JP5982117B2 - Micro diaphragm pump - Google Patents

Description

  The present invention relates to a micro-diaphragm pump formed by laminating a thin film having a pattern such as a valve plate or a valve seat, or a thin film to be a diaphragm, and bonding them together.

In recent years, the spread and commercialization of fuel cell systems are expected as a distributed energy plant for home use (for detached houses). This type of fuel cell requires a pump for supplying fuel gas, liquid fuel, water supplied to the reformer, hydrogen produced by the reformer, and the like to the fuel cell itself. Carbon monoxide (CO) is produced during reforming to extract the necessary hydrogen (H ₂ ) from the fuel, but this carbon monoxide adversely affects the performance of the battery catalyst, so it is selected to reduce the carbon monoxide concentration. Control of the flow rate of oxidizing air is also required at the same time. Furthermore, analytical devices and medical care (medicine, clinical trials, etc.) require the supply of very small amounts of gas or liquid. Furthermore, a pump for releasing and cooling the heat generated with the performance improvement of the electronic device is also required.

  Conventionally, various micropumps used for such applications have been proposed. As a general pump, a centrifugal type, a volume rotary type, a volume reciprocating type, and the like are well known. The volume reciprocating type has features such as discharge of minute flow rate and good lightweight accuracy. Especially the diaphragm type is suitable for downsizing, so medical equipment that can be implanted in the body, small analytical equipment, office equipment, etc. Has been applied.

  Patent Documents 1 to 4 disclose diaphragm type micropumps driven by piezoelectric elements. In this disclosed pump, a diaphragm and a frame surrounding the diaphragm are integrally formed by etching a Si (silicon) substrate, and a pump chamber whose pressure is changed by vibration of the diaphragm is formed.

  Here, a revenue valve and a discharge valve are arranged in the pump chamber so as to face the diaphragm, and the pressure of the pump chamber is changed by vibrating the diaphragm by a piezoelectric element (piezo element) attached to the other surface of the diaphragm. The fluid is sucked into the pump chamber from the suction valve and discharged from the discharge valve.

JP 10-299659 A JP 05-001669 A JP 2007-120399 A USP62626166

  However, according to the research by the inventors, it is apparent that there is a problem that the pump efficiency (discharge efficiency) is lowered when the volume (V0) of the pump chamber is larger than the volume change due to one reciprocation of the diaphragm. Became. That is, if the change in the volume occupied by the diaphragm (exclusion volume Va) due to the diaphragm vibration in the pump chamber is small, the dead volume (Vd = V0−Va, unnecessary volume) that is the volume of the portion not occupied by the diaphragm increases. This is because the compression ratio becomes small.

For example, when the fluid to be sent is compressible (a gas or a gas containing a gas), the reduction in efficiency is remarkable. If bubbles are mixed when the fluid to be sucked is a liquid, these bubbles enter the pump chamber together with the liquid. However, if the pump compression ratio is small, the bubbles in the pump chamber cannot be discharged and the pump can function. no or (i.e. self吸性decreases), a problem that the discharge amount of the liquid becomes inaccurate results. That is, the property (referred to as bubble resistance) that does not reduce the pump function with respect to the mixing of bubbles is low and the reliability is lowered.

For this reason, it is difficult or impossible to use for compressible gas. Pump miniaturization of further reducing the area of the diaphragm, for to increase the suction force and ejection force of the fluid when achieving micronized is difficult and miniaturized, a problem that is bound by micronization.

The present invention has been made in view of such circumstances, and by increasing the compression ratio by reducing the volume of the diaphragm (dead volume, V0-Va) when the diaphragm is displaced to the pump chamber side , the pump chamber It is possible to discharge the air bubbles that enter the pump, improve the self-priming property and bubble resistance of the pump, increase the pump efficiency (discharge efficiency) and improve the fluid flow control accuracy even if the external dimensions are reduced. Further, it is an object to provide a highly reliable micro diaphragm pump by increasing suction force and discharge force.

