Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
  • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
  • G01F23/246—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid thermal devices
  • G01F23/247—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid thermal devices for discrete levels
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water

Definitions

• thermocouples as sensors has the advantage of providing an electrical signal that can be conveniently processed in an evaluation device or via an on-board computer to determine the liquid level.
• a group of such thermocouples is attached to the container at different heights, and at a distance from one another which corresponds to the fineness of the liquid levels to be determined in the container.
• the thermal voltage now comes about by heating one of the two connection points of the thermocouple used to construct the thermocouple.
• different thermal voltages occur because heat is dissipated inside the liquid. The thermal voltages are evaluated and serve to clearly determine the given liquid level in the container.
• thermocouples of a liquid level measuring system were created in this way.
• a heating conductor which in each case heated the one connection point of these thermocouples and thereby generated a thermal voltage between the two connection points of the metals.
• the invention has for its object to develop a reliable, easy-to-use device of the type specified in the preamble of claim 1, which is inexpensive and insensitive to fuel influences and can be easily manufactured. This is achieved according to the invention by the measures specified in the characterizing part of claim 1, which have the following special meaning:
• thermocouple is unnecessary, because the printing of the metal conductive adhesive as lines on the two ends of the webs surprisingly results in a thermocouple which can be used as a sensor.
• the heating conductor is expediently also produced on the back of the carrier by printing with a metal conductive adhesive.
• Material with a thickness of a few micrometers is sufficient for the vapor deposition of the webs or sensors. Minimal quantities of material are also sufficient for printing the connection points and conductor tracks. The inexpensive manufacture of the device is thereby achieved.
• the invention has also recognized that the use of semiconductor materials in conjunction with metal conductive adhesives produces surprisingly high thermal voltages at the connection points.
• Semiconductor materials such as, for example, are suitable for the webs or sensors.
• a silver-containing substance is expediently used as the metal conductive adhesive.
• the heating conductor should also be printed on the back of the carrier, as proposed in claim 2.
• the simplest setup usually requires a separate heating conductor for each sensor set, especially if there is a structure according to claim 14.
• a heating conductor can serve to heat several sets of the sensors. For reasons of energy saving, it is very important that the level indicator in the case of a motor vehicle is only ready for operation when the ignition is switched on. Furthermore, the power of the heating conductor should be kept constant in order to avoid measurement value deviations.
• cover films according to claim 19 In particular when using the device in motor vehicle tanks, it has proven useful to process cover films according to claim 19. With epoxy resin, the cover foils can be laminated on in a fuel-tight and bubble-free manner. When using fuels with alcohol addition, such as methanol, a fuel-tight envelope of the thermocouple carrier is very important. Such fuels generally have a high conductance and electrical shunts could then occur, which could lead to falsified measurements. A metal cladding according to claim 21 of the cover foils prevents interference signals from being measured and leading to errors. To avoid short circuits, however, the metal lamination must be left out in the area of the contact elements. In order to derive the external and interference voltages occurring there, a connection of the metal layer to the system mass should be ensured.
• the film material should, according to claim 25, consist of temperature and fuel-resistant material.
• the connecting line leading from the module on the carrier side to the display device is therefore of a particularly simple construction.
• the supply voltage of the IC module must be stabilized.
• there is a voltage constant holder in the coupling as will be described in more detail. In vehicles with their own on-board computer, this can also take over the function of the IC module, which eliminates the evaluation device. In this case, the mentioned series connection of all sensors is very useful.
• the display system works in the form of a voltage coding, ie the measured value voltage changes analogously to the level in the tank.
• FIG. 13 shows an optimized embodiment of a series connection of the sensors with shortened conduction paths and only one common heating conductor for the two comb-shaped rows of sensors connected in series.
• the device 10 can be used to determine the respective filling content of a container 11, for which purpose the fuel tank of a vehicle is used in the present case.
• the device comprises a measuring device, designated summatively by 12 in FIG. 1, in the inner container 19, which forwards the signals via a connecting line 18 to an evaluation device 13, where they are processed and, via the connecting lines 18 ', a device connected thereto Control display device 14. After switching on the ignition, the device is connected to the vehicle-side power supply, as is illustrated in the area of the evaluation device 13 in FIG. 1.
• the measuring device 12 is immersed at a defined height in the liquid 15 received by the container 11, the level of which is indicated by the arrow 16 to be determined by the device 10. As will be explained in more detail, this is done by electronically measuring the given altitude of the liquid level 17 in the container 11.
• the measuring device 12 comprises an immersion tube 22 which, in the region of the fill level 16 to be measured, is arranged fixedly in the interior 19 of FIG. 1.
