JP2013060925A - Liquid feed pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable easy removal of air bubbles mixed into a pump chamber in a liquid feed pump driving a diaphragm by using a piezoelectric element.SOLUTION: By keeping the tip of a column part of a drive member including the base part and the column part erected from the base part connected to the diaphragm from the outside of the pump chamber, and by applying a charge to elongate the piezoelectric element, the base part can be separated from the diaphragm. In the liquid feed pump like this, since a fluid is set to be force-fed by returning the volume of the pump chamber to an initial state after increasing the volume of the pump chamber from the initial state, the volume of the pump chamber in the initial state can be set indefinitely small. Consequently, the residence of the air bubbles in the pump chamber can be avoided.

Description

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

  There is widely known a liquid feed pump that pumps a liquid in a pump chamber by forming a part of the pump chamber with a diaphragm and deforming the diaphragm with a piezoelectric element. In this liquid feed pump, when a voltage is applied to the piezoelectric element, the piezoelectric element expands to deform the diaphragm and reduce the volume of the pump chamber. As a result, the fluid in the pump chamber is pressurized and sent. When the applied voltage is removed and the piezoelectric element is returned to its original length, the diaphragm returns to its original shape and the volume of the pump chamber increases, and accordingly, liquid is supplied into the pump chamber. Thereafter, when a voltage is applied to the piezoelectric element again, the liquid supplied to the pump chamber is pressurized and fed.

  In such a liquid feed pump, when bubbles are mixed in the pump chamber, even if the diaphragm is deformed, the bubbles are crushed and it is difficult to pressurize the liquid, and the pump performance is lowered. Therefore, a technique (for example, Patent Document 1) has been proposed in which bubbles mixed into the pump chamber are sucked and removed together with the liquid in the pump chamber.

JP 2011-46015 A

  However, the liquid feed pump that drives the diaphragm using the piezoelectric element has a problem that it is difficult to remove bubbles mixed in the pump chamber. This is because a member having a relatively large area called a diaphragm is deformed by using an actuator with a small stroke called a piezoelectric element, so that a portion where the flow of liquid stagnates easily occurs in the peripheral portion of the pump chamber. This is because, since the portion is fixed, it is difficult to remove the bubble if the bubble adheres to this portion.

  The present invention has been made to solve at least a part of the above-described problems of the prior art. In a liquid feed pump that drives a diaphragm using a piezoelectric element, it is easy to remove bubbles mixed in a pump chamber. The purpose is to provide removable technology.

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 that deforms a diaphragm constituting a part of the pump chamber and changes the volume of the pump chamber to pump the fluid,
A driving member provided outside the pump chamber and connected to the diaphragm;
A piezoelectric element that deforms the diaphragm via the driving member;
Voltage applying means for applying a voltage to the piezoelectric element,
The driving member has a base part and a column part standing from the base part, and a tip end of the pillar part is connected to the diaphragm,
The gist of the present invention is that the piezoelectric element is a piezoelectric element that expands when the voltage is applied and separates the base portion of the driving member from the diaphragm.

  In the liquid feed pump of the present invention having such a configuration, when a voltage is applied to extend the piezoelectric element, the base portion and the column portion are separated from the diaphragm and the diaphragm is deformed to increase the volume of the pump chamber. . Then, when the applied voltage is removed and the piezoelectric element is returned to its original length, the base part and the pillar part are returned to their original positions, and the diaphragm is restored to its original shape. Decrease. By increasing or decreasing the volume of the pump chamber in this way, fluid is pumped from the pump chamber.

  In this way, after increasing the volume of the pump chamber, the fluid is pumped by decreasing (returning) the volume of the pump chamber. Accordingly, the volume of the pump chamber in the initial state (before the operation of the liquid feed pump) does not affect the amount of fluid delivered, and thus the volume of the pump chamber in the initial state can be reduced as much as possible. For this reason, for example, if there is a place where bubbles easily accumulate in the pump chamber, the portion of the pump chamber can be crushed in the initial state. Of course, the entire pump chamber can be crushed. As a result, in the liquid feeding pump of the present invention, it is possible to avoid bubbles remaining in the pump chamber.

  If the volume of the pump chamber in the initial state is made as small as possible, the volume ratio between when the volume of the pump chamber is increased and when the volume is restored can be increased. As a result, the fluid in the pump chamber can be pumped by a high pressure, so that a high-performance liquid feed pump can be realized.

