EP0826109B1 - Fluid pump without non-return valves - Google Patents

Abstract

A fluid pump has a pump body and a displacer which is adapted to be positioned at a first and at a second end position by means of a drive, the displacer and the pump body being implemented such that a pump chamber is defined therebetween, and the pump chamber being adapted to be fluid-connected to an inlet and to an outlet via a first opening and a second opening which are not provided with check valves. An elastic buffer bordering on the pump chamber is provided. The displacer is implemented in the form of a plate which is secured to the pump body, and the pump body is provided with a recess defining the pump chamber. The drive acts on the displacer substantially in the area of the first opening. The displacer closes the first opening when it occupies its first end position and leaves the first opening free when it occupies its second end position. The drive means moves the displacer so abruptly from the second to the first end position that a deformation of the buffer means is caused by the movement of the displacer.

Description

The present invention relates to fluid pumps.

It is known to transport liquids and gases To use positive displacement pumps, which consist of a periodic Displacer, a piston or a membrane, and two passive Check valves exist. Through the periodic movement of the piston or membrane becomes liquid sucked the inlet valve into a pumping chamber, or through the outlet valve is displaced from the pump chamber. The direction of transport is determined by the arrangement of the valves. With such an arrangement, the pumping direction to be reversed is one in such known pumps external reversal of the Valves necessary. Such pumps are for example at Jarolav and Monika Ivantysyn; Hydrostatic pumps and motors; Vogel Buchverlag, Würzburg, 1993.

Corresponding pumps that are small in size and deliver low pump currents are called micropumps. The displacers of such pumps are typical designed as a membrane, see P. Gravesen, J. Branebjerg, O. S. Jensen; Microfluidics - A review; Micro Mechanics Europe Neuchatel, 1993, pages 143-164. The displacers can are driven by different mechanisms. At H.T.G. Van Lintel, F.C.M. Van de Pol. S. Bouwstra, A Piezoelectric Micropump Based on Micromachining of Silicon, Sensors & Actuators, 15, pages 153-167, 1988, S. Shoji, S. Nakagawa and M. Esashi, Micropump and sample injector for intrgrated chemical analyzing systems; Sensors and actuators, A21-A23 (1990) pages 189-192, E. Stemme, G. Stemme; A valveless diffuser / nozzle-based fluid pump; Sensors & Actuators A, 39 (1993) 159-167, and T. Gerlach, H. Wurmus; Working principle and performance of the dynamic micropump; Proc. MEMS'95; (1995), pages 221-226; Amsterdam, The Netherlands, piezoelectric drive mechanisms are shown. Thermopneumatic mechanisms for driving the displacers are at F.C.M. Van de Pol, H.T.G. Van Lintel, M. Elwenspoek and J.H.J. Fluitman, A Thermo-pneumatic Micropump Based on Micro-engineering Techniques, Sensors & Actuators, A21-A23, pages 198 - 202, 1990, B. Büstgens, W. Bacher, W. Menz, W.K. Schomburg; Micropump manufactored by thermoplastic molding; Proc. MEMS'94; (1994), pages 18-21. An electrostatic mechanism is at R. Zengerle, W. Geiger, M. Richter, J. Ulrich, S. Kluge, A. Richter; Application of Micro Diaphragm Pumps in Microfluid Systems; Proc. Actuator '94; June 15-17, 1994; Bremen, Germany; pages 25-29. Furthermore, the displacers can be thermomechanical or magnetically driven.

As also shown in the above writings, can be either passive check valves or special flow nozzles can be used. The direction of funding of micropumps can be done without forced valve control solely by driving at a frequency above the resonance frequency of the valves are reversed. To be R. Zengerle, S. Kluge, M. Richter, A. Richter; A. Bi-directional Silicone micropump; Proc. MEMS '95; Amsterdam, Netherlands; Pages 19-24, J. Ulrich, H. Füller, R. Zengerle; Static and dynamic flow simulation through a KOH-etched micro valve; Proc. TRANSDUCERS '95, Stockholm, Sweden, (1995), pages 17-20. The cause of this effect is a phase shift between the movement of the Displacer and the opening state of the valves. Is the Phase difference greater than 90 °, so is the opening state the valves are counter-cyclical to their state in normal forward mode and the pumping direction is reversed. An external one Reversal of the valves, as in macroscopic pumps is necessary. The crucial phase difference it depends on the one hand between the displacer and the valves on the drive frequency of the pump and on the other hand from the resonance frequency of the movable valve part in the Liquid environment.

A disadvantage of this embodiment is that the execution of the valves a compromise between their mechanical Resonance in the liquid environment, its flow resistance, their fluidic capacity, i.e. the elastic Volume deformation, their size and their mechanical Stability must be found. These parameters that all can have an impact on the pump dynamics not independently adjusted to an optimum become and stand in part of a desired, further Miniaturization of the pump dimensions counter.

Generally disadvantageous when using pumps with passive Check valves is also the fact that the Pump the medium to be pumped when switched off do not lock. If the inlet pressure exceeds the outlet pressure the preload of the valves, so the pumped flows through Medium the pump.

Have micropumps that use special flow nozzles the disadvantage that they have a very low maximum Have pump efficiency in the range of 10-20%.

An exemplary check valve micropump is disclosed in EP 0 568 902 A2. This micropump is operated by the reciprocal movement of a membrane. The volume of a changes due to the movement of the membrane Pump chamber formed by the membrane and a support member is. The outlet and inlet of the micropump are provided with an outlet valve or an inlet valve.

In WO-A-87/07218 is a piezoelectrically operated Pressure generating device known that an electrically controllable Membrane made of a first piezoelectrically excitable Layer and a firm with this stimulable layer connected support layer. The membrane has one piezoelectrically excitable peripheral area and a piezoelectric excitable central area, the Areas are controlled such that to generate a Membrane deflection the membrane in its peripheral area shortened by transverse contraction and in its central area is extended. WO-A-87/07218 also discloses a fluid pump using three interconnected Membranes of the type described above, one first membrane serves as an inlet valve, a second membrane defines a variable cavity and a third membrane serves as an outlet valve.

