JP3345229B2 - Dispensing pump system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixed-quantity liquid-feeding pump system used in a liquid chromatography apparatus or the like to precisely and precisely supply a predetermined amount when a small amount of liquid is intermittently supplied. .

[0002]

2. Description of the Related Art In a liquid chromatography apparatus, it is required to feed an eluent at a constant rate, and for that purpose, it is usual to provide a quantitative liquid sending pump system using a piston reciprocating pump.

[0003] However, the piston reciprocating pump has a problem in that the flow rate of the supplied liquid changes with the fluctuation of the liquid supply pressure.

Accordingly, the applicant of the present invention has previously determined a liquid flow rate in real time and feeds it back to the pump, whereby a predetermined fixed amount of liquid can be fed with high accuracy. (See JP-A-2-213729).

[0005] FIG.
Shown in In the figure, 1 is a detector, 2 is an amplifier, 3 is a differentiator,
4 is an auto-zero circuit, 5 is a calculator, 6 is a control device, 7 is a pulse generator, 8 is a stepping motor (hereinafter simply referred to as a motor), 9 is an input / display, 10 is a pump, 11
Is a plunger, 12 is a cylinder chamber, 13 is a suction valve, 14
Denotes a discharge valve, 21 denotes an optical detector, and 31 denotes an electrical detector.

[0006] A detector 1 is provided in the pipeline on the suction side of the pump 10.
Is provided. Although various types of detectors 1 can be used, the detector shown in FIG. 5 is used here.

The detector 31 shown in FIG. 5 is of a type for electrically detecting the flow of a liquid. A heating element 32 having a small heat capacity and containing a platinum resistance element or the like is installed in a conduit 35, This has a configuration in which a current source 33 and a voltage detector 34 are connected. According to this configuration, when the liquid flows, the heat of the heating element 32 is taken away by the liquid, and the resistance value of the heating element 32 changes, so that the flow of the liquid can be detected as a voltage signal.

The detection signal from the detector 1 is transmitted to the amplifier 2
, And differentiated by the differentiator 3, and further input to the auto-zero circuit 4. The output of this auto-zero circuit 4
An impulse signal of the flow timing signal is obtained.

The flow timing signal is input to a calculator 5, which calculates the actual flow time of the liquid, that is, the suction time, based on the flow timing signal, and uses the flow time and various parameters. To determine the flow rate Q of the liquid.

The arithmetic unit 5 controls the obtained flow rate Q of the liquid
Pass to. The control device 6 sets a preset flow rate target value Q
The difference e (=) between _i and the actual flow rate Q of the liquid received from the arithmetic unit 5
Q _i -Q).

The difference e is a loss of suction. That is,
Originally because it did only only be inhaled Q by the should intake only flow target value Q _i is the liquid feed pressure is varied, the difference e will become one loss in.

Then, the controller 6 determines a flow rate (Q _i + e) to be further corrected, replaces the corrected flow rate value (Q _i + e) with a new flow rate target value Q _i, and The pulse generator 7 generates a pulse that only allows the flow rate of
To instruct.

[0013] Since a drive pulse is generated only the pulse generator 7 is instructed by this, the plunger 11 of the pump 10 will flow a flow rate of the new flow rate target value Q _i.

By repeating the above steps, a predetermined amount of liquid can be sent.

[0015]

In the above-mentioned conventional fixed-rate liquid supply pump system, the actual suction time is detected, the flow rate Q of the liquid is determined from the suction time, and the corrected flow rate is further determined. Since the amount of the liquid to be corrected is corrected, the correction is performed in the next cycle after the cycle in which the suction time is detected.

That is, the fixed-quantity liquid supply pump system cyclically repeats the suction step and the discharge step. If the suction time is detected in the suction step of the current cycle, the suction time detected in the suction step is determined. Is corrected in the suction process of the next cycle.

However, in the method of correcting the inhalation loss in the next cycle as described above, in a certain inhalation step, the amount of the inhalation loss in the previous inhalation step is added to the amount to be inhaled in the inhalation step. Since the liquid must be sucked, there is a problem that the amount of liquid to be supplied fluctuates greatly and a so-called hunting phenomenon may occur. This is particularly remarkable when the amount of inhalation is greatly reduced for some reason and the loss of inhalation is increased.

