Dosing system with a cooling device

Abstract

The invention relates to a dosing system (1) for a dosing material having a nozzle (40), a feed channel (44) for dosing material, a discharge element (31), an actuator unit (10) that is coupled to the discharge element (31) and/or the nozzle (40) and has a piezo actuator (60), and a cooling device (2). The cooling device (2) comprises a supply device (21, 24, 26) for feeding a precooled cooling medium into a housing (11) of the dosing system (1). The cooling device (2) is configured for direct cooling of at least one subregion of the piezo actuator (60) and/or at least one subregion of a movement mechanism (14) coupled to the piezo actuator (60) by means of the precooled cooling medium.

Claims

1. A dosing system for a dosing material having a nozzle, a feed channel for the dosing material, a discharge element, an actuator unit that is coupled to the discharge element and/or the nozzle and has a piezo actuator, and a cooling device, the cooling device comprising: a supply device for feeding a precooled cooling medium into a housing of the dosing system, the cooling device being configured for direct cooling by means of the precooled cooling medium of at least one subregion of the piezo actuator and/or at least one subregion of a movement mechanism coupled to the piezo actuator.

2. The dosing system according to claim 1, wherein the piezo actuator comprises an actuator housing in which piezo elements are encapsulated.

3. The dosing system according to claim 1, wherein the cooling device is configured to control and/or to regulate the cooling of at least one subregion of the piezo actuator and/or at least one subregion of the movement mechanism coupled to the piezo actuator as a function of at least one state parameter.

4. The dosing system according to claim 3, wherein the at least one state parameter is a temperature in at least one subregion of the piezo actuator and/or a temperature in at least one subregion of the movement mechanism coupled to the piezo actuator.

5. The dosing system for a dosing material having a nozzle, a feed channel for the dosing material, a discharge element, an actuator unit that is coupled to the discharge element and/or the nozzle and has a piezo actuator, and a cooling device which is configured to cool at least one subregion of the piezo actuator and/or at least one subregion of a movement mechanism coupled to the piezo actuator in a controlled and/or regulated manner as a function of at least one state parameter, according to claim 3, wherein the at least one state parameter is a length of at least one subregion of the piezo actuator and/or a distance between the discharge element and the nozzle of the dosing system and/or a dosing amount.

6. The dosing system according to claim 3, wherein the dosing system comprises a temperature sensor and/or a strain sensor and/or a movement sensor for determining the state parameter.

7. The dosing system according to claim 1, wherein the cooling device is configured to control and/or regulate the cooling of at least one subregion of the piezo actuator separately.

8. The dosing system according to claim 1, wherein the precooled cooling medium is configured to cool at least one subregion of the piezo actuator and/or at least one subregion of the movement mechanism coupled to the piezo actuator to a target temperature.

9. The dosing system according to claim 1, wherein the cooling device for cooling the cooling medium comprises at least one cold generating device.

10. The dosing system according to claim 9, wherein the cold generating device is configured to cool the cooling medium to a predeterminable temperature.

11. The dosing system according to claim 9, wherein the cold generating device comprises a vortex tube.

12. The dosing system according to claim 1, wherein at least one subregion of the movement mechanism coupled to the piezo actuator comprises a heating device for heating at least one subregion of the movement mechanism coupled to the piezo actuator.

13. The dosing system according to claim 12, wherein the heating device is configured to keep at least one of the following state parameters constant in cooperation with the cooling device of the dosing system: a temperature in at least one subregion of the piezo actuator and/or in at least one subregion of the movement mechanism coupled to the piezo actuator, a length of at least one subregion of the piezo actuator, a distance between the discharge element and the nozzle, a dosing amount of the dosing material.

14. A method for operating a dosing system for the dosing of dosing material, the dosing system comprising a nozzle, a feed channel for the dosing material, a discharge element, an actuator unit that is coupled to the discharge element and/or the nozzle and has a piezo actuator, and a cooling device, a housing of the dosing system being fed a precooled cooling medium by means of a supply device of the cooling device, and at least one subregion of the piezo actuator and/or at least one subregion of a movement mechanism coupled to the piezo actuator being cooled directly by the cooling device by means of the precooled cooling medium.

15. A method for manufacturing a dosing system for the dosing of a dosing material having an actuator unit having a piezo actuator, the dosing system being equipped with a cooling device, the cooling device being equipped with a supply device for feeding a precooled cooling medium into a housing of the dosing system, and the dosing system being configured so that at least one subregion of the piezo actuator and/or at least one subregion of a movement mechanism coupled to the piezo actuator is cooled directly by means of the precooled cooling medium.

