JP2008291848A - Pump for liquid chromatography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump for a liquid chromatography having stable liquid-feeding at an extremely low flow rate and excellent bubble discharging characteristics at the time of starting. <P>SOLUTION: In the pump 10 for a liquid chromatography for sucking a low-pressure eluate 2 in an eluate storage container 1 and supplying the pressurized high-pressure eluate 2 to a column 51, plungers 16 and 17 for reciprocating in cylinders 13 and 14 are arranged, stepped sections are respectively formed along the sliding direction of the plunger on the outer peripheral sides of the plungers 16 and 17 in the cylinders 13 and 14, operation chambers 24 and 25 for pressurizing the eluate at the stepped sections are provided, and a flow rate of a pump system is determined by the capacity of the operation chambers 24 and 25. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid chromatograph, and more particularly, to a liquid chromatograph pump suitable for feeding a liquid at a low flow rate.

  Conventional liquid chromatograph pumps generally have a configuration in which eluent is sucked and discharged by a plunger that reciprocates in a cylinder. For this reason, when a very small amount of the eluent is fed with high liquid feeding accuracy, it is necessary to make improvements such as reducing the plunger diameter or reducing the plunger stroke. In addition, the smaller the amount of liquid fed, the more difficult it is to discharge bubbles that have accumulated in the pump or in the liquid flow path.

  As a pump structure for feeding liquid without being affected by bubbles in the eluent, it has a first pump head and a second pump head that are commonly driven by different diameter coaxial plungers having a large diameter portion and a small diameter portion. Two pump heads having different volumes, and the two pump heads driven by the large-diameter portions of the different-diameter coaxial plungers of the first pump head and the second pump head are used as the first pump. Two pump heads driven by the small diameter portion of the plunger are configured as a second pump, and the first pump and the second pump are serially coupled. A configuration is known in which a heater and a gas / liquid separator are provided at the discharge port of the first pump, and the eluent from which bubbles have been removed by the gas / liquid separator is sucked by the second pump and sent (for example, , See Patent Document 1).

JP 2000-39427 A (2nd page, FIG. 3)

  The above prior art is intended to perform precise liquid feeding without being affected at all by the air valve in the eluent, and no sufficient consideration has been given to reducing the amount of liquid fed. In this prior art, the flow velocity of the first pump driven by the large diameter portion of the different diameter coaxial plunger is made larger than the flow velocity of the second pump driven by the small diameter portion of the different diameter coaxial plunger (preferably twice or more). Therefore, the minimum discharge amount of the pump system is determined by the discharge volume of the second pump. For this reason, in order to reduce the minimum discharge amount of the pump system, it is necessary to reduce the plunger outer diameter that determines the discharge volume of the second pump. However, it is not easy from the viewpoint of processing accuracy and strength to reduce the minimum discharge amount by reducing the plunger outer diameter.

  In the prior art, if the large diameter portion of the plunger is made constant and the small diameter portion of the plunger is narrowed to reduce the discharge volume of the second pump, the discharge volume of the first pump is relatively increased. On the other hand, even if the plunger small-diameter portion is made thick and the discharge volume of the first pump is made small, the discharge volume of the second pump is increased. There is a problem that it is difficult to reduce the amount.

  In addition, if the pump discharge volume is reduced to reduce the amount of liquid to be fed, it takes a long time to fill the solvent liquid into the flow path for liquid feeding and to discharge the bubbles at the start of the test. .

  A first object of the present invention is to provide a liquid chromatograph pump suitable for reducing the flow rate of liquid feeding. A second object of the present invention is to provide a liquid chromatograph pump capable of completing the filling of the solvent liquid and the discharge of bubbles at the start of the test in a short time.

  In order to achieve the first object, the liquid chromatograph pump of the present invention is a liquid chromatograph pump comprising a cylinder and a plunger that reciprocates in the cylinder. A step portion is formed along the driving direction of the plunger, a working chamber is constituted by the step portion and the inner wall surface of the cylinder, and the liquid chromatograph is constituted by a cross-sectional area of the working chamber and a driving speed of the plunger. The flow rate of the pump is determined. At this time, the first pump having a first plunger that reciprocates within the first cylinder and the first cylinder, and the second plunger that reciprocates within the second cylinder and the second cylinder. A suction pump on the upstream side of the first pump and a discharge valve on the downstream side of the first pump, and at least on the outer peripheral surface of the second plunger of the second pump. The step portion is formed along the driving direction of the plunger, and the working chamber is constituted by the step portion and the inner wall surface of the second cylinder, and the second pump is placed in the liquid chromatograph pump. It is good to arrange | position at the most downstream side of the some pump comprised. Alternatively, a first pump having a first cylinder and a first plunger reciprocating in the first cylinder, and a second pump having a second cylinder reciprocating in the second cylinder and the second cylinder. Two pumps, a suction valve on the upstream side of the first pump and a discharge valve on the downstream side of the first pump, and at least on the outer peripheral surface of the second plunger of the second pump. The step portion is formed along the driving direction of the plunger, the step portion and the inner wall surface of the second cylinder constitute the working chamber, and the liquid chromatograph pump is provided in the working chamber of the second pump. It is preferable that a discharge passage from the first pump is connected, a suction passage to the liquid chromatograph pump is connected to a working chamber configured in the first pump, and the first pump and the second pump are serially coupled.

