DE102021103615A1 - Eccentric screw metering device and method for controlling an eccentric screw metering device - Google Patents

Abstract

A dosing device and a method for controlling a dosing process with a dosing device are disclosed. The dosing device has an eccentric screw pump which is driven, for example, by an electric motor via a torque sensor. The torque is recorded continuously or periodically. From this, conclusions are drawn about the condition and/or changes, such as wear and tear of the progressing cavity pump.

Description

The invention relates to an eccentric screw dosing device according to the preamble of patent claim 1 and a method for controlling a dosing process with such an eccentric screw dosing device.

As is well known, industrial production is only possible through reproducibility and process control over all production phases, because process improvement accompanying production enables ongoing optimization that permanently maintains competitiveness.

Knowledge and monitoring of all the states of dosing devices in a production plant that determine the production process are correspondingly explosive.

With more and more efficient liquid and pasty functional materials and miniaturization, the need also developed to dose liquids and pastes in the industrial manufacturing process more and more precisely and quickly, with the dosing material being e.g functionalities takes over. In the meantime, even the actual, functional components are manufactured using dosing processes, such as optical lenses, conductors or diffusers, etc. in 3D printing. However, the innovative differentiation of the ever more powerful, application-specific media leads to extreme dosing properties: high and/or abrasive solids loading in the medium (e.g. with thermally conductive pastes or LED phosphors), narrow process windows for temperature, pressure, agitation or kinetic energy input or pot life ever more precise adjustment of the dosing device to the currently effective "system situation" of medium, dosing device and process requirements.

Along with miniaturization and increased productivity, there is a growing need to dose smaller and smaller quantities with high precision and repeat accuracy, with process reliability and system availability being key criteria when choosing the dosing method.

Dosing devices with progressing cavity pumps with their self-sealing rotor-stator fits are very versatile due to their precise volumetric functionality. As long as these work in the regular operating range, they convey the dosing material - including any fillers - exactly in proportion to the angle of rotation, albeit with defined, easily averaged conveying drops due to the opening and closing phases of the screw chambers. A regulation of the drive motor of the progressing cavity pump therefore uses speed and angle of rotation as target values of the volumetric dosing operation. The positioning movement-synchronous control of the speed then enables a locally constant dosing quantity, e.g. an even dosing application on the target. Typical tribological, inter alia, interacting interface properties between the progressing cavity pump and the dosing material as well as the viscosity behavior of the dosing material are decisive for performance, service life and reliability - and are heavily dependent on wear.

According to the state of the art, the individual dosing process is roughly preset on the basis of general experience using the available parameters and then fine-tuned through a series of tests until the desired result is achieved in a stable manner. This state must then be readjusted quickly and appropriately in the event of deviations, for which up to now quality assurance or the person responsible for the process has been required to carry out regular spot checks based on the dosing result (usually on stored doses or e.g. on the finished intermediate product). In some cases, this is already done via automatic processes, e.g. via the image processing evaluation of the placed dosing material.

If quality problems or even dosing interruptions then occur in highly productive series use, questionable batches must be traced back to the first limit sample infringement, the manufacturing process must be stopped and the dosing process must be improved before series production can start again. Damage and expense can be significant and the calculable system availability suffers, reliability is in question.

The present invention gains particular explosiveness through the innovative striving of the market in the direction of minimum quantity dosing with ever more extreme differentiation of dosing material properties for the production of high-value target products: expended dosing material quantity and target product yield are economically highly relevant factors and therefore in the focus of the market, while the cost of production means is considered the high productivity of modern production plants is hardly relevant to the unit costs and thus more than justifies the investments in innovative plant technology.

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

The fact that the rotor-stator fitting properties are extremely relevant to the dosing process, as shown in the phenomena of practical use, is not taken into account and must be taken into account through preventive usage restrictions and process risks.

• • hohe Losbrechkräfte der Passung beim Anfahren (Slip-, Stick- und Schwingungstendenz)
• • mangelnde Kammerfüllung
• • temperaturabhängige Passungseigenschaften
• • medienabhängige Passungseigenschaften
• • medienabhängiges Drehmoment
• • medienabhängiger Verschleiß
• • verschleißbedingte Dosierprozessveränderung (Passungsänderung)
• • „plötzlicher“, unvorhergesehener (Rotorstrang-) Bruch oder Blockade bzw. Totalausfall
• • u.a. kinetisch bedingte Medienveränderung (prozessparameterabhängig)
• • Veränderungen im, und Rückwirkungen aus dem nachgeschalteten Dosierstrang (z.B. Verstopfen der Dosiernadel)

