Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/07—Ink jet characterised by jet control
  • B41J2/125—Sensors, e.g. deflection sensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F11/00—Apparatus requiring external operation adapted at each repeated and identical operation to measure and separate a predetermined volume of fluid or fluent solid material from a supply or container, without regard to weight, and to deliver it
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F11/00—Apparatus requiring external operation adapted at each repeated and identical operation to measure and separate a predetermined volume of fluid or fluent solid material from a supply or container, without regard to weight, and to deliver it
  • G01F11/10—Apparatus requiring external operation adapted at each repeated and identical operation to measure and separate a predetermined volume of fluid or fluent solid material from a supply or container, without regard to weight, and to deliver it with measuring chambers moved during operation
  • G01F11/12—Apparatus requiring external operation adapted at each repeated and identical operation to measure and separate a predetermined volume of fluid or fluent solid material from a supply or container, without regard to weight, and to deliver it with measuring chambers moved during operation of the valve type, i.e. the separating being effected by fluid-tight or powder-tight movements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F13/00—Apparatus for measuring by volume and delivering fluids or fluent solid materials, not provided for in the preceding groups
  • G01F13/006—Apparatus for measuring by volume and delivering fluids or fluent solid materials, not provided for in the preceding groups measuring volume in function of time
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F22/00—Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
  • G01F25/0092—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume for metering by volume
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
  • G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V8/00—Prospecting or detecting by optical means
  • G01V8/10—Detecting, e.g. by using light barriers
  • G01V8/20—Detecting, e.g. by using light barriers using multiple transmitters or receivers
  • G01V8/24—Detecting, e.g. by using light barriers using multiple transmitters or receivers using optical fibres

Definitions

• the invention relates to a drop detection device for detecting droplets emerging from a nozzle of a metering valve and moving along a trajectory. Moreover, the invention relates to a method for detecting a drop, which emerges from a metering valve, preferably a micro-metering valve.
• metering valves are used.
• a metering valve comprises a nozzle at the point of discharge of the medium to be metered.
• the opening of the metering valve is released by the dispensing needle is slightly pulled out of the valve seat.
• the medium for example driven under admission pressure, can flow through the nozzle opening or valve opening.
• jet valves can be built.
• the delivery of quantities of media by the reciprocating movement of the dispensing needle or a valve tappet, wherein a quantity of media is ejected in a jet-like movement of the dispensing needle or the valve stem in the direction of the nozzle opening.
• This allows an application of defined amounts of the metering medium and over greater distances between metering valve and application surface, z. B. on a component to be machined.
• the dosing distances can vary between half a millimeter and a few millimeters. Jet valves allow a very fine dosage at high speed with complete contactlessness to the component to be machined.
• sensors for detecting the drops and corresponding evaluation processes are necessary.
• the smallest possible distance should be maintained between the metering valve and a surface of a component to be processed. This distance can vary depending on the application between 0.5 mm and 3 mm. This specification greatly limits the possible height of a drop sensor. Furthermore, the to be detected drops with diameters of sometimes less than 10 ⁇ very small. Furthermore, the velocity of the drops is very high, up to 50 m / s, resulting in an extremely short transit time through a range of a few microseconds monitored by a detecting sensor.
• the small size and high speed of the droplet cause a weak sensor signal with low signal amplitudes and an unfavorable signal-to-noise ratio, which makes a fault-proof optical detection of a drop very difficult.
• an opto-electronic sensor such as a photodetector
• close to the nozzle of the valve in order to obtain as much optical and thus electrical signal as possible after the conversion results in conflict with the small dimensions of the system. For example, it is hardly possible to position the entire evaluation electronics directly on the sensor due to the limited space available.
• the transmitter is arranged remotely from the sensor, then there is the problem that the detected electrical analog signal must be transmitted to the transmitter interference-proof.
• the sensorial measurement of drops may result in electromagnetic wave interference. If the sensors are based, for example, on the light sensor system, interference by undesired light sources can be caused. The disturbances may occur, for example, due to daylight or light from any lighting equipment.
• US 2002/0 089 561 A1 describes an apparatus for detecting drops of a printer system, wherein light is guided via optical fibers and crosses a trajectory of a drop. The intensity of the light is briefly reduced by the falling drop. This change in intensity as a function of time is detected with the aid of sensors and used to detect the drops.
• the detection is susceptible to external disturbances, such as scattered light, so that reliable drop detection is not always guaranteed.
• US Pat. No. 4,255,754 A describes monitoring the trajectory of ink droplets of an ink-jet printer.
• light is emitted via a light guide synchronized with the frequency of droplet generation in the direction of the trajectory of an ink droplet and detected by means of two light guides.
• a deviation of the ink drop from a predetermined trajectory is determined depending on a difference of shading of the light detected by the two optical fibers. Even with this procedure, it may cause interference due to stray light. It is an object of the present invention to develop a sensor arrangement for metering valves, which allows the most trouble-free drop detection.
• the optical waveguide arrangement comprises a first optical waveguide and a second optical waveguide. These are arranged opposite each other at a gap, which comprises the trajectory of the drop, arranged such that a light beam emitted by the first optical waveguide crosses the trajectory of the droplet and is then coupled into the second optical waveguide.
• the drop detection device has a light signal generating device which is set up to couple a light beam pulsed with a carrier frequency into the first optical waveguide.
• a pulsed light beam with a carrier frequency is to be understood as a pulsed light signal which changes periodically with constant characteristic parameters (eg frequency, ie the carrier frequency or also pulse frequency, amplitude), eg. B. in a certain rhythm on and off.