  In order to achieve the first object, a liquid chromatograph pump according to the present invention is a liquid chromatograph pump comprising a cylinder and a plunger that reciprocates in the cylinder. The step portion is formed along the driving direction of the plunger, and the working chamber is constituted by the step portion and the inner wall surface of the cylinder, and the end opposite to the driving side of the plunger is in a gas atmosphere. It is what I did. At this time, the first pump having a first plunger that reciprocates within the first cylinder and the first cylinder, and the second plunger that reciprocates within the second cylinder and the second cylinder. A suction pump on the upstream side of the first pump and a discharge valve on the downstream side of the first pump, and at least on the outer peripheral surface of the second plunger of the second pump. The step portion is formed along the driving direction of the second plunger, the working chamber is constituted by the step portion and the inner wall surface of the second cylinder, and is on the side opposite to the driving side of the second plunger. It is preferable that the end is provided in a gas atmosphere, and the second pump is disposed on the most downstream side of the plurality of pumps configured in the liquid chromatograph pump. Alternatively, a first pump having a first cylinder and a first plunger reciprocating in the first cylinder, and a second pump having a second cylinder reciprocating in the second cylinder and the second cylinder. Two pumps, a suction valve on the upstream side of the first pump and a discharge valve on the downstream side of the first pump, and at least on the outer peripheral surface of the second plunger of the second pump. The step portion is formed along the driving direction of the plunger, the working portion is constituted by the step portion and the inner wall surface of the second cylinder, and the end opposite to the driving side of the second plunger A discharge passage from the liquid chromatograph pump is connected to the working chamber of the second pump, and the suction to the liquid chromatograph pump is placed in the working chamber configured of the first pump. Connect passage , It may coupling the second pump and the first pump in series.

  The liquid chromatograph pump includes an eluent storage container that stores an eluent sent by the liquid chromatograph pump, and a low-pressure pump is installed between the eluent storage container and the first pump. A switching valve, a passage communicating with the eluent storage container and a passage communicating with the column are provided downstream of the second pump, and a passage communicating the switching valve with the eluent storage container at the start of a test; In addition, the low-pressure pump is driven to supply a large flow rate, and the eluent is filled into the downstream passage while discharging bubbles remaining in the pump and the passage. It is preferable that the first pump and the second pump feed a small flow rate so as to communicate with a passage communicating with the column side.

  In order to achieve the second object, a liquid chromatograph pump of the present invention is provided between a liquid chromatograph pump, a container for storing an eluent, and the liquid chromatograph pump and the container. A low-pressure pump, a first flow path for returning the eluent discharged from the liquid chromatograph pump to the container, and a second flow path for sending the eluent discharged from the liquid chromatograph pump to the injector And a switching valve for switching between the first flow path and the second flow path.

  The liquid chromatograph pump is particularly effective when the liquid flow rate is approximately 0.1 nL / min to 50 μL / min.

  According to the present invention, since the flow rate of the liquid feed can be determined by the pump configured by the step portion formed on the plunger, it is possible to provide a liquid chromatograph pump suitable for reducing the flow rate of the liquid feed.

  In addition, low-pressure liquid feeding is performed with a high-pressure pump, and eluent filling and bubble discharging at the start of the test are performed with a low-pressure pump, so solvent liquid filling and bubble discharging at the start of the test can be completed in a short time. It is possible to provide a liquid chromatograph pump capable of

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  1 and 2 are hydraulic circuit diagrams showing a schematic configuration of a liquid chromatograph feeding system to which a liquid chromatograph pump is applied, and FIG. 3 shows a schematic structure of a pump main body of the liquid chromatograph pump. FIG. 4 is a diagram showing a flow range of the pump, and FIG. 5 is a diagram showing an example of a method for driving the liquid chromatograph pump.