  Moreover, in the liquid feed pump of this invention mentioned above, it is good also as providing a piezoelectric element in the several places around the pillar part of a drive member. Note that “providing piezoelectric elements at a plurality of locations around the pillar portion” is not limited to providing a plurality of piezoelectric elements so as to surround the pillar portion, and a plurality of piezoelectric elements are provided in a region around the pillar portion. It is also included to be provided unevenly.

  If it carries out like this, a diaphragm can be driven with big force by separating a base part (and pillar part) from a diaphragm with a some piezoelectric element. Therefore, it is possible to improve the ability of the liquid feed pump to pump the fluid.

  In the liquid feed pump of the present invention described above, a piezoelectric element having a circular cross section may be provided so as to surround the column portion of the drive member. If it carries out like this, the force which spaces apart the base part of a drive member from a diaphragm can be transmitted to a base part centering on a pillar part without deviation. Therefore, the operation of the base portion and the column portion is stabilized, so that the diaphragm can be driven stably.

  In the liquid feed pump of the present invention described above, the base and the piezoelectric element may be covered with the case member in a state where a gap is formed between the base and the piezoelectric element of the driving member. In this way, it is possible to prevent foreign matter from adhering to the base part and the piezoelectric element, and the base part and the piezoelectric element from receiving an impact from the outside.

It is sectional drawing which showed the structure of the liquid feeding pump of a present Example. It is explanatory drawing which showed the operation | movement in which a liquid feeding pump pumps a fluid. It is sectional drawing which showed the structure of the conventional liquid feeding pump. It is sectional drawing which showed 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. Structure of liquid pump:
B. Fluid pump operation:
C. Variations:

A. Liquid feed pump structure:
FIG. 1 is an explanatory view showing the structure of a liquid feed pump 100 of the present embodiment. FIG. 1A shows a cross-sectional view of the liquid feed pump 100, and FIG. 1B shows a top view of the liquid feed pump 100. As shown in the figure, the liquid feed pump 100 of this embodiment is roughly composed of a piezoelectric element case 110 and a flow path block 120.

  A cylindrical piezoelectric element 114 is accommodated inside the piezoelectric element case 110. On the upper surface side of the piezoelectric element case 110, a convex portion 110b is provided in which the inner wall of the piezoelectric element case 110 protrudes to the inside of the case. The upper surface of the piezoelectric element 114 is fixed to the convex portion 110b. A bottom plate 112 (base) is provided at the bottom of the piezoelectric element 114, and a central column 118 (column) is erected on the bottom plate 112. In the present embodiment, the bottom plate 112 and the central column 118 are described as being formed as separate members, but the bottom plate 112 and the central column 118 may be integrally formed. Further, the bottom plate 112 and the central column 118 of this embodiment correspond to the “driving member” of the present invention.

  In addition, a very shallow circular concave portion is provided above the convex portion 110b of the piezoelectric element case 110, and a disk-shaped diaphragm 116 formed of a stainless steel thin plate is bonded to the bottom of the concave portion. In this state, the center portion of the diaphragm 116 is bonded to the upper end portion of the center column 118.

  The piezoelectric element 114 in the piezoelectric element case 110 is connected to the voltage application unit 200 (voltage application means). As will be described in detail later, when the fluid is pumped by the liquid feed pump 100, a voltage is applied from the voltage application unit 200 to the piezoelectric element 114.

  The flow path block 120 is placed on the upper surface of the piezoelectric element case 110 and firmly attached to the piezoelectric element case 110 by screws or the like. An outlet connection pipe 122 is erected on the left side surface of the flow path block 120 in the drawing. An outlet channel 123 is formed inside the outlet connection pipe 122, and the outlet channel 123 is open on the bottom side of the channel block 120. An inlet side buffer chamber 124 is formed on the upper surface side of the flow path block 120. A passage penetrating to the bottom surface side of the flow path block 120 is formed in the central portion of the inlet side buffer chamber 124, and a check valve 121 is provided at a position where the passage opens to the bottom surface side. Further, an inlet connecting pipe 125 is erected on the right side of the channel block 120 in the drawing, and an inlet channel 126 is formed inside the inlet connecting pipe 125. The inlet channel 126 is formed on the inlet side. The buffer chamber 124 is opened. The inlet connection pipe 125 is connected to a fluid supply source (not shown) via, for example, a tube.

