Method for Operating a Dipping Tank and Device for Operating a Dipping Tank

[0001] The invention relates to a method for operating a dipping tank. Furthermore, the invention relates to a device for operating a dipping tank.

[0002] Dipping tanks are used in automobile manufacturing, for example, for carrying out various manufacturing steps on a shell of the motor vehicle. In a pretreatment tank, the shell coming from the body construction can thus be cleaned, degreased, and usually also prepared with a phosphatization for subsequent cathodic dip painting (CDP) or a CDP coating. The cathodic dip painting takes place after the pretreatment. During this painting, a primer layer, which serves for corrosion protection, is deposited in the corresponding dipping tank by means of electric current on the body, which can be viewed as a component.

[0003] The component or the body of the motor vehicle is typically introduced by means of a conveyor technology into the dipping tank, wherein in particular multiple components are dipped in succession. This dipping process can be carried out by dipping at a defined angle and/or by means of a rotation conveyor technology.

[0004] To avoid sedimentation of solids in the dipping tank and to heat or cool the liquid or the fluid, which fills the dipping tank for the manufacturing step, to a specific temperature, the fluid in the dipping tank is circulated, for example, via heat exchangers and/or filter elements. In a dipping tank of the pretreatment, for example, the phosphatization and/or the degreasing, for example, in addition to the continuous circulation, nozzles installed laterally and/or on the tank bottom are used in order to guarantee a direct or increased incident flow of the manufacturing fluid on the component.

[0005] To achieve a particularly high quality of the painting, it is advantageous to optimize the flow against or around the component. Some media or fluids, in particular in the pretreatment, have special requirements with respect to the incident flow against a surface with respect to the component. Nozzles in the CDP dipping tank can thus ensure a uniform distribution of paint particles and transport an electrolysis gas or process gas arising during the coating or the painting away from the surface of the component. These process gas residues can result in problems during the dip painting and can possibly prevent layer formation.

[0006] Since not only the incident flow of the nozzles has an influence on the flow around the body, but also the specified movement of the conveyor technology, knowing the flow speeds in the dipping tank is advantageous. These can be complexly calculated by means of a 3D-CFD simulation, for example.

[0007] Furthermore, DE 10 2017 005 723 A1 discloses a method for determining a flow speed of a fluid relative to a body of a motor vehicle.

[0008] The object of the present invention is to provide a method and a device for operating a dipping tank, in which a flow speed and an incident flow speed dependent thereon at a component in the dipping tank can be ascertained particularly precisely, wherein the three spatial directions are resolved so that an incident flow direction can be detected.

[0009] A first aspect of the invention relates to a method for operating a dipping tank, which, when filled with a manufacturing fluid, is used to carry out a manufacturing step on a component. The method according to the invention comprises multiple steps.

[0010] In a first step, a measuring device is introduced into a part of the dipping tank filled with the manufacturing fluid and/or a measuring fluid. In a second step, direction-dependent flow speeds are ascertained along the spatial directions in at least one volume area of the filled part by the measuring device, wherein the component is at least partially arranged in the volume area during the manufacturing step. However, the measurement or the ascertainment of the direction-dependent flow speed can be carried out without the component. In a third step, at least one incident flow speed of the manufacturing fluid on the component is determined on the basis of the ascertained direction-dependent flow speeds.

[0011] The volume area represents a measurement volume within which the direction-dependent flow speeds are ascertained. The measurement volume can move in the part or can be stationary. Thus, on the one hand, a tank basic flow can be ascertained, which can be used to optimize the dipping tank in order to advantageously design a circulation, an asymmetry, a filter performance, and/or a nozzle throughput of the different nozzles. On the other hand, the flow can be ascertained for one determined fixed point (or multiple fixed points) on the component, in particular a body, which is/are significantly influenced by the tank basic flow and a conveying speed.