  1 to 3, the liquid feeding system is a liquid chromatograph pump that sucks and pressurizes the eluent 2 in the eluent storage container 1 through a degassing device (degasser) 3, a low pressure pump 4 and a suction pipe 5. 10 and an injector 50 that discharges the eluent from the liquid chromatograph pump 10 and injects a sample to be analyzed through the switching valve 6 and the discharge pipes 7a and 7b, and minute silica gel particles are contained inside. The column 51 packed in the column, the detector 52 that analyzes the components for each separated component, the controller 55 that outputs a drive signal to the motors 21 and 31 that drive the pump, and the pressure provided in the liquid chromatograph pump 10. And a pressure control valve 41 for adjusting the discharge pressure of the low-pressure pump 4, a discharge pipe 7a, Syneresis reservoir 1 and a bypass pipe 61 which communicates via the switching valve 6.

  The liquid chromatograph pump 10 includes a pump body 11, motors 21 and 31, speed reduction mechanisms 22 and 32, and linear motion mechanisms 23 and 33.

  The pump body 11 is formed with a suction passage 12, a first cylinder 13, a second cylinder 14, and a discharge passage 15, and the first plunger 16 and the second plunger 17 are provided in the first cylinder 13 and the second cylinder 14. Is slidably held by the bearings 24 and 34. A suction valve 18 is provided in the suction passage 12, and a discharge valve 19 is provided in an intermediate passage communicating the first cylinder 13 and the second cylinder 14. It is a check valve that limits the direction. That is, the suction valve 18 opens against the spring force when the first pump having the first cylinder 13 is in the suction stroke, and the discharge valve 19 opens against the spring force when the first pump is in the discharge stroke. , Each is biased by a spring.

  The rotation of the motor 21 is decelerated by the speed reduction mechanism 22, converted into a linear motion by the linear motion mechanism 23, and the first plunger 16 is reciprocated in the first cylinder 13. Similarly, the second plunger 17 is also reciprocated within the second cylinder 14 by an actuator comprising a motor 31, a speed reduction mechanism 32, and a linear motion mechanism 33.

  As shown in detail in FIG. 3, the first plunger 16 is formed of a large-diameter portion 16a on the motor side and a small-diameter portion 16b on the opposite side of the motor, and is provided with a step portion. The step portion and the inner wall of the first cylinder 13 constitute a first working chamber 25. That is, the step surface connecting the large-diameter portion 16a and the small-diameter portion 16b, the outer peripheral surface of the first plunger 16 that forms the small-diameter portion 16b, and the end surface of the first cylinder 13 in which the through-hole through which the small-diameter portion 16b passes are formed. The first working chamber 25 is constituted by the part. The seal 26 prevents liquid leakage from the large diameter portion 16a of the plunger 16, and the seal 27 prevents liquid leakage from the small diameter portion 16b.

  Similarly, a large diameter portion 17 a and a small diameter portion 17 b are formed on the second plunger 17, and a step portion is provided. A second working chamber 35 is formed by the step portion and the inner wall of the second cylinder 14. . The seals 36 and 37 provide oil tightness for the large diameter portion 17a and the small diameter portion 17b of the plunger.

  By forming the working chambers 25 and 35 by the stepped portion formed on the outer peripheral surfaces of the plungers 16 and 17 and the inner walls of the cylinders 13 and 14, the working chamber cross-sectional area crossing the driving direction of the plungers 16 and 17 can be miniaturized. It is easy, and it becomes possible to increase the drive amount of the plungers 16 and 17 to some extent and to carry out a small amount of liquid feeding. In addition, when the amount of liquid feeding is reduced, it is relatively easy to form such a step with a small and high accuracy than to increase the rotation accuracy of the motor or the feeding accuracy of the plungers 16 and 17. Conceivable.

  The tips of the small-diameter portions of the plungers 16 and 17 are exposed in a gas (in the present embodiment, air) atmosphere, and the end portions of the small-diameter coaxial plungers of the above-described different-diameter coaxial plungers are in the eluent atmosphere (flow path). This is very different from the case of That is, the distal end portions of the small diameter portions 16b and 17b are extended outside the working chambers 25 and 35, and are not placed in other working chambers. In this liquid chromatograph pump 10, a working chamber is provided only at the stepped portions formed on the plungers 16 and 17 in order to reduce the amount of liquid to be supplied, and the tip of the small diameter portions 16 b and 17 b is configured. Then, it is configured so that it does not work.

  Further, the tips of the small-diameter portions 16b and 17b are exposed to a gas atmosphere, which means that a precipitate such as an organic solvent adhering to the seal (for example, when an aqueous solution containing salt is fed, the salt becomes crystals and becomes a powder state. It is also convenient to remove the residue remaining on the seal.

