JP2013060850A - Liquid feed pump - Google Patents

Abstract

The present invention provides a liquid feed pump capable of easily detecting operation states such as bubble mixing, pressure feed pressure, dissolved gas amount, and liquid feed amount.
A pump chamber is connected to an outlet side buffer chamber via an outlet channel, and liquid is pumped from the outlet side buffer chamber. Then, a deforming portion that is deformed by the internal pressure of the pump chamber is provided, and pressure vibration generated in the pump chamber when the volume of the pump chamber is reduced is detected by a change in displacement of the deforming portion. This pressure vibration includes various information relating to the operation state of the liquid feed pump, such as bubble mixing, pressure feed pressure, dissolved gas amount, and liquid feed amount. Therefore, if the variation of the displacement of the deforming portion is detected, various information relating to the operation state of the liquid feeding pump can be easily detected.
[Selection] Figure 2

Description

  The present invention relates to a liquid feed pump that pumps a liquid.

  There is known a liquid feed pump that repeats an operation of increasing the volume of a pump chamber and sucking in a liquid and then reducing the volume of the pump chamber and pumping the liquid. Further, in a small liquid feed pump, a piezoelectric element that is small and capable of generating a large force is often used as an actuator for increasing or decreasing the volume of the pump chamber (Patent Document 1, etc.).

JP 2011-103930 A

  However, the liquid feed pump that increases or decreases the volume of the pump chamber has the following problems. First, when bubbles are mixed in the pump chamber, the bubbles are crushed and the liquid in the pump chamber cannot be pressurized even if the volume of the pump chamber is reduced, and the liquid cannot be fed. Also, if a gas such as air is dissolved in the liquid to be sent, the compressibility of the liquid will increase, so the pressure in the pump chamber will not increase sufficiently when the volume of the pump chamber is reduced, The pumping pressure of the liquid decreases. In order to avoid this, it is desirable to monitor the amount of air (or amount of gas) dissolved in the liquid, but it is not easy to measure the amount of dissolved air. In addition, when the usage is to connect the flow path of the liquid fed from the liquid feed pump to the suction side of the liquid feed pump to form a circulation flow path system, the liquid is fed by the liquid feed pump. Since the liquid flows through the sealed flow path, it is difficult to grasp the amount of liquid delivery unless a flow sensor or the like is separately provided.

  The present invention has been made to solve at least a part of the above-described problems of the prior art, and information on the operation state of the liquid feeding pump (for example, mixing of bubbles, pressure feeding pressure, dissolved gas amount, The purpose of the present invention is to provide a technique that can easily detect any one of the liquid feeding amount.

In order to solve at least a part of the problems described above, the liquid feeding pump of the present invention employs the following configuration. That is,
A liquid feed pump for feeding liquid in the pump chamber by changing the volume of the pump chamber,
An outlet channel connected to the pump chamber;
An outlet-side buffer chamber having a larger compliance than the pump chamber and constituting a resonance system with the pump chamber by being connected to the pump chamber via the outlet channel;
A deformation part deformed by an internal pressure of the pump chamber;
A displacement detection unit for detecting a change in displacement of the deformation unit;
A gist of the invention is that it includes an operation state detection unit that detects an operation state of the liquid feeding pump based on a change in displacement of the deformation unit.

  In the liquid feed pump of the present invention having such a configuration, when the volume of the pump chamber is increased, the liquid is sucked into the pump chamber from the inlet channel via the check valve. Thereafter, when the volume of the pump chamber is reduced, the liquid is pumped from the pump chamber to the outlet side buffer chamber via the outlet channel, and then the liquid is sent from the outlet side buffer chamber to the fluid channel. Here, the pump chamber and the outlet side buffer chamber are connected via an outlet channel, and constitute a resonance system. The resonance system here refers to a range in which, when the pressure changes (increase or decrease in pressure) inside the system, the pressure oscillation is generated over a period of time, triggered by the change in pressure. Say. In a system in which the pump chamber and the outlet side buffer chamber are connected via the outlet channel, the pressure fluctuation generated in any one of the pump chamber, the outlet side buffer chamber, and the outlet channel continues for a certain period thereafter. Thus, pressure oscillation is generated in the pump chamber, the outlet side buffer chamber, and the outlet channel. In this way, if the resonance system is configured by connecting the pump chamber and the outlet side buffer chamber via the outlet channel, the pressure vibration due to resonance is generated in the pump chamber after the volume of the pump chamber is reduced. And the deformed portion is deformed by this pressure vibration. Therefore, a change in the displacement of the deforming portion is detected to detect the operation state of the liquid feed pump. The deforming part may be any part that can be deformed by the internal pressure of the pump chamber. For example, a deformable part is provided as a deforming part on a part of the wall surface of the pump chamber. Alternatively, it can be deformed inward. Alternatively, instead of being directly deformed by the internal pressure of the pump chamber, a change in the internal pressure causes a liquid flow (for example, a liquid flow toward the pump chamber due to a decrease in the internal pressure of the pump chamber). It is also possible to provide a member that deforms as a deformed portion.

  As will be described in detail later, when a resonance system is configured by connecting the pump chamber and the outlet-side buffer chamber with an outlet flow path, the pressure vibration generated in the pump chamber due to resonance associated with the increase / decrease in the volume of the pump chamber This includes various information related to the operation state (for example, mixing of bubbles, pressure feeding pressure, amount of dissolved air, amount of liquid feeding, etc.). Therefore, if the variation of the displacement of the deforming portion caused by the pressure vibration of the pump chamber is detected, it is possible to easily detect information relating to the operation state of the liquid feeding pump.

