JP2005140514A - Dropping liquid amount measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for measuring the quantity of dropped liquid, capable of constituting the apparatus at a low price and precisely measuring the liquid quantity of droplets dropped from a nozzle, at low cost. <P>SOLUTION: A light sensor 3 is provided with both a light source 31 and a light-receiving part 32 for receiving beam light B emitted from the light source 31, and the light sensor 3 is provided for a location, at which the droplets L discharged from the nozzle 11 interrupt the beam light B. An interrupting time, during which the beam light B is interrupted, is measured by a measuring part 4, and the liquid quantity of the droplets is computed by an operation part 5, on the basis of the result of measurement of the interrupting time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus and method for measuring the amount of liquid droplets dropped from a nozzle.

For example, in order to obtain high measurement accuracy in a titration apparatus, it is important to measure the amount of dropped liquid with high accuracy.
As an example of the conventional method, there is a method of knowing the amount of dripping by controlling the amount of dripping from a nozzle using a pulse motor type pump.
In addition, a method of measuring the amount of liquid dropped by measuring the weight change of a titration tank that receives liquid droplets dropped from a nozzle with an electronic balance or the like is also known (for example, Patent Document 1 below).
JP-A-8-128990

However, the method using a pulse motor-type pump has a problem that it is necessary to manufacture each component with high accuracy in order to achieve high accuracy, resulting in an increase in cost. In addition, since all of the liquid in the pump head is not discharged at the time of dripping, the liquid always stays in the pump head and the liquid is liable to deteriorate, which may reduce the measurement accuracy. Since consumption of the check valve or the like leads to a decrease in accuracy, there is a problem that it is necessary to replace parts regularly and costly.
On the other hand, the method of measuring the weight change of the titration tank requires a precision machine such as an electronic balance, and the price of the apparatus is high, and facilities and operations for preventing weight changes other than the weight change of the titration tank due to dripping In addition, there is a problem that the apparatus becomes large and costs are increased.

  The present invention has been made in view of the above circumstances, and it is difficult for the liquid to deteriorate in the apparatus, and the apparatus can be configured at a low price. The amount of liquid dropped from the nozzle can be reduced at a low cost. It is an object of the present invention to provide a dripping liquid amount measuring apparatus and a dripping liquid amount measuring method capable of measuring with high accuracy.

  In order to solve the above-described problems, a dripping liquid amount measuring apparatus according to the present invention is a device that measures the liquid amount of a liquid droplet dripped from a nozzle, and receives a light source and a light beam emitted from the light source. An optical sensor provided with a section, provided at a position where a droplet ejected from the nozzle blocks the beam light, a measurement unit that measures a blocking time when the beam light is blocked, and a measurement of the blocking time An arithmetic unit that calculates the liquid amount of the droplet based on the result is provided.

  The droplet light discharged from the nozzle can be configured to block the beam light while falling.

  It is preferable that a shielding member for shielding disturbance is provided at least in a region from the nozzle tip to the beam light.

  Further, the dripping liquid amount measuring method of the present invention is a method for measuring the liquid amount of a liquid droplet dripped from a nozzle, and the liquid droplet discharged from the nozzle uses a light beam from the light source of the optical sensor to the light receiving unit. The blocking time for blocking is measured, and the liquid amount of the droplet is calculated based on the measurement result of the blocking time.

  As the blocking time, it is possible to measure the time for blocking the beam light while the droplet discharged from the nozzle is falling.

In the present invention, in the optical sensor, while the light beam emitted from the light source is received by the light receiving unit, the blocking time of the beam light when the droplet is dropped so as to block the beam light is measured. By doing so, it is possible to accurately measure the amount of liquid droplets.
According to the present invention, it is possible to configure an apparatus at a low price, and it is possible to suppress an increase in cost due to wear of parts.

Embodiments according to the present invention will be described below.
FIG. 1 is a schematic configuration diagram showing an embodiment of a dripping liquid amount measuring apparatus according to the present invention. In this embodiment, an example in which the apparatus of the present invention is applied to a titration apparatus will be described.
The dropping liquid amount measuring device of the present embodiment includes a dropping device 1, a titration tank 2 provided below the nozzle 11 of the dropping device 1, and an optical sensor 3 provided between the nozzle 11 and the titration tank 2. And a measurement unit 4 connected to the optical sensor and a calculation unit 5 connected to the measurement unit 4.