FR-A-2478220 discloses a pump in which two drive devices are intended to be a flexible membrane, which is provided with a movable plate, in different To move end positions. The membrane is on attached to a support plate, the middle of an inlet opening having. Outlet openings are provided in the membrane. A suitable control can result in a pumping effect are generated from the inlet opening to the outlet openings.

Based on the prior art mentioned, the present Invention based on the task of efficient fluid pumps with a simple structure that has no check valves have to create.

This task is accomplished by means of non-return valve fluid pumps solved according to claims 1, 14 and 20.

In the fluid pump according to the present invention no check valves, neither passive nor active, required. Furthermore, the fluid pump according to the present Invention for actively blocking the fluid in both directions be used. With the pump according to the present Invention is a reversal of the conveying direction without use an external positive control of valves and without the Using a resonance of passive check valves reachable. The one with the pump according to the present invention achievable pumping capacity can be controlled by the Timing of driving the displacer into the first and in the second end position, i.e. by controlling the clock ratio, be optimized. Furthermore, the achievable Pump power through a cross-sectional adjustment of the first and second opening can be optimized.

The present invention is also based on the finding that that it is possible to use a self-priming fluid pump, for example a self-priming micropump create by creating the dead volume in the micropump, i.e. the volume that is only moved back and forth and does not provide a pump contribution, is drastically reduced. This makes self-filling with simple control of the pump drive reproducible.

Further developments of the present invention are in the dependent Claims set out.

Fig. 1

eine schematische Querschnittdarstellung eines ersten Ausführungsbeispiels der vorliegenden Erfindung;

Fig. 2

eine Darstellung der wesentlichen Pumpparameter der Pumpe, die in Fig. 1 gezeigt ist;

Fig. 3

eine Darstellung der transienten Vorgänge der einzelnen Komponenten der in den Figuren 1 und 2 dargestellten Pumpe;

Fig. 4a bis 4e

graphische Darstellungen der Pumpe von Fig. 1 während eines Pumpzyklusses;

Fig. 5

eine Schnittansicht einer Fluidpumpe;

Fig. 6

eine Querschnittansicht einer weiteren Fluidpumpe;

Fig. 7

eine Schnittansicht noch einer weiteren Fluidpumpe;

Fig. 8

eine Darstellung der transienten Vorgänge der einzelnen Komponenten bei einer Rückwirkung der Pumpkammer auf den Verdränger;

Fig. 9

ein zweites Ausführungsbeispiel einer Pumpe gemäß der vorliegenden Erfindung; und

Fig. 10a bis 10e

graphische Darstellungen einer Pumpe gemäß einem dritten Ausführungsbeispiel der Erfindung während eines Pumpzyklusses.

Fig. 11

eine Querschnittdarstellung eines vierten Ausführungsbeispiels einer Fluidpumpe gemäß der vorliegenden Erfindung;

Fig. 12

eine Querschnittdarstellung eines fünften Ausführungsbeispiels einer Fluidpumpe gemäß der vorliegenden Erfindung;

Fig. 13

eine Querschnittdarstellung eines sechsten Ausführungsbeispiels einer Fluidpumpe gemäß der vorliegenden Erfindung;

Fig. 14a bis 14e

grafische Darstellungen der Pumpe von Fig. 11 während eines Pumpzyklusses; und

Fig. 15a bis 15e

grafische Darstellungen der Pumpe von Fig. 13 während eines Pumpzyklusses.

Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings, the same elements being denoted by the same reference symbols in different drawings. Show it:

Fig. 1

is a schematic cross-sectional view of a first embodiment of the present invention;

Fig. 2

a representation of the essential pumping parameters of the pump, which is shown in Fig. 1;

Fig. 3

a representation of the transient processes of the individual components of the pump shown in Figures 1 and 2;

4a to 4e

graphical representations of the pump of FIG. 1 during a pumping cycle;

Fig. 5

a sectional view of a fluid pump;

Fig. 6

a cross-sectional view of another fluid pump;

Fig. 7

a sectional view of yet another fluid pump;

Fig. 8

a representation of the transient processes of the individual components in a reaction of the pump chamber on the displacer;

Fig. 9

a second embodiment of a pump according to the present invention; and

10a to 10e

graphic representations of a pump according to a third embodiment of the invention during a pumping cycle.

Fig. 11

a cross-sectional view of a fourth embodiment of a fluid pump according to the present invention;

Fig. 12

a cross-sectional view of a fifth embodiment of a fluid pump according to the present invention;

Fig. 13

a cross-sectional view of a sixth embodiment of a fluid pump according to the present invention;

14a to 14e

graphical representations of the pump of FIG. 11 during a pumping cycle; and

15a to 15e

graphical representations of the pump of FIG. 13 during a pumping cycle.

In Fig. 1 is a first embodiment of a pump according to of the present invention. The pump has one Pump body 10, which is plate-like, and a displacer 12, which has connections 18, which depend on the material are attached to the pump body is on. A pump chamber 14 is through a recess in the pump body 10 is formed. In the pump body are also two openings, a first opening 15 and a second Opening 16, provided to which the fluid lines of the pumping fluids can be connected. An elastic one Buffer 13 is through in the first embodiment a thinning of the pump body 10 in the form of a membrane, which is deformable depending on the pressure.

The displacer 12 can be driven (not shown) by a drive. periodically to and fro between two end positions will. The displacer closes in the first end position 12 the first opening 15, which is in normal operation of the pump represents the inlet. In the second end position, the Displacer 12, the first opening 15 open. The second opening 16, which is the outlet in normal operation, is irrelevant the position of the displacer 12 during an entire Pump cycle open.

In the following, the pump mechanism is that shown in FIG. 1 Pump explained in more detail. For this explanation the first opening 15 as an inlet opening and the second opening 16 considered as an outlet. 2 are the essential ones Parameters used to explain the pumping mechanism are shown.