  Moreover, in the liquid feeding pump of the present invention described above, the displacement of the deformable portion generates a binary signal based on a predetermined threshold value, and detects the operation state of the liquid feeding pump based on the binary signal. Also good.

  When the pressure vibration generated in the pump chamber due to resonance occurs, the displacement of the deformed portion varies, so that the binary signal becomes a signal having a plurality of pulses. The presence or absence of these pulses or the time interval between pulses also contains various information relating to the operating state of the liquid feed pump. Furthermore, if the displacement of the deformed portion is converted into a binary signal, the signal can be handled easily. For this reason, it becomes possible to easily detect various information relating to the operation state of the liquid feeding pump by converting the variation of the displacement of the deformed portion into a binary signal.

  Further, in the liquid delivery pump of the present invention described above, the presence or absence of bubbles mixed in the pump chamber may be detected based on the presence or absence of a binary signal pulse generated after the volume of the pump chamber is reduced. Here, the pulse of the binary signal may be a pulse in which the binary signal in the low state is in the Hi state for a short time, or conversely, the pulse in which the binary signal in the Hi state is in the Low state for a short time. There may be.

  When bubbles are not present in the pump chamber, pressure vibration is generated in the pump chamber after the volume of the pump chamber is reduced. However, when bubbles are present, pressure vibration is not generated in the pump chamber. Therefore, it is possible to easily detect the presence or absence of bubbles mixed in the pump chamber based on whether or not there is a pulse in the binary signal after reducing the volume of the pump chamber.

  Further, in the liquid feed pump of the present invention described above, the pressure (pressure feed pressure) for pumping liquid from the liquid feed pump based on the time from when the volume of the pump chamber is reduced until the pulse of the binary signal is detected. ) May be detected.

  Although the detailed mechanism will be described later, the time from when the volume of the pump chamber is reduced to when the pulse of the binary signal is detected is determined by the pressure of the liquid in the outlet side buffer chamber. The pressure of the liquid in the outlet side buffer chamber is a pressure for pumping the liquid. Therefore, if the pumping pressure of the liquid is detected based on the time from when the volume of the pump chamber is reduced until the binary signal pulse is detected, the pumping pressure can be easily detected. In addition, since it is sufficient to detect a binary signal due to fluctuations in the displacement of the deformed portion, for example, even when a liquid feed pump is incorporated in a circulation flow path system and the liquid flows in a closed flow path, the liquid pressure feed The pressure can be easily detected.

  In the liquid delivery pump of the present invention described above, the amount of dissolved gas in the liquid is detected based on the time interval of a plurality of pulses generated in the binary signal after the volume of the pump chamber is reduced. Also good.

  Although the detailed mechanism will be described later, the time interval of a plurality of pulses generated in the binary signal after reducing the volume of the pump chamber has a strong correlation with the dissolved amount of gas in the liquid. Therefore, if the time interval of a plurality of pulses generated after reducing the volume of the pump chamber is detected, the amount of dissolved gas in the liquid can be easily detected. In addition, since it is sufficient to detect a binary signal due to fluctuations in the displacement of the deformed portion, the amount of dissolved gas even when, for example, a liquid feed pump is incorporated in a circulation flow path system and liquid flows in a closed flow path Can be easily detected.

  In the liquid delivery pump of the present invention described above, the amount of liquid delivered per hour is detected based on the time interval of a plurality of pulses generated in the binary signal after the volume of the pump chamber is reduced. You may do it.

  Although the detailed mechanism will be described later, the time interval between a plurality of pulses generated in the binary signal after the volume of the pump chamber is reduced has a strong correlation with the amount of liquid delivered per time. Therefore, if the time interval of a plurality of pulses generated after reducing the volume of the pump chamber is detected, it is possible to easily detect the liquid feeding amount. In addition, since it is sufficient to detect a binary signal due to fluctuations in the displacement of the deformed portion, for example, even when a liquid feed pump is incorporated in a circulation flow path system and liquid flows in a sealed flow path, the liquid feed amount Can be easily detected.

  In addition, the above-described liquid feed pump of the present invention can efficiently feed a liquid, and can greatly reduce the loss of electric energy input to the piezoelectric element. For this reason, it is particularly excellent as a liquid feed pump incorporated into a circulation device or a liquid feed pump incorporated into a medical device.

In addition, the liquid feeding pump of this invention can also be grasped | ascertained in the following aspects. That is,
A liquid feed pump for feeding liquid in the pump chamber by changing the volume of the pump chamber,
An outlet channel connected to the pump chamber;
An outlet-side buffer chamber having a larger compliance than the pump chamber and constituting a resonance system with the pump chamber by being connected to the pump chamber via the outlet channel;
A deformation part deformed by an internal pressure of the pump chamber;
A displacement detector for detecting a change in displacement of the deformable portion after the volume of the pump chamber is reduced;
A gist of the invention is that it includes an operation state detection unit that detects an operation state of the liquid feeding pump based on a change in displacement of the deformation unit.

  When a resonance system is configured by connecting the pump chamber and the outlet side buffer chamber with an outlet channel, the pressure vibration generated in the pump chamber due to resonance after the volume reduction (or increase) of the pump chamber is the operating state of the liquid feed pump It includes various information related to (for example, mixing of bubbles, pumping pressure, dissolved air amount, and liquid feeding amount). Therefore, if the change in the displacement of the deformed portion caused by the pressure vibration after the volume reduction of the pump chamber is detected, it is possible to easily detect information relating to the operation state of the liquid feed pump.

