JP2003254983A - Level detection apparatus and automatic analyzer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow precise detection of a liquid level, and enable even liquid level detection for a trace sample. <P>SOLUTION: The apparatus comprises a liquid level approach control means 6 for causing an air nozzle 2 to discharge air at least before the air nozzle 2 reaches a liquid level 1 and for relatively moving the air nozzle 2 with respect to the liquid level 1, a reference value determination means 7 for detecting an inner pressure of the air nozzle 2 by means of a pressure sensor 5 before the air nozzle 2 reaches the liquid level and for determining a pressure reference value based on the detected value by the pressure sensor 5, a liquid level discrimination means 8 for comparing the pressure value of the pressure sensor 5 with the pressure reference value determined by the reference value determination means 7 so as to determine that the air nozzle 2 has reached the liquid level 1 provided that the pressure value of the pressure sensor 5 exceeded the pressure reference value, and a stop control means 9 for stopping the air discharge from the air nozzle 2 so as to stop the relative movement of the air nozzle 2 with respect to the liquid level 1 under the conditions where it is determined by means of the liquid level discrimination means 8 that the air nozzle 2 has reached the liquid level 1. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device for detecting a liquid level, and more particularly to a liquid level detecting device for detecting a liquid level based on a pressure change using an air nozzle and the liquid level detecting device using the same. Regarding improvement of automatic analyzer.

[0002]

2. Description of the Related Art Generally, in an automatic analyzer for quantifying a substance in a sample such as serum, the sampling amount of the sample and the dispensing amount of the reagent are determined when sampling the sample or dispensing the reagent by suction. In the above, it is usual to detect the liquid level of a sample such as a sample or a reagent, and use the detection information to perform the sample sampling operation and the reagent aspirating / dispensing operation. Conventionally, as a liquid level detection device used in this type of automatic analyzer, for example, a pump and a pipette connected to the pump are provided, and when a sample such as a sample or a reagent is dispensed by suction and discharge operations of the pump, A method to detect the liquid level from the pressure change of the flow system detected by the pressure sensor by providing a pressure sensor for connecting the pump and the pipette to detect the pressure of the flow system, lowering the pipette while operating the pump Has already been proposed (for example, Japanese Patent Laid-Open No. 2-243).
960 publication). For example, in a mode in which a positive pressure is supplied to the pipette, when the pipette reaches the liquid surface, the internal pressure in the pipette rises, so it is possible to detect the liquid surface based on this pressure change.

[0003]

However, in the liquid level detecting device of this type, the pressure reference value of the pressure sensor is set to a constant value in advance, and the pressure reference value of the pressure sensor is exceeded. A method of determining that the pipette has reached the liquid surface is adopted. However, a pressure sensor (such as a piezoresistive pressure sensor) has a temperature dependency, for example, and there is a concern that the sensor output may drift depending on the temperature. In a mode in which the disposable tip is attached, there is a possibility of pressure fluctuation due to dimensional variation of the tip diameter of the nozzle tip, air leak, etc. Therefore, it is necessary to secure a large margin in setting the pressure reference value of the pressure sensor. I don't get it. In addition, as the margin, it is necessary to consider other factors such as power supply voltage fluctuation factors and temperature fluctuation factors of individual components (for example, semi-fixed variable resistors).

At this time, since the margin of the pressure reference value is large, the pipette reaches the liquid surface due to the elasticity of the air until the liquid level is detected (until the pressure reference value is reached). It takes some time. Therefore, there is a delay in the timing of stopping the descending operation of the pipette, and the tip of the pipette is deeply immersed in the liquid. In such a state, if a large amount of sample adheres to the outer peripheral surface of the tip of the pipette, the adhering sample may drop, which may adversely affect the accuracy of the sample dispensing amount. In some cases, the tip of the pipette may collide with the bottom of the sample container, making it impossible to perform suction and dispensing operations by the pipette. In addition, liquid level accuracy is required even when the sample has two layers and only the top liquid is sucked.

