JP2004162547A - pump - Google Patents

Abstract

A pump is provided which has high output and high reliability corresponding to high load pressure and high frequency driving.
A circular diaphragm (5) arranged at the bottom of a case (7) has an outer peripheral green fixedly supported by the case. A piezoelectric element 6 for moving the diaphragm is arranged on the bottom surface of the diaphragm. The space between the diaphragm and the upper wall of the case is a pump chamber 3, and the inlet channel 1 provided with a check valve 4, which is a fluid resistance element, is directed toward the pump chamber and the pump chamber is operated during pump operation. The outlet channel 2 is open. In this pump, the sum of the combined inertance value of the inlet passage 1 and the inertance value of the check valve 4 is smaller than the combined inertance value of the outlet passage 2.
[Selection diagram] Fig. 1

Description

【００３４】
という関係がほぼ成り立つため、これら流体の体積速度の変化率は、ΔＰ_ｏｕｔとＲ_ｏｕｔ×Ｑ_ｏｕｔとの差をイナータンス値Ｌ_ｏｕｔで割ったものと等しい。
本実施形態のポンプは、図１で示したように出口流路２とポンプ室３とが連通しているため、流体抵抗が小さくなっている。その結果、差圧をΔＰ_ｏｕｔ一定として比較した場合に、連通していないポンプよりも出口流路内の流体体積速度の最大値を大きくし運動量の最大値も大きくすることが可能となる。
【００３５】
そして、一周期分の波形Ｗ３で示されている流体の体積速度を積分した値が、一周期当たりの吐出流体体積となる。
また、逆止弁４を通過する流体の体積速度変化の波形Ｗ４に示すように、入口流路１では、ポンプ室３内圧力が吸入側圧力Ｐ_ｋｙよりも減少すると、その圧力差によって逆止弁４の薄板４１が開き、流体の体積速度が増加し始める。また、ポンプ室３内圧力が上昇し、吸入側圧力Ｐ_ｋｙよりも増加すると、流体の体積速度が減少し始める。そして、逆止弁４の逆止効果によって逆流は防がれている。
【００３６】
ポンプ室３内圧力と吸入側圧力Ｐ_ｋｙとの差圧をΔＰ_ｉｎ、出口流路２での流体抵抗をＲ_ｉｎ、逆止弁４のイナータンスと流路のイナータンスを合わせたイナータンスをＬ_ｉｎ、流体の体積速度をＱ_ｉｎとおくと、入口流路１内の流体でも、
【００３７】
【数２】

【００３８】
という関係がほぼ成り立つため、これら流体体積速度の変化率も、ΔＰ_ｉｎとＲ_ｉｎ×Ｑ_ｉｎとの差を入口流路１のイナータンス値Ｌ_ｉｎで割ったものと等しい。
そして、一周期分の波形Ｗ４で示されている流体の体積速度を積分した値が、一周期当たりの吸入流体体積であり、波形Ｗ３の説明で述べた吐出流体体積と等しい。従って、波形Ｗ４で示される流体の体積速度を、逆止弁４が開いている間に速くすればするほど、吸入流体体積（＝吐出流体体積）を多くできる。
【００３９】
そして、本実施形態のポンプは、入口流路１と薄板４１のイナータンス値の和を出口流路２のイナータンス値よりも小さくしてあるので、入口流路１の流体は、大きな流体速度の変化率で流入し、吸入流体体積（＝吐出流体体積）を増加させることが可能となっている。
【００４０】
次に、本発明に係わるポンプ構造について、具体的な寸法を示しながら説明を加える。
出口流路２は直径φ０．８［ｍｍ］、長さ１５［ｍｍ］とし、入口流路１は逆止弁４近傍の縮径された部分（弁穴４２に等しい部位）の直径をφ０．６［ｍｍ］、長さを０．２［ｍｍ］、残りの拡大された部分の直径をφ２［ｍｍ］長さ２［ｍｍ］とした。
ポンプ内に流す流体は水とした。水の密度は１Ｅ３［ｋｇ／ｍ^３］なので、入口流路１の合成イナータンス値は１．３４Ｅ−５［ａｔｍ ｓ^２／ｃｍ^３］、出口流路２のイナータンス値は２．９８Ｅ−４［ａｔｍ ｓ^２／ｃｍ^３］となる。
【００４１】
薄板４１は、水によって腐食されない材質で製作されることが望ましく、密度約８Ｅ３［ｋｇ／ｍ^３］のＳＵＳの薄板をエッチングにて製作し、ラップ量は０．１５［ｍｍ］とした。
その場合、出口流路２のイナータンス値２．９８Ｅ−４［ａｔｍ ｓ^２／ｃｍ^３］と入口流路１の合成イナータンス値１．３４Ｅ−５［ａｔｍ ｓ^２／ｃｍ^３］との差よりも、薄板４１のイナータンス値が小さくなるように薄板４１の板厚を選定すれば、入口流路の流体が確実に大きな流体速度の変化率で流入し、ポンプ室内に流入する流体体積が多くなる。
【００４２】
また、薄板４１の板厚を１１５［μｍ］以下にすることで、薄板４１のイナータンス値を出口流路２のイナータンス値２．９８Ｅ−４［ａｔｍ ｓ^２／ｃｍ^３］の２５％以下にすることができる。すると、入口流路１の合成イナータンス値と合算しても、出口流路２のイナータンス値の５０％以下となり、入口流路の流体を更に大きな流体速度の変化率でポンプ室内に流入させることができ、ポンプ室内に流入する流体体積が多くなる。
さらに、薄板４１のイナータンス値を出口流路２のイナータンス値２．９８Ｅ−４［ａｔｍ ｓ^２／ｃｍ^３］の１０％以下とすれば、入口流路２内の流体を加速させる際の薄板４１が存在する影響を無視できるレベルとなり好ましい。ちなみに、その条件を満たすためには板厚を４６［μｍ］以下にすると良い。
【００４３】
一方、薄板４１にはポンプ内の圧力が加わるため、その圧力で壊れないようにする必要がある。本実施形態のポンプはポンプ室内圧を高くすると吐出流量を多くできる特性であるため、従来の容積形ポンプと比較して遥かに高いポンプ室内圧で運転される。具体的には図３で説明したように、ポンプ室内圧は絶対圧で２０気圧にもなる。
そして、薄板４１は厚さを１０［μｍ］とすると頻繁に破壊されるが、１５［μｍ］とすると破壊されないことを試験により確認しており、板厚１３［μｍ］近傍で限界応力に達すると考えられる。弁穴４２の面積は０．２８［ｍｍ^２］であるから、この面積の平方根は０．５３［ｍｍ］となり板厚１３［μｍ］の約４０倍の値となっている。
【００４４】