• the actual measuring element 20 Inside 25 of immersion tube 22 is the actual measuring element 20, to be described in more detail, which is equipped with a group of special sensors 30.
• the IC module 21 At the top At the end of the measuring element 20 there can also be an IC module 21 with integrated circuits, which is adapted to the specific application of the device 10 and which already partially or completely evaluates the signals coming from the sensors 30 before they are then forwarded via the connecting line 18.
• the vehicle movement When used in a vehicle, the vehicle movement must be taken into account, which would lead to an uncontrolled wave movement in the given liquid level 17.
• the front opening of the immersion tube 22 already leads to an equalization of the liquid level in the tube interior 25, it is advisable to provide a cover with a narrowed opening 23 on the underside.
• the indicated flow 24 of the liquid can flow through this constriction 23 only slowly, which is why sudden, brief changes in height of the liquid level 17 outside the immersion tube 22 cannot have a corresponding change in height in the tube interior 25.
• the liquid level 17 remains in the area of the measuring element 20 essentially at the given height and responds only to actual changes in the fill level.
• thermocouples 30 are used as the sensor, which are positioned on a carrier 27 which is only shown in more detail in the following figures and which has been omitted in FIG.
• the thermocouples 30 are arranged at a defined height distance 31, 31 'from one another, which is adapted to the desired measuring accuracy of the aforementioned fill level 16.
• the height spacings 31, 31 'can, as indicated in FIG. 5, be designed differently from one another in order to then also detect uniform measuring steps corresponding to a given volume unit in those containers 11 which have a height-uneven shape. Such a different increase in the fill level due to the complicated container shape could also be fully or at least partially detected by the evaluation device 13 or the IC module 21 integrated on the measuring element 20.
• thermocouples consist of two different materials. Metals and semiconductors or their compounds are used as the first material component, such as silicon, germanium, gallium arsenide, Tin oxide (SnO), selenium or tellurium. This is done by vapor deposition on a thin film 41, which is explained in more detail in connection with FIGS. 8 to 10. One could possibly also use a screen printing process in which the above materials are used in paste form. Another application possibility is by spraying or by a CVD process. This material creates a family of webs 34 one above the other at a distance 31, 31 '.
• the second material component of the thermocouple 30 to be formed is produced by printing lines in the form of a metal conductive adhesive, preferably silver conductive adhesive, on the two Web ends 32, 33, as will be explained in more detail.
• connection line 35 The printed metal conductive adhesives also produce the lines emanating from the one connection point 32, which, as shown in FIG. 5, merge into a common line 35 for all sensors 30. This line leads to the end 37 of the conductor and will hereinafter be referred to as "connecting line 35".
• a thermal voltage then arises between these two connection points 32, 33 when they are at a different temperature from one another.
• the evaluating device 13 and the described IC module 21 successively separate the voltages between the Common conductor end 37 of the connecting line 35 on the one hand and the individual conductor ends 38 of the various measuring lines 36 on the other hand measured. It follows that between the line end 38 'of the last measuring line 36 compared to the line end 37 there is a higher thermal voltage than between the measuring line ends 38 and the common line end 37 of all the other sensors 30 below. From this, the evaluation device detects that the liquid level 17 must lie between the last and penultimate sensor 30, which is then made known accordingly via the electronics in the display device 14. These measurements can be made in 4 to 5 measuring cycles per minute. For the heating conductor, an adjustment period of approx. 5 seconds per measuring cycle is sufficient for energy saving and low heat development.
• FIG. 6 A second possibility for switching the sensors 30 is shown in FIG. 6, where the sensors 30 are connected in series, that is to say in series.
• the same reference numerals as in FIG. 5 are used to designate corresponding components, which is why the previous description applies to this extent. It is only sufficient to deal with the differences.
• the cold and warm connection points 32, 33 of adjacent sensors 30 are continuously connected to one another by connection lines 79.
• a summative but reciprocal total voltage is thus generated analogously to the above-described liquid level 16 in the container 11.
• the advantage of this circuit lies in the reduction in the number of measuring lines 36. In the optimal case, a single measuring line 36 and a single connecting line 35 are sufficient to transmit the total voltage to the evaluation device 13 or to an on-board computer.
• the display system works in the form of a voltage coding.
• the measuring element 20 comprising the sensors is produced in the following way.
• a layer 40 of, for example, Te from 0.5 to approximately 3.5 .mu.m thick is evaporated, on the underside of which there is a melt adhesive layer 39 which forms the further layer Processing simplified.
• a punching length 43 is now cut out of this flat structure 42 from FIG. 8, the interfaces of which are indicated in FIG. 8 by dash-dot lines and which, for example, has the outline of a "comb", consisting of a longitudinal comb 44 on which a coulter of comb teeth 34 come off, which fulfill the above-mentioned function of the webs.
