Eccentric screw microdosing device and method for controlling an eccentric screw microdosing device

Description

[0001] The invention relates to an eccentric screw microdosing device according to the preamble of patent claim 1 and a method for controlling a microdosing process according to patent claim 7.

[0002] As is well known, industrial production is only possible through reproducibility and process control across all production phases, because process improvement accompanying production enables ongoing optimization, which maintains long-term competitiveness.

[0003] Knowledge and monitoring of all states of dosing devices in a production plant that determine the production process are therefore critical.

[0004] With the advent of increasingly high-performance liquid and pasty functional materials and the advent of miniaturization, there has been a growing need to dispense liquids and pastes more and more quickly and precisely in industrial manufacturing processes. The dispensed material can then perform functions such as pre-fixing and bonding, electrical and thermal contacting, shielding, hermetically sealing, and more. Even the actual functional components are now being manufactured using dispensing processes, such as optical lenses, conductors, or diffusers, using 3D printing. However, the innovative differentiation of increasingly high-performance, application-specific media is leading to extreme dispensing characteristics: high and / or abrasive solid loading in the dispensed material (e.g., thermal pastes or LED phosphors), narrow process windows for temperature, pressure, agitation, etc.Kinetic energy input or pot life require ever more precise adjustment of the dosing device to the currently effective "system situation" of dosing material, dosing device and process requirements.

[0005] Along with miniaturization and increased productivity, the requirement to dose ever smaller quantities with high precision and repeatability is growing, with process reliability and system availability being essential criteria for the selection of the dosing method.

[0006] Dosing devices with eccentric screw pumps with their self-sealing rotor-stator fits are very versatile due to their precise volumetric operation. As long as they operate within the normal operating range, they convey the dosing material - including any fillers - exactly proportional to the angle of rotation, albeit with defined, easily averaged flow drops due to the opening and closing phases of the screw chambers. The control of the drive motor of the eccentric screw pump therefore uses the speed and angle of rotation as target variables for volumetric dosing. The positioning movement-synchronous control of the speed then enables a locally constant dosing quantity, for example, a uniform dosing material application at the target. Typical tribological factors include:Interacting interface properties between the eccentric screw pump and the dosing material as well as the viscosity behavior of the dosing material determine performance, service life and reliability - and are highly dependent on wear.

[0007] According to the state of the art, the individual dispensing process is roughly preset based on general empirical values ​​of the available parameters and then fine-tuned through series of tests until the desired result is consistently achieved. This process must then be quickly and appropriately adjusted in the event of deviations. To date, this requires quality assurance or the process manager to conduct regular spot checks based on the dispensing results (usually on stored dispenses or, for example, on the finished intermediate product). In some cases, this is already being accomplished using automated processes, e.g., through image processing evaluation of the placed dispensed material.

[0008] If quality problems or even dispensing interruptions occur during high-production series production, questionable batches must be traced back to the first sample violation, the production process must be stopped, and the dispensing process must be improved before series production can resume. The damage and expense can be considerable, and the predictable system availability suffers, and reliability is called into question.

[0009] The present invention is particularly explosive due to the market's innovative drive towards minimum quantity dosing with ever more extreme differentiation of dosing material properties for the production of high-value target products: the amount of dosing material used and the target product yield are economically highly relevant factors and therefore in the focus of the market, while the expenditure on production resources hardly counts towards the unit costs in view of the high productivity of modern production plants and thus more than justifies the investment in innovative plant technology.

[0010] According to the state of the art, dosing devices with eccentric screw pumps (and also with eccentric screw, endless piston, Monho / Moineau or peristaltic pumps) typically control with the speed and angle of rotation of the drive motor as the target variable, because these correspond to a clearly calculable dosing flow or dosing volume from the rotor-stator assembly in the trouble-free and unworn regular operating range.

[0011] The fact that the rotor-stator fit properties are extremely relevant for the dispensing process, as shown by the phenomena of practical use, remains unconsidered and must be taken into account through preventive usage restrictions and process risks.

[0012] Well-known such phenomena are, for example, High breakaway forces of the fit during start-up (slip, sticking and vibration tendency) Insufficient chamber filling Temperature-dependent fit properties Media-dependent fit properties Media-dependent torque Media-dependent wear Wear-related dosing process changes (fit changes) "Sudden", unforeseen (rotor strand) breakage or blockage or total failure, among other things Kinetic-related media changes (process parameter-dependent) Changes in and repercussions from the downstream dosing strand (e.g. clogging of the dosing needle)

[0013] The criteria for maintenance requirements and wear status are based on empirical values, including anticipated service life reserves, which, if possible, were obtained with similarly demanding dosing materials and process conditions. This results in growing deficiencies in three respects: the risk of sudden failure is associated with increasingly high-quality production waste. Actually comparable previous experience is rare due to the progressive, application-specific differentiation of dosing material properties toward "high-tech" properties with typically extreme and narrow process windows. In addition, production lines are becoming increasingly productive, resulting in correspondingly high production downtimes in the event of downtime or defective production.

