阅读说明：本技术 送液装置 (Liquid feeding device ) 是由 小川佳祐 今村信也 于 2017-07-03 设计创作，主要内容包括：送液装置包括：一次侧柱塞泵；二次侧柱塞泵,在所述一次侧柱塞泵的下游与所述一次侧柱塞泵串联连接；止回阀,设于所述一次侧柱塞泵的出口与所述二次侧柱塞泵的入口之间；一次侧压力传感器,与所述一次侧柱塞泵的泵室连通,检测所述一次侧柱塞泵的泵室内的压力；送液控制部,构成为控制所述一次侧柱塞泵及所述二次侧柱塞泵的操作；以及漏液侦测部,构成为基于所述待机时间中的所述一次侧压力传感器的输出值的变化,而侦测所述止回阀的漏液。所述送液控制部构成为控制所述一次侧柱塞泵的操作,以在所述二次侧柱塞泵进行的喷出操作中且所述一次侧柱塞泵进行的抽吸结束后,存在所述一次侧柱塞泵停止而不操作的待机时间。(The liquid feeding device comprises: a primary side plunger pump; a secondary-side plunger pump connected in series with the primary-side plunger pump downstream of the primary-side plunger pump; a check valve provided between an outlet of the primary-side plunger pump and an inlet of the secondary-side plunger pump; a primary side pressure sensor that is communicated with the pump chamber of the primary side plunger pump and detects a pressure in the pump chamber of the primary side plunger pump; a liquid feed control unit configured to control operations of the primary-side plunger pump and the secondary-side plunger pump; and a leakage detecting unit configured to detect leakage of the check valve based on a change in an output value of the primary pressure sensor during the standby time. The liquid feeding control unit is configured to control the operation of the primary-side plunger pump so that there is a standby time during which the primary-side plunger pump stops and does not operate after the primary-side plunger pump finishes pumping during the discharge operation by the secondary-side plunger pump.)

1. A liquid feeding apparatus comprising:

a primary side plunger pump;

a secondary-side plunger pump connected in series with the primary-side plunger pump downstream of the primary-side plunger pump;

a check valve provided between an outlet of the primary-side plunger pump and an inlet of the secondary-side plunger pump;

a primary side pressure sensor that is communicated with a pump chamber of the primary side plunger pump and detects a pressure in the pump chamber of the primary side plunger pump;

a liquid feeding control unit configured to control operations of the primary-side plunger pump and the secondary-side plunger pump, and configured to control the operation of the primary-side plunger pump such that there is a standby time during which the primary-side plunger pump stops and does not operate after the pumping by the primary-side plunger pump is completed during the discharge operation by the secondary-side plunger pump; and

and a leakage detecting unit configured to detect leakage of the check valve based on a change in the output value of the primary pressure sensor during the standby time.

2. The liquid conveying apparatus according to claim 1, further comprising:

a relational expression holding unit that holds a relational expression that indicates a relationship between a rate of increase of an output value of the primary pressure sensor and a liquid leakage amount per unit time of the check valve,

the leakage detecting unit is configured to calculate a leakage amount per unit time of the check valve based on a rising rate of an output value of the primary pressure sensor during the standby time and the relational expression held in the relational expression holding unit.

3. The liquid feeding apparatus according to claim 2, further comprising:

a secondary side pressure sensor which is communicated with a pump chamber of the secondary side plunger pump and detects the pressure in the pump chamber of the secondary side plunger pump;

a pre-pressure operation unit configured to perform a pre-pressure operation that causes the primary-side plunger pump to perform a discharge operation until an output value of the primary-side pressure sensor and an output value of the secondary-side pressure sensor become substantially the same, during the discharge operation by the secondary-side plunger pump and after the standby time elapses; and

a relational expression derivation unit configured to obtain the relational expression based on a drive amount of a plunger of the primary side plunger pump and a rate of increase in an output of the primary side pressure sensor during execution of the pre-compression operation, and the relational expression derivation unit is configured to derive the relational expression

The relational expression holding unit is configured to hold the relational expression derived by the relational expression deriving unit.

