SYSTEM FOR MONITORING THE MATERIAL PARAMETERS AND / OR HOMOGENEITY OF A CHANNEL-FED SUSPENSION

Description

[0001] The invention relates to a system with a measuring system for monitoring the material parameters and / or homogeneity of a suspension conveyed through a channel. The suspension can consist of slurries and extrudates intended for the production of electrodes for electrical accumulators or electrical energy storage devices (batteries).

[0002] Electromobility, in particular, is experiencing rapid growth with the current state of technology. This results in a broad spectrum of research and development in the field of batteries. Meeting safety and quality standards is of paramount importance.

[0003] The basic components of a battery consist of an anode, cathode, electrolyte, and a separator. The anode and cathode materials are located on a carrier film. The carrier film is typically made of copper for the anode and aluminum for the cathode. Currently, the electrode material is coated onto the surface of a carrier film using a film casting process. This process results in a high solvent content. An extrusion process, which can be implemented with a significantly lower solvent content, produces and conveys the material using an extruder. The electrode material is applied to the carrier film using a special tool.

[0004] During the extrusion process, inhomogeneities can occur in the material, affecting its properties and thus the subsequent functionality of the accumulator. Delayed inspection and detection of such defects after application leads to the production of unusable material, negatively impacting both economic efficiency and the environment.

[0005] Current technology does not allow for sufficiently precise testing of the extruded material during the ongoing process. Material testing is currently performed via a subsequent functional test of the already manufactured electrodes. This allows the quality of the accumulator to be determined based on reference values ​​and experience. If the expected quality is not met, further investigations of the material must be carried out. The manufacturing process is then adjusted accordingly. Electrode material is produced in parallel with the coating process and the subsequent functional testing. This ensures an uninterrupted process flow. A disadvantage is the late detection of defects, which results in the production of defective and unusable material.

[0006] Testing the extruded electrode material using non-destructive testing methods during the manufacturing process is not possible with the current state of the art.

[0007] These problems also occur when monitoring the quality of other suspensions or extrudates.

[0008] US patent 5 333 502 A discloses a device and a method for modifying the properties of a particle-containing liquid that is stored in a tank or flows through a pipe.

[0009] It is therefore an object of the invention to provide possibilities for monitoring a suspension conveyed through a channel, with which errors or deviations from a certain quality-related consistency can be detected and, if necessary, compensated for and / or material parameters can be determined before a product is finished using the respective suspension.

[0010] According to the invention, this problem is solved with a system having the features of claim 1. Advantageous embodiments and further developments of the invention can be realized with features specified in dependent claims.

[0011] The challenge lies in developing a measurement system that records data regarding material properties. By simultaneously recording eddy current and ultrasonic signals with the measurement system, it is possible to determine the material properties of the conveyed, particularly extruded, suspension during its conveying process. This suspension can then be used to produce electrodes for electrical accumulators or electrical energy storage devices.

[0012] The measuring system is divided into an eddy current and an ultrasonic sensor system. These can be arranged or fixed together in a single housing. An eddy current sensor system is used to determine the electrical, magnetic, and dielectric properties. An ultrasonic sensor system is used to determine mechanical properties. These two sensor systems are positioned between the extruder and the connected die. The suspension is conveyed as extrudate through a channel, which can then be configured as a measuring tube. In any case, the two sensor systems are arranged sequentially in the direction of suspension flow. The ultrasonic sensor system can be positioned either upstream or downstream of the eddy current sensor system in the direction of suspension flow.

[0013] Both sensor systems require no direct intervention in the process. Compared to previous material testing methods, this inline testing allows for immediate adjustment of process parameters or initiation of a production stoppage in the event of suspension consistency errors, particularly inhomogeneities within a volume. This prevents the production of unusable material, leading to improved efficiency and reduced environmental impact.

[0014] A sensor system designed for eddy current detection can be formed with at least one electrical transmitting coil and at least one electrical receiving coil, or with a giant magnetoresistive sensor (GMR), anisotropic magnetoresistive sensor (AMR), superconducting quantum interference sensor (SQUID), or a Hall sensor.

