IMPROVED MICROPUMP

Abstract

The micropump including a pump chamber which can be fluidly filled or emptied both by means of a passage opening and an inlet, the pump chamber being covered with a disk-shaped actuator so that the volume of the pump chamber can be changed by deflecting the actuator, the passage opening being arranged in a side of the pumping chamber opposite the actuator, and the inlet has a smaller or similar flow resistance compared to the through opening. An entrance to the passage opening can be closed by means of the deflected actuator, so that a valve is formed in the basic state, or closed by means of the undeflected actuator, so that a valve is formed in the basic state. The micropump can have a second pump chamber with an actuator and inlet, the passage opening of which is connected to that of the first pump chamber.

Claims

1. Micropump having a small housing size, comprising a pump chamber (21), which can be fluidically filled or emptied by means of a passage opening (4) as well as an inlet (51), wherein the pump chamber (21) is covered with a disk-shaped actuator (11; 11′), so that the volume of the pump chamber (21) can be changed by deflecting the actuator (11; 11′), wherein the passage opening (4) is arranged in a side (61) of the pump chamber (21) which is opposing to the actuator (11; 11′), and wherein the inlet (51) has, compared to the passage opening (4), a smaller or similar flow resistance, and wherein one entrance (31), with respect to the passage opening (4), can be closed by means of the deflected actuator (11), so that a valve is formed which is open in a basic state, or can be closed by means of the undeflected actuator (11′), so that a valve is formed which is closed in a basic state, characterized in that the micropump has a second pump chamber (22) with actuator (12; 12′) and inlet (52), the passage opening (4) of which being connected to the one of the first pump chamber (21).

2. Micropump according to claim 1, wherein the second pump chamber (12, 12′) is formed identical to the first pump chamber (11, 11′).

3. Micropump according to claim 1 or 2, wherein can be closed by means of the deflected actuator (11, 12), so that a valve which is open in an basic state is formed, wherein in a resting position, the actuator (11, 12) is spaced apart from the opposing side (61; 62) of the according pump chamber (21, 22), or is closed by means of the undeflected actuator (11′, 12′), so that a valve which is closed in an basic state is formed, wherein in a resting position, the actuator (11′, 12′) rests against the opposing side (61, 62) of the according pump chamber (21, 22), characterized in that an end stop (61′, 62′) is assigned to the actuator (11, 12; 11′, 12′), which mechanically limits the stroke of the actuator (11, 12; 11′, 12′).

4. Micropump according to claims 1 to 3, wherein its respective actuators (11, 12, 11′, 12′) can be driven by means of a rectangular wave, a sinusoidal wave, or a trapezoidal wave, wherein a phase shift different from 180° can be effected.

5. Micropump according to claim 4, wherein the pump comprises a control unit by means of which the actuators (11, 12, 11′, 12′) can be driven by means of a rectangular wave, a sinusoidal wave, or a trapezoidal wave, wherein a phase shift different from 180° can be effected between the two waves.

6. Apparatus according to any of the preceding claims, wherein both pump chambers (21, 22) are positioned (i) opposing one another or (ii) next to each other, and respectively fluidically connected to each other by the common passage opening (4), and/or wherein the passage opening (4) is arranged in the center of the according pump chamber's (21, 22) side (61, 62) which is opposing to the actuator (11, 12; 11′, 12′).

7. Micropump according to any of claims 1 to 6, wherein the undeflected actuator (11, 12) is spaced apart from the pump chamber's (21, 22) side (61, 62) opposing to the same, so that a pump chamber (21, 22) with a volume larger than zero is achieved.

8. Apparatus according to claim 3 and claim 7, wherein the end stop (61′, 62′) is formed by the side (61, 62) against which the actuator (11, 12) can be mechanically rested by means of control, such that the volume of the pump chamber can be minimized in a definable way.

9. Micropump according to any of claims 1 to 6, wherein the undeflected actuator (11′, 12′) rests against the pump chamber's (21, 22) side opposing to the same, so that a pump chamber (21, 22) with a volume of zero is achieved.

