EP0836012A2 - Microvalve - Google Patents

Abstract

A micro-valve (50a,50b) controls a fluid flow and consists of a valve flap (52) operated by electro-static force and covering a number of esp. laser-drilled perforations (56) in a plate (54). The thickness of the plate (54) sections between adjacent perforations (56) is reduced in comparison to the thickness of the surrounding material. The rim of each perforation (56) directed towards the valve flap (52) bears a surrounding lip (64). The valve flap (52) has a series of perforations (66) which admit fluid in the open position, and close the plate perforations (56) in the closed position.

Description

The present invention relates to control valves a fluid flow and especially on micro valves and method of manufacturing the same, in which a valve flap spaced very little from a support structure is.

6 shows a cross-sectional view of a known microvalve, that in the U.S. U.S. Patent No. 4,585,209 is. A valve flap 160 is located over a support structure 120, which has a plurality of valve openings 140. This microvalve 100 is a valve that normally closed is.

The situation shown in Fig. 6 relates to an existing one Fluid flow 180 through the valve ports 140 that valve 160 moves to an open state. Becomes now between the support structure 120 and the valve flap 160 an electrical voltage is applied, then the Move the valve flap 160 towards the support structure 120 and that Close microvalve 100, thereby controlling fluid flow 180 can be. The microvalve 100 in FIG. 6 exists the support plate provided with the valve openings 140 120 made of glass, whereas the valve flap 160 made of silicon is made. The plurality of valve openings 140 are formed in the glass plate 120 by means of laser drilling. As in the U.S. U.S. Patent No. 4,585,209, can the glass plate 120 by means of a suitable high-frequency etchant are etched, but then none A plurality of openings can be formed, but only a single valve opening. 6 it can be seen that the support structure 120 has a plurality of valve openings 140 has, however, that with respect to FIG. 6 entirely right valve opening 140 does not do much for fluid flow 180 can contribute because the fluid flow 180 through the valve flap 160 suspended on one side is severely hindered. The essential part of the fluid flow is therefore the Valve openings arranged rather on the left are deliver, whereby an "effective valve opening cross section" much smaller in the known microvalve than a "practically effective valve opening cross section".

Furthermore, the exit path of the fluid flow 180 through the small spacing of the tip of the valve flap 160 from the left holding structure of the valve flap limited. Furthermore enlarge conically in the direction of fluid flow reducing valve openings 140, the shape of which by Technology of laser drilling is the flow resistance the microvalve 100.

U.S. Patent No. 4,538,642 discloses a fast acting mechanical valve that is a first microporous planar having electrically conductive plate-like member 4, which comprises a plurality of openings. The openings of the first electrically conductive film are offset to openings in a second microporous planar electrical arranged conductive plate-like member. Both the the upper film and the lower film are made of aluminum. On the top film is an insulating layer that is made of There is aluminum oxide attached. The top and the bottom Films are short-circuited at one end while at one at the other end an electrical voltage can be applied. A current flowing through the conductive films is in the upper film in one direction and in the lower film in flow back in the opposite direction. This flow of electricity in opposite directions through the parallel they drive electrically conductive films due to opposite electromagnetic fields away from each other, causing opening of the valve is achieved.

DE 4402096 A1 discloses a microminiaturized valve with a crystalline substrate that has a flow path and a has raised valve seat structure. The valve seat substrate includes a single valve opening opposite one Fitting is located, which can close the valve opening. In when closed, the valve touches a valve seat, which extends from the seat substrate, and in the form of a Sealing lip is formed around the valve opening. For Reduction in flow resistance are different Refinements of the valve seat or the sealing edge reveals the only valve opening around.

The object of the present invention is a To create microvalve with minimal flow resistance.

This object is achieved by a method according to claim 1 and solved by a microvalve according to claim 2.

In the case of a microvalve, the position with the smallest is limited Flow cross section the fluid flow through the microvalve. Because of the electrostatically operated micro valves existing small distance between the valve flap and the support structure is not the cross-sectional area determining the valve opening for the fluid flow, but the circumference of the valve opening, the effective flow cross-section essentially from multiplying the Circumference of the valve opening with the distance between the valve flap and circulation structure results.