一般的に知られる分布荷重を受ける円板の曲げの理論によると、分布荷重を受ける面積／板厚の２乗が曲げによって発生する応力と比例関係にある。そこで、理論に従い試験結果は一般化して解釈することができる。つまり、開閉される流路の断面積の平方根は、薄板の流路と重なる部分の平均板厚の約４０倍以下にすると薄板は２０気圧に耐えられるようになり、ポンプ室内圧を高くして流量が増大するようにポンプを運転できると言える。
【００４５】
また、本実施例のポンプを長時間連続運転する場合には、薄板４１はポンプ室の圧力変動を何千万回と繰り返し受ける。そのような時には、より応力が緩和するように薄板４１の板厚を厚くすることが必要となる。具体的には、２０［μｍ］以上にすると、長時間運転しても薄板４１は疲労破壊しなくなることを確認した。この時、弁穴面積の平方根は、薄板の流路と重なる部分の平均板厚の約２５倍以下となっている。この結果も先ほどと同様に一般化して解釈できる内容である。以上のように弁穴４２の直径がφ０．６［ｍｍ］である本実施例の場合、薄板４１の少なくとも弁穴４２と重なる部分の板厚は１３［μｍ］以上で１１５［μｍ］以下とすると良い。２０［μｍ］以上で４６［μｍ］以下とするとより好ましい。
【００４６】
本実施例のポンプはアクチュエータに圧電素子を使用し、ダイヤフラム５と変位拡大機構を介さずに接続されているため、ダイヤフラムをｋＨｚオーダーの高い周波数で運転可能である。そのため、薄板４１がこのような高い周波数に追従して、流体抵抗を少なくするのに十分な距離だけ弁穴４２から開けるようにすれば、圧電素子の性能を生かした高い周波数でポンプを駆動でき、吐出流量が増加する。図３で示したように、入り口流路から流体を吸入する際に薄板４１に加わる差圧は１気圧である。弁穴４２の大きさにかかわらず薄板４１の板厚は８０［μｍ］以下とすれば、この差圧によって５［ｋＨｚ］の開閉周波数で１００［μｍ］開くことが可能となり良い。
【００４７】
以上の関係を、弁穴寸法と薄板の板厚との関係でまとめたグラフを図５に示す。グラフ上実線で挟まれた領域内が、薄板のイナータンス値を出口流路２のイナータンス値２．９８Ｅ−４［ａｔｍ ｓ^２／ｃｍ^３］の２５％以下、かつ、弁穴面積の平方根が薄板の板厚の約４０倍以下、更に、板厚が８０［μｍ］以下となる条件を満たす範囲である。そして、グラフ上一点鎖線で挟まれた領域内が、薄板のイナータンス値を出口流路２のイナータンス値２．９８Ｅ−４［ａｔｍ ｓ^２／ｃｍ^３］の１０％以下、かつ、弁穴面積の平方根が薄板の板厚の約２５倍以下、更に、板厚が８０［μｍ］以下となる条件を満たす範囲である。
【００４８】
以上の構成において、ダイヤフラム５の形状は円形に限定するものではない。また、例えばポンプ停止時に万一加えられる過大な負荷圧力からポンプ構成部品を守る目的等で出口流路２に弁要素が配置されていても、少なくともポンプ動作時に出口流路２とポンプ室３とが連通し、流体がポンプ室から出口流路に吐出される方向とその逆方向に自由に移動できる状態となっていれば構わない。また、逆止弁４は、流体の圧力差で開閉する物であれば開閉部材として薄板形状以外のものを用いても良い。また、弁穴４２は円形状以外でも構わない。さらに、ポンプ内に流す流体は油等の水以外のもとしても良い。
【００４９】
さらに、ダイヤフラム５を動かすアクチュエータ６には伸縮するものであれば何を使用しても良いが、本発明のポンプ構造は、アクチュエータとダイヤフラム５とが変位拡大機構を介さずに接続され、ダイヤフラムを高い周波数で運転可能なため、本実施形態のように応答周波数が高い圧電素子６を使用することで、高周波駆動による流量増加ができ、小型高出力なポンプが実現できる。同様に高い周波数特性を有する超磁歪素子を使用しても良い。
【００５０】
【発明の効果】
以上説明したように、本発明のポンプは、開閉部材を具備する流体抵抗要素を入口流路だけに配置すれば良いので、ポンプの信頼性を高めることができる。
また、ピストン或いはダイヤフラムと、それを駆動するアクチュエータとの間には変位拡大機構が配置されておらず、弁に粘性抵抗を利用していないので高周波駆動に対応し、高周波駆動することでポンプの出力を増加することができる。特に、アクチュエータとして圧電素子や超磁歪素子を使用するときには、素子の高い周波数応答性を十分に生かし小型軽量で高出力のポンプを実現できる。
【００５１】
また、請求項２から請求項４に記載した開閉部材と開閉される流路の断面積の関係を満たすことによって、ポンプ室内圧を高くして吐出流量が増大するようにポンプを運転可能となるとともに流体抵抗要素の信頼性が高くなる。また、入口流路の流体を大きな流体速度の変化率でポンプ室内に流入させることができ吐出流量が多くなる。更に、高い周波数に追従して、流体抵抗を少なくするのに十分な距離だけ開閉部材が移動可能となり、高周波駆動時のポンプ効率を向上させることができる。
【図面の簡単な説明】
【図１】本発明に係る実施形態のポンプ構造の縦断面を示す図である。
【図２】本発明に係る実施形態のポンプが具備する流体抵抗要素の上面図である。
【図３】本発明に係る実施形態のポンプ動作時の各状態量を示すグラフである。
【図４】ポンプ室の容積を減少させる時間が長く、ポンプ室内圧が十分に上昇しない状態を示すグラフである。
【図５】本発明に係る実施形態のポンプの弁穴寸法と薄板の板厚との関係を示すグラフである。
【符号の説明】
１：入口流路
２：出口流路
３：ポンプ室
４：逆止弁（流体抵抗要素）
５：ダイヤフラム（可動壁）
６：圧電素子（アクチュエータ）
２０：駆動手段
４１：薄板（開閉部材）
４２：弁穴（開閉される流路）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a positive displacement pump that moves a fluid by changing the volume in a pump chamber by a piston or a diaphragm, and particularly relates to a highly reliable pump having a large output.
[0002]
[Prior art]
Conventional pumps of this type generally have a configuration in which a check valve is mounted between an inlet flow path and an outlet flow path and a pump chamber whose volume can be changed. (For example, see Patent Document 1)
Further, as a pump configuration for generating a flow in one direction by utilizing the viscous resistance of the fluid, a valve is provided in the outlet flow path, and when the valve is opened, the inlet flow path has a larger fluid resistance than the outlet flow path. There is a configuration as described above. (For example, see Patent Document 2)
