on the rear end side of the plunger 12. The feed screw 23 is rotatably supported by bearings 25 and 26 attached to the support plates 21 and 22, and is arranged parallel to the plunger 12. The rear end protruding portion of the plunger 12 is a support plate 21.
Penetrates the slide guide 27 attached to
A linear motion block (ball nut) 24 mounted around the axis of the feed screw 23 is mechanically coupled to the rear end of the plunger 12. When the feed screw 23 is rotated, the linear motion block 24 moves to the right or left along the feed screw 23 according to the rotation direction and the amount of rotation, and the plunger 12 of the pump 10 moves forward or backward together with the movement. To do.

The stepping motor 30 is attached to a support plate 33 arranged on the rear end side of the feed screw 23, and its rotor shaft 31 is connected by a joint 32 to the feed screw 2.
It is directly connected to 3. The stepping motor 30 drives the feed screw 23 to rotate arbitrarily to move the plunger 12
To reciprocate. From this motor 30 to the plunger 12
There is almost no mechanical play in the drive system up to, and the rotation amount of the motor 30 and the stroke amount of the plunger 12 correspond linearly with high accuracy.

A photoelectric sensor 41 is attached to the slide guide 27 of the screw feed mechanism 20 in order to detect the origin position of the plunger 12 on the forward side. When the plunger 12 moves forward to an appropriately set origin position, a mark (not shown) attached to the plunger 12 reaches the detection point of the photoelectric sensor 41, and at that time, the photoelectric sensor 41 outputs a detection signal. ing.

A mark plate 42 is attached to the feed screw 23 and a photoelectric sensor 43 is attached to the support plate 22 in order to detect the origin of the stepping motor 30 in the rotational direction of the rotor shaft 31. ing. The mark plate 42 has only one mark on the circumference, and when the mark reaches the detection point of the photoelectric sensor 43, the photoelectric sensor 43 outputs a detection signal.

The rotation of the stepping motor 30 is controlled by a motor control device 50 using a microprocessor to control the operation of the plunger pump 10.

A schematic structure of the motor control device 50 is shown in FIG. As shown in FIG. 2, the multi-phase drive pulse train output from the pulse generation unit 51 is amplified by the drive unit 52 and supplied to the stepping motor 30. The microprocessor 53 controls the pulse generator 51 and the driver 53,
The rotation of the stepping motor 30 is controlled. Various control information such as an inhalation amount, an ejection amount, or an ejection speed is input to the microprocessor 53 from an input unit 54 such as a keyboard. Information input by the input unit 54, response information of the microprocessor 53, and the like are displayed on the display unit 55 using a liquid crystal panel or the like. Further, the outputs of the photoelectric sensors 41 and 43 for detecting the origin are also input to the microprocessor 53.

The microprocessor 53 accurately positions the plunger 12 at the origin position on the forward side as follows. The control procedure of this positioning is shown in the flowchart of FIG. First, in step 301, the pulse generator 51 and the driver 52 are controlled to rotate the stepping motor 30 forward at a relatively low speed. This causes the plunger 12 to slowly move forward (to the left in FIG. 1). With the plunger 12 thus moved forward, in step 302, the photoelectric sensor 41 waits for the detection signal to be output. If the detection signal is output, the photoelectric sensor 43 is output in the next step 303. Wait for the detection signal to be output, and if the detection signal is output, proceed to the next steps 304, 3
In step 05, the stepping motor 30 is stopped at the zero phase timing of the motor drive pulse train. The stop position of the plunger 12 at this time is the origin.

The most common operation mode of the metering pump device is an operation of sucking a specified amount of liquid and discharging the same amount. The control procedure of this normal operation mode is shown in the flowchart of FIG. When the desired discharge amount is set by the input unit 54 and then started in the normal operation mode, the microprocessor 53 converts the designated discharge amount (synonymous with the suction amount) into the motor drive pulse number in step 401. In the next step 402, an acceleration pattern when the motor is started and a deceleration pattern when the motor is stopped are set. Then, the stepping motor 30 is reversely rotated by a predetermined amount in a predetermined speed pattern and stopped (step 403). As a result, the plunger 12 retracts from the origin by a certain amount, and a designated amount of liquid is sucked into the cylinder 11. Next, the stepping motor 30 is rotated forward by a predetermined amount in a predetermined speed pattern and stopped (step 404). Plunger 12
Moves forward by a certain amount, and the specified amount of liquid is transferred to the cylinder 11
Is discharged from. It is to be noted that when the stepping motor 30 is rotated in the normal direction → stopped, it is confirmed whether or not the plunger 12 has returned to the origin (step 405).
6).

