JP2564588B2 - Low pulsating flow pump device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a low pulsation pump device, and more particularly to a low pulsation pump device suitable for performing highly sensitive analysis such as liquid chromatography.

[Conventional technology]

When performing high-sensitivity analysis with a liquid chromatograph, low pulsating flow is a major point. The mechanism of liquid transfer pump of liquid chromatograph is that the motor rotates the cam shaft, and the cam reciprocates the plunger to continuously suck the solution by the action of the valves provided at the suction port and the discharge port.・ It is intended to be discharged. In this case, the discharge pressure is 40
Since it reaches 0 to 500 kgf / cm ² , the liquid is compressed during the process from suction to discharge, and the discharge amount is temporarily reduced, so that pulsating flow occurs. Further, when air bubbles are mixed in this flow path system, a larger pulsating flow is generated.

In order to reduce such a film flow, a method has been adopted in which the speed of the plunger is diligently controlled so as to reduce the pressure ripple while monitoring the discharge pressure. As a typical example of such a control method, for example, Japanese Examined Patent Publication No. 61-3262
As disclosed in Japanese Patent Publication No. 0, there are a control method based on a learning function (hereinafter referred to as learning control) and a control method based on real time (hereinafter referred to as real time control).

The learning control refers to the pressure pattern of the previous cycle and sequentially changes the rotation speed and the phase of the motor for each cycle while learning (trial and error) in the direction in which the pressure fluctuation (pulsation) decreases. Is the way. In this method, if the flow rate, pressure, and solvent are uniform, the pulsating flow will decrease with time, and very stable liquid transfer can be realized. In addition, the response delay of the pressure measurement system and the response delay of the motor control do not matter.

The real-time control is a method of detecting the decrease or increase of the pressure while monitoring the pressure, controlling the rotation speed of the motor and controlling the phase in real time, and restoring the pressure to the original level. In this case, it is possible to respond to a change in the system in a short time, and it is possible to suppress a relatively small pulsating flow even when a sudden bubble is mixed.

[Problems to be Solved by the Invention]

However, the learning control described above is based on the premise that the same pressure pattern as that of the previous cycle is obtained.
It has the drawback of being weak against changes in the system such as changes in flow rate and inclusion of bubbles.

Further, the real-time control has a drawback that a pulsating flow is always left due to a delay in response of the pressure measurement system and a delay in response of the motor control system.

As described above, the low pulsation control methods have their respective advantages and disadvantages. Further, there are various kinds of analysis purposes and methods of the liquid chromatograph, and there is a problem that one analysis method cannot be covered by one pulsation control method.

An object of the present invention is to provide a low pulsating flow pump device capable of selecting an optimal control method according to the situation and enabling high sensitivity analysis.

[Means for solving the problem]

In order to achieve the above-mentioned object, a low pulsating flow pump of the present invention comprises a drive means, a plunger that is reciprocated by the drive means to feed a liquid, a pressure detection means that detects the discharge pressure of the plunger, and a learning control. Low-pulsation algorithm for the learning control or low-pulsation algorithm for the real-time control according to the pressure signal from the pressure detection means. The selection means for selecting one of the optimum pulsation reduction algorithms among the optimization algorithms, and the control means for controlling the drive means by this algorithm.

[Action]

According to the above configuration, if a plurality of pulsation reducing algorithms are built in the control means in advance, and the pulsation reducing algorithm most suitable for the pattern of the discharge pressure of the plunger is selected from among them, the pulsation reduction is achieved. Since the control means controls the drive means based on the algorithm, it becomes possible to suppress the pulsating flow of the discharge pressure.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall structure of a low pulsating flow pump device according to the present invention. In the figure, a cam shaft 2 is arranged in parallel with the stepping motor 1, and a pair of cams 3 are fixed to the cam shaft 2. One end of a pair of plungers 4 is in contact with the cam surfaces of the pair of cams 3, and a first cylinder 5 and a second cylinder 6 are arranged at the other ends of the plungers 4, respectively. Further, the first cylinder 5 is provided with a suction valve 5A and a discharge valve 5B. The suction valve 5A is connected to the container 8 via the pipe 7, and the discharge valve 5B is connected to the second cylinder 6 via the pipe 9. Further, a pipe 10 is connected to the second cylinder 6, and a pressure sensor 11 is provided in the middle of the pipe 10. The pressure sensor 11 is connected to the control unit 12,
The control unit 12 is connected to the stepping motor 1 via a motor drive unit 13. The control unit 12 incorporates two algorithms, a learning control and a real-time control, as a pulsating control method. Further, 14 is a switch for selecting one of the above two algorithms, 15 is a photo interrupter fixed to the cam shaft 2, and both the switch 14 and the photo interrupter 15 are connected to the control unit 12.

The stepping motor 1, the cam 3 and the like constitute driving means, the pressure sensor 11 constitutes pressure detecting means, and the control section 12, the motor driving section 13 and the switch 14 constitute control means.

 Next, the operation of this embodiment will be described.

When the cam 3 is rotated by the rotation of the stepping motor 1, the plunger 4 reciprocates by the rotation of the cam 3. Suction valve 5A and discharge valve due to reciprocating motion of plunger 4.
5B is opened and closed, and the solution in the container 8 is sucked into the first cylinder 5. The sucked solution is compressed in the cylinder 5 and is discharged to the outside through the second cylinder 6. During this compression, the discharge from the first cylinder 5 is interrupted, so that the total discharge amount decreases, which causes a pulsating flow.