10. Micropump according to claim 9, wherein the end stop (61″, 62″) against which the actuator (11′, 12′) can be mechanically rested by way of control is located at the side of the actuator (11′, 12′) which is facing away from the pump chamber (21, 22), so that the volume of the pump chamber (21, 22) can be maximized in a definable way.

11. Micropump according to any of claim 8 or 10, wherein the same comprises a pump chamber (21, 22) according to definition in claim 8, as well as an end stop (61″, 62″) according to definition in claim 10.

12. Micropump according to any of claim 8 or 10, wherein the same comprises only one pump chamber (21) according to definition in claim 8, or only one pump chamber (21) according to definition in claim 10, or one pump chamber (21) with end stop (61″) according to definition in claim 11, wherein its usable volume is smaller or equal to the usable volume of the second pump chamber (22).

13. Micropump according to any of claims 8, 10 and 11, wherein the same comprises two pump chambers (21, 22) according to definition in claim 8, or two pump chambers (21, 22) according to definition in claim 10, or two pump chambers (21, 22) according to definition in claim 11.

14. Micropump according to any of the preceding claims, wherein the pump chamber's (21, 22) side (61), 62) which is opposing to the actuator (11, 12; 11′, 12′) and which comprises the passage opening has, at least in the region of the passage opening (4), the negative shape of the undeflected actuator (11′, 12′).

15. Micropump according to any of the preceding claims, wherein the inlet (51, 52) as well is located in the side (61, 62) which is opposing to the actuator (11, 12; 11′, 12′).

16. Micropump according to any of the preceding claims, wherein the pump chamber's (21, 22) side (61, 62) which is opposing to the actuator (11, 12; 11′, 12′) and which comprises the passage opening, has entirely the negative shape of the deflected actuator (11, 12) or of the undeflected actuator (11′, 12′).

17. Micropump according to any of the preceding claims, wherein a housing which comprises the actuators (11, 12; 11′, 12′) is not larger than 5 cm×2 cm×1 cm.

18. Micropump according to any of the preceding claims, wherein the same has at least on one of the actuators (11, 12; 11′, 12′) a sensor for the detection of impact of its pump chamber (21, 22) facing side.

19. Valve system for controlling a fluid flow, comprising the components according to any of the preceding claims, wherein the valve system comprises four stages which are formed by the inlet (51) and the first actuator (11; 11′), the first actuator (11; 11′) and the passage opening (4), the passage opening (4) and the second actuator (12; 12′), as well as the second actuator (12; 12′) and the inlet (52).

20. Method for operating a micropump according to definition in any of claims 1 to 19, characterized in that, originating from an initial state in which both actuators (11, 12; 11′, 12′) are controlled in such a way that the volumes of pump chambers (21, 22) are minimal and the according entrances (31, 32) to the passage opening (4) as well as the inlets (51, 52) are closed, a pumping cycle comprises the following steps: increasing the distance of the first actuator (11; 11′) to the side (61) opposing to the same, so that the volume of the first pump chamber (21) increases and the first inlet (51) as well as the first entrance (31) to the passage opening (4) are opened, so that fluid can flow through the first entrance (51) into the first pump chamber (21) and fill the same due to the thus formed underpressure; simultaneously reducing the distance of the first actuator (11; 11′) to the side (61) opposing the same and increasing the distance of the second actuator (12; 12′) to the side (62) opposing the same, so that also the second entrance (32) to the passage opening (4) is open, and the volume of the first pump chamber (21) is reduced, and, at the same time, the volume of the second pump chamber (22) is increased, so that the fluid can flow from the first pump chamber (21) via the common passage opening (4) into the second pump chamber (22), the first being emptied and the second being filled; reducing the distance of also the second actuator (12; 12′), so that the volume of the second pump chamber (22) is minimized and the fluid is emitted through the second inlet (52) due to the forming overpressure, and the pump arriving again in its initial state; so that fluid is transported into the first entrance (51), through both pump chambers (21, 22), and out of the second entrance (52).