[0003]
Furthermore, as a pump configuration that improves the reliability of the pump without using a movable part in the valve section, a configuration is provided in which a compression component having a flow path shape in which the pressure drop is different depending on the flow direction in both the inlet flow path and the outlet flow path. There is something. (For example, see Patent Document 3 and Non-Patent Document 1)
[0004]
[Patent Document 1] Japanese Patent Application Laid-Open No. 10-220357 [Patent Document 2] Japanese Patent Application Laid-Open No. 08-312537 [Patent Document 3] Japanese Patent Application Laid-Open No. 08-506874 [Non-patent Document 1] Anders Olsson, An improved valve- Less pump fabric using deep reactive ion etching, 1996 IEEE 9th Internationala 1 Works on Micro E1 Electro Mechanical Systems, p. 479-484
[0005]
[Problems to be solved by the invention]
However, the configuration of Patent Literature 1 requires a check valve for both the inlet flow path and the outlet flow path, and there is a problem that when the fluid passes through two check valves, the pressure loss is large. In addition, there is a risk that the check valve is repeatedly opened and closed, thereby causing a risk of fatigue damage. As the number of check valves increases, the reliability decreases.
[0006]
In the configuration of Patent Document 2, it is necessary to increase the fluid resistance of the inlet-side flow path in order to reduce the backflow generated in the inlet flow path during the pump discharge stroke. Then, in the pump suction stroke, since the fluid is introduced into the pump chamber against the fluid resistance, the suction stroke becomes considerably longer than the discharge stroke. Therefore, the frequency of the discharge suction cycle of the pump is considerably reduced.
[0007]
In a pump that moves a piston or a diaphragm up and down, when the area of the piston or the diaphragm is equal, generally, the higher the frequency of the up and down movement, the larger the flow rate and the higher the output. However, the configuration of Patent Document 2 can drive only at a low frequency as described above, and therefore has a problem that a high-output pump cannot be realized with a small size.
[0008]
The pump disclosed in Patent Document 3 has a configuration in which a net flow rate flows in one direction due to a difference in pressure drop depending on a flow direction of a fluid passing through a compression component. Therefore, the pump reverses as the external pressure (load pressure) on the pump outlet side increases. There is a problem that the flow rate increases and the pump does not operate at a high load pressure. According to Non-Patent Document 1, the maximum load pressure is about 0.760 atm.
[0009]
Therefore, an object of the present invention is to provide a pump having high output and high reliability corresponding to high load pressure and high frequency driving.
