JP3964946B2 - Dispensing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid level detection using ultrasonic waves in a sample suction device, particularly an automatic dispensing device.
[0002]
[Prior art]
The dispensing device is a device for sucking a sample from a sample container containing a sample (original specimen) and distributing the sucked sample to a plurality of containers. In such a dispensing apparatus, the suction and discharge of the sample is performed by a nozzle connected via an air tube to a dispensing pump that generates suction pressure and discharge pressure. 2. Description of the Related Art In recent years, it has become popular to install a nozzle tip made of a resin or the like on a metal nozzle base and make the nozzle partially disposable. In this specification, for the sake of convenience, an apparatus that performs only sample aspiration is also included in the concept of the dispensing apparatus.
[0003]
In order to increase the dispensing accuracy in the dispensing apparatus, it is necessary to accurately manage the liquid amount (aspirated amount) of the sample sucked by the nozzle and the liquid amount (discharge amount) of the sample discharged from the nozzle. Therefore, conventionally, it has been proposed to transmit light along the longitudinal direction of the nozzle and monitor the amount of liquid based on a change in the amount of transmitted light.
[0004]
[Problems to be solved by the invention]
However, in the conventional liquid amount monitoring using transmitted light, there is a problem that measurement is not possible or measurement accuracy is lowered when a nozzle having low transparency or transparency is used. In addition, even when the nozzle itself is transparent, when a colored sample is discharged, there is a problem that the liquid level cannot be clearly measured because the sample adheres to the inner surface of the nozzle even after discharge.
[0005]
In order to improve dispensing accuracy and improve dispensing reliability in dispensing devices, it is desirable to detect abnormal suction and liquid leakage. Therefore, conventionally, the internal pressure of the piping system connected to the nozzle is monitored, and abnormal suction and liquid leakage are determined based on abnormal fluctuations in internal pressure. However, these methods do not directly monitor the fluctuation of the liquid level in the nozzle itself.
[0006]
In addition, in JP-A-7-146168 and JP-A-6-341998, it is described that liquid level detection is performed using an ultrasonic wave propagation body provided with an ultrasonic transducer. It does not detect the liquid level in the nozzle.
[0007]
The present invention has been made in view of the above-described conventional problems, and an object thereof is to directly monitor the liquid level in the nozzle and measure the suction amount and the discharge amount with high accuracy.
[0008]
It is another object of the present invention to provide a dispensing device that can determine a suction amount, a discharge amount, a liquid leak, and a suction abnormality by using a liquid level detection by ultrasonic waves.
[0009]
Another object of the present invention is to provide a dispensing device that can achieve the focusing of ultrasonic waves for liquid level detection and the blocking of extraneous noise by utilizing a nozzle-like waveguide. .
[0010]
Furthermore, the objective of this invention is providing the dispensing apparatus which can detect the liquid level in a nozzle irrespective of coloring and non-coloring.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises a nozzle base and a nozzle tip attached to the nozzle base, and is provided in a hollow nozzle for sucking a sample, a nozzle transport mechanism for transporting the nozzle, and the nozzle base. An ultrasonic sensor that radiates ultrasonic waves from the base end side of the nozzle to the nozzle internal space and receives reflected waves, and a liquid of the sample sucked into the nozzle based on a received signal from the ultrasonic sensor A liquid level detecting means in the nozzle for detecting the surface, wherein the wave transmitting / receiving surface of the ultrasonic sensor faces the internal space of the nozzle, and ultrasonic waves are radiated from there to the nozzle tip side.
[0012]
According to the above configuration, the nozzle is provided with the ultrasonic sensor, and the ultrasonic wave is transmitted from the ultrasonic sensor to the nozzle internal space. The reflected wave reflected by the liquid level in the nozzle is received by the ultrasonic sensor. Therefore, if the received signal is monitored, the liquid level can be determined as an echo of a predetermined level or higher. In this case, the time from the time of transmission to the time of occurrence of the liquid level echo correlates with the liquid level of the sample in the nozzle.
[0013]
The nozzle itself functions as a sound wave path, and the transmitted ultrasonic wave is guided from the nozzle base end side to the tip end side without divergence. The same applies to the reflected wave, and the reflected wave returns to the inside of the nozzle and is received by the ultrasonic sensor without diverging. Further, the wall surface of the nozzle functions as an external noise shielding member. Therefore, according to the ultrasonic wave transmission / reception within the nozzle, the S / N ratio can be improved, and highly accurate liquid level detection can be realized.