It is assumed that the hydrostatic pressure pl prevails on the inlet side, the hydrostatic pressure p2 on the outlet side and the pressure p in the pump chamber. The flow through the two openings is denoted by  _e for the inlet opening 15 and by  _a for the outlet opening 16. The displacer, in which, according to the first exemplary embodiment, the rest position corresponds to the first end position, in which the inlet opening is closed, is moved into its second end position by the actuation of the drive, as a result of which the volume of the pump chamber changes by a defined volume dV * . A pressure-dependent volume displacement of the elastic buffer is called V _buffer . It is evaluated positively if the membrane 13 bulges out of the pump chamber 14 and negatively if it deforms into the pump chamber 14.

The volume of the pump chamber is composed of a basic volume V _{0 of} the pump chamber 14, the deflection of the displacer 12 V _displacer and the volume deformation of the _buffer volume V _buffer according to the following equation: V Pumping chamber = V 0 + V buffer (p) + V Displacer

A change in the pump chamber volume dV _{pump chamber} is made up as follows: dV Pumping chamber = dV 0 (p) + dV buffer (p) + dV Displacer

The continuity equation for the volume of the pump chamber is: dV Pumping chamber / dt =  e (p 1 -p) -  a (pp 2nd )

An entire pump cycle can be broken down into four sub-steps, whereby the time sequences can be calculated on the basis of equation (2) and equation (3) using some simplifying assumptions. In the following the temporal behavior of the individual pump components in the four sub-steps as well as the resulting pump effect is explained. A pump chamber is initially assumed which is completely filled with an incompressible medium, for example a liquid with dV ₀ / dp ≈ 0. The following applies: dV 0 (p) = [dV 0 (p) / dp] dp = 0

Sub-step 1:

The displacer 12 is moved from the first end position, that is to say the end position in which it closes the inlet opening 15, upward by a defined volume dV * within a very short time, dt ≈ 0. This leads to a corresponding volume deformation of the elastic buffer volume, ie the membrane 13, into the pump chamber, since the content of the pump chamber was assumed to be incompressible, and since within the short time dt ≈ 0 the volume change of the displacer 12 was not due to the fluid flows  _e and  _a can be compensated. If dt ≈ 0 is assumed, dV _{pump chamber} ≈ 0 results from equation (3) and from this with equations (2) and (4) dV _buffer = -dV _displacer = -dV *. The deformed buffer volume creates a negative pressure in the pump chamber 14, which can be calculated using the characteristic V _buffer (p).

Sub-step 2 (suction phase):

Due to the negative pressure generated in the pump chamber, fluid flows through the inlet and outlet openings now occur. The buffer volume relaxes in accordance with the amount of fluid flowing into the pump chamber, the negative pressure generated by the latter decreasing. The time course of the pump chamber pressure in this pumping phase results from equations (2) and (3): dp / dt = [ e (p 1 -p) -  a (pp 2nd )] / [dV buffer / dp]

If the flow resistances of the inlet and outlet openings are the same and the hydrostatic pressures p ₁ and p ₂ correspond to the ambient pressure, the same amount of fluid flows into the pump chamber 14 through the inlet and outlet openings.

Sub-step 3:

Now the displacer is moved from the second end position, ie the end position in which the inlet opening was open, downward within a very short time, dt ≈ 0, by a defined volume dV _displacer = -dV *. The inlet opening is now closed. The downward movement of the displacer 12 leads to a corresponding volume deformation of the elastic buffer, ie the membrane 13 in the first exemplary embodiment, out of the pump chamber 14, since the pump chamber content was assumed to be incompressible, and the volume change of the displacer 12 within the short time not due to the fluid flows  _e and  _a can be compensated through the opening 15, 16. If the time sequence occurs within dt ≈ 0, then dV _{pump chamber} ≈ 0 results from equation (3) and from this with equations (2) and (4): dV _buffer = -dV _displacer = + dV *. The deformed buffer volume now creates an overpressure in the pump chamber, which can also be calculated from the pressure characteristic V _buffer (p) of the buffer.

Sub-step 4 (pumping phase):

After substep 3, the inlet opening 15 is closed by the displacer 12. Thus, the fluid flow that occurs in the pumping chamber 14 due to the excess pressure can only leave the pumping chamber through the outlet opening 16. The buffer volume relaxes in accordance with the amount of fluid flowing out of the pump chamber, the excess pressure generated by the buffer volume reducing. The time course of the pump chamber pressure in this phase again results from equations (2) and (3): dp / dt = [- a (pp 2nd )] / [dV buffer / dp]

As is evident from the above explanation, the fluid quantity dV * is sucked through the inlet and outlet openings 15, 16 during the sub-step 2, whereas it is displaced through the outlet opening 16 during the sub-step 4 alone. If the flow resistances of the inlet and outlet openings are the same and the pump works without load, ie p ₂ = p ₁ = 0, 50% of the displacer volume dV * is transported from the inlet 15 into the outlet 16 in the net balance over an entire cycle.

From a comparison of equations (5) and (6) it can be seen that substep 2, the suction phase, is faster expires when the sub-step 4, the pumping phase. The cause this is because the negative pressure in the suction phase a fluid flow through both openings is balanced. The overpressure in the pumping phase, however, must be caused by a fluid flow balanced by only one opening, the outlet opening 16 will.

By varying the flow resistances of intake and outlet opening, i.e. a change in the opening cross-sections of the two openings, the pump efficiency can vary will. In particular by increasing the flow resistance on the outlet side with respect to the inlet side the efficiency in the no-load case can be clearly seen be optimized more than 50%. The reason for this is in a significantly lower backflow of fluid from the outlet into the pumping chamber during the suction phase. However, the Increase in flow resistance on the outlet side according to Equation (6) a corresponding extension of the pumping phase result.

Suction and pumping phases of different durations can take place at the Control of the displacer can be taken into account by a clock ratio other than 50% is used, i.e. by the timing of driving the displacer into the first and is controlled in the second end position. By doing Case, the increased flow resistance on the outlet side this means that the suction phase by controlling the Displacer is shortened while the pumping phase is extended becomes.