• the signal initially carries no information in unmodulated state except the constant characteristic parameters.
• the information to be transmitted is obtained only by the modulation, which can be realized by some kind of physical interaction of the carrier signal with an information source.
• a carrier signal can be modulated with the aid of a modulation signal or influenced by another physical disturbance, eg. B. a drop to be detected.
• modulation should be understood as a change in the carrier signal with respect to one or more of its parameters, such as the amplitude, the frequency or the phase.
• the pulse frequency or carrier frequency should be higher than the frequency of the modulation or the wavelength should be shorter than a "disturbance" of the signal caused by a drop.
• the drop detection device also comprises a light evaluation device, which is set up to evaluate the light beam coupled into the second optical waveguide in order to determine whether a drop has been emitted by the metering valve.
• a light evaluation device which is set up to evaluate the light beam coupled into the second optical waveguide in order to determine whether a drop has been emitted by the metering valve.
• the first optical waveguide has a first and a second end.
• the first end of the first optical waveguide is coupled to a light emitting device of the Lichtsignalerzeugungs- device.
• the second end of the first optical waveguide forms an emission window to the intermediate space to be monitored.
• the second optical waveguide has a first and a second end, wherein the first end of the second optical waveguide forms a detection window to the space to be monitored and the second end of the second optical waveguide is coupled to a sensor device of the light evaluation device.
• the emission window of the first optical waveguide and the detection window of the second optical waveguide can be formed by the end faces of the ends cut with conventional fiberglass cutting means.
• the fiber ends can be cut with a dedicated cutting means and then possibly a little polished.
• the emission windows of the optical waveguides can thus be produced with little effort. There are no additional optics needed for this. If such an emission window is damaged or soiled, the damage can be easily remedied by removing a piece of the light source. Waveguide cut off and then possibly polished. It is important to ensure that the window areas or the edges of the ends of the optical waveguide are as flat as possible and are oriented perpendicular to the longitudinal axis of the optical waveguide.
• the first and the second optical waveguides are arranged on the metering valve such that the pulsed light beam from the first optical waveguide strikes directly on a droplet possibly emitted by the metering valve, which is physically influenced, preferably modulated, by the droplet in some way
• "direct" means that preferably no secondary optics, such as lens systems or the like, are used before the emission window of the first light guide or in front of the detection window of the second light guide
• the second optical waveguide are arranged directly opposite one another and in alignment with one another, whereby the emission window of the first optical waveguide and the detection window of the second optical waveguide face one another, so that one of the Emission window of the first optical fiber emitted light beam to the detection window of the second optical fiber falls.
• the two optical waveguides and a trajectory of a droplet possibly emitted by the metering valve are preferably in a plane, so that a light beam emitted by the first optical waveguide hits the droplet, is modulated by the droplet and then falls onto the detection window of the second optical waveguide, from which it is coupled into the second optical waveguide.
• the light beam possibly influenced by a drop, ie modulated light beam, after being coupled into the second optical waveguide is passed on by the latter to a sensor device with which the possibly modulated light beam is first converted into a modulated electrical signal for evaluation.
• the first optical waveguide and the second optical waveguide of the droplet detection device according to the invention may comprise, for example, plastic fibers.
• the first optical waveguide and the second optical waveguide have a core diameter in a range of 0.1 mm to 3 mm, preferably 0.5 mm to 1.5 mm, more preferably 0.9 up to 1, 1 mm.
• the optical waveguides are positioned relative to the metering valve such that a defined effective cross-sectional area of the first and / or second optical waveguide is selected as a function of the respective metering process, in particular as a function of an expected drop size.
• the effective cross-sectional area of an optical waveguide is to be understood as the part of the cross-sectional area of the optical waveguide which is available for the detection of the droplet or the emission of a light beam.
• a part of the optical fiber cross-section may be covered by a nozzle adjusting nut of the metering valve, so that it does not contribute to the effective cross-sectional area.
• the signal-to-noise ratio can be optimized or a maximum throughput time of the droplet can be achieved.
• the effective area of the optical waveguides may comprise the entire area of the optical waveguide area. That is, the optical fibers are positioned relative to the metering valve such that no portion of the cross-sectional area of the optical fibers is obscured by the nozzle setting nut of the metering valve. In this case, therefore, the entire active height of the optical waveguides is utilized. This is associated with a maximum transit time of the drop through the modulation unit. This has a favorable effect on tropical detection, as more signal samples can be obtained. Logically, as much of the light modulated by the droplet should be coupled into the second optical waveguide so that the value of the amplitude of the measurement signal detected by the sensor is as large as possible and a sufficient signal-to-noise ratio is achieved.
• the effective area of the optical waveguides comprises only half the total area of the optical waveguide surface. That is, the optical fibers are positioned relative to the metering valve so that the upper half of the cross-sectional area of the optical fibers is approximately concealed by the nozzle adjusting nut of the metering valve. In this case, only half the height of the optical waveguide is used for detection. Associated with this is also compared to the use of the entire height only half as long Jerusalemszeit of the drop. Such an arrangement usually makes a good compromise between the longest possible throughput time of the drop and the required space and thus the resulting minimum distance of the nozzle.
• the effective area of the optical waveguides comprises only a fraction of the total optical waveguide area. That is, the optical waveguide surface used comprises only a fraction of the total optical waveguide surface.
• Such an arrangement may be advantageous, for example, in the case of very small drops, since there is a more favorable relationship between the active surface and the surface shadowed by the drop. This results in a stronger signal amplitude of the modulation signal, which contributes to an improved signal-to-noise ratio.