  Hereinafter, in this embodiment, a portion including the first plunger 16 and an actuator for driving the first plunger 16 is referred to as a first pump, and a portion including the second plunger 17 and the actuator for driving the second plunger 17 is referred to as a second pump.

  Next, FIG. 4 is a diagram showing a flow range and classification of a liquid chromatograph pump (referred to as a high pressure pump). This embodiment is intended for a liquid chromatograph pump that feeds liquid at an extremely low flow rate such as micro (μl) and nano (nl) below semi-micro. As can be seen from an example of the flow rate range of the general-purpose pump shown in FIG. 4, the ratio between the minimum flow rate and the maximum flow rate is generally only about 100 times due to restrictions on the rotation speed range and rotation accuracy of the motor. Therefore, when the flow rate is set in the micro and nano regions, the maximum flow rate is naturally reduced. For this reason, it takes time to fill the eluent into the passage of the measurement system on the downstream side of the pump at the start of the test, and it is difficult to discharge bubbles accumulated in the pump. In particular, if air bubbles remain in the cylinder, there is a problem that even if the plunger reciprocates, the flow rate is not discharged simply by compressing and expanding the air bubble, or the flow rate is significantly reduced and accurate measurement cannot be performed. .

  Therefore, in the present embodiment, liquid feeding at an extremely low flow rate is performed by the above-described high-pressure pump, and eluent filling and bubble discharge at the start of the test are performed by a low-pressure pump.

  As shown in configuration examples 1 and 2 in FIG. 4, the flow rate range of the high-pressure pump is set so as to cover the micro and nano areas. On the other hand, the flow rate range of the low-pressure pump does not need to be set in particular.

  Here, the total liquid flow rate on the horizontal axis in FIG. 4 is the total liquid flow rate during high-pressure gradient operation, which will be described later, and the gradient operation changes the flow rate in several 10 to 100 steps. The minimum flow rate that can be delivered by the high-pressure pump is one or two digits lower.

  Here, the specification of the plunger diameter of the high-pressure pump when it is assumed that the gradient operation is performed in 100 stages will be described. Since the flow rate is the product of the cross-sectional area and speed of the plunger, it can be set by changing the diameter of the plunger, the rotational speed of the motor, the reduction ratio, and the like.

  Assuming that the diameter of the large-diameter portion shown in FIG. 3 is D, the diameter of the small-diameter portion is d, and the reduction ratio is 1/10 to 1/20 compared to that used in a general-purpose pump, D is Assuming 2 mm, in the case of the configuration example 1, d is about 1.5 mm. On the other hand, in the case of the configuration example 2, d is 1.99 to 1.98 mm.

  In the above configuration, a method for operating the liquid chromatograph pump will be described with reference to FIGS. 1, 2, and 5. 5 shows the displacement of the second plunger 17 from the top, the displacement of the first plunger 16, the speed of the second plunger 17, the speed of the first plunger 16, and the total flow rate passing through the discharge passage 11 with respect to the horizontal axis time. It is shown.

  First, when the bubbles inside the pump are discharged and filled with the solvent liquid as a preliminary stage of the test, the switching valve 6 is switched to the bypass pipe 61 side as shown in FIG. And the bypass pipe 61 are communicated to start the low-pressure pump 4. When the low-pressure pump 4 is operated, the eluent 2 in the eluent storage container 1 is sucked, and bubbles dissolved in the eluent are removed by the degassing device (degasser) 3. Here, a pressure control valve 41 for adjusting the discharge pressure is provided on the discharge side of the low-pressure pump 4, and the discharge pressure is normally set to 0.5 to 0.6 MPa or less, but this value is adjusted. It is possible. The discharged eluent passes through the suction passage 12, the suction valve 18, the first working chamber 25, the discharge valve 19, the intermediate passage, the working chamber 35, the discharge passage 15, the discharge pipe 7a, the switching valve 6 and the bypass pipe 61. Return to the eluent storage container 1.

  By disposing the low-pressure pump 4 on the upstream side and performing liquid feeding at a large flow rate, the bubbles accumulated in the high-pressure pump 10 on the downstream side can be easily discharged. In particular, in the high-pressure pump 10 of the present embodiment, the working chambers 25 and 35 are introduced by introducing a solvent liquid from the bottom dead center and discharged from the working chambers 25 and 35 from the top dead center. Care is taken to eliminate stagnation in 25 and 35 and to prevent bubbles from staying. Thereby, the test preparation can be completed in a time shorter than or equal to that of a general-purpose liquid chromatograph pump. During this time, there is no problem even if the high-pressure pump 10 is stopped or started.

