JPH0754114B2 - Control method of liquid delivery pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention controls a liquid delivery pump capable of delivering a constant flow rate in a wide range of flow rates regardless of the type of liquid and the conditions under which the liquid is placed. Regarding the method.

[Prior Art] A constant flow rate liquid feed pump is used to feed a liquid at a constant flow rate.

Conventionally, as such a pump, for example, a double plunger type pump as shown in FIG. 4 has been used. In the figure, 1A and 1B are respectively first and second heart cams, and the shafts 2 of the respective cams are integrated as shown in FIG. 5 and fixed to the shaft of the motor 3. Further, the heart cams 1A and 1B jointly form a symmetrical shape with respect to the axis X as shown in FIG. 6 and are arranged 180 ° out of phase with each other, and the first and second rollers 4A and 4B come into contact with each other. is doing. The first one
The second rollers 4A and 4B are connected to the first and second plungers 5A and 5B, respectively. The first and second plungers 5A and 5B are the motor 3
The first and second heart cams 1A, 1 that rotate in synchronization with the rotation of the
By the movement of B, linear reciprocating movement is performed in the first and second pump chambers 6A and 6B, respectively. The movements of the first and second plungers are offset from each other by 180 °. For example, the first plunger 5A moves to the right (arrow PA), and the liquid moves from the liquid tank 7 to the first pump chamber 6A.
At the same time as being sucked in, the second plunger 5B moves leftward (arrow PB), and the liquid in the second pump chamber 6B is discharged to the outside. Next, the first plunger 5A moves to the left (arrow QA) to discharge the liquid in the first pump chamber 6A to the outside, and at the same time, the second plunger 5B moves to the right (arrow QB) to move from the liquid tank 7. The liquid is sucked into the second pump chamber 6B. In addition, 8a, 8 in the figure
b, 8c, 8d are balls that float or sink in the liquid passage to flow or stop the liquid by the movement of the plunger. Further, 9A and 9B are compression springs which bring the first and second plungers 5A and 5B into contact with the first and second heart cams, respectively. As described above, the first plunger 5A and the second plunger
Since the movement of 5B is carried out by 180 °, the first pump chamber 6A
The liquid is sucked and the liquid is discharged from the second pump chamber 6B at the same time, and further, the liquid is discharged from the first pump chamber 6A and the second pump chamber 6B is sucked at the same time. FIG. 7 (a) shows the state, in which the horizontal axis indicates time or the rotation angle of the cam, and the vertical axis indicates the displacement of the plunger, that is, the contact point between the plunger and the roller and the basic circle (FIG. 6F). ) And the distance. The solid line shows the displacement of the first plunger 5A, and the broken line shows the displacement of the second plunger 5B. SA1 and SA3 are the suction period of the first pump chamber 6A, SB1 and SB3 are the discharge period of the second pump chamber 6B, SA2 and SA4 are the discharge period of the first pump chamber 6A, and SB2 and SB4 are the suction period of the second pump chamber 6B. Indicates the period. FIG. 7 (b) shows the outflow amount of the liquid from the outflow passage to the outside per unit time, the solid line is due to the discharge in the first pump chamber, and the broken line is due to the discharge in the second pump chamber. Then, ideally, it should be parallel to the time axis, that is, a constant outflow amount. However, in reality, since pressure is applied to the discharge side of the pump, the suction (or discharge) step by the first plunger and the discharge (or suction) step by the second plunger are respectively discharge (or suction) step and suction (or suction) step. (Or discharge) process, there is a delay in the discharge of the liquid from the first pump chamber (or the second pump chamber) with respect to the displacement of the first plunger (or the second plunger). D1
As shown by D4, the outflow amount per unit time from the flow path of the first pump (or the second pump chamber) to the outside falls for a short time immediately after the process is changed. This phenomenon is because the pressure inside the pump chamber is close to zero at the time of suction, and when the process changes to the discharge process, the movement of the plunger tries to reach high pressure, but since pressure is applied to the discharge side of the pump, the pressure in the outflow passage outside the pump chamber is high. This is because it is not possible to immediately pass over the liquid, and until the cam and the plunger are displaced, there is no discharge of liquid from the pump chamber to the outflow passage. If the measurement column of the liquid chromatograph device is connected to the outside of the outflow channel due to the decrease in the outflow amount, pulsation occurs in the baseline of the spectrum of the measurement result, which hinders accurate measurement. In particular, this phenomenon becomes remarkable as the pressure in the outflow passage outside the pump chamber increases.