On the other hand, the cross-sectional area of the valve opening for the fluid power or in the case of a gas as a pneumatic fluid Force that acts on the valve flap is decisive.

• der Umfang der Ventilöffnung muß bei gegebener pneumatisch wirksamer Fläche optimiert werden;
• der Strömungswiderstand der Zuleitungen muß durch Vergrößerung der Querschnittsflächen für die Strömung in den Zuleitungen minimiert werden;
• zur Verringerung des Strömungswiderstandes der Zuleitungen müssen diese ferner verkürzt werden, was durch Bilden von geeigneten Löchern in der Ventilklappe erreicht wird; und
• zum Erreichen eines minimalen Strömungswiderstandes bei geöffnetem Ventil muß die Länge der Ventilöffnungen minimal sein.

The invention is therefore based on the knowledge that the following measures must be taken to achieve the lowest possible flow resistance, ie the highest possible fluid flow:

• the extent of the valve opening must be optimized for a given pneumatically effective area;
• the flow resistance of the supply lines must be minimized by increasing the cross-sectional area for the flow in the supply lines;
• to reduce the flow resistance of the supply lines, these must also be shortened, which is achieved by forming suitable holes in the valve flap; and
• To achieve a minimum flow resistance when the valve is open, the length of the valve openings must be minimal.

All of these measures serve the goal of pneumatic force to minimize the valve flap so it is for operating of the valve can be neglected.

Furthermore, all of the above considerations require additional Boundary conditions are taken into account, e.g. a minimal Space requirement for the microvalve, sufficient stability for mechanical and pneumatic requirements as well lowest possible costs by choosing suitable materials and by limiting it to a minimum number of Manufacturing steps.

In the microvalve according to the invention, the influence should thus be the pneumatic force can be minimized. The opening and Closing forces of the fluid on the valve flap should essentially not caused by the fluid, but be applied to the microvalve from the outside. If the Influence of the pneumatic forces can be neglected could, it would be possible to move the microvalve in either direction to operate. In contrast, the state of the Technology is not an opening force, but this force effected solely by the pneumatic force. This well known So valve is indeed a valve that only in one Direction can be operated.

Fig. 1

eine prinzipielle Darstellung eines Mikroventils;

Fig. 2A

eine prinzipielle Darstellung eines Mikroventils, das eine Maßnahme zum Verringern des Strömungswiderstandes darstellt;

Fig. 2B

eine prinzipielle Darstellung eines Mikroventils, das eine weitere Maßnahme zum Verringern des Strömungswiderstandes darstellt;

Fig. 2C

eine prinzipielle Darstellung eines Mikroventils, das noch eine weitere Maßnahme zum Verringern des Strömungswiderstandes darstellt;

Fig. 3

eine prinzipielle Darstellung eines Mikroventils, bei dem die Maßnahmen der Figuren 2A bis 2C kombiniert sind;

Fig. 4A

eine schematische Draufsicht auf eine Auflagestruktur eines erfindungsgemäßen Mikroventils;

Fig. 4B

eine schematische Draufsicht auf eine weitere Auflagestruktur gemäß der vorliegenden Erfindung;

Fig. 5

eine schematische Draufsicht auf eine Ventilklappe sowie die darunterliegende Auflagestruktur, um die gegenseitige Anordnung von Ventilklappenöffnungen und Ventilöffnungen darzustellen; und

Fig. 6

eine prinzipielle Darstellung eines Mikroventils gemäß dem Stand der Technik;

Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. Show it:

Fig. 1

a schematic representation of a microvalve;

Figure 2A

a schematic diagram of a microvalve, which is a measure to reduce the flow resistance;

Figure 2B

a schematic representation of a microvalve, which is a further measure to reduce the flow resistance;

Figure 2C

a schematic representation of a microvalve, which is yet another measure to reduce the flow resistance;

Fig. 3

a schematic representation of a microvalve, in which the measures of Figures 2A to 2C are combined;

Figure 4A

a schematic plan view of a support structure of a microvalve according to the invention;

Figure 4B

is a schematic plan view of another support structure according to the present invention;

Fig. 5

a schematic plan view of a valve flap and the underlying support structure to show the mutual arrangement of valve flap openings and valve openings; and