[0014] According to the state of the art, a lack of knowledge of the current system and wear status can lead to, for example, a drift in dosing accuracy, a chipping of a clogged dosing needle or the spontaneous breakage of the drive train with correspondingly costly consequences.

[0015] In contrast, the invention is based on the object of creating a microdosing device and method for controlling a microdosing process which avoids the disadvantages described above.

[0016] This object is achieved by a microdosing device having the features of patent claim 1 and a method for controlling a microdosing process having the features of patent claim 7.

[0017] Further advantageous embodiments of the invention are described in the dependent patent claims.

[0018] According to the invention, use is made of the knowledge that a pragmatically relevant subsumption of current influences is manifested in the course of the torque on the conveyor rotor or conveyor stator and that this therefore represents the primary variable to be evaluated in the control system.

[0019] Preferably, the readjustment is carried out via the drive torque and angle of rotation, or the resulting speed of the conveyor rotor, as well as the more sluggish control variables of temperature or back pressure at the dosing material feed and eccentric screw pump. Depending on the dosing device and dosing material, other control variables are also available in the control loop, which, thanks to the inventive, sensitive condition detection, can also be used for rapid readjustment or maintenance planning before real quality defects or even a system failure occur.

[0020] The present invention makes it possible to detect impending deviations in the dosing process early and preferably automatically, analyze them with a view to potential manipulated variables, and thus enable immediate readjustment without any interruption to production or the production of rejects. The service life of the production equipment and the pot life of the dosing material can be reliably and fully utilized, thus eliminating the need for safety reserves that would otherwise be lost.

[0021] Furthermore, the invention opens up entirely new application strategies by always providing complete control over the dosing process, based on the current functional state. Thus, for example, even "poor" fits between the conveyor rotor and conveyor stator can still be utilized right up to the edge of the process window: Fits that were previously discarded as a precaution due to doubtful service life expectations can now be safely driven to the wear limit using the inventive approach. The torque measurement according to the invention also enables, for example, the tracking of a fit-relevant contact force, as well as many other methods for adjusting the functionally relevant fit lines of the eccentric screw pump in order to adapt the dosing characteristics or improve the service life.

[0022] Wear of the rotor-stator fit reduces the torque required per angle of rotation under unchanged media conditions, while the rising edges may become flatter and their phase position may shift compared to the new condition. The attack and overshoot behavior changes significantly. The observed phenomena can be further clarified by special control cycles.

[0023] With appropriately sensitive measurement, the torque to be overcome by the conveyor rotor drive, correlated with a known standard condition and, if applicable, the individual's history, adequately reflects all of the currently relevant properties of the functional progressing cavity pump, allowing for the highest-precision reliability in the dosing process, suitable for series production. Process fluctuations can be corrected accordingly, maintenance requirements anticipated, and unforeseen production interruptions avoided.

[0024] Both the steady-state torque and, for example, start-up ramps with their slope, phase position, and overshoot behavior provide clear indications of the wear status of the eccentric screw pump. Specially defined drive cycles can facilitate the condition analysis of the eccentric screw pump (and the metered material).

[0025] The inclusion of additional production process information perfects the performance, availability, and reliability of the dosing device, resulting in increased productivity, cost efficiency, and quality of results. This opens up new application possibilities, for example, in precise microdosing.

[0026] According to the invention, changes in dosing accuracy can be detected and corrected through sensitive torque monitoring, and the approach to a dosing process limit can be predictably counteracted through a needs-based maintenance plan. This also enables the safe exploitation of the maximum possible service life of the high-quality dosing components.

[0027] Furthermore, the fine controllability according to the invention also enables smaller dosages to be reliably made with the required accuracy.

[0028] The present invention closes a gap in monitoring and process control, thus eliminating high risks to quality and plant availability. It creates the prerequisites for Industry 4.0 and self-learning (AI) applications.

[0029] The specifically claimed microdosing device comprises an eccentric screw pump having a conveyor stator and a conveyor rotor, wherein the conveyor rotor is rotatable relative to the conveyor stator by means of a drive. According to the invention, a torque sensor is provided for detecting the torque effectively applied to the conveyor rotor or the conveyor stator.