3 shows the transient processes in the pump according to Fig. 1 shown in diagram form.

The curve "A" shows the course of the displacement movement during a pump cycle in the four sub-steps 1, 2, 3 and 4. In step 1, the displacer quickly adapts deflected above and remains in step 2 during this Position. The inlet opening is open. In step 3 the displacer is moved down very quickly, closes the entrance opening and remains during the Step 4 in this state.

Curve "B" represents the response of the buffer, which according to the embodiment of FIG. 1 consists of the membrane 13. This elastic buffer element in the form of the membrane 13 can deform in accordance with the pressure conditions. During step 1, the deformation of the Buffer the volume change of the displacer. During the Step 2 builds up the deformation of the buffer Fluid flows through the inlet or outlet opening again from. In step 3, the buffer element deforms downwards and thus compensates for the rapid volume change of the displacer. This deformation builds up during substep 4 due to the fluid flow through the outlet opening.

The curve "C" represents the pump chamber pressure. Since the pump chamber pressure depends on the deformation of the buffer its course essentially the course of the volume change through the buffer.

Curve "D" illustrates the flow through the inlet opening. From the curve "D" is a rectifier effect recognizable, since the inlet is closed in step 3 and during substep 4, during which in the pressure chamber there is overpressure, remains closed. In order to is a backflow from the pump chamber to the inlet side prevented.

Curve "E" shows the flow through the outlet opening. Since the outlet opening in both end positions of the displacer is open, the fluid flows in both step 2 and in step 4 through the outlet opening. The net transportation of Fluid through the inlet and outlet ports results from the integral over one of the two curves "D" or "E". in the normal mode of operation is the net transport from inlet to Outlet directed.

4a to 4e is the pump according to the first embodiment, which is shown in Fig. 1 during the various Partial steps of a pump cycle are shown.

Figures 5, 6 and 7 show fluid pumps.

Fig. 5 shows a pump in which a buffer 43 in a pump body 40 is arranged. The pump body 40 has one Base plate 40a and side walls 40b, which together form one Form hollow body by the side walls 40b and Base plate 40a is completed and on one side, in Fig. 5 of the upward side is open. Know that Base plate has a round shape, the side walls are formed, to define a tubular structure. By the base plate extends an inlet opening 45 and Outlet opening 46. A displacer is located in the cavity 42, which closes the same towards the open side and by means of a drive (not shown) in the Direction shown by arrow 19 is piston-like in the cavity is movable.

A pump chamber 44 is through a recess of the displacer 42 and the pump body 40 are formed. The elastic Buffer 43 is in the pump body 40, i.e. in the side wall 40b of the base body 40 educated. For this purpose, the side wall 40b is in one Area adjacent to pump chamber 44 is thinned by one to result in membrane-like structure.

6 shows a further fluid pump. A pump body 50 is included constructed in the same way as the pump body 40 the pump shown in Fig. 5, except that the elastic Buffer is not formed in the same. In the pump body 50 is in turn a displacer 52 and Movable piston-like in the direction of arrow 19. The displacer 52 has the shape of an H in cross section, wherein one leg thereof has a protrusion 52a to one To close inlet opening 55 in the pump body 50. A Outlet opening 56 in the pump body 50 is always open. The displacer 52 is formed around the pump body 50 to close to the open side. He can depending on the shape of the pump body 50, seen from above, any round, polygonal, elliptical, etc., Have shape.

The shape of the displacer 52 is between the displacer 52 and the pump body 50 in turn a pump chamber 54 Are defined. In contrast to that described with reference to FIG. 5, Pump is the elastic one But don't buffer in that Pump body 50 formed, but in the displacer 52 is the elastic buffer as membrane 53 in the displacer 52 trained.

7 is yet another fluid pump shown. In Fig. 7 are components that are similar to those in Fig. 6, with the the same reference numerals. The pump body is identical to the pump body shown in Fig. 6. An elastic buffer element 63 is arranged in a displacer 62, such that the elastic buffer element 63 is an interface to one formed by the displacer 62 and the pump body 50 Has pump chamber 64. When this pump is operated, it will elastic buffer element 63 compressed and expanded, which in turn changes the previously explained mode of operation results.

In addition to the elastic buffers shown, the function of the elastic buffer element also from an elastic one Medium are taken over in the pump chamber. Examples are a gas inclusion in a liquid filled Chamber or a rubber-like material in the pump chamber. In this case, the elastic membrane, which is called Part of the displacer or the pump body a section of the pump chamber limitation, can be dispensed with. Provided the medium to be pumped is compressible, for example gas, the buffer function can be taken over by the same itself, with no other mechanical components to be realized of the buffer are necessary. The stroke of the displacer in steps 1 and 3 explained above is then first through expansion or compression of the elastic medium in the pumping chamber or the medium to be pumped itself, to be compensated. Relaxed in steps 2 and 4 the volume deformation of the medium as a result of fluid flows through the openings as referenced above of the first embodiment have been described. A clean So gas pump can only with one displacer and two Openings can be realized, with the displacer in each case periodically closes one of the two openings.

In the description of the pumping mechanism above, a positively controlled volume displacer, at which has no retroactive effect between the displacement position and the pump chamber pressure. For such a realization are drive mechanisms with a very large force density necessary. The pump mechanism also works when one such retroactivity, or coupling, is present.

A representation of the transient processes of the individual components, for example that of the embodiment that is shown in Fig. 1, with a reaction of the pump chamber on the displacer, i.e. without forced control, is in Fig. 8 shown. In this case the displacer is in Step 1 does not fully reach its final end position, but only towards the end of sub-step 2. Correspondingly the displacer must at the end of substep 3 Do not completely close the inlet opening yet, but only with increasing pressure equalization during the substep 4. A very fast control is also required for the pump effect of the displacer within a very short time, dt ≈ 0, inexpensive, but not absolutely necessary.