An example of the rotational speed pattern of the motor 30 in the normal operation mode is shown in FIG. As shown in FIG. 5, the stepping motor 30 is started at a low speed equal to or lower than the self-starting frequency, gradually increased to a constant speed, and decelerated in a symmetrical pattern and then stopped. The maximum speed of the motor rotation and the acceleration / deceleration rate are appropriately set according to the amount of liquid to be sucked and discharged, as shown by the dotted line in the figure.

As described above, since the operating speed pattern of the plunger 12 at the time of discharging can be freely set by digital control, an appropriate speed and speed change of the discharging flow can be realized according to the characteristics of the liquid to be discharged and the intended use. can do. When the intake / discharge amount is changed for each operation in the normal operation mode, the discharge amount for each time is programmed as in the NC control, whereby completely automatic control is possible.

FIG. 6 shows a control pattern of the motor 30 when operating the plunger pump 10 in the above-mentioned split injection mode. As is apparent from FIG. 6, after a predetermined amount of liquid is sucked in by one suction operation, the plunger 12 can be moved forward by a predetermined amount in a plurality of times and divided injection (discharging) can be performed by a predetermined amount.

Depending on the viscosity of the liquid, when the forward movement of the plunger 12 is stopped (when the ejection is completed), the liquid may be ejected with a slightly larger amount than the set amount due to the inertial effect of the liquid. This phenomenon is called dripping. In order to prevent this dripping phenomenon, it is effective to set the rotation control pattern of the stepping motor 30 as shown in FIG.
As shown in FIG. 7, immediately after the plunger 12 is moved forward and then stopped to end the discharge operation, the plunger 12 is slightly retracted and stopped. The liquid sucking action due to this retreat can prevent dripping due to the inertial effect.

[0022]

As described in detail above, the metering pump device of the present invention is configured such that the plunger of the plunger pump is operated by the screw feeding mechanism using the stepping motor as the rotational driving source and the rotation of the stepping motor is controlled. It is configured to be controlled by an open loop type control device. The rotation amount and rotation speed of the stepping motor can be controlled with extremely high accuracy even with open loop control, and the rotation amount and speed of this motor are converted to the stroke amount and speed of the plunger with very high accuracy by the screw feed mechanism. It Therefore, the plunger pump can be precisely controlled by electrical control of the stepping motor. Moreover, since the rotation of the stepping motor can be controlled in various operation modes with a simple and inexpensive digital control circuit using a microprocessor or the like, the discharge amount can be changed or divided injection can be performed each time.
It is possible to easily and accurately realize various discharge operation modes, and it is possible to easily perform various advanced controls such as arbitrarily changing the speed pattern of the discharge flow.

Further, the mechanical structure including the plunger pump, the screw feed mechanism and the stepping motor is remarkably simple as compared with the conventional metering pump device of this type, and even if an electric motor control circuit is added, the whole structure is improved. As a result, the cost is greatly reduced, and it is easy to downsize the device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a mechanical system of a metering pump device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an electric system of the apparatus of the above embodiment.

FIG. 3 is a flowchart of origin positioning control in the apparatus of the above embodiment.

FIG. 4 is a flowchart of a normal operation mode in the apparatus according to the same embodiment.

FIG. 5 is a motor rotation control pattern diagram in a normal operation mode in the above-described embodiment apparatus.

FIG. 6 is a motor rotation control pattern diagram in a split injection mode in the apparatus of the above embodiment.

FIG. 7 is a motor rotation control pattern diagram in which a dripping prevention mode is added in the device of the above embodiment.

[Explanation of symbols]

10 Plunger Pump 12 Plunger 20 Screw Feed Mechanism 23 Feed Screw 24 Direct Acting Block 30 Stepping Motor 41 Photoelectric Sensor 42 Mark Plate 43 Photoelectric Sensor 50 Motor Control Device

Claims (4)

[Claims] 1. A plunger pump that sucks in an amount of liquid corresponding to the amount of retreat of the plunger and discharges an amount of liquid corresponding to the amount of advance of the plunger, and a screw feed mechanism that reciprocally drives the plunger of the pump. , A stepping motor that rotationally drives the feed screw of this screw feed mechanism, and a drive pulse of a number corresponding to the specified suction amount are applied to the motor to reverse it, move the plunger backward, and discharge the specified discharge. A metering pump device comprising: an open-loop motor control unit that applies a number of drive pulses corresponding to the amount to the motor to rotate the motor forward and to move the plunger forward. 2. The motor control means includes control means for starting the motor at an appropriate low speed and then accelerating the motor to a predetermined speed and decelerating to the appropriate low speed and then stopping the motor. The metering pump device according to claim 1. 3. The metering pump device according to claim 1, wherein the motor control means includes control means for intermittently rotating the motor in a normal amount intermittently. 4. The metering pump device according to claim 1, wherein the motor control means includes control means for rotating the motor in a normal direction and stopping the motor to reversely rotate the motor by an appropriate amount immediately after the motor is stopped.