[0012] In other words, a method is presented which can be used in particular to determine a flow in a dipping tank in order to thus carry out or operate the dipping tank or a manufacture in which the dipping tank is used. The dipping tank is thus used for a manufacturing step of a manufacture, wherein in particular a flow in a manufacturing fluid at least partially filling the dipping tank can be present due to the manufacturing step or for the manufacturing step and a flow measuring device—the measuring device—is used in order to determine a flow speed in a volume area. The area of the measuring device—for example, a sensor, in particular a sound sensor—sensitive for the measurement of the flow speeds is positioned at a location in the dipping tank relevant for the flow speed, which is filled at least partially and in particular up to the relevant location with the manufacturing fluid and/or a measuring fluid. The relevant location can be located, for example, in the dipping tank to determine the tank flow or on a component to be examined, in order to determine the conditions prevailing their of the superposition of the conveying speed with the tank flow.

[0013] The flow speeds can then be determined in a volume area at the location, wherein the flow and thus an incident flow speed is determined at least in the volume area or the measurement volume in which a measurement point is located.

[0014] A relationship between the direction-dependent flow speed and the incident flow speed at the component can occur in that, for example, the measuring device is used in a stationary or fixed manner in the dipping tank to determine the direction-dependent flow speeds but the component is conveyed with a corresponding relative speed through the dipping tank, which results in a different speed. In addition, the tank basic flow can be present, for example, due to circulation and/or nozzles.

[0015] Thus, for example, the incident flow speed can be inferred or converted from the flow speed by means of variables, such as a component speed, wherein this can only be possible conditionally if the flow is highly turbulent, for example. This is particularly advantageously possible if flow induced by the incident flow were friction-free (potential) flow.

[0016] In particular the third step of the method, for example, can be carried out by means of a suitable control device. This can be designed, for example, for executing evaluation software. This can filter the ascertained direction-dependent flow speeds for measurement errors and/or carry out a “Reynolds averaging” and/or represent turbulent fluctuations. Furthermore, turbulent kinetic energy can be calculated via a stress tensor. The measured values can therefore be represented and checked for plausibility. For example, a 3D-CFD simulation can be used for verification and/or validation of the results of the method according to the invention.

[0017] To ensure advantageous dip painting of a body, which forms the component, an advantageous flow in the dipping tank is helpful. A flow can now be detected with particularly high resolution and in all three spatial directions by the method according to the invention.

[0018] The invention is based on the finding that the circulating flow around a body by respective manufacturing fluids in respective dipping tanks is relevant for the painting plant passage. It is therefore advantageous to detect the current status of the respective circulating flow or incident flow and associated flow speeds in the respective dipping tank. An incident flow can thus possibly be adapted or optimized on the basis of the ascertained flow speeds or the at least one incident flow speed on the component, which is in particular direction-dependent. This is particularly advantageously enabled by the method presented.

[0019] In practice, complex turbulent effects can occur in the dipping tank; it is therefore advantageous to detect the flow with high resolution in all three spatial directions. Conventional impeller anemometers are not capable of this, since they have to be aligned in the main flow direction and moreover negatively mechanically influence the flow. Other optical measuring means or heated wire anemometers are not possible for use in the painting plant due to continuous production or particle feed and/or the composition of the manufacturing fluid. An impeller anemometer thus does not keep up, for example, due to turbulence of the inertia thus caused in the fluid. This is bypassed by a particularly suitable measuring device in the method, so that a particularly advantageous determination, in particular with high resolution, is enabled by the method according to the invention along all or the three spatial directions in the dipping tank.

[0020] It has proven to be an advantageous embodiment of the method if an acoustic Doppler velocimeter is used as the measuring device, which has a sound source for emitting sound pulses and multiple spatially separated sound receivers, in particular arranged around the volume area. In other words, the direction-dependent flow speeds are ascertained with the aid of the acoustic Doppler velocimeter on the basis of sound pulses. An acoustic Doppler velocimeter measures a speed of the fluid or the liquid by using the physical principle of the Doppler effect. The Doppler effect or the Doppler shift represents a frequency change of a sound wave when the source of the sound waves moves in relation to an observer or a sound receiver. The sound wave frequency thus increases in the case of approaching periodic sound waves, whereas the sound wave frequency decreases in the case of sound waves moving away.

