DOSING SYSTEM WITH COOLING DEVICE

Description

[0001] The invention relates to a metering system for a metering substance comprising a nozzle, a feed channel for the metering substance, an ejection element, an actuator unit coupled to the ejection element and / or the nozzle with a piezoelectric actuator, and a cooling device. The invention further relates to a method for operating and a method for manufacturing such a metering system.

[0002] Dispensing systems of the type mentioned above are typically used to precisely dispense a medium, usually a liquid to viscous substance. In so-called "micro-dispensing technology," it is often necessary to apply very small quantities of a substance to a target surface with pinpoint accuracy and without contact, i.e., without direct contact between the dispensing system and the target surface. Such a non-contact method is frequently referred to as a "jet dispensing method." A typical example is the dispensing of adhesive dots, solder pastes, etc., during the assembly of printed circuit boards or other electronic components, or the application of converter materials for LEDs.

[0003] A key requirement is the highly precise delivery of the dosing agents to the target surface – that is, at the right time, in the right place, and in a precisely measured quantity. This can be achieved, for example, by dispensing the dosing agent drop by drop through a nozzle of the dosing system. In this process, the medium only comes into contact with the interior of the nozzle and a section, usually the front, of the ejection element of the dosing system. A preferred method is the ejection of individual droplets in a type of "inkjet" process, as used, among other things, in inkjet printers. The size of the droplets, or the amount of medium per droplet, can be predetermined as precisely as possible through the design and control of the nozzle, and the resulting effect. Alternatively, the dosing agent can also be sprayed in a jet.

[0004] To dispense the medium from the dosing system, a movable ejector element (usually a plunger) can be arranged in the nozzle of the dosing system. The ejector element can be pushed forward at a relatively high speed inside the nozzle towards a nozzle opening or outlet, thereby ejecting a droplet of the medium, which is then retracted.

[0005] Alternatively, the nozzle of the metering system itself can be moved in an ejection or retraction direction. To dispense the metering material, the nozzle and an ejection element located inside the nozzle are moved relative to each other. This relative movement can be achieved either solely by moving the outlet or nozzle, or at least partially by moving the ejection element.

[0006] The ejector element can typically be moved into a closed position by firmly engaging a sealing seat in the nozzle opening and remaining there temporarily. With more viscous metering media, it may also be sufficient for the ejector element to simply remain in the retracted position, i.e., away from the sealing seat, without any drop of the medium escaping.

[0007] The present invention can be used in all the aforementioned variants regardless of the specific ejection principle, i.e., in a jet process, an open ink-jet process, a classic closure element or a movable nozzle.

[0008] The movement of the ejector and / or nozzle is typically achieved using an actuator system within the metering system. To transmit the force generated by the actuator system to the ejector, the metering system typically includes a motion mechanism coupled to both the actuator system and the ejector. This motion mechanism can be implemented, for example, by means of a lever upon which the actuator system is mounted. The lever itself can rest on a lever bearing and be tiltable about a pivot axis so that the movement of the actuator system is transmitted to the ejector via a contact surface of the lever. Depending on the specific ejection principle, however, the motion mechanism can also be designed to transmit the force generated by the actuator system to move the nozzle.

[0009] The actuator system can be implemented in various ways, with piezoelectric actuators being the preferred choice, particularly in applications requiring highly precise dosing resolution. Piezoelectric actuators, also known as piezoelectric actuators, offer the advantage of very precise and, above all, rapid controllability compared to other types of actuators, such as hydraulically, pneumatically, and / or electromagnetically driven actuators. Advantageously, piezoelectric actuators are characterized by extremely short reaction times, which are typically significantly lower than those of other actuator principles. Another advantage is that piezoelectric actuators require comparatively little installation space within a dosing system compared to other types of actuators. Therefore, piezoelectric actuators offer an efficient solution for operating dosing systems, especially when highly precise dosing is required.

[0010] Despite these advantages, piezoelectric actuators are components that dissipate significant power, which can cause substantial heating of the piezoelectric material. Since piezoelectric actuators exhibit temperature-dependent behavior, heating of the actuator material can affect both the longitudinal expansion of the piezoelectric actuator in its resting (unexpanded) state and its displacement under voltage. In addition to the piezoelectric actuator itself, the components of the dispensing system's movement mechanism can also heat up due to frictional heat, especially under high-frequency dispensing requirements.

[0011] Thermally induced expansion of one or more of the aforementioned components can lead to an undesirable change in the stroke process of the ejector element, causing the dispensed quantity of material to increasingly deviate from the target value during operation of the dosing system. Consequently, the temperatures of the piezoelectric actuator and the movement mechanism can have a direct impact on the precision of the dosing system.

[0012] To counteract overheating of the piezoelectric actuator, the entire actuator can be surrounded by compressed air, as compressed air is readily available in most dispensing systems. The movement mechanism is not directly exposed to the airflow but is simply cooled by the exhaust air from the piezoelectric actuator. However, a disadvantage of this design is that as the ambient temperature of the dispensing system increases, the compressed air is no longer sufficient to dissipate enough heat from the piezoelectric actuator to keep it and other temperature-sensitive components of the system consistently below a critical temperature for precise operation. US Patent 2015 / 0300748 A1 describes a dispensing system in which a cooling fluid, such as air, can be introduced into the housing of the dispensing system.US Patent 2016 / 0339470 A1 describes a dispensing system in which air can be introduced into a housing of the dispensing system to cool a piezoelectric actuator. US Patent 2016 / 0136661 A1 describes a dispensing system in which two piezoelectric actuators in a housing of the dispensing system can be cooled by means of a cooling fluid. KR 101 150 139 B1 describes a dispensing system in which heat can be dissipated from a piezoelectric element by means of a heat pipe.

[0013] It is therefore an object of the present invention to provide a dosing system for a dosing substance, a method for operating and a method for manufacturing such a dosing system, with which the disadvantages described above can be avoided and with which the dosing precision of the dosing system is improved.

[0014] This problem is solved by a dosing system according to claim 1, a method for operating a dosing system according to claim 12 and a method for manufacturing a dosing system according to claim 13.

[0015] A metering system according to the invention for a liquid to viscous metering substance comprises at least one nozzle, a feed channel for the metering substance, an ejection element, an actuator unit coupled to the ejection element and / or the nozzle with at least one piezoelectric actuator for moving the ejection element and / or the nozzle, and a cooling device. In the following, the term plunger is used synonymously with an ejection element, without limiting the invention thereto.

[0016] The dispensing of the metering substance from the metering system according to the invention can be carried out in any of the ways described above; that is, the metering system is not limited to a specific ejection or operating principle. Accordingly, as is usually the case, a ejection element movable at a relatively high speed can be arranged in the nozzle of the metering system (particularly in the area of ​​the nozzle, e.g., shortly before the outlet opening) to eject the metering substance from the nozzle. Alternatively or additionally, as mentioned, an outlet opening of the metering system according to the invention can be designed to be movable. Nevertheless, for the sake of clarity, it will be assumed in the following that the metering substance is dispensed by means of a movable ejection element, e.g., a plunger. However, the invention is not intended to be limited to this.

[0017] The actuator unit comprises at least one piezoelectric actuator and a movement mechanism that functionally interacts with the piezoelectric actuator and, as explained above, may preferably include at least one lever and one lever bearing. The actuator unit is distinct from the fluidic unit of the metering system, which comprises the components that come into contact with the metering material, such as the feed channel, the nozzle, and the plunger.

[0018] The actuator unit's movement mechanism is designed to functionally couple the ejector element with the at least one piezoelectric actuator of the metering system. This coupling is achieved by transmitting the forces and movements exerted by the piezoelectric actuator, resulting in the desired movement of the ejector element to release the metering material from the nozzle. The movement mechanism thus represents a force-transmitting, preferably multi-part, coupling that is at least temporary, to convert the deflection of the piezoelectric actuator into a movement of the ejector element, preferably vertical. Preferably, the coupling between the movement mechanism and the ejector element is not a fixed coupling. This means that the two components are preferably not screwed, welded, glued, etc., together for coupling purposes.

[0019] According to the invention, the dosing system comprises a cooling device with a feed device for supplying a pre-cooled cooling medium into a housing of the dosing system, in particular into a housing of the actuator unit. The housing of the actuator unit encloses the actuator unit from the ambient atmosphere of the dosing system, i.e., it forms an enclosure for the actuator unit, and therefore comprises at least one piezo actuator and the movement mechanism of the dosing system.

[0020] The feed device according to the invention has a number of connection or coupling points for an (external) cooling medium supply line in a region of the housing, as well as a feed channel arrangement adjoining the (respective) coupling point and extending into an interior space of the housing. The feed device can further comprise a number of components for regulating a volume flow and / or pressure of the cooling medium flowing into the housing, e.g., a pump or a proportional valve, and optionally other components.

[0021] According to the invention, the cooling device is designed for the direct, predominantly selective cooling of at least a partial area of ​​the piezo actuator and / or the movement mechanism of the actuator unit coupled to the piezo actuator by means of the pre-cooled cooling medium. "Direct" cooling of a partial area means that the respective partial area, in particular its surface, is the focus of the cooling. Preferably, the respective partial area can be directly exposed to the pre-cooled cooling medium. According to the invention, the cooling of a partial area takes place within the housing itself, i.e., directly "on site." The cooling is therefore not "indirect," meaning that the housing or parts thereof are not cooled from the outside (e.g., by conduction).