It is explanatory drawing which showed the structure of the liquid feeding pump of a present Example. It is explanatory drawing which illustrated the fluctuation | variation of the displacement by a deformation | transformation part deform | transforming when a drive signal is applied to a piezoelectric element, and a binary signal. It is explanatory drawing which illustrated the displacement and binary signal of a deformation | transformation part obtained when a bubble exists in a pump chamber. It is a measurement result which shows the relationship between the time from the 1st pulse of a binary signal to the 2nd pulse, and the pressure in the outlet side buffer chamber. It is explanatory drawing which illustrated the circulation flow path system formed using the liquid feeding pump. It is explanatory drawing which showed the relationship between the amount of gas dissolved in the liquid obtained by measurement, and a natural vibration period. It is explanatory drawing which showed the relationship between the amount of gas dissolved in the liquid obtained by actual measurement, and the amount of liquid feeding. It is explanatory drawing which showed the relationship between the natural vibration period obtained by measurement, and the amount of liquid feeding. It is explanatory drawing which illustrated the structure of the liquid feeding pump of a modification.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Device configuration:
B. Bubble detection method:
C. Detection method of pumping pressure:
D. Detection method of gas dissolved amount and liquid feeding amount:
E. Variations:

A. Device configuration :
FIG. 1 is an explanatory diagram showing the configuration of the liquid feed pump 100 of this embodiment. In the liquid feed pump 100 of this embodiment, a part of the pump chamber 102 is formed of a diaphragm 104, a piezoelectric element 106 is housed in the case 108, and a check valve 110 is disposed above the pump chamber 102. An inlet side buffer chamber 112 is provided through the. The inlet side buffer chamber 112 is supplied with liquid from the inlet channel 114. The pump chamber 102 is connected to an outlet side buffer chamber 118 via an outlet channel 116, and a fluid channel 122 is connected to the outlet side buffer chamber 118. Furthermore, a control circuit 150 is connected to the piezoelectric element 106, and a drive signal can be applied from the control circuit 150 to the piezoelectric element 106.

  Also, a part of the pump chamber 102 is provided with a deformed portion 102d that is thinner than other portions, and when the internal pressure of the pump chamber 102 increases, the deformed portion 102d deforms outward. On the contrary, when the internal pressure is lowered, the deforming portion 102d is deformed inward. Further, a so-called reflective photocoupler 130 is provided outside the deformable portion 102d. In the photocoupler 130, the light emitting element and the light receiving element are incorporated in substantially the same direction. If the object is at an appropriate distance from the photocoupler 130, the light emitted from the light emitting element is the object. Reflected and detected by the light receiving element. In the present embodiment, in a state where the deforming portion 102d is not deformed (a state in which the internal pressure of the pump chamber 102 is atmospheric pressure), the light receiving element of the photocoupler 130 does not receive reflected light, but the deforming portion 102d is above a certain level. When deformed to the outside, the reflected light is received. Then, the photocoupler 130 outputs a binary signal (binary signal) indicating whether or not the light is received by the light receiving element toward the control circuit 150.

  In the present embodiment, a description will be given assuming that a binary signal is output by detecting the displacement of the deformation portion 102d using the photocoupler 130. However, the binary signal is not limited to the photocoupler 130, and a binary switch is used, for example. A signal may be generated. That is, a binary signal can be generated by turning on the contact switch when the displacement of the deforming portion 102d becomes larger than a certain level and turning off the contact switch when the displacement of the deforming portion 102d becomes less than a certain amount. it can. Alternatively, a terminal plate is provided in place of the photocoupler 130 to form a capacitor with the deforming portion 102d, and an electrical method such as detecting a change in the capacitance of the capacitor due to the displacement of the deforming portion 102d is used. Alternatively, the binary signal may be output by detecting the displacement itself of the deforming portion 102d and comparing the obtained displacement with a predetermined threshold value. Furthermore, the detected displacement may be output to the control circuit 150 as it is (without binarization).

  In the illustrated liquid feed pump 100, when a drive signal is applied to the piezoelectric element 106 to expand the piezoelectric element 106, the diaphragm 104 is deformed and the volume of the pump chamber 102 is reduced. Then, the liquid in the pump chamber 102 flows into the outlet side buffer chamber 118 via the outlet channel 116 and is sent from the outlet side buffer chamber 118 to the fluid channel 122. Here, the control circuit 150 of the present embodiment is equipped with a CPU (not shown), which not only applies a drive signal to the piezoelectric element 106 but also receives a binary signal from the photocoupler 130, It also has a function of acquiring various information related to the operating state. In this embodiment, the photocoupler 130 corresponds to the “displacement detection unit” and the “binary signal generation unit” in the present invention, and the control circuit 150 corresponds to the “operation state detection unit” in the present invention.

  FIG. 2 is an explanatory diagram showing the result of actual measurement of the displacement Dp of the deforming portion 102d of the pump chamber 102 when a drive signal is applied to the piezoelectric element 106. FIG. FIG. 2A illustrates a drive signal applied to the piezoelectric element 106. FIG. 2B shows the actual measurement result of the displacement Dp of the deforming portion 102d. The positive displacement Dp shown in FIG. 2B indicates that the internal pressure of the pump chamber 102 is increased and the deformed portion 102d is deformed so as to expand outward, and the negative displacement Dp is the pump displacement Dp. It shows that the internal pressure of the chamber 102 has decreased and the deformed portion 102d has been deformed so as to shrink inward.