The present invention has been made in order to solve the above technical problems, and is capable of accurately detecting the liquid level and also capable of detecting the liquid level of a small amount of sample. And an automatic analyzer using the same.

[0006]

According to the present invention, as shown in FIG. 1, a liquid surface 1 is disposed so as to face a liquid surface 1 to be detected.
An air nozzle 2 capable of ejecting air that moves relative to
An air supply device 3 for supplying a predetermined pressure of air into the air nozzle 2, an air pipe 4 connecting the air nozzle 2 and the air supply device 3 in communication with each other, and a pressure sensor 5 for detecting the internal pressure of the air nozzle 2. In the liquid level detection device, at least before the air nozzle 2 reaches the liquid level 1, air is ejected from the air nozzle 2 and the liquid level approach control means 6 that moves the air nozzle 2 relative to the liquid level 1; Before the liquid reaches the liquid surface 1, the internal pressure of the air nozzle 2 is detected by the pressure sensor 5, and the reference value determining means 7 for determining the pressure reference value based on the detection value of the pressure sensor 5, and the reference value determining means. The pressure reference value determined in 7 is compared with the pressure value of the pressure sensor 5, and the air nozzle 2 has reached the liquid level 1 under the condition that the pressure value of the pressure sensor 5 exceeds the pressure reference value. thing Under the condition that the liquid level determining means 8 for determining and the liquid level determining means 8 determine that the air nozzle 2 has reached the liquid level 1, the air discharge from the air nozzle 2 is stopped, and the liquid level 1 And a stop control means 9 for stopping the relative movement of the air nozzle 2 with respect to.

In the present invention, the air nozzle 2 is not limited to the mode in which the air nozzle 2 moves with respect to the liquid surface 1 as long as it can move relative to the liquid surface 1, and the air nozzle 2 is fixed and the liquid surface 1 It also includes a mode of moving. here,
When applied to a moving type of the air nozzle 2, the present invention, as shown in FIG. 1, includes a nozzle driving device 10 for moving the air nozzle 2 up and down in the liquid level detecting device, in which at least the air nozzle 2 is a liquid. Liquid level approach control means 6 for discharging air from the air nozzle 2 before reaching the surface 1 and lowering the air nozzle 2 with respect to the liquid level, and internal pressure of the air nozzle 2 before the air nozzle 2 reaches the liquid level 1. Reference value determining means 7 for detecting the pressure sensor 5 and determining a pressure reference value based on the detected value of the pressure sensor 5, and the pressure reference value and the pressure sensor 5 determined by the reference value determining means 7. Liquid level determining means 8 for determining that the air nozzle 2 has reached the liquid level 1 under the condition that the pressure value of the pressure sensor 5 exceeds the pressure reference value, and this liquid level. The discriminating means 8 Under the condition that it is determined that the nozzle 2 has reached the liquid surface 1, the stop control means 9 for stopping the air discharge from the air nozzle 2 and stopping the descending operation of the air nozzle 2 may be provided. .

In such a technical means, the air nozzle 2 may be appropriately selected as long as it has a nozzle structure capable of ejecting air. For example, as in the method of detecting the liquid level based on the change in capacitance, the material There is no restriction. Further, the air nozzle 2 is not limited to a mode in which the air nozzle 2 is a single component as a whole, and may have a structure in which, for example, the tip portion is detachable. In particular, if the tip portion has a detachable structure, even if the liquid adheres to the tip outer peripheral surface of the air nozzle 2 when the air nozzle 2 reaches the liquid surface 1, the influence of the adhered liquid can be avoided. It is possible.
Further, the type of the pressure sensor 5 may be appropriately selected, but from the viewpoint of being suitable for minute pressure detection,
It is preferable to use a piezoresistive pressure sensor that is inexpensive and highly sensitive. Since this piezoresistive pressure sensor has a temperature characteristic itself, it has a high temperature dependency. However, in the present invention, since the pressure reference value is determined based on the output of this pressure sensor 5, the pressure reference value is The temperature characteristic of the sensor 5 is considered in the process of determining the pressure reference value. Regarding the position where the pressure sensor 5 is arranged, the air nozzle 2
It suffices to be able to detect the internal pressure of the air pipe 4, and the inside of the air pipe 4 may be appropriately selected.