The accuracy of the constant flow rate with respect to the pressure resistance can be improved by increasing the cycle of pump stroke (cycle of displacement of the plunger). That is, if the cycle of the pump stroke is reduced, the degree of decrease in the flow rate per unit time increases, and if the cycle of the pump stroke is increased, the degree of decrease in the flow rate decreases. By increasing the value, the degree of decrease in the withstand pressure flow rate per unit time is reduced.

[Problems to be Solved by the Invention] However, when the pump stroke is increased, the pressure resistance constant flow rate per unit time is improved, but the pressure ripple increases as the flow rate decreases. For example, 1
When the liquid is sent at a flow rate of about 1 ml per minute or more, the pressure resistance constant flow rate property is not lowered and the ripple is small. However, when the liquid is sent at a flow rate of 0.1 ml or less per minute, the ripple cycle of the pump becomes as long as about 1 minute and the ripple cannot be smoothed even if a damper is used. Further, in a system in which two or more kinds of liquids are mixed, such as gradient elution, when the stroke is increased as described above, when the mixing ratio of the two liquids is continuously changed, Since the two liquids are not mixed at a predetermined mixing ratio, a ripple occurs on the baseline of the spectrum at the time of detection.

The present invention solves such a problem, and provides a novel method for controlling a liquid delivery pump capable of delivering a constant flow rate in a wide range of flow rates regardless of the type of liquid and the conditions under which the liquid is placed. Is.

[Means for Solving Problems] A method for controlling a liquid feed pump according to the present invention is such that a liquid is sucked from the outside by a first pump, and an appropriate compression preliminary pressure is applied to the liquid immediately before the liquid is discharged. , The second pump sucks the liquid from the first pump and discharges the liquid to the outside. At that time, when the second pump switches from the suction process to the discharge process, The pressure is made to be the same as the pressure outside the pump chamber, and the plungers are linearly reciprocated in the first pump chamber and the second pump chamber by the movement of the cams operated by the independent cam drive mechanisms to continuously Liquid is delivered to the cam, and the cam rotation angle is set based on the product of the linear movement amount of the plunger per unit time according to the flow rate and the predetermined one-way movement time of the plunger. , The setting The cam is reciprocally rotated within the range of the rotation angle, the slope of the time-varying waveform of the pressure obtained by detecting the discharge pressure of the second pump is obtained, and the slope becomes zero based on the slope. The first
It is characterized in that the moving distance of the plunger of the pump is changed.

[Function] Type of liquid to be sent and conditions under which the liquid is placed (pressure,
The pre-compression pressure varies depending on the temperature and the degree of wear of the seal member. Therefore, a liquid is sucked from the outside by the first pump, and a compression preliminary pressure having a magnitude based on the type of liquid to be sent and the condition in which the liquid is placed is applied immediately before the liquid is discharged,
The second pump sucks the liquid from the first pump and discharges the liquid to the outside. At this time, the pressure in the second pump chamber when the second pump switches from the suction process to the discharge process. Is made to be the same as the pressure outside the pump chamber, and the plunger is linearly reciprocated in the first pump chamber and the second pump chamber by the movement of the cam operated by the cam drive mechanism, and the liquid is sucked. In the method in which the liquid is discharged and the liquid is continuously sent, the linear movement amount of the plunger per unit time according to the flow rate and the predetermined one-way movement time of the plunger Set the rotation angle of the cam based on the product of. For example, if you choose a small flow rate,
The linear movement amount of the plunger per unit time is set small, and the rotation angle of the cam is set to be small based on the product of the linear movement amount per unit time and the predetermined one-way movement time of the plunger. When a large flow rate is selected, the linear movement amount of the plunger per unit time is increased, and the cam is calculated from the product of the linear movement amount per unit time and the predetermined one-way movement time of the plunger. The rotation angle is set to a large one. If the flow rate is to be increased with the rotation angle set to a small value, the speed of the motor that rotates the cam must be extremely increased, which is not possible. In this way, if the cam is reciprocally rotated within the range of the rotation angle set according to the flow rate, there is no noise even under high pressure in a wide range of flow rate, and liquid can be transferred with good quantitativeness.

