JPH01206260A - Distribution apparatus - Google Patents

Abstract

PURPOSE:To reduce the effect of temp. change on a distribution amount, by correcting the moving quantity of a plunger when a liquid is sucked corresponding to the temp. of the body part of a distribution tip. CONSTITUTION:A detection means 15a for detecting the temp. T1 of air is provided in the vicinity of a place where the sucking operation of a liquid is performed and a detection means 15b for detecting the temp. T2 of a body part 3 is provided to the body part 3 and the outputs of both means are sent to a controller 11 and the moving quantity (x) of a plunger 5 is calculated on the basis of the temps. T1, T2 according to a formula x=x0/[1-(T2-T1)/T1] (wherein x0 is the moving quantity of the plunger before correction). The plunger 5 is raised by predetermined quantity on the basis of this value by a plunger driving mechanism 6 and a liquid 8 is sucked in a distribution tip 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dispensing device used in automatic chemical analyzers and the like to quantify a liquid.

[Conventional technology]

As a dispensing device used in an automatic chemical analyzer, there is a device (Japanese Unexamined Patent Publication No. 106341/1983) that aspirates liquid by moving a plunger and heightens the needle.

FIG. 3 is a diagram showing a conventional dispensing device using a plunger;
Body part 3 located above the tip part 2; Atmospheric communication hole 4 passing through the tip part 2 and the body part 3. A plunger 5 that moves within the atmosphere communication hole 4. The plunger drive mechanism 6 includes a pulse motor 6a, a coupling 6b, a ball screw 6c, a plunger holding member 6d, a plunger vertical moving part 6e, and a bearing member 6f, a motor 7a, a vertical moving part 7b, and a receiving member 7c, and the tip part A vertical movement mechanism 7 for vertically moving the portion from 2 to the plunger drive mechanism 6, a container transport mechanism 10 for transporting the tip 1, a container 9 containing a liquid 8 (moves perpendicular to the plane of the paper), a plunger drive mechanism 6, Vertical movement mechanism 7
and a controller 11 that controls the operation of the transport mechanism 10,
A dispensing tip pushing member 12 and a tip removing member 14 that move around the outside of the body 3 in conjunction with the plunger drive mechanism 6. It consists of a holding member 13.

This dispensing device transfers liquid to another container as follows. The container 9 is positioned below the dispensing tip 1 by the container transport mechanism 10, and the dispensing tip 1 is moved by the vertical movement mechanism 7.
After lowering the plunger 5 until it is immersed in the liquid 8, the plunger drive mechanism 6 raises the plunger 5 by a predetermined amount to absorb the liquid 8 into the dispensing tip 1, and then the vertical moving mechanism 7 lowers the dispensing tip 1. is raised, another container 9 to which the liquid 8 is to be transferred is positioned below the dispensing tip 1 by the container transport mechanism 10, the dispensing tip 1 is lowered by the vertical movement mechanism 7, and the dispensing tip 1 is lowered by the vertical movement mechanism 7. 1 into the container 9,
The plunger drive mechanism 6 lowers the plunger 5 by a predetermined amount to discharge the liquid 8.

The amount of plunger movement during this discharge is set a certain amount larger than the amount of plunger movement during suction to prevent liquid from remaining inside the dispensing tip 1. A discard hole (not shown) for discarding the dispensing device 1 is transported to the lower part of the dispensing device, and the plunger drive mechanism 6 is driven here to push the tip removing member 14 downward through the dispensing tip pushing member 12. Remove the dispensing tip 1.

[Problem to be solved by the invention]

Next, the results of investigating the change in the amount of liquid sucked when the dispensing mechanism continues to dispense one volume are shown.
In FIG. 4, the horizontal axis shows the number of dispensing operations when dispensing continuously, and the vertical axis shows the measurement results of the dispensed amount and the degree of temperature rise in the body. In this manner, as the number of times of dispensing increases, the amount of liquid sucked in the operation of moving the plunger 5 upward to suck the liquid decreases. Furthermore, as the dispensing operation continues, the temperature of the body increases. This is the pulse motor 6a
This is due to the heat generated in the air and conducted through the holding member 13 and the frictional heat generated when the plunger 5 moves inside the atmosphere communication hole 4.

Next, we will discuss the relationship between this decrease in the amount of suction liquid and the temperature increase in the body of the dispensing device. If the product of the plunger cross-sectional area and the amount of plunger movement when sucking liquid is V, the plunger 5 rises and moves from the bottom of the atmosphere communication hole 4 to the atmosphere communication hole 4.
The air volume sucked into is also V. (Note that a small amount of air leaks from the base of the dispensing tip 1, but this leakage amount is
Since the ratio is small and constant at about 1%, it will be ignored from now on. ) The air sucked into the atmosphere communication hole 4 exchanges heat with the body, so its temperature T rises. that time.

The heat capacity of the body of the dispensing device is sufficiently large compared to the heat capacity of air on the μQ order, and the heat transfer from the body is also sufficiently large, so the temperature of the air sucked into the atmosphere communication hole 4 instantly becomes almost the same as that of the body. will have the same value.