According to an advantage of the present invention, it is possible the position of the displacer in the deactivated mode to design the pump without any additional effort, that by blocking the inlet opening by the displacer fluid flow in both directions excluded is. Is the displacer positively controlled and its position due to the pressure prevailing in the pump chamber is affected by the blocking of the fluid line in given both directions without additional effort. If there is a reaction between the displacement position and the pump chamber pressure exists, the drive of the displacer can be interpreted in such a way that the active displacer presses on the inlet opening and thus the fluid flow is active prevents. With a piezoelectrically driven one Displacer, for example by means of a piezo stack actuator, a piezo disk or a piezo bending transducer , this would only be the polarity reversal of the operating voltage require.

According to a further advantage, the pumping direction can be one Fluid pump can be reversed according to the present invention. If the displacer is driven with a frequency that above the mechanical resonance of the buffer in that Environment, i.e. in the fluid to be pumped, this results in a phase shift of more than 90 ° between the expansion or compression of the buffer element and the opening condition defined by the displacement position the inlet opening. The buffer in the pumping chamber thus increases Pump medium while the inlet opening is closed, and releases pumping medium when the inlet and outlet openings are open are. This results in an inverse to that described above Pump direction. In this case there is a reversal the pumping direction from the outlet opening to the inlet opening.

The advantage over the existing, bidirectional Micropump lies in the fact that (i) passive Valves can be dispensed with entirely, and (ii) the resonance frequency of the buffer differently than with the resonance of a passive Check valve, regardless of other important Variables such as the flow resistance of the valve, the fluidic capacity, the size of the valve and its mechanical stability can be adjusted. As a result, the resonance frequencies can range from <200 Hertz can be lowered, which means that the effort at electrical and mechanical control of the displacer is significantly reduced. In contrast, passive Valves resonate in the range between 2000 Hertz and 6000 Hertz. By reducing the resonance frequency the inertial forces acting on the displacer are clear less. Furthermore, the mechanism cannot be limited to microscopic Pumps that deliver small moving masses but can also be realized in a macroscopic design.

Another advantage of a fluid pump according to the present Invention arises when the same as a micropump is performed. Although conventional micropumps can transport both liquids and gases, they are not self-priming throughout, i.e. she are unable to hold a pump chamber filled with gas To be replaced independently by liquid during the pumping process. This makes it difficult to use the pumps in practice quite considerably. The following is the causes of the nonexistent self-priming.

Capillary forces play in micropumps with passive check valves a major role. As soon as the liquid level reaches the inlet valve and the movable valve part, the valve flap or the valve membrane, wetted, capillary forces occur which severely restrict movement or which the necessary effort to move the enlarge the elastic valve part considerably. Only when that entire movable valve part completely with liquid is washed around, these forces cancel each other out and the pump is in its normal pump mode.

Because with conventional micropumps, the passive check valves can not be controlled from the outside, you can drive not directly to overcome capillary forces deploy. Rather, with the drive, the gas is in first to compress or expand the pumping chamber, wherein a force to overcome the capillary forces only via the gas pressure is transferred to the valves. This indirect Power transmission via a compressible gas connected to the Fact that the net surface of the pressure on the movable Valve part is very small, contains very large ones Losses in power transmission from the actuator to the check valve and prevents in the currently known micropumps the self-priming.

When realizing micropumps with nozzles instead of Check valves to define the pumping direction occurs a pumping effect only when the flow resistance everyone individual nozzle in the pumping direction is lower than the opposite for pumping direction. When averaging over the whole Pump cycle, this means for the inlet nozzle that the volume flow into the pumping chamber must be greater than out of the pumping chamber. However, as soon as the fluid meniscus reaches the inlet nozzle, the changes Flow resistance of the nozzle due to the greater density the liquid dramatically. Becomes a for density change typical value of 1,000, the flow resistance changes by the factor (1000) ½ ≈ 30. Since in pumping direction Liquid flow through the nozzle is the volume flow significantly less than contrary to the pump direction, because in this case gas flows through the nozzle. In this Situation breaks down the pumping action, being from this There is no self-priming.

In contrast to the known micropumps just described can the actuator directly in the pump according to the invention be used to overcome the capillary forces. By the direct power transmission of the drive to that of one Liquid wetted parts are subject to much higher forces Overcoming capillary forces available. Thus, the Work displacer despite wetting.

In Fig. 9 is a second embodiment of a pump according to the present invention.

In this embodiment, the displacer 82 is part of a second pump body 90. The second pump body 90 is structured, i.e. it exhibits thickening and thinning 89 to create an elastic suspension for the displacer 82 to deliver. The second pump body 90 is via connections 88 attached to a pump body 80. The pumping chamber 84 is as a capillary gap between the pump body 80, the displacer 82 and the second pump body 90 educated. The pump body 80 has an inlet opening 85 which is closed by the displacer 82 when it is in the first end position. The displacer 82 can in turn be moved in the direction of arrow 19. There are two outlet openings in the second pump body 90 86a and 86b. The buffer is in this embodiment again designed as a membrane, which is in the pump body 80.

In an alternative embodiment, the buffer could through the dilutions 89, which are called elastic suspensions serve for the displacer 82, be realized, the Buffer in the pump body 80 would then be eliminated. In this Case it would be advantageous if the dilutions 89 opposite 9 would be enlarged.

If the overall height of the pump chamber 84, as in the present Embodiment, designed as a capillary gap, it fills itself as soon as a fluid meniscus abuts this gap. Such a reduction in Pump chamber height is in conventional micropumps with check valves excluded, as this causes the movement of the Valves is restricted. For micropumps with flow nozzles provides the pump chamber with a drastic reduction the pump chamber height an additional flow resistance This internal flow resistance of the pump chamber dominates about the flow resistance of the nozzles, so that the Pump effect breaks down based on the preferred direction of the nozzles.

In the exemplary embodiments described so far, the second opening, the outlet opening during normal operation of the pump always corresponds to open.

10a to 10e is a third embodiment a pump according to the present invention during the different sub-steps of a pump cycle are shown.