[0022] According to the invention, the cooling device can selectively apply cooling medium to only a single sub-area, i.e., a limited area or section of a surface of the piezo actuator or the movement mechanism. Therefore, the cooling device can include flow-directing elements within the housing, e.g., separately controllable flow channels, guide vanes, fans, etc., to direct the cooling medium to a specific sub-area. Accordingly, there can be areas of the surface of the piezo actuator or movement mechanism that are not included in the sub-area to be cooled and are therefore excluded from direct cooling. However, it is preferred that a number of sub-areas, i.e., one or more sub-areas which together comprise substantially the entire surface of the piezo actuator or movement mechanism, are used.the components of the movement mechanism are directly exposed to the cooling medium, so that the invention is subsequently described, without limitation thereto, by reference to this embodiment.

[0023] Due to the selectivity of the cooling, only the parts of the piezo actuator or the movement mechanism that need to be cooled, e.g. their entire surface, are directly exposed to the cooling medium.

[0024] The invention does not cover the mere flow of the cooling medium to areas of the dosing system other than (partial) areas of the piezo actuator or the movement mechanism, e.g., an outer surface of the housing. Similarly, areas located inside the housing, e.g., the walls forming a chamber surrounding the piezo actuator (actuator chamber) and a chamber surrounding the movement mechanism, are not the target of direct cooling. These areas or surfaces of the dosing system, which are not encompassed by a section to be cooled, are therefore not specifically targeted by the cooling medium, but merely "passed by" it. This means that the cooling medium necessarily passes through these areas on its way from the feed device to an outlet opening in the housing, but the areas themselves are not the focus of direct cooling by the cooling device.

[0025] According to the invention, the cooling device can be configured to selectively cool only a number of sub-areas of one or more piezoelectric actuators. This means that the movement mechanism would not be affected by the direct cooling. Alternatively, the direct cooling could also be directed only at one or more sub-areas of the movement mechanism, whereby the piezoelectric actuator would not be included in the direct cooling. Advantageously, the piezoelectric actuator and the movement mechanism can thus be cooled separately by means of the cooling device according to the invention. Alternatively, the cooling device can also be configured to directly cool a number of sub-areas of the piezoelectric actuator and the movement mechanism as a single unit, as will be explained later.

[0026] In the context of the invention, a pre-cooled cooling medium is understood to mean that the cooling medium has a predetermined (target) temperature, at least at the time it enters the housing. The (target) temperature of the cooling medium is lower, and potentially significantly lower, than the ambient temperature of the dosing system due to cooling. This distinguishes the "true" cooling according to the invention, using a cooled cooling medium, from simply circulating compressed room air around the piezoelectric actuator for "cooling purposes." To achieve a specific (target) temperature, the cooling medium is subjected to cooling or heat removal before being fed into the housing. This means that heat or thermal energy is selectively extracted from the cooling medium, as described below, by means of a refrigeration unit within the cooling system.Preferably, the pre-cooled cooling medium can have a (target) temperature of at most 18°C, preferably at most 10°C, and particularly preferably at most 1°C at the time of entry into the housing.

[0027] Advantageously, the dosing system according to the invention enables the process heat generated during operation to be dissipated particularly effectively from the piezo actuator or movement mechanism. In contrast to simply circulating compressed ambient air around the piezo actuator, the "true" and targeted cooling according to the invention leads to a significant improvement in cooling performance, so that with the same volume flow rate of the cooling medium, considerably more heat energy per unit of time can be dissipated from a surface to be cooled directly. This allows the particularly temperature-sensitive components of the dosing system (e.g., piezo actuator and movement mechanism) to be cooled even at high ambient temperatures, thus preventing the undesirable thermally induced expansion of these components described above and ensuring consistently high precision of the dosing system.Thanks to its highly effective cooling system, the dosing system can operate at maximum dosing frequency even at high ambient temperatures. Furthermore, the cooling unit allows for the targeted and selective cooling of temperature-sensitive components within the dosing system, eliminating the need to cool the other components or the housing itself. This reduces the consumption of pre-cooled cooling medium.

[0028] In an inventive method for operating a metering system for dosing a dosing agent, wherein the metering system comprises a nozzle, a feed channel for the dosing agent, an ejection element, an actuator unit coupled to the ejection element and / or the nozzle with a piezoelectric actuator, and a cooling device, a pre-cooled cooling medium is supplied to the interior of a housing of the metering system, in particular a housing of the actuator unit, by means of a feed device of the cooling device. According to the invention, one or more sub-areas of the piezoelectric actuator are cooled directly by the cooling device using the pre-cooled cooling medium. Alternatively or additionally, at least a sub-area of ​​a movement mechanism of the actuator unit coupled to the piezoelectric actuator is cooled directly by the cooling device using the pre-cooled cooling medium, i.e., selectively or focused, by flowing or blowing the cooling medium onto it.Preferably, a number of sub-areas, which together comprise the surface of the piezo actuator and / or the movement mechanism, can be cooled directly. To directly cool a number of sub-areas, the cooling device can be controlled and / or regulated accordingly by means of a control and / or regulation unit coupled to the dosing system, as will be explained later.

[0029] In a method for manufacturing a dosing system for dispensing a dosing agent with an actuator unit comprising at least one piezoelectric actuator, the dosing system is equipped with a cooling device. The cooling device is fitted with a feed device for supplying a pre-cooled cooling medium into a housing of the dosing system. According to the invention, the dosing system, and in particular the cooling device, is designed such that at least a portion of the piezoelectric actuator and / or a movement mechanism coupled to the piezoelectric actuator can be directly cooled by means of the pre-cooled cooling medium during operation of the dosing system.

[0030] Further, particularly advantageous embodiments and developments of the invention result from the dependent claims and the following description, wherein the independent claims of a claim category may also be further developed analogously to the dependent claims and embodiments of another claim category, and in particular individual features of different embodiments or variants may be combined to form new embodiments or variants.

[0031] The at least one piezoelectric actuator of the dispensing system can comprise an actuator housing that is at least partially flexible, e.g., a folded metal bellows in which a number of piezoelectric elements are hermetically encapsulated. This means that the actual "active" piezoelectric actuator, preferably a monolithic piezoceramic multilayer actuator with a number of stacked layers of a piezoelectrically active material, can be arranged inside a separate actuator housing in such a way that the stack of piezoelectric elements (piezoelectric stack) is completely sealed off from the actuator chamber or the dispensing system. Since the actuator housing is permanently connected to the piezoelectric stack encapsulated therein, or since the two components form a functional unit, the actuator housing is considered a component of the piezoelectric actuator within the scope of the invention.

[0032] The actuator housing of the at least one piezoelectric stack is preferably designed such that, even during operation of the dosing system, i.e., when the piezoelectric stack is deflected, no substances can penetrate the actuator housing from the outside to the inside or vice versa. In particular, the actuator housing is designed to be impermeable to water or moisture in general. Due to the encapsulation, in this embodiment of the invention, at least a portion of an outer surface of the actuator housing, preferably its entire surface, facing away from the piezoelectric stack, is directly exposed to a flow of cooling medium.

[0033] To cool the encapsulated piezoelectric stack particularly efficiently, a thermally conductive medium surrounding the piezoelectric stack can be arranged within the actuator housing to dissipate heat from a surface of the stack. Preferably, the thermally conductive medium is designed such that heat is transferred from the piezoelectric stack surface to the actuator housing, e.g., a metal body, by conduction and / or convection. Preferably, the piezoelectric stack surface can represent a heat transfer surface for a heat source, with at least one (to be cooled) portion of the actuator housing being designed as a heat transfer surface for a heat sink. Alternatively or additionally, the actuator housing can also include a medium for moisture suppression.

[0034] Advantageously, a dosing system with at least one hermetically encapsulated piezoelectric stack allows the piezoelectrically active material to be almost completely shielded from harmful external (environmental) influences, especially moisture, even during operation, thus significantly improving the piezoelectric actuator's lifespan. The dosing system's highly effective cooling system ensures that the piezoelectric stack is adequately cooled despite the encapsulation, which can generate considerable heat during operation. This significantly increases both the precision and the (uninterrupted) operating time of the dosing system. Furthermore, a liquid or aqueous cooling medium can be advantageously used, as the hermetically sealed encapsulation prevents condensation on the piezoelectrically active material.

[0035] For the most efficient cooling possible, the cooling device can be configured to directly control and / or regulate the cooling of at least a sub-area of ​​the piezo actuator and / or the motion mechanism coupled to the piezo actuator by means of a control unit, depending on at least one state parameter of the dosing system generated as a result of operation. This process is also referred to as thermal control. Preferably, the dosing system is coupled to a control unit for this purpose. Preferably, a number of sub-areas, which together comprise, for example, the entire surface of the piezo actuator or the motion mechanism, can be combined into a single unit for control purposes and uniformly controlled depending on at least one state parameter. The invention is described below, without limitation, using this embodiment as an example.