  Next, when shifting to the steady operation, as shown in FIG. 1, the switching valve 6 is switched to the discharge pipe 7b side, and the discharge pipe 7a and the discharge pipe 7b of the high-pressure pump 10 are communicated to connect to the detector 52. Use a liquid feed line.

  Although the low-pressure pump 4 is activated, a low-flow rate liquid is fed by the high-pressure pump 10. The eluent 2 is sucked into the pump through the suction passage 12 and discharged from the discharge passage 15, and then a sample to be analyzed is injected by the injector 53 through the switching valve 6 and the discharge pipes 7 a and 7 b. The mixed solution enters the column 51 and is separated for each component and then analyzed by the detector 52. The column 51 is filled with fine silica gel particles, and a load pressure of about 10 MPa is generated in the high-pressure pump 10 due to fluid resistance when flowing through the column 51. The magnitude of the pressure varies depending on the diameter of the column 51 and the passing flow rate.

  An example of the drive pattern of the high-pressure pump 10 is shown in FIG. 5, but the flow rate is proportional to the plunger speed, so the speed waveform is equivalent to the flow rate waveform.

  The driving of the first plunger 16 and the second plunger 17 is controlled so that the sum of the speeds of the first plunger 16 and the second plunger 17 is always constant, that is, the total flow rate is always constant. In the present embodiment, the first pump and the second pump are configured with the same specifications. That is, the first plunger 16 and the first working chamber 25 and the second plunger 17 and the second working chamber 35 are configured to have the same size and shape. When the second plunger 17 is in the discharge stroke, the discharge valve 19 (which is a suction valve when viewed from the second pump side) is closed, and the driving speed of the second plunger 17 and the disconnection of the second working chamber 35 are closed. Liquid is fed from the discharge passage 15 at a flow rate determined by the area. At this time, the first plunger 16 is in the suction stroke, and the suction valve 18 is open. When the second plunger 17 enters the suction stroke, the first plunger 16 enters the discharge stroke, the suction valve 18 is closed, and the discharge valve 19 is opened. The first plunger 16 is driven at a speed twice that of the second plunger 17 and discharges liquid at substantially the same flow rate as the first pump discharges in the discharge stroke while compensating the second pump.

  As described above, in the present embodiment, not only when the second pump is in the discharge stroke, but also when the second pump is in the suction stroke, liquid feeding is performed at a flow rate that the second pump discharges in the discharge stroke. For this reason, pulsation generated in the flow rate discharged from the liquid chromatograph pump 10 is reduced, and stable liquid feeding with less pulsation can be performed.

  In such an operation method of the liquid chromatograph pump 10, the discharge flow rate of the first pump having the first plunger 16 is larger than the discharge flow rate of the second pump having the second plunger 17. There may be a case where it is not necessary to make the working chamber cross-sectional area as small as the working chamber cross-sectional area of the second pump. In this case, it is also conceivable that the working chamber of the first pump is configured at the tip portion instead of the step portion of the first plunger 16. However, when the flow rate is not so different between the plurality of pumps as in this embodiment, or when the flow rate is very small, all the working chambers 25 and 35 of the plurality of pumps are formed in the plungers 16 and 17. It is preferable to form the stepped portion. As a result, it is possible to reduce the amount and stabilize the liquid feeding.

  In any case, among the plurality of pumps provided in the liquid chromatograph pump 10 in order to reduce the amount of liquid fed by the liquid chromatograph pump 10, the pump disposed closest to the discharge passage 15 The working chamber 35 (the working chamber 35 to which the inlet of the discharge passage 15 is connected) is configured at the step portion of the plunger 17, and the tip of the small-diameter portion 17b of the plunger 17 is exposed in a gas atmosphere. It is. Alternatively, among the pumps arranged in multiple stages, the pump operating chamber 35 arranged on the most downstream side is configured at the stepped portion of the plunger 17, and the tip end portion of the small diameter portion 17b of the plunger 17 is exposed in a gas atmosphere. It has been made. Alternatively, the flow rate discharged from the liquid chromatograph pump 10 is determined by the cross-sectional area or volume of the second pump or the working chamber 35 constituted by the step portion of the plunger 17.

  Next, FIG. 6 shows an example in which a high-pressure gradient system is constructed using two liquid feeding systems of the present invention. The gradient operation is an operation method in which the mixing ratio of the two types of eluents A and B is changed stepwise with time, and the ratio of Qa and Qb is set while keeping the total liquid flow rate (= Qa + Qb). The test is performed by changing.

