JPH0693974A - Trace flow rate pump - Google Patents

Abstract

PURPOSE:To provide a technology through which a specified amount or less of a flow rate is continued to be stably fed to a column, in a trace flow rate pump for a liquid chromatograph. CONSTITUTION:A trace flow rate pump is formed of a base plate part comprising a piezoelectric element 1, a plunger 2, and a cylinder 3. Fluid is sucked and delivered through the change of the volume of a plunger in the cylinder by means of a voltage applied on the piezoelectric element. High speed control the speed of which is approximate 100 times as fast as that of a conventional motor-operated pump is practicable and the generation of a pressure fluctuation ripple can be reduced through coping at a high speed with a fluctuation in a flow rate.

Description

Detailed Description of the Invention

[0001]

It is used as a sample delivery means in an analyzer, and is most suitable for a fine flow rate pump in a liquid chromatograph analyzer.

[0002]

2. Description of the Related Art Conventionally, a pump in a liquid chromatograph analyzer needs to deliver a sample at a high pressure. A motor is used as a power source and a plunger is reciprocated in the cylinder to reciprocate the sample in the cylinder. Is inhaled and delivered. However, when the number of cylinders is one, the sample cannot be delivered during inhalation, and the delivered flow rate becomes a pulsating flow.
Therefore, by combining the two cylinders, while one cylinder is inhaling, the remaining one cylinder is operated so as to deliver, thereby reducing the pulsating flow.

[0003]

Due to the high sensitivity of the liquid chromatograph analyzer, it becomes possible to perform measurement with a small amount of sample, and the amount of sample delivery has been reduced. Fine flow rate control has become difficult with conventional pumps that rely solely on motors as power sources. In particular, in the above-mentioned two cylinder operations, there is a need for a technology for correcting the flow rate fluctuation occurring at the time of switching between suction and delivery and the flow rate fluctuation due to the accuracy limit of the moving amount of the plunger at a high speed and with high accuracy. ing. It is an object of the present invention to provide a high pressure pump that responds to an electric signal at high speed and can be controlled with high accuracy, and to provide a pump that stably controls a minute flow rate.

[0004]

According to a first aspect of the present invention, for example, a plunger is fixed to a piezoelectric element, and a volume change of the piezoelectric element results in a volume change of the plunger inside the cylinder.
An example of this structure is shown in the principle diagram of the minute flow rate pump in FIG. If the applied voltage is changed so that the volume of the piezoelectric element is reduced by connecting the suction valve to the suction side and the discharge valve to the delivery side, the volume of the plunger in the cylinder decreases and the pressure in the cylinder decreases. The downward discharge valve is closed, the suction valve is opened, and the sample is sucked into the cylinder. Next, when the applied voltage is changed so that the volume of the piezoelectric element increases, the volume of the plunger in the cylinder increases, the cylinder internal pressure rises, the suction valve closes, and the discharge valve opens, which causes the sample in the cylinder to discharge the discharge valve. Sent out.

According to a second aspect of the present invention, the fine flow rate pump is arranged between the output of the main pump for delivering the sample and the load, and the plunger is controlled to be taken in and out of the cylinder so that the pressure value of the output becomes constant. An example of such a configuration is shown in the fine flow rate correction pump configuration diagram of FIG.

[0006]

The piezoelectric element according to the present invention may be made of, for example, a laminated ceramic. Applied voltage is about 600
By changing about V, 6 with an accuracy of 0.1 μm or less
A product that has a displacement of 0 μm and generates a force of 11 KN or more has been commercialized. The response of displacement to voltage change is 1
Since it is 00 μsec or less, control from DC to 10 KHZ or more can be freely performed. On the other hand, the conventional technique using the motor is excellent in that the generated force and the displacement amount can be increased, but is inferior in the small displacement controllability for controlling the minute flow rate with high accuracy and the high-speed response.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is shown in the fine flow rate pump configuration diagram of FIG.