[0014]
In a preferred aspect of the present invention, the liquid level height calculating means for calculating the height of the detected liquid level is provided. That is, the ultrasonic propagation distance from the ultrasonic sensor to the liquid surface can be calculated from the time until the liquid surface reflected wave is obtained from the time of transmission, and if the propagation distance is subtracted from the length inside the nozzle, the liquid surface from the nozzle tip Can be easily obtained. Of course, the reflected wave time until the reflected wave is generated is a function of the height of the liquid surface, and therefore the height of the liquid surface can be directly calculated from the reflected wave time by using a table or the like.
[0015]
In a preferred aspect of the present invention, the apparatus includes a suction amount calculating means for calculating a suction amount of the sample sucked into the nozzle based on the detected liquid level, and the amount of descending liquid level when the sample is discharged is included. And a discharge amount calculating means for calculating the discharge amount of the sample discharged from the nozzle based on the nozzle. That is, if the form inside the nozzle is known, the liquid amount (suction amount) can be calculated from the height of the liquid level, and the discharge amount can also be calculated from the amount of descent of the liquid level.
In a preferred aspect of the present invention, a liquid leakage determining means for determining liquid leakage based on the fluctuation of the liquid level in the sample holding state is included. That is, if a leak (air suction) occurs at any part of the piping system or at the fitting portion between the nozzle base and the nozzle tip, the liquid leaks and the liquid level of the sample sucked into the nozzle gradually decreases. Therefore, the liquid leakage is determined by detecting the temporal fluctuation of the liquid level.
[0016]
In a preferred aspect of the present invention, a suction abnormality determining means for determining a suction abnormality based on a change in liquid level during sample suction is included. Here, the suction abnormality determination means desirably determines the suction abnormality when the temporal fluctuation of the liquid level during the suction is out of the appropriate range.
[0017]
That is, if the nozzle tip opening is clogged during sample suction or the above-mentioned leak occurs, the fluctuation of the liquid level also becomes abnormal. Therefore, in order to improve dispensing reliability, abnormal suction is determined.
[0018]
As described above, according to the present invention, liquid level detection by ultrasonic waves can be effectively utilized in a series of dispensing steps of sample suction, sample holding, and sample discharge.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0020]
FIG. 1 shows a preferred embodiment of a dispensing apparatus according to the present invention, and FIG. 1 is an overall configuration diagram thereof. In this embodiment, the nozzle 10 that sucks and discharges the sample is composed of a metal nozzle base 12 and a nozzle tip 14 formed of a transparent resin or the like. A tip mounting portion 12A having a tapered outer surface is formed at the lower end of the nozzle base portion 12, and the upper end portion 14A of the nozzle tip 14 is detachably fitted into the tip mounting portion 12A. The nozzle tip 14 is used as a so-called disposable, and after dispensing one sample, the nozzle tip 14 is replaced prior to dispensing the next sample.
[0021]
The nozzle 10 has a hollow pipe shape as a whole, and has a waveguide structure from another viewpoint. A small ultrasonic sensor 18 incorporating an ultrasonic transducer is embedded in the upper end portion 12B of the nozzle base portion 12. The transmission / reception surface of the ultrasonic sensor 18 faces the internal space of the nozzle 10. That is, the transmission / reception surface of the ultrasonic sensor 18 faces the inner side of the nozzle tip located immediately below. The tip of the nozzle tip 14 is tapered to form a taper, and an opening 14B as a microhole is formed at the tip. The diameter of the opening 14B is, for example, 0.5 to 0.7 mm.
[0022]
A sample 22 as a suction target is placed in the container 20, and the container 20 is held vertically by a rack. FIG. 1 shows a state in which a predetermined amount of sample is sucked into the nozzle 10 and its liquid level is detected by ultrasonic measurement.
