JP2556039B2 - Feed pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid delivery pump used for delivering a mobile phase in a liquid chromatograph, and more particularly to a small plunger reciprocating type pump having two pump heads. The present invention relates to a double-plunger type liquid delivery pump provided.

(Prior Art) A conventional liquid feed pump is not provided with a means for monitoring the flow rate. Therefore, the only way to do this is to monitor the pressure to see if the liquid is being sent normally.

Normally, the liquid feed pump is provided with a limiter for detecting the upper limit and the lower limit of the pressure. However, this limiter can only detect that there is clogging or leakage somewhere in the liquid feed system.

(Problems to be Solved by the Invention) Various abnormalities occurring in the liquid feed pump can be detected by observing minute changes in the pressure waveform of the liquid feed pump. However, it is not practical from the viewpoint of the measurement method to always observe such a pressure waveform, and even if such a pressure waveform is viewed, it may not be possible to judge that it does not have sufficient experience and knowledge. . And
If an abnormality occurs in the liquid feeding operation of the liquid feeding pump, there arises a problem in reliability of measurement data such as analysis.

INDUSTRIAL APPLICABILITY The present invention increases the reliability of analysis data and the like by automatically detecting the presence or absence of abnormality in the liquid feeding operation of the liquid feeding pump and giving a warning to the operator, and facilitates maintenance of the liquid feeding pump. The purpose is to

(Means for Solving the Problems) FIG. 1 shows the configuration of the present invention.

2 is a liquid delivery pump main body of a double plunger type pump having two pump heads arranged in parallel, 4 is a measuring means for measuring the discharge pressure of the liquid feed pump main body 2, 6 is a digital signal from the measuring means 4. A / D converter for converting to signal, 8
Is a memory that captures and stores the output of the A / D converter 6 at regular time intervals or once every cycle, and 10 is the content stored in the memory 8 that indicates that the pressure is the lowest due to pulsation from the start of discharge in each pump head discharge period. To the point where the displacement of the plunger, the rotation angle of the cam that drives the plunger or the time is extracted as the operating characteristic of the pump, and the characteristic extraction unit that detects the slope of the pressure drop due to the pulsation, 12 is the operating characteristic of each pump head The setting unit that sets the degree of difference in size as a setting condition, 14 compares the operating characteristic extracted by the characteristic extracting unit 10 with the setting condition of the setting unit 12, and determines the operating characteristic of each pump head. Whether the pump operation is normal depending on the degree of difference and the magnitude of the slope of the pressure drop due to pulsation,
Further, when there is an abnormality, a comparison / determination unit that determines which of the pump head inlet valve and the outlet valve has the abnormality, and 16 is a display unit that displays the determination result of the comparison determination unit 14.

(Operation) When two pump heads 2a and 2b are arranged in parallel, if an abnormality occurs in the inlet valve of the pump head 2a or the outlet valve of the pump head 2b, the pressure drops during the discharge period of the pump head 2a. If an abnormality occurs in the inlet valve of the pump head 2b or the outlet valve of the pump head 2a, the pressure will decrease during the discharge period of the pump head 2b. When the inlet valve is abnormal, the gradient of pressure drop is gentler than when the outlet valve is abnormal. Thus, for example, a pump head
If the pressure drop occurs during the discharge period of 2a and the slope of the pressure drop is gentle, it is judged that an abnormality has occurred in the inlet valve of the pump head 2a, and if the slope of the pressure drop is steep, the outlet valve of the pump head 2b. It can be judged that something went wrong. Further, for example, if the pressure drop occurs during the discharge period of the pump head 2b and the slope of the pressure drop is gentle, it is determined that an abnormality has occurred in the inlet valve of the pump head 2b, and if the slope of the pressure drop is steep, the pump is It can be determined that an abnormality has occurred in the outlet valve of the head 2a.

(Embodiment) FIG. 2 shows an embodiment of the present invention.

A pressure sensor 18 is provided in the flow path 3 to which the mobile phase is supplied by the pump body 2. The detection signal of the pressure sensor 18 is amplified by the amplifier 20, converted into a digital signal by the A / D converter 6, and taken into the microcomputer 22. The pressure sensor 18 and the amplifier 20 constitute the measuring means 4 in FIG.