Well-known phenomena of this type are, for example

• • High breakaway forces of the fit when starting (tendency to slip, stick and vibrate)
• • insufficient filling of the chamber
• • temperature-dependent fit properties
• • media-dependent fit properties
• • Medium-dependent torque
• • media-dependent wear
• • Dosing process change due to wear (change of fit)
• • "Sudden", unforeseen (rotor strand) breakage or blockage or total failure
• • Among other things, kinetically caused media change (depending on the process parameters)
• • Changes in and repercussions from the downstream dosing line (e.g. clogging of the dosing needle)

As criteria for the need for maintenance and the state of wear, empirical values including the service life reserves to be provided are used, which were obtained as far as possible with similarly demanding dosing material and process conditions. This results in increasing inadequacies in three respects: the risk of sudden failure is associated with increasingly high-quality production rejects. Previous experiences that are actually comparable are rare because of the progressive, application-specific differentiation of dosing material properties towards "high-tech" properties with typically extreme and narrow process windows. In addition, there is a higher productivity of the production lines with a correspondingly high production loss in the event of standstill or faulty production.

According to the state of the art, a lack of knowledge of the current system and state of wear can result, for example, in the dosing accuracy drifting off, a clogged dosing needle flaking off or the drive train spontaneously breaking, with correspondingly costly consequences.

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

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

Further advantageous refinements of the invention are described in the dependent patent claims.

According to the invention, use is made of the finding that a pragmatically relevant subsummation of current influences manifests itself in the course of the torque on the conveyor rotor or conveyor stator, and this therefore represents the control variable to be primarily evaluated.

The readjustment is preferably carried out via the drive torque and angle of rotation or the rotational speed of the conveying rotor derived from this, as well as the rather sluggish manipulated variables of temperature or dynamic pressure at the dosing material feed and eccentric screw pump. Depending on the dosing device and dosing material, other manipulated variables are also available in the control loop, which can also be used by the sensitive status detection according to the invention for quick readjustment or maintenance planning even before real quality defects or even a system failure occur.

The present invention makes it possible to recognize impending deviations in the dosing process early and preferably automatically, to analyze them with a view to possible manipulated variables and thus to enable the immediate readjustment process without production being interrupted or rejects being produced at all. The service life of the means of production and the pot life of the dosing material become reliable and fully exploitable, i.e. without the need for safety reserves to be provided and in any case lost.

Furthermore, the invention opens up completely new application strategies by always creating complete control over the dosing process based on the current functional status and thus, for example, "poor" fits between the conveyor rotor and conveyor stator can still be used right up to the edge of the process window: fits that were previously dubious expectation of service life were discarded as a precaution, can be driven risk-free up to the wear limit by proceeding according to the invention. Also, for example, the tracking of a fit-relevant Contact force can be used through the torque detection according to the invention, as well as many other methods of readjusting the functionally relevant fit lines of the eccentric screw pump in order to adapt the metering properties or to improve the service life.

Due to wear of the rotor-stator fit, the torque to be applied per angle of rotation with unchanged media conditions decreases, while the rising flanks can become flatter and their phase position shifts compared to the new condition. The transient and overshoot behavior changes significantly. The observed phenomena can be further clarified by special control cycles.

The torque to be overcome by the drive of the conveying rotor forms, with correspondingly sensitive recording, with correlation to a known standard state and, if necessary, the individual history, sufficiently from the entirety of the currently relevant properties of the functional progressing cavity pump, so that a series production-oriented reliability in the dosing process of the highest precision can be derived from this is. Process fluctuations can be corrected based on this, maintenance requirements can be foreseen and unforeseen production interruptions can be avoided.

Both the steady torque and, for example, start-up ramps with their edge steepness, phasing and overshoot behavior provide clear indications of the state of wear of the progressing cavity pump. Specially defined drive cycles can facilitate the status analysis of the progressing cavity pump (and the dosing material).

The inclusion of further production process information perfects the performance, availability and reliability of the dosing device in terms of productivity, cost efficiency and quality of results. There are new possible uses, for example in precise microdosing.

According to the invention, changes in the dosing accuracy can be recognized and corrected by sensitive monitoring of the torque, and the approach to a dosing process limit can be intercepted in a calculable manner by means of a needs-based maintenance plan. This also enables the maximum possible service life of the high-quality dosing components to be safely exploited.

Furthermore, the ability to be finely adjusted according to the invention also enables smaller and smaller dosages to be dosed reliably with the required accuracy.

The present invention closes a gap in monitoring and process control and thus eliminates high risks for quality and plant availability. It creates the conditions for Industry 4.0 and self-learning (AI) applications.

The specifically claimed metering device has an eccentric screw pump which has a conveyor stator and conveyor rotor, the conveyor rotor being 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.

The torque sensor is preferably integrated in a non-positive manner in a rotor train between the drive and the eccentric screw pump.