Further, with respect to the liquid level approach control means 6, the air discharge pressure of the air nozzle 2 may be appropriately selected, but it is preferable that the pressure is a minute pressure that suppresses fluctuations in the liquid level position to be detected as much as possible. Then, the air discharge operation of the air nozzle 2 may be started at an arbitrary position apart from the liquid surface 1 as an initial position as long as it is within a range in which the pressure reference value can be determined by the reference value determination means 7.

The reference value determining means 7 determines the pressure reference value in order to absorb all other influences such as the temperature dependency of the pressure sensor 5 and the manufacturing error of the air nozzle 2. Here, the “pressure reference value” means that the air nozzle 2 is at the liquid level 1
It is only necessary to be able to discriminate the pressure change when the pressure reaches a certain point, and from the viewpoint of improving the discrimination accuracy, a predetermined margin is added to the stable pressure value in the process of the air nozzle 2 approaching the liquid surface 1. Is selected. That is, when the air nozzle 2 reaches the liquid surface 1, the air nozzle 2 is blocked by the liquid surface 1, so that the internal pressure of the air nozzle 2 rapidly rises, but in the previous stage, there is a region where the internal pressure of the air nozzle 2 is stable. Since it continues, the pressure reference value may be selected based on the pressure value and the margin in this stable region. Note that the “margin” referred to here only needs to take noise margin into consideration, and it is not necessary to consider the margin corresponding to the temperature dependency of the pressure sensor 5 or the manufacturing error of the air nozzle 2, so the margin itself is small. Can be set to a value.

Further, the liquid level discriminating means 8 checks whether the pressure value of the pressure sensor 5 exceeds a predetermined pressure reference value, for example, and sends out a liquid level discriminating signal under such a condition. You can select it. Then, by stopping the relative movement of the air nozzle 2 by the stop control means 9 based on the liquid level determination signal from the liquid level determination means 8, the immersion amount of the tip of the air nozzle 2 on the liquid level can be reduced, and the air nozzle 2 It is possible to accurately detect the liquid surface position at the tip position of the. Here, the stop control means 9 stops the air discharge operation to the air nozzle 2 when the liquid level 1 is detected, but this suppresses the fluctuation of the liquid level 1 due to the air discharge pressure.

Further, the present invention is not limited to the liquid level detection device, but also an automatic analysis device using the same. In this case, the present invention, as shown in FIG. 1, has a container 11 in which a sample or a reagent is contained, and in an automatic analyzer for automatically analyzing a sample, the liquid 12 contained in the container 11 is used.
The liquid level detection device described above may be used as the liquid level detection device for detecting the liquid level 1. According to this aspect,
Since the immersion amount at the tip of the air nozzle 2 can be reduced, the liquid level can be detected even for a small amount of sample. At this time, the movable air nozzle 2 is preferably used as the air nozzle 2 from the viewpoint of simplifying the device configuration. Of course, the fixed type air nozzle 2 can be used, but in this case, for example, a mechanism for moving the container 11 itself to a predetermined position may be added.

Further, in the automatic analyzer, the air nozzle 2 may be constructed as an independent functional component, but when the air nozzle 2 is used in the automatic analyzer, a preferable mode of the air nozzle 2 is to suck or suck the liquid 12 in the container 11. The air nozzle 2 is used as a suction pipette for dispensing.
It is preferable that the suction pipette and the suction pipette are commonly used in terms of simplification of the device configuration.