4. The liquid feeding apparatus according to claim 2 or 3, wherein the liquid feeding control portion is configured to, when the liquid leakage detecting portion detects the liquid leakage at the check valve, increase the discharge speed of the secondary side plunger pump based on the amount of the liquid leakage calculated by the liquid leakage detecting portion, thereby compensating for the lack of the liquid feeding flow rate due to the liquid leakage.

Technical Field

The present invention relates to a double plunger (double plunger) type liquid feeding apparatus for feeding a mobile phase in a liquid chromatograph (liquid chromatograph), and more particularly to a tandem type double plunger type liquid feeding apparatus in which a primary side plunger pump and a secondary side plunger pump are connected in series.

Background

As one of liquid feeding apparatuses for liquid chromatographs, a tandem type double-plunger type liquid feeding apparatus is known. The tandem type double-plunger type liquid feeding device has a primary side plunger pump and a secondary side plunger pump connected in series with the primary side plunger pump. The primary-side plunger pump and the secondary-side plunger pump are operated in a complementary manner to each other so as to stably feed liquid at a predetermined flow rate (see, for example, patent document 1).

During the period in which the primary-side plunger pump performs the discharge operation, the secondary-side plunger pump performs the suction operation, and the secondary-side plunger pump sucks a part of the liquid discharged by the primary-side plunger pump. After the discharge operation of the primary-side plunger pump is completed, the secondary-side plunger pump performs the discharge operation, and the primary-side plunger pump performs the suction of the liquid during this period.

[ Prior art documents ]

[ patent document ]

[ patent document 1] U.S. Pat. No. 5637208 publication

Disclosure of Invention

[ problems to be solved by the invention ]

In the tandem type double-plunger type liquid feeding device as described above, a check valve is provided between an outlet of the primary-side plunger pump and an inlet of the secondary-side plunger pump, and the check valve prevents the liquid from flowing back to the primary-side plunger pump when the secondary-side plunger pump performs the discharge operation.

However, the liquid tightness between the valve body and the valve seat of the check valve may be deteriorated, and liquid leakage may occur. If a leak occurs in the check valve between the outlet of the primary-side plunger pump and the inlet of the secondary-side plunger pump, a part of the liquid discharged from the secondary-side plunger pump flows toward the primary-side plunger pump, and the liquid feed flow rate in the discharge process by the secondary-side plunger pump does not reach the set flow rate, so that the liquid feed at a constant flow rate cannot be realized, and pulsation occurs, which deteriorates reproducibility of the retention time of the analysis.

Conventionally, there is no method of detecting a reverse flow from the secondary-side plunger pump to the primary-side plunger pump. Therefore, if the control accuracy of the liquid feeding flow rate is lowered, it is difficult to take appropriate measures.

Therefore, an object of the present invention is to detect leakage at a check valve between a primary-side plunger pump and a secondary-side plunger pump.

[ means for solving problems ]

The liquid feeding device of the present invention includes: a primary side plunger pump; a secondary-side plunger pump connected in series with the primary-side plunger pump downstream of the primary-side plunger pump; a check valve provided between an outlet of the primary-side plunger pump and an inlet of the secondary-side plunger pump; a primary side pressure sensor that is communicated with the pump chamber of the primary side plunger pump and detects a pressure in the pump chamber of the primary side plunger pump; a liquid feeding control unit configured to control operations of the primary-side plunger pump and the secondary-side plunger pump, and configured to control the operation of the primary-side plunger pump such that there is a standby time during which the primary-side plunger pump stops and does not operate after the pumping by the primary-side plunger pump is completed during the discharge operation by the secondary-side plunger pump; and a leakage detecting unit configured to detect leakage of the check valve based on a change in an output value of the primary pressure sensor during the standby time.

The liquid feeding device of the present invention is provided with a primary side pressure sensor for detecting the pressure in a pump chamber of the primary side plunger pump. The primary-side plunger pump is configured to perform suction of the liquid after the completion of the discharge operation thereof and the start of discharge by the secondary-side plunger pump, and then to stop the operation for a certain period of time. The time during which the primary-side plunger pump stops after the completion of pumping is referred to as "standby time".