According to the present invention, a first object is to form a pump chamber opposite to the suction valve and the discharge valve by a diaphragm fixed to one side of the suction valve and the discharge valve via a frame body, and to vibrate the vibration of the diaphragm. A micro diaphragm pump for guiding fluid from the suction valve to the discharge valve,
The frame is formed of a laminate comprising a plurality of thin plate opening surrounding the pump chamber is formed, the opening diameter of the opening is changed by being close to the curved shape due to the displacement to the pump chamber side of the diaphragm It is achieved by a micro-diaphragm pump characterized in that

According to the present invention, the frame of the pump chamber is formed by laminating a plurality of thin plates, and an opening whose opening diameter is changed so as to be close to a curved surface shape corresponding to the displacement of the diaphragm is formed on the thin plate. The volume (dead volume V0-Va) when the diaphragm is displaced toward the diaphragm chamber can be reduced. For this reason, the compression ratio can be increased, so it can be used for compressible fluids (liquids containing gas), and even if the external dimensions and pump chamber volume are extremely small, the pump efficiency (discharge efficiency) is increased, and the fluid The flow rate control accuracy can be improved.

That is, it increases the compression ratio, even if the bubble in the liquid fluid is not contaminated by reducing the diaphragm it is possible to generate a predetermined ejection amount and the ejection pressure, improve self吸性and bubble tolerance of the pump can do. Further miniaturization of the pump, can be micro-reduction.

The perspective view of the micro diaphragm pump which is one Example of this invention Similarly exploded perspective view Enlarged side sectional view for showing the same laminated structure Partially enlarged exploded perspective view showing the same laminated state Conceptual diagram for explaining the compression ratio of the diaphragm chamber

  The optimal part for the frame of the pump chamber is a laminate of thin metal plates (Claim 2). For example, a thin plate such as stainless steel can be used. In this case, it is not necessary to use relatively expensive silicon and it is inexpensive. The thin plate may be a material other than metal, for example, a ceramic thin plate, a glass thin plate, a silicon thin plate, a hard resin thin plate, or the like, and one that does not corrode by the fluid used can be used. Here, the thin plate includes a foil.

  The opening diameter of each thin plate is preferably changed stepwise along the displacement curved surface shape of the diaphragm, but the opening diameters of partially adjacent thin plates may be the same. In addition, in order to laminate and bond thin stainless plates, solder with high Sn (tin) concentration or silver alloy solder plating such as Sn-Ag is used in terms of wettability and soldering strength to stainless steel. be able to. Various methods such as adhesives and metal diffusion bonding can also be used.

  The outer shape of the pump can be a quadrangle in plan view, and the pump chamber can be a circle. In this case, when this pump is mounted on an electronic board or the like together with the electronic component, a useless gap formed between the pump having a rectangular outer shape and the other electronic component can be reduced to increase the mounting density.

  A piezoelectric element (piezo element) is suitable as the driving element held in the diaphragm. For example, it is possible to use a sintered body of a piezoelectric material that includes zircon / lead titanate (PZT) and is collectively called PZT, which is bonded to a diaphragm and polarized by applying an electric field. If the second frame surrounding the drive element is fixed to the periphery of the diaphragm, the movable range (movable space) of the drive element and the diaphragm can be secured inside the second frame, and this pump When mounted on a substrate or the like, adjacent components do not come into contact with each other and hinder the pump operation.

  1-3, the code | symbol 10 has shown one Example of the micro diaphragm pump based on this invention. The pump 10 is a multi-layered joining of a plurality of thin metal plates made of stainless steel and a frame, that is, a metal thin plate or the like is aligned and laminated, and is a quadrangle having a side of about 7 to 10 mm. The structure of the pump 10 is as described in detail in Japanese Patent Application No. 2010-130304 by the same applicant.

