JP2001254684A - Liquid feeder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extremely precisely and stably feed liquid, in a liquid feeder for liquid chromatography. SOLUTION: In a device alternately and continuously feeding liquid to a receiver side by two plunger pumps, a load sensor is connectedly arranged in the plunger of each pump. The frictional force between the plunger and a plunger seal is transmitted to a control part by a signal transmission line. The drive part of the plunger is controlled via the control part so as to control the operation of the plunger. Pre-pressurization and discharge between the two pumps are controlled by the control part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a liquid feeding device.

[0002]

2. Description of the Related Art In liquid chromatography, a pump for continuously feeding a solvent has been proposed. For example,
U.S. Pat. No. 4,347,131 shows the use of a single cylinder pump for each solvent of different composition. This is an intermittent mode in which the operation of the cylinder is started and stopped, so that the hydraulic pressure capacity fluctuates during operation, and the liquid flow rate cannot be maintained constant unless the system pressure corresponds to the change in the viscosity of the solvent. .

Also, US Pat. No. 4,919,595 and US Pat. No. 4,985,0059 propose an apparatus for compensating for the shortage of liquid flow and preventing the flow from being interrupted. It has not been possible to prevent turbulence in airflow and system pressure.

To solve these problems, Japanese Patent Application Laid-Open No.
72130 has been proposed. This is a continuous pumping device that operates two pump units independently, and a pressure sensor is provided in each pump unit. The pressure sensor can compress the contents of the cylinder refilled off-line without disturbing the operation in the on-line state, and when the compression is completed, it is possible to determine when to start feeding the fluid to the system It is to be.

[0005]

The double plunger pump is widely used as a stable continuous liquid feeding device. Both plungers project and suck alternately so that liquid can be continuously fed, and the combined flow rate becomes constant. However, such an idea does not hold under high pressure conditions, and as a result, stable continuous liquid sending cannot be obtained. Usually, the pump on the protruding side is started at atmospheric pressure, and the compression ratio of the solvent, deformation of the pump chamber, deformation of the elastic polymer plunger seal (compression at high pressure, the seal shrinks), etc. This is because a time is required for the fluid pressure in the initial stage (compression process) of the protruding process to rise to the system pressure. In the compression step, continuous pumping is substantially not performed because the pump does not pump into the system. In particular, it is impossible to overcome such disadvantages when using one motor with a double plunger pump.

A double plunger pump having an independent drive has been developed to overcome the above-mentioned disadvantages. On the other hand, the solvent is compressed before the plunger protrudes, an appropriate preliminary pressurization is performed, and the other plunger protrudes with an appropriate pressure at the moment when the plunger finishes protruding. Information such as the appropriate pressure is obtained from a pressure sensor in fluid communication based on a "learning function" or in the pump chamber. In the former case, information such as "appropriate pressure" cannot be obtained unless the liquid is sent for a while. In other words, pre-pressurization is over before projecting,
Since the system pressure is disturbed, correction is made so as not to exceed the next pre-pressurization and gradually converges to “appropriate pressure”. However, even if the “appropriate pressure” is finally found, it is impossible to immediately respond and follow up if there is some fluctuation in the external conditions. In particular, in the case of a very small flow rate, one stroke of the plunger takes a considerable amount of time, and such a post-learning function has a practical problem.

The pressure in the pump chamber is monitored in real time by a pressure sensor which is in fluid communication with the pump chamber, and the plunger on the standby side discharges the pressure (or system pressure) of the plunger before discharging before discharging.
The pressure in the pump chamber is pre-pressurized on the basis of. The plunger for which the pre-pressurization has been completed theoretically has no discharge delay time when discharging in response to the discharge command. However, there is a problem that the dead volume of the pump chamber is increased due to the built-in pressure sensor which is in fluid communication with the pump chamber. Further, when the solvent is changed, the replacement time is long, and even when air is generated, the air does not escape, and even if the pre-pressurizing function is provided, it may not be possible to fully pressurize to the target pressure. A pressure sensor in fluid communication with the pump chamber can detect the pressure in the pump chamber, but can constantly monitor the usage state of the plunger seal and the frictional force between the plunger seal and the plunger. Can not.