21. Method according to claim 20 for the operation of a micropump having at least one end stop according to definition in any of claim 3, 8, 10, 11, 12 or 13, characterized in that the first actuator (11; 11′), in a situation when it moves towards the according end stop (61′, 61″, 62′, 62″) is controlled such that it mechanically contacts end stop (61′, 61″, 62′, 62″) so that its stroke is limited in a defined way.

22. Method according to claim 20 or 21 for the operation of a controllable micropump according to definition in any of claim 4 or 5, wherein both actuators (11, 11′, 12, 12′) are accordingly controlled by a rectangular wave, a sinusoidal wave, or a trapezoidal wave, their phase shift being between 70° and 120°.

23. Method according to any of claims 20 to 23, wherein the steps by means of changing the phase shift or by means of inversing the control sequence are run through in reverse order, so that fluid is transported into the second entrance (52), through both pump chambers (22, 21), and out of the first entrance (51).

24. Method according to any of claims 20 to 23, wherein the pump capacity per time interval corresponds to the product of volumes of the pump chambers (21, 22) and number of cycles per time interval.

25. Method according to any of claims 20 to 24, wherein both actuators (11, 12; 11′, 12′) are driven by means of a sinusoidal, trapezoidal, or rectangular voltage, the phase shift of which being 90°±20° or 270±20°, wherein the stroke of the actuator (11, 12; 11′, 12′) is limited to 75%±20%.

26. Method according to any of claims 20 to 25, wherein the actuators (11, 12; 11′, 12′) are operated at the resonance frequency or a second, third, or higher harmonic.

27. Usage of a micropump according to any of claims 1 to 19 as a multi stage valve system with four closures.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0098] The invention is explained below by way of example with reference to figures. It is shown by

[0099] FIG. 1 the micropump of a first variant in an idle state;

[0100] FIG. 2 this micropump according to the invention in an initial state which is at the same time the end of the emission process;

[0101] FIG. 3 this micropump according to the invention at the end of the suction process;

[0102] FIG. 4 this micropump according to the invention at the end of the shifting process;

[0103] FIG. 5 the micropump of a second variant in a resting position which is at the same time the end of the emission process;

[0104] FIG. 6 this micropump according to the invention at the end of the suction process;

[0105] FIG. 7 this micropump according to the invention at the end of the shifting process;

[0106] FIG. 8 this micropump according to the invention in a “normally-open-state”;

[0107] FIG. 9 the micropump of a third variant in a resting position which is at the same time the end of the emission process;

[0108] FIG. 10 this micropump according to the invention at the end of the suction process;

[0109] FIG. 11 this micropump according to the invention at the end of the shifting process;

[0110] FIG. 12 this micropump according to the invention in a “normally-open-state”;

[0111] FIG. 13 an embodiment of a micropump with two pump chambers, wherein only one pump chamber has an outer end stop;

[0112] FIG. 14 an embodiment of this micropump with an adjusting device;

[0113] FIG. 15 an example of the change in the flow rate and direction of conveyance when the phase shift of both actuators changes.

DETAILED DESCRIPTION

[0114] In FIG. 1, the micropump according to the invention is shown in an idle state. This is a “normally open variant” of the micropump according to the invention, in which the actuators do not close the entrances in the basic state, so that fluid can flow through the pump.

[0115] In the present case, the micropump is constructed symmetrically and is therefore suitable for conveyance in both directions. It has two pump chambers 11, 12. It also includes two inner end stops 61′, 62′; the inner sides 61, 62 of the two pump chambers 11, 12 serve this purpose.

[0116] Parts that are not essential for understanding the invention, such as electrical leads, seals and the like, have been omitted for reasons of clarity.

[0117] The idle state shown is characterized in that both actuators 11, 12 are in a resting position. In the exemplary embodiment, the actuators 11, 12 are designed as piezo disks which are applied to a membrane (black area). According to the definition, the two components each result in an actuator 11, 12.