[0030] The microdosing device or the microdosing process can be characterized by at least one of the following features: The volume of each dispense is in the microliter range (ul) (equivalent to the milligram range) or less, i.e. the volume of each dispense is less than 1 milliliter (ml). Low flow rates, i.e. less than 2 milliliters per second (ml / s), in particular less than 1 milliliter per second (ml / s). Small dead space losses (i.e. low consumption of dispensed material up to the first dispense). High accuracy requirements, including repeatability. Preservation of the often highly sensitive properties of the dispensed material (viscosity, pot life, etc.). The functionality of the dispensed material depends on the precision of the application, not just on the volume. The eccentric pump and the dispensed material must therefore be controlled together because of the strong mutual influence. The ratio of the contacting surfaces of the eccentric pump to the dispensed material volume is high.

[0031] In a first basic principle of the invention, the torque sensor is frictionally integrated into a rotor train between the drive and the eccentric screw pump. This means that at least essential parts of the torque sensor rotate.

[0032] In a second basic principle of the invention, the torque sensor is integrated into a stator strand between the housing or the stator coupling housing and the eccentric screw pump. This makes the torque sensor fixed to the housing.

[0033] In the first basic principle, the torque sensor is installed serially between the drive and the eccentric screw pump, e.g. in the rotor train - preferably via adapting couplings.

[0034] In the second basic principle, the torque sensor is arranged between the stator coupling housing and the conveyor stator.

[0035] The torque sensor can preferably be retrofitted by the user in a modular manner between the drive and the progressing cavity pump, or between the stator coupling housing and the conveyor stator. For example, the torque sensor can be retrofitted by the user in a modular manner into the rotor train or stator train. The torque sensor is connected via an adaptable coupling to the drive on the one hand and the conveyor rotor on the other, or to the stator coupling housing on the one hand and the conveyor stator on the other.

[0036] The term "rotor train" refers to rotating components, in particular a drive rotor and the conveyor rotor. The term "stator train" refers to components fixed to the housing, in particular the stator coupling housing, the conveyor stator, and the stator mount.

[0037] The drive is primarily an electric motor.

[0038] The microdosing device according to the invention preferably also has a rotation angle sensor for the conveyor rotor. This can also be developed as a speed sensor. This further facilitates the early and preferably automatic detection of impending deviations in the dosing process.

[0039] The microdosing device according to the invention preferably has at least one additional sensor for a dosing material. The additional sensor can be a dynamic pressure sensor, a temperature sensor, or a volumetric flow sensor. This further facilitates the early and preferably automatic detection of impending deviations in the dosing process according to the invention.

[0040] The specifically claimed sensor method serves to optimize a microdosing process. According to the invention, the temporal progression of a torque effectively applied to a conveyor rotor or conveyor stator of an eccentric screw pump of a microdosing device is continuously or periodically recorded, logged, and output. This serves to monitor and / or control and / or parameterize and / or maintain the microdosing device. The microdosing device is preferably a previously described microdosing device.

[0041] A particularly preferred development of the method according to the invention serves to further optimize the microdosing process. The temporal progression of a rotation angle or speed of the conveyor rotor is recorded, logged, and / or output. This serves for monitoring and / or controlling and / or parameterizing and / or maintaining the microdosing device.

[0042] An impulse response analysis can also be carried out after active excitation to determine the condition of the microdosing device, in particular the eccentric screw pump, in particular a rotor-stator assembly.

[0043] The evaluation of the torque curve and, if applicable, the angle of rotation or the speed is preferably carried out within the framework of a self-learning control process of the microdosing.

[0044] In a preferred refinement of the method, a service and maintenance plan is created using the torque curve recorded according to the invention, and if applicable, also the angle of rotation or speed. This serves to maximize service life, system availability, reliability, and prevent unexpected total failures.

[0045] Based on the knowledge gained and the possibilities for the microdosing process, the above-mentioned service and maintenance plan will be modified or a separate service and maintenance plan will be created if the process is further developed. This also serves to maximize uptime, system availability, reliability, and prevent unexpected total failures.

[0046] With the aid of the torque detected according to the invention or its course, a condition of a dosing material can also be monitored, wherein the condition is preferably a viscosity.

[0047] With at least one additional sensor, a back pressure and / or a temperature and / or a delivery volume of the dosing material can also be monitored.

[0048] Using the insights gained and the possibilities regarding the dosing material, the above-mentioned service and maintenance plan can be modified or a separate service and maintenance plan can be created. This also serves to maximize pot life, dosing material consumption, system availability, reliability, and avoid unexpected total failures.