[0008] A suction valve of 4 and a sample is sucked through the suction valve and is discharged through a discharge valve of 5, and a fine flow pump of 10 and a sample from the discharge valve of 5 are sucked and sent to a load. 11 minute flow pump 2 and 11 minute flow pump 2
12 pressure sensors for measuring flow path pressure between loads, 1
15 pump control circuits that generate control signals for the fine flow pumps 1 and 2 of 10, 11 by the setting signal of the flow rate setting circuit of 6 and the signal from the pressure sensor of 12, and a voltage according to the control signal amount. 13 voltage generating circuits 1 that are generated,
It is configured by 14 voltage generation circuits 2. The minute flow pumps 1 and 2 of 10 and 11 are composed of a piezoelectric element 1 shown in the principle diagram of the minute flow pump of FIG. 1, a plunger 2 and a cylinder 3 respectively. In the relationship diagram between the control signal and the cylinder plunger volume in FIG. 4, 15 pump control circuits OUT
2 shows the relationship between the control signals output from the Nos. 1 and 2 and the in-cylinder plunger volumes of the minute flow pumps 1 and 10. 5 and 6 show control signals for the pumps 2 and 1 during operation. FIG. 7 shows operation states corresponding to the sections a to d in the control signals of FIGS. The operation of one embodiment is shown by the above figures. In the case of the present embodiment, it functions by repeating four operating states by the movement of the plungers of the two minute flow rate pumps 1 and 2, and the movements of the suction valve and the discharge valve. The section indicated by a in FIG. 5 is the state shown by the operation in the section a in FIG. 7, and the control signal is changing in the decreasing direction as shown in FIG. Since the first plunger operates in the direction to go out of the cylinder, the suction valve opens and the sample solution is sucked. Since the control signal of the pump 2 is changing in the increasing direction, the second plunger moves into the cylinder of the pump 2 so that the pressure in the cylinder of the pump 2 rises, the discharge valve is closed, and the inside of the pump 2 is closed. Sample is sent out to the outside by the volume of the second plunger entering the cylinder. Next, in the operation of the section b, only the control signal of the pump 1 changes from the decreasing direction to the increasing direction. As a result, the internal pressure of the pump 1 rises and the suction valve closes. The pump 2 delivers the sample similarly to the section a.
Next, the operation of section c starts. In the section b, the discharge valve opens when the internal pressure of the pump 1 becomes equal to or higher than the internal pressure of the pump 2, and the sample of the pump 1 is pushed out to the pump 2. In this section, the amount delivered to the outside is the sum of the pumps 1 and 2 pushing out.
In the case of keeping the sending amount constant, the change amount of the control signal is made small as shown in FIG. In the next section d, the control signal of the pump 2 is changed in the decreasing direction so that the sample sucked by the pump 1 is sucked into the pump 2. At the same time, since it is necessary to send the signal to the outside, the increase rate of the control signal of the pump 1 becomes high as shown in d of FIG. During this time, the suction valve closes and the discharge valve opens. The above operations of a, b, c and d are repeated as one cycle. The amount of the sample delivered from the minute flow rate pump of this embodiment changes depending on how many times this one cycle is repeated within a fixed time. Further, in the present embodiment, by arranging a pressure sensor between the delivery port of the pump and the load, when the inflow resistance is stable as in a load column, for example, a liquid chromatograph column, the pressure fluctuation is
Since the flow rate fluctuates, it is possible to control the flow rate to the load to be constant by inputting the pressure signal from the 12 pressure sensors to the 15 pump control circuit in FIG.

According to the present embodiment, by combining two minute flow rate pumps, a minute flow rate (especially about 0.1 to 1 μm / min) can be obtained.
It is possible to provide a pump that stably delivers a minute flow rate centered on l 1.

FIG. 3 shows another embodiment of the present invention, which is an example in which the minute flow pump of the present invention is connected between the output of 20 main pumps and the load. A control signal is sent between the load and the fine flow rate pump by the signal from the 12 pressure sensor to the voltage generating circuit at 13 to operate so that the cylinder capacity of the fine flow rate pump increases as the pressure rises. ,
When the pressure is lowered and the pressure is lowered, the operation moves in the opposite direction to the above-mentioned operation to increase the pressure. According to the present embodiment, it is possible to provide a pump having a small pressure fluctuation by absorbing a slight pressure fluctuation of the pump output.

FIG. 8 shows an embodiment in which a piezoelectric element also functions as a plunger. In the present invention, when the volume displacement of the piezoelectric element is smaller than the compression displacement of the liquid, it cannot be delivered to the outside. This embodiment is one embodiment in which the displacement area of the piezoelectric element is expanded with respect to the capacity in the cylinder to realize a displacement larger than the amount of compression of the liquid to be delivered.

[0012]

【The invention's effect】

1. Maximum to minimum cylinder capacity of pump, or
It is possible to change from the minimum to the maximum at a high speed of 100 μsec or more with high precision, and it is possible to provide a pump capable of performing high-speed control about 100 times or more as compared with the conventional motor drive method.

2. High-speed control has become possible, and it has become possible to reduce pressure fluctuation ripples that could not be removed by conventional methods.

3. A motor and a reciprocating motion conversion mechanism are not required, which enables downsizing and cost reduction.

[Brief description of drawings]

FIG. 1 is a principle diagram of a minute flow rate pump.

FIG. 2 is a configuration diagram of a minute flow rate pump.

FIG. 3 is a fine flow rate correction pump diagram.

FIG. 4 is a graph showing a relationship between a control signal and an in-cylinder plunger volume.

5 is a graph showing a control signal of the minute flow rate pump 2 in the embodiment shown in FIG.

FIG. 6 is a graph showing a control signal of the minute flow rate pump 1 in the embodiment shown in FIG.

FIG. 7 is a diagram showing an operation in the embodiment shown in FIG.

FIG. 8 is a principle view showing another embodiment of the minute flow rate pump.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 2 ... Plunger, 3 ... Cylinder, 4 ... Suction valve, 5 ... Discharge valve, 6 ... O-ring, 7 ... Piezoelectric element electrode.

Claims (3)

[Claims] 1. A pump for delivering a small amount of liquid,
It has a cylinder means for sucking and delivering liquid, a voltage volume changing portion whose volume is changed by voltage, and means for changing the internal volume of the cylinder by the volume change of the voltage volume changing portion, and the amount of liquid delivered is changed by voltage. A micro-flow pump characterized by being controllable by a voltage applied to a volume changing part. 2. A fine flow rate pump according to claim 1, wherein the fine flow rate pump is arranged in the middle of the output of the main pump and the load part for feeding the liquid, and the fine flow rate can be controlled. 3. A minute flow rate pump characterized in that the voltage volume changing portion according to claim 1 has a structure which also serves as an inner wall of the cylinder, whereby contraction of the inner wall of the cylinder changes the inner volume of the cylinder.