[0010]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is an actuator that displaces a movable wall such as a piston or a diaphragm, a driving unit that drives and controls the actuator, and a volume that can be changed by displacement of the movable wall. Pump chamber, an inlet flow path for flowing the working fluid into the pump chamber, and a pump having an outlet flow path for flowing the working fluid from the pump chamber,
The outlet flow path communicates with the pump chamber during a pump operation, the inlet flow path includes a fluid resistance element having an opening / closing member for opening and closing the flow path, and a combined inertance value of the inlet flow path and the opening / closing member. The sum with the inertance value was smaller than the combined inertance value of the outlet channel.
[0011]
According to the first aspect, first, the outlet flow path is communicated with the pump chamber during the operation of the pump, so that the fluid resistance element having the opening / closing member only needs to be disposed only in the inlet flow path, thereby improving the reliability of the pump. Can be. Further, no displacement enlargement mechanism is arranged between the piston or the diaphragm and the actuator for driving the piston or the diaphragm, and viscous resistance is not used as a valve, so that high-frequency driving can be supported.
Further, since the outlet flow path is communicated with the pump chamber during the pump operation, the fluid resistance of the outlet flow path is reduced, and the flow velocity in the outlet flow path can be increased during the volume reduction process of the pump chamber, thereby increasing the momentum of the fluid. . Further, since the sum of the combined inertance value of the inlet flow path and the inertance value of the opening / closing member is smaller than the combined inertance value of the outlet flow path, the momentum of the fluid in the outlet flow path decreases from the inlet flow path side until the momentum of the fluid in the outlet flow path decreases. Many fluids can be introduced into the pump chamber to significantly increase the discharge flow rate.
[0012]
According to a second aspect of the present invention, in the pump according to the first aspect, an inertance value of the opening / closing member is set to 25% or less of a combined inertance value of the outlet passage. By doing so, the effect of the presence of the opening / closing member on the fluid velocity change rate of the fluid in the inlet channel can be further reduced, and the discharge flow rate can be increased.
[0013]
According to a third aspect of the present invention, in the pump according to the first or second aspect, the opening / closing member is a thin plate, and a square root of a cross-sectional area of the flow path to be opened / closed is an average of a portion overlapping the flow path of the thin plate. The thickness was set to 40 times or less of the plate thickness. By doing so, the pump can be operated so as to increase the pump chamber pressure and increase the flow rate.
According to a fourth aspect of the present invention, in the pump according to the third aspect, a square root of a cross-sectional area of the flow path to be opened and closed is set to 25 times or less an average thickness of a portion overlapping the flow path of the thin plate. . In this way, the thin plate does not suffer from fatigue failure even when repeatedly subjected to high pump chamber pressure, and can be a highly reliable pump whose life is greatly extended.
[0014]
According to a fifth aspect of the present invention, in the pump according to the third or fourth aspect, an average plate thickness of a portion of the thin plate that overlaps the flow path to be opened and closed is 80 μm. With this configuration, the thin plate can follow a high switching frequency and move a sufficient distance to reduce the fluid resistance due to the pressure difference between the pump chamber and the suction passage. Therefore, it is possible to configure a pump in which the discharge flow rate does not decrease even when driven at a high frequency.
[0015]
Further, as described in claim 7, in the pump according to any one of claims 1 to 6, the actuator is preferably a piezoelectric element. Further, as described in claim 8, in the pump according to any one of claims 1 to 7, the actuator is preferably a giant magnetostrictive element. This is because the pump of the present invention can be driven at a high frequency, and if a high-frequency responsive actuator such as a piezoelectric element or a giant magnetostrictive element is used as the actuator, a small, lightweight, and high-output pump can be realized. is there.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the structure of the pump according to the present invention will be described with reference to FIG.
FIG. 1 shows a longitudinal section of the pump of the present invention. A circular diaphragm 5 is arranged at the bottom of a cylindrical case 7. The outer peripheral green of the diaphragm 5 is fixedly supported by the case 7 and is elastically deformable. On the bottom surface of the diaphragm 5, a piezoelectric element 6 that expands and contracts in the vertical direction in the drawing is arranged as an actuator for moving the diaphragm 5.
[0017]
The narrow space between the diaphragm 5 and the upper wall of the case 7 is the pump chamber 3, the inlet flow path 1 provided with the check valve 4 which is a fluid resistance element toward the pump chamber 3, and the pump chamber 3 is always in operation. An outlet passage 2 which is a pipe with a small hole communicating with the pump chamber is open. A part of the outer periphery of the component constituting the inlet flow path 1 serves as an inlet connection pipe 8 for connecting to an external element (not shown) of the pump. Further, a part of the outer periphery of the component constituting the outlet flow path 2 serves as an outlet connection pipe 9 for connecting to an external element (not shown) of the pump. In addition, both the inlet channel and the outlet channel have rounded portions 15a and 15b in which the inlet side of the working fluid is rounded.