The dropping device 1 is configured to discharge liquid from the nozzle 11 in the form of drops. In the present embodiment, a tank 13 for storing a liquid communicates with a nozzle 11 having a discharge port at the tip via a valve 12. Then, by opening and closing the valve 12 by a driving means (not shown), a predetermined amount of liquid is intermittently sent from the tank 13 to the nozzle 11, and accordingly, the droplet L drops from the discharge port at the tip of the nozzle 11. It is configured to be. In order for the liquid ejected from the nozzle 11 to be droplets, the ejection amount per unit time may be reduced.
For example, an electromagnetic valve can be suitably used as the valve 12.
The tank 13 may be installed at a position higher than the nozzle 11 and the valve 12 so that when the valve 12 is opened, the liquid in the tank 13 is fed to the nozzle 12 by gravity. Or you may use the pressurization-type tank provided with the pressurization means which pressurizes the inside of the tank 13, and liquid-feeds, In this case, the freedom degree of the installation position of the tank 13 is high. As a medium for pressurizing the inside of the tank 13, a medium that does not react with the liquid in the tank 13 is preferable, and an inert gas such as air or nitrogen gas can be appropriately used.

  In the present embodiment, the liquid to be titrated is contained in the titration tank 2, and a stirrer for stirring the liquid in the titration tank 2 is provided, and in the titration indicated by an arbitrary instruction method. A sensor for detecting the end point is provided.

The optical sensor 3 includes a light source 31 that continuously emits beam-like light (referred to as beam light B in this specification) and a light receiving unit 32 that receives the beam B from the light source 31. The light receiving unit 32 is configured to detect whether or not the light beam B emitted from the light source 31 is blocked, and to output an electrical signal opposed thereto to the measuring unit 4. In addition, the light receiving unit 32 is configured to output a signal indicating a blocked state when at least a part of the light beam B is blocked.
The optical sensor 3 can use an existing device. In general, the beam diameter of the beam B is preferably equal to or smaller than the diameter of the droplet L. The beam diameter of the beam B used in the present invention is preferably about 0.5 to 2 mm. The smaller the beam diameter, the better the accuracy of measuring the amount of dripping liquid.
In the present embodiment, the nozzle 11 and the optical sensor 3 are arranged such that the optical path of the light beam B emitted from the light source 31 and the passage path through which the droplet L ejected from the nozzle 11 passes are dropped. In other words, the droplets L ejected from the nozzle 11 are fixed at positions where the light beam B is blocked during dropping.

The measuring unit 4 is configured to receive a signal from the light receiving unit 32 and measure a blocking time while the beam B is blocked.
The computing unit 5 is configured to calculate the liquid amount of the droplet L based on the measurement result of the blocking time measured by the measuring unit 4.
The measurement unit 4 and the calculation unit 5 can be configured using an existing calculation device.

Next, a method for measuring the liquid amount of the droplet L using the dropped liquid amount measuring device of the present embodiment will be described.
When driving means (not shown) is driven to open and close the valve 12 and the droplet L is ejected from the tip of the nozzle 11, the droplet L is ejected from the nozzle 11. The droplet L ejected from the nozzle 11 falls off the light beam B from the light source 31 of the optical sensor 3 to the light receiving unit 32. When the beam light B is blocked by the droplet L, a signal indicating the blocking state is output from the light receiving unit 32 to the measuring unit 4, and the measuring unit 4 measures the blocking time based on the signal. Then, the calculation unit 5 calculates the liquid amount of the droplet L based on the measurement result of the blocking time measured by the measurement unit 4.

Here, in the present embodiment, a method for calculating the liquid amount of the droplet L from the blocking time of the beam B will be theoretically described.
When an object of mass m naturally falls, the force F acting on the object is F = mg (g is gravitational acceleration).
When this is integrated, the drop speed v when the time t has passed since the start of the fall is
v = gt (Expression 1) From this, it can be seen that the drop speed v is constant regardless of the mass m of the object if t is constant.
Therefore, as illustrated in FIG. 2, if the distance h from the lower end of the droplet L to the beam light B in a state immediately before the droplet L discharged from the nozzle 11 starts to fall is constant, the droplet L The time t from when the droplet begins to drop until the beam light B is blocked is constant, and the drop velocity v when the droplet L blocks the beam light B is constant.

