EP0840534A1 - Chauffage électrique et sa commande - Google Patents

Chauffage électrique et sa commande Download PDF

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Publication number
EP0840534A1
EP0840534A1 EP97118676A EP97118676A EP0840534A1 EP 0840534 A1 EP0840534 A1 EP 0840534A1 EP 97118676 A EP97118676 A EP 97118676A EP 97118676 A EP97118676 A EP 97118676A EP 0840534 A1 EP0840534 A1 EP 0840534A1
Authority
EP
European Patent Office
Prior art keywords
heating
carrier
unit
sensor
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97118676A
Other languages
German (de)
English (en)
Inventor
Ralf Diehlmann
Volker Block
Achim Bierbaum
Wilfried Schilling
Lutz Dr. Ose
Franz Dr. Bogdanski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EGO Elektro Geratebau GmbH
Original Assignee
EGO Elektro Geratebau GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EGO Elektro Geratebau GmbH filed Critical EGO Elektro Geratebau GmbH
Publication of EP0840534A1 publication Critical patent/EP0840534A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B1/00—Details of electric heating devices
    • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
    • H05B1/0202—Switches
    • H05B1/0208—Switches actuated by the expansion or evaporation of a gas or liquid
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B1/00—Details of electric heating devices
    • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/02—Details
    • H05B3/06—Heater elements structurally combined with coupling elements or holders
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/011—Heaters using laterally extending conductive material as connecting means
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/017—Manufacturing methods or apparatus for heaters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/021—Heaters specially adapted for heating liquids

Definitions

  • the invention relates to a heater which is particularly suitable for heating solids or flowable media, such as liquids, by direct heat conduction.
  • a heater which is particularly suitable for heating solids or flowable media, such as liquids, by direct heat conduction.
  • This can e.g. Solids of devices such as hot plates or water can be heated to temperatures below 200 ° C or 100 ° C.
  • control elements of a control unit are expediently provided, which work electronically. You can each have at least one sensor, measuring signal amplifier, differentiator, threshold switch, an actuator, a microprocessor, a power supply or the like. contain. In order not to be damaged, such elements can usually only be exposed to a temperature or permanent temperature of at most 200 ° C or 150 ° C. Therefore, they should be placed in an area protected from overheating. For example, electronic elements and the electrical conductor tracks connecting them can be arranged on a support, such as a circuit board, separate from the heating unit.
  • These elements work with a much lower voltage or supply voltage than the heating element of the heating unit, which is also expediently at least partially arranged as a coating on a support, such as a circuit board.
  • a support such as a circuit board.
  • the electrically conductive connections between the control unit, the one or more heating circuits, sensors or the like Made with strands, there is a high cost for wiring.
  • the two supports on the base of the heating device must be secured separately for each other, since they or the like through flexible connection with the strands, wires or the like. without this definition, one would be able to move against one another with little force.
  • the invention has for its object to provide a heating by which disadvantages of known designs or the type described are avoided and which ensures a high heating power or simple assembly, in particular with a simple and compact structure.
  • the heating unit can be precisely defined with respect to the associated control unit and can be arranged to be movable or rigidly to a limited extent.
  • the strength of the connection between the units is expedient so that one unit can freely carry the other in its operating arrangement on the device, so that the second-mentioned unit does not require any special attachment to the device, but is carried solely by the connection to the first-mentioned unit.
  • the two units can also be heating units, of which possibly only one or none contains a control unit or electronic control elements.
  • connection between the units as well as the units themselves can provide means to protect the controls against Overheating included, so that the controls are heated up to a maximum of 135 ° C or 130 ° C despite the direct connection to the heating elements, although the heating elements have a temperature that is several times higher.
  • These means dissipate the heat generated by the heating element bypassing the control elements so quickly that the control elements are not heated beyond the above-mentioned temperatures even in continuous operation over several minutes or hours.
  • the heat can be dissipated in the shortest possible way into the material to be heated directly from the carrier or through thermal coupling elements that are in direct contact with the heating unit and this material.