[0015] The generation of a magnetic field (primary field) by a current-carrying electrical transmitting coil induces eddy currents and displacement currents in a conductive object under test. This, in turn, generates a second magnetic field (secondary field) due to electrical induction. The effect resulting from the interaction of these two magnetic fields can be utilized in the eddy current method. The strength of the secondary magnetic field, which is picked up by the receiving coil, depends on the eddy current and displacement current losses in the object under test, i.e., the suspension within the respective detection range during its conveyance. These losses are defined by the electrical, magnetic, and dielectric properties of the suspension.

[0016] Furthermore, the eddy current method can be used to perform either an absolute or a differential measurement. In absolute measurement, a fault / material change has an absolute amplifying or attenuating effect. Differential measurement, through compensation of the magnetic fields (primary and secondary fields), enables the direct recording of the fault signal. The invention described here allows for the realization of both absolute and / or differential measurement. In absolute measurement, the transmitting and receiving coils should be arranged in a common sensor module. The transmitting coil should be the outer coil, and the receiving coil the inner coil. The electrical voltage induced in the respective receiving coil contains not only the relevant fault signal voltage (information about material changes, material composition, cracks, voids, material defects) but also the induced electrical coil voltage, as well as interference signals, etc.This property can lead to small material variations not being noticeable.

[0017] In differential measurement, two identical absolute coils can be used as transmitter and receiver coils, connected in opposite directions. This leads to compensation of the transmit and receive fields. Thus, at the beginning of the measurement, or with a homogeneous suspension, especially a homogeneous extrudate material, the receiver coil voltage is zero. This makes it possible to detect and evaluate small variations in consistency and thus small amplitude deflections, since only the error signal voltage, which results from inhomogeneities, is used. Both methods of eddy current testing can be implemented within the mechanical free space of the sensor system.

[0018] The integration of the eddy current measurement method with a corresponding sensor system can be achieved using sensor modules. These modules can be fixed within a housing in the eddy current measurement area, which can be positioned or attached to the respective channel. These modules can consist of several sensors, each comprising a transmitting and receiving coil. They contain a coil pair adapted to the specific test task and an interface to the electronic evaluation unit. The coil modules can have an opening, particularly a bore, through which the respective channel or measuring tube can be guided with a precise fit. An external flow sensor can be installed in the area of ​​the opening / bore. A generously dimensioned mechanical clearance in the eddy current measurement area allows for the use of preferably different sensor systems designed for eddy current measurement.Using several differently configured sensor modules, adaptation to different suspensions or suspension compositions can be achieved by selecting a suitable sensor module for monitoring that has the highest possible sensitivity for the respective suspension.

[0019] It can also include at least one transmitting coil formed or arranged around the channel circumference and a receiving coil inside the transmitting coil, integrated into the channel wall, received in grooves on the outer wall of the channel or arranged inside the channel.

[0020] Non-destructive testing and investigation of the respective suspension, particularly regarding its mechanical properties, can be carried out using ultrasound. Sound waves are emitted using high-frequency pulses. Excitation with a pulsed sound causes pulse-echo signals to penetrate the suspension material. Due to differing material characteristics, propagation delays and amplitude attenuations of the sound waves occur.

[0021] The reflection and transmission signals can be used for evaluation.

[0022] If an ultrasonic transducer functions as both a transmitter and receiver, the reflection signals of the sound waves can be captured and evaluated using this single transducer once it has switched from transmit to receive mode. For the analysis of transmission signals, two ultrasonic transducers are used. One serves as the transmitter, and the opposite transducer acts as the receiver of the sound wave signals. The invention enables the near-simultaneous acquisition of reflection and transmission signals. Due to inhomogeneities or defects in the suspension consistency, the characteristics and direction of the transmitted sound pulse change compared to detected sound measurement signals that are representative of a correct suspension consistency. These altered measurement signals can provide information about the material properties.

[0023] The adaptation of the ultrasonic transducers to the sensor system should take place within the ultrasonic measurement range. Within this range, the outer dimensions of the channel, particularly the outer radius of a measuring tube, can be concave or flattened (i.e., planar) for improved coupling. Planar surfaces between the ultrasonic transducer and the outer channel wall ensure good coupling both in and out.