[0036] The term "control" is used synonymously with "control" and / or "regulation" in the following. This means that even when referring to "control," the control process can encompass at least one regulation process. In regulation, a controlled variable (actual value) is generally continuously measured and compared to a reference variable (setpoint). Regulation typically occurs in such a way that the controlled variable is adjusted to match the reference variable. This means that the controlled variable (actual value) continuously influences itself within the control loop.

[0037] According to the invention, a state parameter can be, for example, a (surface) temperature in at least a sub-area of ​​the piezo actuator and / or a (surface) temperature in at least a sub-area of ​​the movement mechanism coupled to the piezo actuator and / or a temperature in at least a sub-area of ​​an outer surface of the housing ("external temperature"). For temperature determination, the dosing system can comprise one or more temperature sensors, which are preferably coupled to a control unit of the dosing system.

[0038] To monitor the temperature of the piezoelectric actuator spatially (with the highest possible resolution), multiple temperature sensors can be implemented along a longitudinal axis on the actuator surface. If the piezoelectric actuator has an actuator housing in which a piezoelectric stack is encapsulated, multiple temperature sensors can also be arranged in different areas of an inner and / or outer wall of the actuator housing. Alternatively or additionally, a number of temperature sensors can also be arranged in direct contact with at least one component of the movement mechanism, e.g., the lever.

[0039] Alternatively, a number of temperature sensors can be mounted on or in the housing in close proximity to a respective component to estimate or extrapolate the component's temperature. Furthermore, the temperature sensors can also be designed to determine the temperature of a specific sub-area of ​​the movement mechanism or the piezo actuator from a certain distance, e.g., using infrared temperature sensors. Preferably, a relevant state parameter, upon which the control is dependent ("control state parameter"), can correspond to a mean temperature or a maximum temperature of a number of sub-areas of the piezo actuator and / or movement mechanism.

[0040] Another state parameter can be the length of at least a portion of the piezoelectric actuator. As explained earlier, piezoelectric actuators, or the individual piezoelectric elements, can exhibit temperature-dependent expansion behavior. Therefore, to monitor the (operating) state of the piezoelectric actuator, at least one strain gauge can be attached to the actuator surface to monitor the absolute length and / or the dynamic change in length of the piezoelectric actuator. The strain gauge can be used to monitor the longitudinal strain of the entire actuator as well as a section thereof. The strain gauge can also be located inside an actuator housing (e.g., in the area of ​​an inner wall) and / or on the outer surface of the actuator housing.

[0041] Additionally or alternatively, the distance between the ejection element, preferably a plunger tip, and the nozzle or nozzle seat of the metering system in the open state can also be used as a state parameter to control the cooling. During continuous operation of the metering system, wear can occur, particularly in the area of ​​the plunger tip, which can cause the plunger to shorten. Furthermore, the individual components of the movement mechanism can heat up and expand due to friction. A thermally induced change in the actuator's length, resulting from its coupling with the movement mechanism, can also cause the actual position of the plunger tip to deviate from the target position.

[0042] To determine this state parameter, the dosing system can include at least one motion sensor, e.g., a magnetic sensor, for measuring the displacement of a moving component. Preferably, at least one thermally compensated Hall sensor can be arranged in a region of the housing such that the sensor can interact with a magnet of the plunger and / or the lever to perform a preferably vertical displacement measurement of the plunger or lever. Preferably, the position of the plunger tip in the closed state of the dosing system can be compared with a position in the open state to determine the actual movement of the plunger or plunger tip for dispensing the metering material.

[0043] Another additional or alternative state parameter can be the amount of dosing agent dispensed by the dosing system within a specific time interval. Particularly with high-frequency dosing and / or highly viscous media, the piezo actuator can heat up considerably due to the work it performs. Therefore, the flow rate of the medium, e.g., in the feed channel, can also be considered as a state parameter. To determine this state parameter, at least one flow sensor can be positioned in a section of the feed channel. Alternatively or additionally, a "learned" (dosing agent-specific) state parameter can be stored in the control unit or the dosing system.

[0044] It should be noted here that the basic concept of controlling and / or regulating the cooling of at least a sub-area of ​​the piezo actuator and / or the movement mechanism as a function of at least one state parameter is not limited to the dosing system according to the invention. Rather, the control concept constitutes an independent aspect of the invention.

[0045] Preferably, the control concept can also be used in dosing systems in which the piezo actuator and / or the movement mechanism are exposed to an uncooled cooling medium, e.g., compressed room air (i.e., not a pre-cooled cooling medium as defined in the invention), for cooling purposes. Preferably, the cooling of at least a portion of the piezo actuator and / or the movement mechanism, i.e., the flow around or onto a respective portion for cooling purposes, can also be controlled as a function of the length of at least a portion of the piezo actuator and / or the distance between the ejection element and the nozzle of the dosing system and / or the quantity of the dosing material.

[0046] The aforementioned state parameters provide essential insights into the current (operating) state of the actuator unit and can therefore be used for appropriate compensation measures within the framework of comprehensive temperature management of the dosing system. Preferably, the control, in particular the regulation of the direct cooling of at least a sub-area of ​​the piezo actuator and / or movement mechanism, can be implemented such that at least one state parameter requiring control in these sub-areas is kept stable within a non-critical range during operation of the dosing system, particularly even under load fluctuations of the piezo actuator, i.e., corresponds to a predetermined setpoint. Preferably, the setpoint is neither exceeded nor fallen below as a result of the control. Alternatively, the control can also be implemented such that the state parameter is continuously maintained within a setpoint range during operation.

[0047] For control purposes, a corresponding setpoint or target range can be assigned to each state parameter as its actual value; this setpoint is stored, for example, in the control unit. The same state parameter can have different setpoints in different areas of the actuator unit. For example, the temperature setpoint for the piezo actuator could be significantly higher than the temperature setpoint for the movement mechanism.

[0048] Preferably, the direct cooling of several sub-areas of the piezo actuator can be controlled such that the actuator surface temperature (as a setpoint) remains constant during operation of the dosing system, corresponding to the ambient temperature of the dosing system. This achieves "thermal constancy" of the piezo actuator, largely preventing thermally induced longitudinal expansion of the piezo actuator during operation.

[0049] In principle, a maximum permissible operating temperature for the piezo actuator can be set as a target value to achieve the highest possible dosing precision of the dosing system. Preferably, the current and / or expected power consumption of the actuator can be taken into account to determine the temperature target value. Due to the poor thermal conductivity of the piezo material typically used, significant load fluctuations in the piezo actuator, especially in the case of an encapsulated piezo actuator, can lead to the heat loss generated inside the piezo actuator or piezo stack not being dissipated quickly enough to the cooled surface of the piezo actuator or actuator housing. This can result in a temperature gradient developing from the core of the actuator or piezo stack to its outer surfaces or the actuator housing. Therefore, despite reaching the target temperature at the surface of the piezo actuator or piezo stack, the piezo actuator or piezo stack may still overheat.the length of the actuator housing can change. Preferably, the respective power consumption of the piezo actuator, which is stored, for example, in the control unit, can be taken into account in order to determine a "corrected" target temperature of the surface (of the piezo actuator or the actuator housing), which prevents longitudinal expansion of the entire piezo actuator even during dynamic load changes of the piezo actuator or the encapsulated piezo stack.

[0050] The longitudinal extension of the piezoelectric actuator, which, as mentioned, can be determined using strain sensors, could also be used as the setpoint. Preferably, the control, in particular the thermal control of the cooling of several sections of the piezoelectric actuator, can be implemented such that the piezoelectric actuator maintains a constant, predefined length during operation of the dosing system. Accordingly, an "output" length of the piezoelectric actuator at room temperature or a maximum tolerable length of the piezoelectric actuator could be used as the setpoint.

[0051] Alternatively or additionally, the direct cooling of several sub-areas of the movement mechanism (thermally) can be controlled to achieve the most constant and consistent (target) movement of the ejector element, particularly its tip, during operation of the metering system. Accordingly, a target value or range could be defined as the distance between a plunger tip and a nozzle insert or a nozzle sealing seat when the metering system is open, or as the distance traveled by the plunger tip per plunger stroke. It is also conceivable that a maximum permissible "external temperature" of the housing could be used as the target value.

[0052] To control direct cooling, the control unit can perform a virtually real-time comparison of at least one state parameter with its assigned setpoint. Preferably, a number of sub-areas can be uniformly controlled based on just one state parameter, while at least one other state parameter is continuously monitored by the control unit. Monitoring is useful, for example, when a particular state parameter is currently significantly below its assigned setpoint, so that control is not (yet) necessary. As soon as the actual value of the monitored state parameter approaches a setpoint, for example, due to changes in the actuator's operating conditions, this state parameter could also be taken into account for cooling control.Preferably, the respective state parameters, on which the direct cooling of a number of sub-areas depends, can change during the operation of the dosing system.