The present invention solves the above-mentioned problems, and a fixed-quantity liquid-feeding pump system capable of correcting flow loss without realizing a hunting phenomenon in a more real-time manner than before. The purpose is to provide.

[0019]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, a quantitative liquid sending pump system according to the first aspect of the present invention provides a quantitative liquid sending pump by cyclically repeating a suction step and a discharging step. In the fixed volume pump system, the liquid actually flows after the suction process starts.
The method is characterized in that a loss of liquid supply is detected from the time until the start , and the detected loss is corrected in a cycle in which the suction step or the discharge step is performed. Further, Metering pump system of claim 2, wherein, in the Metering pump system for quantitative feeding by repeating the suction stroke and discharge stroke cyclically, sucking step or
A waiting time is provided after the discharge process, and a loss amount that could not be sent during the suction process or the discharge process is detected,
The detected loss is corrected within the waiting time .

According to the first and second aspects of the present invention, the loss of the liquid feed is corrected in the cycle in which the loss is detected, so that the real-time property of the correction is improved as compared with the related art. In addition, since there is no influence on the next cycle, it is possible to prevent a large change in the amount of liquid to be sent, and therefore, the hunting phenomenon does not occur unlike the conventional case.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of the configuration of a fixed-rate liquid supply pump system according to the present invention. In the figure, 40 is a buffer, 41 is a switch, 42 is a capacitor, 43 is a differential amplifier, 44 is a buffer, and 45 is a switch. , 46 are capacitors, 47 is a comparator, 48 is a flip-flop (hereinafter referred to as FF), 49 is a counter, 50
Denotes a control device, and 51 denotes a diode. Note that the same components as those shown in FIG. 4 are denoted by the same reference numerals.

First, each circuit shown in FIG. 1 will be described with reference to the timing chart of FIG. A detector 1 is provided in a feed line on the suction side of the pump 10. Detector 1
Various types can be used, but here, the configuration shown in FIG. 5 is used.

The buffer 40, switch 41, and capacitor 42 form an auto-zero circuit. This switch 4
Although the first opening and closing is controlled by the control signals S ₁ from the controller 50, as shown in FIG. 2 (C), is closed momentarily at the start of the discharge process, the detector 1 of the output voltage capacitor 42 at that time Is held. Therefore, a differential voltage between the voltage held by the capacitor 42 and the subsequent output voltage of the detector 1 is obtained from the differential amplifier 43. This difference voltage is obtained by clamping the output voltage of the detector 1 at the start of ejection to 0V.

The reason for providing such an auto-zero circuit is that, in the detector shown in FIG. 5, the output voltage is subject to drift for a long time due to various factors such as the liquid temperature of the liquid, the ambient temperature of the liquid, and the viscosity of the liquid. This is to cancel the drift. That is, since the voltage at the start of the ejection process is held in the capacitor 42,
Therefore, the differential amplifier 43 always outputs a signal from which the drift has been removed over a long period of time, with the start of ejection as the reference voltage (0 V).

The buffer 44, the switch 45, the capacitor 46, the diode 51 and the comparator 47 constitute a peak detecting circuit for detecting the peak of the output signal of the detector 1. This closing of the switch 45 is controlled by a control signal S ₂ from the control unit 50, as shown in FIG. 2 (D), is closed only during the period from the start of the discharge process to the start of the suction stroke, other periods Is made open. Therefore, the capacitor 46 holds the peak voltage of the signal during the period when the switch 45 is closed via the diode 51.

The voltage of the capacitor 46 is input to one input terminal of the comparator 47, and the output voltage of the differential amplifier 43 is input to the other input terminal. A predetermined offset voltage V _OS is superimposed on the latter.

The comparator 47 compares the two input voltages and outputs a pulse when the two input voltages match. The operation of the comparator 47 will be described below with reference to FIG.