As a prior art similar to the liquid level detection device of the present invention, there is, for example, one disclosed in Japanese Patent Laid-Open No. 2001-304938. This is a descending step of descending the nozzle toward the liquid surface while sucking or discharging air at the tip of the nozzle by the pump, and suction or discharge of the pump when the internal pressure of the pipe connected to the nozzle changes and It includes a detection step of stopping the descending of the nozzle, and a determination step of determining that the tip of the nozzle comes into contact with the liquid surface when the internal pressure of the pipe continues for a predetermined time or longer within an allowable variation range. In this type of prior art, when the internal pressure of the pipe changes, the suction or discharge of the pump is stopped and the lowering of the nozzle is stopped, and then the internal pressure of the pipe continues within the allowable change amount range. It is checked whether or not it is done, and it is judged that the tip of the nozzle comes into contact with the liquid surface only under the condition that these are satisfied. According to this type, by repeating a series of processes such as a change in the internal pressure of the pipe, a suction or discharge operation of the pump, a stop of the descending operation of the nozzle, and an internal pressure continuation check of the pipe,
Since it determines whether or not the tip of the nozzle has come into contact with the liquid surface, not only the liquid surface detection processing time increases, but also the suction operation may cause the sample to be sucked during the internal pressure continuation check. In addition, in the case of the discharging operation, it is not preferable in that air is sent into the sample to be stirred.

On the other hand, according to the present invention, the internal pressure of the air nozzle 2 is detected before the air nozzle 2 reaches the liquid surface 1, and the pressure reference value is determined based on the internal pressure. The feature point is that the liquid level is discriminated under the condition that the value is exceeded. Therefore, the present invention can be performed without stopping the air discharging operation of the air nozzle 2 and the relative movement operation of the air nozzle 2 with respect to the liquid surface 1 until the liquid surface is detected. Not only is it possible to shorten the detection processing time of, but also by considering the noise margin when setting the pressure reference value,
The influence of noise can be eliminated and the liquid surface detection accuracy can be improved. As described above, the present invention employs a liquid level detection method which is completely different from the above-mentioned prior art, and is irrelevant to the above-mentioned prior art.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. FIG. 2 shows an embodiment of an automatic analyzer to which the present invention is applied. In the figure, the automatic analyzer according to the present embodiment is configured for immunological analysis using the latex agglutination reaction method, and sample sampling for sampling a plurality of samples (for example, serum in this example) respectively The device 15 and a sample for dispensing a predetermined reagent (for example, a latex reagent in this example) to the sampled sample, stirring them to react the sample with the reagent, and optically measuring the reaction result And a reaction measuring device 20.

In the present embodiment, the sample sampling device 15 includes a disk-shaped sample table 16 in which a required number of sample cups (sample cups) not shown and dilution cups not shown are held in concentric loops. , And a sample pipetting mechanism 17 for sampling a sample (serum in this example) (sample suction operation and sample dispensing operation). Here, the sample table 16 is for intermittently transferring a sample cup or a dilution cup containing a sample to be inspected or a diluted sample to a predetermined sample suction stage. On the other hand, the sample pipetting mechanism 17 has a sample pipette 18 that can move up and down and rotate freely, and aspirates a required amount of the sample in the sample cup, or if necessary, divides the sample and the diluent into the dilution cup. The sample is poured or a sampled sample is dispensed into a cuvette described later.

The sample reaction measuring device 20 is provided with a reaction table 21 in which a required number of cuvettes (reaction cells) (not shown) are held in a loop at predetermined pitch intervals, and is provided coaxially with the reaction table 21. A reagent table 22 holding a reagent bottle containing a predetermined reagent (latex reagent in this example) and a reagent pipetting mechanism 23 (specifically 23a for sucking the reagent in the reagent bottle and dispensing it into a cuvette). , 23b) and an optical measuring device (not shown) for optically measuring the reaction between the sample and the reagent at a predetermined inspection stage. In this example, the reaction table 21
The cuvette is intermittently transferred in a fixed direction by stepwise rotation, while the reagent table 22 is rotationally driven independently of the reaction table 21. Further, in this example, the reagent pipetting mechanism 2
3 (23a, 23b) are provided, for example, two in consideration of workability when dispensing a plurality of reagents, and each is provided with a reagent pipette 24 for aspirating and dispensing the reagents.