  • the maximum heating output of the individual heating unit can be at least 250, 500, 1000, 1500 or even 2000 watts.
  • the largest linear dimension of the heating unit or of its support need not be greater than 200 or 150 mm.
  • the heating element is arranged on the heating vessel in such a way that the heating of the heating element results in an upward convection or circulating flow within the water, which is cooled parallel to the heating element and laterally over its edges into the area of the heating elements flows again.
  • connection between the two separate units or carriers can contain electrically conductive parts or be formed exclusively by them and is expediently inherently rigid.
  • connection can also contain electrically insulating connection parts or connection parts not acted upon by power or signal currents. It is particularly advantageous if both carriers are formed by a one-piece support body which is provided with electrical insulation in the region of the electrically conductive parts or consists entirely of insulating material.
  • the respective carrier can be made from a ceramic material, such as hard ceramic, from an electrically conductive material, such as aluminum, copper, steel or the like, with a dielectric layer, such as hard enamelling or glass, as insulation, from plastic, a flexible substrate, such as paper or the like consist.
  • the elements of the respective unit namely resistors and conductor tracks for connecting the respective resistor or the respective control element are expediently arranged on the associated carrier as an insoluble adhesive coating of at least 5 and at most 35 ⁇ m thick.
  • the coating can be applied as a paste by printing processes and then hardened.
  • the application in thick-film technology, in thin-film technology, in transfer printing or the like is suitable.
  • the respective sensor is expediently a temperature-variable resistor which, like any of the other control elements, is operated with a voltage of less than 20, 10 or 5 volts which is substantially lower than that of the heating element and can have a positive or negative temperature coefficient.
  • the heating element Since the heating element is extremely low in mass, it responds almost instantaneously to changes in the power supply or heat consumption. In order to keep the hysteresis in response to the control unit or the exceeding of the limit temperature by the heating element as small as possible, a very short controlled system or an almost immediate heat-conducting coupling between the heating element and the sensor for dry running or the like is provided. This coupling can essentially only take place via the carrier. Based on the largest surface area of the heating unit or the support or the resistance surface, a very high power density of over 15, 50, 70 or 100 W / cm 2 is possible. If the carrier consists of aluminum oxide ceramic, it has good thermal conductivity.
  • the entire heating element, the sensor arrangement, the electronic control unit, a temperature protection element such as a temperature monitor, temperature limiter, temperature switch or the like. and all conductor tracks can be arranged on the same surface or side of the carrier. But they can also be arranged on separate surfaces which are approximately parallel at an angle or away from one another. At a distance within its outer edges or on the outer edges, the carrier is expediently free of breakthroughs, so that it is limited only by continuously or evenly continuous edge surfaces and is protected from stress cracks.
  • the heating or heating unit can be produced essentially completely automatically with handling machines or with very little wiring.
  • the control unit and its support give the thermal power loss of the control essentially completely to the substance to be heated, so that there is a very high efficiency.
  • the heating unit can be extremely compact, e.g. continuously plate-shaped, are formed, with only individual control elements such as transistor, triac, thyristor or the like. can protrude across the associated surface of the carrier.
  • the heating unit or its current-carrying parts can also be electrically insulated, for example by coating, in such a way that the heating unit is embedded directly in the substance to be heated or is immersed in the case of an aqueous solution. It can only or in combination the heating side, the side facing away from it, the edge surfaces or the like. the heating unit or the wearer are in direct contact with this substance. This results in an even faster heat dissipation and therefore the possibility of a further increase in the power density mentioned.
  • the means for heat dissipation expediently contain a heat-conducting base made of a solid .
  • This base can have one or more layers, with all the layers being bonded to one another essentially over the entire surface.
  • the layers can the carrier, hardened thermal adhesive, an insulating plate, a heat-conducting flange or the like. included, which also serves to attach the heating or heating unit to the device.
  • This flange advantageously has a thermal conductivity of at least 70, 150 or 300 W / mK.