The output voltage of the detector 1 gradually increases when no liquid is flowing, but decreases when the liquid starts flowing. That is, when the liquid starts flowing, the output voltage of the detector 1 reaches a peak.
A voltage obtained by superimposing the offset voltage V _OS on the output voltage of the differential amplifier 43 is applied to one of the input terminals as shown by the solid line in FIG. As indicated by the broken line, the voltage of the capacitor 46 which holds the peak voltage of the output voltage of the differential amplifier 43 is applied and the comparison is performed. According to this, when the two input voltages match, the output of the comparator 47 outputs a pulse as shown in FIG. 3 (B), so this time is taken as the peak position of the output voltage of the detector 1 and It can be said that it has begun to flow.

The FF 48 receives a control signal S from the control device 50.
Set by ₃ and reset by the output pulse of comparator 47. The control signal S ₃ is generated when the suction process is started as shown in FIG. 2 (E).

The counter 49 starts counting the drive pulses of the motor 8 input from the pulse generator 7 when the FF 48 is set, ends counting when the FF 48 is reset, and outputs the count value to the control device 50. Notify.

It is clear that the count value of the counter 49 corresponds to the loss that could not be sucked. That is,
The period during which the driving pulse from the pulse generator 7 is counted by the FF 48 is a period from the start of the suction step until the liquid actually starts to flow as shown in FIG. Therefore, the count value of the drive pulse during this period corresponds to the flow rate that should be sucked as it is but was not sucked but was lost. As described above, in the fixed-quantity liquid supply pump system shown in FIG. 1, the loss of liquid supply is detected as the stroke length of the plunger 11.

As described above, each circuit in FIG. 1 has been described.
Next, the overall operation will be described. As shown in FIG. 2 (B), in this fixed-quantity liquid supply pump system, a waiting time is provided between the suction step and the discharge step, and the loss that cannot be suctioned during this waiting time is corrected. Has been made.

Now, as shown in FIG. 2, assuming that the discharge process is started at t ₀ , the switch 41 is switched to the state shown in FIG.
It is closed only for a short time as shown in FIG. Since the liquid on the suction side of the pump 10 is not flowing at this time, the output voltage of the differential amplifier 43 increases from 0 V as shown in FIG. In addition, at the start of the discharge step, FIG.
The switch 45 is also closed as shown in FIG.

Thereafter, the discharge step is completed (t ₁ ) and the suction step is started. At this time, the switch 45 is opened. At this time, since the FF 48 is set, the counter 49 starts counting the driving pulses from the pulse generator 7. At this time, since the liquid on the suction side of the pump 10 has not started flowing, the output voltage of the differential amplifier 43 is
It continues to increase gradually as shown in FIG.

Thereafter, at time t ₂ , the liquid on the suction side of the pump 10 starts flowing, and when the output voltage of the differential amplifier 43 reaches a peak, a pulse is output from the comparator 47 as shown in FIG. Since the FF 48 is reset as shown in FIG. 2 (G), the counter 49 ends the counting of the drive pulse and notifies the control device 50 of the count value.

When the suction step is completed at time t ₃ , a waiting time is entered. During this waiting time, the control device 50 instructs the pulse generator 7 to drive the pulse having the count value notified from the counter 49 to the pulse generator 7. Is generated.

In accordance with this, the pulse generator 7 generates the number of drive pulses specified by the control device 50 to generate the motor 8
, The plunger 11 performs the suction operation for the number of drive pulses. Therefore, by this suction operation, t
It is possible to suck the amount of loss in that could not be sucked into ₁ ~t ₂ times. In FIG. 2A, t within the waiting time
It has done this correction operation in time of ₄ ~t _5.

In other words, in this fixed-quantity liquid-feeding pump system, the correction of the detected loss of the liquid-feeding is corrected within the cycle in which the loss is detected.

When the correction operation is completed and the waiting time has elapsed, the ejection process is started again (t ₆ ), and the above-described operation is repeated.