[0021] If a signal emitted by the sound source propagates in the fluid, its movement state is thus to be taken into consideration or reconstructed. The acoustic Doppler velocimeter makes use of this principle in that it transmits brief sound pulses of a specific frequency to the manufacturing fluid or the measurement fluid by means of the sound source. The sound pulses are in particular not reflected from the respective fluid itself, but rather by passive tracers or scattering elements which represent particles in the fluid. These tracers can represent, for example, floating sediment particles or paint particles in the manufacturing fluid, which generally move at the same average speed as the manufacturing fluid or the measurement fluid. The flow speed of the fluid can therefore be ascertained by measuring the speed of a tracer. Thus, due to the use of the acoustic Doppler velocimeter, in particular a phase difference, which can be evaluated, for example, by a control device, is detected on the basis of the Doppler shift as the measurement signal of the measuring device.

[0022] A foundation for estimating the flow speeds is thus provided by the phase difference between two emitted pulses, wherein in particular the emitted pulses are coherent. In particular, the multiple sound receivers are three sound receivers, which due to their arrangement, in particular due to the spatial separation around the volume element, can convert the sound pulses or the signal into a chronological movement profile of a tracer within the volume element or the control volume. Due to the phase difference ΔΦ, the flow speeds v can be expressed as a function of the transmitted frequency F and the speed of sound of the manufacturing fluid or the measurement fluid (speed of sound C) by:

$v=\frac{\Delta \Phi C}{4\pi F\Delta t}$

[0023] It is an advantage for the method that in particular a chronologically resolved flow speed can be contactlessly measured at a point or the volume element in all three spatial directions within the manufacturing fluid. A flow is thus not negatively influenced by a measuring device itself, due to which the flow speed can be measured particularly precisely, for example.

[0024] In a further advantageous embodiment of the invention, a speed of sound of the manufacturing fluid and/or the measurement fluid is ascertained and the flow speed is ascertained as a function of the speed of sound. In other words, the flow speed per spatial direction can be ascertained via the speed of sound of the respective fluid. As a result, the speed of sound in the medium to be measured, thus the manufacturing fluid and/or the measurement fluid, is related to the phase difference ascertained by the Doppler effect and is thus to be used to determine the flow speeds. The advantage thus results that the flow speeds are ascertainable particularly precisely by the method.

[0025] In a further advantageous embodiment of the invention, scattering elements are introduced into the manufacturing fluid and/or the measurement fluid. In other words, elements which enable the reflection of sound waves, thus can be used as tracers, are introduced into the medium in which the direction-dependent flow speeds are to be determined. The scattering elements can be, for example, solid particles, such as paint particles and/or sediment particles or the like. The advantage thus results that in particular depending on the property of the manufacturing fluid and/or the measurement fluid, an ascertainment of the direction-dependent flow speeds can be carried out in a particularly advantageous manner.

[0026] In a further advantageous embodiment of the invention, the measuring device is moved through the dipping tank along a trajectory and/or movement direction of the component. In other words, the measuring device executes a movement, in particular during the determination of the direction-dependent flow speed, which corresponds to the movement of the component during the manufacturing step through the dipping tank. It can thus be that the component, which is designed in particular as a vehicle body, is rotated by means of a conveyor system through the dipping tank, wherein corresponding incident flows or circulating flows can occur. The method can now be carried out in such a way that these movements can be simulated or carried out, by which a particularly advantageous determination of the incident flow speed of the manufacturing fluid on the component can be ascertained. The advantage thus results that the method can particularly precisely ascertain the at least one incident flow speed on the component.

[0027] In a further advantageous embodiment of the invention, the measuring device is fastened on the component and/or a dummy during the ascertainment of the direction-dependent flow speed. In other words, the measuring device is arranged in the dipping tank in such a way that at least one measuring area or the detection area of the volume area is arranged on the component or a dummy or a framework which can, for example, execute the trajectory of the component. The dummy can thus also be designed, for example, as a stationary framework and can thus advantageously be used to ascertain the tank basic flow (without component). An alternative thus results to a static arrangement or fixed arrangement of the measuring device in the dipping tank, so that a particularly precise determination of the at least one incident flow speed or an ascertainment of the flow speeds is enabled.