16. A dosing system for a dosing material having a nozzle, a feed channel for the dosing material, a discharge element, an actuator unit that is coupled to the discharge element and/or the nozzle and has a piezo actuator, and a cooling device which is configured to cool at least one subregion of the piezo actuator and/or at least one subregion of a movement mechanism coupled to the piezo actuator in a controlled and/or regulated manner as a function of at least one state parameter, wherein the at least one state parameter is a length of at least one subregion of the piezo actuator and/or a distance between the discharge element and the nozzle of the dosing system and/or a dosing amount.

17. The dosing system according to claim 11, wherein the vortex tube comprises an adjustable valve for regulating the temperature of the cooling medium.

Description

(1) The invention is explained in more detail in the following with reference to the attached figures using embodiments. The same components are provided with identical reference numbers in the various figures. The figures are usually not to scale. Shown are:

(2) FIG. 1 a sectional view of a dosing system according to an embodiment of the invention,

(3) FIGS. 2 to 4 parts of dosing systems depicted in section according to other embodiments of the invention,

(4) FIG. 5 parts of an actuator unit of a dosing system depicted in section according to an embodiment of the invention,

(5) FIG. 6 a sectional view of an encapsulated piezo actuator for a dosing system according to an embodiment of the invention,

(6) FIG. 7 a schematic representation of a cooling device for a dosing system according to an embodiment of the invention.

(7) A specific embodiment of a dosing system 1 according to the invention is now described with reference to FIG. 1. The dosing system 1 is depicted here in the usual intended location or position, for example, during operation of the dosing system 1. A nozzle 40 is located in the lower region of the dosing system 1, so that the drops of the medium are discharged downwards in a discharge direction R through the nozzle 40. Insofar as the terms below and above are used in the following, these details therefore always relate to such a, usually conventional, position of the dosing system 1. However, this does not rule out that the dosing system 1 can also be used in a different position in special applications and the drops are discharged laterally, for example. This is basically also possible depending on the medium, pressure and exact construction and activation of the entire discharge system.

(8) The dosing system 1 comprises, as essential components, an actuator unit 10 and a fluidic unit 30. In the embodiment of the dosing system 1 shown here, the actuator unit 10 and the fluidic unit 30 are fixedly connected to one another, for example, by means of a fixing screw 23. It should be noted, however, that the respective assemblies 10, 30 can also be implemented in the manner of plug-in coupling parts that can be coupled to one another to form a quick-release coupling. The actuator unit 10 and the fluidic unit 30 could then be coupled to one another without tools in order to form the dosing system 1.

(9) The actuator unit 10 substantially comprises all components that ensure the drive or movement of a discharge element 31, here a tappet 31, in the nozzle 40, thus, for example, a piezo actuator 60 and a movement mechanism 14, to be able to actuate the discharge element 31 of the fluidic unit 30, and similar components, as is explained in the following.

(10) In addition to the nozzle 40 and a supply line 44 of the medium to the nozzle 40, the fluidic unit 30 comprises all other parts that are in direct contact with the medium, and the elements that are required in order to assemble together the relevant parts which are in contact with the medium or to hold them in their position on the fluidic unit 30.

(11) In the embodiment of the dosing system 1 shown here, the actuator unit 10 comprises an actuator unit housing block 11 having two internal chambers, namely on the one hand, an actuator chamber 12 having a piezo actuator 60 located therein and on the other hand, an action chamber 13 into which the movable discharge element 31, here the tappet 31, of the fluidic unit 30 protrudes. Via a movement mechanism 14, which protrudes from the actuator chamber 12 into the action chamber 13, the tappet 31 is actuated by means of the piezo actuator 60 so that the fluidic unit 30 discharges the medium to be dosed in the desired amount at the desired time. The tappet 31 here closes a nozzle opening 41 and thus also serves as a closure element 31. However, since most of the medium is only discharged from the nozzle opening 41 when the tappet 31 is moving in the closing direction, it is referred to here as the discharge element 31.