That is, since the speed at which the droplet L blocks the beam light B is constant regardless of the size of the droplet L, the blocking time is proportional to the size of the droplet L. For example, assuming that the droplet L is a true sphere, its diameter is 2r, the blocking time is T, and the velocity at which the droplet L blocks the beam B is v ′, T = (2r) / v ′. Become. On the other hand, since the volume V of the droplet L is expressed by V = (4πr ³ ) / 3, the relationship between T and V is T = (2 / v ′) [3 / (4π)] ^1/3 · (V) ^1/3 (Expression 2) From this, it can be seen that by measuring the blocking time T, the volume V of the droplet L can be uniquely obtained.
Note that v ′ in Equation 2 can be obtained as follows.
That is, when v = gt (Equation 1) is integrated, the drop distance from the start of the drop until the time t elapses, that is, the distance h from the lower end of the droplet L to the beam B is
h = (gt ² ) / 2 = (vt) / 2 (Expression 3) The value of h can be approximated from the nozzle 11 at a distance H ₁ in beam B, it is easily obtained because can be corrected by using the measurement result of the radius r of the droplet L. Then, if the value of h is known, the fall time t from when the drop starts until the beam light B is blocked can be found from the above equation 3, and the velocity v ′ when the droplet L blocks the beam light B can be determined. Understand.
Therefore, the volume V of the droplet L is calculated from the measured value of the v ′ and the blocking time T obtained in this way according to the above equation 2.

As illustrated in FIG. 2, the distance H ₁ from the nozzle 11 to the beam light B is such that the beam light B is lower than the lower end of the droplet L just before the droplet L discharged from the nozzle 11 starts to fall. What is necessary is just to set so that it may be located below. However, as the distance H ₁ is large, the drop time t from the start of dropping until blocking the light beam B becomes larger, the velocity v 'increases when the droplet L interrupts the light beam B, the It is necessary to set H ₁ so that the speed v ′ at the time of blocking does not exceed the limit value of the resolution at which the light receiver 32 can recognize the light blocking state.

According to this embodiment, by measuring the time during which the falling droplet L blocks the beam light B, the liquid amount of the droplet L can be measured easily and accurately.
Furthermore, if the liquid amount of each droplet L obtained in this way is integrated, the sum of a plurality of droplets, that is, the dropped liquid amount can be obtained.
Moreover, the dripping liquid amount measuring apparatus of this embodiment can be easily comprised by the calculating apparatus containing the dripping apparatus 1, the titration tank 2, the optical sensor 3, the measurement part 4, and the calculating part 5. FIG. Since the apparatus having such a configuration can be configured using an existing apparatus without using parts that require high accuracy, a low-cost apparatus can be realized. Further, since the beam light is used as the measurement medium, there is no concern about the deterioration of accuracy due to wear of parts, and the cost can be suppressed.
Further, since the liquid in the tank 13 is sent to the nozzle 11 by opening and closing the valve 12, there is no place where the liquid stays in the dropping device 1, and therefore the liquid is hardly deteriorated in the device.

In the above embodiment, as shown in FIGS. 3 and 4, the shielding member 6 (7) may be provided so as to surround an area from the tip of the nozzle 11 to the beam B. When the droplet L ejected from the nozzle 11 is subjected to disturbance such as wind before the light beam B is blocked, the shielding member 6 (7) reduces the measurement accuracy of the blocking time or the droplet L However, it is provided to prevent such inconvenience because it falls without blocking the light beam B and becomes unmeasurable.
In the example of FIG. 3, the tip of the nozzle 11 and the region below the nozzle 11 are surrounded by a cylindrical shielding member 6 made of a material that transmits the beam B, and the light source of the optical sensor 3 is outside the shielding member 6. 31 and the light receiver 32 are provided facing each other.
In the example of FIG. 4, the tip portion of the nozzle 11 and the region below the nozzle 11 are surrounded by a cylindrical shielding member 6 made of a material that transmits the beam B, and the light source 31 of the optical sensor 3 and the shielding member 6 A light receiver 32 is embedded oppositely.
The shielding member 6 (7) may be any member as long as it can suppress disturbance that may adversely affect the measurement of the beam B blocking time by the droplet L, and its size and shape are not limited to these examples. Can be designed as appropriate.