B. Fluid pump operation:
FIG. 2 is an explanatory view showing an operation in which the liquid feed pump 100 pumps fluid. When starting the fluid pumping, first, the piezoelectric element 114 is extended by applying a voltage from the voltage application unit 200 to the piezoelectric element 114. At this time, when the bottom plate 112 is pushed by the piezoelectric element 114 and moves away from the diaphragm 116, the diaphragm 116 is pulled by the central column 118 and deformed. As a result, as shown in FIG. 2A, the volume of the space (pump chamber 130) between the bottom surface of the flow path block 120 and the diaphragm 116 increases, and the pump chamber 130, the inlet side buffer chamber 124, The inlet channel 126 and the outlet channel 123 are filled with fluid.

  Thereafter, when the positive charge applied to the piezoelectric element 114 is removed, as shown in FIG. 2B, the piezoelectric element 114 returns to its original length, so that the central column 118 attempts to return to the original position. The fluid in the pump chamber 130 is pressurized by the diaphragm 116. Here, since the check valve 121 is provided between the pump chamber 130 and the inlet side buffer chamber 124, the fluid in the pump chamber 130 does not flow back into the inlet side buffer chamber 124. As a result, the fluid pressurized by the diaphragm 116 is pushed out from the outlet channel 123.

  Subsequently, when a voltage is applied and the piezoelectric element 114 is extended as shown in FIG. 2C, the diaphragm 116 is deformed via the bottom plate 112 and the central column 118, and the volume of the pump chamber 130 is increased. The pump chamber 130 becomes negative pressure. This negative pressure acts in the direction in which the fluid (inlet side fluid) in the inlet side buffer chamber 124 is sucked into the pump chamber 130 and at the same time in the direction in which the fluid (outlet side fluid) in the outlet channel 123 is sucked. Works. However, in reality, the fluid on the outlet side is hardly sucked, and the fluid on the inlet side is sucked into the pump chamber 130 as shown in FIG. Compared to the inertance of the outlet side channel (outlet channel 123), the inlet side channel (the inlet side buffer chamber 124 and the passage portion penetrating from the inlet side buffer chamber 124 to the bottom side of the pump chamber 130). This is because the inertance is significantly smaller.

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, the inertance of the outlet channel 123 has a large value 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 has a small value because the length of the passage portion penetrating from the inlet side buffer chamber 124 to the bottom surface side of the pump chamber 130 is short. For this reason, when the pump chamber 130 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 130 exclusively.

  When the fluid is sucked into the pump chamber 130 in this way, the voltage applied to the piezoelectric element 114 is removed, and the diaphragm 116 is returned to its original shape, thereby pushing out the fluid in the pump chamber 130 from the outlet channel 123, and then the piezoelectric element. The fluid is sucked into the pump chamber 130 by applying a voltage again to the diaphragm 114 to deform the diaphragm 116. By repeatedly applying a voltage to the piezoelectric element 114 and removing the applied voltage in this manner, the operation of pushing the fluid sucked into the pump chamber 130 from the inlet-side flow path into the outlet-side flow path is repeated. Pump the fluid.

  As described above, in the liquid feeding pump 100 according to the present embodiment, after the fluid is sucked into the pump chamber 130 by increasing the volume of the pump chamber 130, the sucked fluid is pumped from the pump chamber 130. Therefore, since the volume of the pump chamber 130 before the fluid is sucked (initial state) does not affect the amount of fluid delivered, the volume of the pump chamber 130 in the initial state can be reduced as much as possible. For this reason, for example, the volume of the pump chamber 130 in the initial state can be made almost zero, so that even when bubbles are mixed in the pump chamber 130, it is avoided that bubbles remain in the pump chamber 130. Can do. As a result, when the diaphragm 116 is returned to its original shape, it can be avoided that the bubbles in the pump chamber 130 are compressed and it is difficult to pressurize the fluid. It is possible to maintain the ability to pump.

  In addition, by reducing the volume of the pump chamber 130 in the initial state as much as possible, the volume ratio between when the volume of the pump chamber 130 increases and when the volume returns to the original can be increased. Thereby, the fluid in the pump chamber 130 can be pumped by a high pressure.