  As shown in FIG. 2A, it is assumed that a drive signal of 1 pulse is applied. Since the piezoelectric element 106 expands when the voltage of the drive signal (drive voltage) increases, the volume of the pump chamber 102 decreases. As a result, at the same time as the voltage of the drive signal rises, the internal pressure of the pump chamber 102 suddenly rises, and the displacement Dp of the deforming portion 102d suddenly increases to the plus side, as shown in FIG. 2B. Further, while the voltage of the drive signal is maintained at the maximum voltage, the deformation amount of the piezoelectric element 106 does not change, and therefore the volume of the pump chamber 102 does not change. For this reason, as the liquid flows out from the pump chamber 102, the internal pressure of the pump chamber 102 decreases, and accordingly, the displacement Dp of the deformable portion 102d also decreases. At this time, an inertial force acts on the liquid passing through the outlet channel 116 due to the inertance of the outlet channel 116, so that the internal pressure of the pump chamber 102 becomes negative and the displacement Dp of the deforming portion 102d becomes negative. In this embodiment, since the voltage of the drive signal is lowered while the internal pressure of the pump chamber 102 is negative, the displacement of the piezoelectric element 106 is reduced. Thereafter, the displacement Dp of the deforming portion 102d oscillates at a constant period as shown in FIG. 2B, although the drive signal has not changed. This indicates that the internal pressure of the pump chamber 102 is oscillating at a constant cycle.

  Such pressure oscillation is generated by the following mechanism. First, when the drive signal is applied, the piezoelectric element 106 expands, and the internal pressure of the pump chamber 102 rapidly increases. At this time, since the outlet side buffer chamber 118 exists between the outlet channel 116 and the fluid channel 122, the liquid pressurized in the pump chamber 102 moves to the outlet side buffer chamber 118, and the pump chamber 102. The internal pressure of immediately falls. When this phenomenon is viewed from the pump chamber 102 side, the fluid flow path 122 existing beyond the outlet side buffer chamber 118 hardly affects the pump chamber 102 because the outlet side buffer chamber 118 exists. This is the same state as when the outlet channel 116 is simply connected. For this reason, when the volume of the pump chamber 102 decreases and the liquid for the excluded volume is about to flow out, only the flow resistance and inertance of the outlet flow path 116 are affected, so the liquid for the excluded volume flows. The time required for this is shortened. The liquid that has moved through the outlet channel 116 has an inertial force due to the inertance of the outlet channel 116, so that the internal pressure of the pump chamber 102 becomes negative, and the liquid is supplied from the inlet side buffer chamber 112 to the pump chamber 102. It becomes possible. At this time, since the inertance of the outlet channel 116 is larger than the inertance of the communication path between the inlet side buffer chamber 112 and the pump chamber, the liquid moving in the outlet channel 116 hardly returns to the pump chamber 102. Instead, the liquid in the inlet side buffer chamber 112 is supplied to the pump chamber 102 exclusively. This is because the inertance of the flow path on the inlet side (the passage portion provided with the check valve 110) is significantly smaller than the inertance of the flow path on the outlet side (outlet flow path 116).

Here, inertance is a characteristic value of the flow path, and indicates the ease of fluid flow when the fluid in the flow path is about to flow when pressure is applied to one end of the flow path. For example, in the simplest case, a fluid having a density ρ (here, a liquid) is filled in a channel having a cross-sectional area S and a length L, and a pressure P (exactly, It is assumed that a pressure difference P) at both ends is added. A force of pressure P × cross-sectional area S acts on the fluid in the channel, and as a result, the fluid in the channel flows out. If the acceleration of the fluid at that time is a, the mass of the fluid in the flow path is density ρ × cross-sectional area S × length L.
P = ρ × L × a (1)
Is obtained. Furthermore, when the volume flow rate flowing through the flow path is Q and the flow velocity of the fluid flowing through the flow path is v,
Q = v × S So
dQ / dt = a × S (2)
Holds. Substituting equation (2) into equation (1),
P = (ρ × L / S) × (dQ / dt) (3)
It becomes. This equation is an equation representing the equation of motion of the fluid in the flow path using the pressure P applied to one end of the flow path (more precisely, the pressure difference at both ends) and dQ / dt. Equation (3) indicates that if the same pressure P is applied, dQ / dt increases (that is, the flow velocity changes greatly) as (ρ × L / S) decreases. This (ρ × L / S) is a value called inertance.

  In the liquid feed pump 100 of the present embodiment shown in FIG. 1, the inertance of the outlet channel 116 is large because the inner diameter is small and the passage length is long. On the other hand, the inertance of the flow path on the inlet side of the pump chamber 102 takes a small value because the passage length of the passage portion provided with the check valve 110 is short. For this reason, when the pump chamber 102 has a negative pressure, the liquid on the outlet side with a large synthetic inertance is hardly sucked, and the liquid on the inlet side with a small synthetic inertance is sucked into the pump chamber 122 exclusively.

  On the other hand, the liquid that has flowed into the outlet side buffer chamber 118 does not readily flow out because the flow path resistance of the fluid flow path 122 is high, so the internal pressure of the outlet side buffer chamber 118 rises. At this time, since the internal pressure of the pump chamber 102 is decreasing, the inertial force of the liquid in the outlet channel 116 gradually decreases. Since a check valve is not provided between the pump chamber 102 and the outlet side buffer chamber 118, a reverse flow from the outlet side buffer chamber 118 to the pump chamber 102 eventually occurs. Even if the liquid flows back into the pump chamber 102, the liquid does not flow out to the inlet side buffer chamber 112 by the check valve 110. Therefore, the internal pressure of the pump chamber 102 rises again, and the liquid that has flowed back flows into the outlet side buffer chamber 102. It flows toward 118. Thereby, the pump chamber 102 again becomes negative pressure, and it becomes possible to supply more liquid from the inlet side buffer chamber 112 to the pump chamber 102. By repeating such vibrations, the check valve 110 can be opened a plurality of times (twice in the example shown in FIG. 2) by a single drive, and the liquid can be supplied to the pump chamber 102.