In FIG. 2, reference numeral 27 is a reaction table 21.
A cuvette supply / disposal device that supplies a new cuvette into the cuvette and discards the cuvette that has been inspected, 31 is a liquid crystal display that displays the inspection result, 32 is an operation panel that instructs the inspection menu, and 33 is the inspection result A printer for outputting 34 is a recording medium drive used when storing data such as inspection results in a recording medium such as a flexible disk.

Particularly, in the present embodiment, the pipette 40
The pipette control system (particularly the liquid level detection device) for the sample pipette 18 or the reagent pipette 24 (see FIG. 3) is characterized. That is, the pipette control system according to the present embodiment, as shown in FIG.
A pipette moving mechanism 41 (sample pipetting mechanism 17 or reagent pipetting mechanism 23 for vertically moving and rotating the sample)
a and 23b), a suction / dispensing mechanism 42 that causes the pipette 40 to perform suction or dispensing operation, and the pipette 40.
Of the pressure sensor 43 for detecting the internal pressure of the pipe, a predetermined control signal to the pipette moving mechanism 41 and the suction / dispense mechanism 42, and a detection device for fetching the detection output of the pressure sensor 43. Three
It has 0 and. Then, in the present embodiment, the pipette control system includes a container 4 such as a sample cup or a reagent bottle.
By determining that the pipette 40 has reached the liquid surface of the sample (specimen, reagent, etc.) 45 contained in 4, the liquid level detecting device also functions as a liquid level detecting device.

Here, FIG. 4 shows a specific example of the structure of the liquid level detection device. In the figure, the pipette moving mechanism 41 is
The pipette 40 (in this example, an aspect in which a disposable detachable nozzle tip is attached to the tip is used) is provided with a vertical movement mechanism 50 that can be moved up and down. The vertical movement mechanism 50 is provided with a support member 51 at the base end portion of the pipette 40, a rack 52 is attached to the support member 51, and the rack is meshed with a worm gear 53 having an axis extending in the vertical direction to drive the rack vertically. The worm gear 53 is rotationally driven by a motor (stepping motor in this example) 54, and the vertical movement amount of the pipette 40 is regulated by the rotation direction of the worm gear 53 and the number of rotations thereof. In addition, the suction and dispensing mechanism 42
Has a syringe pump 61 for air suction or discharge,
The syringe pump 61 and the pipette 40 are connected to each other through a piping tube 62, and the piston 61a of the syringe pump 61 is moved by an air drive motor (stepping motor in this example) 63, so that air is discharged to the pipette 40. The operation or the air suction operation is performed.

Further, in this embodiment, the piping tube 6 is used.
A sensor mounting portion 62a is provided in the middle of 2, and the pressure sensor 43 is mounted on the sensor mounting portion 62a. In the present embodiment, as the pressure sensor 43,
For example, a piezoresistive pressure sensor is used, and this pressure sensor 43 has a diaphragm 7 that is displaced by the internal pressure of the piping tube 62, as shown in FIGS.
1, and four piezoresistive elements 72 (specifically, R1 to R4) are symmetrically attached to the diaphragm 71. The piezoresistive element 72 is shown in FIG.
As shown in (b), the diaphragm 71 has a characteristic that the longitudinal strain σa and the lateral strain σb are received according to the displacement of the diaphragm 71, and the resistance changes with these strains. The output circuit from the pressure sensor 43 forms a bridge circuit 73 with the four piezoresistive elements 72 (R1 to R4) as shown in, for example, FIG. By supplying a constant current with the current source 74, the voltage Vo across the bridge circuit 73 is taken out.

The output of the pressure sensor 43 is the control device 3.
It is taken into 0. The control device 30 takes, for example, an amplification amplifier 81 that amplifies the output of the pressure sensor 43, the output of the amplification amplifier 81, and calculates a comparator voltage that is a pressure reference value, and also the vertical drive motor 54 and the air drive motor 63. A controller 82 for sending a drive control signal (drive start signal, drive stop signal and speed control signal) to the output of the amplifier 81 and a comparator voltage calculated by the controller 82,
It is provided with a comparator 83 that outputs a liquid level determination signal under the condition that the output of the amplification amplifier 81 exceeds the comparator voltage, and executes the sample / reagent suction / dispensing processing sequence as shown in FIGS. 6 and 7. To do.