In the pump according to FIGS. 10a to 10b, the buffer is in the displacer formed such that the displacer and the Buffer formed as different areas of a membrane which spans the pump body to the pump chamber define. The pump body is similar to that of the first Embodiment formed, with the exception that the Buffer is not formed in the same. Such a structure the pump according to the invention enables a further simplified Making the same.

The present invention thus provides a pump based on is based on a new mechanism, completely without check valves gets along and a reversal of the pump direction without external valve reversal. Consequently the pump according to the present invention has one essential simpler construction. Furthermore, the displacer simultaneously used to flow over a fluid the pump is passive in both directions after it is switched off or actively shut off.

The present invention also provides a pump that Provides advantages when switching the pump direction. According to of the present invention, the resonance of the mechanical Component, which in the conventional case the valve and in the present invention the buffer element is independent the flow resistance of a valve whose Size, its fluidic capacity and its mechanical Stability can be set. This makes it possible on the one hand to further miniaturize the components and on the other hand to lower the resonance frequencies on average. In conventional micropumps, these stand up opposite effects.

In contrast to conventional micropumps, where typical Resonance frequencies in the range from 2000 Hertz to 3000 Hertz is a reversal of the pumping direction at one Pump according to the present invention already on frequencies of 40 Hertz possible. This will reduce the effort of the electrical and mechanical control of the displacer considerably reduced. In addition, the inertial forces on the Displacers work, significantly less, and the mechanism can not only be realized with microscopic pumps, but also in a macroscopic design.

Compared to pumps with flow nozzles, the inventive one Pump that works without check valves, one increased efficiency per pump cycle of more than 50% on.

In a micromechanical embodiment of the invention The pump can only be structured from a single one Component in which the displacer is implemented, and one Base plate with two openings. These simple ones Structures allow the entire system to be assembled without any problems. A basic structure made of Pyrex allows the anodic Bonding the structured silicon component to the Pyrex base body, which serves as a pump body. The openings in the basic structure can be as simple holes or any be shaped. This reduces the effort compared to the production of flow nozzles considerably. Further the basic design of the micropump can be round or any have any shape.

In addition to silicon, the materials for the micropump come as well almost all other materials are considered, for example metals, Plastics, glasses, ceramics. It is a simple one Production in plastic injection molding technology also possible such as production using metal pressure casting technology or the LIGA process.

The drive of the micropump, i.e. of the displacer, can by all known actuator processes take place, for example piezoelectric, pneumatic, thermopneumatic, thermomechanical, electrostatic, magnetic, magnetostrictive or hydraulic.

Via integrated sensors, for example in the buffer membrane can be built a control loop that drives the Brings the micropump into the optimal working range.

The field of application of the pump according to the invention covers the whole Area of microfluidics and fluidics as the medium both conveyed bidirectionally and blocked in a defined manner can be. The minimal size enables the Development of minimal mixing and dosing systems in the medical, Chemical and analysis technology. At B.H. van de Schoot, S. Jeanneret, A. van den Berg and N.F. de Rooij; A silicon integrated miniature chemical analysis system; Sensors and Actuators, B, 6 (1992), pages 57-60, are for such Application uses two pumps, whereas one uses only a pump according to the invention would do. Generally is the pump principle is suitable for a wide range of sizes, so that in many cases the injection molding technology as inexpensive Manufacturing technology can be used.

Fig. 11 shows a fourth embodiment of a self-priming Fluid pump according to the present invention. The Fluid pump has a pump body 110, on which by means a connecting device 112 a displacer 114 in the Form of a membrane 114 is attached. The membrane 114 can on the sections where the displacer on the pump body 110 is attached, be thickened. The membrane 114 is by means of a drive device 116, which is a piezoelectric, a pneumatic, a thermopneumatic, a thermomechanical, electrostatic, magnetic, a magnetostrictive or a hydraulic drive arrangement can be from the position shown in Fig. 11 and is referred to below as the first end position, movable into a second end position. In this embodiment are two openings 118 and in the pump body 110 120 arranged, for example, with an inlet or Outlet fluid line (not shown) may be connected. In the pump shown in FIG. 11, the opening is 118 the inlet opening, while opening 120 the outlet opening represents. The membrane 114 is preferably directly over the Inlet opening 118 connected to drive device 116, to the operation of the pump, referring to below 14 will be explained. To attach the Drive device the membrane 114 in place of the same, at which it is connected to the drive device 116 is thickened.

The self-priming, self-filling shown in Fig. 11 Micropump differs from known micropumps in that they alternate the first in pump mode Opening 118 opens while second opening 120 closes remains to then open the second opening 120 while the first opening is closed. In the case of Fig. 11 pump is always only one at any time Opening, 118 or 120, opened while the other opening closed is. Both openings 118 are at rest and 120 closed, whereby the pumping medium is shut off in a defined manner becomes.

12 is a fifth embodiment of an inventive one Fluid pump shown. The fluid pump has again a pump body 110, on which by means of a Connection device 112 a membrane 124 is attached. In this embodiment, however, is between the membrane and a capillary gap 126 is formed in the pump body. To close openings 118 and 120 when the displacer, i.e. the membrane 124 is in the rest position the membrane thickened at the locations of the openings facing the surface of the plate of the pump body 110 are. Again, there is a drive device on the membrane 116 attached.

On the top, i.e. the one facing away from the pump body Structures can be formed on the side of the membrane 124 be the optimal buffer volume adjustment and emptying enable. Structuring, which can be designed, for example, as flow channels, on the top of the pump body, i.e. the top that faces the membrane 124, or the underside of the membrane used for optimal filling or emptying of the pump will.

As an alternative to the exemplary embodiment shown in FIG. 12 could be openings 118 and 120 made in the pump body 110 are arranged, further surveys, the same surrounded, have. In this case, the membrane 124 would have to have no thickenings facing the pump body 110, to allow openings 118 and 120 to be closed.

13 is a sixth embodiment of a fluid pump according to the present invention. In the The pump shown in Fig. 13 is between the pump body 110 and a membrane 136 forming a displacer is a capillary Gap formed. In this embodiment In the present invention, it is significant that the two Openings 118 and 120 spaced apart from each other on different Arranged sides of a central axis of the membrane 136 are. This asymmetrical structure of the invention Pump is a self-priming or self-filling Operation of the micropump according to the present invention possible.