• the light emitting device of the drop detection device is adapted to convert a pulsed electrical signal into a light wave, without changing the carrier frequency and phase of the pulsed signal to a relevant extent. Since the phase position of the pulsed signal is also preferably taken into account in the evaluation of the detected signal, a stronger change in the phase of the pulsed signal during the emission of the light beam by the light emission device would influence the evaluation of the detected signal.
• the optical route, d. H. in particular the signal conversion of the signal from the electrical signal into a light signal and back again into an electrical signal between the light emission device and the sensor device causes a certain phase shift. However, this is rather low in relation to the preferably used carrier frequencies. Furthermore, in advance, d. H.
• a training phase is performed, in which the perfect phase offset between the carrier signal and the control signals of the demodulation unit for side band selection is set.
• a slight phase offset which results from the electro-optical signal conversion, be taken into account.
• the light signal generating device is designed such that the brightness of the pulsed light beam is set by selecting the size of the parameter value of the pulse width of the light pulses of the pulsed light beam. If, for example, a duty cycle with a comparatively small pulse width or short pulse duration is selected relative to the period of the signal or of the pulsed light beam, then the brightness of the pulsed light beam is selected reduced. Conversely, the brightness of the pulsed light beam can be increased by a duty cycle with a comparatively large pulse width or long pulse duration relative to the period of the signal or the pulsed light beam.
• An optimum brightness to be set relates to the residual light reaching the optoelectronic sensor, ie the light reaching the photodiode, ie the light which remains after the entire optical path and strikes the photodiode.
• the intensity of the emitted light and thus also of the received residual light must be selected so that the sensor has its maximum sensitivity at this operating point.
• the sensitivity relates to the fact that a slight fluctuation of the light intensity results in a maximum possible fluctuation of the output current of the photodiode.
• the setting should be adjusted when replacing the optical fibers.
• the drop detection device according to the invention preferably has a signal generation unit, which may preferably be part of the light signal generation device. This signal generating device is preferably configured to generate an electrical carrier signal having a defined pulse frequency or carrier frequency. On the basis of this electrical carrier signal then the pulsed light beam is generated.
• the drop detection device preferably has an evaluation unit, which may be part of the light evaluation device.
• the evaluation unit is set up to determine on the basis of the modulated measurement signal, taking into account the defined pulse frequency or carrier frequency, whether a drop has been delivered from the metering valve.
• a modulation signal based on the modulated signal can preferably be determined in a demodulation unit, which may be part of the evaluation unit, taking into account the defined pulse frequency or carrier frequency, and it is then determined on the basis of the modulation signal whether a drop of the Dosing valve was discharged.
• a modulation signal is to be understood as a signal corresponding to the modulation of the carrier signal by the drop, which signal can again be "separated” from the carrier signal by demodulation.
• Certain signal parameter values of the modulated measurement signal or of the modulation signal correspond to specific properties or dimensions. Solutions of a drop to be detected.
• the relationship between the aforementioned signal parameters and the properties or dimensions of a drop to be detected need not be immediately known for the detection. It is sufficient if, in advance, for example in a training method with the aid of "pattern drops" with defined dimensions, it has been determined which signal parameter values of the modulated measurement signal or of the modulation signal for a drop with the desired properties or dimensions (used in the training method) "Pattern drop”), ie, when a drop is detected as detected.
• a delivery of a drop in a defined time window is checked, which is synchronized with a drop delivery control of the metering valve.
• a time window in which a drop is detected or after a drop is at all "sought" or optionally even a carrier signal is delivered, synchronized with a drop delivery of the metering valve so that the intended drop delivery is within the time window.
• the drop detection device comprises a demodulation unit, which is set up to perform an amplitude demodulation of the measurement signal.
• a quadrature demodulation of the measurement signal is performed in order to determine an in-phase component and a quadrature component.
• the demodulation unit can be set up accordingly.
• the magnitude of the amplitude and / or the phase of a modulation signal based on the modulated measurement signal can be determined.
• the amplitude and phase of the modulation signal can be obtained by polar coordinate transformation of the in-phase component and the quadrature component.
• the evaluation unit of the drop detection device can preferably have a modulation value determination unit which is set up for this purpose.
• the latter in particular the modulation value determination unit, is set up to provide amplitude derivative values, including the time derivative of the magnitude of the amplitude, and / or phase deviation.
• Derivative values comprising the time derivative of the phase of the modulation signal to determine.
• the drop detection device in particular the modulation value determination unit, is set up in a predetermined fixed time interval of the time window for a predetermined number of the amplitude derivative values to amplitude comparison values and / or in a predetermined second time interval of the time window a predetermined number to combine the phase derivative values into phase comparison values.
• the combination of the amplitude derivative values and the phase derivative values may comprise a summation or addition of a plurality of amplitude derivative values to amplitude comparison values and a summation or addition of a plurality of phase derivative values to phase comparison values.
• the two time intervals are determined for the combination of the amplitude derivative values and the combination of the phase derivative values during the training phase or in the abovementioned training method.
• values are obtained constantly without time limitation.
• the time intervals are set so that a defined number of maximum values for the amplitude derivative values and the phase derivative values can be obtained at these time intervals.
• the time intervals for the amplitude derivative values and the phase derivative values are preferably set independently of each other. That is, their time and their start time are independent of each other.
• a time interval may be such that it comprises 50 measured values should the defined number of maximum values, for example 10, be within such a large range.
• the evaluation device of the drop detection device preferably comprises a detection filter unit, which is set up on the basis of the amplitude comparison values and / or the phase comparison values to determine whether the modulation signal indicates a drop.