The microcomputer 22 is provided with a CPU 24, a function as the memory 8 of FIG. 1 for storing measurement data, a RAM 25 for storing setting conditions as a setting unit 12, and a ROM 26 for storing operation programs. There is. RAM25, ROM2
6 and the CPU 24 are connected to each other by a bus 28. The microcomputer 22 is a memory 8 and a characteristic extraction unit in FIG.
10, a setting unit 12 and a comparison determination unit 14 are configured to control the overall timing of the liquid delivery pump and determine the state. Reference numeral 30 is an operation unit for starting an operation and setting conditions, 32 is a pump drive unit for driving the pump 2, both of which are connected to the bus 28 of the microcomputer 22 via an interface (not shown). .

First, the operation of a single pump head will be described as a comparative example.

When the pump operates normally, the pressure waveform is
Let it be as shown in the figure. C is for pump 1
Represents a cycle. A pressure drop is seen when the pump is in the suction process. Therefore, as a first example, the sampling period of the pressure value is made sufficiently shorter than one cycle so that such a pressure drop portion can be sufficiently captured, and the resolution of pressure measurement is also sufficient.

Then, for example, when the check valve has a malfunction, the pressure waveform as shown in FIG. 4 is observed even though the check valve is operated at the same flow velocity and pressure as in the normal state.

Therefore, for an actually obtained pressure waveform of one cycle, the pulsation magnitude a as shown in FIG. 5 and the time b for the pressure to return to a certain value are measured and compared with a value within the normal range. You can check if the pump is working properly. And if this measurement is performed with sufficient fineness in both the pressure resolution and the sampling period,
The characteristics such as a and b shown in FIG. 5 can be accurately known, and the certainty of the determination can be increased.

In this example, parameters a and b indicating the normal operation of the pump are stored in the RAM 25 from the operation unit 30 in FIG.

 FIG. 6 shows the procedure of the operation of this example.

The CPU 24 starts data collection when the plunger of the pump body 2 reaches the initial position. Then, this data was collected at a certain time interval, and the pressure value (A /
The D-converted one) is stored in a predetermined position in the RAM 25 (steps S1 and S2). When one cycle of pump operation is completed, this data collection is also completed for one cycle (step S
3). In this way, the pressure waveform for one cycle of the pump is taken into the RAM 25.

Next, the pulsation magnitude a and the recovery time b are calculated as characteristics from the stored data for one cycle (step S
4) and compare with the set values a and b (step S5). If the measured characteristic is within the normal operation range, data is sampled again in the same manner, and comparison judgment is advanced (steps S6 → S1).

On the other hand, as a result of comparison with the set value, if the characteristic values a and b are not within the normal range, the operator is warned by displaying them on the display unit (step S7).

Although the types of abnormalities that are likely to occur and the appearance of their pressure waveforms differ depending on the liquid feed pump, they are usually reproducible, and the determination may be made according to each.

 Next, another comparative example will be described.

If there is any abnormality in the operation of the pump, some information can be obtained by examining the continuous pressure waveform. For example, the pressure waveform as shown in FIG. 8 is observed when bubbles remain in the pump head. Therefore,
If the pulsation of the waveform captured in the memory is larger than the reference value and is gradually decreasing, it can be determined that there are bubbles in the pump head. By operating the computer section in this way, the operator knows that there are bubbles presently, and as a result, the operator can take actions such as waiting for the bubbles to naturally discharge or increasing the flow velocity of the pump to accelerate the discharge. .

In this example, the microcomputer 22 controls the drive of the pump main body and at the same time measures the discharge pressure, and uses the minimum value c and the maximum value d of the pressure as data for each step of the pump operation as data. Input and RAM these for a period of time, for example 100 consecutive pumping steps
Store in 25 predetermined positions.

 Next, the operation of this comparative example will be described with reference to FIG.