14a to 14e, a Pump cycle of the pump shown in Fig. 11 explained. It should be pointed out here that in FIG. 12 illustrated embodiment of the present invention undergoes a similar pump cycle during operation.

14a the pump is shown in the rest position, which is also shown in Fig. 11. Are in this position both connections closed, which means an absolute media lock is produced.

Then, as shown in Fig. 14b, the displacer, i.e. the membrane 114, from the rest position in the direction of in of the arrow shown in FIG. 14b is moved upward selectively, the inlet opening, opening 118, being opened, while the outlet opening, the opening 120, is closed remains. The position shown in Fig. 14b can be second End position of the displacer can be considered.

In Fig. 14c it is shown how by the upward movement the displacer a medium to be pumped through the inlet opening, i.e. the opening 118 into which by the upward movement of the displacer pump chamber is drawn. Subsequently, as shown in Fig. 14d, the displacer suddenly, selectively moved down and closed hence the inlet opening. Due to the displacement deformation, i.e. the deformation of membrane 114 becomes a buffer volume formed between the diaphragm and the pump body, which is the absorbed Fluid volume corresponds to what causes the Exhaust opening is released.

As shown in Fig. 14e, the buffer volume through the outlet opening, i.e. the opening 120, emptied, wherein the medium to be pumped "shifted" or via a "Roll displacement" was transported.

The one described above with reference to FIGS. 14a to 14e Pump mechanism gives a pumping direction from the inlet opening 118 to the outlet opening 120. By increasing the drive frequency to a frequency above the resonance frequency of the overall system, consisting of the displacer and the fluid system, the pump direction can be reversed will. It is obvious that the inlet or reverse the outlet opening, i.e. that the inlet opening 118 becomes the outlet opening, and the outlet opening 120 becomes the inlet opening.

That with every pump cycle of the fluid pump according to the invention volume of the medium received through an opening corresponds to the volume dispensed through the second opening of the medium. The occurring in the pump according to the invention Backflow or dead volume, i.e. that volume that is only moved back and forth and does not provide a pump contribution, go with this arrangement in contrast to known micropumps towards zero. This is in the case of the invention Micropump with simple control of the drive device self-filling in connection with membrane deformation and the sequential opening of the openings reproducible.

15a to 15e is a pump cycle of that in FIG. 13 shown sixth embodiment of a pump according to of the present invention. As shown in Fig. 15a is, the membrane 136 is initially based on a Rest position moved downwards by means of the drive device 116, such that the opening 118 is closed. In turn to simplify the explanation, let opening 118 be that Inlet opening referred to as opening 120 as the Exhaust opening is called. The one shown in Fig. 15a The position of the membrane 136 can be referred to as the first end position will.

As shown in Fig. 15b, the membrane 136 becomes subsequently moved jerkily upwards. In this case it is not only one opening is closed while the other is open is. As shown in Figs. 15b and 15c here both openings briefly opened, however a different dimension of the medium through the openings flows because the opening height, i.e. the distance of the membrane above the openings, and thus the flow resistance. Thus flows in through the inlet opening 118 greater fluid flow than through outlet opening 120. This is shown in Fig. 15c by the different strengths Arrows appear.

As shown in Figure 15d, the membrane is subsequently moved jerkily downward, closing the opening 118 becomes. Again is between the membrane and the Pump body formed a pump volume that, as in Fig. 15e is shown, then by reshaping the displacer is emptied through the opening 120.

In the fluid pump shown in Fig. 13, its operation 15, there is a larger one Dead volume than in the fourth and fifth exemplary embodiments of the present invention shown in Figs. 11 and 12 are shown. This indicates with respect to FIGS. 13 and 15 described sixth embodiment of the present Invention is less efficient than that regarding 11 and 12 described embodiments.

The micropump according to FIGS. 11 and 12 can be operated with a fill the constant drive frequency yourself. After that too pumping medium has filled the pump chamber or the pump chamber and emerges at the outlet opening, the drive frequency the drive device that drives the displacer, in the case of pumping a liquid medium by a factor 10 can be reduced because air is no longer displaced must, but only the liquid medium.

One basis for the pump mechanism is displacement and the arrangement of the openings. The one to be pumped Medium is received through opening 118 and to the opening 120 "shifted" or via a "roll displacement" transported.

The pump body and displacement devices according to the present Invention can preferably consist of silicon. In addition, they can also be used in plastic injection molding be made. As drive devices can all drives known in the art can be used. The transient waveforms characteristic of the micropump for the stroke, the pump chamber pressure, the displacement volume change and the flow can be derived easily will.

As an alternative to the fluid pumps shown, a capillary Gap between the displacer membrane and the pump body plate also through a recess in the pump body plate be educated.

The present invention enables according to the second and third aspect of the same, the production for the first time non-return valve, self-priming, i.e. self-filling, Micropumps. The field of application of the invention Pumping covers the entire field of microfluidics and Fluidics, since the medium to be pumped is both bidirectional can be promoted as well as blocked. Further are the pumps according to the invention with minimal effort and can be manufactured with minimal sizes. Through this Small sizes, the present invention enables Development of minimal mixing and dosing systems in the medical, Chemical and analytical technology, the ones used Pumps have good efficiency.