  • the conductor carrier or the flange is in direct, good heat-conducting contact with the substance to be heated, such as a fluid, so that most of the heating power is transferred to this substance via it.
  • the flange can consist of copper, aluminum or a similar, in particular metallic, material.
  • the heat-conducting adhesive expediently contains a ceramic mass which becomes brittle or hard after the plastic application.
  • the design according to the invention also provides means for self-cleaning the heating unit from solidified adhering deposits, such as lime. In the cyclical heating mode, deposits from a certain layer thickness gradually burst off without damaging the heating unit.
  • a heating or start-up control is expediently provided for starting up the heating, which first detects the thermal reaction of the heating unit in a short test run for less than five, three or 2 seconds and only after evaluating this reaction and after a pause releases the heating operation, which often takes a long time.
  • the procedure is advantageously such that the heating element is initially subjected to a power pulse of approximately one second at full operating power and then the power supply is completely interrupted again or at least substantially reduced over a period of at least 2, 3 or 4 times longer.
  • the speed of the temperature rise of the heating unit or of the carrier is determined by the power pulse via a time recording element.
  • the heating element is subjected to the full operating power in continuous operation after the pause time mentioned.
  • the heating then heats the fabric up to the target temperature, which can be changed using a manually or continuously adjustable setpoint generator. If this target temperature is reached, the control unit interrupts or reduces the power supply in order to supply it again after a lower temperature limit value has been reached.
  • the permissible limit value of the speed measured on the sensor or dry-running sensor depends on the absolute temperature of the heating unit and is modified accordingly by the control unit.
  • the heating 1 contains a structural unit 2 and an electronic temperature controller or a control, parts of which are arranged separately from the unit 2 and can be connected to the latter via connecting or signal lines. At least part of the control, however, is arranged as an electronic circuit or control unit 6 in a fixed position on the unit 2.
  • the unit 2 has a plate-shaped, flat and continuously one-piece support 3, 4 made of a material which is a good heat conductor but is electrically insulating.
  • the carrier 3, 4 carries on the same plate side as that Units 5, 6 conductor tracks 7, so that no current-carrying parts of the structural unit 2 have to be provided on the side of the plate facing away from them.
  • two connecting elements 8 are provided for device lines, via which both units 5, 6 are supplied with current, in particular mains and alternating current of 110 or 230 volts.
  • heating elements 9 are provided as heating elements 9. These are expediently of the same design, but shown in FIG. 1 in different designs.
  • the left heating element 9 is made continuously of resistance material over its length, while the right heating element is divided into longitudinal sections which are spaced one behind the other and are connected to one another in series by interconnects of lower resistance. Thereby a higher thermal load on the carrier 3, 4 is possible.
  • the elongated rectangular beams 3, 4 have two parallel, longer outer edges 11 and two shorter outer edges 12 connecting them at right angles. Each of the edges or edge surfaces 11, 12 is continuously straight or flat.
  • the length of the edges 11 can be less than 200 or 150 mm and the length of the edges 12 less than 100 or 75 mm.
  • edges 11 are preferably approximately 100 mm long and the edges 12 approximately 50 mm long. All conductor tracks 7 are first printed on the board surface. Then the resistors are also printed as layers so that their connection ends cover the associated connection fields of the conductor tracks 7 and are thus connected to them in an electrically conductive manner.
  • the surface roughness of the coated zones of the carrier 3, 4 is at most 0.8 or 0.6 ⁇ m.
  • Each resistor 9 is parallel to one of the edges 11 and continuously therefrom at a distance which is smaller than its continuously constant strip width.
  • the resistor 9 extends over most of the length of the edge 11, namely over more than 75 or 85% thereof. No further current-carrying parts or resistors are provided between the resistor 9 and the adjacent edge 11 or 12.
  • Two conductor tracks 7 lie parallel to the edges 12 and immediately adjacent to them at a distance which can be the same as that of the resistors 9 from the edges 11. The ends of these conductor tracks are in conductive contact with the respectively associated ends of both resistors 9, so that the resistors 9 with these conductor tracks 7 surround the central field 4 of the carrier 3, 4 continuously in a frame-like manner.