(12) The piezo actuator 60 is connected in an electrical or signal manner to a control unit 90 of the dosing system 1 in order to be activated. The connection to this control unit 90 is via control cables 91, which are connected to suitable piezo actuator control connections 66, for example, suitable plugs. The two control connections 66 are each coupled to a contact pin 61 or to a respective connection pole of the piezo actuator 60 in order to activate the piezo actuator 60 by means of the control unit 90. In contrast to what is depicted in FIG. 1, the control connections 66 can be guided through the housing 11 in a sealed manner such that substantially no air can penetrate into the actuator chamber 12 from the outside in the region of the respectively implemented control connections 66, for example, in the context of a direct cooling, described in the following, of a number of subregions of the piezo actuator 60 using a precooled cooling medium. The piezo actuator 60, particularly the piezo actuator control connections 66, can, for example, be provided with a suitable memory unit (for example, an EEPROM or the like) in which information such as an article designation etc. or control parameters for the piezo actuator 60 are stored, the control parameters then being able to be read out by the control unit 90 to identify the piezo actuator 60 and activate in the appropriate way. The control cables 91 can comprise a plurality of control lines and data lines. However, since the basic activation of piezo actuators is known, this will not be discussed further.

(13) The piezo actuator 60 can expand and contract again in the longitudinal direction of the actuator chamber 12 in accordance with a wiring by means of the control device 90. The piezo actuator 60 can be inserted into the actuator chamber 12 from above. A spherical cap that is height-adjustable by means of a screwing movement can then serve as the upper abutment (not shown here), allowing precise adjustment of the piezo actuator 60 to a movement mechanism 14, here a lever 16. Accordingly, the piezo actuator 60 is mounted on the lever 16 in the downward direction via a pressure piece 20 which tapers at an acute angle at the bottom and which in turn rests on a lever bearing 18 at the lower end of the actuator chamber 12. The lever 16 can be tilted about a tilt axis K via this lever bearing 18, so that a lever arm of the lever 16 protrudes through a breakthrough 15 into the action chamber 13. At the end of the lever arm, this has a contact surface 17 pointing in the direction of the tappet 31 of the fluidic unit 30 coupled to the actuator unit 10, which presses on a contact surface 34 of a tappet head 33.

(14) It should be mentioned at this point that in the embodiment shown, it is provided that the contact surface 17 of the lever 16 is permanently in contact with the contact surface 34 of the tappet head 33, in that a tappet spring 35 presses the tappet head 33 against the lever 16 from below. The lever 16 rests on the tappet 31. However, there is no fixed connection between the two components 16, 31. In principle, however, it would also be possible for the tappet spring 35 to be at a distance between the tappet 31 and lever 16 in an initial or rest position, so that the lever 16 initially travels freely through a specific path section when it is pivoted downwards and thereby picks up speed and then with a high impulse strikes the tappet 31 or its contact surface 34 in order to increase the discharge impulse which the tappet 31 in turn exerts on the medium. In order to enable an almost constant pre-tensioning of the drive system (lever piezo actuator movement system), the lever 16 is pressed upwards by an actuator spring 19 at the end at which it comes into contact with the tappet 31.

(15) As mentioned, the fluidic unit 30 is connected to the actuator unit 10 by means of a fixing screw 23. The tappet 31 is supported by means of the tappet spring 35 on a tappet bearing 37, to which a tappet seal 36 connects downwards. The tappet spring 35 pushes the tappet head 33 away from the tappet bearing 37 in the axial direction upwards. A tappet tip 32 is thus also pushed away from a sealing seat 43 of the nozzle 40. That is, without external pressure from above on the contact surface 34 of the tappet head 33, in the rest position of the tappet spring 35, the tappet tip 32 is located at a distance from the sealing seat 43 of the nozzle 40. Thus, a nozzle opening 41 is also free or not closed in the rest state (non-expanded state) of the piezo actuator 60.

(16) The dosing material is fed to the nozzle 40 via a nozzle chamber 42 to which a feed channel 44 leads. On the other hand, the feed channel 44 is connected to a medium reservoir 46 by means of a reservoir interface 45. Furthermore, the fluidic unit 30 can also comprise a series of additional components that are usually used in dosing systems of this type, such as a frame part 47, a heating device 48 with heating connection cables 49 etc., to name just a few. Since the basic structure of dosing systems is known, for the sake of clarity, predominantly those components are shown here which relate at least indirectly to the invention.

(17) The dosing system 1 comprises a cooling device 2 having a supply device 21 in order to feed a precooled cooling medium to the housing 11 of the actuator unit 10. The supply device 21 here comprises a plug nipple 21 or a hose olive 21 as a coupling point for connecting a cooling medium supply line (not shown). In order to guide the cooling medium directly into the actuator chamber 12, thus, without directly cooling a region of the housing 11, the supply device 21 furthermore comprises an inflow channel 26 that follows the plug nipple 21. It should be pointed out that the plug nipple 21 and the inflow channel 26 are only representative of a number of further possible components of a supply device 21 here and also in the following figures. The inflowing cooling medium is directed in a targeted manner to a number of subregions of the piezo actuator 60 within the actuator chamber 12 by means of flow-directing elements (not shown here), so that the cooling medium is preferably blown directly onto the entire surface of the piezo actuator 60.