Next, the automatic analyzer according to the present embodiment,
In particular, the operation of the liquid level detection device will be described. In the present embodiment, when performing the aspiration / dispensing process of the sample or reagent, the control device 30 first detects the liquid level of the sample (sample or reagent) 45 in the container 44, as shown in FIG. The liquid level detection processing step is performed, then the sample suction processing step is performed, and then the sample dispensing processing step is performed.

Hereinafter, each processing step will be described in order. First,
The liquid level detection processing step will be described with reference to FIG. 7. now,
When the aspiration / dispensing process of the sample or the reagent is started by operating a switch (not shown) in the automatic analyzer, the control device 30 causes the pipette moving mechanism 41 (see FIG. 3) as shown in FIG. After initializing the pipette 40 to the initial position A determined in advance (see
Is driven to lower the pipette 40 toward the liquid surface of the sample 45, and the syringe pump 61 is driven at a predetermined timing to eject air from the pipette 40. Here, the ejection start timing of the air may be appropriately selected before the pipette 40 reaches the liquid surface of the sample 45, but in this example, the maximum accommodation position of the sample 45 in the container 44 (previously The timing immediately before the settable position) is selected. The internal pressure of the pipette 40 at this time, that is, the pressure change of the pressure sensor 43 is shown in FIG.

After this, as shown in FIG. 8B, the tip of the pipette 40 approaches the liquid surface of the sample 45, but the internal pressure of the pipette 40 causes the tip of the pipette 40 to reach the liquid surface. It shows a stable pressure value up to. Therefore, in the present embodiment, as shown in FIG. 7, the controller 82 checks the output of the pressure sensor 43 at a predetermined sampling period for a predetermined time immediately after the air discharge by the syringe pump 61 is started, and the pressure is checked. The pressure change of the sensor 43 is sampled. Then, as a result of, for example, averaging a plurality of sampling values of the pressure sensor 43, the discharge pressure value is determined under the condition that the difference between the average value and the maximum value or the minimum value of the sampling values is within a predetermined range.

After that, the controller 82, based on the judged discharge pressure value, is a comparator 83 which is a pressure reference value.
The comparator value (comparator voltage) of is determined. In this case, as the comparator value, a value in which a margin is added to the discharge pressure value is selected. Here, in addition to the noise margin, when considering the temperature dependency of the pressure sensor 43, the manufacturing error of the nozzle tip (not shown) of the pipette 40, and the margin for all factors such as air leak, it corresponds to the discharge pressure value. With respect to the voltage value (for example, around 2.5V), the marginal voltage is, for example, 1.0 to
Although 2.0 V is required, in this example, only the noise margin is considered as the margin voltage, and for example, 0.2 to
0.5V is selected.

Thereafter, as shown in FIG. 8C, when the pipette 40 further descends while ejecting air, finally,
The tip of the pipette 40 reaches the liquid surface of the sample 45. Then, as shown in FIG. 9, since the tip of the pipette 40 is completely blocked by the liquid surface, the internal pressure of the pipette 40 rapidly rises, and the comparator 83 outputs the output of the pressure sensor 43 to the comparator value ( When the pressure reference value) is exceeded, a liquid level determination signal is sent to the controller 82. During this period, the controller 82 checks the output of the comparator 83 (whether the output of the pressure sensor 43 exceeds the comparator value (pressure reference value)), as shown in FIG.
It is determined that the pipette 40 has reached the liquid surface under the condition that the liquid surface determination signal is received from 3, and as a result, the liquid surface position is recognized. After that, the controller 82 sends a drive stop signal to the vertical drive motor 54 and the air drive motor 63 in synchronization with the liquid level determination signal, the drive of each drive motor 54, 63 is stopped, and the lowering operation of the pipette 40. And the air discharge operation is stopped.