The torque sensor is preferably installed serially via adapting couplings between the drive and the eccentric worm pump, e.g. in the rotor assembly.

The torque sensor can preferably be subsequently inserted by the user in a modular manner between the drive and the eccentric screw pump. For example, the user can subsequently insert the torque sensor into the rotor train in a modular manner. The torque sensor is non-rotatably coupled to the drive on the one hand and to the conveyor rotor on the other by means of an adapting clutch.

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

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

The specifically claimed sensory method serves to optimize a dosing process. According to the invention, an ongoing or periodic cal detection and logging and output of the time profile of a torque effectively applied to a delivery rotor or to a delivery stator of an eccentric screw pump of a dosing device. This serves to monitor and/or regulate and/or parameterize and/or maintain the dosing device. The dosing device is preferably a dosing device as described above.

A particularly preferred development of the method according to the invention serves to further optimize the dosing process. In this case, the time course is recorded, logged and/or output, including a rotation angle or a speed of the conveyor rotor. This serves to monitor and/or regulate and/or parameterize and/or maintain the dosing device.

After active excitation, an impulse response analysis can also be carried out to determine the state of the dosing device, in particular the eccentric screw pump, in particular a rotor-stator assembly.

The evaluation of the course of the torque and possibly the angle of rotation or the speed is preferably carried out within the framework of a self-learning control process of the metering.

In a preferred development of the method, a service and maintenance plan is drawn up with the aid of the course of the torque recorded according to the invention and possibly also the angle of rotation or the rotational speed. This serves to maximize service life, system availability, reliability and avoid unexpected total failures.

In a preferred further development of the method, the above-mentioned service and maintenance plan is changed or an extra service and maintenance plan is created with the aid of the knowledge and possibilities gained for the dosing process. This also serves to maximize service life, system availability, reliability and avoid unexpected total failures.

With the aid of the torque detected according to the invention or its progression, a state of a dosing product can also be monitored, with the state preferably being a viscosity.

A dynamic pressure and/or a temperature and/or a delivery volume of the dosing material can also be monitored with at least one additional sensor.

With the help of the knowledge and possibilities gained regarding the dosing material, the above-mentioned service and maintenance plan can be changed or an extra 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.

In a preferred development of the method, a total failure is signaled immediately. Specifically, this can be a break in the drive train, which is detected by an extremely high torque or by an extremely low torque. In the further development of the method with the angle of rotation or speed monitoring, the break in the drive train can also be detected by an extremely high or extremely low speed.

Two exemplary embodiments of the dosing device according to the invention and an exemplary embodiment of the method according to the invention are shown in the figures.

• 1 eine Exzenterschneckenpumpe und einen Antrieb der erfindungsgemäßen Dosiervorrichtung gemäß einem ersten Ausführungsbeispiel in einer geschnittenen Darstellung,
• 2 die erfindungsgemäße Dosiervorrichtung gemäß einem zweiten Ausführungsbeispiel in einer schematischen Darstellung, und
• 3 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens zur Steuerung eines Dosierprozesses.

Show it

• 1 an eccentric screw pump and a drive of the metering device according to the invention according to a first embodiment in a sectional view,
• 2 the dosing device according to the invention according to a second embodiment in a schematic representation, and
• 3 an embodiment of the method according to the invention for controlling a dosing process.

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

The eccentric screw pump 1 has a conveyor stator 60 which is accommodated in a stator mount 70 fixed to the housing. The stator receptacle 70 is firmly connected to a housing of the electric motor drive 10 via a stator coupling housing 20 . The rotor strand with the torque sensor 110 is accommodated in the stator coupling housing 20 .

The feed stator 60 surrounds the feed rotor 50, as a result of which sealed screw chambers are formed which, when the feed rotor 50 rotates, are ejected from a dosing material inlet 100 (in 1 downward) are moved in the direction of a dosing needle seat 80 .

Torque sensor 110 signals are in a (in 1 not shown) electronic dosing control continuously available. The dosing control thus has the information at all times as to which torque is being fed from the drive 10 into the feed rotor 50 of the eccentric screw pump 1 .

Other sensors 90 can supply helpful additional information regarding the dosing material (such as its dynamic pressure, temperature or delivery volume flow) from the dosing outlet of the dosing needle holder 80 to the electronic dosing control.

2 shows the dosing device according to the invention according to a second embodiment. Metering material is conveyed from a container 140 to the metering material inlet 100 of the eccentric screw pump 1 . Their (in 2 (not shown) conveying rotor is driven by the electric motor drive 10 via the rotor train, with a speed sensor 120 also being arranged in or on the rotor train in addition to the torque sensor 110 .