Fig. 6

a schematic representation of a microvalve according to the prior art;

Fig. 1 shows schematically a section of a micro valve 10 in cross-sectional representation, its flow resistance should be optimized. The microvalve 10 has a support structure 12 with a valve opening 14 and one Valve flap 16 open. An arrow 18 indicates a fluid flow to be controlled by the microvalve 10. The Valve 10 of FIG. 1 and all others described below However, micro valves are also for the other Fluid flow direction can be used, even if it is not explicit it is said. By means of, for example, electrostatic forces the valve flap 16 can with respect to the support structure 12 are moved such that the valve opening 14 through the Valve flap 16 can be closed. However, it is not possible to open the flap with electrostatic forces. Theoretically, the two electrodes (flap and support structure) electrical charge carriers of the same name be applied that repel each other. The opposite Charge carriers where the electric field lines end, but are far away, e.g. on a metallic Casing. The capacity of this arrangement is so small that for a given voltage almost no charge carriers of the same name be brought on the valve flap and support structure can. In practice, therefore, electrostatic forces are always there attractive. The opening force for the microvalve is then, for example, a mechanical preload, e.g. by a resilient suspension of the valve flap, or a tilted mounting of the flap or a force by a suitable piezoelectric coating.

In the micro valve 10 there are both the valve flap 16 as well as the support structure 12 made of silicon. For professionals it is obvious that the support structure 12 also with respect to FIG the valve flap 16 can be moved depending on the which of the two elements is fixed or elastic is.

The valve flap is in a de-energized or depressurized state 16 spaced a few micrometers from the support structure 12, whereby the valve opening 14 is opened.

The microvalve 10 is activated by the application of an electrical one Tension (not shown) between the support structure 12 and the valve flap 16 is actuated. Charges flow onto the opposite sides of the two components. This Charges attract each other, causing the valve flap 16 is moved towards the support structure 12. For professionals it is obvious that in Fig. 10 it is only is a schematic view because, for example between the two components 12 and 16 necessary insulation layer to prevent charge flow between the same is not shown.

Such a micro valve has due to the electrical Principle a very small distance between the valve flap and support structure. This small distance limited between the valve flap and the support structure the volume flow of the fluid flow 18 through the valve opening 14.

The fluid force or, in the case of a gas as fluid, the pneumatic Force acts in the micro valve in Fig. 1 in Closing direction of the microvalve 10, whereby the supply lines 20 to the valve opening 14 when the microvalve is open 10 can be reduced, which in turn is the inconvenient The effect is that the flow resistance is increased. In closed state of the microvalve 10 acts the pneumatic Force on the valve flap 16 only on the surface the valve flap 16, which lies opposite the valve opening 14. If the cross-sectional area of the valve opening is large, then can lead to the destruction of the valve flap 16 in a corresponding pneumatic pressure come. The compressive strength of the microvalve 10 can therefore be reduced by reducing the pneumatically effective area can be increased. At the same pneumatic pressure can be used to achieve the same Breaking strength, however, reduces the thickness of the valve flap 16 be, which further miniaturization of the Micro valve 10 can be achieved.

2A shows a microvalve 50a according to a first exemplary embodiment of the present invention. A valve flap 52 is arranged over a support structure 54. The support structure 54 has a plurality of valve openings 56, through which a fluid flow 58, through which is shown schematically in FIG. 2A, can flow. On the valve flap 52 opposite The support structure 54 has a recess on the side defines a web 60 of the support structure 54. For professionals it is obvious that in Fig. 2A it is a Cross-section that passes through the centers of the plurality of Valve openings 56 is placed such that the web 60 in the figure appears piece by piece. For professionals, however, it is obvious that the web 60 of the support structure 54 a flat section with compared to the edge sections the support structure 54 is less thick. Further be noted that Fig. 2A is not to scale with respect to Fig. 1 described in connection with the prior art was shown. The opening cross section the valve opening 14 of Fig. 1 is namely the area of the Webs 60, i.e. the portion of the support structure 54 with less Thickness. This will keep the same size the microvalves 10 of FIG. 1 and 50a of FIG. 2A the flow cross section, i.e. the product of the sum of the extent of each the plurality of valve openings 56 with the distance between the valve flap 52 and the support structure 54, essential increases, whereas the pneumatic effective area is not enlarged. In other words, the valve opening cross section a single valve opening 56 much smaller than the valve opening cross section of the valve opening 14 of Fig. 1st