[0008] Under the pressure of the liquid feeding condition, the pressure in the pump head fluctuates constantly. In the compression step, the plunger begins to advance immediately after drawing the liquid at atmospheric pressure, compresses the liquid and the pressure in the pump head increases as the plunger advances. At that time, there are two of the forces that resist plunger advancement, one is the frictional force between the plunger and the plunger seal, and the other is the resistance to the internal pressure of the pump head. In the compression process, a resilient polymeric plunger seal is compressed as pressure increases, and above a certain threshold, some seals escape into the backside gap. In this case, despite the fact that the capacity of the pump head is reduced due to the advance of the plunger, the internal capacity of the pump head does not change temporarily or almost stops changing due to the insertion or clearance of the plunger seal. Or a gradual rise (hereinafter referred to as a pressure rise delay stage). If the pressure continues to increase, the frictional force between the plunger and the plunger seal becomes substantially constant, and the frictional force between the plunger and the plunger seal at that time and the resistance of the internal pressure of the pump head are reduced. It becomes a pressure function in the chamber. But,
The pressure at that time is not used in ordinary liquid chromatography.

In the case of a multi-pump system, there is a method of pre-pressurizing in order to eliminate the fluctuation of the pressure when the discharge is alternated with the aim of the pressure on the side of the discharging plunger. A pressure sensor in fluid communication with each pump chamber monitors the pressure in the pump chamber and accurately controls the pre-pressurization process. But,
The pressure sensor has individual differences, and even if it is configured between the sensors, the pressure sensor is shifted again due to an influence of a liquid temperature change or the like. In particular,
If the pre-pressurization has been completed in the “pressure rise delay phase” and the pressure in the pump is slightly lower than the system pressure, the pump plunger moves forward during the discharge process even if the plunger advances. Since discharge cannot be obtained, a significant decrease in system pressure cannot be avoided, and stable liquid feeding cannot be performed.

[0010] There are quite a lot of needs to make the liquid contact part non-metallic, but it is very difficult to make the pressure receiving part of the pressure sensor that is in fluid communication with the pump chamber nonmetallic. The pressure-receiving part of the pressure sensor can be coated with fluororesin or the like, but the coated fluororesin film or the like is weak in mechanical strength and will be peeled off during installation.
Further, if the receiving pressure portion is covered with a packing made of polymer, the response of the pressure sensor becomes considerably slow, so that accurate control of pre-pressurization becomes impossible.

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention uses a load sensor to prevent a plunger seal from escaping when the end stage of pre-pressurization exactly coincides with the "pressure rise delay stage". Since the frictional force between the piston and the plunger seal is increased, a highly sensitive response signal is obtained, and the pre-pressing process can be controlled more precisely. Also, the phenomenon that some plunger seals escape into the gap on the back surface occurs at a high pressure stage, but when the plunger enters the suction process, the internal pressure of the pump head becomes atmospheric pressure and The escaped seal also partially returns to its original position. At that time, in consideration of the case where the zero point of the load sensor shifts due to the frictional force between the plunger and the plunger seal even though the internal pressure of the pump head is 0,
The zero point of the load sensor can be automatically adjusted while referring to the value of the pressure sensor attached to the same pump head.

That is, according to the present invention, even when the pressure rise in the pump chamber is delayed, it is easy to capture the change in the signal indicating the pressure change.
The plunger can be operated via the motor, avoiding a decrease in system pressure and ensuring stable liquid supply. First, the plunger driven by the drive unit can freely enter and exit the pump chamber. In addition, a load sensor is provided at the rear of the plunger, a signal transmission line is provided on the load sensor, and two or more pumps are connected to a drive unit such as a motor via a control unit. The second feature is that the plunger driven by the drive unit can freely enter and exit the chamber of the pump, a load sensor is provided at the rear of the plunger, and a signal transmission line is provided to the load sensor. On the other hand, a pressure sensor that is in fluid communication with the chamber is provided, and the operation of each plunger is controlled by signals from both sensors. And butterflies.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to connect and use a desired plunger pump. FIG. 1 shows a structure in which two plunger pumps are connected in series and connected in series. Here is the plunger pump
One cylinder and associated piston,
It means a piston seal and a piston actuator.

Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings. Reference numeral 1 denotes a pump head, and a plunger 8 is inserted freely into and out of a chamber 7 formed in the center thereof. A through hole 71 is formed in communication with the chamber 7,
An inlet check valve 4 and an outlet valve 5 are provided in the through hole 71, respectively. One end communicates with the solvent tank 2 via the inlet conduit 3, and the other communicates with another pump, supply destination, etc. via the outlet conduit 6. They are communicating. The pump head 1 is a cylinder, and the plunger 8 is a piston.

An empty space 34 is provided at the rear end of the pump head 1 so as to communicate with the chamber 7, and the wall surface thereof is formed in a tapered shape. Reference numeral 30 denotes a seal mounting portion, the side surface of which is formed in a tapered shape, which can be mounted on the empty space 34. At this time, it is recommended that the tip diameter be increased or the degree of taper be formed so that the side surface hits the cavity 34. Reference numeral 9 denotes a plunger seal having a plunger seal spring or an O-ring 33 made of polymer. The plunger seal 9 is in contact with a seal mounting portion 30, and a rear portion thereof is in contact with a backup ring 10 inserted through the plunger 8. The backup ring 10 is a plunger seal 9
It is recommended to use a polymer that is harder than the material and softer than stainless steel. The backup ring 10
As a result, a force for holding down the plunger seal 9 is given, the pressure resistance of the plunger 8 is increased, and the plunger 8 operates as a protection guide. The pump head 1 is fixed to the pump head mounting block 16 by screws 31 via the backup ring 10 and the like, and the seal friction force is adjustable.

By using a backup ring 10 made of a polymer having an appropriate hardness, a gap 32 is provided so that the plunger 8 does not come into contact with the pump head mounting block 16.
Is slightly enlarged, the gap 32 is covered by the backup ring 10, so that the plunger seal 9
Can be prevented from deforming at high pressure and escaping to the low pressure side, thereby deteriorating the pressure resistance. Further, by using the backup ring 10, the torque of the screw 31 can be easily adjusted when the pump head 1 is mounted on the pump head mounting block 16 in order to obtain the optimum frictional force between the plunger 8 and the plunger seal 9. Become.

Reference numeral 11 denotes a spline shaft, the tip of which is a cylindrical space 1 formed in a pump head mounting block 16.
61 can be inserted freely, and the center part is the spline outer cylinder fixing part 1
8 is supported by a splined outer cylinder 17. More specifically, the ball 171 supported in the spline outer cylinder 17 is pressed and rolled into a rolling groove precisely ground on the spline shaft 11. A plunger base 81 is housed in an empty space 111 provided at the tip of the spline shaft 11, and a spring 13 supported by a spring retainer 12 provided at the tip is provided.
It is suppressed by the rear. Reference numeral 14 denotes a load sensor or a load sensor (hereinafter, represented by a load sensor).
The spring 13 is provided in contact with the rear portion of the plunger base 81 so as to be resiliently provided. The load sensor 14 is provided with a signal transmission line 15 and communicates with a control unit 26. Since the value is constant even during the plunger operation caused by the spring 13, it can be ignored by the electrical zero adjustment.
The control unit 26 includes a motor 24 provided at the rear end of the pump body 27.
Is in communication with A nut 21 of a ball screw 20 is connected to the other end of the spline shaft 11 via a connecting unit 19, and the ball screw 20 threaded through the nut 21 is
It is larger than the diameter of the ball screw 20 and freely enters and exits a cylindrical space 25 formed longer than the longest stroke of the plunger 8.