Claims (24)

1. A fluid pump, comprising:

   a pump body (10; 80); and

   a displacer (12; 82) which is adapted to be positioned at a first and at a second end position by means of a drive, the displacer and the pump body being implemented such that a pump chamber (14; 84) is defined therebetween, and said pump chamber (14; 84) being adapted to be fluid-connected to an inlet and to an outlet via a first opening (15; 85) and a second opening (16; 86a; 86b) which are not provided with check valves;

   said displacer (12; 82) being implemented in the form of a plate which is secured to the pump body (10; 80), and said pump body (10; 80) being provided with a recess defining the pump chamber (14; 84);

   characterized by

   an elastic buffer (13; 83) bordering on said pump chamber;

   said drive acting on the displacer (12; 82) substantially in the area of the first opening (15; 85);

   said displacer (12; 82) closing said first opening (15; 85) when it occupies its first end position and leaving said first opening free when it occupies its second end position; and

   said drive means moving the displacer so abruptly from the second to the first end position that a deformation of the buffer means is caused by the movement of said displacer.
2. A fluid pump according to claim 1, characterized in
   that the buffer (13; 83) is arranged in the pump body (10; 80).
3. A fluid pump according to claim 1 or 2, characterized in
   that the buffer is arranged in the displacer.
4. A fluid pump according to claim 2, characterized in
   that the buffer (13; 83) is implemented as a diaphragm by providing an area of reduced thickness in a wall of the pump body.
5. A fluid pump according to claim 3, characterized in
   that the buffer is implemented as a diaphragm by providing an area of reduced thickness in the displacer.
6. A fluid pump according to claim 1, characterized in
   that the buffer is formed by an elastic medium in the pump chamber.
7. A fluid pump according to claim 1, characterized in
   that the buffer is formed by the medium to be transmitted itself.
8. A fluid pump according to claim 1, characterized in that the displacer (82) is integrated in a second pump body (90) which is provided with portions of reduced thickness (89) so as to provide an elastic suspension for the displacer (82).
9. A fluid pump according to one of the claims 1 to 8, characterized in
   that the displacer (12; 82) closes the first opening passively or actively in both flow directions when the pump has been switched off.
10. A fluid pump according to claim 9, characterized in
    that active closing of the first opening is effected by the drive means which presses the displacer onto the first opening.
11. A fluid pump according to one of the claims 1 to 10, characterized in
    that the pumping direction of the pump is reversible by operating the displacer at a frequency above the resonant frequency of the buffer.
12. A fluid pump according to one of the claims 1 to 11, characterized in
    that the pump chamber (84) is implemented as a capillary gap.
13. A fluid pump according to claim 1, characterized in
    that the displacer and the buffer are implemented as different areas of a diaphragm which spans the pump body so as to define the pump chamber.
14. A check valve-free fluid pump, comprising:

    a pump body (110); and

    a flexible displacer (114; 124) which is attached to the pump body (110) in a fluid-tight manner along its circumference and which is movable with the aid of a drive means (116) into a first and a second end position;

    the pump body (110) and the flexible displacer (114; 124) defining a pumping space which is adapted to be fluid-connected to an inlet and to an outlet via a first opening (118) and a second opening (120) arranged in spaced relationship with said first opening;

    said displacer (114; 124) closing the first and the second opening when it occupies the first end position, and

    said displacer (114; 124) opening the first opening (118), while the second opening (120) is substantially closed, when said displacer (114; 124) is moved by said drive means (116) from said first end position into said second end position,

    characterized in

    that said drive means (116) acts on said flexible displacer (114; 124) essentially in the area of said first opening (118), and

    that said drive means moves the displacer so abruptly from the second end position into the first end position that a buffer volume is formed between the displacer and the pump body by an elastic deformation of the displacer.
15. A check valve-free fluid pump according to claim 14, characterized in
    that the pump body (110) is implemented in the form of a plate and the displacer (114) in the form of a diaphragm in such a way that said diaphragm rests on a main surface of said plate when the displacer (114) is at the first end position.
16. A check valve-free fluid pump according to claim 14, characterized in
    that the pump body (110) is implemented in the form of a plate and the displacer (124) in the form of a diaphragm in such a way that a capillary gap (126) is formed between a main surface of said plate and said diaphragm.
17. A check valve-free fluid pump according to claim 14, characterized in
    that the first and second openings (118, 120) are arranged in the pump body (110), the diaphragm (124) being provided with first and second areas of increased thickness directed towards the plate (110) and closing said first and second openings when the displacer (124) is at the first end position.
18. A check valve-free fluid pump according to claim 14, characterized in
    that the first and second openings (118, 120) are arranged in the pump body (110), raised portions being provided around said first and second openings (118, 120) in such a way that the diaphragm closes said first and second openings (118, 120) at the first end position.
19. A check valve-free fluid pump according to one of the claims 14 to 18, characterized in
    that, when the pump has been switched off, the displacer (114; 124) closes the first and second openings (118, 120) passively and/or actively.
20. A check valve-free fluid pump, comprising:

    a pump body (110); and

    a flexible displacer (136) which is attached to the pump body (110) in a fluid-tight manner along its circumference and which is movable with the aid of a drive means (116) to a first and a second end position,

    the pump body (110) and the flexible displacer (136) defining a pumping space which is adapted to be fluid-connected to an inlet and to an outlet via a first opening (118) and a second opening (120), and

    said displacer (136) closing the first opening (118) when it occupies its first end position and leaving said first opening (118) free when it occupies its second end position,

    characterized in

    that said first and second openings (118, 120) are arranged in spaced relationship with one another on different sides of a central axis of the displacer (136);

    that said drive means (116) acts on the flexible displacer (136) substantially in the area of the first opening (118) so as to move said displacer (136) into the first and into the second end position, and

    that said drive means moves the displacer so abruptly from the second end position to the first end position that a buffer volume is formed between said displacer and said pump body by an elastic deformation of the displacer.
21. A check valve-free fluid pump according to claim 20, characterized in
    that the pump body (110) is implemented in the form of a plate and the displacer (136) in the form of a diaphragm in such a way that a capillary gap is formed between a main surface of said plate and said diaphragm.
22. A check valve-free fluid pump according to one of the claims 14 to 21, characterized in
    that the pump body (110) and the displacer (114; 124; 136) are made of silicon.
23. A check valve-free fluid pump according to one of the claims 14 to 21, characterized in
    that the pump body (110) and the displacer (114; 124; 136) are produced by means of an injection moulding technique.
24. A check valve-free fluid pump according to one of the claims 14 to 23, characterized in
    that the pumping direction of the pump is reversible by operating the displacer (114; 124; 136) at a frequency above the resonant frequency.

Images