[0049] In a preferred refinement of the method, a total failure is signaled – preferably immediately. This can be a break in the drive train, which is detected by an extremely high torque or an extremely low torque. In a refinement of the method with angle or speed monitoring, the break in the drive train can also be detected by an extremely high or extremely low speed.

[0050] A preferred application of this method is to compensate for design-related dosing quantity fluctuations in eccentric screw pumps used in microdosing. This increases dosing accuracy and thus improves process precision.

[0051] Three embodiments of the microdosing device according to the invention and one embodiment of the method according to the invention are shown in the figures.

[0052] It shows Figure 1 an eccentric screw pump and a drive of the microdosing device according to the invention according to a first embodiment of a first basic principle of the invention in a sectional view, Figure 2 the microdosing device according to the invention according to a second embodiment of the first basic principle of the invention in a schematic representation, Figure 3 an embodiment of the method according to the invention for controlling a microdosing process, and Figure 4 the microdosing device according to the invention according to a second basic principle of the invention in a sectional view.

[0053] According to the first embodiment of Figure 1 According to the invention, the microdosing device has a torque sensor 110, which is non-positively connected, on the one hand, to the electric motor drive 10 and, on the other hand, to an eccentric screw conveyor rotor 50 of an eccentric screw pump 1. The connection between the drive 10 and the conveyor rotor 50 is formed by a rotor train into which the torque sensor 110 is non-positively integrated.

[0054] The eccentric screw pump 1 has a conveying stator 60, which is fixedly mounted in a stator receptacle 70. The stator receptacle 70 is fixedly connected to a housing of the electric motor drive 10 via a stator coupling housing 20. InThe rotor strand with the torque sensor 110 is accommodated in the stator coupling housing 20.

[0055] The conveyor stator 60 surrounds the conveyor rotor 50, forming sealed screw chambers which, when the conveyor rotor 50 rotates, are fed by a metered material inlet 100 (in Figure 1 downwards) in the direction of a dispensing needle holder 80.

[0056] Signals from the torque sensor 110 are available to a (in Figure 1 The metering control (not shown) is continuously available. The metering control thus has information at all times about the torque being fed from the drive 10 into the conveyor rotor 50 of the eccentric screw pump 1.

[0057] Additional sensors 90 can provide helpful additional information regarding the dosing material (such as its back pressure, temperature or flow rate) from the dosing outlet of the dosing needle holder 80 to the electronic dosing control.

[0058] Figure 2 shows the metering device according to the invention according to a second embodiment, with which both basic principles of the invention can be implemented. Dosage material is conveyed from a container 140 to the metered material inlet 100 of the eccentric screw pump 1. Its (in Figure 2 The conveyor rotor (not shown) is driven by the electric motor drive 10 via the rotor train, wherein in or on the rotor train, in addition to the torque sensor 110, a speed sensor 120 is also arranged.

[0059] Signals from the torque sensor 110 are continuously available to the electronic dosing control µC. In combination with the angle information from the speed sensor 120, the dosing control µC therefore has at its disposal the information at any time regarding the forces, power, and energy being fed from the drive 10 into the conveyor rotor 50 of the eccentric screw pump 1. A volumetric flow sensor 90 provides helpful additional information regarding the dosing material from the dosing outlet of the (in Figure 2 not shown) dispensing needle holder to the dispensing control µC.

[0060] Respective couplings 30 are arranged in the rotor train on both sides of the torque sensor 110, i.e., on the drive 10 side and on the eccentric screw pump 1 side. These couplings enable the subsequent modular insertion of the torque sensor 110 according to the invention into the rotor train. This allows an existing dosing device, in particular the micro-dosing device shown, to be retrofitted with the sensor technology according to the invention.

[0061] In both embodiments according to the Figures 1 and 2 The dosing control µC continuously controls the conveyance of the dosing material via the drive 10 by specifying the angle of rotation per unit of time that corresponds to the desired flow rate. At the same time, the dosing control µC continuously records the measurement signals from the torque sensor 110 and, optionally, the speed sensor 120 and / or at least one additional sensor 90.

[0062] According to Figure 3The electronic dosing control µC performs measurement, logging, testing, and reporting cycles either simultaneously or during production interruptions and / or in combination with specially defined microdosing test sequences. To do this, the dosing control µC records the torque in particular during the time cycle, saves it as an additional log file, and compares it with existing cycle logs, the commissioning status of the microdosing device or its eccentric screw pump 1, and any stored limit pattern profiles in terms of amplitude, edge steepness, onset and overshoot characteristics, and phase position.