[0053] As part of the temperature management system, the cooling intensity can be controlled, for example, by regulating the volume flow of the pre-cooled cooling medium entering the housing. Consequently, the intensity with which a number of sub-areas are exposed to the cooling medium can also be controlled. Alternatively or additionally, the (target) temperature of the pre-cooled cooling medium upon entering the housing can also be controlled. For this purpose, the control unit can be coupled with a cooling device. Preferably, the intensity of the direct cooling can be dynamically adjusted (as needed) during operation of the dosing system. Furthermore, the precise location of the direct cooling can also be controlled. Preferably, the piezoelectric actuator and the movement mechanism can be supplied with cooling medium separately, as explained below.

[0054] The cooling device of the dosing system can be configured to directly cool several sections of the piezoelectric actuator and the motion mechanism together, i.e., as a single unit ("combined cooling"). Preferably, the cooling device comprises only a single cooling circuit with separate supply and discharge devices for the cooling medium, the cooling circuit encompassing both the actuator chamber and the chamber of the motion mechanism. This means that sections of the piezoelectric actuator and the motion mechanism are supplied with a cooling medium at the same (target) temperature. Preferably, the control of the direct cooling can be based on a state parameter of only one of the two components. For example, the direct cooling of the piezoelectric actuator and the motion mechanism could be controlled solely based on the surface temperature of the piezoelectric actuator.

[0055] For particularly efficient temperature management, the cooling device can also be configured to separately control and / or regulate the direct cooling of at least a sub-area of ​​the piezo actuator by means of the control unit, in particular separately or independently from the control and / or regulation of the direct cooling of at least a sub-area of ​​the movement mechanism coupled to the piezo actuator. Preferably, the cooling device can therefore comprise two separately designed, independently operable cooling circuits, each with separate supply and discharge devices, which can be individually supplied with the pre-cooled cooling medium. Preferably, the cooling circuit for cooling the piezo actuator can be designed separately, in particular (spatially) separate from a cooling circuit for cooling the movement mechanism. Accordingly, the control unit can also have two separate "cooling-control" or "cooling-regulating" circuits.-Control circuits" are included to separately detect and process the respective state parameters of the piezo actuator or the movement mechanism, i.e. to supply the respective cooling circuits with cooling medium and to direct the cooling medium to the respective areas to be cooled.

[0056] Preferably, on the one hand, a number of sub-areas of the piezo actuator, e.g. the entire actuator surface, can be cooled to a first target temperature by means of the cooling device in such a way that the most advantageous conditions for the operation of the actuator result or the dosing accuracy is increased.

[0057] Similarly, a number of sub-areas of the movement mechanism, e.g., a "head" of the lever that comes into contact with the plunger, can preferably be cooled to a second target temperature by means of the cooling device, which may differ from the first target temperature. The separate cooling of these sub-areas makes it possible to decouple the cooling of the movement mechanism from the often very dynamic cooling requirements of the piezoelectric actuator.

[0058] Preferably, the direct cooling of partial areas of the motion mechanism (thermally) can be controlled in such a way as to compensate for wear and tear on components of the motion mechanism and / or ejection element. For this purpose, it may be advantageous or even necessary to selectively utilize the heating of individual or multiple components of the dosing system resulting from its operation within the framework of temperature management. As mentioned, the motion mechanism can heat up, in particular, due to frictional heat. The plunger can heat up due to contact with a preheated medium in the area of ​​the plunger tip. Furthermore, the two components can also thermally influence each other through their at least temporary coupling.

[0059] Preferably, a thermally induced expansion of the lever, particularly in an area of ​​the "lever head", and / or a plunger head of the plunger can be used to compensate for a wear-related shortening of the plunger in the area of ​​the nozzle, in order to keep the target stroke of the plunger (as a state parameter) stable.

[0060] During operation of the metering system, the plunger, at least partially, particularly with its head, protrudes into a chamber of the metering system surrounding the movement mechanism, so that the plunger is "indirectly cooled" by the cooling medium used to cool the movement mechanism. Preferably, therefore, the movement mechanism can be cooled less intensively than the potentially very hot piezoelectric actuator due to the separate thermal control, in order to utilize the (intrinsic) heat present in the lever and / or plunger to maintain the desired stroke of the plunger. Particularly preferably, the control of the direct flow to the movement mechanism can be such that the desired stroke of the plunger is maintained even when at least parts of the ejection element are also "indirectly cooled."

[0061] Advantageously, the temperature management of the dosing system allows the extent and intensity of the cooling of the piezo actuator or movement mechanism to be constantly adapted to the current (operating) state of the actuator unit. In particular, load fluctuations of the piezo actuator can be taken into account in order to reduce the cooling power accordingly during periods of lower load on the actuator unit and thus reduce the consumption of cooling medium.

[0062] Decoupling the cooling of the piezo actuator and the movement mechanism can lead to a further reduction in cooling medium consumption. Furthermore, this also increases the scope for compensating for wear and tear on the movement mechanism, which can have a beneficial effect on the precision of the dosing system.

[0063] In contrast, a dosing system with "combined cooling" offers the advantage of a simplified cooling design and thus a reduction in the manufacturing costs of the dosing system, since only one common cooling circuit is required for the entire actuator unit. With this design, any wear and tear that occurs can also be compensated for, for example, by selectively heating the movement mechanism, as will be explained later.

[0064] Preferably, the pre-cooled cooling medium supplied to the cooling circuit(s) is designed, i.e., cold enough and present in sufficient quantity within the housing, to maintain a predefinable cooling capacity continuously during operation of the dosing system. Preferably, the (target) temperature of the cooling medium can be set by the control unit to such a low temperature that a (respective) setpoint value, as described above, is kept stable in at least a sub-area of ​​the piezo actuator and / or the movement mechanism coupled to the piezo actuator during operation as a result of direct cooling.

[0065] To cool the cooling medium to a predetermined (target) temperature, the cooling device includes a cooling unit. Preferably, the cooling device, in particular the supply device, is configured to provide the pre-cooled cooling medium to the actuator chamber and / or the chamber of the movement mechanism within the housing. Preferably, the cooling device is further configured to distribute the pre-cooled cooling medium within the housing as needed. Preferably, the pre-cooled cooling medium also has a specific (target) temperature when it comes into contact with the surface of a number of sub-areas of the piezoelectric actuator or the movement mechanism.

[0066] To direct the incoming cooling medium from a (respective) supply device as precisely as possible to the area(s) to be cooled and subsequently to a discharge device in the housing, the cooling device can include flow-directing elements within the housing, e.g., separately controllable flow channels, guide vanes, fans, etc. Preferably, the cooling device therefore comprises at least components for cooling a cooling medium to a (target) temperature, providing the cooling medium in the housing at a (target) temperature, directing the cooling medium in the housing to a number of areas of the piezo actuator and / or the movement mechanism, discharging the cooling medium from the housing, and optionally feeding it back to the cooling device.

[0067] Preferably, the cooling device for cooling the cooling medium can comprise any type of "active" cooling source. The cooling source is preferably designed to actively remove heat energy from a substance, e.g., a cooling medium, in order to actively "generate" cold. Therefore, the cooling device can preferably comprise at least one cooling source.

[0068] The cooling device can be designed separately, i.e., not as an integral part of a single dosing system. Preferably, the cooling device can interact with several dosing systems. To supply the pre-cooled cooling medium to the housing, the cooling device can be connected to at least one connection point of the housing via a cooling medium supply line from the cooling unit, e.g., a temperature-insulated flexible line.

[0069] According to the invention, the cooling device, according to a first embodiment, is configured to cool the cooling medium to a specific absolute (setpoint) temperature. Preferably, the operation of the cooling device can take place regardless of the temperature and / or humidity of the ambient air of the dosing system or the cooling device. This means that the temperature of the cooling medium can not only be reduced relative to an ambient temperature by means of the cooling device, but can also be set to any desired value, i.e., as required for the operation of the dosing system. Preferably, the cooling device can utilize the principle of a refrigeration machine (as a cooling source). For example, the cooling device could comprise at least one compression refrigeration system.Preferably, such a refrigeration machine can be configured to supply two or more separate dosing systems with cooled refrigerant. Suitable refrigerants include liquid and / or gaseous media, with refrigerants having a high heat capacity being preferred.

[0070] Alternatively or additionally, the cooling device could utilize the principle of thermoelectric cooling. Preferably, the cooling device can therefore include at least one Peltier element (as a cooling source).

[0071] Preferably, compressed and (actively) cooled air can be used as the cooling medium, since this can be provided with relatively little effort and is compatible with the hygroscopic properties of live (unencapsulated) piezoelectric actuators. Therefore, in another embodiment of the invention, the cooling device can comprise at least one vortex tube (as a cooling source) for cooling the cooling medium to a specific (target) temperature. Preferably, the temperature of the cooled air exiting the vortex tube can be controlled by means of an adjustable control valve in the region of a hot air outlet of the vortex tube. Alternatively or additionally, a volume flow rate of the air flowing into a vortex chamber of the vortex tube can also be adjusted to provide a required quantity of pre-cooled cooling medium, e.g., by means of a proportional valve upstream of the vortex tube. Preferably, the control valve or...The proportional valve of each vortex tube is controlled by the control unit so that the cooling medium is supplied to the housing at a (target) temperature. The quantity of pre-cooled cooling medium supplied by a single vortex tube is preferably sufficient for the direct cooling of the temperature-sensitive components of an actuator unit.