  This phenomenon tends to be understood as propagation due to pressure waves in the liquid that normally propagate between the pump chamber 102 and the outlet side buffer chamber 118. However, in the liquid delivery pump 100 of this embodiment, the distance between the pump chamber 102 and the outlet side buffer chamber 118 is short (no matter how long it is about 10 cm (centimeter)), and the speed of sound in the liquid is about 1000 m / sec. (Meter / second), the vibration period due to the propagation of the pressure wave should be 0.2 msec (milliseconds) at the maximum. However, the natural vibration period of the vibration shown in FIG. 2B is about 0.4 msec, which cannot be explained by the propagation of the pressure wave.

However, this phenomenon can be explained by considering the compressibility of the liquid (ie, treating the liquid as a compressible fluid). That is, considering the resonance formed by the compliance of the pump chamber 102, the inertance of the outlet channel 116, and the compliance of the outlet side buffer chamber 118, the natural vibration period T can be expressed by the following equation (4).
T = 2π (MC) ^1/2 (4)
Here, M is an inertance of the outlet channel 116, and C is a combined compliance of the pump chamber 102 and the outlet side buffer chamber 118. Further, when the compliance of the pump chamber 102 is C ₁ and the compliance of the outlet side buffer chamber 118 is C ₂ , the composite compliance C is given by the following equation (5).
C = 1 / {1 / C ₁ + 1 / C ₂ } (5)
Assuming resonance having the natural vibration period T of the above equation (4), it is possible to explain the phenomenon in which the internal pressure of the pump chamber 102 shown in FIG.

Here, the compliance indicates expansion of volume or compression of fluid due to deformation of the fluid chamber when pressure is applied to the fluid chamber. For example, in the simplest case, a fluid chamber having a volume V and a bulk modulus K is filled with a fluid having a compressibility κ _F (here, a liquid), and pressure P is applied to the liquid in the fluid chamber. Shall. At this time, the volume change amount ΔV1 due to the deformation of the fluid chamber is:
ΔV1 = V / K × P (6)
It becomes. The volume change ΔV2 due to the compression of the liquid is
ΔV2 = V × κ _F × P (7)
It becomes. Therefore, the amount of change ΔV in the apparent fluid chamber volume with respect to the pressure P is
ΔV = V × (1 / K + κ _F ) × P (8)
This V × (1 / K + κ _F ) is a value called compliance. Here, when the fluid chamber is a member having the same elastic modulus and the liquid is a fluid having the same compressibility, the equation (5) can be used to change the apparent volume of the fluid chamber if the same pressure P is applied. The quantity ΔV is proportional to the volume V of the fluid chamber.

  Further, from the equations (4) and (5), it is expected that the natural vibration period T varies depending on the compliance (volume) of the pump chamber 102 and the compliance (volume) of the outlet side buffer chamber 118. The phenomenon has been confirmed.

  When a drive signal is applied to the piezoelectric element 106, pressure vibration is generated in the pump chamber 102 due to resonance based on the above mechanism, and as a result, as shown in FIG. Will occur. In addition, as described above with reference to FIG. 1, in this embodiment, the variation in the displacement of the deforming portion 102d is detected using the photocoupler 130, and while the displacement of the deforming portion 102d is smaller than the threshold value Dth, Although the light receiving element of the photocoupler 130 does not receive the reflected light from the deforming portion 102d, the light receiving element receives the reflected light when the displacement of the deforming portion 102d becomes larger than the threshold value Dth. As a result, a binary signal Ds from the photocoupler 130 is in the Low state while the light receiving element is not receiving the reflected light, and is in the Hi state while the light receiving element is receiving the reflected light. Is output. FIG. 2C shows a state in which a binary signal Ds is output from the photocoupler 130 when a drive signal is applied to the piezoelectric element 106. In the present embodiment, the variation of the displacement of the deforming portion 102d due to such pressure vibration is detected, and various types of information regarding the operating state of the liquid feed pump 100 are detected. Note that the binary signal Ds of this embodiment is in the low state when the displacement Dp of the deforming portion 102d is small (or negative), and enters the Hi state when the displacement Dp increases, but the displacement Dp is A signal that is in the Hi state when it is small (or when it is negative) and becomes Low when the displacement Dp increases may be used as the binary signal Ds.

B. Bubble detection method:
FIG. 3 is an explanatory diagram illustrating the displacement Dp of the deforming part 102d obtained when bubbles exist in the pump chamber 102 and the binary signal Ds output from the photocoupler 130. 3A shows a driving signal applied to the piezoelectric element 106, FIG. 3B shows a displacement Dp of the deforming portion 102d, and FIG. 3C shows a binary signal Ds. ing.

  As apparent from the comparison with the case where bubbles are not shown in FIG. 2, when bubbles are present in the pump chamber 102, the internal pressure of the pump chamber 102 is increased by applying a drive signal to the piezoelectric element 106. Due to the compression of the bubbles, the displacement of the piezoelectric element 106 is absorbed, and the amount of increase in internal pressure is reduced. For this reason, pressure vibrations (and fluctuations in the displacement of the deforming portion 102d) due to the above-described resonance among the pump chamber 102, the outlet channel 116, and the outlet side buffer chamber 118 hardly occur. That is, the increase / decrease in the displacement Dp of the deformable portion 102d accompanying the increase in internal pressure when the voltage of the drive signal is increased (hereinafter referred to as the first wave) is shown in FIGS. 2 (b) and 3 (b). ), The increase or decrease of the displacement Dp of the deforming portion 102d due to the subsequent pressure vibration due to resonance (hereinafter, these are expressed as the second wave, the third wave, and the fourth wave in order from the top. 3) hardly occurs in FIG. 3B where bubbles exist. As a result, the pulse of the binary signal Ds corresponding to the first wave is generated in both FIG. 2C and FIG. 3C, but the pulse corresponding to the subsequent second wave, The pulse corresponding to is not seen in FIG. 3C where bubbles are present. In the following, the pulse of the binary signal Ds corresponding to the first wave is referred to as a first pulse, the pulse corresponding to the second wave is referred to as a second pulse, and the pulse corresponding to the third wave is referred to as a third pulse. A pulse corresponding to the fourth wave is called a fourth pulse. Therefore, if the second pulse can be detected in the binary signal Ds, it is possible to determine that there are no bubbles in the pump chamber 102, and conversely, if the second pulse cannot be detected, it can be determined that bubbles exist in the pump chamber 102. .