The pressure in the pump chamber of the primary-side plunger pump after the primary-side plunger pump sucks the liquid is usually atmospheric pressure. Therefore, the operation of the primary-side plunger pump is maintained at atmospheric pressure for the "standby time" during which the operation is stopped. However, when leakage occurs in the check valve between the primary-side plunger pump and the secondary-side plunger pump, the liquid flowing backward from the secondary-side plunger pump flows into the pump chamber of the primary-side plunger pump, and the pressure in the pump chamber of the primary-side plunger pump rises. Thereby, the output value of the primary side pressure sensor rises.

That is, by monitoring the output value of the primary side pressure sensor during the standby time, leakage of the check valve between the primary side plunger pump and the secondary side plunger pump can be detected. Therefore, the leakage detecting section monitors the output value of the primary side pressure sensor during the standby time and detects leakage based on a change in the output value.

Further, the pressure in the pump chamber of the primary-side plunger pump in the "standby time" in which the operation of the primary-side plunger pump is stopped increases in proportion to the amount of liquid flowing back from the secondary-side plunger pump into the pump chamber of the primary-side plunger pump. This makes it possible to calculate the reverse flow rate of the liquid to the primary-side plunger pump side, that is, the amount of leakage of the check valve, based on the rate of increase in the output value of the primary-side pressure sensor.

Therefore, in a further preferred embodiment of the liquid feeding apparatus of the present invention, the liquid feeding apparatus further includes: the leakage detection unit is configured to calculate the amount of leakage per unit time of the check valve based on the rate of rise of the output value of the primary-side pressure sensor during a standby time during which the primary-side plunger pump is stopped and the relational expression held in the relational expression holding unit.

The relationship between the rate of increase of the output value of the primary side pressure sensor and the amount of leakage of the check valve can also be obtained in advance through experiments. However, the relationship between the rate of increase of the output value of the pressure sensor of the primary pressure sensor and the amount of leakage liquid at the check valve varies depending on the compressibility of the liquid, and the compressibility of the liquid varies depending on the composition, temperature, and the like of the liquid.

Therefore, in order to obtain a more accurate relational expression, the liquid feeding device may have a function of deriving the relational expression. To derive the relational expression, the preliminary pressing operation of the primary-side plunger pump can be utilized. The "pre-pressure operation" herein means that the primary-side plunger pump is caused to perform the discharge operation until the pressure in the pump chamber of the primary-side plunger pump and the pressure in the pump chamber of the secondary-side plunger pump become substantially the same during the discharge operation of the secondary-side plunger pump and after the elapse of the standby time. The phrase "the pressure in the pump chamber of the primary-side plunger pump is substantially the same as the pressure in the pump chamber of the secondary-side plunger pump" means that the pressure in the pump chamber of the primary-side plunger pump is substantially the same as the pressure in the pump chamber of the secondary-side plunger pump, and the pressure in the pump chamber of the primary-side plunger pump is slightly lower than the pressure in the pump chamber of the secondary-side plunger pump.

Further, the possibility of deriving the relational expression in the pre-compression operation is limited to a case where leakage is not generated at the check valve between the primary-side plunger pump and the secondary-side plunger pump. This is because, if leakage occurs in the check valve between the primary-side plunger pump and the secondary-side plunger pump, the pressure in the pump chamber of the primary-side plunger pump reaches the same level as the pressure in the pump chamber of the secondary-side plunger pump in the "standby time" before the pre-pressing operation, and therefore the pre-pressing operation is finished without performing the discharge operation by the primary-side plunger pump.

Therefore, in a further preferred embodiment of the liquid feeding apparatus of the present invention, the liquid feeding apparatus further includes: the secondary side pressure sensor is communicated with a pump chamber of the secondary side plunger pump and is used for detecting the pressure in the pump chamber of the secondary side plunger pump; a pre-pressure operation unit configured to perform a pre-pressure operation that causes the primary-side plunger pump to perform a discharge operation until an output value of the primary-side pressure sensor and an output value of the secondary-side pressure sensor become substantially the same, during the discharge operation by the secondary-side plunger pump and after a standby time elapses; and a relational expression derivation unit that obtains the relational expression based on a drive amount of a plunger of the primary-side plunger pump and a rate of increase in an output of the primary-side pressure sensor during execution of the pre-compression operation. The relational expression derived by the relational expression deriving unit is held in the relational expression holding unit.