[0072] Particularly preferably, the refrigeration device according to a further embodiment can comprise a refrigeration machine, e.g., a compression refrigeration system, and at least one downstream vortex tube interacting with it. Preferably, the cooling device can also comprise more than one, i.e., at least two, different cooling sources. In particular, the multiple cooling sources can be configured to be controlled separately. Preferably, a pre-tempered or pre-cooled cooling medium can be cooled to a final (target) temperature by means of the vortex tube. As a result of this interaction, the cooling medium can also be cooled to temperatures below the "lowest possible" cooling temperature of a refrigeration machine.

[0073] According to the invention, the cooling device's refrigeration unit ensures that a sufficiently large quantity of adequately cooled cooling medium is always present in the housing to maintain one or more state parameters within a non-critical target range in several sub-areas during operation of the dosing system. Particularly when a refrigeration unit is combined with a vortex tube, a very wide or deep cooling control range can be achieved. This allows the dosing system to operate at maximum dosing frequency even under unfavorable ambient conditions, such as particularly high temperatures, while simultaneously ensuring high dosing precision.

[0074] To further improve dosing accuracy, at least one part of the actuator unit's movement mechanism coupled with the piezo actuator can include a controllable heating device for heating at least one part of the movement mechanism.

[0075] The heating device can be implemented as part of the movement mechanism, e.g. in the form of a heating coil in or on the lever.

[0076] Alternatively or additionally, the housing of the actuator unit can include at least one heating device, controllable by the control unit, for heating at least a partial area of ​​the movement mechanism. Preferably, the partial area can be heated to a predeterminable temperature by conduction. The heating device, e.g., a heating cartridge or a heating coil, can be thermally decoupled from the piezo actuator, e.g., by means of an insulating, air-filled slot in the housing between the heating device and the piezo actuator.

[0077] Preferably, the housing, particularly in an area between the heating cartridge and the thermal break, can include at least one temperature sensor. As is generally the case with dosing systems of this type, a heating device for heating the nozzle or the dosing material in the nozzle area can also be provided.

[0078] Preferably, the heating device is designed to maintain, in conjunction with the cooling device of the dosing system, one or more state parameters of the dosing system as constant as possible during operation in a number of sub-areas of the piezo actuator and / or movement mechanism, preferably within the range of a respective setpoint. Preferably, the heating device and the cooling device of the dosing system can interact in such a way that a (setpoint) temperature in at least one sub-area of ​​the piezo actuator and / or the movement mechanism coupled to the piezo actuator, and / or a length of the piezo actuator, and / or a distance between the ejection element and the nozzle in the open state of the dosing system, and / or a quantity of dosing material during the dispensing process is predominantly constant during operation of the dosing system.

[0079] Preferably, the heating and cooling effects can be coordinated by the control unit in such a way that at least one "control state parameter" is maintained within a target range as efficiently as possible during operation of the dosing system. Preferably, the control unit can include a "heating control circuit" to control the heating device separately, in particular independently of the cooling device.

[0080] Preferably, the heating and cooling devices can be operated in parallel, at least temporarily, meaning that a number of sub-areas can be heated and cooled simultaneously ("overlapping control"). Preferably, the "overlapping control" is implemented in such a way that the consumption of heating energy or cooling medium is minimized, i.e., the heating and cooling devices do not operate continuously at full load against each other. For example, in a dosing system with "combined cooling," the cooling device could be controlled to achieve a target temperature in a specific area of ​​the actuator surface. Additionally, the heating device can be controlled to heat a number of sub-areas of the movement mechanism (and, via conduction, also the ejection element or plunger) to a (higher) target temperature in order to maintain a setpoint for the stroke of the ejection element.

[0081] Alternatively or additionally, the heating device can also be controlled to achieve a desired thermally induced expansion in a region of the housing, particularly in a region of the housing encompassing the chamber of the movement mechanism. Preferably, the thermally induced expansion of at least one region of the housing can be carried out in such a way that a setpoint for the stroke of the ejector element is kept stable during operation of the dosing system.

[0082] Advantageously, the possibility of wear compensation can be further improved by means of a separately controllable heating device, for example, by compensating for a shortening of the ejector element or plunger through targeted heating or controlled thermal expansion of individual sections of the movement mechanism, or indirectly also of the plunger and / or the housing. Thus, the plunger tip can always be positioned at an initial or target distance to the nozzle when the metering system is open, so that the amount of metering material dispensed per plunger stroke remains constant. At the same time, the heating device is designed and arranged in the metering system in such a way that the relevant operating parameters of the piezoelectric actuator (e.g., the actuator temperature or length) can also be kept within a non-critical range.

[0083] Indeed, the aforementioned advantages can also be utilized in the "combined cooling" system, enabling the desired thermal expansion of several sub-areas of the movement mechanism to be achieved despite direct exposure to a potentially very cold cooling medium. Thus, consistently high precision in the dispensing of the metering system can be achieved despite a simplified design. Furthermore, the slight, controlled interaction ("overlapping control") between the heating and cooling devices can advantageously contribute to increased rigidity or constancy of a state parameter of the metering system against external disturbances.

[0084] The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments. The same components are designated with identical reference numerals in the various figures. The figures are generally not to scale. They show: Figure 1 a cross-sectional view of a dosing system according to an embodiment of the invention, Figures 2 to 4 Parts of dosing systems shown in section according to other embodiments of the invention, Figure 5 Parts of an actuator unit of a dosing system shown in cross-section according to an embodiment of the invention, Figure 6 a sectional view of an encapsulated piezo actuator for a dosing system according to an embodiment of the invention, Figure 7 a schematic representation of a cooling device for a dosing system according to an embodiment of the invention.

[0085] Based on the Figure 1A specific embodiment of a dosing system 1 according to the invention will now be described. The dosing system 1 is shown here in its usual intended position, e.g., during operation. In this configuration, a nozzle 40 is located in the lower region of the dosing system 1, so that the drops of the medium are ejected downwards through the nozzle 40 in an ejection direction R. Therefore, wherever the terms "bottom" and "top" are used below, they always refer to such a generally common position of the dosing system 1. However, this does not preclude the possibility that the dosing system 1 can also be used in a different position in specific applications, with the drops being ejected laterally, for example. Depending on the medium, pressure, and the precise design and control of the entire ejection system, this is also fundamentally possible.

[0086] The dosing system 1 comprises, as essential components, an actuator unit 10 and a fluid unit 30. In the embodiment of the dosing system 1 shown here, the actuator unit 10 and the fluid unit 30 are permanently connected to each other, e.g., by means of a fixing screw 23. However, it should be noted that the respective assemblies 10 and 30 can also be implemented as interlocking plug-in couplings to form a quick-release coupling. In that case, the actuator unit 10 and the fluid unit 30 could be coupled together without tools to form the dosing system 1.

[0087] The actuator unit 10 essentially comprises all components that provide for the drive or movement of an ejection element 31, here a plunger 31, in the nozzle 40, i.e. e.g. a piezo actuator 60 and a movement mechanism 14 to actuate the ejection element 31 of the fluidic unit 30 and similar components, as will be explained below.

[0088] The fluidic unit 30 comprises, in addition to the nozzle 40 and the supply line 44 of the medium to the nozzle 40, all other parts that are in direct contact with the medium, as well as the elements required to assemble the parts in contact with the medium or to hold them in position on the fluidic unit 30.

[0089] In the embodiment of the dosing system 1 shown here, the actuator unit 10 comprises an actuator unit housing block 11 with two internal chambers: firstly, an actuator chamber 12 containing a piezoelectric actuator 60, and secondly, an action chamber 13 into which the movable ejection element 31, here the plunger 31, of the fluidic unit 30 projects. Via a movement mechanism 14, which projects from the actuator chamber 12 into the action chamber 13, the plunger 31 is actuated by the piezoelectric actuator 60 such that the fluidic unit 30 ejects the medium to be metered in the desired quantity at the desired time. The plunger 31 closes a nozzle opening 41 and thus also serves as a closing element 31. However, since most of the medium is only ejected from the nozzle opening 41 when the plunger 31 moves in the closing direction, it is referred to here as an ejection element 31.

[0090] To control the piezo actuator 60, it is electrically or via signal technology connected to a control unit 90 of the dosing system 1. The connection to this control unit 90 is made via control cables 91, which are connected to suitable piezo actuator control terminals 66, e.g., suitable connectors. The two control terminals 66 are each coupled to a contact pin 61 or to a respective terminal of the piezo actuator 60 in order to control the piezo actuator 60 by means of the control unit 90. Unlike in Figure 1As shown, the control connections 66 can be sealed and routed through the housing 11 in such a way that essentially no outside air can penetrate into the actuator chamber 12 in the area of ​​the respective control connections 66, e.g., as part of the direct cooling of a number of sub-areas of the piezo actuator 60 with a pre-cooled cooling medium, as described below. The piezo actuator 60, in particular the piezo actuator control connections 66, can be equipped, for example, with a suitable storage unit (e.g., an EEPROM or the like) in which information such as an article designation, etc., or control parameters for the piezo actuator 60 are stored. This information can then be read by the control unit 90 to identify the piezo actuator 60 and control it appropriately. The control cables 91 can comprise several control lines and data lines. However, since the basic control of piezo actuators is known, it will not be discussed further here.