(18) In this embodiment, the actuator chamber 12 is continuously connected to the action chamber 13. Thus, the cooling medium flowing into the actuator chamber 12, for example, compressed air cooled to a target temperature, can be directed in a targeted manner by the cooling device such that a number of subregions of the movement mechanism are also cooled directly. The cooling device is configured to form a cooling medium flow within the actuator chamber 12 and the action chamber 13 and to direct it such that predominantly only the surfaces of the subregions to be cooled are acted upon with the cooling medium in a focused manner, preferably frontal.

(19) In contrast, other regions of the dosing system 1 that are not to be cooled directly, for example, an outer wall of the housing 11 or an inner wall of the actuator chamber 12 or the action chamber 13, are not blown upon with cooling medium in a focused manner. The latter regions are indeed passed or grazed by the cooling medium (“flowed along”), but there is no flow directly against them, so that the cooling medium does not develop its full cooling capacity here.

(20) The cooling medium leaves the housing by means of a discharge channel 27 of a discharge device 22. The discharge device 22 is configured here as part of the cooling device 2 according to the invention.

(21) Mechanical abrasion from the actuator chamber 12 or action chamber 13 can also be removed from the dosing system 1 by means of the cooling medium flow. In this embodiment of the invention, a number of subregions of the piezo actuator and the movement mechanism are directly cooled together, that is, as a unit, (“combined cooling”). Accordingly, the dosing system 1 here comprises only one cooling circuit.

(22) In principle, the piezo actuator 60 and the movement mechanism 14 can be cooled directly at a constant intensity when the dosing system is in operation (“unregulated cooling”). However, as shown in FIG. 1, it is preferred that the direct cooling is regulated as required by means of the control unit 90. Since the piezo actuator 60 and the movement mechanism 14 are cooled here together or as a unit, the control unit 90 only requires a single control and/or regulating circuit here. For example, the cooling could be regulated as a function of a temperature of the actuator surface (as a state parameter) in order to regulate the piezo actuator 60 to a constant length during operation. For this purpose, the piezo actuator 60 can comprise a number of temperature sensors, wherein the corresponding measured values are fed to the control unit 90 by means of temperature sensor connection cables. This is explained later with reference to FIGS. 3 and 6.

(23) The control unit 90 is coupled to a cold generating device, for example, a compression refrigeration system and/or a vortex tube (see FIG. 7), and controls this as a function of the state parameter so that the housing 11 is fed a sufficiently cooled cooling medium with such a volume flow and distributed in the housing 11 so that the at least one state parameter consistently corresponds to an assigned target value as a result of the direct cooling.

(24) In the embodiment shown in FIG. 1, due to the common cooling of the piezo actuator 60 and the movement mechanism 14, the movement mechanism 14 can be so strongly cooled by the cooling medium which, for example, is matched to a target temperature of the piezo actuator, that it is not possible to alone compensate for wear of parts of the movement mechanism 14 using the frictional heat that occurs. In order to nevertheless combine the advantage of a structural simplification of the cooling device with the highest possible dosing precision, a thermally induced expansion of a subregion of the movement mechanism 14 can be brought about in a targeted manner. For this purpose, the housing 11 comprises a heating device 51, here a heating cartridge 51, which can be activated by the control unit 90 by means of heating cartridge connection cables 92. The heat generated by the heating cartridge 51 leads, for example, by means of conduction and/or thermal radiation to heating at least one subregion of the movement mechanism 14, for example, the region of the lever 16 (“lever head”) resting on the tappet head 33 and/or to heating of the housing 11 and thus to a corresponding change in length of the housing material.