  2 and 3, as shown in FIGS. 2 and 3, the valve plate 14 and the channel opening 16 are formed by etching or press punching on a stainless steel plate having a thickness of 0.01 mm (10 microns), for example. is there. Here, the valve plate 14 can be moved up and down by being held by a support arm that extends while bending toward the inner diameter side from an opening having substantially the same diameter as the flow path opening 16.

  Reference numeral 18 denotes a valve seat, which is formed, for example, by etching or press punching the valve seat 20 and the valve stopper 22 on a stainless steel plate having a thickness of 0.05 mm. The valve stopper 22 has an annular portion 22a and three flow passages 22b divided in the circumferential direction around the annular portion 22a (FIG. 3). The annular portion 22a faces the valve seat 20 via the valve plate 14 in a state where the pump 10 is assembled as will be described later.

  The valve plate sheet 12 and the valve seat sheet 18 processed in this way are prepared two by two, the valve plate sheets 12 and 12 are stacked as shown in FIGS. 2 and 3, and the valve seat sheets 18 and 18 are placed on both sides thereof. Multi-layer joining is performed. For example, diffusion bonding (bonding by heating and pressing in vacuum) is performed. At this time, as is apparent from FIG. 2, the valve plate sheets 12 and 12 are turned upside down with the left and right sides reversed (rotated 180 degrees). For this reason, the valve plate 14 and the flow path opening 16 of the valve plate sheet 12 are formed at positions that overlap with the valve seat 20 and the valve stopper 22 of the valve seat 18 when the left and right sides of the valve plate sheet 12 are reversed or turned over. . As a result, the laminated body (preliminary laminated body) 24 is formed with the suction valve 26 and the discharge valve 28 shown in FIG.

  2 and 3, reference numeral 32 denotes a base plate. The base plate 32 is, for example, a stainless steel plate having a thickness of 0.4 mm, and a flow path 32a serving as a suction port facing the valve seat 20 of the suction valve 26 and a valve stopper 22 (flow path 22b) of the discharge valve 28. A flow path 32b is formed as a discharge port opposite to (FIG. 3). These flow paths 32 a and 32 b are laminated on the lower surface of the preliminary laminated body 24.

Reference numeral 34 denotes a first frame corresponding to the frame of the present invention. The outer shape is the same as that of the base plate 32, and four stainless thin plates 34a to 34d having a thickness of 0.005 mm are laminated to have a thickness of about 0.02 mm. It is the thickness of. The stainless steel plates 34a to 34d are very thin and may be in the form of a metal foil. Each of the stainless steel thin plates 34a to 34d is formed with a circular opening having a different opening diameter by etching or punching, and the diameter of each opening is stepped into a curved shape when the diaphragm 36 is curved toward the diaphragm chamber 40 described later. It is set to approach closely. These openings surround the suction valve 26 and the discharge valve 28. In FIG. 2, the openings of the thin plates 34 a to 34 d are drawn to have the same diameter for the convenience of drawing, but in actuality, they change stepwise (stepwise) as shown in FIGS. 3 and 4. .

  Reference numeral 36 denotes a diaphragm, which is a thin stainless steel plate having a thickness of 0.05 mm. This also has the same outer shape as the base plate 32. Reference numeral 38 denotes a second frame, for example, a stainless steel plate having a thickness of 0.04 mm. The outer shape of the second frame 38 is the same as that of the base plate 32.

  The preliminary laminate 24 has a base plate 32 on the lower surface and a frame 34, a diaphragm 36, and a second frame 38 sequentially stacked on the upper surface, and are multilayered and joined while being pressurized. For example, diffusion bonding is performed. As a result, a pump chamber (pressure chamber) 40 is formed between the diaphragm 36 and the upper valve seat 18 facing the diaphragm 36.

  When the multi-layered joining of a large number of thin metal plates is performed as described above, PZT 42 that is a sheet-like piezoelectric element is then attached to the diaphragm 36 from above the second frame 38 by the adhesive sheet 44. If this PZT 42 is not polarized, it is polarized in an electric field. The wiring connected to the electrode of the PZT 42 is guided upward and connected to a drive circuit (not shown).