[0023]
The internal space of the nozzle base 12 is branched as shown in FIG. 1, and an air pump 28 is connected to the branch path 12 </ b> C via an air tube 26. The air pump 28 functions as a dispensing pump, and specifically includes a syringe 30 and a piston 32. Depending on the amount of movement of the piston 32 relative to the syringe 30, suction pressure or discharge pressure is generated. The pressure change is transmitted to the inside of the nozzle 10 through the air tube 26, and the sample is sucked and discharged. The pump 28 is mechanically driven by a pump drive mechanism 34. The nozzle 10 is held by a nozzle transport mechanism 36 so as to be movable up and down and horizontally. Specifically, the nozzle base 12 is held by the nozzle transport mechanism 36.
[0024]
In FIG. 1, the main control unit 38 is configured by a computer, for example, and includes a dispensing control unit 40 and a nozzle liquid level detection unit (hereinafter, liquid level detection unit) 42.
[0025]
The dispensing control unit 40 performs control for liquid level detection using ultrasonic waves, in addition to nozzle elevation control and pump drive control during suction and discharge. When a transmission trigger is given from the dispensing control unit 40 to the transmission unit 44, a transmission signal is supplied from the transmission unit 44 to the ultrasonic sensor 18, whereby an ultrasonic pulse is emitted from the ultrasonic sensor 18. The ultrasonic pulse propagates in the internal space (in the air) of the nozzle 10, and the reflected wave reflected by the liquid surface of the sample in the nozzle 10 is received by the ultrasonic sensor 18. The received signal is subjected to processing such as amplification, detection, and noise removal in the receiving unit 46 and then sent to the liquid level detecting unit 42 in the nozzle, where the liquid level in the nozzle 10 is detected based on the received signal. .
[0026]
The center frequency of the ultrasonic pulse radiated from the ultrasonic sensor 18 is set to any value between, for example, several tens of KHz to several Mhz, taking into account that the propagation medium is air and the internal form of the nozzle 10. Is done. The transmission repetition period of the ultrasonic pulse is set to a value larger than the time for the ultrasonic pulse to reciprocate the distance from the ultrasonic sensor 18 to the nozzle tip. It is desirable that the wave number constituting the ultrasonic pulse is appropriately set in consideration of distance resolution and signal intensity.
[0027]
In FIG. 1, the dispensing control unit 40 includes a liquid level calculation unit 50, a suction amount calculation unit 52, a discharge amount calculation unit 54, a liquid leakage determination unit 56, and a suction abnormality determination unit 58. Each configuration will be described in detail below.
[0028]
The liquid level calculation unit 50 calculates the height of the liquid level based on the liquid level detected by the in-nozzle liquid level detection unit 42. FIG. 2 schematically illustrates the received signal as a waveform. As shown in FIG. 2A, a liquid level echo 102 is generated at a position corresponding to the liquid level in the received signal. Therefore, if the liquid level echo 102 is discriminated by the predetermined threshold value 100, the time t1 from the time of transmission to the time of occurrence of the liquid level echo can be obtained. Then, by multiplying t1 by the velocity of the ultrasonic wave in the air, the distance h1 from the ultrasonic sensor 18 to the liquid surface in FIG. 3 can be calculated. Since the length of the nozzle tip 14 is known, and the distance h0 from the ultrasonic sensor 18 to the tip of the nozzle tip 14 is also known, the height h2 of the liquid level to be obtained can be easily obtained by subtracting h1 from h0. It can be calculated. The in-nozzle liquid level detection unit 42 shown in FIG. 1 performs discrimination of the liquid level echo 102 by the threshold value 100 and measurement of the time t1 as shown in FIG. Then, the liquid level height calculation unit 50 calculates the liquid level height h2 from time t1 as described above.
[0029]
When the liquid level height h2 is obtained in this way, the suction amount calculation unit 52 calculates the liquid amount of the sample 22 sucked into the nozzle 10. That is, since the internal form of the nozzle tip 14 is known, the suction amount can be calculated from the liquid level height h2. In this case, for example, a table for obtaining h2 and the suction amount directly from t1 may be used. Further, such a table may be switched and used depending on the type of the nozzle tip 14.
[0030]
The discharge amount calculation unit 54 shown in FIG. 1 calculates the discharge amount from the amount of descending liquid level. As shown in FIG. 2B, when the liquid level echo 104 is initially generated at time t1, and the liquid level echo 106 after the sample is discharged is generated at time t2, the liquid amount is changed at each time. Since the calculation can be performed as described above, the discharge amount U can be obtained from the difference in the liquid amount at each time as shown in FIG. When the inner diameter of the nozzle tip 14 is constant from t1 to t2, the discharge amount U may be obtained directly from the time difference t3 between t1 and t2, as shown in FIG.