[0018]
Here, the details of the check valve 4 will be described with reference to FIG. In FIG. 2, a circle shown by a broken line is a valve hole 42 which is a flow path to be opened and closed, and a tongue-shaped thing shown by a thick solid line is a thin plate 41 which is an opening and closing member. The check valve 4 is configured such that the thin plate 41 overlaps the valve hole 42, and the base of the tongue-shaped thin plate 41 is fixed to a member having the valve hole 42 opened away from the valve hole 42. The distance from the center of the valve hole 42 to the outer periphery of the thin plate 41 is longer than the distance from the center of the valve hole 42 to the outer periphery of the valve hole 42 even at the shortest point. This difference in distance is called the lap amount. The thin plate 41 is separated from the valve hole 42 and the fluid passes through the valve hole 42 due to the pressure difference between the surface of the thin plate 41 on the valve hole side and the surface on the opposite side.
[0019]
Here, the inertance value L of the flow path is defined. When the cross-sectional area of the flow path is S, the length of the flow path is 1, and the density of the working fluid is ρ, it is given by L = ρ × 1 / S. When the pressure difference in the flow path is ΔP and the flow rate in the flow path is Q, by deforming the equation of motion of the fluid in the flow path using the inertance value L, the relation ΔP = L × dQ / dt is derived. It is.
[0020]
That is, the inertance value L indicates the degree of influence of the unit pressure on the time change of the flow rate. The larger the inertance value L, the smaller the time change of the flow rate. The smaller the inertance value L, the larger the time change of the flow rate.
In addition, the combined inertance value for the parallel connection of a plurality of flow paths and the series connection of a plurality of flow paths having different shapes is obtained by combining the inertance values of the individual flow paths in the same manner as the parallel connection and the serial connection of the inductance in an electric circuit. It is sufficient to calculate it.
[0021]
In addition, the inlet flow path referred to here is a flow path from the inside of the pump chamber 3 to the end face of the inlet connection pipe 8 on the fluid inflow side. However, when the pulsation absorbing means is connected in the middle of the pipe, it refers to the flow path from the inside of the pump chamber 3 to the connection with the pulsation absorbing means. Further, when the inlet flow paths 1 of a plurality of pumps are merged, it refers to the flow path from the inside of the pump chamber 3 to the merged portion. The same applies to the outlet flow path.
[0022]
Next, the inertance value of the opening / closing member is defined. The inertance value of the opening / closing member is substantially related to the mass of the opening / closing member and the cross-sectional area of the flow path closed by the opening / closing member,
Inertance value of the opening / closing member = mass of the opening / closing member / square of the cross-sectional area of the flow path closed by the opening / closing member. The inertance value of the opening / closing member determines the degree of influence of the unit pressure on the time change of the flow rate, similarly to the inertance of the flow path, while the opening / closing member is opened from a state in which the flow path is completely closed and the flow rate is small. It can be considered that the time change of the flow rate is smaller as the inertance value is larger, and the time change of the flow rate is larger as the inertance value is smaller.
[0023]
In a valve in which a part of the opening and closing member shown in FIG. 2 is fixed to a member having a valve hole, the mass of the opening and closing member is determined by the distance from the center of the valve hole to the outer periphery of the valve hole 42. The mass of the thin plate 41 in an area drawn with a diameter to which the lap amount is added (an area shown by hatching in FIG. 2) is used. In other types of valves in which the opening / closing member is not fixed to a member having a valve hole, the mass of the opening / closing member itself is used as the mass of the opening / closing member.
[0024]
Next, an internal state when the pump according to the present invention is operated will be described with reference to FIGS.
FIG. 4 shows waveforms when the internal pressure of the pump chamber does not rise sufficiently and the pump cannot be operated well (W1: diaphragm displacement waveform during pump operation, W2: internal pressure waveform of the pump chamber). In the waveform W1, a region where the slope of the waveform is positive is a process in which the volume of the pump chamber 3 is reduced due to the extension of the piezoelectric element 6. Although not shown, in the region where the inclination is negative, the piezoelectric element 6 contracts and the volume of the pump chamber 3 increases.
[0025]
In the operation state of FIG. 4, at the timing of starting the pump chamber volume increasing stroke (not shown), the pump chamber pressure is equal to the load pressure P _fu , and the diaphragm displacement is reduced to increase the volume of the pump chamber. Even if the pump chamber pressure decreases, a large amount of diaphragm displacement is required to lower the pump chamber pressure below the suction side pressure, and pump performance is greatly reduced. In some cases, the internal pressure of the pump chamber does not drop below the suction side pressure, and the flow rate in the discharge direction and the flow rate flowing backward in the pump chamber direction are equal in the outlet flow path without opening the suction valve, thus functioning as a pump. It will not be in the state.
As described above, the operation principle of the pump having the structure of the present embodiment is different from that of the conventional positive displacement pump which always discharges the excluded volume by the diaphragm.
[0026]
On the other hand, FIG. 3 shows a waveform W1 of the displacement of the diaphragm 5, a waveform W2 of the internal pressure of the pump chamber 3, and a volume velocity of the fluid passing through the outlet flow path 2 (disconnection of the outlet pipe) when the pump is operated normally. Area × fluid flow rate, in this case equal to the flow rate), and a waveform W4 of the volume velocity of the fluid passing through the check valve 4. Further, the load pressure P _fu shown in FIG. 3 is a fluid pressure at a position downstream of the outlet flow rate 2, and the suction side pressure P _ky is a fluid pressure upstream of the inlet flow path 1.
[0027]
As shown in the waveform W1 of the displacement of the diaphragm 5, the area where the slope of the waveform is positive is the process in which the volume of the pump chamber 3 is reduced due to the extension of the piezoelectric element 6. The region where the slope of the waveform is negative is a process in which the volume of the pump chamber 3 is increasing due to the contraction of the piezoelectric element 6.