• the detection filter unit of the droplet detection device can be configured to detect a deviation of a, for. B. from the modulation value determination unit, determined amplitude comparison value of an amplitude reference value to determine and / or a deviation of, for. B. determined by the modulation value ascertainment unit, determined phase comparison value of a phase reference value.
• An amplitude reference value may be formed, for example, from a plurality of amplitude comparison values of previously detected modulation signals.
• a phase reference value may be formed from a plurality of phase comparison values of previously detected modulation signals. In the formation of the reference values, care should be taken that only reference values which are assigned as correctly detected drops are included in the determination of the reference values.
• the drop detection device may comprise a reference value memory device, in which an amplitude reference value, which is formed from a plurality of amplitude comparison values of previously detected modulation signals, and / or a phase reference value, which is selected from a plurality of Phase comparison values of previously detected modulation signals is formed as variable reference values are stored.
• a reference value memory device in which an amplitude reference value, which is formed from a plurality of amplitude comparison values of previously detected modulation signals, and / or a phase reference value, which is selected from a plurality of Phase comparison values of previously detected modulation signals is formed as variable reference values are stored.
• the drop detection device in particular the detection filter unit, can be set up to determine whether the determined deviation of the amplitude comparison value from the amplitude reference value and / or the determined deviation of the phase comparison value from the phase - Reference value does not exceed a maximum value.
• the reference values form a kind of desired value, which was determined, for example, from empirical values.
• the reference values are continuously recovered during the normal detection process. They represent a kind of setpoint in connection with the permissible relative deviations determined from a filter training phase.
• the permitted relative deviations widths represent empirical variables, since they are determined during filter training. If the determined comparison values are too far away from the desired value, it is concluded that either no drop or at least no regular drop was detected.
• the detection filter unit can be set up accordingly.
• a fixed reference value interval for the amplitude and phase reference values can be stored in a reference value memory device.
• Such a fixed reference value interval can be determined, for example, in a training phase in which a possible fluctuation range of a reference value is also measured.
• a determination result can be classified as at least uncertain or even discarded. Such a situation can occur when the dimensions of the drops dispensed by a metering valve change slowly but steadily. If a reference value is now formed on the basis of such modified modulation values or comparison values, then in the unfavorable case, a reference value may also correspond to an incorrect drop which deviates too much from a previously determined nominal drop. In order to avoid such an error, a fixed interval is preferably set for the reference values, from which they must not deviate.
• a message to the user of the drop detection device can be output that the system is no longer calibrated correctly.
• the user can then take countermeasures. For example, the user can check the metering valve for correct function and eliminate any malfunctions.
• correct reference values can be determined.
• the reference values are determined in a kind of preliminary phase after the restart and constantly updated during the measuring process by averaging current measured values with previous reference values.
• FIG. 1 shows a schematic representation of a drop detection device according to an embodiment of the invention
• FIG. 2 shows a cross-sectional view of a drop detection device according to the invention as well as several variants with different active optical waveguide heights
• FIG. 3 shows a detailed illustration of a drop detection device according to an exemplary embodiment of the invention
• FIG. 4 shows a detailed representation of a mixer unit of a demodulation unit of a drop detection device according to an exemplary embodiment of the invention
• FIG. 5 shows a schematic representation of an external view of a control unit of a drop detection device according to an exemplary embodiment of the invention
• FIG. 6 is a flowchart illustrating a method for detecting a drop.
• FIG. 7 shows a flow chart with which the functional principle of the modulation value determination unit shown in FIG. 3 is illustrated in detail
• FIG. 8 shows a flow chart with which the functional principle of the detection filter unit shown in FIG. 3 is illustrated in detail.
• FIG. 1 shows a drop detection device 11 according to an exemplary embodiment of the invention.
• the drop detection device 1 1 comprises a light signal generation device 70, an optical waveguide arrangement L and a light evaluation device 80.
• the light signal generation device 70 comprises a signal generation unit 20 which generates a pulsed electrical carrier signal TS.
• the electrical carrier signal TS is transmitted to a light emission unit 31, for example a light-emitting diode, which transmits the electrical signal TS in a NEN pulsed with the carrier signal TS pulsed light beam LS.
• the pulsed light LS generated by the light emission unit 31 is transmitted to the optical fiber array L.
• a first optical waveguide element L1 of the optical waveguide arrangement L is connected to the light emission unit 31 in such a way that the light beam LS emitted by the light emission unit 31 is coupled directly into the first optical waveguide element L1 of the optical waveguide arrangement L.
• the pulsed light beam LS is fed through an emission window 14 to a gap ZR, in which a trajectory T of a droplet TR emitted by a dosing valve DV (with a nozzle adjusting nut DEM) runs.
• the light of the light beam LS is modulated by the droplet TR in such a way that it subsequently comprises information corresponding to a modulated light signal MS.
• the light beam LS comprising the modulated light signal MS is coupled via a detection window 15 into a second optical waveguide element L2.
• the light evaluation device 80 comprises a light sensor 32 and a signal evaluation device 50.
• the drop detection device 1 since the drop detection device 1 1, in particular due to the use of the pulsed light beam, is very insensitive to scattered light and other disturbances, but is highly sensitive to the useful signal, it is advantageously not necessary at the emission window 14 of the first optical waveguide element L1 or the detection window 15 of the second Optical waveguide element L2 additional optical elements, such. As lens systems or the like to use.
• the exit or entry sides of the optical waveguides must be as far as possible perpendicular to the longitudinal axis of the optical waveguide.