(25) In FIG. 1, a temperature sensor 52 is arranged in the housing 11 in the immediate vicinity of the heating cartridge 51 and is coupled to the control unit 90 by means of temperature sensor connection cables 86. The data determined by the temperature sensor 52 can be used to detect a temperature in a region of the housing 11. The control unit 90 can activate the heating cartridge 51 such that the housing 11, particularly a region of the housing 11 that encompasses the action chamber 13, is heated to a target temperature with the cooling medium despite the direct cooling of the movement mechanism 14 (“overlapping regulation”) to achieve a desired thermally induced expansion of the housing 11. The thermally induced expansion can, for example, lead to a length of the housing 11, which here corresponds to the vertical extension of the housing 11, increasing by a desired amount. As a result, a location or position of the movement mechanism 14 with respect to the piezo actuator 60 can also be (relatively) changed. This changes the position of the lever 16 in relation to the discharge element 31, since the distance between the lever bearing 18 and the piezo actuator 60 is also influenced thereby, and thus in turn the distance between the discharge element 31 and the nozzle 40 of the dosing system 1.

(26) In the region of the action chamber 13 is further arranged a motion sensor 53, for example, a thermally compensated Hall sensor 53, which interacts with a magnet in the region of the “lever head” (not shown) in order to determine a predominantly vertical movement of the “lever head” as a result of a deflection of the piezo actuator 60. The vertical movement of the “lever head” substantially corresponds to a (vertical) stroke of the tappet 31. The data from Hall sensor 53 (travel measurement per tappet stroke) are fed to control unit 90. Conclusions can be drawn about the actual distance between the tappet tip 32 and the nozzle 40 or nozzle seat 43 in the open state of the dosing system (as a state parameter) by means of this data. The control unit 90 can, for example, taking into account the data of the temperature sensor 52 and the Hall sensor 53, control the heating cartridge 51 so that a target stroke of the tappet 31 is kept stable despite wear of the components of the movement mechanism 14 and/or the tappet 31 even during the direct cooling of the movement mechanism 14.

(27) The housing 11 comprises a vertically running air-filled slot 50 in order to thermally decouple the heating cartridge 51 from the piezo actuator 60 to be cooled. The heat generated by the heating cartridge 51 is thus predominantly directed in the direction of the movement mechanism 14. Thermal decoupling of the actuator chamber 12 from the action chamber 13 can also be provided (FIG. 2), depending on the embodiment of the dosing system 1.

(28) FIG. 2 shows parts of a dosing system according to another embodiment of the invention. The fluidic unit here and also in FIGS. 3 and 4 corresponds to the structure according to the fluidic unit from FIG. 1, so that this assembly is only partially shown in the following for the sake of better clarity. The control unit and the corresponding cables for making contact with the piezo actuator or the heating cartridge and the temperature sensor in the housing are also not shown below or only partially shown in order to avoid repetitions.

(29) An essential difference to the embodiment according to FIG. 1 is that the cooling device 2 of the dosing system 1 here (FIG. 2) comprises two separately configured and activatable cooling circuits in order to cool the piezo actuator 60 directly, independently or separately from the movement mechanism 14. A first cooling circuit of the cooling device 2 is configured to cool the piezo actuator 60 directly, wherein the cooling circuit comprises a supply device 21 having an inflow channel 26 and a discharge device 25 interacting therewith having an outflow channel 27 in the lower region of the actuator chamber 12.

(30) In order to decouple the cooling of the piezo actuator 60 from the cooling of the movement mechanism 14, at least one O-ring 54 is arranged between a foot region of the piezo actuator 60, for example, a circular plate on which the piezo actuator 60 is fastened, and an inner wall of the actuator chamber 12. The O-ring 54 thus delimits the actuator chamber 12 towards the bottom and forms a barrier for the cooling medium. In this embodiment, the O-ring 54 is part of the cooling device 2. Due to the subdivision, a chamber is configured below the O-ring 54 in the region of the lever bearing 18, the chamber no longer being included in the cooling circuit of the actuator chamber 12. This chamber is connected to the action chamber 13 by means of the breakthrough 15 and is therefore regarded in this embodiment as part of the action chamber 13, thus, as a chamber 13 surrounding a movement mechanism 14 of the dosing system 1.

(31) The cooling device 2 here comprises a second, separate cooling circuit for the direct cooling of at least one subregion of the movement mechanism 14. For this purpose, the (expanded) action chamber 13 has its own supply device 24 having an inflow channel 26 for a precooled cooling medium and a discharge device 22 interacting therewith having an outflow channel 27.

(32) The cooling device 2 can be controlled by means of the control unit (not shown here) such that the two cooling circuits are separately supplied with cooling medium by means of the independently configured supply device 21 or 24. For example, the respective volume flow and the respective temperature of the supplied cooling medium can be adapted as required to a respective situation of the piezo actuator 60 or the movement mechanism 14. Less intense cooling of the movement mechanism 14 can lead to the frictional heat of the movement mechanism 14 alone being sufficient to compensate for wear.