[0031]
The liquid leak determination unit 56 shown in FIG. 1 determines a liquid leak caused by a leak that occurs in a piping system or the like by monitoring the amount of liquid in the nozzle in a sample holding state where suction or discharge is not performed. is there. Specifically, as shown in FIG. 5, it is determined that liquid leakage has occurred when the liquid level fluctuation ΔU occurs in the pump stop state.
[0032]
Note that such liquid leakage monitoring may be performed by, for example, storing the liquid volume immediately after sample suction, measuring the liquid volume again immediately before discharge, and generating an alarm when there is a difference in liquid volume. Good. Alternatively, the liquid level fluctuation can be confirmed also by comparing the time until the liquid level echo is generated without comparing the liquid levels.
[0033]
Next, the suction abnormality determination unit 58 shown in FIG. 1 will be described. The suction abnormality determining unit 58 determines suction abnormality by monitoring temporal fluctuations in the liquid level during suction. FIG. 7A shows a change in liquid level when a normal suction is performed as a graph 200. In the present embodiment, as shown in FIG. 7B, the suction abnormality determination unit 58 sets the determination curves 202U and 202L while being spaced apart from each other by a fixed interval above and below the normal graph 200. Abnormal suction is determined when the liquid level graph 204 deviates from the region surrounded by such two determination curves. FIG. 7B shows a state where a leak occurs in the piping system and the like, and the sample cannot be sucked with a sufficient suction pressure. As shown in the figure, the gradient of the graph 204 indicating the liquid level is smaller than the normal one.
[0034]
On the other hand, FIG. 7C shows a graph 206 when clogging occurs. That is, as shown in FIG. 6, when the tip opening of the nozzle tip 14 is blocked by the foreign matter 200 or the like floating in the sample 22, the liquid level of the sample does not rise even if the suction pressure is generated by the pump. The state is shown in FIG. 7C, and the graph 206 has deviated from the area surrounded by the curves 202U and 202L from the time when the occurrence occurred. Therefore, the suction abnormality determination unit 58 generates an alarm indicating a suction abnormality based on the pop-up of the graph from such a determination area.
[0035]
It should be noted that the determination region surrounded by the curves 202U and 202L shown in FIG. 7 is desirably set as appropriate in consideration of the required determination accuracy of suction abnormality, exclusion of erroneous determination, and the like. For example, it is possible to increase the width of the determination region as time elapses.
[0036]
Next, operation | movement of the dispensing apparatus of this embodiment is demonstrated using FIG.
[0037]
First, in a state where the nozzle 10 is positioned above the container 20 containing the sample 22, in S101, the nozzle 10 is pulled down by the nozzle transport mechanism 36, and in S102, the amount of insertion of the nozzle tip into the liquid surface The sample is aspirated while maintaining a constant value.
[0038]
In S103, the liquid level is detected based on the transmission / reception of the ultrasonic wave by the ultrasonic sensor 18 as described above. In this case, the suction amount calculation unit 52 calculates the suction amount, that is, the suction amount is constantly monitored. At the same time, the suction abnormality determination unit 58 constantly monitors the suction abnormality, and if a leak or clogging as shown in FIG. 7 occurs, an alarm is generated in S107.
[0039]
In S104, it is determined whether or not the monitored suction amount has reached the set value. If the suction amount has reached the set value, suction is stopped in S105, and the nozzle 10 is transported in S106. The mechanism 36 is pulled upward. In S108, the nozzles are conveyed in the horizontal direction as necessary. When the nozzle rises or moves, the liquid leakage determination unit 56 functions. In the example shown in FIG. 8, the liquid level fluctuation is constantly monitored. A liquid leak alarm has occurred. Of course, the liquid leakage may be determined by comparing the liquid amount immediately after suction with the liquid amount immediately before discharge.