• the light sensor 32 and the light emission unit 31 are located outside the working area occupied by the metering valve DV, this sensor 32 and emitter 31 can be dimensioned independently of the narrow space prevailing in the area of the nozzle adjusting nut DEM of the metering valve DV.
• the emitter 31 serves as a signal converter, which converts the unmodulated electrical carrier signal TS into an unmodulated light signal LS.
• the light sensor 32 serves as a signal converter, which converts the modulated light signal MS into a modulated electrical measurement signal EMS. The subsequent processing of the modulated electrical measurement signal EMS is described in more detail in connection with FIGS. 3, 6 and 7.
• FIG. 2 shows in the upper partial drawing a cross-section of a drop detection device according to an exemplary embodiment of the invention. Furthermore, in the lower part of the drawing in Figure 2, several variants of the arrangement of the optical waveguides L1, L2 illustrated with different active optical fiber heights h a .
• the arrangement of the optical fibers L1, L2 is determined by means of spacers DS, which are mounted between an optical fiber mount LH and the metering valve DV.
• the active height h a beyond the nozzle setting nut DEM of the metering valve DV is about half the optical waveguide diameter, which corresponds to an effective height h a of 500 ⁇ m for an optical waveguide diameter of 1 mm.
• the height to be understood is the height of the section of the optical waveguides L1, L2 which is open towards the intermediate space in which the trajectory T of the drop runs. That is, the portion means the part of the cross section of the optical fibers L1, L2, which is not hidden by the nozzle adjusting nut DEM of the metering valve DV.
• this height h a can be matched to the particular conditions which are determined by the respective metering process.
• Half the optical waveguide area is used in the middle lower partial drawing, ie the active height h a corresponds to half the diameter of the optical waveguides L1, L2.
• the active width b a of the optical waveguide corresponds to the diameter of the optical waveguides L1, L2.
• Such an arrangement may be advantageous, for example, in the case of very small drops, since in this variant there is a more favorable ratio between the active area and the area shadowed by the drop. This results in a stronger signal amplitude of the modulation signal, which contributes to an improved signal-to-noise ratio.
• FIG. 3 shows a drop detection device 11a in accordance with a particularly preferred embodiment of the invention.
• the droplet detection device 11a also includes the units shown in FIG. 1, such as a light signal generating device 70, an optical waveguide device L and a light evaluation device 80, which are marked with dashed lines in FIG.
• the light signal generating device 70 and the light evaluation device 80 are shown in detail in FIG.
• the light signal generating device 70 includes a signal generating unit 20, which is shown in dashed lines in FIG.
• the signal generation unit 20 comprises a transmission signal generation unit 21 which generates a transmission signal PWM_5 having a defined, predefinable pulse frequency, for example as a pulsed square-wave signal.
• the generated transmission signal PWM_5 is transmitted to a power amplifier 24, which amplifies the transmission signal PWM_5 to a carrier signal TS.
• the signal generation unit 20 additionally comprises a signal generation unit 23, which is set up to transmit phase-shifted pulsed control signals PWM_1,..., PWM_4 with respect to the carrier signal to a mixer unit 43 of a demodulation unit 40.
• the signal generation unit 23 is part of the signal generation unit 20, it is used to evaluate a detected modulated signal EMS and is therefore not considered as part of the light signal generation device 70, but as part of the light evaluation device 80.
• the signal generating unit 20 has a control signal output 22 for driving amplifier circuits 44, 45 of the light evaluation device 80, which are also not considered part of the light signal generating means 70, but as part of the light evaluation device 80, since the control signal generated by the control signal output 22 of the evaluation of modulated signal MS is used.
• the pulse frequency of the control signals PWM_1, ..., PWM_4 for the mixer 43 is always equal to the frequency of the transmission signal PWM_5.
• the phase shift between the control signals PWM_1, ..., PWM_4 and the transmission signal is variable.
• the pulse frequency is preferably 450 kHz + - 15 kHz.
• the determination of the frequency of the carrier signal serves to ensure that the received signal (the carrier signal and the sidebands produced by the amplitude modulation caused by the drop) can optimally pass through the bandpass filter.
• a sideband is then selected.
• the carrier frequency must, according to the sampling theorem, be higher than twice the frequency resulting from the droplet transit time through the modulation unit 30.
• the carrier signal TS generated by the transmission signal generation unit 21 is transmitted from the amplifier 24 to a light emission unit 31.
• the light emission unit 31 can, for example, be a light-emitting diode which lights up as a function of the carrier signal TS applied to the light-emitting diode. In other words, the carrier signal TS initially present as a pulsed electric current is converted into a pulsed light signal.
• the light emission unit 31 is connected to the optical fiber array L.
• the light emission unit 31 emits the pulsed light signal TS into a first optical waveguide L1 of the optical waveguide arrangement L, which feeds the pulsed light signal TS to a gap ZR, in which a trajectory of a droplet TR to be detected of a metering valve (see FIG. 1) runs.
• a second optical waveguide L2 is arranged.
• the optical waveguide L2 is connected to the light evaluation device 80, which is also marked in dashed lines in FIG.
• the light evaluation device 80 comprises a sensor unit 32, which detects - if drops are delivered - a light signal MS modulated by the drops TR.
• the sensor unit 32 comprises, for example, a photodetector which receives the modulated light signal MS and converts it again into an electrical modulated signal EMS which can be transported by an electrical line.
• the electrical modulated signal EMS is subsequently transmitted to an evaluation unit 50 (likewise marked by dashed lines in FIG. 3), which is part of the light evaluation device 80 and also has a demodulation unit 40.