• a carrier 27 already mentioned which consists of a sheet-shaped plastic, for which a flexible film should also be used.
• This preliminary product 27, 43 is, as shown in FIG. 10, subjected to the previously mentioned screen printing process, where a coating layer 45, 46, which consists of the metal conductive adhesive already mentioned, is applied to the two web ends 32, 33 of the evaporated metal layer 40 and which also produces the connecting and measuring lines 35, 36 already described, the course of which results in principle from the front view of the carrier of FIG. 3.
• a free field 49 is arranged in the upper region of the carrier 27, where the conductor ends 37, 38 described are located and are connected to the IC module 21 already mentioned in FIG. 2 via switching connections (not shown in more detail).
• the procedure according to FIG. 3 is such that the mentioned connecting line 35 runs longitudinally on the longitudinal comb 44 described in FIG. 9 and thereby connects all the base points of the sensors at which the connection points 32 of Fig. 5 arise. Among other things, this results in a reduction in the conductor track resistance.
• the already mentioned heating conductor 26 is also printed on the back of the carrier 29, which, as the back 29 of FIG. 4 shows in connection with the front 28 of FIG. 3, is in alignment with the free ends 32 mentioned individual webs 34 stands. In some cases, however, it is advisable to proceed in reverse.
• the return line 47 shown in FIG. 4 is likewise applied to the back of the carrier 29 by printing using the conductive metal which is expediently made of the same metal, but which has a substantially larger layer width 48 compared to the heating conductor 26. Although the same current flows through both lines 26, 47, only the heating conductor 26 heats up because of the much smaller width, while the return line 47 remains cold.
• a connection element 78 which continues the carrier 27, is located above the field 49 marked in FIGS. 3 and 4 for connecting the IC module 21.
• Lanes 52, 52 ′ run there, which serve as output lines for the signals processed in the IC module 21.
• a cover film 50, 51 is laminated on both the front 28 and the back 29 of the carrier 27, in a fuel-tight and bubble-free manner by using epoxy resin, which results from the fragment of the finished film package drawn in high magnification 20 can be seen in Fig. 7.
• the carrier 27 used and the cover foils 50, 51 are actually only about 30 ⁇ m thick.
• a metal lamination 59 of the cover foils 50, 51 is used to shield the resulting measuring element 20.
• the metal lamination 59 are connected to the system mass via contact elements 71 connected.
• the connection element 78 the construction of which will be described in more detail, however, the metal lamination 59 must be left out to avoid short-circuits, as indicated at 80 in FIG. 7.
• Metallic, clamp-like contact elements 53 are used for the easy electrical connection of the finished measuring element. They have two clamp ends 54, which are pierced and flanged by the foil package 20 in the region of its connecting element 78, the webs 52, 52 'of FIGS. 3 and 4. 7, the clamp ends 54 penetrate all layers and, on the one hand, ensure a mechanical connection and, on the other hand, also the electrical connection when penetrating the conductor track 52, 52 'assigned to them.
• the connector parts 55 indicated in FIGS. 3 and 4 are produced in one piece with the contact elements 53. The connector parts 55 project beyond the upper edge of the connecting element 78.
• the connector parts 55 are coupled into complementary sleeves, the components of the connecting line indicated in FIG. 1 18 are divided into the following sub-lines.
• connecting element 78 there are plug parts 73 for the heating line, furthermore one or more plug parts 74 for one or more measuring lines, then a plug part 75 for the voltage connection of the IC component, furthermore a plug part 76 for the control line of the IC component and finally the already mentioned connector part 71 for connecting the system ground.
• the measuring element is connected to its connecting element 78 through a mounting slot of a cover indicated in FIGS.
• the flexibility of the measuring element designed as a foil package 20 can be used to reduce the geometric dimensions. Folds and / or roll deformations of the foil package 20 are used for this purpose. In the rolled state, such a foil package 20 can be positioned in the dip tube 22 in the correct shape. In addition, such a rolled shape can also be used to build or support an immersion tube 22.
• the invention not only forms an extremely thin film package 20, but also the widths of such a package can be significantly reduced by these deformations, so that there is essentially an elongated structure, the sensors 30 of which have the defined height distance 31, 31 'of already described 5 and 6 remain arranged and extend over the entire fill level 16 to be monitored in the interior 19 of FIG. 1.
• thermocouples 30 are constructed due to the combination of materials described above, this can be doubled by a series connection of at least two sets of sensors 30, 30 'or increased by a multiple of several sets of sensors.
• 11 shows a possibility for this with the aid of a modified foil package 20 ', which is shown in cross-section in a large enlargement, but not to scale.