  • the entire circuit 10 lies between the connecting members 8 in the middle field 4 and can have a minimum distance from the resistors 9 and their connecting tracks 7, which corresponds to their distance from the edges 11, 12.
  • the circuit 10 is supplied with current of at most 30, 20 or 15 volts via the connecting elements 8, with the interposition of a single voltage reducer emitting this output voltage, which can be, for example, a series resistor 29 printed on the carrier 4, so that no transformer is required is.
  • the control unit 6 contains control elements 13 to 27, 30, each of which can be provided directly on the carrier 4 or separately from the unit 2 in such a way that it is connected to the unit 2 in a controlling manner via suitable flexible signal or connecting lines.
  • the power current is supplied to the heating elements 9 connected in parallel with the interposition of an actuator 25, such as a triac, via a current conductor 28.
  • the heating elements 9 are thermally coupled to sensors 14, 15 via the carrier 3, 4 or the medium to be heated or additional heat conducting elements. If they belong to the unit 2, they can easily be resistance sensors printed as a layer, which have a negative or positive temperature coefficient.
  • the sensors 14, 15 each also act as dead time or time delay elements 13 and comprise a dry-running sensor 14 and a sensor 15 for detecting the temperature of the medium to be heated, which is also arranged separately from the unit 2 and at a distance therefrom on the device may be that it is immersed in the medium.
  • 3 can be arranged on a one-piece carrier 3, 4 or on a single circuit board.
  • the sensors 14, 15 act on signal signal amplifiers 16 via signal lines and these in turn on signal lines on differentiators 17 for evaluating the measurement signals.
  • the differentiators 17 act on signal lines on threshold switches 18, which open and close when corresponding limit temperatures are reached.
  • One amplifier 16 acts via a signal line directly on a threshold switch 18, which can be set to a limit value, namely a maximum temperature of the sensor 14, using an actuator 26.
  • a further limit value, namely the maximum temperature rise rate at the sensor 14, can also be set via a further actuator 27.
  • the differentiator 17 for the measurement signal of the sensor 15 is connected to a further threshold switch 18 via a signal line.
  • the circuit 10 can also contain a microprocessor for evaluating the signals mentioned, which is attached directly to the carrier 4 or its current-carrying side and forms the zero-voltage switch 30.
  • the sensor 14 or 15 is an elongated resistance layer printed directly on the carrier 3, 4, which is parallel to the resistor 9 and has a length which is smaller than that of the resistor 9, but greater than half or two thirds of the length of the resistor 9.
  • the ends of the sensor 15 are thereby the same Distances from the ends of the resistor 9 set back.
  • the width of the resistor 15 is substantially smaller than that of the resistor 9.
  • the continuously constant distance of the sensor 15 from the resistor 9 is at most as large as or smaller than the width of the resistor 9, approximately equal to its distance from the adjacent edge 11 and larger than the thickness of the carrier plate.
  • the respective unit 2 contains the sensor 14 or 15, the electronic circuit 10, the actuator 25 and the heating element 9 on the carrier, while the adjusting element 19 is arranged separately on the device.
  • Two or more units 2 can be connected to each other to form an inherently rigid unit, for example in such a way that their heating units 5 or paired heating elements 9 are connected in series with one another.
  • the actuator 19 can act jointly on all units 2, and only a single sensor 15 can be provided for all units 2. Nevertheless, each unit 2 is independently protected from overheating by a sensor 14 or the circuit 10, independently of the other units. If the heating elements 9 of one unit 2 fail or are switched off, the heating elements of the other units 2 can remain in operation.
  • Adjacent units 2 can connect to one another at the same level or be offset from one another on the level.
  • the unit 2 is combined in a sandwich-like manner with further layers 31 to 36, each of which extends over the largest part of the surface area of the carrier 3, 4.