[Embodiment] FIG. 1 is a schematic view of a constant flow rate pump device showing an embodiment of the present invention.

In the figure, the same numbers and symbols as those used in FIG. 1 represent the same components.

In FIG. 1, the discharge passage OA of the first pump chamber 6A and the suction passage IB of the second pump chamber 6B are connected. The first heart cam 1A and the second heart cam 1B are provided with separate shafts 2A and 2B, respectively. The respective cams are connected to the shafts of the motors 3A and 3B. The motor operates based on a command from the control device 10. One of the commands is a command for setting the rotation angle of the cam for obtaining a predetermined flow rate.

That is, the flow rate, which is the liquid delivery amount per unit time, corresponds to the linear movement amount of the plunger per unit time. Therefore, the control device 10 sets the rotation angle of the cam based on the product of the linear movement amount of the plunger per unit time according to the flow rate to be selected and the predetermined one-way movement time of the plunger. For example, when a small flow rate is selected, since the linear movement amount of the plunger per unit time is small, the cam is calculated from the product of the linear movement amount per unit time and the predetermined one-way movement time of the plunger. The rotation angle is set to a small one. When a large flow rate is selected, since the linear movement amount of the plunger per unit time is large, the cam is calculated from the product of the linear movement amount per unit time and the predetermined one-way movement time of the plunger. The rotation angle is set to a large one. The control device sets the rotation angle of the cam according to the flow rate to be selected in this way, and sends a command to the motor so that the cam is reciprocally rotated within the set rotation angle range. Specifically, when a pulse motor is used as the motor, a signal specifying the number of pulses per unit time, the time interval between the pulses, and the rotation direction is sent to the pulse motor.

A pressure gauge 11 is provided in the discharge passage OB of the second pump chamber 6B, and the control device 10 obtains the inclination of the pressure waveform based on the pressure information from the pressure gauge, and based on the inclination, Send commands to each motor. In the pump device, the second plunger 5B has a function of discharging the liquid to the outside, and the first plunger 5A has a function of sending the appropriately pressurized liquid to the second plunger 5B. And each of these plungers operates independently.

The operation of the constant flow rate liquid feed pump configured as described above will be described below.

In advance, the control device 10 sends a command signal related to the rotation angle of the cam for obtaining the flow rate to be selected to the motors 3A and 3B. For example, when a small flow rate is selected, since the linear movement amount of the plunger per unit time is small, the cam is calculated from the product of the linear movement amount per unit time and the predetermined one-way movement time of the plunger. If the rotation angle is set to a small value and a large flow rate is selected, the linear movement amount of the plunger per unit time is large, so the linear movement amount per unit time and the predetermined one-way movement of the plunger are set. The rotation angle of the cam is set to a large value from the product of time. The control device sets the rotation angle of the cam in accordance with the flow rate to be selected, and sends a command signal to the motor so that the cam can be reciprocally rotated within the set rotation angle range. In the reciprocating rotation within the set angle range, for example, the suction step is performed when rotating to the right, and the discharging step is performed when rotating to the left.

FIG. 2 is a diagram showing the operation of the plunger, in which the horizontal axis represents time, the vertical axis represents the discharge amount per unit time in the upper direction, and the suction amount per unit time in the lower direction, that is, the speed of the plunger.
In the figure, the broken line shows the operation of the first plunger 5A and the solid line shows the operation of the second plunger 5B.