  FIG. 3 is a cross-sectional view showing the structure of a conventional liquid feed pump 300. As shown in FIG. 3A, in the conventional liquid feed pump 300, a pump chamber 330 is formed above the diaphragm 316. The piezoelectric element 314 has a lower end bonded to the bottom of the piezoelectric element case 310 and an upper end bonded to the diaphragm 316. Such a liquid feed pump 300 pressurizes the fluid in the pump chamber 330 by applying a voltage to the piezoelectric element 314 and extending the piezoelectric element 314. Further, when the voltage applied to the piezoelectric element 314 is removed and the piezoelectric element 314 is restored to its original length, fluid is supplied from the inlet side buffer chamber 324 to the pump chamber 330.

  In such a conventional liquid feed pump 300, even if the piezoelectric element 314 is extended to deform the diaphragm 316, a region that cannot be excluded by the diaphragm 316 occurs in the peripheral portion of the pump chamber 330 (FIG. 3B). )). Therefore, if bubbles enter such a portion, it becomes difficult to expel the bubbles no matter how much the diaphragm 316 is deformed. On the other hand, such a portion does not occur in the liquid feed pump 100 of the present embodiment. As a result, it is possible to reliably avoid the bubbles from staying in the pump chamber 130 and the pump performance from deteriorating.

C. Modified example:
In the liquid feed pump 100 of the above-described embodiment, it has been described that the cylindrical piezoelectric element 114 is provided so as to surround the central column 118 (see FIG. 1). However, the piezoelectric element 114 only needs to be able to increase the volume of the pump chamber 130 by extending the base plate 112 away from the diaphragm 116. Therefore, the piezoelectric element 114 is not limited to a cylindrical shape, and for example, the piezoelectric element 114 may be provided as follows. In the modification described below, the same components as those in the above-described embodiment are denoted by the same reference numerals as those in the embodiment, and detailed description thereof is omitted.

  FIG. 4 is an explanatory view showing the structure of a liquid feed pump 100 according to a modification. As illustrated, in the liquid feeding pump 100 according to the modified example, the rectangular parallelepiped piezoelectric elements 114 are provided at a plurality of locations (four locations in the modified example) around the central column 118. Also in the liquid feed pump 100 of such a modification, it is possible to avoid leaving bubbles in the pump chamber 130 by setting the volume of the pump chamber 130 in the initial state to almost zero. In addition, since the piezoelectric elements 114 need only be provided at four locations around the central pillar 118, the amount of piezoelectric elements 114 to be used is smaller than when the cylindrical piezoelectric elements 114 are provided so as to surround the central pillar 118. Can be reduced. As a result, the liquid feed pump 100 can be manufactured at low cost.

  Although various embodiments have been described above, the present invention is not limited to all the above embodiments, and can be implemented in various modes without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 100 ... Liquid feed pump, 110 ... Piezoelectric element case, 110b ... Projection part,
112 ... Bottom plate, 114 ... Piezoelectric element, 116 ... Diaphragm,
118 ... Center pillar 120 ... Flow path block 121 ... Check valve
122: outlet connection pipe, 123: outlet channel, 124: inlet side buffer chamber,
125 ... Inlet connection pipe, 126 ... Inlet flow path, 130 ... Pump chamber,
200 ... Voltage application unit, 300 ... Liquid feed pump, 314 ... Piezoelectric element,
316 ... Diaphragm, 324 ... Inlet side buffer chamber, 330 ... Pump chamber

Claims (3)

A liquid feed pump that deforms a diaphragm constituting a part of the pump chamber and changes the volume of the pump chamber to pump the fluid,
A driving member provided outside the pump chamber and connected to the diaphragm;
A piezoelectric element that deforms the diaphragm via the driving member;
Voltage applying means for applying a voltage to the piezoelectric element,
The driving member has a base part and a column part standing from the base part, and a tip end of the pillar part is connected to the diaphragm,
The liquid feeding pump, which is a piezoelectric element that expands when the voltage is applied and separates the base portion of the driving member from the diaphragm.   The liquid feeding pump according to claim 1, wherein the piezoelectric elements are provided at a plurality of locations around the pillar portion of the driving member.   The liquid feed pump according to claim 1, wherein the piezoelectric element is provided around the pillar portion of the driving member, and is a piezoelectric element having a circular cross section.

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