[0118] Each actuator 11, 12 covers a pump chamber 21, 22, thus delimiting and defining its volume. If the deflection of an actuator 11, 12 changes, i.e. if the distance between the actuator 11, 12 and the respective side 61, 62 increases, this changes the volume of the respective pump chamber 21, 22, as will be shown below. In the center of each pump chamber 21, 22, namely on the side 61, 62 opposite the respective actuator 11, 12 which presently serves as an (inner) end stop 61′, 62′, an entrance 31, 32 to the passage opening 4 is positioned. The passage opening 4 fluidly connects the two pump chambers 21, 22 to one another.

[0119] Furthermore, an inlet 51, 52 is also present in each pump chamber 21, 22, which connects it to the adjacencies, and at the distal end of which, for example, a hose fixation or the like can be attached (not shown).

[0120] In FIG. 2, both actuators 11, 12 are shown in a deflected position. In the present case, this state is referred to as the “initial state”, which is at the beginning of each pump cycle of this variant of the micropump.

[0121] As can now be seen, the shape of the side 61, 62 opposite the respective actuator 11, 12 (“bottom” of the pump chamber) corresponds to the negative of the shape of the deflected actuator 11, 12. In this way, almost the entire amount of fluid (not shown) is pressed out of the two pump chambers 21, 22, and the dead volume is minimized.

[0122] The two sides 61, 62 also serve as inner end stops 61′, 62′; by mechanical contact of the actuator 11, 12 with the corresponding side 61, 62, the end positions of the actuators 11, 12 are mechanically determined, and the end positions are independent from the actuators insofar as it is only necessary to ensure that each actuator 11, 12 in the depicted minimum position is actually in contact with the respective end stop 61′, 62′ (side 61, 62).

[0123] The two entrances 31, 32 (reference numbers omitted) are closed by the actuators 11, 12 in the initial state. The two inlets 51, 52 are also closed by them.

[0124] In the present case, the two actuators 11, 12 are prevented from further movement (bulging in direction of the center of the micropump) by the corresponding inner end stop 61′, 62′ (sides 61, 62).

[0125] In FIG. 3, the state is shown as it appears at the end of the suction process. In this state, the first actuator 11 has relaxed, i.e. it has moved from the deflected position into its (in the present case flat) resting position. Actuator 12 further remains in the deflected position, in the present case in physical contact with its end stop 62′. By increasing the volume of the first pump chamber 21, a negative pressure is created. This leads to fluid flowing through inlet 51 into the pump chamber 21. It is clear that the actuator 11 could also swing further outwards in order to further increase the volume of the pump chamber 21 (not shown). However, a further, external end stop would then preferably be present (see FIGS. 5-8).

[0126] FIG. 4 shows the state at the end of shifting the fluid from the first pump chamber 21 into the second pump chamber 22. When the second actuator 12 begins to move out of its minimally deflected end stop position (see FIG. 3, “minimal” always means “most closely to the end stop”) in direction of its resting position, the second entrance 32 is first opened; by successively moving actuator 12 further, the second pump chamber 22 is gradually enlarged. By simultaneous, successive deflection of the first actuator 11 from the resting position to its minimally deflected position, the fluid is now pushed through the passage opening 4, which is open on both sides, until the first pump chamber 21 is emptied and its volume is minimized. In this position, the first actuator 11 closes the entrance 31 again.

[0127] Finally (not shown in FIG. 4) the second actuator 12 also moves back into its minimally deflected position, in the present case up to the corresponding end stop 62′ (side 62). Since the first actuator 11 has already closed the passage opening 4, the fluid can now only escape through inlet 52; the micropump conveys the fluid. One pumping cycle is complete, the two actuators 11, 12 are again in the initial position shown in FIG. 2, and the micropump is again in the defined initial state.

[0128] A conveying cycle thus comprises 3 “cycles”, as shown in FIGS. 2 to 4.

[0129] FIGS. 5 to 8 show a “normally closed” variant of the micropump according to the invention.

[0130] FIG. 5 shows the micropump in an idle state. In this state, both actuators 11′, 12′ rest on the respective sides 61, 62. The pump chambers 21, 22 (reference numbers see FIGS. 6 and 7) have a minimum volume. Sides 61, 62 also serve as inner end stops 61′, 62′.