  In addition, since the magnitude | size of a 1st wave will become small if a bubble exists in the pump chamber 102, it is also possible to determine the presence or absence of a bubble by detecting the magnitude | size of the displacement Dp of the deformation | transformation part 102d. However, this method is to determine that bubbles are present when the magnitude of the first wave is reduced to some extent, and to what extent is it determined that bubbles have been generated (that is, setting a threshold) Depends on the accuracy of judgment. On the other hand, in the method of the present embodiment described above, since it can be determined based on whether or not the second pulse based on the second wave has occurred, it is possible to accurately determine the presence or absence of bubbles. Become.

  In the above-described embodiment, since the displacement of the deforming portion 102d is detected using the photocoupler 130, the binary signal Ds from the photocoupler 130 is input to the control circuit 150. For this reason, the presence / absence of bubbles in the pump chamber 102 is determined based on whether or not the second pulse corresponding to the second wave of the displacement Dp of the deforming portion 102d is generated. On the other hand, when the displacement Dp itself of the deforming portion 102d is detected and input to the control circuit 150 by, for example, an electrical method using a change in capacitance, the second wave of the displacement Dp is generated. The presence or absence of bubbles in the pump chamber 102 may be determined based on whether or not they have occurred.

C. Detection method of pumping pressure:
When the second pulse is detected subsequent to the first pulse of the binary signal Ds as illustrated in FIG. 2C, the length of time from the generation of the first pulse to the generation of the second pulse. Includes information on the pressure at which the liquid feed pump 100 pumps the liquid (more precisely, the pressure in the outlet-side buffer chamber 118). This is because, as described above, the first pulse of the binary signal Ds is a pulse corresponding to the first wave of the displacement Dp of the deforming portion 102d, and the second pulse is a pulse corresponding to the second wave. Further, as described above, the second wave of the displacement Dp is caused by the pressure difference between the pump chamber 102 and the outlet side buffer chamber 118 due to the liquid flowing in the outlet channel 116 from the pump chamber 102 toward the outlet side buffer chamber 118. It is generated by being pulled back into the pump chamber 102. Therefore, when the pressure difference between the pump chamber 102 and the outlet side buffer chamber 118 is increased, the force for pulling back the liquid in the outlet channel 116 is increased, so that the second wave is generated earlier, and therefore the second pulse is also generated earlier.

  Here, during the period from the end of the first wave (the displacement Dp of the deforming portion 102d returns to the initial level) to the generation of the second wave, it flows out from the pump chamber 102 toward the outlet side buffer chamber 118. This is a period until the liquid is pushed back from the outlet side buffer chamber 118 and returns. Therefore, the inside of the pump chamber 102 is generally negative pressure until the second wave is generated. Further, since the pump chamber 102 is connected to the inlet side buffer chamber 112 via the check valve 110, the pressure in the pump chamber 102 does not fluctuate greatly during the period until the second wave is generated. For this reason, the pressure difference between the pump chamber 102 and the outlet side buffer chamber 118 in the period from the end of the first wave to the generation of the second wave (hereinafter, this period is referred to as a negative pressure period) is The pressure in the outlet side buffer chamber 118 is mainly determined. That is, if the pressure in the outlet side buffer chamber 118 is high, the negative pressure period is shortened. In other words, if the negative pressure period is short, it can be said that the pressure in the outlet side buffer chamber 118 is high. Furthermore, it has been experimentally confirmed that the time from the generation of the first wave to the end thereof (the pulse width of the first pulse) hardly changes. Therefore, regarding the time from the generation of the first wave (first pulse) to the generation of the second wave (second pulse), the higher the pressure in the outlet-side buffer chamber 118, the shorter the time. Can do.

  FIG. 4 is an actual measurement result showing the relationship between the time from the first pulse to the second pulse and the pressure in the outlet side buffer chamber 118. In the example shown in FIG. 4, the time from the end of the first pulse to the generation of the second pulse is measured as the time from the first pulse to the second pulse. However, almost the same tendency is established when the time from the first pulse generation to the second pulse generation is used.

  As shown in FIG. 4, when the pressure in the outlet-side buffer chamber 118 (and hence the pressure at which the liquid is pumped into the fluid flow path 122) decreases, the time from the first pulse to the second pulse increases. From this, when the second pulse is detected following the first pulse of the binary signal Ds, the liquid feed pump 100 pumps the liquid by detecting the time from the first pulse to the second pulse. The pressure (pumping pressure) to be detected can be detected. That is, a threshold time is set in advance, and when the detected time is longer than the threshold time, it can be determined that the liquid pumping pressure has decreased. Alternatively, the relationship shown in FIG. 4 (the relationship between the detection time and the pumping pressure) is stored in the control circuit 150 as a lookup table, and the pumping pressure is detected by referring to this lookup table. You can also.

  Further, as illustrated in FIG. 5, when the circulation flow path is configured by returning the liquid flowing through the fluid flow path 122 to the inlet flow path 114, the liquid flows through the sealed flow path. It is difficult to notice that the pressure has dropped. In this regard, in this embodiment, the pressure in the outlet side buffer chamber 118 can be monitored by detecting the time from the first pulse to the second pulse, so that the pumping pressure is immediately recognized. It becomes possible to do.