The web 60 defined by the recess is reduced in FIG. 2A effective the length of the valve openings 56 to them in Framework of the stability requirements for the support structure 54 to optimize for minimal flow resistance. The recess in the support structure 54, which as well as the Valve flap 52 is made of silicon, for example wet-chemical to the required web thickness using KOH 60 pre-etched. A currently available dry etching is for Production of the recess is not suitable since 300 µm is too thick. In this membrane, i.e. in the bridge 60, then many openings, for example by means of a KOH etching or realized by dry etching, since the web is essentially thinner than 100 µm.

For example, would fluid flow 58 of FIG. 2A vice versa so that it corresponds to the fluid flow 180 in FIG. 6, thus the microvalve 50a of Fig. 2A would be essential have lower flow resistance because the Length of the valve openings 56 compared to the valve openings 140 through the above-mentioned etching of the silicon support structure 54 can be made significantly shorter. Further The microvalve 50a in FIG. 2A does not have to be complex Processing of 2 components, since the support structure 120 6 is formed from glass while the valve flap 160 in Fig. 6 is made of silicon.

Fig. 2B shows another way to the micro valve 50a of FIG. 2A to improve fluidically. Same Parts in Fig. 2B as well as in all other figures with respect 2A are denoted by the same reference numerals. The difference to Fig. 2A is in Fig. 2B on the valve flap 52 adjacent side of the support structure 54 around each A recess 62 is formed around the valve opening 56. This Recess 62 is from valve opening 56 through a sealing edge 64 separated. The microvalve shown in Fig. 2B has a much lower lead resistance, because the distance between the valve flap 52 and the support structure 54 is enlarged in the recess 62. The variant 2B nevertheless ensures through the sealing edge 64 for reliable control of the fluid flow 58. Furthermore there is no need to produce the recesses and the sealing edge as a kind of inverse depression e.g. can be produced by layer deposition. Compared the height of the sealing edge is therefore also one Deepening available.

In contrast to FIG. 2A, the microvalve from FIG. 2C a plurality of openings 66 in the valve flap 52, which are also referred to as valve flap openings. By Providing the valve flap openings 66 in the valve flap 52, it is also possible to reduce the lead resistance Reduce valve opening 56 by the length of the supply path is shortened compared to Fig. 2A. The valve flap openings can be either wet chemical or dry be etched because the thickness of the valve flap is usually smaller than 100 µm. In summary, it can be said that by the measure shown in Fig. 2B, i.e. the Wells 62, the flow cross section of the feed lines is reduced, while in Fig. 2C the length of the leads can be reduced to the valve opening 56.

3 shows a microvalve 50b according to a second exemplary embodiment of the present invention. The micro valve 50b has a minimal one compared to the microvalve 50a Flow resistance for the fluid flow 58 by the measures for reduction described in FIGS. 2B and 2C the flow resistance into the micro valve 50a of 2A are introduced. The execution of the valve flap 52 offset with a plurality of valve flap openings 66 to the plurality of valve openings 56 provides a maximum Valve opening range compared to the given pneumatic Surface. Providing the recesses 62 together with the sealing edges 64 effectively reduces the lead resistance from the valve flap 52 through the plurality of valve openings 56 of the support structure 54.

4A shows a schematic top view of the support structure 54, the recesses and the sealing edges were omitted for clarity. The circulation structure 3 results from a cross section along line I-I of Fig. 4A. The majority of valve openings 56 here are several rectangular parallel to each other arranged valve openings. For professionals, however, it is obvious that the majority of valve openings when it is also necessary to have curved or triangular structures can accept.