The minimum value c and the maximum value d of the pressure are collected for each process of the pump operation and are stored (steps S11 and S1).
2). Then, the data is collected for a predetermined number of steps, for example 100
After performing the process (step S13), the operation unit 30
According to the conditions set from, it is determined what kind of pump operation the continuous waveform is in (step S1
Four). Then, if the pump operation is normal from the determination result, data collection is restarted (steps S15 → S1).
1) Repeat the same operation. On the other hand, if the pump operation is abnormal from the determination result, what kind of abnormality is displayed (step S16), data collection is started again, and the same operation is repeated (steps S16 → S11). .

As described above, when judging the abnormality of the pump operation from the waveforms of a plurality of continuous processes, the abnormality that can occur depending on the pump and the way of displaying the pressure waveform are different.
However, this case is also reproducible and is generally applicable to other abnormalities.

Next, an embodiment in which the present invention is applied to a double plunger type pump will be described.

The double-plunger pump realizes liquid transfer with less pulsation by shifting the movements of the two plungers by a half cycle.

 Figure 10 shows a double-plunger pump.

The outlets of the two pump heads 2a and 2b are the flow paths 3
And the inlet sides of the pump heads 2a and 2b are connected to the reservoirs, respectively.

An inlet side check valve 34a is provided on the inlet side of the pump head 2a, an outlet side check valve 36a is provided on the outlet side, and an inlet side check valve 34b is provided on the inlet side of the pump head 2b.
Is provided, and an outlet side check valve 36b is provided on the outlet side. These check valves 34a, 34b, 36a, 36b act so that the liquid flows only in one direction from the inlet side to the outlet side of the pump heads 2a, 2b.

The pump head 2a is provided with a plunger 40a capable of reciprocating with a seal 42a preventing liquid leakage, and the pump head 2b has a plunger 42b capable of reciprocating with a seal 42b preventing liquid leakage. It is provided in. The plunger 40a and 40b reciprocate with a half cycle shift to perform the liquid feeding operation.

This double plunger type pump is arranged in place of the pump 2 shown in FIG.

FIG. 11 (A) shows the moving speed of the plungers 40a and 40b. The upper side is the discharge side and the lower side is the suction side.
44a is for plunger 40a, 44b is for plunger 4
It is about 0b.

When this double-plunger pump is operating normally, the discharge pressure detected by the pressure sensor 18 (see FIG. 2) has a waveform as shown in FIG. 11 (B).

Frequent pump failures include those in which the check valve does not function properly due to scratches or dust on the check valve. Figure 12 to
Figure 15 shows the discharge pressure detection waveform when the check valve is not operating properly.

FIG. 12 shows the case where the outlet valve 36b of the pump head 2b is scratched, FIG. 13 shows the case where the inlet valve 34a of the pump head 2a is scratched, and FIG. 14 shows the case where the outlet valve 36a of the pump head 2a is scratched. FIG. 15 shows the case where the inlet valve 34b of the pump head 2b is damaged. That is, FIG. 12 and FIG.
As shown in the figure, when the outlet valve 36b of the pump head 2b or the inlet valve 34a of the pump head 2a has a flaw, a large decrease in pressure in the discharge section of the pump head 2a, that is, a lack of liquid delivery appears, As shown in FIGS. 14 and 15, when the outlet valve 36a of the pump head 2a or the inlet valve 34b of the pump head 2b is damaged, a large decrease in pressure appears in the discharge section of the pump head 2b. When such a characteristic pressure waveform is observed, a display to that effect is automatically made, so that the user can recognize that any valve needs to be repaired.

The operation of this example can be performed in the same manner as the procedure shown in FIG. However, in the characteristic extraction in step S4 and the comparison with the set value in step S5, the following operations are performed.