  FIG. 7 shows the time change of each part in the gradient operation. When Qa + Qb is constant at 100, the initial operation starts from Qa: Qb = 1: 99, 2:98, 3:97,... : 50, ..., 99: 1. This is a case of a gradient of 100 stages. When the total liquid feeding flow rate is 1 μL / min, the minimum flow rate and resolution are required to be 1/100 of 10 nL / min. As shown in the figure, even when a constant flow rate is flowing, the fluid resistance when passing through the column changes due to the change in the composition of the fluid due to mixing, and the discharge pressure of the pump may change up to about 1.5 to 2 times. Are known. For this reason, if the pressure is kept constant, the flow rate will fluctuate.

  On the other hand, since the relationship between the mixing ratio and the pressure fluctuation is known in advance from past experimental data, the pressure fluctuation curve when the flow rate is constant can be predicted. Therefore, if the theoretical value of the pressure fluctuation curve is set as a target value, and the pump is driven by pressure sensor signal feedback to match the actual pressure to the target pressure, a constant total liquid feeding flow rate can be obtained with high accuracy. Specifically, the signal of the pressure sensor 60a in FIG. 6 is fed back to the main controller 70, and the controllers 55 and 55 'of each pump are controlled to cause the pressure to follow the target pressure. Since the discharge passages of both pumps communicate with each other via the mixer 53, the pressure is almost the same in any part, and either signal from the pressure sensors 60a and 60b may be used.

  At this time, if the actual pressure is lower than the target pressure, it means that the total liquid supply flow rate (= Qa + Qb) is reduced. Therefore, the flow rate is increased by increasing the number of revolutions of the motor, but either Qa or Qb is reduced. It cannot be determined from one piece of pressure sensor information. Actually, if Qa is lowered but Qb is judged to be lowered and correction is performed, the mixture ratio accuracy is deteriorated. This is a problem called mutual interference in gradient operation.

  In order to avoid this, in the present embodiment, correction is performed assuming that Qa and Qb are decreased at the same rate. This can be realized by providing a feedback gain proportional to the flow rate ratio as shown. For example, the feedback gains of Qa and Qb when the flow rate ratio of Qa: Qb is 20:80 are given by (20/100) × K and (80/100) × K, respectively. K is a constant. Assuming that the total liquid flow rate is 5 short and proportional control is performed, the command values of Qa and Qb are 20+ (20/100) × K × 5 and 80+ (80/100) × K × 5, respectively. Given. For example, if K is 1, the former is 21 and the latter is 84. According to this method, although the deterioration of mixing accuracy due to the difference between the two pumps is inevitable, the problem of mutual interference can be avoided, so that further reduction of mixing accuracy can be prevented.

  In addition, since the discharge pressure is changing with time, it is necessary to change the pressure of the 1st working chamber of both pumps according to this. In particular, when the pressure in the pressure sensors 60a and 60b is lower than the pressure in the first working chamber, the discharge valve opens and the eluent in the first working chamber flows into the second working chamber, increasing the liquid feed flow rate. End up. For this reason, in this embodiment, pressure sensors 60a 'and 60b' are provided in the first working chambers of both pumps, and this signal is fed back to the controllers 55 and 55 'to drive the first plunger, so that the pressure in the first working chamber is increased. Is controlled to be equal to the discharge pressure measured by the pressure sensor 60a.

  As described above, a high-pressure gradient system excellent in liquid feeding stability and mixing accuracy can be provided.

  In the above description, the liquid feeding system to which the liquid chromatograph pump according to the present invention is applied as a direct drive by a motor has been described as an example, but the present invention is not limited thereto. That is, for example, the liquid chromatograph pump according to the present invention may be applied as a cam drive by a motor. FIG. 8 is a hydraulic circuit diagram showing an example of a schematic configuration of such another liquid feeding system. In FIG. 8, the same reference numerals are given to the parts equivalent to the application target, and the description will be omitted as appropriate.

  The liquid feeding system shown in FIG. 8 is provided integrally with a cam shaft 80 of a liquid chromatograph pump, a motor 82 connected to rotationally drive the cam shaft 80 via a speed reducer 81, and the cam shaft 80. First and second cams 83, 84, first roller follower 85 and second roller follower 86 that rotate and slide with each cam, bearings 87 and 88 that rotatably support cam shaft 80, and cam An angle sensor 89 provided on the shaft 80 for detecting the rotation angle of the cam and a controller 75 for outputting a control signal to the motor 82 are provided.

  The controller 75 inputs detection signals of the pressure sensor 60 and the angle sensor 89 provided in the pump 10, performs predetermined calculation processing based on these detection signals, and outputs the generated drive command signal to the motor 82. .