• the same reference numerals are used to designate corresponding components as in the previous exemplary embodiment, which is why the previous description applies to this extent. It is enough to only consider the differences.
• thermocouples 30, 30 ' This creates two sets of thermocouples 30, 30 ', which are in pairs in the same height in the foil package 20 'and are connected in series with one another
• This metal liner 59 is as shown in FIG has already been mentioned, connected to the system ground at 71.
• This metal layer 59 can have a thickness of 0.01 to 1.5 ⁇ m and, for example, of Al uminium or copper. It serves to shield the electrical lines inside this foil package 20 '.
• FIG. 12 shows an alternative embodiment of a foil package 20 "with a series connection of two sets of thermocouples 30, 30 ', the course of the lines and connections also produced here by printing with metal conductive adhesive being shown only by broken lines, which The two diecuts 43, 43 'are arranged in mirror image to one another on the common front side 28 of a carrier 27, ie the longitudinal bars 44, 44' are directed away from one another.
• Tines 34, 34 ' face each other and are located in a longitudinal zone 61, on which there is a common heating conductor 26 on the back of the carrier warming ends 33, 33 'arranged next to each other in an electrically insulated manner, but at the same time heated by the same heating conductor 26. In use, this has the advantage of minimal energy consumption and little heating of the liquid to be monitored. However, it is necessary to carry out the printing of the lines produced by metal conductive adhesive in several stages and to use an intermediate film 60 for the insulation of intersecting cable runs.
• both the support layers 45, 58 of which the support layer 45 is forwarded as a common connecting line 35, is applied both to the spar 44 of the one diecut 43 and to the spar 44 'of the other diecut 43' leads and acts in the sense of FIG. 5 during the measurement.
• the cold connection points 32, 32 ' are formed at these points. From the cold connection points 32' of the longitudinal spar 44 ', individual connection lines 58 lead to the warm connection points 33 of the adjacent punched section lings 43 and thus ensure the subsequent electrical series connection of one warm connection point 33 and the opposite cold connection point 32 '.
• Interruptions 63 which are produced after the diecut 43' is stuck to the carrier, for example by punching out, separate them Comb tines 34 'on the longitudinal comb 44'.
• an intermediate film 60 according to FIG. 12 is glued to the one die-cut part 43 'fastened to the carrier 27 in such a way that its film edge 62 is set back relative to the warm connection points 33' mentioned and leaves them free. Only then, in a further process step, are the individual support layers 46 of the metal conductive adhesive printed on the upward-facing front side of the intermediate film 60, which cover the warm connection points 33 ′ over the band edge 62 of the intermediate film 60 and there the required thermocouple Generate contact. These support layers 46 can then be continued in the sense of FIG. 5 through the respective measuring lines 36.
• FIG. 13 shows a particularly space-saving and cost-saving design of a measuring element 20 ′ ′′.
• sensors 30, 30 ' are connected in series, ie in series.
• a summative but reciprocal measuring voltage is generated, which changes analogously to the filling level 16 in the container 11.
• the sensors 30, 30 ' are produced by comb-shaped die-cuts 43, 43', which are arranged in mirror image to one another. This mirror image is, however, offset by half a comb pitch 70 from one another, so that the individual webs 34, 34 'can be nested.
• the warm connection points 33, 33 ' lie in a linear alignment and determine the longitudinal zone 61 for the arrangement of a heating conductor.
• the width of the longitudinal zone 61 can thereby be minimized. In any case, a single heating conductor is required, the advantages of which have already been explained in connection with FIG. 12.
• Interruptions 63 are punched in along the spars 44, 44 'on both sides of the diecuts 43, 43' glued on, as a result of which L-shaped sections are formed from the originally comb-shaped diecuts 43, 43 ', which separate the sensors 30, 30'. Due to this angular sensor geometry and the nested sensor arrangement, the warm connection points 33, 33 'lie directly opposite the cold connection points 32, 32', as a result of which extremely short connection lines 58 made of the metal conductive adhesive mentioned are sufficient. The use of an intermediate film is avoided by the crossover-free construction of the circuit. The number of work steps for producing this measuring element 20 '"is thus reduced.

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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Fluid Mechanics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

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• 1990
  • 1990-09-26 DE DE19904030401 patent/DE4030401A1/de active Granted
• 1991
  • 1991-03-09 JP JP50571291A patent/JPH05500571A/ja active Pending
  • 1991-03-09 WO PCT/EP1991/000452 patent/WO1991014926A1/de not_active Application Discontinuation
  • 1991-03-09 EP EP19910905960 patent/EP0472694A1/de not_active Withdrawn

Non-Patent Citations (1)

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