[0028] In a further advantageous embodiment of the invention, at least one nozzle arranged in the dipping tank, through which the manufacturing fluid can be conveyed and which can in particular influence at least one incident flow speed at the component, is aligned on the basis of the at least one determined incident flow speed. In other words, the nozzle is aligned accordingly in the dipping tank, for example, in its orientation and/or in its ejection speed of the fluid. It can thus be advantageous, for example, during the degreasing and/or during the depositing of the particles by means of the cathodic dip painting if a specific incident flow using the respective fluid is achieved on the component, which can be influenced by the nozzle. The nozzle can advantageously be aligned by means of the knowledge of the at least one incident flow speed, which is determinable particularly precisely by the method. The advantage thus results that the dipping tank can be operated or the manufacturing step can be carried out particularly advantageously by means of the method.

[0029] In a further advantageous embodiment of the invention, at least one suction unit or filter system arranged in the dipping tank, through which in particular the manufacturing fluid can also be conveyed, is aligned on the basis of the at least one determined incident flow speed. In other words, suction units or filters are arranged in the dipping tank, by which, for example, the manufacturing fluid is circulated in order to ensure a uniform quality or avoid contamination. These can also have influence on an incident flow speed, so that, for example, a suction unit or the intensity of a suction unit can be varied by the specific incident flow speed. The advantage thus results that the dipping tank can be particularly advantageously operated and therefore the manufacturing step can advantageously be carried out. For example, a suction unit can advantageously be designed to better circulate and/or filter the dipping tank by static measurement of the dipping tank.

[0030] In a further advantageous embodiment of the invention, the dipping tank and/or the manufacturing fluid are used for cathodic dip painting of the component. In other words, the dipping tank is a dipping tank of cathodic dip painting, so that painting of the component can be carried out by the method during the operation of the dipping tank. The dipping tank can also be such that it can be used for the pretreatment for the cathodic dip painting, for example, for degreasing. Furthermore, the method is applicable to alternative embodiments of a dipping tank. The advantage thus results that the method can both be used particularly advantageously for painting the component and also particularly flexibly.

[0031] A second aspect of the invention relates to a device for operating a dipping tank, which comprises a control device and a measuring device and is designed to carry out a method according to the first aspect of the invention.

[0032] Advantageous embodiments and refinements of the first aspect of the invention are to be viewed as advantageous embodiments and refinements of the second aspect of the invention and vice versa.

[0033] Further features of the invention result from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned hereinafter in the description of the figures and/or shown solely in the figures are usable not only in the respective specified combination but also in other combinations or alone.

[0034] The invention will now be explained in more detail on the basis of a preferred exemplary embodiment and with reference to the drawings.

[0038] FIG. 1 at least partially shows a schematic view of a dipping tank 1, which is filled with a manufacturing fluid 2 to carry out a manufacturing step on a component 3, which is designed here as a vehicle body. FIG. 1 serves to illustrate both a method for operating the dipping tank 1 and a device for operating the dipping tank 1. The device comprises a measuring device 4 and a control device 5 and is designed to carry out the method, which comprises multiple steps.

[0039] In a first step of the method, the measuring device 4 is introduced into a part of the dipping tank 1 filled with the manufacturing fluid 2 and/or a measurement fluid. In a second step, direction-dependent flow speeds are ascertained along the spatial directions in at least one volume area 6 of the filled part by the measuring device 4, wherein the component 3 is at least partially arranged in the volume area 6 or at least adjoins this volume area 6 during the manufacturing step. In a third step of the method, at least one incident flow speed of the manufacturing fluid at the component 3 is determined on the basis of the ascertained direction-dependent flow speeds. This can have the result that the component 3 is moved at a certain conveyance speed through the dipping tank 1, due to which a difference between flow speed and correspondingly incident flow speed or circulating flow speed occurring in the same spatial direction is possible.

[0040] The method is thus used to determine a flow in a dipping tank 1, in order to thus carry out or operate the dipping tank 1 or a manufacture in which the dipping tank 1 is used.