In such a liquid level determination process, as shown in FIG.
As shown in, the comparator value (pressure reference value) is selected to be a value obtained by adding the margin voltage ΔVm to the voltage value corresponding to the discharge pressure value, so that even after the pipette 40 reaches the liquid surface. Although the pipette 40 continues the descending operation, the amount of immersion in the sample 45 after the pipette 40 reaches the liquid surface is extremely small because the voltage ΔVm itself for the margin is small. Therefore, the tip of the pipette 40 accurately stops at a position substantially corresponding to the liquid surface of the sample 45. Therefore, even if the amount of the sample 45 in the container 44 is extremely small, there is little concern that the tip of the pipette 40 reaches the bottom of the container 44, and the liquid surface of the sample 45 can be accurately detected. Is.

When a piezoresistive pressure sensor, for example, is used as the pressure sensor 43, the pressure value of the pressure sensor 43 changes depending on the temperature, or the noise of the pipette 40, because the temperature dependency is generally high. Although the pressure value of the pressure sensor 43 changes due to chip manufacturing errors, air leaks, and fluctuations in the power supply voltage, etc., these pressure fluctuation factors are absorbed at the stage of measuring the discharge pressure value, so the pressure reference value is determined. , It is not necessary to consider these variables as a margin.

After that, the control device 30 executes the sample suction processing sequence as shown in FIG. 8 (d). In this sample suction processing sequence, the pipette 40 is further lowered by δ from the liquid level detection position by the vertical movement mechanism 50, and thereafter, air is sucked by the syringe pump 61 for a predetermined time, whereby the pipette 40 is sucked into the pipette 40. Sample 45
Is sucked by a predetermined amount, and in this state, the vertical movement mechanism 5
The pipette 40 is returned to the initial position A by 0. In such a sample suction treatment process, the amount of immersion of the tip of the pipette 40 into the sample 45 does not vary greatly. Therefore, the sample 45 attached to the outer peripheral surface of the tip of the pipette 40 excessively adheres to the sample 45. There is no concern that the suction volume will change significantly.

In the liquid level detection process and the sample suction process (FIGS. 8 (a) to 8 (d)), the process is performed by the sample suction stage ST1. When the process is completed, the control device 30 causes the pipette moving mechanism 41 to move the pipette 40, as shown in FIG.
After shifting to the initial position B of the sample dispensing stage ST2, the sample dispensing processing sequence is executed. At this time, the sample in the pipette 40 is still held by suction. In this sample dispensing processing sequence, the vertical movement mechanism 50 is used while holding the sample 45 in the pipette 40 by suction.
The pipette 40 to another reaction vessel, the cuvette 4
6, the sample 45 is dispensed into the cuvette 46 by ejecting air from the syringe pump 61 after returning the pipette 40 to the initial position B by the vertical movement mechanism 50. Let In such a sample dispensing process, since the sample 45 does not excessively adhere to the outer peripheral surface of the tip of the pipette 40, when the sample 45 in the pipette 40 is discharged during the air discharge operation by the syringe pump 61, The sample adhering to the outer peripheral surface of the tip of 40 does not mix in the cuvette 46. Therefore, the dispensing amount of the sample 45 into the cuvette 46 becomes extremely accurate.

[0033]

As described above, according to the liquid level detecting device of the present invention, the internal pressure of the air nozzle is detected before the air nozzle reaches the liquid level, and the pressure reference value is determined based on this. After that, since the method of discriminating the liquid surface under the condition that the internal pressure of the air nozzle exceeds the pressure reference value is adopted, compared with the mode in which the pressure reference value is selected in advance, as the pressure reference value, for example, for detecting the internal pressure of the air nozzle. It is no longer necessary to consider the temperature dependence of the pressure sensor and the manufacturing error of the air nozzle, and the margin of the pressure reference value can be minimized to that extent. Can be detected. Therefore, the amount of immersion of the air nozzle into the liquid surface can be minimized, and the liquid surface detection accuracy can be improved.