The flat waveform section displaced by about 4.5 μm is the position of the diaphragm 5 where the volume of the pump chamber 3 becomes minimum at the top dead center of the diaphragm 5.
[0028]
As shown by the waveform W2 of the change in the internal pressure of the pump chamber 3, when the process of reducing the volume of the pump chamber 3 starts, the internal pressure of the pump chamber 3 starts increasing. Then, before the process of reducing the volume of the pump chamber 3 ends, the internal pressure of the pump chamber 3 reaches a maximum value of 20 atm at an absolute pressure much higher than the load pressure and starts to decrease. The maximum point of the internal pressure is a point at which the volume velocity of the rejected fluid by the diaphragm 5 becomes equal to the volume velocity of the fluid in the outlet channel 2 shown by the waveform W3.
[0029]
The reason is that before this time,
Volume velocity of rejected fluid-Volume velocity of fluid in outlet channel 2> 0
Therefore, the fluid in the pump chamber 3 is compressed correspondingly, the pressure in the pump chamber 3 increases, and after this time,
Volume velocity of rejected fluid-Volume velocity of fluid in outlet channel 2 <0
This is because the amount of compression of the fluid in the pump chamber 3 decreases accordingly, and the pressure in the pump chamber 3 drops.
[0030]
The pressure in the pump chamber 3 is as follows: ΔV is a volume change of the fluid in the pump chamber 3 at each time.
ΔV = displaced fluid volume by the diaphragm + inhaled fluid volume−changes according to the relationship between the discharged fluid volume and the compressibility of the fluid. Therefore, even in the process where the volume of the pump chamber 3 is decreasing, the pressure in the pump chamber 3 may be lower than the load pressure _Pfu .
[0031]
Further, in the case of FIG. 3, the pressure in the pump chamber 3 becomes lower than the suction side pressure P _ky and becomes 0 atm due to aeration or cavitation which gasifies the components dissolved in the working fluid into gas bubbles. Saturated nearer. However, when the entire flow path system including the pump is pressurized and the suction side pressure _Pky is sufficiently high, aeration and cavitation may not occur.
[0032]
Further, as shown in the waveform W3 of the fluid volume velocity in the outlet flow path 2, in the outlet flow path 2, the period in which the pressure in the pump chamber 3 is larger than the load pressure _Pfu is almost the period during which the volume velocity of the fluid increases. It has become. When the pressure in the pump chamber 3 becomes lower than the load pressure _Pfu , the volume velocity of the fluid in the outlet channel 2 also starts to decrease.
If the pressure difference between the pressure in the pump chamber 3 and the load pressure P _fu is ΔP _out , the fluid resistance in the outlet channel 2 is R _out , the inertance is L _out , and the volume velocity of the fluid is Q _out , the outlet channel 2 The fluid inside is
[0033]
(Equation 1)

[0034]
, The rate of change in volume velocity of these fluids is equal to the difference between ΔP _out and R _out × Q _out divided by the inertance value L _out .
In the pump of the present embodiment, as shown in FIG. 1, the outlet channel 2 and the pump chamber 3 communicate with each other, so that the fluid resistance is reduced. As a result, it is possible to increase the maximum value of the fluid volume velocity in the outlet flow path and the maximum value of the momentum as compared with a pump that is not in communication, when comparing the differential pressure with a constant ΔP _out .
[0035]
Then, a value obtained by integrating the volume velocity of the fluid shown by the waveform W3 for one cycle is the discharge fluid volume per cycle.
Further, as shown in the waveform W4 of the change in volume velocity of the fluid passing through the check valve 4, when the pressure in the pump chamber 3 becomes lower than the suction side pressure P _ky in the inlet flow path 1, the check is made due to the pressure difference. The lamella 41 of the valve 4 opens and the volume velocity of the fluid starts to increase. When the pressure in the pump chamber 3 rises and becomes higher than the suction side pressure _Pky , the volume velocity of the fluid starts to decrease. The check valve 4 prevents the check valve from flowing backward.
[0036]
The differential pressure between the pressure in the pump chamber 3 and the suction-side pressure P _ky is ΔP _in , the fluid resistance _in the outlet flow path 2 is R _in , the inertance of the check valve 4 and the inertance of the flow path are L _in , Assuming that the volume velocity of the fluid is Q _in , even the fluid in the inlet channel 1
[0037]
(Equation 2)

[0038]
, The rate of change of the fluid volume velocity is also equal to the difference between ΔP _in and R _in × Q _in divided by the inertance value L _in of the inlet flow path 1.
The value obtained by integrating the volume velocity of the fluid shown by the waveform W4 for one cycle is the suction fluid volume per cycle, and is equal to the discharge fluid volume described in the description of the waveform W3. Therefore, as the volume velocity of the fluid indicated by the waveform W4 is increased while the check valve 4 is open, the suction fluid volume (= discharge fluid volume) can be increased.
[0039]
In the pump of the present embodiment, the sum of the inertance values of the inlet flow path 1 and the thin plate 41 is smaller than the inertance value of the outlet flow path 2. And the suction fluid volume (= discharge fluid volume) can be increased.
[0040]
Next, the pump structure according to the present invention will be described while showing specific dimensions.