[0063] The highest priority is given to the particularly simple detection of rotor breakage or blockage, which is immediately signaled to the higher-level QM process control computer with the highest priority so that it can immediately stop the production process to avoid rejects.

[0064] Without such an alarm finding, the remaining target or "n / n+1" measurement deviations are converted into a status (diagnosis) protocol based on existing algorithmic empirical values ​​to estimate the remaining service life, the next maintenance interval and a degree of confidence (e.g., probability of failure in the current maintenance interval).

[0065] These status indicators can be used advantageously by the QM process control computer to maximize the availability, yield, productivity and cost efficiency of the manufacturing processes.

[0066] Figure 4 shows a third embodiment of the microdosing device according to the invention in a sectional view. The electric motor 10 serving as the drive, the eccentric screw pump 1 and the dosing needle holder 80 with the additional sensor 90, which can be a flow rate sensor, correspond to those of the first embodiment of Figure 1 .

[0067] In contrast to the first exemplary embodiment, the torque sensor 110 according to the invention is arranged between the stator coupling housing 20 and the stator receptacle 70 according to a second basic principle of the invention. Thus, the torque sensor 110 is fixed to the housing without rotating functional parts.

[0068] Disclosed are a microdosing device and a method for controlling a microdosing process using a microdosing device. The microdosing device has an eccentric screw pump driven by, for example, an electric motor drive via a torque sensor. The torque is measured continuously or periodically. This allows conclusions to be drawn about the condition and / or changes, such as wear, of the eccentric screw pump. List of reference symbols

[0069] 1 Eccentric screw pump 10 Drive / electric motor 20 Stator coupling housing 30 Coupling 40 Connecting flange 50 Conveyor rotor 60 Conveyor stator 70 Stator mount 80 Dosing needle mount 90 Additional sensor, flow rate sensor 100 Dosing material inlet 110 Torque sensor QM process control computer µC electronic dosing control

Claims

1. A micro-dosing device with an eccentric screw (1), comprising a feed stator (60) and a feed rotor (50), wherein the feed rotor (50) is rotatable relative to the feed stator (60) via a drive (10), characterized by a torque sensor (110) for detecting the torque effectively applied to the feed rotor (50) or to the feed stator (60).

2. The micro-dosing device according to claim 1, characterized in that the torque sensor (110) is integrated in a rotor strand between the drive (10) and the eccentric screw (1) or in a stator strand between a stator coupling housing (20) and the eccentric screw (1) in a force-fit manner.

3. The micro-dosing device according to claim 2, characterized in that the torque sensor (110) is preferably introduced serially between the drive (10) and the eccentric screw (1) via adapting couplings (30), or in that the torque sensor (110) is preferably arranged serially between the stator coupling housing (20) and the feed stator (60).

4. The micro-dosing device according to claim 2 or 3, characterized in that the torque sensor (110) can be inserted subsequently.

5. The micro-dosing device according to one or more of the preceding claims, characterized by an angle of rotation sensor (120) for the feed rotor (50).

6. The micro-dosing device according to one or more of the preceding claims, characterized by at least one further sensor (90) for a dosing material, which is a dynamic pressure sensor or a temperature sensor or a delivery volume flow sensor.

7. A sensor method for optimizing a micro-dosing process characterized by a continuous or periodic detection and logging of the time course of a torque effectively applied to a feed rotor (50) or to a feed stator (60) of an eccentric screw (1) of a micro-dosing device - in particular according to one of the preceding claims.

8. The method according to claim 7, characterized by a detection and logging of the course over time of a rotation angle or of a rotational speed of the feed rotor (50).

9. The method according to claim 7 or 8, characterized in that, after active excitation, an impulse response analysis is carried out to determine the state of the micro-dosing device, in particular of the eccentric screw (1).

10. The method according to one of claims 7 to 9, characterized in that the utilization of the torque curve takes place as part of a self-learning control process of the dosing.

11. The method according to one of claims 7 to 10, characterized in that a service and maintenance plan is created with the aid of the torque curve.

12. The method according to one of claims 7 to 11, characterized in that a state of a dosing material is monitored with the aid of the torque or of the torque curve, wherein the state is preferably a viscosity.

13. The method according to one of claims 7 to 12, characterized in that at least one state of a dosing material is monitored, wherein the state is a stagnation pressure, or a temperature, or a delivery volume.

14. The method according to claim 12 or 13, characterized in that a service and maintenance plan is created and / or adapted with the aid of the state of the dosing material.