• the demodulation Onsaku 40 includes an amplifier unit 41, which amplifies the modulated electrical signal EMS.
• the amplifier unit 41 is driven by the signal generating unit 20 via a control signal output 22 and serves on the one hand for preamplification of the modulated signal EMS detected by the photodetector 32 and on the other hand as a transimpedance amplifier.
• the photodetector 32 is biased in the reverse direction and operated in a quasi short circuit.
• the transimpedance amplifier converts the current signal into a voltage signal.
• the amplification factor of this conversion is adjustable. This achieves a maximum, voltage-dependent, voltage-controlled signal modulation.
• the demodulation unit 40 comprises a filter unit 42.
• the filter unit 42 may, for example, comprise a bandpass filter which passes only the two sidebands and the carrier frequency of the modulated signal EMS.
• the filter unit 42 also removes any interfering signals caused by external light radiation with frequencies far away from the pulse frequency of the carrier signal TS.
• the filter unit 42 preferably a steep-edge bandpass filter, also removes harmonics generated by the pulse width modulation.
• the thus filtered modulated measurement signal EMS is then forwarded to a mixer 43, which transmits the modulated and filtered measurement signal EMS with pulsed control signals PWM_1,..., PWM_4, which are phase-shifted with respect to the carrier signal and subsequently also PWM.
• Called signals mixes and transmits an in-phase signal or an in-phase component I to an in-phase signal amplifier 44 and transmits a quadrature signal or a quadrature component Q to a quadrature signal amplifier 45.
• the in-phase signal amplifier 44 and the quadrature signal amplifier 45 are driven by a control signal output 22 of the signal generation unit 20.
• the amplifiers 41, 44, 45 are controlled separately. They are set via a variable resistor (rheostat) programmable via a data bus (eg I2C-BUS). Each rheostat (and therefore amplifier) is individually adjusted. The setting of the amplifier 41 is thereby completely independent of the value of the amplifiers 44 and 45.
• the amplifiers 44 and 45 however, always have the same Value so as not to change the relation between the I and the Q signal. Nevertheless, these two are controlled separately.
• the mode of operation of the mixer unit 43 is shown in detail in FIG. 4 and will be explained in more detail later.
• the in-phase component I and the quadrature component Q form the modulation signal MOD.
• the two components I, Q are transmitted within the evaluation unit 50 to the subunits of the evaluation unit 50, which are part of a control unit 60 in the embodiment shown in FIG.
• the control unit 60 has corresponding inputs 53, 54 for the signal components I, Q.
• the inputs 53, 54 are followed by AD converters (not shown), which convert the analog signal components I, Q into digital signals.
• the amplifiers 44, 45 of the demodulation unit 40 are adaptable in their amplification factor and serve to raise the signal components I, Q of the modulation signal MOD generated by the mixer unit 43 to an optimum voltage level for the AD converters. This ensures maximum utilization of the converter resolution. In order not to bring the AD converters through the DC components present in the components I, Q to their voltage limit given by a reference voltage, only the alternating components caused by a drop are amplified.
• the evaluation unit 50 comprises a modulation value determination unit 51 and a detection filter unit 52.
• these subunits of the evaluation unit 50 are part of the control unit 60.
• the modulation value determination unit 51 the digitized signal components I, Q are processed mathematically and in amplitude and phase information transformed, for example by means of a polar coordinate transformation.
• the detection filter unit 52 can be formed, for example, as a parameterizable software filter with which it is determined on the basis of the acquired information whether a drop has passed the gap ZR between the first optical waveguide L1 and the second optical waveguide L2. Before the system 1 1 a begins its regular operation, it must be set by two separately running initialization operations.
• all hardware modules must be set to an optimum operating point for detection. These settings include the determination of the operating point of the light sensor 32 by the carrier signal duty cycle, the frequency Tuning of the carrier signal TS to the filter characteristic of the bandpass filter 42, the adjustment of the phase position of the mixer signals PWM_1 ... PWM_4 in relation to the carrier signal for accurate sideband selection, the determination of the optimum gain of the transimpedance amplifier 41 and the signal matching of the I and Q signals for the AD converter of the inputs 53, 54 through the ADC preamplifiers 44, 45.
• all parameters of the detection filter unit 52 based on the expected target drops TR, must be adjusted.
• Both hardware and filter settings can be set manually or through automatic training processes. These settings are needed for the modulation value extraction as well as the signal evaluation regarding the recognition of a drop TR.
• the quadrature demodulator 43 comprises a transformer 431, a switch unit 432 with switches 432a, 432b, 432c, 432d connected in parallel, an integrator unit 433 with the parallel-connected switches 432a, 432b, 432c, 432d respectively downstream integrators 433a, 433b, 433c, 433d and a first and a second differential amplifier 434a, 434b, which are each electrically connected to two integrators.
• the quadrature demodulator 43 acts as a single-sideband mixer and sets the modulated electrical measurement signal EMS back into the baseband.
• the sideband used for the demodulation is determined by an appropriate choice of the phase position of the modulated measuring signal EMS with respect to four control signals PWM_1, PWM_4, which control the switches 432a, 432b, 432c, 432d of the mixer 43, via the differential amplifiers 434a, 434b, which control the Integrators 433a, 433b, 433c, 433d are selected.
• the output signals of the differential amplifiers 434a, 434b are InPhase signals I and quadrature signals Q, from which a modulation signal MOD can be derived, which is correlated with the disturbance of the carrier signal TS by a drop TR of a metering valve.