As the plunger 8 reciprocates, it is recommended to employ a ball spline to prevent the plunger 8 from oscillating against the plunger seal 9 and rotating the plunger 8. The ball spline is a linear motion system in which a ball incorporated in a spline outer cylinder 17 can transfer torque while performing a smooth linear motion in a rolling groove of a precisely ground spline shaft 11.
Further, the plunger 8 is hardly subjected to external vibrations, shocks, and the like by applying a pressurized force by the spline outer cylinder 17, and a highly accurate positioning structure can be simplified. The rotational motion of the motor 24 provided on the pump body 27 is transmitted to the ball screw 20 via the coupling 23, and the ball screw 2
The zero nut 21 drives the spline shaft 11 to realize the reciprocating linear movement of the plunger 8.

When the spline shaft 11 moves forward and backward, the plunger 8 moves into and out of the pump chamber 7, and at the time of the movement, the liquid is pushed out and sent to the outlet conduit 6. At this time, the pressure received from the liquid by the advance of the plunger 8 is applied via the plunger base 81 to the load sensor 14.
, And the signal is sent to the control unit 26 via the signal transmission line 25. The signal from the control unit 26 is
To control the rotation of the motor 24.

In FIG. 1, 27 pumps 27A, 27
B is connected in series. To explain this in detail, pump 2
The pump chambers 7, 7 are connected to the pump chamber 7A by a connecting pipe 60. The solvent tank 2 is connected to the pump 27A via the inlet conduit 3 and the pump 27B
Are connected to outlet conduits 6, respectively. In the two pumps 27A and 27B, the stroke length or diameter of each plunger 8A, 8B is determined by the respective plungers 8A, 8A, 8B of both pumps 27A and 27B.
8B, the stroke length of the plunger 8A of the pump 27A is
And the average speed of the reciprocating movement of the plunger 8A is twice that of the plunger 8B. When the diameter of the plunger 8A is twice as large as the diameter of the plunger 8B, the average speed of the reciprocating motion of the plunger 8A and the stroke length of the plunger 8A are the same as those of the plunger 8B.

The plungers 8A and 8B of the respective pumps 27A and 27B are alternately operated by the control unit 26 by the motor 24. Explaining the operation of one plunger 8A, the rotation of the motor 24 causes the ball screw 20 to rotate via the coupling 23. The spline shaft 11 is moved forward and backward by the ball screw nut 21 screwed to the ball screw 20 and the connection unit 19 for fixing the nut. When the spline shaft 11 moves forward and backward, the ball is built in the spline outer cylinder 17 to move forward and backward with high accuracy. When the spline shaft 11 moves forward, the plunger 8A moves forward while pressing the plunger fixing spring 13 via the load sensor 14 and the plunger base 81.

At this time, the pump 27A as a preparation for sending the liquid sucks the solvent from the solvent tank 2, and the sucked solvent is connected to the pump head of the pump 27B via the connecting pipe 60 from the outlet check valve 5 by the plunger 8A. The liquid passes through the chamber 7 via the inlet check valve 4 and is sent at the set flow rate at the same time as the liquid sending start command. Half of the solvent sent is pump 27, which just starts
It is sucked by the suction operation of B, that is, the backward movement of the plunger 8B. From the point in time when the plunger 8A of the pump 27A finishes discharging and enters suction, the plunger 8 of the pump 27B
B begins to protrude. Therefore, during the liquid feeding, the pressure in the pump head of the plunger 8A of the pump 27A, that is, the pressure in the chamber 7 changes in the steps such as suction and discharge.
The pressure in the pump head of 7B plunger 8B, i.e., chamber 7, is the same as the system pressure via outlet conduit 6, and there is no pressure fluctuation in each step.

The embodiment shown in FIG. 2 shows a parallel double pump arrangement. In this embodiment, the solvent tank 2 communicates with the pump heads of the respective pumps 27A and 27B via the respective inlet conduits 3 and 3 and also communicates with the outlet conduit 6 respectively. In this case, the two pumps 27A and 27B are alternately turned on the plunger 8 respectively.
A and 8B are operated to alternately protrude and suck. Of course,
The plunger diameter and stroke length are exactly the same. Here, the operation steps of the two pumps remain unchanged.