In FIG. 2A, the flow of the liquid is temporarily stopped on the suction side of the pump 10 from t ₃ to t ₄ from the end of the suction step to the start of the correction operation. Although the output voltage of the amplifier 43 actually rises, this time is extremely short, so that it is described in the drawing that the voltage is maintained at a substantially constant value.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above example, the detector 1 is provided on the suction side of the pump 10, but it is apparent to those skilled in the art that the detector 1 may be provided on the discharge side. And
In this case, a waiting time may be provided between the discharge step and the next suction step, and the loss that could not be discharged in the immediately preceding discharge step during the waiting time may be corrected.

The pump 10 is not limited to the one having the configuration shown in the figure. For example, the drive unit of the plunger 11 can use not only a rotary type motor schematically shown in FIG. 1 but also a linear type step motor.

The peak detection circuit is not limited to the configuration shown in FIG. 1. For example, the signal may be converted into a digital signal using an A / D converter and then subjected to computer processing or a digital peak detection circuit to detect the peak. Is also good.

As is clear from the above description, according to the above-described fixed-quantity liquid-feeding pump system, the liquid-feeding loss is corrected in the same cycle in which the loss is detected, so that the following method is used, as in the prior art. There is no effect on the cycle, and not only can the liquid be sent more stably, but also no hunting phenomenon occurs unlike the conventional case.

Further, in the conventional fixed-quantity liquid-feeding pump system shown in FIG. 4, the differentiator 3 is used to find the peak of the output voltage of the detector. There has been a problem that the position detected as a peak becomes unstable due to the variation due to the above, but since the differentiator is not used in the circuit configuration shown in FIG. 1, the peak position can be detected stably. .

The differentiator 3 sometimes malfunctions due to various kinds of noises such as external noises. However, this is not the case in the circuit configuration shown in FIG. 1, and the noise resistance is improved as compared with the prior art. I have.

Further, in the conventional fixed-quantity liquid feeding pump system, complicated calculations are performed to find the flow rate to be corrected. In this fixed-quantity liquid sending pump system, a pulse generator for driving the motor 8 is used. Since the loss of liquid feed, that is, the flow rate to be corrected, is obtained by a very simple method of counting the drive pulses generated from 7,
Correction can be performed more accurately than in the past.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a fixed-quantity liquid sending pump system according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the fixed-quantity liquid feeding pump system shown in FIG.

FIG. 3 is a diagram for explaining the operation of the peak detection circuit.

FIG. 4 is a diagram showing a configuration example of a fixed-quantity liquid feeding pump system proposed by the present applicant previously.

FIG. 5 is a diagram illustrating a configuration example of a detector 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Detector, 2 ... Amplifier, 3 ... Differentiator, 4 ... Auto-zero circuit, 5 ... Operation unit, 6 ... Control device, 7 ... Pulse generator,
8 stepping motor, 9 input / display, 10 pump, 11 plunger, 12 cylinder chamber, 13 suction valve, 14 discharge valve, 31 detector, 40 buffer
41 switch, 42 capacitor, 43 differential amplifier, 44 buffer, 45 switch, 46 capacitor, 47 comparator, 48 flip-flop, 49 counter, 50 control device.

Continuation of the front page (56) References JP-A-63-259183 (JP, A) JP-A-2-213729 (JP, A) JP-A-58-208629 (JP, A) JP-A-61-166176 (JP, A) , U) JP 53-43421 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 1/00 G01F 11/00-13/00 G01N 30/00 G01N 35/00

Claims (2)

(57) [Claims] In a constant-quantity liquid supply pump system for performing a constant-quantity liquid supply by cyclically repeating a suction step and a discharge step, a period from when the suction step is started until the liquid actually starts flowing.
A fixed-quantity liquid-feeding pump system, wherein a liquid-feeding loss is detected from time, and the detected loss is corrected in a cycle in which the suction step or the discharging step is performed. 2. A fixed-quantity liquid-feeding pump system for performing a constant-quantity liquid-feeding operation by cyclically repeating a suction step and a discharge step, wherein a waiting time is not provided after the suction step or the discharge step.
A pump that detects a loss that could not be sent during the suction step or the discharge step , and corrects the detected loss within the waiting time .