[0041] In order that the flow speeds can be carried out particularly advantageously and without interference, for example, due to the turbulence in the dipping tank 1 due to the flow around the component 3, the measuring device 4 shown in FIG. 2 and FIG. 3 is advantageously used, which is designed as an acoustic Doppler velocimeter, which has a sound source 7 for emitting sound pulses and multiple spatially separated sound receivers 8.

[0042] Since the component 3 is a motor vehicle body, the dipping tank 1 is used in particular in preparing for or carrying out cathodic dip painting. It is advantageous here for the most advantageous possible painting if occurring process gas, in particular hydrogen, can escape and does not accumulate at the component 3 or the body. This can be achieved, for example, by at least one corresponding incident flow speed. Furthermore, the knowledge of the at least one incident flow speed can be advantageous for a particle flow and uniform painting.

[0043] It is thus advantageous to detect the flow for painting applications at high resolution in all three spatial directions, which is enabled by the presented method and the presented device, wherein the ascertainment of the flow speeds is carried out by means of sound waves. A distance between sound receiver 8 and volume area 6 or volume area 6 and sound source 7 is advantageously to be selected in such a way that a corresponding signal arrives at the respective sound receivers 8. It is therefore furthermore advantageous if the respective liquid, thus the manufacturing fluid 2 and/or the measurement fluid, is checked for the capability of measurability or for the use for the measurement, by which a signal-to-noise ratio (abbreviated SNR) can be set high enough to obtain a good quality measurement.

[0044] Moreover, the speed of sound of the manufacturing fluid 2 to be measured or the measurement fluid is to be determined, since this specifies a phase difference, which characterizes a time-of-flight as a function of the flow speed to the respective one of the total of three sound receivers 8. In one embodiment of the method, the speed of sound of the corresponding medium, thus of the manufacturing fluid 2 and/or the measurement fluid, can be ascertained, for example, by means of a further measuring device in order to determine the direction-dependent flow speeds as a function of the speed of sound.

[0045] Furthermore, the method can be carried out in such a way that the signal-to-noise ratio is improved by introducing corresponding scattering elements into the manufacturing fluid 2 and/or the measurement fluid. The measurement is thus carried out by means of the acoustic Doppler velocimeter by reflection of sound waves emitted by the sound source 7 and reflected at the scattering elements in the volume element 6. The reflections of the sound waves thus occur in particular due to tracers or the scattering elements and not due to the manufacturing fluid 2 or the measurement fluid itself. Introducing scattering elements into the manufacturing fluid and/or the measurement fluid can thus be an advantage.

[0046] Depending on the type of the movement of the component 3 or its conveyance through the dipping tank 1, it can be advantageous for the method if the measuring device 4, as shown in FIG. 1, is fastened on the component 3—for example a front flap—and/or alternatively on a dummy, such as a framework. It is thus made possible that the measuring device 4 is moved, for example, along a trajectory and/or movement direction of the component 3 through the dipping tank 1. In this way, the at least one incident flow speed can be ascertained particularly precisely.

[0047] The method can thus particularly advantageously be used to align a nozzle arranged in the dipping tank 1, through which the manufacturing fluid can be conveyed, on the basis of the at least one determined incident flow speed. Furthermore, it is an advantage to align at least one suction unit arranged in the dipping tank on the basis of the at least one determined incident flow speed.

[0048] As it was possible to show, a quality of the component 3 or the motor vehicle body can advantageously be influenced by the method or the device. The measuring means, thus in particular the measuring device 4, can thus be mounted on the component 3 and the incident flow can be directly measured during startup of the manufacturing process to be carried out by means of the dipping tank 1. A nozzle picture can be adapted and checked by the measured values, for example, by means of a later measurement that can also be carried out by the method. Industrial dipping facilities can thus possibly perform corresponding settings on the basis of the data ascertained by the method or determined incident flow speeds in the dipping tank, without the tank having to be drained and refilled. It is thus advantageously possible to detect the vehicle flow in the dipping paint by way of the method and the device.

• [0049] 1 dipping tank
• [0050] 2 manufacturing fluid
• [0051] 3 component
• [0052] 4 measuring device
• [0053] 5 control device
• [0054] 6 volume area
• [0055] 7 sound source
• [0056] 8 sound receiver