In a further preferred embodiment, the liquid feed control unit is configured to compensate for a lack of the liquid feed flow rate due to the leakage by increasing the discharge speed of the secondary side plunger pump based on the leakage amount calculated by the leakage detecting unit when the leakage at the check valve is detected by the leakage detecting unit. The term "compensating for the lack of the liquid feeding flow rate due to the leakage" means that the leakage amount is added to increase the discharge speed of the secondary-side plunger pump, thereby setting the liquid feeding flow rate to the set flow rate. For example, when the set flow rate is α μ L/min and the calculated leakage amount is β μ L/min, the discharge speed of the secondary-side plunger pump is controlled so that the discharge flow rate from the secondary-side plunger pump becomes (α + β) μ L/min. In this way, by compensating for the lack of the liquid feed flow rate due to the liquid leakage by using the discharge speed of the secondary-side plunger pump, even when the liquid leakage occurs in the check valve between the outlet of the primary-side plunger pump and the inlet of the secondary-side plunger pump, the liquid feed flow rate can be stabilized by suppressing the decrease in the liquid feed flow rate in the discharge process of the secondary-side plunger pump and suppressing the occurrence of pulsation.

[ Effect of the invention ]

The liquid feeding device of the present invention detects leakage of the check valve based on a change in the output value of the primary pressure sensor when the primary-side plunger pump is stopped and the secondary-side plunger pump performs a discharge operation, and therefore can quickly detect leakage of the check valve provided between the outlet of the primary-side plunger pump and the inlet of the secondary-side plunger pump. If the leakage in the check valve can be detected, the discharge speed of the secondary-side plunger pump can be increased so as to cope with the leakage, and the decrease in the liquid feed flow rate can be suppressed, so that the liquid feed flow rate can be stabilized.

Drawings

Fig. 1 is a schematic cross-sectional configuration view showing an embodiment of a liquid feeding device.

Fig. 2 is a flowchart showing the operations of the primary-side plunger pump, the secondary-side plunger pump, and the control device in the liquid feeding when no liquid leakage occurs at the check valve of the embodiment.

Fig. 3 is a flowchart showing the operations of the primary-side plunger pump, the secondary-side plunger pump, and the control device in the liquid supply when a leak occurs at the check valve according to the embodiment.

Fig. 4 is a graph showing a temporal change in the measured value of each of the primary pressure sensor and the secondary pressure sensor.

Detailed Description

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

First, the configuration of the liquid feeding device will be described with reference to fig. 1.

The liquid feeding device 1 of the present embodiment includes a primary-side plunger pump 2 and a secondary-side plunger pump 22. The primary-side plunger pump 2 and the secondary-side plunger pump 22 are connected in series with each other.

The primary-side plunger pump 2 includes a pump head 3 having a pump chamber 4 therein, and a pump body 6. The pump head 3 is provided at the front end of the pump body 6. The pump head 3 is provided with an inlet portion for allowing liquid to flow into the pump chamber 4 and an outlet portion for allowing liquid to flow out of the pump chamber 4. A check valve 16 for preventing reverse flow of liquid is provided at an inlet of the pump head 3.

The front end of the plunger 10 is slidably inserted into the pump chamber 4. The proximal end of the plunger 10 is held by a crosshead (crosshead)8 housed in the pump body 6. The crosshead 8 moves in one direction (left-right direction in the drawing) in the cylinder 6 by the rotation of the feed screw 14, and the plunger 10 moves in one direction in association with this. A primary-side plunger pump driving motor 12 for rotating a feed screw 14 is provided at a base end portion of the pump body 6. The primary-side plunger pump driving motor 12 is a stepping motor (stepper).

The secondary plunger pump 22 includes a pump head 23 having a pump chamber 24 therein, and a pump body 28. The pump head 23 is provided at the front end of the pump body 28. The pump head 23 is provided with an inlet portion for allowing liquid to flow into the pump chamber 24 and an outlet portion for allowing liquid to flow out of the pump chamber 24. A check valve 26 for preventing reverse flow of liquid is provided at an inlet of the pump head 23.

The front end of the plunger 32 is slidably inserted into the pump chamber 24. The proximal end of the plunger 32 is held by a crosshead 30 housed in the pump body 28. The crosshead 30 moves in one direction (left-right direction in the drawing) in the cylinder 28 by the rotation of the feed screw 36, and the plunger 32 moves in one direction in association with this. A secondary plunger pump driving motor 34 for rotating a feed screw 36 is provided at a base end portion of the pump body 28. The secondary plunger pump driving motor 34 is a stepping motor.