Further, according to the automatic analyzer using this type of liquid level detecting device, it becomes possible to accurately detect the liquid level even if the amount of the sample such as the sample or the reagent is very small. Therefore, the sampling amount of the sample, the dispensing amount of the reagent, and the like can be controlled more accurately, and the analysis accuracy of the automatic analyzer can be further improved by that amount.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of a liquid level detection device according to the present invention and an automatic analysis device using the same.

FIG. 2 is an explanatory diagram showing an embodiment of an automatic analyzer to which the present invention is applied.

FIG. 3 is an explanatory diagram showing a pipette control system of the automatic analyzer used in the present embodiment.

FIG. 4 is an explanatory diagram showing details of the liquid surface detection device according to the present embodiment.

5A is a front explanatory view of a pressure sensor, FIG. 5B is a plan explanatory view thereof, and FIG. 5C is an explanatory view showing an output extraction principle of the pressure sensor.

FIG. 6 is a flowchart showing a process of aspirating / dispensing a sample or a reagent.

FIG. 7 is a flowchart showing a liquid level detection processing process of FIG.

8A to 8E are explanatory views schematically showing a process of aspirating / dispensing a sample or a reagent.

FIG. 9 is a graph showing changes in internal pressure of the pipette.

[Explanation of symbols]

1 ... Liquid level, 2 ... Air nozzle, 3 ... Air supply device, 4 ... Air piping, 5 ... Pressure sensor, 6 ... Liquid level approach control means, 7 ...
Reference value determination means, 8 ... Liquid level determination means, 9 ... Stop control means, 10 ... Nozzle drive device, 11 ... Container, 12 ... Liquid

Claims (5)

[Claims] 1. An air nozzle capable of ejecting air, which is arranged to face a liquid surface to be detected and moves relative to the liquid surface, an air supply device for supplying air of a predetermined pressure into the air nozzle, and the air nozzle. In a liquid level detection device equipped with an air pipe that communicates with an air supply device and a pressure sensor that detects the internal pressure of the air nozzle, at least before the air nozzle reaches the liquid level, air is discharged from the air nozzle to A liquid level approach control means that moves the air nozzle relative to the surface, and a pressure sensor detects the internal pressure of the air nozzle before the air nozzle reaches the liquid level, and the pressure reference value is determined based on the detected value of this pressure sensor. The pressure reference value determined by this reference value determination means and the pressure value of the pressure sensor are compared, and the pressure value of the pressure sensor determines the pressure reference value. Under the condition that the air nozzle has reached the liquid level under the exceeded condition, and the condition that the air nozzle has reached the liquid level by this liquid level determination unit, A liquid level detecting device, comprising: stop control means for stopping air discharge from the air nozzle and stopping relative movement of the air nozzle with respect to the liquid surface. 2. The liquid level detection device according to claim 1, further comprising a nozzle drive device for moving the air nozzle up and down, wherein air is discharged from the air nozzle at least before the air nozzle reaches the liquid level. A liquid level approach control means for lowering the air nozzle relative to the surface, and the pressure sensor detects the internal pressure of the air nozzle before the air nozzle reaches the liquid level, and the pressure reference value is determined based on the detection value of this pressure sensor. The reference value determining means and the pressure reference value determined by this reference value determining means are compared with the pressure value of the pressure sensor, and the air nozzle is set to the liquid level under the condition that the pressure value of the pressure sensor exceeds the pressure reference value. Liquid level determining means for determining that the air nozzle has reached the liquid level, and the air from the air nozzle under the condition that the liquid level determining means determines that the air nozzle has reached the liquid level. The output is stopped, the liquid level detecting apparatus characterized by comprising a stop control means for stopping the downward movement of the air nozzle. 3. The liquid level detecting device according to claim 1 or 2, wherein the pressure sensor is a piezoresistive pressure sensor. 4. A container having a sample or a reagent contained therein,
An automatic analyzer for automatically analyzing a sample in the container, wherein the liquid level detecting device according to claim 2 is used as a liquid level detecting device for detecting a liquid level of a liquid contained in the container. apparatus. 5. The automatic analyzer according to claim 4, wherein the air nozzle is also used as a suction / dispensing pipette for sucking or dispensing the liquid in the container.