That is, each plunger pump sucks the solvent in preparation for liquid sending. At the same time as the liquid sending start command, one plunger pump starts liquid feeding at the set flow rate. At the same time, the next plunger pump to be fed next starts a pre-pressure operation to reach the pressure of the plunger pump during feeding. The suction operation starts when the plunger pump during liquid feeding completes the full stroke liquid feeding, and at the same time, the plunger pump during pre-pressure operation starts liquid feeding. Next, the plunger pump to be fed next starts the preload operation. By repeating the above, continuous liquid feeding is performed.

Referring to the embodiment shown in FIG. 3, a pressure sensor 28 is provided in communication with the chamber 7 and connected to the control unit 26 by a signal transmission line 29. Other configurations are the same as the embodiment of FIG. Therefore, the pressure inside the pump head can be monitored by the pressure sensor 28. This pressure is transmitted to the control unit 26,
Control the motor 24 as desired. On the other hand, in the load sensor 14, when the zero point shifts to an increase in the frictional force between the plunger and the plunger seal, the zero point of the load sensor is automatically adjusted with reference to the monitoring value of the pressure sensor 28. You. By the mutual correction of the two, the pre-pressurization of the pump is performed more accurately,
Precise liquid delivery is achieved.

[0026]

As described above, according to the first aspect of the present invention, the plunger driven by the driving unit can freely enter and exit the chamber of the pump, and the load sensor is provided at the rear part of the plunger. By providing a signal transmission line to the sensor, comprising two or more pumps connected to a drive unit such as a motor via a control unit, since each signal transmission line is connected to the control unit, by using a load sensor, The end stage of pre-pressurization is just "pressure rise delay stage"
In the case of overlap, the escape of the plunger seal increases the frictional force between the plunger and the plunger seal, resulting in a highly sensitive response signal and more precise control of the pre-pressurization process. Can be done. Therefore, the pressure rise delay stage of the conventional apparatus is overcome, the final pressurization step is performed accurately, the discharge step is performed accurately, and the liquid is supplied in accordance with the specified target value.

According to the second aspect of the present invention, the plunger driven by the driving unit can freely enter and exit the chamber of the pump, and a load sensor is provided at the rear of the plunger.
Since a signal transmission line is provided for the load sensor, a pressure sensor is provided in fluid communication with the chamber, and the operation of each plunger is controlled by signals from both sensors.
Improving the disadvantage that the zero point of the load sensor when entering the load sensor suction process shifts to an increase in the frictional force between the plunger and the plunger seal, the value of the pressure sensor can be referred to, through the signal line The zero point of the load sensor can be automatically adjusted, and the pressure in the pump chamber can be monitored directly, so that the pre-pressurization process can be performed more accurately. Therefore, accurate continuous liquid feeding can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of one embodiment of the present invention.

FIG. 2 is a schematic explanatory view of another embodiment of the present invention.

FIG. 3 is a schematic explanatory view of another embodiment of the present invention.

FIG. 4 is a comparison diagram of two examples of sensors.

FIG. 5 is an enlarged vertical cross-sectional explanatory view of an essential part of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump head part 7 Pump chamber 8 Plunger 9 Plunger seal 10 Backup ring 11 Spline shaft 17 Spline outer cylinder 30 Plunger seal mounting part 31 Adjustment screw 33 Spring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H045 AA03 AA09 AA14 AA22 AA37 BA19 CA03 DA42 EA13 EA42 3H069 AA01 AA09 BB03 CC03 DD14 EE32

Claims (2)

[Claims] 1. A plunger driven by a driving unit can be freely moved into and out of a chamber of a pump, a load sensor is provided at a rear portion of the plunger, a signal transmission line is provided at the load sensor, and a motor or the like is provided via a control unit. A liquid transmission device comprising two or more pumps connected to the drive unit, and each signal transmission line connected to the control unit. 2. A plunger driven by a driving unit is freely movable into and out of a chamber of a pump, a load sensor is provided at a rear portion of the plunger, a signal transmission line is provided to the load sensor, and fluid communication is performed with the chamber. A liquid feeding device comprising a pressure sensor and controlling the operation of each plunger according to signals from both sensors.