(33) The housing 11 here further comprises a horizontal air-filled slot 50 in order to thermally decouple the piezo actuator 60, which is typically more strongly cooled than the movement mechanism 14, from the movement mechanism 14. Undesired thermal interactions between the two cooling circuits can be reduced in this way.

(34) FIG. 3 shows a further embodiment of a dosing system which, with regard to the cooling device, substantially corresponds to that from FIG. 1. However, the piezo actuator here comprises an actuator housing 62 in which a piezo stack is hermetically sealed. The wiring of the piezo actuator or the piezo stack takes place here by means of the two outer contact pins 61 (see also FIG. 6). The two contact pins 61 shown in the middle here are used to transmit the measured values of a number of temperature sensors of the piezo actuator or of the piezo stack from the actuator casing 62 to the control unit (not shown). For this purpose, the contact pins 61 are each connected to the control unit by means of temperature sensor connecting cables 86 on the one hand and to one or a plurality of temperature sensors (not shown) in the actuator casing 62 on the other hand.

(35) The embodiment shown in FIG. 4 substantially corresponds to the dosing system from FIG. 2. However, as already explained for FIG. 3, a piezo stack encapsulated in an actuator casing 62 is arranged in the actuator chamber 12 here as well. In this embodiment, by means of a first cooling circuit of the cooling device 2, cooling medium directly acts upon a number of subregions of a surface or the outside of the actuator casing 62 facing the actuator chamber 12. The precooled cooling medium, as said, acts upon at least one subregion of the movement mechanism 14 by means of a second cooling circuit of the cooling device 2.

(36) FIG. 5 shows in detail part of an actuator unit having an encapsulated piezo actuator for a dosing system according to an embodiment of the invention. The actuator casing 62 having the piezo stack encapsulated therein is arranged in the actuator chamber 12 such that the actuator casing 62 directly adjoins an inner side 80 of the wall 79 of the actuator chamber 12 at least in the region of bulges 82. Periodically, substantially horizontally running indentations 83 are arranged between the respective bulges 82 of the actuator casing 62.

(37) The cooling device 2 here comprises a cooling medium supply line 84 which is coupled to a pump 28 of a feed device 21. Alternatively, the cooling medium supply line 84 could also be coupled to an adjustable cooling air supply (not shown) of the supply device 21. To regulate the cooling output, the pump 28 can be activated by the control unit 90 by means of a control connection 29. In order to feed the cooling medium to the actuator chamber 12, the pump 28 is connected to an inflow channel 26 for cooling medium by means of the supply device 21.

(38) The inflow channel 26 of the cooling device 2 runs here directly along an outer side 81 of the chamber wall 79, that is, the inflow channel 26 is delimited by the outer side 81 of the chamber wall 79 and the housing 11. The inflow channel 26 has a number of breakthroughs 88 or openings 88 in the chamber wall 79 along the actuator chamber 12. A respective breakthrough 88 thus represents a connection between the inflow channel 26 and the actuator chamber 12.

(39) For direct cooling of a number of subregions of the actuator casing 62, the latter is positioned in the actuator chamber 12 such that in each case a breakthrough 88 between the inflow channel 26 and the actuator chamber 12 and a breakthrough 88′ interacting therewith (depicted here on the left) between the actuator chamber 12 and an outflow channel 27 are arranged in a horizontal plane with a single channel 83 in the actuator casing 62.

(40) The gaseous and/or liquid cooling medium flowing into the actuator chamber 12 through a respective breakthrough 88 from the inflow channel 26 is thus guided substantially horizontally along the actuator casing 62 along a respective channel 83, which is vertically delimited by the adjacent bulges 82, and finally arrives into the outflow channel 27 or, by means of the discharge device 25, into a cooling medium discharge line 85 of the cooling device 2. A number of subregions of the actuator casing 62 are thus cooled directly in this embodiment. In order to also effectively cool the encapsulated piezo stack, a heat-conducting medium can be arranged in the actuator casing 62, as is explained with reference to FIG. 6.