Therefore, the temperature of the body measured in FIG. 4 can be regarded as the temperature of the air after it has been sucked into the atmosphere communication hole 4. Since air at atmospheric pressure and room temperature level can be regarded as approximately an ideal gas, the relational expression PV = RT (R: gas constant) and since the pressure P of air does not change before and after suction, the volume of suctioned air is will change in proportion to the rate of change in temperature before and after suction. Therefore, if the decrease in the dispensed amount shown in Fig. 4 is due to thermal expansion of air, then
The ambient temperature before suction is 'rzK, and the temperature at the tip is T.
x K , the volume of the sucked air is T before suction
2/T is doubled, and this air volume expansion v×(T
2-Tt)/Tl should appear as a decrease in liquid suction. In FIG. 5, when this predicted value (broken line) was compared with the experimental value (solid line), the two agreed well. From the above results, the cause of the dispensing amount being less than that of the atmospheric communication hole 4
In this experiment, which can be concluded to be due to thermal expansion of the air sucked in, the maximum temperature increase in the body was around 10°C, and the amount of decrease in the amount dispensed was around 3%. In conventional devices, the temperature of the body changes depending on the history of the dispensing operation, so there is a problem in that the dispensed amount fluctuates for the reasons stated above.

An object of the present invention is to solve the above-mentioned problem that the dispensed amount fluctuates due to temperature changes in the body, and to provide means for improving dispensing accuracy.

[Means to solve the problem]

The above object is achieved by providing a temperature detection means for detecting the temperature of the body and the temperature of the surrounding air, and employing a control method that corrects the amount of movement of the plunger when sucking liquid according to the temperature.

[Effect]

The operation of the dispensing device according to the present invention will be explained. Before aspirating the liquid, first check the ambient air temperature T1 and the body temperature T for the dispensing device.
2, and determine the amount of plunger movement X when sucking the liquid according to the temperature.

Let xO be the value obtained by dividing the target dispensing amount by the plunger cross-sectional area (this corresponds to the plunger movement amount before correction).

is calculated to find the plunger movement amount X that corrects the temperature change in the body. Next, a dispensing operation is performed based on the calculated value.

In the above-described operation, the influence of temperature changes in the body on the amount dispensed can be reduced, so variations in the amount dispensed can be reduced and accuracy can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to a partial diagram of a dispensing device shown in FIG. 1 and an operation flowchart shown in FIG. In this embodiment, an air temperature T1 detection means 15a is provided near the place where the liquid suction operation is performed, and a body temperature T2 detection means 15 is provided in the body 3.
b, and these outputs are sent to the controller 11. Next, based on the air temperature T1 and the body temperature T2, the plunger movement amount X during liquid suction is determined as follows.

The value obtained by dividing the target dispensing amount by the plunger cross-sectional area is xo
(This corresponds to the amount of plunger movement before correction).

Next, a pulse count corresponding to the plunger movement amount X is determined, and a dispensing operation is performed based on this value. That is, after the container 9 is positioned below the dispensing tip 1 by the container transport mechanism 10 and lowered by the vertical movement mechanism 7 until the dispensing tip 1 is immersed in the liquid 8, the plunger 5 is moved by the plunger drive mechanism 6. is raised by a predetermined amount to aspirate the liquid 8 into the dispensing tip 1. Next, the dispensing tip 1 is raised by the vertical movement mechanism 7, and the liquid 8 is transferred to another container 9 by the container transport mechanism 10. is positioned below the dispensing tip 1, the dispensing tip 1 is lowered by the vertical movement mechanism 7, and the dispensing tip 1 is inserted into the container 9. After that, the plunger 5 is moved into place by the plunger drive mechanism 6. The liquid 8 is discharged in a fixed amount. Plunger movement during this discharge'#J
The amount is set at a constant sensitivity to the amount of plunger movement during suction.

To prevent liquid from remaining inside the dispensing tip 1. Next, the container transport mechanism 10 transports the dispensing tip 1 through a discard hole (not shown) below the dispensing device, where the plunger drive mechanism 6 is driven to push out the dispensing tip 1 through the dispensing tip push-out member 12. Push the tip removal member 14 downward to remove the dispensing tip 1.

In this embodiment, a method of strictly determining the temperature based on the air temperature Tt and the body temperature T2 has been shown, but when the difference between the body temperature T2 and the air temperature 71't is small and the air temperature Tl does not vary greatly.

x= (1+a(Tz Tt))xo a; It is also possible to obtain the plunger movement amount X using a simpler relational expression with m coefficients.

〔Effect of the invention〕

As explained above, in the dispensing device according to the present invention, it is possible to reduce the dispersion in the dispensing amount due to temperature changes in the body, and it is possible to improve the dispensing accuracy.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view of a dispensing device according to the present invention, FIG. 2 is an operation flowchart thereof, FIG. 3 is a partial sectional view and side view showing the configuration of a conventional dispensing device, and FIG. FIG. 5 is a correlation diagram between the amount of dispensed amount and the body temperature with respect to the number of times of dispensing in the dispensing device. FIG. 5 is a correlation diagram between the amount of decrease in the dispensed amount and the body temperature. 1...Dispensing tip, 4...Atmospheric communication hole, 5...
Plunger, 6... Plunger drive mechanism, 7... Vertical movement mechanism, 8... Liquid, 9... Container, 10...
Conveying mechanism, 11...Controller, 13...Holding member, 15a...Air No. 1 Port No. 4 Fig. 8: @I number, 5 5L degree charcoal of the mouth body part

Claims (1)

[Claims] 1. An atmosphere communication hole, a body section that includes a plunger that moves within the atmosphere communication hole, a tip section that is connected under the body section and sucks and discharges liquid, a plunger drive mechanism that moves the plunger, the tip section, and the body section. In the dispensing device, the dispensing device includes a moving mechanism that moves the position of the plunger drive mechanism, a container transport mechanism, and a controller that controls the operation of all of the drive mechanisms described above. A dispensing device comprising means for correcting a plunger movement amount when sucking a liquid according to the temperature.