[0131] At the end of the suction process, which is shown in FIG. 6, the first actuator 11′ has maximally moved away from the opposite side 61 and thus the end stop 61′. The volume of the first pump chamber 21 is at its maximum. The fluid has flowed in through inlet 51. Since the second actuator 12′ rests still flat on the side 62 and thus the end stop 62′, the passage opening 4 is closed there; fluid cannot therefore flow back from inlet 52.

[0132] The micropump according to the invention is shown in FIG. 7 at the end of the shifting process. Analogous to the shifting process of the “normally open” variant described above, the fluid was shifted from the first pump chamber 21 into the second pump chamber 22 here too. For this purpose, the distance between the first actuator 11′ and the side 61 or the end stop 61′ is successively reduced, while the distance between the second actuator 12′ is gradually increased until the state shown in FIG. 7 is obtained.

[0133] Subsequently, the second actuator 12′ also goes into its resting position again, so that the initial state shown in FIG. 5 results. Meanwhile, the volume of the second pump chamber 22 is reduced so that the fluid can only take the path out of the micropump through inlet 52.

[0134] Thus, the conveying cycle of this embodiment also comprises 3 “cycles”, as shown in FIGS. 5 to 7.

[0135] For the sake of completeness, FIG. 8 shows the positions of the two actuators 11′, 12′ of the second variant when this is in a “normally open” state. It is clear, however, that in the basic state, typically planar actuators can remain in said position only when energy is supplied. Thus, if such a state is desired as the basic state, the “normally open” variant described above is more advantageous.

[0136] The frequency of the micropump or the control of the actuators 11, 12, respectively, is, for example, 25 kHz, the actuators are then typically being operated in a harmonic of the first degree. The diameter of the preferably disk-shaped actuator is, for example, 12 mm.

[0137] FIGS. 9 to 12 show a further embodiment of a “normally closed” variant of the micropump according to the invention. On the outward-facing sides of the actuators 11′, 12′, a mechanical outer end stop 61′, 62′ is schematically shown. This prevents the respective actuator 11′, 12′ from moving freely (further) so that its maximum deflection (i.e. the deflection furthest away from the respective end stop) is mechanically specified. Sides 61, 62 serve as inner end stops 61′, 62′.

[0138] FIG. 9 shows the micropump in an idle state. In this state, both actuators 11′, 12′ rest on the respective sides 61, 62, but not against the respective external end stop 61″, 62″. The pump chambers 21, 22 (reference numbers see FIGS. 10 and 11) have a minimum volume.

[0139] At the end of the suction process, which is shown in FIG. 10, the first actuator 11′ has maximally moved away from the opposite side 61 and is in contact with outer end stop 61″. The volume of the first pump chamber 21 is at its maximum and defined by the outer end stop 61″, which specifies the end position for actuator 11′. The fluid has flowed in through inlet 51. Since the second actuator 12′ is still flat against the side 62 and thus against inner end stop 62′, the passage opening 4 is closed there; thus, fluid cannot flow back from inlet 52.

[0140] In FIG. 11, the micropump according to the invention is shown at the end of the shifting process. Analogous to the shifting process of the “normally open” variant described above, here too, the fluid was shifted from the first pump chamber 21 into the second pump chamber 22. For this purpose, the distance between the first actuator 11′ and the side 61 is successively reduced, while the distance between the second actuator 12′ is successively increased until the state shown in FIG. 11 is obtained, in which the end position of the second actuator 12′ is specified by the corresponding outer end stop 62″.

[0141] Subsequently (not shown) also the second actuator 12′ takes its resting position again, so that the initial state shown in FIG. 9 is obtained again. Meanwhile, the volume of the second pump chamber 22 is reduced so that the fluid can only take the path out of the micropump through inlet 52.

[0142] Thus, the conveying cycle of this embodiment also comprises 3 “cycles”, as shown in FIGS. 9 to 11.

[0143] For the sake of completeness, FIG. 12 shows the positions of the two actuators 11′, 12′ of this embodiment when being in a “normally open” state. It is clear, however, that in the basic state, typically planar actuators can only take said position when energy is supplied. Thus, if such a state is desired as the basic state, the “normally open” variant described above with “real” pump chambers is more advantageous.