An inlet of the pump head 3 is connected to a container (not shown) for accumulating liquid to be delivered via a flow path. The inlet of the pump head 23 is connected to the outlet of the pump head 3 via the connecting passage 18. The connection flow path 18 is provided with a primary side pressure sensor 20 that detects the pressure (P1) in the pump chamber 4.

An outlet passage 38 is connected to an outlet portion of the pump head 23. The outlet channel 38 leads to an analysis channel of a liquid chromatograph, for example. A secondary pressure sensor 40 that detects the pressure (P2) in the pump chamber 24 is provided in the outlet flow path 38.

The operations of the primary-side plunger pump driving motor 12 and the secondary-side plunger pump driving motor 34 are controlled by the control unit 42. The control section 42 includes a liquid feeding control section 44, a liquid leakage detecting section 46, a preliminary pressure operating section 48, a relational expression holding section 50, and a relational expression deriving section 52. The control device 42 is implemented by a dedicated computer or a general-purpose personal computer (personal computer). The liquid feeding control Unit 44, the liquid leakage detection Unit 46, the preliminary pressing operation Unit 48, and the relational expression derivation Unit 52 are functions obtained by executing a predetermined program by an arithmetic element such as a Central Processing Unit (CPU) provided in the control device 42. The relational expression holding unit 50 is a function realized by using a part of a storage area of a storage device provided in the control device 42.

The liquid feeding control unit 44 is configured to control the operations of the primary-side plunger pump 2 and the secondary-side plunger pump 22 such that the primary-side plunger pump 2 and the secondary-side plunger pump 22 operate complementarily to feed liquid at a predetermined flow rate.

The leakage detecting unit 46 is configured to detect leakage of the check valve 26 and calculate the amount of leakage based on the output value of the primary side pressure sensor 20 during a "standby time" in which the secondary side plunger pump 22 performs a discharge operation and the primary side plunger pump 2 is stopped. The calculation of the "standby time" and the amount of leakage liquid will be described below.

The preload operation section 48 is configured to cause the primary-side plunger pump 2 to perform a preload operation described below after a "standby time" has elapsed while the secondary-side plunger pump 22 is performing a discharge operation.

The relational expression holding unit 50 holds a relational expression for calculating the amount of leakage of the check valve 26 based on the output value of the primary pressure sensor 20 by the leakage detecting unit 46. The relational expression held in the relational expression holding unit 50 represents the relationship between the rise value (rise rate) per unit time of the output value of the primary pressure sensor 20 and the amount of leakage per unit time of the check valve 26. The relational expression may be obtained in advance through experiments, or may be derived by the relational expression deriving unit 52 described below.

The relational expression derivation unit 52 is configured to derive the relational expression in the preliminary compression operation of the primary-side plunger pump 2. As for a specific derivation method, it will be described below.

Fig. 2 and 3 show an example of the operations of the primary-side plunger pump 2, the secondary-side plunger pump 22, and the control device 42, which are realized by the above-described units 44, 46, 48, 50, and 52. Fig. 2 shows an operation when no leak occurs in the check valve 26, and fig. 3 shows an operation when a leak occurs in the check valve 26.

First, an operation when no leakage occurs at the check valve 26 will be described with reference to fig. 1 and 2.

When the primary-side plunger pump 2 starts the liquid discharge operation (step S11), the liquid feed controller 44 starts the suction operation of the secondary-side plunger pump 22 (step S21). When the primary-side plunger pump 2 performs the discharge operation, the check valve 16 is closed and the check valve 26 is opened, and the liquid from the outlet portion of the pump head 3 is discharged to the outlet flow path 38 via the connecting flow path 18, the check valve 26, and the pump chamber 24. The secondary-side plunger pump 22 performs a pumping operation at a flow rate smaller than the discharge flow rate of the primary-side plunger pump 2, and part of the liquid discharged from the pump head 3 is accumulated in the pump chamber 24.