[0024] If the surface(s) of the ultrasonic transducer(s), through which the sound waves are emitted and detected, are concave and, complementarily, the outer wall of the channel in the area where an ultrasonic transducer is located is convexly curved, a focusing of the sound waves can be achieved, which can lead to an increase in measurement sensitivity.

[0025] Due to the need for a coupling medium to couple the ultrasound, a closed area should be provided on a housing in which the ultrasound transducer(s) is arranged and held.

[0026] Utilizing the aforementioned properties, the measuring system according to the invention can be arranged at the outlet of an extruder. This allows the electrical and mechanical properties of a suspension as an extrudate to be monitored during the manufacturing process. An exemplary application is the production of battery electrodes. These consist of an electrically conductive carrier film with applied electrode material. An extruder can be used to produce such electrode material. The aim of the extrusion process is the homogenization and dispersion of the components with which the extrudate, as an example of a suspension, can be monitored. The testing process plays a fundamental role in meeting the quality and safety standards of the batteries produced in this way. This testing process can be carried out using the invention.This enables material characterization through the combined application of ultrasound and eddy current methods. This approach allows conclusions to be drawn about the electrical and mechanical properties as well as the homogeneity. The acquired measurement signals can be evaluated using electromagnetic and acoustic impedance spectroscopy. This type of spectroscopy aims to decompose signals into their constituent components. Significant regions where differentiation is possible can be selected for signal evaluation. For example, regions can be selected for evaluation in which a specific, predefined threshold value—also defined for the respective suspension—is exceeded or fallen below within a given time interval.

[0027] The invention will be explained in more detail below by way of example.

[0028] This shows: Figure 1 an example of a housing for receiving and attaching the two sensor systems to a measuring tube as an example of a channel; Figure 2 an example of a housing part for receiving a sensor module for a sensor system designed for eddy current detection and Figure 3 a measuring tube.

[0029] A measuring system is installed at the outlet of an extruder, which conveys a suspension intended for the formation of electrodes for an electrical energy storage device through a measuring tube 3, for example, a channel. The measuring system can be attached to a channel located between the extruder outlet and the channel outlet, which is typically a die. In this area, the material / extrudate is to be tested for homogeneity. All extruder tools can be connected downstream of the measuring system in the conveying direction. In the specific case of battery electrode production, electrode foils are formed using a slot die.

[0030] The electrode material used consists of active material, conductive carbon black, binder, and solvent. Depending on the composition, this results in a solids content of between 80% and 90% by mass. Using a slot die, electrodes are formed in the form of films with a thickness of 100 µm to 600 µm in the green state, which are then applied to carrier films.

[0031] To characterize the material during the extrusion process, a measuring system with combined ultrasonic and eddy current sensors is used. This allows for the observation of a broad spectrum of the characteristics of the electrode material conveyed to the exit die by the extruder. The integration of the measuring system is designed to minimize the impact on the extrusion process. For this reason, the measuring section is kept short.

[0032] The flow channel was adapted to the extruder outlet. For this purpose, an interchangeable measuring tube 3 is provided as an example of a channel that can be adapted to the respective sensor systems used (ultrasonic and eddy current). This interchangeability allows the material of measuring tube 3 to be adapted to the specific application, affecting its mechanical, electrical, magnetic, and / or acoustic properties. The ultrasonic and eddy current sensor systems were designed with adapted geometries. This setup is described in the following sections.