  • Each layer can lie on the current-carrying side of the carrier or on the side remote from it, or each of the layers can be provided twice on both sides of the carrier.
  • the carrier is attached with its side facing away from the current-carrying side via an intermediate or adhesive layer 32 directly to the outside of a flange or plate 31 which can form the wall or at least part of the horizontal bottom of a vessel in which the medium to be heated is directly adjacent to the inside of this wall and the flange.
  • the other, current-carrying side of the carrier can lie freely within a removable cover, but is here covered with a further intermediate layer 33, which can thus also embed and cover all current-carrying parts, such as conductor tracks, resistors or the like, in an electrically insulating manner.
  • This layer 33 is arranged between the carrier 3, 4 and an electrical insulating layer, for example a hard ceramic plate 34.
  • a layer 35 is again arranged, which is designed like the layers 32, 33 and lies between the plate 34 and a plate-shaped flange 36.
  • the layers 32 to 35 consist of a good heat-conducting, for example ceramic material with electrically insulating properties.
  • the layers or layers can be provided with receiving recesses or openings, into which these control elements then protrude, but, like all other current-carrying parts, are encased completely watertight or can be embedded.
  • the flange 36 which is thicker than the layers 3, 4 and 31 to 35, can be electrically conductive and suitably consists of a particularly good heat-conducting metal, for example aluminum, copper or the like.
  • the flange 36 can lie continuously parallel to the layers 3, 31 to 35 or can have transversely angled or protruding parts for fastening or supporting the unit 2 on the device.
  • the connecting element 8 expediently has two plate-shaped legs at an angle to one another, one of which is parallel to the carrier 3, 4 and is electrically conductively fastened with its outer plate surface to the associated conductor track 7 by soldering or another adhesive connection.
  • the other leg protrudes transversely to the support plane from the support 3 and can be used as a plug, e.g. be designed as a flat plug or as a holder for snapping an electrical fuse. These plugs lie in a common and parallel plane to the edge surface 11.
  • the control members 13 to 25, 30, like the connecting members 8, can be fastened to the associated conductor tracks by appropriate adhesive or fused connections, without the need for additional fastening members.
  • the plate 31 which consists of a heat-conducting material of the type mentioned, for example aluminum, is a flange or bottom of a hot water boiler 37 trained so that their top is in direct contact with the boiler content.
  • the unit 2 is glued to its underside in such a way that the connections 8 remain accessible. Two further connections can be provided on the unit 2 in order to connect the actuator 19, for example a potentiometer, or the sensor 15.
  • the carriers 3, 4 are formed by separate bodies, which, however, are connected to one another in a rigid or dimensionally stable manner.
  • a carrier 4 can be parallel to the plane or congruent with the carrier 3.
  • a carrier 4 can also lie adjacent to an edge 11, 12 of the carrier 3 or at the same level as this.
  • the two carriers 3, 4 are connected to one another in a positionally fixed or adhesive manner via connecting members 38 and 39, respectively.
  • These links 38, 39 can only carry live metal parts or the like. be, which in turn can be made, for example, as stamped parts from sheet metal and can contain the connecting members 8.
  • the links 38, 39 can also form spacers between the supports 3, 4 and are or the like in the manner described by soldering. attached.
  • the separate carrier 4 is particularly expedient when the control unit 6 or individual parts 8, 13 to 25, 29, 30 of this unit cannot be accommodated spatially on the carrier 3 or when the carrier 3 reaches temperatures during operation which are for these parts could be harmful.
  • the power density, based on the surface area of the heating elements 9, can namely be substantially above 20 or 40 or 70 or 100 or 150 W / cm 2 . At least some of the control elements mentioned must not be heated significantly above 125 ° C. To ensure this, the training according to Figures 1 to 6 are provided.
  • the medium is up to a predetermined, continuously adjustable temperature, for example at most 100 ° C, heated.
  • overheating for example if there is no medium and the heat is dissipated from the unit 2, is avoided by the temperature monitors or temperature limiters mentioned, since these switch off the power flow immediately when running dry and switch on again automatically if the temperature falls below the limit value.