As shown in FIG. 2, when the first pump performs the suction process, the supply pressure of the liquid from the liquid tank 7 is generally low, so that cavitation easily occurs in the pump chamber or the valve. It is particularly likely to occur when rapidly aspirated, and this cavitation causes air bubbles, which makes the operation irregular. Therefore, the suction process of the first pump is performed as slowly as possible. or,
The first pump prepressurizes the sucked liquid for a very short period of time between the suction stroke and the discharge stroke. The magnitude of the pre-pressurization differs depending on the type of liquid to be fed and the conditions under which the liquid is placed (pressure, temperature, degree of wear of the seal member, etc.), so the first pump should feed. Pre-pressurization of a size based on the type of liquid and the conditions under which the liquid is placed is performed. Due to the pre-pressurization, the liquid is not sent to the second pump, but is compressed (the liquid has a pressure of about 100 kg / cm ²
~ Shrinks about 2%, and at a pressure of 500 kg / cm ² shrinks by 5/10%).
The degree of this pre-pressurization is such that when the second pump chamber that has sucked the liquid discharged from the first pump chamber switches to the step of discharging the liquid to the outside, the pressure of the liquid inside the second pump chamber is set to the outside. It is about the same as the pressure. Next, the first pump discharges the compressed liquid S ₁ into the second pump chamber in a very short time.

On the other hand, the second pump is a pump having a role of sucking the liquid compressed to the pressure required by the first pump and discharging the liquid to the outside at a predetermined flow rate accurately. The liquid is discharged to the outside at a predetermined constant flow rate in synchronization with the process of discharging for pressurization. Therefore, the discharge stroke of the second pump is performed slowly.
Also, in synchronism with the discharge stroke of the first pump, the liquid of S ₂ compressed from the first pump in a very short time is sucked,
In the suction process, unlike the suction process of the first pump, the liquid from the first pump is forcibly sent, and the pressure on the suction side of the second pump is close to that pressure. However, cavitation does not occur and therefore suction can be performed very quickly.

Now, the liquid discharge amount S ₁ by the first pump (first plunger 5A) is the liquid suction amount S ₂ by the second pump (second plunger 5B) and the time required for the discharge process of the first plunger. It is equal to the sum of the discharge amounts S ₃ of the second plungers 5B at the same time. That is, the discharge amount of the liquid by the first pump S ₁ and equal to the difference of the suction volume S ₂ is S ₃ according to the second pump, the liquid of the S ₃ is the discharge stroke of the first pump (suction stroke of the second pump) And is ejected to the outside in a very short time. As a result, a fixed amount of liquid is continuously sent per unit time from the second pump chamber 6B.

In this way, the first plunger 5A repeats the process of performing the discharge from the suction to the pre-pressurization → the discharge process → the process of performing the discharge from the suction to the pre-pressurization → the discharge process, and the second plunger 5B does this. The ejection process, the suction process, the ejection process, and the suction process are repeated in synchronization. Then, in such a process, the operation characteristics of the two pumps are that the first pump sucks slowly and discharges quickly, and the second pump sucks quickly and discharges slowly.

When the flow rate is set to a different value, the rotation angle of the cam changes according to the flow rate. However, if the rotation angle of the cam is made smaller, the discharge amount and the suction amount are changed accordingly in FIG. Lower and the cam rotation angle increases,
The discharge amount and the suction amount are high. However, the time required for this discharge and inhalation does not change.

Now, the preliminary compression and pressurization by the first plunger 5A of the first pump is performed by the pressure gauge 11 provided in the discharge passage of the second pump chamber 6B.
By detecting the pressure of the liquid discharged from the second pump chamber, the control device 10 obtains the slope of the pressure waveform (that is, the pressure velocity on the discharge side of the second pump) based on the pressure information from the pressure gauge. , Is controlled by sending a command to each of the motors based on the inclination. That is, according to the experiment, in the steady state, the pressure waveform of the liquid discharged from the second pump chamber is such that the liquid sucked by the second plunger 5B is not pressurized to the external pressure (predetermined discharge pressure) ( That is, the second
The actual liquid delivery amount Ur of the pump chamber is the designed liquid delivery amount Uo of the second pump.
When the liquid is smaller than the above, the liquid is inclined to the right as shown in FIG. 3 (a), and the liquid is pressurized higher than the external pressure (that is, Ur> Uo), as shown in FIG. 3 (c). Similarly, it will be tilted to the left. In this case, the degree of these inclinations is equal to the difference in external pressure.