4B shows a further modification of the support structure 54 of Fig. 4A. By the added amount of all valve openings compared to the pneumatically effective surface The rectangular valve openings 56 are to be increased further 4A divided into a plurality of square valve openings 56 been. It therefore results for the circulation structure 54 a kind of a sieve structure. Fig. 3 can also a cross section through the support structure 54 of FIG. 4B be along the line II-II. The majority of the valve openings 56 in Fig. 4B, however, are not square holes limited. For example, the holes can also be round, oval or any other suitable shape. On At this point it should be recalled that the Support structure 54, which is implemented as a chip, is pre-etched must be so that the web 60, as already noted was, is a flat web, is formed. Thereby can keep the length of the valve openings to a minimum can be set.

5 shows a schematic top view of the valve flap 52, the staggered arrangement of the valve flap openings 66 with respect to valve openings 56, which are shown in FIG are shown hatched, is visible. For professionals it is obvious that Fig. 5 is a schematic view is that, in a real plan view, the valve openings 56 would not be seen since it is covered by the valve flap 52 are. For reasons of clarity, neither Wells 62 around the valve openings 56 and the Sealing edges 64 that define the recesses 62 from the valve openings Delimit 56, drawn. The so-called "move Sieve geometries "of regular or irregular Arrays of valve openings 56 compared to the regular or irregular array of valve flap openings 66 thus create a micro valve 50b in which the fluid flow optimized with a minimally effective pneumatic surface is. Thus, after opening the valve flap 52, a fluid can i.e. by creating a distance from the valve flap 52 to the support structure 54, through all valve flap openings 66 flow through the arrangement in a minimal way.

Claims (10)

Method for manufacturing a microvalve (50a; 50b), comprising the following steps: Providing a valve flap (52); Providing a support structure (54) made of silicon; wet chemical etching a recess in the support structure (54) to obtain an area (60) of reduced thickness of the support structure (54); Etching a plurality of valve openings (56) into the region (60) of reduced thickness of the support structure (54); and Arranging the support structure (54) and the valve flap (52) in relation to one another such that the valve flap is movable with respect to the support structure and that the valve flap closes the plurality of valve openings (56) in a first position and of the plurality of in a second position Valve openings (56) is spaced such that a flow cross section, which is defined by the plurality of valve openings and the valve flap, is largely determined by the distance of the valve flap from the support structure. Micro valve (50a; 50b) with: a valve flap (52); and a silicon-containing support structure (54) which has a recess on its side opposite the valve flap (52) which defines a region (60) of reduced thickness of the support structure (54) through which a plurality of valve openings (56) extend,
wherein the valve flap (52) is movable with respect to the support structure (54) and closes the plurality of valve openings (56) in a first position and is spaced apart from the plurality of valve openings (56) in a second position in such a way that a flow cross-section which passes through the plurality of valve openings (56) and the valve flap (52) is defined, is largely determined by the distance of the valve flap from the support structure, and
wherein the recess tapers from the side of the support structure (54) opposite the valve flap (52) to a side of the region (60) opposite the valve flap (52) with reduced thickness. Microvalve (50b) according to claim 2, in which the valve flap (52) has a plurality of valve flap openings (66) which are arranged offset to the valve openings (56) in the support structure (54) such that a fluid flow (58) through the microvalve (50b) can be controlled . Micro valve (50a; 50b) according to claim 2 or 3, in which depressions (62) or elevations are formed around the valve openings (56) in the support structure (54), the depressions (62) being separated from the valve openings (56) by sealing edges (64), while the elevations separate the sealing edges ( 64) are. Microvalve (50a; 50b) according to one of claims 2 to 4, in which the valve flap (52) is also made of silicon. Microvalve according to one of claims 2 to 5, in which the recess is produced by means of KOH etching, while the valve openings (56) and the valve flap openings (66) are etched by wet chemical etching or dry chemical etching. Microvalve (50a; 50b) according to one of claims 2 to 6, wherein the plurality of valve openings (56) are a plurality of substantially parallel rectangles. Microvalve (50a; 50b) according to one of claims 2 to 6, wherein the plurality of valve openings (56) is a plurality of openings arranged in a regular or irregular array. Microvalve (50a; 50b) according to claim 8, in which the valve openings (56) are rectangular, round or oval. Microvalve according to one of claims 3 to 9, in which the majority of the valve flap openings (66) are arranged and shaped offset to the respective valve openings (56) in the support structure (54) such that when the valve flap (52) is closed there is no passage between the valve flap side and the support structure side.

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