The liquid feeding control unit 44 ends the discharge operation of the primary-side plunger pump 2 at a predetermined timing, and at this time, causes the secondary-side plunger pump 22 to start the discharge operation (step S12, step S22). When the discharge operation of the secondary-side plunger pump 22 is started, the check valve 26 closes because the pressure in the pump chamber 24 is higher than the pressure in the pump chamber 4.

After the liquid feeding control unit 44 starts the discharge operation of the secondary-side plunger pump 22, the primary-side plunger pump 2 is caused to perform the suction operation at a high speed (step S13), and then stands by for a certain period of time. The time during which the primary-side plunger pump 2 stands by without operating after the pumping operation is finished is referred to as "standby time". During the standby time, the leakage detecting unit 46 monitors the output value P1 of the primary pressure sensor 20 and calculates the rate of increase thereof (step S31). When the leakage at the check valve 26 does not occur, the pressure in the pump chamber 4 of the primary-side plunger pump 2 is maintained at the atmospheric pressure without being varied, and therefore the rate of increase of the output value P1 of the primary-side pressure sensor 20 is almost equal to 0. At this time, the leakage detecting unit 46 determines that there is no leakage from the check valve 26 (step S32).

The "almost 0" rate of increase of the output value P1 includes a value that is considered to be equivalent to 0 in consideration of noise (noise) of the output signal of the primary side pressure sensor 20, even if the value is not completely 0. Whether or not the rate of increase of the output value P1 is "substantially 0" can be determined, for example, by whether or not the rate of increase of the output value P1 obtained by calculation exceeds a preset threshold value.

The preload operation unit 48 causes the primary-side plunger pump 2 to perform the preload operation until the discharge operation of the secondary-side plunger pump 22 is completed after the elapse of the predetermined standby time (step S14, step S15). The pre-pressure operation is an operation for setting the pressure in the pump chamber 4 of the primary-side plunger pump 2 to the same pressure as the pressure in the pump chamber 24 of the secondary-side plunger pump 22 before the discharge operation of the secondary-side plunger pump 22 is completed. In the above-described pre-compression operation, the pre-compression operation unit 48 takes in the output value P1 of the primary pressure sensor 20 and the output value P2 of the secondary pressure sensor 40, and performs discharge driving of the primary-side plunger pump 2 while performing feedback control so that the pressure in the pump chamber 4 and the pressure in the pump chamber 24 become substantially the same.

In the pre-compression operation, the relational expression derivation section 52 derives a relational expression between the rate of increase of the output value of the primary pressure sensor 20 and the amount of leakage per unit time of the check valve 26 (step S33). By monitoring the output value P1 of the primary pressure sensor 20 during the pre-compression operation, the amount of increase in the output value P1 of the primary pressure sensor 20 can be determined when the plunger 10 of the primary plunger pump 2 is driven in the discharge direction only a certain distance. This enables the characteristics (compressibility) of the liquid of the current liquid feed to be examined.

For example, the primary-side plunger pump 2 ejects 1.0 μ L of liquid when the stepping motor 12 is rotated by one pulse. When the stepping motor 12 is rotated by one pulse in the preliminary pressing operation, the pressure value detected by the primary side pressure sensor 20 rises by 5MPa, which can be calculated as 1.0 μ L/pulse/5.0 MPa/pulse being 0.2 μ L/MPa.

That is, when the pressure value P1 detected by the primary side pressure sensor 20 rises by 1MPa, it means that 0.2 μ L of liquid flows into the primary side pressure sensor 20. Therefore, when the amount of leakage at the check valve 26 is X (μ L/sec) and the rate of increase of the output value P1 of the primary side pressure sensor 20 is Δ P1(MPa/sec), the relational expression of X is found to be X0.2 × Δ P1.

The relational expression thus obtained is stored in the relational expression storage unit 50 (step S34).

Then, the liquid delivery control unit 44 ends the discharge operation of the secondary-side plunger pump 22 (step S23), and starts the discharge operation of the primary-side plunger pump 2 again (step S11).

Next, an operation when liquid leakage occurs in the check valve 26 will be described with reference to fig. 1 and 3.

The discharge operation of the primary-side plunger pump 2 (step S11) and the suction operation of the secondary-side plunger pump 22 (step S22) are the same as those when no leakage occurs at the check valve 26.