(41) FIG. 6 shows in detail a possible embodiment of an encapsulated piezo actuator for use in a dosing system. The piezoelectrically active material 67, thus, the piezo stack 67, is arranged between a cover 64 and a base 63 of the actuator casing 62 and is laterally surrounded by a fold-like jacket 74. The jacket 74 is fixedly connected to the cover 64 and the base 63 in order to hermetically seal off the piezo stack 67 from its surroundings. The cover 64 comprises four glass feedthroughs 65 (only one shown here), by means of which a contact pin 61 is guided hermetically sealed and electrically insulated from the interior of the actuator casing 62 to the outside of the actuator casing 62. A contact pin 61 is connected to an outer electrode 70 of the piezo stack 67, for example, soldered, to wire the piezo stack 67. A total of two outer electrodes 70 run on two opposite sides of the piezo stack 67 along its longitudinal extent between the two inactive head or foot regions 73 on the outside or surface 77 of the piezo stack 67.

(42) Four temperature sensors 78 are arranged in the actuator casing 62; three of them on the surface 77 of the piezo stack 67 along the longitudinal extent of the piezo stack 67 and a further one in measuring contact with the jacket 74 or the inner wall 74 of the actuator casing 62. A respective temperature sensor 78 can usually be connected to two contact pins 61 (not shown here) in each case in order to generate measured values or to transmit them to the control unit. To transmit the measurement signals of a plurality of temperature sensors 78 to the control unit, the individual sensor signals can also be placed on just one contact pin 61 and modulated in a suitable manner, provided that the temperature sensors 78 are bus-compatible IC temperature sensors.

(43) In the actuator casing 62, a strain gauge 87 is further arranged on the surface 77 of the piezo stack 67. The strain gauge 87 extends here substantially along the entire longitudinal extent of the encapsulated piezo stack 67, thus, between an inactive foot or head region 73. The corresponding measured values (state parameters) of the strain gauge 87 can be transmitted to the control unit of the dosing system by means of contact pins 61 (not shown). A further strain gauge 87 is arranged on the outside of the actuator casing 62, wherein the strain gauge 87 extends there between the base 63 and the cover 64 and can thus detect a total deflection, particularly also a temperature-related change in length, of the encapsulated piezo stack 67.

(44) In order to effectively cool the piezo stack 67 despite the encapsulation, the actuator casing 62 comprises a liquid and/or solid filling medium 75, which efficiently removes the heat generated during operation from the surface 77 and transfers it to a region of the actuator casing 62, the region being included in the direct cooling by means of the cooling device. The filling medium can also comprise a moisture suppressing medium. The actuator casing 62 further comprises an expansion region 76, for example, a gas bubble 76 or a gas-filled region 76.

(45) FIG. 7 shows schematically the structure of a cooling device 2 according to an embodiment of the dosing system for direct cooling of a number of subregions of the piezo actuator or the movement mechanism. The control unit 90 activates a cold generating device 55 of the cooling device 2, for example, a compression refrigeration machine 55, as a function of at least one state parameter of the dosing system 1 so that the cooling medium is cooled to a specific (first) temperature. The cooling medium, for example, compressed room air, is supplied to the refrigeration machine 55 by means of a cooling medium supply—KMZ. The cooling medium emerging from the refrigeration machine 55 has already been cooled to a temperature below the ambient temperature of the dosing system 1 and reaches a downstream vortex tube 57 of the cooling device 2 by means of suitable insulated lines.

(46) In order to cool the previously controlled cooling medium in a targeted manner to a final (target) temperature by means of the vortex tube 57, the vortex tube 57 comprises a controllable regulating valve 94 in the region of a hot air outlet HAW of the vortex tube 57. Both the temperature and the (volume) flow of the cooled cooling medium (“cold air component”) can be regulated by means of the valve 94. In principle, opening the valve leads to a reduction in the flow as well as the temperature of the cooled air emerging from the vortex tube 57. The cooled cooling medium leaves the respective vortex tube 57 at a cold air outlet of the vortex tube 57 in a direction SKM. A “hot air component” of the vortex tube is led away from the vortex tube 57 or dosing system 1 by means of the hot air outlet HAW. To regulate the volume flow of the cooling medium entering the vortex tube 57, a proportional valve 56 can be connected upstream of the vortex tube 57, the proportional valve being able to be activated by means of the control unit 90.

(47) In the embodiment of the cooling device 2 shown here, the cooling medium is introduced into the housing 11 of the dosing system 1 by means of a cooling medium supply line 84, which is coupled to the vortex tube 57 on the one hand and to a supply device 21 on the other hand, in order to jointly cool a number of subregions of the piezo actuator and of the movement mechanism (“combined cooling). A controllable pressure reducer 59 is provided here between the vortex tube 57 and the supply device 21.

(48) The actuators described above, the controllable compression refrigeration machine 55, the proportional valves 56, the pressure reducer 59 and the controllable regulating valves 94, can be used individually or in addition. The shown arrangement of the cooling circuit thus shows an almost maximum stage of extension in order to describe the individual components in their function.