• the mixer unit 43 functions as follows: A measurement signal EMS is transmitted from the transmitter 431 to the input of the mixer unit 43.
• the transformer 431 serves to match the power between different components as well as the signal balancing and removal of existing DC components.
• the Mixer 43 a resistor R, which is connected in series to the output of the transformer and together with the integrators 433a, 433b, 433c, 433d forms a filter.
• the switches 432a, 432b, 432c, 432d are acted upon by the signal generation unit 23 with control signals PWM_1, PWM_4, which in each case for a quarter of the period T PW M or a quarter wave of the carrier signal TS one of the switches 432a, 432b, 432c, 432d through.
• the control signals PWM_1, PWM_4 are thus synchronized with the carrier signal TS. If one of the switches 432a, 432b, 432c, 432d is closed, the measuring signal EMS for the time interval in which the respective switch 432a, 432b, 432c, 432d is closed, from the associated integrator 433a, 433b, 433c, 433d to a Average value integrated.
• the integrators 433a, 433b, 433c, 433d may, for example, comprise capacitors connected in parallel and produce average values of the sections of the modulated electrical measurement signal EMS assigned to the individual quarter-waves of the carrier signal TS.
• An average value integrated in the first quarter wave is applied to the positive input of the first differentiator 434a marked "+”
• an average value integrated in the third quarter wave is applied to the negative input of the first differentiator 434a marked "-”.
• An integrated average value in the second quarter wave lies at the positive input of the second differentiator 434b and an integrated average value in the fourth quarter wave is applied to the negative input of the second differentiator 434b.
• An in-phase signal I in the baseband is generated at the output of the first differentiator 434a, and a quadrature signal Q in the baseband is generated at the output of the second differentiator. Details on the operation of such mixing units are described in US 6,230,000 B1. 5 shows an external view (of a housing) of a control device 60 with which the activation of individual units of a drop detection device 11, 11a, the evaluation of measurement signals, the monitoring of the functionality of individual units and the setting and tuning of individual system parameters are performed can.
• This housing houses all the electronics. This applies in principle to the overall drop detection system, including the optoelectronic signal converter (receiver photodiode 32, and transmit LED 31).
• the data bus connection DB is intended in the future to serve inter alia for communication with the valve control unit this data bus connection DB the current status of the drop detection or statistics on the past dosing processes (number of detected errors and when they have occurred) are transmitted to them.
• Another possible application for this data bus connection DB is that the drop detection could request the valve control unit via this bus to intentionally cause false doses in order to check the correct function of the drop detection. Drop detection would then have to detect these intentional false doses safely.
• Part of the control device 60 is also a communication interface I / O, with which trigger signals are received by the valve control unit 70 and output via the information regarding the system status of the drop detection device and the dosing status.
• control device 60 comprises a serial interface Sl, which serves as a connection to a superordinate process control computer 80.
• the process control computer 80 can control the drop detection via the serial interface S1 and / or query status reports on the past dosings.
• the control device 60 has an input RX, which serves as a connection of the receiving optical waveguide L2 to the photoelement. At the input RX, therefore, the reception optical fiber L2 is connected.
• An output TX serves as a connection of the transmitting optical waveguide L1 to the transmitting light-emitting diode 31. At the output TX so the transmitting optical fiber L1 is connected.
• Another input U s is used to supply voltage to the control device 60.
• An additional input PGM can be used as a programming socket for firmware transmission.
• the control device 60 comprises a display 55 and a plurality of indicator lights 56, ..., 59.
• a first indicator light 56 is used to display various system errors.
• a second indicator light 57 is used to display a system status or activity of the system. This status may, for example, concern the fact that an optical fiber L1, L2 is not properly connected, damaged, too long or dirty.
• a third indicator light 58 may include a message that a drop of correct dosage has been detected.
• a fourth warning light 59 may include a message that an error has occurred in the metering, that, for example, no drop was detected or the detected drop has too great a deviation from a target drop.
• the control device 60 also comprises two pressure switches S1, S2 for tuning individual units of a droplet detection device.
• a first training mode a "hardware training mode”
• a “hardware training mode” is switched on, in which, for example, the setting of a pulse width of the carrier signal TS is optimal Brightness of the light emitting unit 31 with respect to the light reaching the light sensor unit, a light beam formed on the basis of the carrier signal TS is achieved, the setting of a frequency of the pulsed carrier signal TS, so that the two sidebands of the modulated signal EMS can pass through the sensor device downstream filter unit 42 , adjusting the phase position of the carrier signal TS via the signal PWM_5 in relation to the control signals PWM_1,..., PWM_4, with which the mixer unit 43 associated with the demodulation unit is driven, and adjusting the voltage adjustment amplifier units 44 and 45 and the Amplifier unit 41, wel che acts as a transimpedance amplifier takes place.
• This hardware training mode is z. B. carried out at a first commissioning of the droplet detection means or when hardware
• a second training mode By pressing the other switch S2 for a defined period of time (also for example 2 s), a second training mode, a "software training mode", is switched on, in which, for example, the detection filter unit 52 and the modulation value determination unit 51 of the evaluation unit 50 In this case, the relative permissible fluctuation ranges of the comparison values in relation to the reference values, the acquisition time windows of the values relevant for the detection filter unit 52 and the absolute value ranges of the reference values are determined a new test series is pending, ie another type of drop is to be detected.
• FIG. 6 shows a flowchart with which a method 500 for detecting a drop of a metering valve DV is illustrated.
• a pulsed carrier signal TS is generated with a defined pulse frequency or carrier frequency and a defined duty cycle.