When the pressure of the liquid is equal to the external pressure (that is, Ur = Uo)
As shown in FIG. 3 (b), the inclination is zero, that is, it is parallel to the time axis.

Then, the control device 10 controls the first plunger 5A if the pressure waveform has a rightward inclination as shown in FIG. 3 (a).
The motor 3A for activating the above is instructed to appropriately increase the moving distance of the first plunger 5A and supply a signal for increasing the preliminary compression / pressurization so that the inclination becomes zero. or,
As shown in FIG. 3 (c), in the case of a leftward tilt, a signal for reducing the movement distance of the first plunger and appropriately reducing the preliminary compression / pressurization is supplied so that the tilt becomes zero. Order. In addition, a constant pressure release valve that releases a surplus amount from the first pump to the second pump in advance to a slightly larger amount than the required liquid amount of the second pump is provided in the discharge passage of the first pump chamber 6A.
It may be provided between the OA and the suction passage IB of the second pump chamber 6B, and the operating pressure of the release valve may be controlled by the control device 10 to equalize the pressure inside the second pump chamber and the pressure outside the chamber. .

[Advantages of the Invention] According to the present invention, a liquid is sucked from the outside by a first pump, an appropriate compression preliminary pressure is applied to the liquid immediately before the liquid is discharged, and a second pump is used to discharge the liquid from the first pump. Inhaling the liquid of
To discharge to the outside, in which case the pressure inside the second pump chamber becomes the same as the pressure outside the pump chamber when the second pump switches from the suction process to the discharge process, each independent cam By moving the cam operated by the drive mechanism, the plunger is linearly reciprocated in the first pump chamber and the second pump chamber to perform the suction operation and the liquid discharge operation of the liquid, and to continuously feed the liquid. As the liquid is supplied and the cam is reciprocally rotated within the range of the rotation angle set according to the flow rate, the type of liquid or the type of liquid can be used in a wide range of flow rates (eg, 0.1 μm to 2 ml per minute). Regardless of the condition in which the liquid is placed, a small amount of liquid can be sent with good quantitativeness.

Further, even in a system in which two or more kinds of liquids are mixed, such as gradient elution, the two liquids can be mixed at a predetermined mixing ratio, and the mixing ripple is eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a pump device showing an embodiment of a method for controlling a liquid delivery pump according to the present invention, FIGS. 2 and 3 are operation diagrams of the pump device, and FIG. FIG. 5 and FIG. 5 show an example of a conventional double plunger type pump mechanism, FIG. 6 is a plan view of a heart cam used in the pump mechanism, and FIG. 7 is the aforementioned FIG. 4 and FIG. FIG. 6 is a diagram used to supplement the description of the operation of the pump mechanism of FIG. 1A, 1B: 1st, 2nd heart cam, 2A, 2B: shaft, 3A, 3B: motor, 4A, 4B: 1st, 2nd roller, 5A, 5B: 1st, 2nd plunger, 6A, 6B: 6th 1, second pump chamber, 7: liquid tank, 8a, 8b, 8c, 8d: ball, 9A, 9B: compression spring, 10: control device, 11: pressure gauge, IA, I
B: suction path, OA, OB: discharge path

Claims (1)

[Claims] 1. A liquid is sucked from the outside by a first pump,
Immediately before discharging the liquid, an appropriate compression preliminary pressure is applied to the liquid,
The second pump sucks the liquid from the first pump and discharges the liquid to the outside. At this time, the pressure in the second pump chamber when the second pump switches from the suction process to the discharge process. Are made to be the same as the pressure outside the pump chamber, and the plungers are linearly reciprocated in the first pump chamber and the second pump chamber by the movement of the cams operated by independent cam drive mechanisms, respectively, and continuously. The liquid is sent, and the rotation angle of the cam is set based on the product of the linear movement amount per unit time of the plunger according to the flow rate and the predetermined one-way movement time of the plunger, The cam is reciprocally rotated within the set rotation angle range, and the slope of the time-varying waveform of the pressure obtained by detecting the discharge pressure of the second pump is obtained, and the slope becomes zero based on the slope. Yo Control method of the liquid supply pump, characterized in that so as to vary the travel distance of the plunger of the first pump.