JP2516332B2 - Fluid pump with temperature controller to keep mass flow rate constant - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pump mainly used as a liquid-sending pump for chromatography, and more particularly to a fluid flow rate and a mass flow rate of the fluid which are maintained at a constant temperature of the inflowing fluid and the pump chamber. The present invention relates to a fluid pump with a temperature control device that keeps the temperature constant.

2. Description of the Related Art Conventionally, a reciprocating piston type pump is generally used as a liquid delivery pump for chromatography such as HPLC and SFC (supercritical fluid chromatography). This type of fluid pump has a chamber communicating with an inflow passage having a check valve that allows only the inflow of fluid and an outflow passage having a check valve that allows only the outflow of fluid, and a piston in the chamber. The fluid is sucked and discharged by reciprocating. The discharge rate per unit time of this type of pump is expressed as follows: Q = K · Vc · N where K is efficiency, Vc is the volume change due to piston movement in volume, and N is the unit time. Number of strokes of piston per hit.

The above-mentioned discharge amount varies depending on the structure of the pump, the efficiency of the check valve, the compressibility of the fluid, and the magnitude of the back pressure. In short, the conventional fluid pump of this type delivers a constant volume of fluid per unit time. For changes in efficiency that cause temporal fluctuations,
It can be corrected quite well by monitoring back pressure and increasing / decreasing the number of strokes per unit time by a predetermined amount.

Problems to be Solved by the Invention However, when the organic solvent used in liquid chromatography or the like is, for example, methyl alcohol, the temperature is 1 ° C.
The volume expansion per unit reaches 0.12%, and even if the volumetric flow rate of the pump is constant, the mass flow rate greatly depends on the temperature. The effect of this temperature on the mass flow rate is shown in the graph of FIG. In the figure, the horizontal axis is temperature (° C), the dotted vertical axis is the volume flow rate (ml / min), the solid vertical axis is the mass flow rate (g / min), and the volume flow rate is 0.4 ml / min (diamond), 1.0 ml / min (Triangle), 5.0 ml / min
The mass flow rate (solid line) is shown for (square) and 9.9 ml / min (circle) (broken line).

At present, the flow rate accuracy required for HPLC is 1% or more, and especially GPC (gel
A value of 0.1% is required for permeation chromatography). Conventionally, in order to obtain a good reproducibility of the holding time, the column part has been kept at a constant temperature, and some effects have been obtained. However, as described above, since the delivery flow rate of the conventional pump is controlled only by the volumetric flow rate, even if the volumetric flow rate is constant due to changes in the solvent temperature due to room temperature changes, temperature rise in the chamber due to mechanical friction, etc., Mass flow rates vary greatly. As a result,
Even if the temperature of the column section is kept constant, the mass flow rate of the solvent flowing through the column changes, and it becomes impossible to keep the retention time of the sample components constant.

Therefore, an object of the present invention is to improve the above points and provide a fluid pump which keeps a mass flow rate constant by keeping a fluid (solvent) temperature and a Cheber temperature constant.

Means for Solving the Problems In order to achieve the above-mentioned object, a fluid pump according to the present invention comprises, in a head, a chamber that communicates with an inflow passage that allows only inflow and an outflow passage that allows only outflow. A fluid pump for sucking and discharging a fluid by reciprocating a piston in the chamber is provided with means for holding the fluid flowing into the pump and the pump chamber at a constant temperature.

The means for maintaining the constant temperature preferably comprises a heat balancing coil for passing a fluid, an aluminum block connected to the head, and a means such as a circulation constant temperature bath for keeping the temperature of the aluminum block constant.

Embodiment An embodiment of the present invention will be described in detail below with reference to FIG.

FIG. 2 is a diagram schematically showing the structure of a fluid pump according to the present invention. In the figure, 3 is a head of a pump, and an inlet member 7 for attaching a suction pipe 6 to the head and a discharge pipe 8 are provided in the head 3. An outlet member 9 to be attached to is provided.