[0040]
In S109, the nozzle 10 is pulled downward by the nozzle transport mechanism 36 toward the container to be discharged, and in S110, discharge is started. In S112, ultrasonic wave transmission / reception by the ultrasonic sensor 18 is executed again, and the height fluctuation of the liquid level is monitored. In this case, the discharge amount calculation unit 54 calculates the discharge amount. In S113, it is determined whether or not the calculated discharge amount has reached the set value. If the discharge amount has reached the set amount, the discharge is stopped in S114, and then the nozzle in S115. 10 is pulled upward by the nozzle transport mechanism 36. In S116, it is determined whether or not to continue the discharge of the sample to the next container, and in the case of continuing, each step from S108 is repeatedly executed.
[0041]
According to the above embodiment, various calculations and determinations can be realized by providing the ultrasonic sensor 18 in the nozzle 10, and high-precision dispensing can be achieved.
[0042]
【The invention's effect】
As described above, according to the present invention, the liquid level in the nozzle can be directly monitored, and the suction amount and the discharge amount can be calculated with high accuracy. Further, according to the present invention, it is possible to determine liquid leakage and suction abnormality in addition to the suction amount and the discharge amount by utilizing the liquid level detection by ultrasonic waves. Furthermore, according to the present invention, it is possible to simultaneously realize the focusing of ultrasonic waves for detecting the liquid level and the blocking of external noise by utilizing the unique form of the nozzle. Moreover, according to this invention, there exists an advantage that a liquid level detection can be performed also with respect to the colored nozzle.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a dispensing apparatus according to the present invention.
FIG. 2 is a waveform diagram showing a waveform of a received signal.
FIG. 3 is a diagram illustrating a calculation principle of a liquid amount.
FIG. 4 is a diagram illustrating a calculation principle of a discharge amount.
FIG. 5 is a diagram showing fluctuations in the liquid level when liquid leakage occurs.
FIG. 6 is a diagram showing a state where the nozzle tip opening is clogged with foreign matter. FIG. 7 is a diagram showing a determination range for determining suction abnormality.
FIG. 8 is a flowchart showing the operation of the dispensing apparatus according to the present invention.
[Explanation of symbols]
10 nozzles, 12 nozzle bases, 14 nozzle tips, 18 ultrasonic sensors 22 samples, 28 pumps, 34 pump drive mechanisms, 36 nozzle transport mechanisms, 38 main control units, 40 dispensing control units, 42 liquid level detection units in nozzles, 50 liquid level height calculation unit, 52 suction amount calculation unit, 54 discharge amount calculation unit, 56 liquid leakage determination unit, 58 suction abnormality determination unit.

Claims (7)

A hollow nozzle that is composed of a nozzle base and a nozzle tip attached to the nozzle base and sucks a sample;
A nozzle transport mechanism for transporting the nozzle;
An ultrasonic sensor that is provided at the nozzle base, emits ultrasonic waves from the base end side of the nozzles to the nozzle internal space, and receives reflected waves;
In-nozzle liquid level detection means for detecting the liquid level of the sample sucked into the nozzle based on the received signal from the ultrasonic sensor;
Including
2. A dispensing apparatus according to claim 1, wherein a transmission / reception surface of the ultrasonic sensor faces the inner space of the nozzle, and ultrasonic waves are radiated from there to the nozzle tip side. The apparatus of claim 1.
A dispensing apparatus comprising liquid level height calculating means for calculating a height from a nozzle tip to a liquid level based on the detected liquid level. The apparatus of claim 1.
2. A dispensing apparatus comprising: a suction amount calculating means for calculating a suction amount of a sample sucked into the nozzle based on the detected liquid level. The apparatus of claim 1.
A dispensing apparatus comprising discharge amount calculating means for calculating a discharge amount of a sample discharged from the nozzle based on a descending amount of a liquid level at the time of discharging a sample. The apparatus of claim 1.
A dispensing apparatus comprising: a liquid leakage determining means for determining a liquid leakage based on a fluctuation of a liquid level in a sample holding state. The apparatus of claim 1.
A dispensing apparatus comprising suction abnormality determining means for determining a suction abnormality based on a change in a liquid level during sample suction. The apparatus of claim 6.
Based on the detected liquid level, it has a liquid level height calculating means for calculating the height from the nozzle tip to the liquid level,
The dispensing apparatus according to claim 1, wherein the suction abnormality determining unit determines a suction abnormality when a temporal variation in height from a nozzle tip to a liquid level during suction is out of an appropriate range.

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