After the liquid feeding control unit 44 starts the discharge operation of the secondary-side plunger pump 22, the primary-side plunger pump 2 is caused to perform the suction operation at a high speed (step S13), and then stands by for a certain period of time. During the standby time, the leakage detecting unit 46 monitors the output value P1 of the primary pressure sensor 20 and calculates the rate of increase thereof (step S31). When the leakage occurs at the check valve 26, the pressure in the pump chamber 4 of the primary-side plunger pump 2 rises, and the rate of rise thereof increases in accordance with the amount of leakage per unit time at the check valve 26. The leakage detecting section 46 calculates the amount of leakage per unit time at the check valve 26 using the calculated rate of increase and the relational expression held in the relational expression holding section 50 (step S35).

The liquid feeding control unit 44 calculates the discharge speed (corrected discharge speed) of the secondary-side plunger pump for compensating for the lack of the liquid feeding flow rate due to the leakage, based on the leakage amount per unit time calculated by the leakage detecting unit 46 (step S36). For example, when the set value of the liquid delivery flow rate is 100 μ L/min, if the amount of liquid leakage at the check valve 26 calculated by the liquid leakage detecting unit 46 is 1 μ L/sec (60 μ L/min), the discharge flow rate of the secondary-side plunger pump 22 for compensating for the lack of the liquid delivery flow rate due to the liquid leakage can be calculated to be 100 μ L/min +60 μ L/min, 160 μ L/min.

The liquid feed control unit 44 calculates the discharge speed of the secondary-side plunger pump 22 so that the liquid of the flow rate thus calculated is discharged from the secondary-side plunger pump 22.

The secondary-side plunger pump 22 is operated at the discharge speed calculated by the liquid feeding control unit 44 (step S24). This makes up for the lack of the liquid feed flow rate due to the liquid leakage at the check valve 26 by the increase in the discharge speed of the secondary-side plunger pump 22, stabilizes the liquid feed flow rate, and suppresses the occurrence of pulsation.

Fig. 4 is verification data regarding a difference in liquid delivery pressure when the discharge speed of the secondary-side plunger pump 22 is not corrected when liquid leakage occurs at the check valve 26 and when the discharge speed is corrected. In the figure, the lower graph shows a temporal change in the measurement value (MPa) of the primary pressure sensor 20, and the upper graph shows a temporal change in the measurement value (MPa) of the secondary pressure sensor 40. In the verification, the discharge speed of the secondary-side plunger pump 22 is not corrected in the first half of the liquid feeding cycle, and the discharge speed of the secondary-side plunger pump 22 is corrected in the second half of the liquid feeding cycle so as to compensate for the lack of the liquid feeding flow rate due to the liquid leakage at the check valve 26.

If no leakage occurs in the check valve 26 provided between the primary-side plunger pump 2 and the secondary-side plunger pump 22, the pressure in the pump chamber 4 of the primary-side plunger pump 2 is maintained at atmospheric pressure during a standby time after the end of the suction operation (referred to as primary-side suction in the figure) of the primary-side plunger pump 2. However, in the above verification, it is found that the pressure rises immediately after the suction operation of the primary-side plunger pump 2 is completed, and leakage occurs in the check valve 26.

In the liquid feeding cycle in the first half of the discharge speed of the secondary-side plunger pump 22, which is not corrected, the liquid feeding pressure (the measurement value of the secondary-side pressure sensor 40) is lost due to leakage at the check valve 26, and pulsation of about 0.22MPa is generated. In contrast, it was found that the pulsation was suppressed to about 0.05MPa in the second half of the liquid feeding cycle in which the discharge speed of the secondary-side plunger pump 22 was corrected. It was thus confirmed that the discharge speed of the secondary-side plunger pump 22 was corrected to stabilize the liquid delivery flow rate, thereby obtaining the effect of suppressing pulsation.

[ description of symbols ]

1: liquid feeding device

2: primary side plunger pump

3. 23: pump head

4. 24: pump chamber

6. 28: pump body

8. 30: crosshead

10. 32: plunger piston

12. 34: motor with a stator having a stator core

14. 36: feed screw

16. 26: check valve

20: primary side pressure sensor

22: secondary side plunger pump

40: secondary side pressure sensor

42: control unit

44: flow rate control unit

46: liquid leakage detecting part

48: prepressing operation part

50: relational expression holding part

52: and a relational expression derivation unit.