The discharge waveform is shown in FIG. 16, where A and B are each pump head 2a,
It is the displacement of the plunger from the start of discharge in the discharge period of 2b to the point where the pressure becomes minimum due to pulsation, or the rotation angle of the cam that drives the plunger. Time may be measured instead of the displacement of the plunger or the like. When the pump heads 2a and 2b are normal, A and B are almost equal. However, from Figure 12
When an abnormality as shown in FIG. 15 occurs, A becomes large and B becomes almost 0 as shown in FIG. 17, for example. Therefore,
If A >> B, it can be determined that the pressure drop has occurred during the discharge period of the pump head 2a, and if A << B, it can be determined that the pressure drop has occurred during the discharge period of the pump head 2b.
Therefore, it suffices to display the content and give a warning. And when A >> B, the outlet valve of the pump head 2b
36b or the inlet valve 34a of the pump head 2a is repaired, and A << B
In case of, the outlet valve 36a of the pump head 2a or the pump head 2
The inlet valve 34b of b may be repaired.

Further, by distinguishing the pressure waveforms in FIGS. 12 and 13, it is possible to display which of the outlet valve 36b of the pump head 2b and the inlet valve 34a of the pump head 2a is abnormal. The same applies to the discrimination between the waveforms in FIGS. 14 and 15. In order to make this distinction, A and B in FIG.
In addition to comparing the magnitude relationship between the two, the slope (y / x) when the pressure drops is detected.If the slope is steep, the outlet valve is abnormal.If the slope is gentle, the inlet valve is It may be determined that there is an abnormality and that fact is displayed.

(Effects of the Invention) According to the present invention, it is possible to automatically detect the presence / absence of an abnormality in the operation of a pump and which valve is located in which pump head and which abnormality location. It is possible to know an abnormality that could not be judged by the upper limiter and the lower limiter of the pressure, and the reliability of the target analysis data and the like is improved.

Further, the labor of the operator for judging the pressure waveform can be reduced, and the abnormality of the pump will not be overlooked.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing an embodiment, FIG. 3 is a pressure waveform diagram showing normal operation of the pump, and FIG. 4 is pressure showing abnormal operation of the pump. Waveform diagram, FIG. 5 is a diagram showing characteristics of pump operation, FIG. 6 is a flowchart showing operation of one application example, FIG. 7 is a pressure waveform diagram showing other characteristics of the pump, and FIG. 8 is pump abnormality. FIG. 9 is a pressure waveform diagram showing the operation, FIG. 9 is a flowchart showing the operation of another application example, FIG. 10 is a schematic diagram showing the double plunger type pump, and 11 (A) shows the moving speed of the plunger of the double plunger type pump. The figure, (B) is a diagram showing the detection waveform of the discharge pressure, FIGS. 12 to 15 are diagrams showing the detection waveform of the discharge pressure when the check valve operation is defective, and FIG. 16 is the discharge pressure. Fig. 17 shows the characteristics of Fig. 17, and Fig. 17 shows the discharge pressure when the check valve is not operating properly. Is an enlarged view showing a detection waveform. 2 ... Pump main body, 2a, 2b ... Pump head, 4 ... Measuring means, 6 ... A / D converter, 8 ... Memory, 10 ... Characteristic extraction section, 12 ... Setting section, 14 ... Comparison / judgment part, 16 ... Display part.

Claims (1)

(57) [Claims] 1. A liquid feed pump main body of a double plunger type pump having two pump heads arranged in parallel, a means for measuring the discharge pressure of the liquid feed pump main body, and a signal from the measuring means as a digital signal. Convert to A / D
The converter and the memory that captures and stores the output of this A / D converter at fixed time intervals or every cycle, and the stored contents of this memory, the pressure due to the pulsation from the start of discharge in the discharge period of each pump head. The displacement of the plunger up to the point where is the minimum, the rotation angle of the cam that drives the plunger, or the time is extracted as the operating characteristics of the pump, and the characteristic extraction unit that detects the slope of the pressure drop due to the pulsation and the pump head The size of the operating characteristic of each pump head is compared by comparing the operating characteristic extracted by the characteristic extracting unit with the setting condition of the establishing unit, and the setting unit that sets the degree of difference in the operating characteristic as the setting condition. Of the pressure drop due to the pulsation and the magnitude of the slope of the pressure drop. A liquid delivery pump comprising a comparison / determination unit that determines whether the valve is an inlet valve or an outlet valve of the head, and a display unit that displays the determination result of the comparison / determination unit.