  In the above configuration, a method for operating the liquid chromatograph pump of the present embodiment will be described with reference to FIGS. 9 shows the displacement of the second plunger 17, the displacement of the first plunger 16, the speed of the second plunger 17, the speed of the first plunger 16, and the total flow rate passing through the discharge passage 11 from the top with respect to the horizontal axis time. It is shown.

  The operation mode in which the bubbles inside the pump are discharged and filled with the solvent liquid as the pre-stage of the test is the same as described above, so it is omitted and the steady operation mode will be described.

  The switching valve 6 is switched to the discharge pipe 7b side, and the discharge pipe 7a and the discharge pipe 7b of the high-pressure pump 10 are communicated to form a liquid feed line connected to the detector 52. The speeds of the first plunger 16 and the second plunger 17 are changed. Control is performed so that the sum is always constant, that is, the total flow rate is always constant, and the first plunger 16 moves at a speed twice that of the second plunger 17, and the liquid is supplied while filling the second pump. When the first pump is in the suction stroke, the suction valve acts so that the liquid is fed only by the second pump.

  With the above configuration, a liquid chromatograph pump can be configured with a single motor, so that the liquid feeding system can be made compact.

  When this flow rate is extremely low, the actuator does not have to be a motor + linear motion mechanism or a motor + cam drive mechanism. For example, the displacement is controlled by temperature control using the thermal expansion of a piezoelectric actuator or metal. Applicable to any actuator.

  Here, a method for controlling displacement by temperature control using thermal expansion of metal will be described. If the minimum flow rate of the pump is 0.1 nL / min (this flow rate is the pump discharge when the gradient is 100 steps in the configuration example 2 in FIG. 4) and the plunger diameter is φ2, the average feed rate of the plunger Is 3.2 × 10 −5 mm / min. On the other hand, since the linear expansion coefficient of iron is 1.2 × 10 −5 / ° C., the average feed rate of the plunger is in the same order as the linear expansion coefficient of iron. Therefore, by directly or indirectly controlling the plunger at a temperature of 1 ° C./min, the plunger can be displaced and the discharge amount can be fed. As means for realizing the above-described temperature control, there are a thermo module (a semiconductor cooling element that generates a temperature difference when an electric current flows), a refrigerating air conditioner, and the like.

  With the configuration as described above, since the mechanical element is not included in the means for displacing the plunger, there is an effect that the reliability and maintenance of the system becomes easy.

  In this embodiment, two working chambers are configured in one pump body and connected by a passage. However, a system may be configured by separately providing pump heads and connecting them by piping. This facilitates disassembly of the pump and facilitates maintenance work such as seal replacement. In addition, advantages such as improved device layout can be obtained.

  In the above description, the field of use of the present invention has been described for liquid chromatographs in the field of medical equipment. It is obvious that the present invention can be applied to any pump for feeding liquid.

It is a hydraulic circuit diagram showing the schematic structure of the liquid feeding system which is the application object of the pump for liquid chromatographs of this invention. It is a hydraulic circuit diagram showing the schematic structure of the liquid feeding system which is the application object of the pump for liquid chromatographs of this invention. It is an expanded sectional view showing the schematic structure of the pump main part of the pump for liquid chromatographs of the present invention. It is a figure which shows the flow range of the pump of this invention. It is a figure which shows an example of the drive method of the pump for liquid chromatographs of this invention. It is a figure which shows an example of the system configuration | structure using the pump for liquid chromatographs of this invention. It is a figure which shows an example of the drive method of the pump for liquid chromatographs of this invention. It is a hydraulic circuit diagram showing the schematic structure of the liquid feeding system as an example of the other application object of the pump for liquid chromatographs of this invention. It is a figure which shows an example of the drive method of the pump for liquid chromatographs of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Eluent storage container, 2 ... Eluent, 3 ... Deaeration device (degasser), 4 ... Low pressure pump, 5 ... Intake pipe, 6 ... Switching valve, 7a, 7b ... Discharge pipe, 10 ... Liquid chromatograph pump , 11 ... pump body, 12 ... suction passage, 13 ... first cylinder, 14 ... second cylinder, 15 ... discharge passage, 16 ... first plunger, 16a ... large diameter portion, 16b ... small diameter portion, 17 ... second plunger 17a ... large diameter part, 17b ... small diameter part, 18 ... suction valve, 19 ... discharge valve, 21, 31 ... motor, 22, 32 ... deceleration mechanism, 23,33 ... linear motion mechanism, 24 ... bearing, 24 ... first 1 working chamber, 26, 27 ... seal, 35 ... second working chamber, 41 ... pressure control valve, 50 ... injector, 51 ... column, 52 ... detector, 53 ... mixer, 55 ... controller, 60 ... pressure sensor, 70 ... host controller.