  • an electrical fuse such as a fuse, can also be provided on the unit 2, or its holder is fastened directly to the carrier 3, 4 or to one of the members 8, so that the fuse which is held by clamping is pulled off can be replaced non-destructively.
  • this detection can contain the control elements 21 to 23, namely an adjustable or adjustable default element 22, such as an R / C element for determining the course of the rise in temperature, a flip-flop 21 or the like. and a time or pulse control element 23.
  • the element 21 is influenced by the control element 20 and by the control elements 18 in each case via a signal line and in turn influences the elements 22, 23 via a signal line.
  • the element 22 influences the threshold switch 18, which is influenced by the sensor 15, and the element 23 influences, via a signal line with the interposition of the zero-voltage switch 24, the actuator 25 for applying power to the heating element 9.
  • the element 23 When the heating element 9 is switched on, the element 23 initially receives a time-limited power pulse of approximately a second.
  • the sensors 13 to 15 record the rate of rise of the temperature and the beginning of the temperature rise. If no limit values defined by the elements 17, 18, 22, 27, 30 are exceeded, the heating element 9 is subjected to the full power after a corresponding pause of at least 3 seconds, which is longer than the power pulse.
  • the permissible limit value of the speed of the temperature rise at sensor 14 or 15 depends on the absolute temperature of unit 2. If limit values are exceeded, the heating element remains out of operation.
  • the control monitors the entire heating process until the desired temperature is reached and, in the event of an error or incorrect operation, ensures that the heating is switched off safely and reliably. Flawless operation is guaranteed in all possible operating conditions.
  • Such operating states can be switching on the heating in dry running with or without residual water, with cold or hot heating and with an inclination of the heating element of approximately 5 ° on all sides.
  • the heating or its thermally closest device area coupled to the water expediently forms the ideally horizontal bottom of the water reservoir.
  • the control switches off when the water is drained during the heating process and when the boiling temperature is reached, without automatically switching to the on state to return.
  • the switch-off temperatures are not affected by calcification.
  • the renewed, in particular manually initiated, start of the heating process is also possible when the water is already hot.
  • the resistance sensors are provided to record the three possible operating cases of complete dry running, small amounts of residual water and normal operation with water in hot and cold conditions.
  • the dry-running sensor 14 is located as close as possible to the heating surfaces and can be at a smaller distance from these or the heating conductors than the sensor 15. Since the sensor 14 does not have to be galvanically separated from the heating conductors, a distance of at most 5 or 2 or one millimeter is sufficient. Due to the metal flange 31 or 36 lying above it, the sensor 14 can additionally be thermally coupled to the heating surfaces in an improved manner.
  • the senor 15 can lie freely in the area of an opening or a recess in the flange 31 or 36, so that it is thermally closer to the sensor 14 and less closely coupled to the heating conductor than the sensor 14.
  • the temperature of sensor 15 rises with a delay, so that this delay can be evaluated to detect dry running.
  • the flange 31 can be a round, circular or rectangular plate, opposite the edge of which the unit 2 is set back on all sides, which is only sealed with its edge as a closure for opening the bottom wall of the heating container to this bottom wall and is penetrated by lines or pipes can, via which an excess pressure in the heating tank is avoided by steam discharge or fresh water is fed into the heating tank.
  • the flange 31 can be detachably attached non-destructively and forms a preassembled structural unit with the heating.
  • the remote from the circuit 10 Side of the carrier 3 thus comes into direct, heat-conducting contact with the water, while the circuit 10 itself is completely dry and only needs to be covered with a protective cover that is accessible at all times.
  • the flange 31 covering the beam 3, 4 on all sides at the edge parallel to the beam plane has a safety distance from all conductors, in particular the heating elements 9 and the conductors 7, which is at least 2 or 3 mm and forms a creepage distance.
  • the control of the power curve of the heating at the beginning of the heating process is possible, in particular for heating powers below 200 W, by ramp-shaped phase control or by reducing the initial power by half-wave operation, but is not expedient at high powers for safety reasons.