[0091] The piezo actuator 60 can expand and contract longitudinally within the actuator chamber 12 according to a circuit controlled by the control unit 90. The piezo actuator 60 can be inserted into the actuator chamber 12 from above. A spherical cap adjustable in height by a screw movement (not shown here) can then serve as the upper abutment, enabling precise adjustment of the piezo actuator 60 to a movement mechanism 14, in this case a lever 16. Accordingly, the piezo actuator 60 is supported downwards by a pressure piece 20 tapering at an acute angle on the lever 16, which in turn rests on a lever bearing 18 at the lower end of the actuator chamber 12. Via this lever bearing 18, the lever 16 can be tilted about a tilting axis K, so that a lever arm of the lever 16 projects through an opening 15 into the action chamber 13.At the end of the lever arm, it has a contact surface 17 pointing towards the plunger 31 of the fluidic unit 30 coupled to the actuator unit 10, which presses against a contact surface 34 of a plunger head 33.

[0092] It should be mentioned here that in the illustrated embodiment, the contact surface 17 of the lever 16 is permanently in contact with the contact surface 34 of the plunger head 33, by means of a plunger spring 35 pressing the plunger head 33 downwards against the lever 16. The lever 16 rests on the plunger 31, but there is no fixed connection between the two components 16 and 31. However, it would also be possible, in principle, for the plunger spring 35 to be in its initial or rest position, with a gap between the plunger 31 and the lever 16. This would allow the lever 16 to initially travel freely through a certain section of its path as it pivots downwards, accelerating in the process, and then impact the plunger 31, or rather its contact surface 34, with a high impulse, thereby increasing the ejection impulse that the plunger 31 then delivers to the medium.In order to enable an almost constant preload of the drive system (lever-piezo actuator motion system), the lever 16 is pushed upwards at the end where it comes into contact with the plunger 31 by an actuator spring 19.

[0093] As mentioned, the fluidic unit 30 is connected to the actuator unit 10 by means of a fixing screw 23. The plunger 31 is supported on a plunger bearing 37 by means of the plunger spring 35, to which a plunger seal 36 is attached below. The plunger spring 35 pushes the plunger head 33 away from the plunger bearing 37 in an axial direction upwards. Thus, a plunger tip 32 is 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 plunger head 33, the plunger tip 32 is located at a distance from the sealing seat 43 of the nozzle 40 when the plunger spring 35 is in its rest position. Thus, in the rest state (unexpanded state) of the piezo actuator 60, a nozzle opening 41 is also free or unblocked.

[0094] The metering medium is supplied to the nozzle 40 via a nozzle chamber 42, to which a feed channel 44 leads. The feed channel 44 is, in turn, connected to a medium reservoir 46 by means of a reservoir interface 45. Furthermore, the fluidic unit 30 can comprise a number of additional components that are commonly used in metering 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 metering systems is known, for the sake of clarity, primarily those components that at least indirectly relate to the invention are shown here.

[0095] The dosing system 1 comprises a cooling device 2 with a feed device 21 for supplying a pre-cooled cooling medium to the housing 11 of the actuator unit 10. The feed device 21 includes a plug nipple 21 or a hose olive 21 as a coupling point for connecting a cooling medium supply line (not shown). To direct the cooling medium directly into the actuator chamber 12, i.e., without directly cooling any area of ​​the housing 11, the feed device 21 further includes an inlet channel 26 connected to the plug nipple 21. It should be noted that the plug nipple 21 and the inlet channel 26 are shown here and in the following figures only as representatives of a number of other possible components of a feed device 21.The inflowing cooling medium is directed within the actuator chamber 12 by means of flow-directing elements (not shown here) to a number of sub-areas of the piezo actuator 60, so that preferably the entire surface of the piezo actuator 60 is directly blown with the cooling medium.

[0096] 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, e.g., compressed air cooled to a target temperature, can be directed by the cooling device in such a way that a number of sub-areas of the movement mechanism are also directly cooled. The cooling device is designed to form and direct a flow of cooling medium within the actuator chamber 12 and the action chamber 13 in such a way that predominantly only the surfaces of the sub-areas to be cooled are exposed to the cooling medium in a focused manner, preferably frontally.

[0097] In contrast, other areas of the dosing system 1, which are not intended to be directly cooled, e.g., an outer wall of the housing 11 or an inner wall of the actuator chamber 12 or the action chamber 13, are not directly cooled by the cooling medium. These latter areas are passed over or grazed by the cooling medium ("flowed over"), but not directly cooled, so the cooling medium does not achieve its full cooling capacity here.

[0098] The cooling medium leaves the housing by means of a discharge channel 27 of a discharge device 22. The discharge device 22 is designed here as part of the cooling device 2 according to the invention.

[0099] Preferably, mechanical abrasion can also be removed from the actuator chamber 12 or action chamber 13 of the metering system 1 by means of the cooling medium flow. In this embodiment of the invention, a number of sub-areas of the piezo actuator and the movement mechanism are thus cooled directly together, i.e., as a single unit ("combined cooling"). Accordingly, the metering system 1 here comprises only one cooling circuit.

[0100] In principle, the piezo actuator 60 and the movement mechanism 14 can be cooled directly at a constant intensity during operation of the dosing system ("unregulated cooling"). However, as described in Figure 1It is shown, preferably, that the direct cooling is controlled as required by the control unit 90. Since the piezo actuator 60 and the movement mechanism 14 are cooled together or as a single unit, the control unit 90 requires only a single control loop. For example, the cooling could be controlled as a function of the actuator surface temperature (as a state parameter) to maintain the piezo actuator 60 at a constant length during operation. For this purpose, the piezo actuator 60 can include a number of temperature sensors, with the corresponding measured values ​​being supplied to the control unit 90 via temperature sensor connection cables. This will be shown later using the Figures 3 and 6 explained.

[0101] The control unit 90 is equipped with a refrigeration device, e.g. a compression refrigeration system and / or a vortex tube (see Figure 7), coupled and controls these depending on the state parameter in such a way that a sufficiently cooled cooling medium is supplied to the housing 11 with such a volume flow and distributed in the housing 11 in such a way that at least one state parameter permanently corresponds to an assigned setpoint as a result of the direct cooling.

[0102] At the in Figure 1In the illustrated embodiment, due to the combined cooling of the piezo actuator 60 and the motion mechanism 14, the motion mechanism 14 may be cooled so significantly by the cooling medium, which is, for example, adjusted to a target temperature of the piezo actuator, that wear compensation of parts of the motion mechanism 14 using only the generated frictional heat is not possible. To nevertheless combine the advantage of a simplified cooling design with the highest possible metering precision, a thermally induced expansion of a portion of the motion mechanism 14 can be deliberately induced. For this purpose, the housing 11 includes a heating device 51, in this case a heating cartridge 51, which can be controlled by the control unit 90 via heating cartridge connection cables 92. The heat generated by the heating cartridge 51, for example,by means of conduction and / or thermal radiation to a heating of at least a partial area of ​​the movement mechanism 14, e.g. the area of ​​the lever 16 resting on the plunger head 33 ("lever head") and / or to a heating of the housing 11 and thus to a corresponding change in length of the housing material.

[0103] In Figure 1A 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 control the heating cartridge 51 so that the housing 11, in particular a region of the housing 11 encompassing the action chamber 13, is heated to a set temperature despite the direct cooling of the movement mechanism 14 by the cooling medium ("overlapping control") in order to achieve a desired thermally induced expansion of the housing 11. The thermally induced expansion can, for example, lead to an increase in the length of the housing 11, which here corresponds to the vertical extent of the housing 11, by a desired amount. This can also be used to adjust the position or orientation of the housing 11.The position of the movement mechanism 14 relative to the piezo actuator 60 can be changed. This changes the position of the lever 16 relative to the ejection element 31, as the distance of the lever bearing 18 to the piezo actuator 60 is also affected, and thus in turn the distance between the ejection element 31 and the nozzle 40 of the metering system 1.

[0104] In the area of ​​the action chamber 13, a motion sensor 53, e.g., a thermally compensated Hall sensor 53, is arranged, which interacts with a magnet in the area of ​​the "lever head" (not shown) to determine a predominantly vertical movement of the "lever head" resulting from a deflection of the piezo actuator 60. The vertical movement of the "lever head" essentially corresponds to a (vertical) stroke of the plunger 31. The data from the Hall sensor 53 (displacement measurement per plunger stroke) are supplied to the control unit 90. Using this data, conclusions can be drawn about the actual distance between the plunger tip 32 and the nozzle 40 or nozzle seat 43 in the open state of the metering system (as a state parameter). The control unit 90 can, for example,Taking into account the data from the temperature sensor 52 and the Hall sensor 53, the heating cartridge 51 is controlled in such a way that a target stroke of the plunger 31 is kept stable despite wear of the components of the movement mechanism 14 and / or the plunger 31, even during direct cooling of the movement mechanism 14.