(49) If the cooling device 2 comprises two separate cooling circuits other than shown here, a first vortex tube 57 can be provided for the needs-based cooling of the piezo actuator and a second vortex tube 57 for the needs-based cooling of the movement mechanism.

(50) The cooling medium is guided through the housing 11 by means of the cooling device 2 such that a number of subregions of the piezo actuator and the movement mechanism are cooled directly. The cooling medium, which may have warmed up as a result of the heat dissipation from the piezo actuator or movement mechanism, is then removed from the housing 11 by means of at least one discharge device 22 or a cooling medium discharge line 85 or is carried away from the actuator unit 10 in the region of a hot air outlet HAD. A further pressure reducer 59 is arranged here in the region of the hot air outlet HAD.

(51) The pressure reducers 59 are shown here as optional components of the cooling device 2. In principle, the proportional valve 56 is already configured to set, for example, reduce, the pressure in the cooling medium supply line 84 or in the cooling circuit via the enabled flow through the vortex tube 57. Furthermore, the flow of cooling medium through vortex tube 57 and the division into a hot air part and a cold air part also lead to a pressure reduction.

(52) The housing 11 comprises a heating cartridge 51 which can be controlled by means of the control unit 90 such that at least one subregion of the movement mechanism is heated to a (target) temperature. Furthermore, a number of temperature sensors 78, 52 are arranged in the actuator unit 10 in order to detect a temperature of at least one subregion of the piezo actuator or the movement mechanism. The corresponding data are fed to the control unit 90 as a state parameter of the dosing system.

(53) As a function of these or further state parameters, the control unit 90 can calculate or carry out temperature management of the dosing system in order to achieve the constant highest possible level of dosing precision. For this purpose, the control unit 90 can apply appropriate control signals to the individual components of the cooling device 2, thus, the refrigeration machine 55, the proportional valve 56, the vortex tube 57 or the regulating valve 94, the pressure reducer 59, the heating cartridge 51 and optionally further components.

(54) Finally, it is pointed out once again that the dosing systems described in detail above are merely embodiments which can be modified in the most varied of ways by the person skilled in the art without departing from the scope of the invention. For example, a single refrigeration machine can thus be coupled to a plurality of vortex tubes. Furthermore, the use of the indefinite article “a” or “an” does not exclude the possibility that the relevant characteristics can also be present several times.

LIST OF REFERENCE SYMBOLS

(55) 1 dosing system 2 cooling device 10 actuator unit 11 housing actuator unit 12 actuator chamber 13 action chamber 14 movement mechanism 15 breakthrough 16 lever 17 lever contact surface 18 lever bearing 19 actuator spring 20 pressure piece 21 supply device/actuator chamber 22 discharge device/action chamber 23 fixing screw 24 supply device/action chamber 25 discharge device/actuator chamber 26 inflow channel 27 outflow channel 28 pump 29 pump control connection 30 fluidic unit 31 tappet 32 tappet tip 33 tappet head 34 tappet contact surface 35 tappet spring 36 tappet seal 37 tappet bearing 40 nozzle 41 nozzle opening 42 nozzle chamber 43 sealing seat 44 feed channel 45 reservoir interface 46 medium reservoir 47 frame part 48 heating device fluidic unit 49 heating connection cable 50 slit/housing 51 heating cartridge actuator unit 52 temperature sensor/housing 53 Hall sensor 54 O-ring 55 refrigeration machine 56 proportional valve; throttle valve 57 vortex tube 59 pressure reducer 60 piezo actuator 61 contact pin 62 piezo actuator housing; actuator casing 63 base (actuator casing) 64 cover (actuator casing) 65 glass feedthrough 66 piezo actuator control connections 67 piezo stack 70 outer electrode 73 inactive region 74 jacket (actuator casing) 75 filling medium 76 expansion region 77 actuator surface 78 temperature sensor piezo actuator 79 chamber wall 80 inside of chamber wall 81 outside of chamber wall 82 bulge of actuator casing 83 indentation of actuator casing 84 cooling medium supply line 85 cooling medium discharge line 86 temperature sensor connection cable 87 strain gauge 88, 88′ breakthrough 90 control unit 91 control unit connection cable 92 heating cartridge connection cable 94 regulating valve vortex tube HAD hot air outlet dosing system HAW hot air outlet vortex tube K tilt axis KMZ cooling medium supply R discharge direction SKM flow direction cooling medium