D. Detection method of gas dissolved amount and liquid feeding amount:
In addition, as illustrated in FIG. 2C, when the third pulse and the fourth pulse of the binary signal Ds are detected, the time from the generation of the third pulse to the generation of the fourth pulse is detected. By doing this, it is possible to detect the dissolved amount (gas dissolved amount) of gas such as air dissolved in the liquid. This is due to the following reason.

First, the natural vibration period T of resonance generated by the pump chamber 102 and the outlet side buffer chamber 118 via the outlet channel 116 is expressed by the above-described equation (4). Moreover, the synthetic | combination compliance C which appears in (4) Formula is represented by (5) Formula mentioned above. The compliance C ₁ (compliance of the pump chamber 102) and the compliance C ₂ (compliance of the outlet side buffer chamber 118) appearing in the equation (5) are respectively given by the following equations using the equation (8).
C ₁ = V ₁ × (1 / K + κ _F ) (9)
C ₂ = V ₂ × (1 / K + κ _F ) (10)
Here, V ₁ is the volume of the pump chamber 102, and V ₂ is the volume of the outlet side buffer chamber 118. In the present embodiment, the pump chamber 102, the outlet channel 116, and the outlet side buffer chamber 118 are made of very hard members such as stainless steel, and the elastic modulus K is very large. In the equations (10) and (10), changes in the volumes of the pump chamber 102 and the outlet side buffer chamber 118 are almost ignored. (9) and (10), and rearranging are substituted into (5) and (4), the natural vibration period T is proportional to the square root of the compression ratio kappa _F of the liquid. And since the compression rate (kappa) _F of a liquid becomes high as the dissolved amount of the gas in a liquid increases, it is thought that the natural vibration period T becomes long, so that the dissolved amount of the gas in a liquid increases. Further, since the dissolved amount of gas in the liquid is increased compressibility kappa _F of the liquid becomes high, effectively applying it will not be pressurized fluid in the pump chamber 102, feed volume of the liquid supply pump 100 is lowered It is considered a thing. Therefore, the liquid feed amount and the natural vibration period T of the liquid feed pump 100 were measured while changing the gas dissolved amount in the liquid.

  FIG. 6 is an explanatory diagram showing the relationship between the dissolved gas amount in the liquid and the natural vibration period T obtained by actual measurement. As shown in FIG. 6, the natural vibration period T becomes longer as the dissolved gas amount increases. Since the natural vibration period T corresponds to the time from when the third pulse of the binary signal Ds is detected until the fourth pulse is detected, the period from when the third pulse is generated until the fourth pulse is generated. By detecting the time, it is possible to detect the dissolved amount (gas dissolved amount) of gas such as air dissolved in the liquid.

  FIG. 7 is an explanatory diagram showing the relationship between the dissolved gas amount in the liquid obtained by actual measurement and the liquid feed amount of the liquid feed pump 100. As shown in FIG. 7, the liquid feeding amount decreases as the gas dissolved amount increases. As shown in FIG. 6, since there is a strong correspondence (correlation) between the dissolved gas amount and the natural vibration period T, there is also a correlation between the liquid supply amount and the natural vibration period T. There is a possibility. Therefore, FIG. 8 is obtained by arranging the relationship between the natural vibration period T and the liquid feeding amount measured for the same dissolved gas amount. As shown in FIG. 8, a strong correlation is established between the natural vibration period T (in this embodiment, the time from the generation of the third pulse to the generation of the fourth pulse) and the amount of liquid to be fed. ing. From this, it is also possible to detect the liquid supply amount of the liquid supply pump 100 by detecting the time from the generation of the third pulse to the generation of the fourth pulse in the binary signal Ds.

  Thus, in the liquid feed pump 100 of the present embodiment, the liquid feed amount and the dissolved gas amount in the liquid can be detected by measuring the time from the third pulse to the fourth pulse of the binary signal Ds. . For this reason, it is not necessary to separately provide a flow meter or the like for detecting the liquid feeding amount. In addition, a special device is required to detect the dissolved amount of gas in the liquid, but in this embodiment, the dissolved amount of gas in the liquid can be detected without using a special device. In particular, as illustrated in FIG. 5, when the liquid feed pump 100 is incorporated in a circulation flow path, the liquid flows through the sealed flow path, so that the liquid feed amount and dissolved gas amount are detected. It is difficult. In this respect, in the present embodiment, it is possible to always monitor the liquid feeding amount and the dissolved gas amount by detecting the natural vibration period T.

In the above description, the natural vibration period T is obtained by measuring the time from the third pulse to the fourth pulse, not the time from the second pulse to the third pulse of the binary signal Ds. This is due to the following reason. As shown in FIG. 1, in the liquid delivery pump 100 of the present embodiment, the pump chamber 102 is connected to the inlet side buffer chamber 112 via the check valve 110, and when the pump chamber 102 becomes negative pressure, The stop valve 110 opens and the pump chamber 102 and the inlet side buffer chamber 112 communicate with each other. When the pump chamber 102 and the inlet-side buffer chamber 112 communicates deviate the natural vibration period T by as if a state such as compliance C ₁ in the pump chamber 102 is increased significantly. As shown in FIG. 2B, a period during which the pump chamber 102 is negative between the second pulse and the third pulse (that is, the pump chamber 102 and the inlet side buffer chamber 112 communicate with each other). Therefore, the natural vibration period T cannot be measured accurately. On the other hand, since the period in which the pump chamber 102 becomes negative pressure does not occur between the third pulse and the fourth pulse (even if it occurs, it is only a short period), the accurate natural vibration period T is measured. can do. For the above reason, in this embodiment, the natural vibration period T is obtained by measuring the time between the third pulse and the fourth pulse of the binary signal Ds. Of course, if so much measurement accuracy is not required, the natural vibration period T may be obtained by measuring the time between the second pulse and the third pulse of the binary signal Ds. Alternatively, when the attenuation in the outlet channel 116 becomes strong, the amplitude of the third wave of the displacement Dp of the deforming portion 102d becomes small, and the fourth pulse of the binary signal Ds may not be generated. In such a case, the time between the second pulse and the third pulse of the binary signal Ds is measured (in some cases, the time between the first pulse and the second pulse is measured). The natural vibration period T may be obtained.