• a modulated measurement signal MS is generated by a physical interaction of the carrier signal TS with a droplet TR to be detected, which was delivered by the metering valve DV.
• the carrier signal TS is converted by a light emission unit into a light signal LS.
• the light beam LS pulsed with a carrier frequency is coupled into a first optical waveguide L1.
• the pulsed light beam LS is emitted by the first optical fiber L1 at step 6.11c so as to pass a gap ZR between the first optical fiber L1 and a second optical fiber L2, a trajectory of the drop TR passing through the gap ZR between the first optical fiber L1 first optical waveguide L1 and the second optical waveguide L2 extends, crosses and then - possibly a modulated light signal MS comprising - is coupled into the second optical waveguide L2.
• the light beam LS possibly comprising a modulated light signal MS is converted by a light conversion unit, for example a light sensor, into a possibly modulated electrical measurement signal EMS.
• a modulation signal MOD is determined on the basis of the possibly modulated electrical measurement signal EMS.
• the modulation signal MOD corresponds to the information which is impressed on the light beam LS in the event of a collision of a droplet TR with the light beam LS.
• step 6.1V it is determined on the basis of the modulation signal MOD whether a drop TR has been delivered by the metering valve DV.
• FIG. 7 shows the functional principle 700 of the modulation value determination unit 51 of an evaluation unit 50 shown in FIG. 3 in detail.
• the modulation value determining unit 51 detects in-phase and quadrature components I, Q from the AD converters of the evaluation unit 50 connected downstream of the inputs 53, 54 of the control unit 60.
• the sampling of the in-phase Signal I and the quadrature signal Q takes place continuously.
• the two values I, Q are preferably obtained absolutely at the same time.
• the values I, Q pass through a median filter prior to their further processing in order to remove extreme values caused by interference radiation, ADC conversion errors, etc.
• step 7.II the signal components I, Q are converted by means of a polar coordinate transformation into a signal MOD (A, ⁇ ), which comprises information relating to the amplitude A and the phase ⁇ of the modulation signal MOD.
• a signal MOD A, ⁇
• the amplitude A is as follows:
• I and Q correspond to the amplitudes of the in-phase and quadrature components I, Q of the demodulated signal or of the modulation signal MOD.
• the amplitude A and the phase ⁇ are like the signal components I and Q time-dependent quantities. Due to the high sampling rate and the associated fast value extraction, the calculations according to Equations 1 and 2 are calculated using look-up tables with linear inter-value interpolation.
• step 7. II a time derivative of the amplitude A and the phase ⁇ of the modulation signal MOD (A, ⁇ ) takes place.
• step 7.1V derivative values dA / dt, dcp / dt are considered in a predetermined time interval I T and a predetermined number of maximum values max (dA / dt), max (dcp / dt) of the derivative values dA dt, dcp / dt, For example, the largest 10 values are selected in the predetermined time interval I T.
• the predetermined time interval I T may be set in advance at the initialization of the drop detection means or during the detection filter training.
• modulation values A M , ⁇ for the amplitude A and the phase ⁇ are formed as a sum over the predetermined number of maximum values.
• FIG. 8 illustrates the functional principle 800 of the detection filter unit 52 of the evaluation unit 50 shown in FIG. 3 in detail.
• modulation values A M , ⁇ for the amplitude A and the phase cp which are also known as comparison values, are determined by the modulation value determination unit 51 according to the method illustrated in FIG. 7.
• these comparison values A M , cp M are stored in an electronic memory.
• the stored comparison values are used for the reference value calculation.
• Reference values RW A , RW ⁇ p for the amplitude A and the phase ⁇ are determined.
• These reference values RW A , RW ⁇ p can be, for example, mean values from older amplitude and phase values, ie comparison values which were obtained, for example, in an earlier detection of drops.
• step 8. IV a deviation AW of the modulation values A M , ⁇ for the amplitude A and the phase ⁇ of the modulation value determination unit 51 determined by the modulation value determination unit 51 is determined the reference values RW A , RW ⁇ p. Subsequently, in step 8.V, a comparison is made between the deviation AW determined in each case and a maximum permitted relative deviation upward AW_Oben, or downward AW_Unten. If the deviation is too large, which is marked with "j" in FIG.
• step 8.VI a faulty drop has been determined
• the measure of the permitted deviation AW_Oben or AWJJnten is based on one or more desired values
• a creeping error for example the phenomenon that the size of the droplets TR to be detected changes during a frequently repeated delivery of droplets TR from a metering valve DV
• the value of the drops is also slowly changing, it is also possible to monitor the reference values RW A , RW ⁇ p, that is to say the average values over the modulation values A M , (M) of past drops the reference values RW A , RW ⁇ p for amplitude A and phase ⁇ are within a predetermined absolute value interval ARI, PRI If the reference values RW A , RW ⁇ p do not are in the predetermined value interval ARI, PRI, which is marked in Figure 8 with "n", so in step 8.VII I issued a message that now there is a sequence of erroneous drops.
• the devices described in detail above are only exemplary embodiments which can be modified by the person skilled in many different ways without departing from the scope of the invention.
• the use of the indefinite article “on” or “one” does not exclude that the characteristics in question may also be present multiple times.
• the term “unit” should also include components which consist of a plurality of subunits, which may also be spatially separate, and the term “unit” may also mean a logical unit of thought, so that one and the same hardware component has several of these logical units. can take. This applies, for example, in particular to the demodulation unit 40 and possibly also to the signal generation unit 20 and the evaluation unit 50.

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• 2015
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