[0105] The housing 11 includes a vertically extending, air-filled slot 50 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 directed predominantly towards the movement mechanism 14. Depending on the embodiment of the dosing system 1, thermal decoupling of the actuator chamber 12 from the action chamber 13 can also be provided ( Figure 2 ).

[0106] In Figure 2 Parts of a dosing system according to another embodiment of the invention are shown. The fluidic unit corresponds here and also in the Figures 3 and 4the fluidic unit according to its structure Figure 1 Therefore, for the sake of clarity, this assembly will only be shown partially below. The control unit and the corresponding cables for connecting the piezo actuator or heating cartridge and the temperature sensor in the housing are also not shown below, or only partially shown, to avoid repetition.

[0107] A significant difference from the embodiment according to Figure 1 consists of the fact that the cooling device 2 of the dosing system 1 is located here ( Figure 2The cooling device 2 comprises two separately designed and controllable cooling circuits to directly cool the piezo actuator 60 independently or separately from the movement mechanism 14. A first cooling circuit of the cooling device 2 is designed to directly cool the piezo actuator 60, wherein the cooling circuit includes a supply device 21 with an inlet channel 26 and a cooperating discharge device 25 with an outlet channel 27 in the lower region of the actuator chamber 12.

[0108] 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 base area of ​​the piezo actuator 60, e.g., a circular plate to which the piezo actuator 60 is attached, and an inner wall of the actuator chamber 12. The O-ring 54 thus delimits the actuator chamber 12 at 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 this subdivision, a chamber forms below the O-ring 54 in the area of ​​the lever bearing 18, which is no longer encompassed by the cooling circuit of the actuator chamber 12. This chamber is connected to the action chamber 13 by means of the opening 15 and is therefore considered, in this embodiment, as part of the action chamber 13, i.e., as a chamber 13 surrounding a movement mechanism 14 of the metering system 1.

[0109] The cooling device 2 here comprises a second, separate cooling circuit for the direct cooling of at least a partial area of ​​the movement mechanism 14. For this purpose, the (extended) action chamber 13 has its own supply device 24 with an inlet channel 26 for a pre-cooled cooling medium and a cooperating discharge device 22 with an outlet channel 27.

[0110] The cooling unit 2 can be controlled by the control unit (not shown here) so that the two cooling circuits are supplied separately with cooling medium via the independently designed supply units 21 and 24, respectively. For example, the respective flow rate and temperature of the supplied cooling medium can be adjusted as needed to the specific situation of the piezo actuator 60 or the movement mechanism 14. Less intensive cooling of the movement mechanism 14 can mean that the frictional heat generated by the movement mechanism 14 alone is sufficient to compensate for wear.

[0111] The housing 11 also includes a horizontal air-filled slot 50 to thermally decouple the piezo actuator 60, which is typically cooled more intensively than the movement mechanism 14, from the movement mechanism 14. This reduces undesirable thermal interactions between the two cooling circuits.

[0112] In Figure 3 Another embodiment of a dosing system is shown, which, with regard to the cooling device, is essentially the same as the one described above. Figure 1 This corresponds to the previous design. However, the piezo actuator here comprises an actuator housing 62 in which a piezo stack is hermetically encapsulated. The piezo actuator and the piezo stack are connected via the two outer contact pins 61 (see also...). Figure 6The two contact pins 61 shown in the center are used to transmit the measured values ​​of a number of temperature sensors of the piezo actuator or the piezo stack from the actuator housing 62 to the control unit (not shown). For this purpose, the contact pins 61 are each connected on one side to the control unit via temperature sensor connection cables 86 and on the other side to one or more temperature sensors in the actuator housing 62 (not shown).

[0113] The in Figure 4 The illustrated embodiment essentially corresponds to the dosing system from Figure 2 However, here too, as already mentioned for Figure 3As explained, a piezoelectric stack encapsulated in an actuator housing 62 is arranged in the actuator chamber 12. In this embodiment, a first cooling circuit of the cooling device 2 directly supplies a number of sub-areas of a surface, or rather the outer surface of the actuator housing 62 facing the actuator chamber 12, with cooling medium. As mentioned, a second cooling circuit of the cooling device 2 allows at least a sub-area of ​​the movement mechanism 14 to be supplied with the pre-cooled cooling medium.

[0114] Figure 5Figure 1 shows in detail a portion of an actuator unit with an encapsulated piezoelectric actuator for a dosing system according to an embodiment of the invention. The actuator housing 62 with the encapsulated piezoelectric stack is arranged in the actuator chamber 12 such that the actuator housing 62 borders directly on an inner surface 80 of the wall 79 of the actuator chamber 12, at least in the area of ​​protrusions 82. Periodically arranged, essentially horizontally extending indentations 83 are provided between the respective protrusions 82 of the actuator housing 62.

[0115] The cooling device 2 comprises a cooling medium supply line 84, which is coupled to a pump 28 of a supply 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 capacity, the pump 28 can be controlled by the control unit 90 via a control connection 29. To supply the cooling medium to the actuator chamber 12, the pump 28 is connected to a cooling medium supply channel 26 via the supply device 21.

[0116] The inlet channel 26 of the cooling device 2 runs directly along an outer surface 81 of the chamber wall 79; that is, the inlet channel 26 is bounded by the outer surface 81 of the chamber wall 79 and the housing 11. The inlet channel 26 has a number of openings 88 in the chamber wall 79 along the actuator chamber 12. Each opening 88 thus forms a connection between the inlet channel 26 and the actuator chamber 12.

[0117] For the direct cooling of a number of sub-areas of the actuator shell 62, it is positioned in the actuator chamber 12 such that a through-hole 88 between inlet channel 26 and actuator chamber 12 and a cooperating through-hole 88' (shown here on the left) between actuator chamber 12 and an outlet channel 27 are arranged in a horizontal plane with a single channel 83 of the actuator shell 62.

[0118] Thus, the gaseous and / or liquid cooling medium flowing into the actuator chamber 12 from the inlet channel 26 through a respective opening 88 is guided essentially horizontally along the actuator shell 62 along a respective channel 83, which is vertically bounded by the adjacent bulges 82, and finally reaches the outlet channel 27 or, via the discharge device 25, a cooling medium drain 85 of the cooling device 2. In this embodiment, a number of sub-areas of the actuator shell 62 are therefore directly cooled. In order to also effectively cool the encapsulated piezoelectric stack, a thermally conductive medium can be arranged in the actuator shell 62, as shown in the figure. Figure 6 will be explained.

[0119] Figure 6Figure 1 shows in detail a possible embodiment of an encapsulated piezo actuator for use in a dispensing system. The piezoelectrically active material 67, i.e., the piezo stack 67, is arranged between a lid 64 and a base 63 of the actuator housing 62 and is laterally surrounded by a pleated sheath 74. The sheath 74 is firmly connected to the lid 64 and the base 63 to hermetically seal the piezo stack 67 from its environment. The lid 64 includes four glass feedthroughs 65 (only one is shown here) through which a contact pin 61 is hermetically sealed and electrically insulated from the interior of the actuator housing 62 to the outside of the actuator housing 62. To connect the piezo stack 67, a contact pin 61 is connected to an outer electrode 70 of the piezo stack 67, e.g., by soldering.A total of two external electrodes 70 run on two opposite sides of the piezo stack 67 along its longitudinal extent between the two inactive head and foot regions 73 on the outside and surface 77 of the piezo stack 67.

[0120] Four temperature sensors 78 are arranged in the actuator housing 62; three of them on the surface 77 of the piezoelectric stack 67 along the longitudinal extent of the piezoelectric stack 67, and another in measuring contact with the sheath 74 or the inner wall 74 of the actuator housing 62. Typically, each temperature sensor 78 can be connected to two contact pins 61 (not shown here) to generate measured values ​​or transmit them to the control unit. For transmitting the measurement signals of a plurality of temperature sensors 78 to the control unit, the individual sensor signals can also be placed on only one contact pin 61 and modulated appropriately, provided that the temperature sensors 78 are bus-compatible IC temperature sensors.

[0121] A strain gauge 87 is arranged on the surface 77 of the piezo stack 67 within the actuator housing 62. The strain gauge 87 extends essentially along the entire longitudinal extent of the encapsulated piezo stack 67, i.e., between an inactive base and 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 via contact pins 61 (not shown). Another strain gauge 87 is arranged on the outside of the actuator housing 62, extending between the base 63 and the cover 64, and thus capable of detecting the total deflection, and in particular temperature-induced changes in length, of the encapsulated piezo stack 67.

[0122] To effectively cool the piezoelectric stack 67 despite the encapsulation, the actuator shell 62 comprises a liquid and / or solid filling medium 75, which efficiently dissipates the heat generated during operation from the surface 77 and transfers it to a region of the actuator shell 62 that is directly cooled by the cooling device. The filling medium can also include a moisture-repellent medium. The actuator shell 62 further comprises an expansion region 76, e.g., a gas bubble 76 or a gas-filled region 76.