  In this embodiment, the flow path (suction port) 32a and the flow path (discharge port) 32b of the base plate 32 are connected to a fluid supply path and a flow path (both not shown), respectively, and the drive circuit of the PZT 42 is operated. Use. The diaphragm 36 is vibrated up and down by the operation of the PZT 42, and the volume of the pump chamber 40 is changed by this vibration. When the pump chamber 40 has a negative pressure due to this vibration, the valve plate 14 of the suction valve 26 moves away from the valve seat 20 and the suction valve 26 opens, and the valve plate 14 of the discharge valve 28 contacts the valve seat 20 and the discharge valve 28 closes. As a result, new fluid is sucked from the suction valve 26. When the diaphragm 36 pressurizes the pump chamber 40, the suction valve 26 is closed, the discharge valve 28 is opened, and the fluid is discharged from the pump chamber 40 through the discharge valve 28.

  Next, the frame 34 will be described. FIG. 5 shows a simplified structure for explaining the compression ratio due to vibrations of the pump chamber 40 and the diaphragm 36. Here, the shape of the pump chamber 40 in a circular shape is more than that in a square shape. The increase in the compression ratio will be described. In the square pump chamber 40 having a side of 2r in FIG. 5, the volume V1 is 2r × 2r × t (t is height). In the circular diaphragm chamber 40 having a diameter of 2r, the volume V2 is π × r × r × t.

  On the other hand, the dead volume Vd, which is a volume that does not change due to the vibration of the diaphragm 36, is Vd1 = V1-Va for a square and Vd2 = V2-Va for a circle. Here, Va is the volume occupied by the diaphragm 36 at the maximum amplitude downward of the diaphragm 36. The variable volume (exclusion volume) Ve of the pump chamber 40 is Ve = 2Va.

  Since the compression ratio γ at this time is γ = (exclusion volume Ve) / (dead volume Vd), γ1 = Ve / Vd1 in the square and γ2 = Ve / Vd2 in the circle. Since the dead volume Vd is larger in the square (Vd1> Vd2), the compression ratio is γ1 <γ2. That is, the circular pump chamber 40 has a larger compression ratio γ than the square pump chamber 40.

  Further, in the present invention, as described above, the frame 34 forming the pump chamber 40 is formed by laminating a plurality of thin plates (foil), and the apertures are gradually different in diameter so as to approach the curved surface of the diaphragm 36. Therefore, the dead volume Vd can be reduced. For this reason, the compression ratio γ can be increased. In this case, if the pump chamber 40 is made circular, the compression ratio γ can be made larger than that made square for the above reason.

10 Micro-diaphragm pump 20 Valve seat 32a Flow path (suction port)
32b Flow path (discharge port)
34 Frame 34a-34d Thin plate (metal thin plate)
36 Diaphragm 40 Pump chamber 42 Drive element (piezo element, PZT)

Claims (4)

A pump chamber facing the suction valve and the discharge valve is formed by a diaphragm fixed to one side of the suction valve and the discharge valve via a frame, and fluid is guided from the suction valve to the discharge valve by vibration of the diaphragm. A micro diaphragm pump,
The frame is formed of a laminate comprising a plurality of thin plate opening surrounding the pump chamber is formed, the opening diameter of said openings, is close to the curved shape due to the displacement to the pump chamber side of the diaphragm A micro-diaphragm pump characterized by   The micro diaphragm pump according to claim 1, wherein the plurality of thin plates forming the frame are a plurality of thin metal plates, and an opening diameter of each of the thin metal plates changes stepwise.   2. The micro diaphragm pump according to claim 1, wherein the outer shape of the pump is a quadrangle in a plan view and the pump chamber is a circle.   2. The micro diaphragm pump according to claim 1, wherein the diaphragm is vibrated by a piezoelectric element fixed to the diaphragm.

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