E. Modified example:
In the above-described embodiments, the deformation portion 102d provided on a part of the wall surface of the pump chamber 102 has been described as deforming outward when the internal pressure of the pump chamber 102 increases. However, any member that can be deformed by the internal pressure of the pump chamber 102 can be used as the deforming portion 102d.

  FIG. 9 is an explanatory view illustrating a modified example in which a member (valve member) constituting the valve portion of the check valve 110 is used as the deforming portion 102d. That is, the check valve 110 is opened when the internal pressure of the pump chamber 102 becomes negative (lower than the pressure in the inlet side buffer chamber 112), and is closed in other cases. Therefore, a photocoupler 132 is provided above the check valve 110. When the check valve 110 is in a closed state, light from the light emitting element of the photocoupler 132 is reflected by the valve member of the check valve 110 and received. The light is received by the element.

  In this case, when the internal pressure of the pump chamber 102 becomes negative, the check valve 110 is opened (that is, the deforming portion 102d is deformed), and the light receiving element of the photocoupler 132 does not receive the reflected light. The negative pressure period can be detected directly. As a result, it is possible to detect the pressure of the liquid feed pump 100. Further, in the above-described modified example, instead of the photocoupler 132, other methods such as a change in electrostatic capacitance between the check valve 110 and the check valve 110 coated with a thin film piezoelectric member are used. The displacement of the valve member may be detected by using an electrical method utilizing distortion.

  As mentioned above, although the liquid feeding pump 100 of a present Example was demonstrated, this invention is not restricted to all the said Examples, It is possible to implement in a various aspect in the range which does not deviate from the summary. For example, a heat source generated by a projector or the like can be applied to a fluid circulation device that cools a fluid such as a refrigerant liquid by circulation. In addition, the fluid discharge device used to form microcapsules that contain drugs and nutrients, and the diameter of the fluid flow path tip is reduced to allow fluid (water, physiological saline, drug solution, etc.) to flow from the tip to high pressure. The present invention can be applied to various electronic devices such as a surgical instrument such as a jet knife and a medical device including a drug solution ejecting tool that ejects the target object by jetting the target. Further, the outlet side buffer chamber 118 and the inlet side buffer chamber 112 in the liquid feed pump 100 of the present embodiment do not necessarily have to be made of a very hard member such as stainless steel, and if a member having a low elastic modulus is used. Even when the volume is small, a sufficiently large compliance can be obtained, and a very small liquid feeding pump can be realized.

100 ... Liquid feed pump, 102 ... Pump chamber, 102d ... Deformation part,
104 ... Diaphragm, 106 ... Piezoelectric element, 108 ... Case,
110 ... Check valve, 112 ... Inlet side buffer chamber, 114 ... Inlet flow path,
116: outlet channel, 118: outlet side buffer chamber, 122: fluid channel,
130 ... Photocoupler, 132 ... Photocoupler, 150 ... Control circuit

Claims (8)

A liquid feed pump for feeding liquid in the pump chamber by changing the volume of the pump chamber,
An outlet channel connected to the pump chamber;
An outlet-side buffer chamber having a larger compliance than the pump chamber and constituting a resonance system with the pump chamber by being connected to the pump chamber via the outlet channel;
A deformation part deformed by an internal pressure of the pump chamber;
A displacement detection unit for detecting a change in displacement of the deformation unit;
A liquid feed pump comprising: an operation state detection unit that detects an operation state of the liquid feed pump based on a change in displacement of the deformation unit. The liquid delivery pump according to claim 1,
A binary signal generation unit that generates a binary signal based on a predetermined threshold value of the displacement of the deformation unit;
The operating state detecting unit is a detecting unit that is a detecting unit that detects an operating state of the transmitting pump based on the binary signal. The liquid delivery pump according to claim 2,
The operation state detection unit is a detection pump that detects the presence or absence of bubbles mixed in the pump chamber based on the presence or absence of the pulse of the binary signal generated after the volume of the pump chamber is reduced. . The liquid feed pump according to claim 2 or 3, wherein
The operation state detection unit is a liquid supply pump that is a detection unit that detects a pressure for pumping a liquid based on a time from when the volume of the pump chamber is reduced to when the pulse of the binary signal is detected. It is a liquid feeding pump as described in any one of Claim 2 thru | or 4, Comprising:
The operation state detection unit is a detection unit that detects a dissolved amount of gas in the liquid based on time intervals of a plurality of pulses generated in the binary signal after the volume of the pump chamber is reduced. Liquid pump. It is a liquid feeding pump as described in any one of Claim 2 thru | or 5, Comprising:
The operation state detection unit is a detection unit that detects a liquid feeding amount per time of the liquid based on a time interval of a plurality of pulses generated in the binary signal after reducing the volume of the pump chamber. A liquid pump.   A circulation device using the liquid feed pump according to any one of claims 1 to 6.   A medical device using the liquid feeding pump according to any one of claims 1 to 6.

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