Therefore, in the present embodiment, a method is adopted in which the pulsating flow is reduced by operating the stepping motor 1 at high speed in the compression section of this solution. The magnitude of the pulsating flow largely depends on the start and end timings of the high-speed operation control of the stepping motor 1. Therefore, with proper control, it is possible to eliminate pulsating flow.

Here, the control method for reducing the pulsating flow in this embodiment will be described with reference to FIG.

Two types of control methods, learning control and real-time control, are stored in the memory 17 in advance. Further, the phase of the cam 3 is detected by the photo interrupter 15, and the detection signal is transmitted to the control unit 12, so that the control unit 12 can know the high-speed operation section (solution compression section) of the stepping motor 1 from this signal. . At the same time, the discharge pressure is detected by the pressure sensor 11, the detection signal is transmitted to the control unit 12 via the A / D converter 16, and the control unit 12 detects the discharge pressure by this signal. Then, while judging the state of the discharge pressure, a person turns ON / OFF the switch 14 to select the most suitable control method from the above two kinds of control methods. The control unit 12 sends a control signal to the motor drive unit 13 based on the selected control method. The motor driving unit 13 drives the stepping motor 1 according to the control signal.

The determination of which of the above two control methods is optimal is selected according to the type of analysis method.

For example, in learning control, whether the flow rate and discharge pressure are almost constant,
Alternatively, it is suitable for a so-called isocratic method, which is a means for performing analysis while relatively slowly changing. This is because the pump suction / discharge cycle can be expected to be reproduced in the same pattern as the previous cycle.

On the other hand, the real-time control is suitable for a so-called gradient method, which is a method of analyzing while changing the composition and flow rate of the solvent. This is poor in reproducibility such that the compressibility changes when the composition of the solvent changes, and the pressure changes when the flow rate changes, and when water and methanol are used as the solvent, bubbles are generated in the solution. This is because the compression rate changes greatly.

Data obtained by actually performing the above two control methods for the case where the discharge pressure pattern has reproducibility and the case where the discharge pressure pattern does not have reproducibility are shown in FIGS. 3 and 4.

When the discharge pressure pattern has reproducibility as shown in FIG. 3A, the learning control causes the pulsating flow to be gradually reduced as shown in FIG. However, according to the real-time control, the same figure (c)
As shown in, the pulsating flow cannot be completely eliminated.

Further, when the discharge pressure pattern is not reproducible as shown in FIG. 4 (a), learning control makes it impossible to reduce the pulsating flow as shown in FIG. 4 (b). According to the real-time control, the pulsating flow cannot be completely eliminated, but can be reduced, as shown in FIG.

According to the present embodiment, if the pattern of the discharge pressure has reproducibility, it is controlled by the learning control, and if it does not have reproducibility, it is controlled by the real-time control, so that the pulsation of the discharge pressure becomes extremely small.

The content of the pulsation reduction algorithm is assembled as shown in the flowchart of FIG. This will be described. First, in step 30, the rotation speed of the motor is obtained from the set flow rate, and the motor is operated. In step 31, it is judged from the signal from the photo interrupter whether or not the cam is at the origin, and if it is at the origin, the discharge pressure at that time is read out in step 32, and this discharge pressure is used as the reference pressure within the cycle. Next, in step 33, it is judged whether or not the vehicle is in the high speed operation section.
The discharge pressure at that time is read with. Then, in step 35, the discharge pressure is compared with the reference pressure, and if the discharge pressure is lower than the reference pressure, the rotation speed of the motor is increased in step 36,
If it is higher, the motor speed is returned to the set number of points in step 37. Next, in step 38, it is judged whether or not it is in the high speed operation section. If it is in the high speed operation section, go to step 34 and repeat the steps 34 to 37. If the high speed operation section is over, go to step 30. Set the rotation of the motor to the set speed,
This cycle ends. The above process is repeated as one cycle.

〔The invention's effect〕

As described above, according to the invention of the present application, one of the optimum pulsation reduction algorithms, which is the low pulsation reduction algorithm for learning control or the low pulsation reduction algorithm for real-time control, is selected. Since the low pulsation pump is provided with a selection means for this, it is possible to select the pulsation reduction algorithm most suitable for the pattern of the discharge pressure of the plunger, and it is possible to suppress the pulsation flow of the discharge pressure.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a low pulsation pump device according to the present invention,
FIG. 2 is a control block diagram for controlling the low pulsation pump of FIG. 1, and FIG. 3 is a waveform diagram of discharge pressure when learning control and real-time control are performed for reproducible pulsating flow. Four
FIG. 5 is a waveform diagram of the discharge pressure in the case of learning control and in the case of real-time control for a non-reproducible pulsating flow, and FIG. 1 ... Stepping motor, 2 ... Cam shaft, 3 ... Cam, 4 ... Plunger, 5 ... First cylinder, 5A ... Suction valve, 5B ... Discharge valve, 6 ... Second cylinder, 7, 9,10 ... Piping, 8 ... Container, 11 ... Pressure sensor, 12 ... Control section, 13 ... Motor drive section, 14 ... Switch, 15 ... Photo interrupter, 16 ... A / D converter , 17 …… Memory.

Claims (1)

(57) [Claims] 1. A driving means, a plunger that reciprocates by the driving means to feed a liquid, a pressure detecting means that detects a discharge pressure of the plunger, a low pulsation algorithm for learning control, and a low for real-time control. An pulsating algorithm is built-in, and depending on a pressure signal from the pressure detecting means, either the pulsating algorithm for the learning control or the pulsating algorithm for the real-time control is optimally reduced. A low pulsating flow pump device comprising: a selection means for selecting one algorithm, and a control means for controlling the driving means by this algorithm.