[0144] FIG. 13 shows an embodiment of the micropump with two pump chambers 21, 22, only one pump chamber 21 having an inner end stop 61′ and an outer end stop 61″. The pump chamber 21 in the picture above has an actuator 11′ which, in the maximum deflection shown, rests against the outer end stop 61″. Actuator 12′, on the other hand, has no such inner or outer end stop. Since, when actuator 11′ is in operation, the volume it conveys is defined by the outer end stop 61″ and the inner end stop 61′, only this volume can be further conveyed by subsequent (downstream) actuator 12′. It must only be ensured that said second actuator 12′ and the associated pump chamber 22 are suitable and set up to actually convey a volume of this size. Preferably, the actuator can also convey an at least slightly (e.g. +5%, +10%, +20%) larger volume. In the present case, the conveying direction is from pump chamber 21 into pump chamber 22. It is indicated in FIG. 13 that actuator 12′ is larger and thicker than actuator 11′, so that a larger volume can also be conveyed with the same. It also has no end stop, because in the resting position shown, its side which points upward in the Figure and which faces pump chamber 22 is spaced apart from the pump chamber's 22 side which is opposite this side. So both sides are not in contact with one another; even if actuator 12′ is deflected, it will not lie flat against the side of the pump chamber 22. There is also no external end stop for actuator 12′.

[0145] The embodiment according to FIG. 14, in which the reference symbols have largely been omitted, has an adjusting device 7, shown schematically, for subsequent, simple adjustment of the position of maximum deflection of actuator 11′. This position is adjustable in direction of actuator 11′, whereby the end position of the same can be varied within certain limits.

[0146] FIG. 15 shows an example of the change of flow rate and conveying direction when the phase shift (also: phase difference) changes between the activation of both actuators. Both actuators are driven with a sinusoidal voltage of the same frequency (here: 300 Hz) and amplitude (here: 250 Vpp). The numbers on the Y-axis are only to be understood qualitatively in the present case, while the numbers on the X-axis represent concrete values for the phase shift of the voltage curves of the control voltages of both actuators. The diagram shows that with a phase shift of 0° or ±180°, the delivery rate becomes zero. In the first case, both actuators oscillate in unison, in the second case in push-pull.

[0147] With a phase shift of +90°, the delivery rate reaches a negative maximum. In this case, actuator 11, 11′ leads actuator 12, 12′; the conveying direction is then from inlet 51 to inlet 52. With a phase shift of −90°, the delivery rate reaches a positive maximum. In this case, actuator 11, 11′ follows actuator 12, 12′; the conveying direction is then from inlet 52 to inlet 51; consequently the conveying direction is exactly the opposite.

[0148] It can also be seen that by varying the phase shift around a value of ±90°, a reduced delivery rate occurs.

[0149] However, depending on the design, the positive or negative maximum can also be at other values, for example at ±70°, ±80°, ±100°, or ±110°. This can be the case if the two pump chambers are not completely identical, but are constructed slightly “asymmetrically”. This can be the case, for example, due to different volumes of the pump chambers, actuators that differ from one another, different flow resistances of the respective inlets, etc. Such differences may be intentional; however, they typically result from production-related variations of the respective components. However, the invention makes it possible to compensate for the disadvantageous result of such undesirable but unavoidable variations by adjusting the phase shift. Instead of cost-intensive measures to further improve, for example, the similarity of the actuators, the joining technology, or the manufacturing process, the delivery rate can be optimized by simply adapting the control of the actuators. In addition, subsequent variations, for example due to different aging, or variations that arise under different operating conditions (pressure, temperature, viscosity of the conveyed medium, . . . ), can be readjusted in situ, which would otherwise not be possible.

LIST OF REFERENCES

[0150] 11, 12, 11′, 12′ actuator [0151] 21,22 pump chamber [0152] 31,32 entrance [0153] 4 passage opening [0154] 51,52 inlet [0155] 61,62 side [0156] 61′,62′ end stop, inner end stop [0157] 61″,62″ end stop, outer end stop [0158] 7 adjusting device