  • An oscillation packet control could also be used for this, in which the relationship between the power pulse or oscillation packet and the power pause is changed in the course of the heating-up time, but strong noises can result here. It is therefore advisable to supply the heating elements with the full nominal power as soon as they are switched on. By monitoring the temperature profile, a possible dry running is then recognized and the heating is switched off.
  • the temperature or voltage at the sensor could be used directly as a signal value, but it is expedient to use the course of the rate of rise of the temperature as a signal value in order to enable dry running to be recognized as quickly as possible, especially when operating with water, this rate of rise is significant is less.
  • the limit value modules 18 and the memory element are used for this mode of operation 21 and the power section 7, 9 provided with the triac 25 as an actuator. Since with hot heating 1 the rate of increase in temperature is significantly lower than with a cold heating element, the limit value is expediently reduced with increasing temperature of the heating element and a further limit value is also specified, namely the maximum temperature of the heating element. In order to be able to start the heating process again even with hot water, the limit must be increased, which would, however, significantly impair the protection when running dry. The additional fuse for quickly switching off the heating element in this case therefore contains the pulse control 23. During the power pulse and the pause, the temperature profiles of the sensors 14, 15, if necessary separately, are evaluated, and if the rate of rise is too high, the further heating process before the pause ends canceled.
  • the evaluation of the rate of rise of the water temperature or the sensor 15 in connection with the pulse control increases the safety of the heating 1 considerably. While the temperature rise at sensor 15 takes place only slowly during operation with water, a much faster, pulse-like rise can be determined when running dry. This increase can also be delayed during the break. This behavior prevents the heating element 9 from being switched on again after the pause time has elapsed.
  • a voltage curve is used as the limit value for the speed of the temperature rise, which is still relatively low during the impulse application and the subsequent pause time, but increases to a higher final value during continuous operation of the heating process.
  • the measuring signal amplifier 16 is expediently designed as a differential amplifier and amplifies the input voltage of the Sensors 14, 15 many times over, so that the course of the water temperature increasing from 0 ° to 100 ° C is assigned a decreasing voltage range of, for example, at most 15 or 10 volts to 0 volts.
  • This anti-proportional ratio ensures that in the event of a wire break or other failure of a component of the heating system 1, a shutdown takes place because the electronics 10 detects this failure in the same way as hot or boiling water.
  • the amplifier 16 is advantageously preceded by a bridge circuit with which the dependence on voltage fluctuations in the mains current or the like is reduced and a simplified adjustment of the input stage to the sensor is achieved.
  • the input resistances of the bridge circuit are small compared to the resistances of the amplifier 16, for example in such a way that at 0 ° C. in both input bridge circuits with 4.5 volts approximately half of the voltage supplied results. Both components for dry running and water temperature show the same fluctuations in the input voltage.
  • the heating element is cold, there is an output voltage of the bridge amplifier of the input stage, which is only slightly lower than the input voltage when the heating 1 is cold and substantially lower when the heating 1 is hot.
  • the resistors of the differential amplifier have a high resistance to the bridge resistors.
  • the rate of rise of the temperature at sensor 14 or 15 is detected by differentiating the temperature measurement signal over time, for which purpose the differentiator 17 is provided with a suitable operational amplifier.
  • This circuit expediently contains an input resistor connected in series and a capacitance connected in parallel, such as a capacitor, in the feedback branch. in order to reduce the amplification of high frequencies or interference signals and to prevent the input resistance from decreasing as the frequency and tendency to oscillate increase.
  • the control element 22 is adjusted so that at a maximum rate of increase in temperature or voltage of 4 volts per second, the output voltage of this differentiator corresponds to 4.5 volts half of the input voltage mentioned.
  • the heating process or the power supply to the heating elements 9 is ended when the set target value of the water temperature has been reached, the heating 1 has an excess temperature, the rate of rise of the temperature of the sensor 14 is too high or if the rate of rise of the temperature of the sensor 15 during the Start phase or increases too high during the power pulse and the following pause.