Claims (8)

In a liquid chromatograph pump comprising a cylinder and a plunger that reciprocates in the cylinder,
A stepped portion is formed on the outer peripheral surface of the plunger along the driving direction of the plunger, and a working chamber is constituted by the stepped portion and the inner wall surface of the cylinder. A cross-sectional area of the working chamber and a driving speed of the plunger And determines the flow rate of the liquid chromatograph pump,
A first pump having a first cylinder and a first plunger that reciprocates in the first cylinder; a second pump that reciprocates in the second cylinder and the second cylinder; A second pump located downstream of one pump,
The liquid chromatograph pump, wherein the discharge flow rate of the first pump is larger than the discharge flow rate of the second pump.   2. The liquid chromatograph pump according to claim 1, wherein an intake valve is provided upstream of the first pump and a discharge valve is provided downstream of the first pump, and at least the second plunger of the second pump is provided. The step portion is formed on the outer peripheral surface along the driving direction of the second plunger, the working portion is constituted by the step portion and the inner wall surface of the second cylinder, and the second pump is connected to the liquid. A liquid chromatograph pump characterized by being arranged on the most downstream side of a plurality of pumps configured in a chromatograph pump.   2. The liquid chromatograph pump according to claim 1, wherein an intake valve is provided upstream of the first pump and a discharge valve is provided downstream of the first pump, and at least the second plunger of the second pump is provided. The step portion is formed on the outer peripheral surface along the driving direction of the second plunger, the working chamber is constituted by the step portion and the inner wall surface of the second cylinder, and the working chamber of the second pump. A discharge passage from the liquid chromatograph pump, and a suction passage to the liquid chromatograph pump is connected to a working chamber configured in the first pump, and the first pump and the second pump, A liquid chromatograph pump characterized by serially connecting the two. In a liquid chromatograph pump comprising a cylinder and a plunger that reciprocates in the cylinder,
A stepped portion is formed on the outer peripheral surface of the plunger along the driving direction of the plunger, and an operating chamber is constituted by the stepped portion and the inner wall surface of the cylinder, and an end portion opposite to the driving side of the plunger Is in a gas atmosphere,
A first pump having a first cylinder and a first plunger that reciprocates in the first cylinder; a second pump that reciprocates in the second cylinder and the second cylinder; A second pump located downstream of one pump,
The liquid chromatograph pump, wherein the discharge flow rate of the first pump is larger than the discharge flow rate of the second pump.   5. The liquid chromatograph pump according to claim 4, wherein an intake valve is provided upstream of the first pump and a discharge valve is provided downstream of the first pump, and at least the second plunger of the second pump is provided. The step portion is formed on the outer peripheral surface along the driving direction of the second plunger, the working chamber is constituted by the step portion and the inner wall surface of the second cylinder, and the driving of the second plunger A liquid chromatograph characterized in that an end opposite to the side is provided in a gas atmosphere, and the second pump is disposed on the most downstream side of a plurality of pumps configured in the liquid chromatograph pump. Pump.   5. The liquid chromatograph pump according to claim 4, wherein an intake valve is provided upstream of the first pump and a discharge valve is provided downstream of the first pump, and at least the second plunger of the second pump is provided. The step portion is formed on the outer peripheral surface along the driving direction of the second plunger, the working chamber is constituted by the step portion and the inner wall surface of the second cylinder, and the driving of the second plunger An end opposite to the side is provided in a gas atmosphere, a discharge passage from the liquid chromatograph pump is connected to the working chamber of the second pump, and the liquid is placed in the working chamber configured in the first pump. A liquid chromatograph pump, wherein a suction passage to a chromatograph pump is connected, and the first pump and the second pump are serially coupled.   The liquid chromatograph pump according to any one of claims 2, 3, 5, or 6, further comprising an eluent storage container for storing an eluent sent by the liquid chromatograph pump, wherein the eluent reservoir is stored. A low pressure pump is installed between the container and the first pump, and a switching valve, a passage communicating with the eluent storage container and a passage communicating with the column are provided on the downstream side of the second pump. The switching valve communicates with a passage communicating with the eluent storage container, and the low pressure pump is driven to supply a large flow rate to discharge bubbles remaining in the pump and the passage to the downstream passage. The eluent is filled, and then the switching valve is communicated with a passage communicating with the column side so that a small flow rate is fed by the first pump and the second pump. Toss Liquid chromatograph pump.   The liquid chromatograph pump according to any one of claims 1, 4 and 7, wherein the range of the flow rate of the liquid is approximately 0.1 nL / min to 50 µL / min. .

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