  In the above embodiment, the droplet L ejected from the nozzle 11 is configured to block the beam light B while falling, but the droplet L ejected from the nozzle 11 is irradiated with the beam light during growth. Even if it is configured so as to block, the volume of the droplet L can be obtained based on the same principle.

(Simulation example 1)
A simulation for measuring the liquid amount of the droplet L was performed using the dripping liquid amount measuring apparatus and method of the first embodiment.
When the distance h from the lower end of the droplet L just before dropping to the beam light B is 2 mm, the drop time t from when the droplet L starts to fall to the beam light B is 0.002 = (9.8 / 2) t ^{2 From} this, t = 0.020 seconds is obtained.
If this value of t = 0.020 seconds is used, the velocity v ′ = 9.8 × 0.020 = 0.20 m / sec when the droplet L blocks the light beam B can be obtained from Equation 1 above.
Substituting the value of v ′ obtained in this way into Equation 2 above,
T = (2 / 0.20) [3 / (4π)] ^1/3 · (V) ^1/3
That is, T = 6.2 × (V) ^1/3 is obtained.
Therefore, the volume V of the droplet L can be obtained using the measured value of the blocking time T of the light beam B.

For example, when the volume of the droplet L when falling is 50 μL,
The blocking time T of the light beam B = 6.2 × (50 × 10 ⁻⁹ ) ^1/3 = 22.8 ms (milliseconds).
When the volume of the droplet L when falling is 40 μL,
The blocking time T of the light beam B = 6.2 × (40 × 10 ⁻⁹ ) ^1/3 = 21.2 ms (milliseconds).
Similarly, the relationship between the volume of the dropped droplet L and the blocking time when blocking the light beam B provided at the position of h = 2 mm while the droplet L was dropped was obtained by calculation. The result is shown in FIG.
In FIG. 5, the horizontal axis indicates the volume V (unit: μL) of the dropped droplet L, and the vertical axis indicates the blocking time T (unit: millisecond) of the beam light B by the droplet L.
From this figure, it can be seen that V and T are well correlated, and the volume V of the droplet L can be obtained using the measured value of the blocking time T of the beam B.

It is a schematic block diagram which shows the dripping liquid quantity measuring device concerning this invention. It is a figure for demonstrating the positional relationship of the nozzle and beam light in the 1st Embodiment of this invention. It is a schematic sectional drawing which shows the example of the shielding member concerning this invention. It is a schematic sectional drawing which shows the example of the shielding member concerning this invention. It is a graph which shows the result of the example of simulation concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dripping apparatus 2 Titration tank 3 Optical sensor 4 Measuring part 5 Calculation part 6,7 Shielding member 11 Nozzle 31 Light source 32 Light receiver B Beam light L Droplet

Claims (5)

An apparatus for measuring the amount of liquid droplets dropped from a nozzle,
An optical sensor including a light source and a light receiving unit that receives the beam light emitted from the light source is provided at a position where a droplet discharged from the nozzle blocks the beam light,
An apparatus for measuring a dropped liquid amount, comprising: a measuring unit that measures a blocking time when the light beam is blocked; and a calculation unit that calculates a liquid amount of a droplet based on the measurement result of the blocking time.   The dripping liquid amount measuring device according to claim 1, wherein the droplet light discharged from the nozzle blocks the beam light while falling.   The dripping liquid amount measuring device according to claim 1, wherein a shielding member that shields disturbance is provided at least in a region from the tip of the nozzle to the beam light. A method for measuring the amount of liquid dropped from a nozzle,
The liquid droplets discharged from the nozzle measure the blocking time for blocking the beam light from the light source of the optical sensor to the light receiving unit, and calculate the liquid amount of the liquid droplets based on the measurement result of the blocking time A method for measuring the amount of dripping liquid. The dripping liquid amount measuring method according to claim 4, wherein as the blocking time, a time for blocking the beam light while the droplet discharged from the nozzle is falling is measured.

Images