The outlet channel 2 has a diameter of φ 0.8 [mm] and a length of 15 [mm], and the inlet channel 1 has a diameter of a reduced diameter portion (a portion equivalent to the valve hole 42) near the check valve 4 of φ 0. 6 [mm], the length was 0.2 [mm], and the diameter of the remaining enlarged portion was φ2 [mm] and the length was 2 [mm].
The fluid flowing in the pump was water. Since the density of water is 1E3 [kg / m ³ ], the synthetic inertance value of the inlet channel 1 is 1.34E-5 [atms s ² / cm ³ ], and the inertance value of the outlet channel 2 is 2.98E-4 [ atm s ² / cm ³ ].
[0041]
The thin plate 41 is desirably made of a material that is not corroded by water. A SUS thin plate having a density of about 8E3 [kg / m ³ ] is manufactured by etching, and the lap amount is 0.15 [mm].
In this case, than the difference between the inertance value 2.98E-4 in the outlet channel ^{2 [atm s 2 / cm 3} ] and combined inertance value 1.34E-5 of the inlet channel ^{1 [atm s 2 / cm 3} ] If the thickness of the thin plate 41 is selected so that the inertance value of the thin plate 41 becomes small, the fluid in the inlet flow path surely flows at a large rate of change of the fluid velocity, and the volume of fluid flowing into the pump chamber increases.
[0042]
Further, by setting the thickness of the thin plate 41 to 115 [μm] or less, the inertance value of the thin plate 41 is set to 25% or less of the inertance value of the outlet channel 2.98E-4 [atms s ² / cm ³ ]. be able to. Then, even if the sum of the inertance value of the inlet flow path 1 and the combined inertance value is 50% or less of the inertance value of the outlet flow path 2, the fluid in the inlet flow path can flow into the pump chamber at a larger fluid velocity change rate. As a result, the volume of fluid flowing into the pump chamber increases.
Further, if the inertance value of the sheet 41 and more than 10% of the inertance value 2.98E-4 in the outlet channel ^{2 [atm s 2 / cm 3} ], the thin plate 41 for accelerating the fluid in the inlet flow path 2 Is at a level at which the influence of the presence of can be ignored. Incidentally, in order to satisfy the condition, the plate thickness is preferably set to 46 [μm] or less.
[0043]
On the other hand, since the pressure in the pump is applied to the thin plate 41, it is necessary to prevent the thin plate 41 from being broken by the pressure. Since the pump of this embodiment has a characteristic that the discharge flow rate can be increased by increasing the pump chamber pressure, the pump is operated at a much higher pump chamber pressure than a conventional positive displacement pump. Specifically, as described in FIG. 3, the pump chamber pressure becomes as high as 20 atm in absolute pressure.
The thin plate 41 is frequently broken when the thickness is set to 10 [μm], but it is confirmed by a test that the thin plate 41 is not broken when the thickness is set to 15 [μm]. It is thought that. Since the area of the valve hole 42 is 0.28 [mm ² ], the square root of this area is 0.53 [mm], which is about 40 times the plate thickness 13 [μm].
[0044]
According to a generally known theory of bending a disk subjected to a distributed load, the square of the area / plate thickness subjected to the distributed load is proportional to the stress generated by bending. Therefore, the test results can be generalized and interpreted according to the theory. In other words, when the square root of the cross-sectional area of the flow path to be opened and closed is set to be about 40 times or less the average thickness of the portion overlapping the flow path of the thin plate, the thin plate can withstand 20 atm, and the pump chamber pressure is increased. It can be said that the pump can be operated so that the flow rate increases.
[0045]
Further, when the pump of this embodiment is operated continuously for a long time, the thin plate 41 repeatedly receives tens of millions of pressure fluctuations in the pump chamber. In such a case, it is necessary to increase the thickness of the thin plate 41 so that the stress is further reduced. Specifically, it was confirmed that when the thickness was set to 20 [μm] or more, the thin plate 41 did not break due to fatigue even after a long operation. At this time, the square root of the valve hole area is about 25 times or less the average plate thickness of the portion overlapping the flow path of the thin plate. This result can be generalized and interpreted similarly to the above. As described above, in the case of the present embodiment in which the diameter of the valve hole 42 is φ0.6 [mm], the plate thickness of at least the portion of the thin plate 41 that overlaps the valve hole 42 is not less than 13 [μm] and not more than 115 [μm]. Good. It is more preferable that the thickness be 20 μm or more and 46 μm or less.
[0046]
Since the pump of this embodiment uses a piezoelectric element as an actuator and is connected to the diaphragm 5 without passing through a displacement enlarging mechanism, the diaphragm can be operated at a high frequency on the order of kHz. Therefore, if the thin plate 41 follows such a high frequency and is opened from the valve hole 42 a sufficient distance to reduce the fluid resistance, the pump can be driven at a high frequency utilizing the performance of the piezoelectric element. As a result, the discharge flow rate increases. As shown in FIG. 3, the differential pressure applied to the thin plate 41 when sucking the fluid from the inlet channel is 1 atm. If the thickness of the thin plate 41 is 80 [μm] or less regardless of the size of the valve hole 42, it is possible to open 100 [μm] at an opening / closing frequency of 5 [kHz] by this differential pressure.