[0123] Figure 7Figure 1 schematically shows the structure of a cooling device 2 according to an embodiment of the metering system for directly cooling a number of sub-areas of the piezo actuator or the movement mechanism. The control unit 90 controls a refrigeration unit 55 of the cooling device 2, e.g., a compression refrigeration machine 55, depending on at least one state parameter of the metering system 1, such that the cooling medium is cooled to a specific (first) temperature. The cooling medium, e.g., compressed room air, is supplied to the refrigeration machine 55 via a cooling medium supply unit KMZ. The cooling medium exiting the refrigeration machine 55 has already been cooled to a temperature below the ambient temperature of the metering system 1 and reaches a downstream vortex tube 57 of the cooling device 2 via suitable insulated lines.

[0124] To cool the pre-tempered cooling medium to a final (target) temperature using the vortex tube 57, the vortex tube 57 includes a controllable regulating valve 94 in the area of ​​a hot air outlet HAW of the vortex tube 57. The valve 94 allows for the regulation of both the temperature and the (volume) flow rate of the cooled cooling medium ("cold air component"). Generally, opening the valve reduces both the flow rate and the temperature of the cooled air exiting the vortex tube 57. The cooled cooling medium exits the vortex tube 57 at a cold air outlet in the direction SKM. A "hot air component" from the vortex tube is discharged away from the vortex tube 57 or the metering system 1 via 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 installed upstream of the vortex tube 57, which can be controlled by means of the control unit 90.

[0125] In the embodiment of the cooling device 2 shown here, the cooling medium is introduced into the housing 11 of the metering system 1 by means of a cooling medium supply line 84, which is coupled on one side to the vortex tube 57 and on the other side to a feed device 21, in order to cool a number of sub-areas of the piezo actuator and the movement mechanism together ("combined cooling"). A controllable pressure reducer 59 is provided between the vortex tube 57 and the feed device 21.

[0126] The described actuators – the controllable compression refrigeration unit 55, the proportional valve 56, the pressure reducer 59, and the controllable regulating valve 94 – can be used individually or in combination. The illustrated arrangement of the basic cooling circuit thus represents a near-maximum configuration for describing the function of the individual components.

[0127] If the cooling device 2 comprises two separate cooling circuits, unlike the one shown here, a first vortex tube 57 can be provided for the required cooling of the piezo actuator and a second vortex tube 57 for the required cooling of the movement mechanism.

[0128] The cooling medium is guided through the housing 11 by means of the cooling device 2 in such a way that a number of sub-areas of the piezo actuator and the movement mechanism are directly cooled. Subsequently, the cooling medium, which may have heated up as a result of heat dissipation from the piezo actuator or movement mechanism, is removed from the housing 11 by means of at least one discharge device 22 or a cooling medium drain 85, or is directed away from the actuator unit 10 in the area of ​​a hot air outlet HAD. A further pressure reducer 59 is arranged in the area of ​​the hot air outlet HAD.

[0129] The pressure reducers 59 are shown here as optional components of the cooling unit 2. The proportional valve 56 is already designed to adjust, e.g., reduce, the pressure in the cooling medium supply line 84 or in the cooling circuit by controlling the flow rate through the vortex tube 57. Furthermore, the flow of cooling medium through the vortex tube 57 and its division into a hot air section and a cold air section also result in a pressure reduction.

[0130] The housing 11 includes a heating cartridge 51, which can be controlled by the control unit 90 such that at least a portion 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 to detect the temperature of at least a portion of the piezo actuator or the movement mechanism. The corresponding data are supplied to the control unit 90 as state parameters of the dosing system.

[0131] Depending on these and other state parameters, the control unit 90 can calculate and / or implement temperature management of the dosing system to achieve the highest possible constant dosing precision. For this purpose, the control unit 90 can send corresponding control signals to the individual components of the cooling unit 2, namely the chiller 55, the proportional valve 56, the vortex tube 57 or the control valve 94, the pressure reducers 59, the heating cartridge 51, and possibly other components.

[0132] Finally, it should be noted once again that the dosing systems described in detail above are merely exemplary embodiments which can be modified in various ways by those skilled in the art without departing from the scope of the invention. For example, a single refrigeration unit can be coupled with a plurality of vortex tubes. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the relevant features may be present multiple times. Reference symbol list

[0133] 1 Dosing system 2 Cooling unit 10 Actuator unit 11 Actuator unit housing 12 Actuator chamber 13 Action chamber 14 Movement mechanism 15 Opening 16 Lever 17 Lever contact surface 18 Lever bearing 19 Actuator spring 20 Push piece 21 Feeding device / Actuator chamber 22 Discharge device / Action chamber 23 Fixing screw 24 Feeding device / Action chamber 25 Discharge device / Actuator chamber 26 Inlet channel 27 Outlet channel 28 Pump 29 Pump control connection 30 Fluidic unit 31 Plunger 32 Plunger tip 33 Plunger head 34 Plunger contact surface 35 Plunger spring 36 Plunger seal 37 Plunger 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 unit Fluidic unit 49 Heating connection cable 50 Slot / Housing 51 Heating cartridge Actuator unit 52 Temperature sensor Housing 53 Hall sensor 54 O-ring 55 Refrigeration unit 56 Proportional valve;Throttle valve 57 Vortex tube 59 Pressure reducer 60 Piezo actuator 61 Contact pin 62 Piezo actuator housing; Actuator housing 63 Base (actuator housing) 64 Cover (actuator housing) 65 Glass feedthrough 66 Piezo actuator control connections 67 Piezo stack 70 Outer electrode 73 Inactive area 74 Sheath (actuator housing) 75 Filling medium 76 Expansion area 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 housing 83 Indentation of actuator housing 84 Cooling medium supply line 85 Cooling medium discharge 86 Temperature sensor connection cable 87 Strain gauge 88, 88' Opening 90 Control unit 91 Control unit connection cable 92 Heating cartridge connection cable 94 Control valve Vortex tube HAD Hot air outlet Dosing system HAW Hot air outlet Vortex tube K Tilting axis KMZ Cooling medium supply R Discharge direction SKM Flow direction of cooling medium;

Claims

1. 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) comprising 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) being configured for direct cooling by means of the precooled cooling medium 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), characterized in that the cooling device (2) for cooling the cooling medium comprises at least one cold generating device (55, 57), wherein the cold generating device (55) is designed to cool the cooling medium to a predeterminable temperature.

2. The dosing system according to claim 1, wherein the piezo actuator (60) comprises an actuator housing (62) in which piezo elements (67) are encapsulated.

3. The dosing system according to any one of claims 1 or 2, wherein the cooling device (2) is configured to control and / or to regulate the cooling of at least one subregion of the piezo actuator (60) and / or at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60) 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 (60) and / or a temperature in at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60).

5. The dosing system 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) which is configured to cool 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) in a controlled and / or regulated manner as a function of at least one state parameter, particularly according to claim 3 or 4, characterized in that the at least one state parameter is a length of at least one subregion of the piezo actuator (60) and / or a distance between the discharge element (31) and the nozzle (40) of the dosing system (1) and / or a dosing amount.

6. The dosing system according to any one of the preceding claims 3 to 5, wherein the dosing system (1) comprises a temperature sensor (52, 78) and / or a strain sensor (87) and / or a movement sensor (53) for determining the state parameter.

7. The dosing system according to any one of the preceding claims, wherein the cooling device (2) is configured to control and / or regulate the cooling of at least one subregion of the piezo actuator (60) separately, particularly separately from the control and / or regulation of the cooling of at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60).

8. The dosing system according to any one of the preceding claims, wherein the precooled cooling medium is configured to cool at least one subregion of the piezo actuator (60) and / or at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60) to a target temperature.

9. The dosing system according to any one of the preceding claims, wherein the cold generating device (55, 57) comprises a vortex tube (57) and wherein the vortex tube (57) preferably comprises an adjustable valve (94) for regulating the temperature of the cooling medium.

10. The dosing system according to any one of the preceding claims, wherein at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60) comprises a heating device (51) for heating at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60).

11. The dosing system according to claim 10, wherein the heating device (51) is configured to keep at least one of the following state parameters constant in cooperation with the cooling device (2) of the dosing system (1): - a temperature in at least one subregion of the piezo actuator (60) and / or in at least one subregion of the movement mechanism (14) coupled to the piezo actuator (60) - a length of at least one subregion of the piezo actuator (60) - a distance between the discharge element (31) and the nozzle (40) - a dosing amount of the dosing material.

12. A method for operating a dosing system (1) according to any one of the preceeding claims for the dosing of dosing material, the dosing system (1) comprising 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), a housing (11) of the dosing system (1) being fed a precooled cooling medium by means of a supply device (21, 24, 26) of the cooling device (2), and 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) being cooled directly by the cooling device (2) by means of the precooled cooling medium.

13. A method for manufacturing a dosing system (1) for the dosing of dosing material having an actuator unit (10) having a piezo actuator (60), the dosing system (1) being equipped with a cooling device (2), the cooling device (2) being equipped with a supply device (21, 24, 26) for feeding a precooled cooling medium into a housing (11) of the dosing system (1), and the dosing system (1), particularly the cooling device (2), being configured so that 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) is cooled directly by means of the precooled cooling medium, characterized in that the cooling device (2) for cooling the cooling medium comprises at least one cold generating device (55, 57), wherein the cold generating device (55) is designed to cool the cooling medium to a predeterminable temperature.