[0033] The sensor system, designed for ultrasonic measurement, uses two ultrasonic transducers arranged diametrically opposite each other in this example. This enables the recording of reflection and transmission signals of sound waves. Oil is used as the coupling medium between the ultrasonic transducers and the outer wall of the measuring tube 3. This necessitates a mechanical separation of the measuring area. Sealing can be achieved with shaft seals. Planar surfaces 3.1 have been formed on the measuring tube 3 in the ultrasonic measuring area to create parallel surfaces between the ultrasonic transducers and the measuring tube surface in the coupling area. This aims to reduce changes in the wave propagation direction within the medium. Contact and immersion ultrasonic transducers can be used for this sensor system. Suitable frequencies for the ultrasonic transducers can be selected depending on the application.In applications involving battery electrode manufacturing, ultrasonic transducers with resonant frequencies in the range of 1 MHz to 4 MHz are suitable for monitoring the homogeneity of the extruded electrode material. During measurements, the ultrasonic transducers are in contact with the outer surface of the measuring tube 3 at the planar surfaces 3.1. Only the coupling medium is present between the surfaces of the measuring tube 3 and the sensitive surfaces of the ultrasonic transducers. This position must be checked before each use to prevent energy losses of the emitted and detected sound waves in an excessively large gap between the ultrasonic transducer and the planar surface 3.1 of the measuring tube 3. The reflection and transmission signals are used for evaluation. The signals should be recorded almost simultaneously by pulsed operation during the emission of sound waves.An ultrasonic transducer experiences a vibrational motion due to the piezoelectric effect, generating mechanical waves that are emitted as sound waves through the wall of the measuring tube 3 and the extrudate conveyed through it. A second ultrasonic transducer, positioned diametrically opposite the emitting transducer, can detect the sound waves emitted through the measuring tube wall and the extrudate in transmission mode. During periods of inactivity, when the emitting transducer is not emitting sound waves, the emitting transducer can detect sound waves reflected from the measuring tube wall. In this receiving mode, backscatter information can be detected.

[0034] To implement an eddy current sensor system, sufficient mechanical clearance is provided in the housing 1, which can be attached to the measuring tube 3 to accommodate a measuring system according to the invention. This clearance allows the integration of various electrical coil systems as sensor modules designed for eddy current detection. Through-coils are used in this sensor system. That is, the electrical transmitting and receiving coils used enclose the measuring tube 3. They have an inner diameter of approximately 28.1 mm and, depending on the number of turns, an outer diameter of 29.5 mm to 33.5 mm. In this specific application of battery electrode manufacturing, copper wire with a diameter of 250 µm is used as the coil wire. The number of turns in the individual coils varies from 25 n to 200 n. Inductances in the range of 25 µH to 200 µH are currently achieved.The degree of electrical contact with the coils plays a crucial role in eddy current technology; therefore, the distance between the inner diameter of the receiver coil and the outer diameter of the measuring tube 3 should be as small as possible. For instrumentation and protection, the coils are used in the form of specially manufactured sensor modules. A transmitting coil and a receiver coil can be accommodated in a housing part 2. For this purpose, an opening in the form of a recess 2.1 is provided on one side of the housing part 2, into which a transmitting coil and a receiver coil can be inserted with a precise fit. Appropriate clearances are provided in the area of ​​the recess 2.1 for the electrical contact of the two coils, and bores are provided through which electrical leads to the two coils are routed.The respective transmitting coil is connected to a frequency generator and the receiving coil to a measuring device for determining the complex receiver coil impedance (eddy current measuring device), which can be components of an electronic evaluation unit (both not shown).

[0035] One or more sensor modules can then be inserted into a suitably dimensioned free space 1.1 of the housing 1 and fixed therein. Several sensor modules can be arranged sequentially in the conveying direction of the electrode material, each in a parallel orientation to the others. Identical sensor modules can be arranged in this way. However, differently configured sensor modules can also be arranged in this manner.

[0036] The measuring tube 3 can be inserted through bores 1.2 in the housing 1. The sensor modules are dimensioned so that the measuring tube 3 can also be guided through the sensor module(s).

[0037] In a form not shown, at least one receiver coil can also be embedded in the wall of the measuring tube or inserted into grooves formed in the outer wall of the measuring tube 3. In a sensor module, a receiver coil can then be inserted into a housing part 2.