[0047]
FIG. 5 is a graph summarizing the above relationship in the relationship between the valve hole size and the thickness of the thin plate. The region between the graph on the solid line, 25% or less of the inertance value of the thin inertance value 2.98E-4 in the outlet channel ^{2 [atm s 2 / cm 3} ], and the square root of the valve hole area thin This is a range that satisfies the condition that the plate thickness is about 40 times or less and the plate thickness is 80 μm or less. In the area between the dashed lines on the graph, the inertance value of the thin plate is set to 10% or less of the inertance value 2.98E-4 [atms s ² / cm ³ ] of the outlet channel 2 and the valve hole area. The square root is within a range that satisfies the condition that the thickness is about 25 times or less the thickness of the thin plate, and further, the thickness is 80 μm or less.
[0048]
In the above configuration, the shape of the diaphragm 5 is not limited to a circle. Further, for example, even if a valve element is arranged in the outlet flow path 2 for the purpose of protecting the pump components from an excessive load pressure applied when the pump is stopped, at least during the pump operation, the outlet flow path 2 and the pump chamber 3 And the fluid can be freely moved in the direction opposite to the direction in which the fluid is discharged from the pump chamber to the outlet flow path. The check valve 4 may be a member other than a thin plate as the open / close member as long as it can be opened and closed by a pressure difference of the fluid. Further, the valve hole 42 may have a shape other than a circular shape. Further, the fluid flowing in the pump may be other than water such as oil.
[0049]
Further, as long as the actuator 6 for moving the diaphragm 5 can be used as long as it expands and contracts, the pump structure of the present invention connects the actuator and the diaphragm 5 without passing through the displacement enlarging mechanism. Since the operation can be performed at a high frequency, the flow rate can be increased by high-frequency driving by using the piezoelectric element 6 having a high response frequency as in the present embodiment, and a small and high-output pump can be realized. Similarly, a giant magnetostrictive element having high frequency characteristics may be used.
[0050]
【The invention's effect】
As described above, in the pump of the present invention, the fluid resistance element having the opening / closing member may be disposed only in the inlet channel, so that the reliability of the pump can be improved.
In addition, there is no displacement magnifying mechanism between the piston or diaphragm and the actuator that drives it, and the valve does not use viscous resistance. Output can be increased. In particular, when a piezoelectric element or a giant magnetostrictive element is used as an actuator, a small, lightweight, high-output pump can be realized by making full use of the high frequency response of the element.
[0051]
Further, by satisfying the relationship of the cross-sectional area of the opening / closing member and the flow path to be opened / closed, the pump can be operated so as to increase the pump chamber pressure and increase the discharge flow rate. At the same time, the reliability of the fluid resistance element increases. Further, the fluid in the inlet channel can be caused to flow into the pump chamber at a large rate of change in fluid velocity, and the discharge flow rate increases. Further, following the high frequency, the opening / closing member can be moved by a distance sufficient to reduce the fluid resistance, and the pump efficiency at the time of high frequency driving can be improved.
[Brief description of the drawings]
FIG. 1 is a view showing a vertical section of a pump structure according to an embodiment of the present invention.
FIG. 2 is a top view of a fluid resistance element included in the pump according to the embodiment of the present invention.
FIG. 3 is a graph showing each state quantity during a pump operation of the embodiment according to the present invention.
FIG. 4 is a graph showing a state where the time for reducing the volume of the pump chamber is long and the pressure in the pump chamber is not sufficiently increased.
FIG. 5 is a graph showing a relationship between a valve hole size and a thin plate thickness of the pump according to the embodiment of the present invention.
[Explanation of symbols]
1: Inlet channel 2: Outlet channel 3: Pump chamber 4: Check valve (fluid resistance element)
5: Diaphragm (movable wall)
6: Piezoelectric element (actuator)
20: drive means 41: thin plate (opening / closing member)
42: Valve hole (flow path to be opened and closed)

Claims (7)

An actuator for displacing a movable wall such as a piston or a diaphragm, a driving means for driving and controlling the actuator, a pump chamber whose volume can be changed by displacement of the movable wall, and an inlet flow path for flowing a working fluid into the pump chamber And a pump having an outlet flow path for allowing a working fluid to flow out of the pump chamber,
The outlet flow path communicates with the pump chamber at the time of a pump operation, the inlet flow path includes a fluid resistance element having an opening / closing member that opens and closes the flow path, and a combined inertance value of the inlet flow path and the opening / closing member. A pump characterized in that a sum with an inertance value is smaller than a combined inertance value of the outlet flow path. The pump according to claim 1, wherein an inertance value of the opening / closing member is 25% or less of a combined inertance value of the outlet flow path. The said opening-and-closing member is a thin plate, The square root of the cross-sectional area of the said flow path opened and closed is 40 times or less of the average board thickness of the part which overlaps the flow path in the said thin plate, The Claim 1 or 2 characterized by the above-mentioned. The pump according to 1. 4. The pump according to claim 3, wherein a cross-sectional area of the flow path to be opened and closed is not more than 25 times an average plate thickness of a portion of the thin plate overlapping the flow path to be opened and closed. 5. The pump according to claim 3, wherein an average plate thickness of a portion of the thin plate overlapping the flow path to be opened and closed is 80 μm or less. 6. The pump according to claim 1, wherein the actuator is a piezoelectric element. The pump according to any one of claims 1 to 5, wherein the actuator is a giant magnetostrictive element.

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