Signals from the torque sensor 110 are continuously available to the electronic dosing controller μ0. In combination with the rotational angle information from the rotational speed sensor 120 , the dosing controller μC thus has the information at all times as to which forces, outputs and energies are being fed from the drive 10 into the delivery rotor 50 of the eccentric screw pump 1 . A delivery volume flow sensor 90 provides helpful additional information regarding the dosing material from the dosing outlet of the (in 2 not shown) dosing needle holder to the dosing controller µC.

In the rotor train, on both sides of the torque sensor 110, ie on the side of the drive 10 and on the side of the eccentric screw pump 1, respective clutches 30 are arranged. These allow a subsequent modular insertion of the torque sensor 110 according to the invention in the rotor train. An existing dosing device can thus be retrofitted with the sensor system according to the invention.

In both embodiments according to 1 and 2 controls the dosing control μC continuously the promotion of the dosing via the drive 10 by angle of rotation specifications per unit of time, which correspond to the desired delivery volume flow. At the same time, metering controller µC continuously records the measurement signals from torque sensor 110 and optionally from speed sensor 120 and/or the at least one additional sensor 90.

According to 3 the electronic dosing control µC carries out measuring, logging, testing and reporting cycles either simultaneously or during production interruptions and/or in combination with specially defined dosing test processes. For this purpose, the dosing control µC records in particular the torque in the cycle over time, saves this as an additional log file and compares it in terms of amplitude, edge steepness, transient and overshoot character and phase position with existing cycle logs, that of the commissioning status of the dosing device or its eccentric screw pump 1 and any stored ones border pattern gradients.

The highest priority is 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 stop the production process immediately to avoid rejects.

Without such an alarm finding, the remaining target or "n/n+1" measurement deviations are converted into a status (diagnosis) log for estimating the remaining service life, the next maintenance interval and a degree of confidence (e.g. probability of failure in the current maintenance interval) using existing algorithmic empirical values ).

The QM process control computer can use these status indicators to maximize availability, yield, productivity and cost efficiency of the manufacturing processes.

A dosing device and a method for controlling a dosing process with a dosing device are disclosed. The dosing device has an eccentric worm pump which is driven, for example, by an electric motor via a torque sensor. The torque is recorded continuously or periodically. From this, conclusions are drawn about the condition and/or changes, such as wear and tear of the progressing cavity pump.

Reference List

1

progressing cavity pump

10

drive

20

stator coupling housing

30

coupling

40

connecting flange

50

conveyor rotor

60

conveyor stator

70

stator mount

80

dosing needle holder

90

further sensor, delivery volume flow sensor

100

dosing inlet

110

torque sensor

QM

process control computer

µC

electronic dosing control

Claims (15)

Metering device with an eccentric screw pump (1), which has a delivery stator (60) and a delivery rotor (50), the delivery rotor (50) being rotatable relative to the delivery stator (60) by means of a drive (10), characterized by a torque sensor (110 ) for detecting the torque effectively applied to the conveyor rotor (50) or the conveyor stator (60). dosing device claim 1 , characterized in that the torque sensor (110) is non-positively integrated in a rotor train between the drive (10) and the eccentric screw pump (1). dosing device claim 2 , characterized in that the torque sensor (110) via adapting clutches (30) serially between the drive (10) and the eccentric screw pump (1) is introduced. dosing device claim 2 or 3 , characterized in that the torque sensor (110) is subsequently insertable. Dosing device according to one or more of the preceding claims , characterized by a rotation angle sensor (120) for the conveyor rotor (50). 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. Sensory method for optimizing a dosing process , characterized by ongoing or periodic detection and logging of the chronological progression of a torque effectively applied to a delivery rotor (50) or to a delivery stator (60) of an eccentric screw pump (1) of a dosing device. procedure after claim 7 characterized by a detection and logging of the time course of a rotation angle or a speed of the conveyor rotor (50). procedure after claim 7 or 8th characterized in that after active excitation, an impulse response analysis is carried out to determine the status of the dosing device, in particular the eccentric screw pump (1). Procedure according to one of Claims 7 until 9 characterized in that the utilization of the course of the torque takes place as part of a self-learning control process of the metering. Procedure according to one of Claims 7 until 10 characterized in that a service and maintenance plan is created with the help of the course of the torque. Procedure according to one of Claims 7 until 11 characterized in that a state of a dosing material is monitored with the aid of the torque or the course of the torque, the state preferably being a viscosity. Procedure according to one of Claims 7 until 12 characterized in that at least one state of a dosing material is monitored, the state being a dynamic pressure or a temperature or a delivery volume. procedure after claim 12 or 13 characterized in that a service and maintenance plan is created and/or adjusted with the aid of the condition of the dosing material. Procedure according to one of Claims 7 until 14 characterized in that a total failure is signaled immediately.

Images