[0038] Eddy current technology uses a transmitting coil and a receiving coil to examine materials. The positioning of these two coils relative to each other is, in principle, freely selectable, thus allowing for a high degree of flexibility in the development of an eddy current sensor system. A distinction can be made between an absolute system and a differential system. In the absolute system, the transmitting and receiving coils can be located in a single sensor module. The transmitting coil is the outer coil, and the receiving coil is the inner coil. In an absolute system, a change in the material of the extrudate has an absolute effect, either amplifying or attenuating the signal. The electrical voltage measured at the receiving coil contains not only the relevant fault signal voltage (information about material changes, cracks, voids, material defects) but also the induced electrical coil voltage, as well as interference signals, etc.This property can lead to small material variations going undetected. The differential system uses two identical absolute coils connected in opposite directions. This results in the compensation of the electromagnetic fields. Thus, at the beginning of the measurement or with homogeneous extruded material, the electrical receiver coil voltage is zero. This makes it possible to detect small material variations and therefore small amplitude deflections, since only the electrical error signal voltage is measured. Both systems can be implemented in a mechanical free space as a recess 2.1 in a housing part 2. A frequency sweep covering the range from 10 kHz to 100 MHz is used to evaluate the signals. The real part, imaginary part, and magnitude of the impedance are recorded over time.For analysis, signals in the area of ​​significant peaks (amplitude values) or when a tolerance limit is exceeded are examined more closely. These areas indicate changes such as inhomogeneities, particle shape / size changes, pressure changes, or external disturbances.

[0039] The housing 1 has two diametrically opposed bores 1.3 into which an ultrasonic transducer (not shown) is inserted and fixed in such a way that the respective active and sensitive surface comes into contact with one of the planar surfaces 3.1 that are present on the measuring tube 3 and only a coupling medium is present between these surfaces and the respective planar surface 3.1.

Claims

1. A system comprising a measuring system for monitoring the material parameters and / or homogeneity of a suspension that is conveyed through a channel, that is electrically conductive or comprises electrically conductive components, and by which an electrode of an electrical storage battery or electrical energy store is configured, an electronic evaluation unit, a channel, an extruder and an outlet nozzle, in which a sensor system configured for an ultrasound inspection has at least one ultrasonic transducer that is arranged at the outer wall of the channel for the emission of sound waves; and a sensor system that is configured for eddy current detection and that is formed with at least one electrical transmission coil and at least one electrical receiver coil or with a giant magnetoresistive sensor (GMR), an anisotropic magnetoresistive sensor (AMR), a superconducting quantum interference sensor (SQUID), or a Hall sensor is arranged upstream or downstream of the sensor system configured for the ultrasound inspection in the direction of movement of the suspension, and both sensor systems are arranged between the extruder and the connected outlet nozzle on the channel through which the suspension is conveyed as extrudate; and the sensor system configured for the ultrasound inspection and the sensor system configured for the eddy current detection are connected to the electronic evaluation unit and the electronic evaluation unit is configured to recognize flaws in the material parameters and homogeneity of the conveyed suspension by means of the measurement signals detected by both sensor systems.

2. The system in accordance with claim 1, characterized in that a second ultrasonic transducer of the sensor system configured for the ultrasound inspection is arranged at the outer channel wall diametrically opposite the other ultrasonic transducer.

3. The system in accordance with one of the preceding claims, characterized in that the ultrasonic transducer or transducers has / have a concavely arched surface that is / are arranged contacting a correspondingly convexly arched surface of the channel; or a planar surface of the ultrasonic transducer or transducers is / are arranged at a planar surface (3.1) at the outer wall of the channel.

4. The system in accordance with one of the preceding claims, characterized in that at least one transmission and receiver coil pair forms a sensor module that is configured for eddy current detection.

5. The system in accordance with one of the preceding claims, characterized in that a plurality of transmission and receiver coil pairs form a sensor module that is configured for eddy current detection, with the sensor modules being replaceably arranged in a housing (1) and / or being alternatingly operable.

6. The system in accordance with one of the preceding claims, characterized in that at least one transmission coil is formed or arranged around the channel periphery; and a receiver coil in the interior of the transmission coil is integrated in the channel wall, is received in grooves at the outer wall of the channel, or is arranged in the interior of the channel.

7. The system in accordance with one of the preceding claims, characterized in that the sensor system or systems that is / are configured for eddy current detection is / are configured for carrying out an absolute measurement and / or a difference measurement.