Although the internal structure of the head 3 is well known, it is not shown in the figure, but in brief, the head 3 has an inflow passage communicating with the suction pipe 6 and the discharge pipe 8 through the chamber and the inlet member 7 and the outlet member 9. , Outflow channels are provided respectively, and the chamber is open on one side (right side in the figure). Since the inflow passage is provided with a check valve that allows only inflow and the outflow passage has a check valve that allows only outflow, the fluid flows only in one direction. A piston is inserted through a liquid-tight seal in the chamber, and as the piston is reciprocated in the left-right direction in the figure by the piston drive device 10, fluid is sequentially sucked into the chamber and discharged therefrom.

Although a constant volumetric flow rate can be discharged per unit time by the fluid pump as described above, the mass flow rate changes with the temperature change of the fluid and the chamber as described above, so in the present invention, the temperature of the fluid flowing into the pump and the temperature of the chamber are constant. The mass flow rate is kept constant by providing a means for holding it.

A preferred embodiment of the above means for keeping the temperature constant will now be described. In FIG. 2, reference numeral 1 is a bottle containing a fluid, and an organic solvent such as methyl alcohol is used as the fluid when applied to chromatography. The solvent is guided from the bottle 1 through the suction pipe 6 to the head 3, and as shown in the drawing, the suction pipe 6 has a heat balance coil 2 in the middle thereof. Since the ambient temperature surrounding the thermal equilibrium coil 2 is kept constant by the aluminum block 4 described later, the solvent is kept at a constant temperature while passing through the thermal equilibrium coil 2 and is not affected by the change in ambient temperature.

Further, in the present invention, the head 3 of the fluid pump is connected to the aluminum block 4 so as to be able to conduct heat, and the temperature of the aluminum block 4 is adjusted by the heat medium sent from the circulation constant temperature bath 5. Therefore, the chamber in the head 3 is maintained at a constant temperature and is not affected by temperature changes due to mechanical friction or the like. Further, as described above, the aluminum block 4 also plays a role of keeping the ambient temperature including the heat balance coil 2 at a constant value.

In the illustrated embodiment, the temperature is controlled by using the circulation constant temperature bath, but the method of temperature control is not limited to this.
Similar effects can be obtained by other methods such as using a Peltier element.

As described above, according to the present invention, the inflow fluid (solvent)
Since the fluid pump that keeps the mass flow rate constant at all times can be obtained by keeping the chamber temperature and chamber temperature constant, the retention time of the sample components can be changed by the change of ambient temperature and chamber temperature if this is applied to chromatography. It can be prevented and exerts a great effect especially in GPC, etc., where high flow rate precision is required.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the effect of temperature change on mass flow rate, and FIG. 2 is a schematic configuration diagram of a fluid pump according to the present invention. 1 ... Fluid (solvent) bottle, 2 ... Thermal equilibrium coil, 3 ...
… Head, 4… Aluminum block, 5… Circulating constant temperature bath,
6 ... Suction pipe, 8 ... Discharge pipe, 10 ... Piston drive device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Kurosu 529-2967 Ishikawa-cho, Hachioji City, JASCO Corp. (56) References (JP, B1)

Claims (1)

(57) [Claims] 1. A fluid pump for sucking and discharging a fluid by providing a head with a chamber communicating with an inflow passage for allowing only an inflow and an outflow passage for allowing only an outflow, and reciprocally moving a piston in the chamber. A solvent bottle in which the fluid sucked by the fluid pump is stored, and a substantially spiral pipe that connects the solvent bottle and the inflow passage of the fluid pump and can supply the fluid in the solvent bottle to the inflow passage of the fluid pump. A heat balance coil; a metal block connected to the head of the fluid pump so as to be able to conduct heat; and a constant temperature unit capable of keeping the temperature of the heat balance coil and the metal block constant. Fluid pump with temperature controller that keeps the mass flow rate constant.