  • the associated sensor voltages are monitored and evaluated by a comparator of the respective limit or threshold switch 18. This comparator compares the actual value with the limit value which can be changed by setting.
  • the polarity of the difference in the input voltage at the operational amplifier determines the polarity of the output voltage, so that an overshoot or undershoot of the limit value can cause the output voltage to tip over instantaneously or suddenly.
  • the four limit elements 18 are connected to one another and connected to the reset input of the memory element 21 via an OR gate which consists of universal diodes.
  • the flip-flop memory element 21 represents the memory element for switching the heating power on and off and is designed in such a way that its reset has priority over the manual setting by the control element 20 and that the setting with the control element 20 only on the basis of a single pulse takes place so that when the start button of link 20 is continuously pressed, no cycle operation can occur in the event of dry running.
  • the power pulse triggered by the link 23 at the beginning of the heating process is achieved by superimposing two RC charging voltages with an opposite profile. This voltage causes the desired power curve at the comparator of the zero voltage switch 30 in connection with the reference voltage applied there.
  • the pulse length of the power supply or the subsequent pause time results from the time constants of the two RC elements. Falling below or exceeding the limit voltage triggers the desired power curve on the comparator.
  • the resistors and capacitors of the two RC circuits determine the ratio between the pulse and pause length, which can be changed at any time without changing the ratio by changing an applied voltage.
  • the zero voltage element 30, which also serves as an ignition unit, enables appropriate control by an integrated triac and is designed as an integrated circuit. It contains a full-wave logic that excludes any DC load on the network. An integrated synchronization unit ensures perfect ignition of the triac in the zero crossing of the mains voltage. A further integrated ramp generator enables the construction of an oscillation packet control in a simple manner. It also contains an additional comparator and an ignition pulse amplifier, which enables the triac to be connected directly to the mains voltage via a series resistor.
  • the link 30 enables a regulated voltage supply and has eight separate connection poles here. The negative voltage supply of the entire circuit is provided by the link 30, while the comparator is provided for generating the power pulse.
  • the positive supply voltage for the operational amplifier is provided by means of a Z diode.
  • the entire supply voltage is obtained directly from the mains voltage via a high-performance series resistor 29 using thick-film technology, so that no transformer or the like is required.
  • the voltage supply to the link 13 takes place without a transformer.
  • the entire circuit is operated with negative voltage.
  • the module 30 is operated via a resistor and a diode directly on the supply network. With the one-way rectification by the diode, a negative pulsating voltage arises.
  • the resistor serves to limit the current and is designed in accordance with the power loss that falls on it.
  • the pulsating AC voltage is smoothed by a charging capacitor.
  • a DC voltage of 9.25 volts is produced by the internal Z-diode in element 30.
  • module 30 is used as a proportional controller.
  • the frequency of the ramp generator can be set with a capacitor at two of the connections of the link 30.
  • a resistor is provided in order to achieve synchronous switching with the zero crossing of the mains voltage.
  • the resistors and the like mentioned are provided as coatings on the carrier 4.
  • the power pulse is not detected by the water temperature differentiators 17. After the pause has elapsed and the power has been switched on again, the temperature rise at the differentiator 17 of the sensor 15 takes place with a shorter delay than the pause length. In addition, the limit value of the dry-running component 13, 14, 16, 17 drops so that it is not exceeded when operating with water.
  • the course of the limit value of the water temperature component 13, 15, 16, 17 is specified by an RC element in such a way that it is very low at the beginning of the heating phase, but increases to its high final value in the further course.
  • the power pulse can already be detected by the differentiators 17, in particular if the flange 31 or 36 has already stored so much heat that it cannot absorb any more thermal energy. This reduces the delays in evaluating the water temperature curve.
  • the large heat capacity of the flange 31 or 34 or 36 can absorb the heat quantity of the power pulse almost completely.
  • the temperature rise detected by sensor 14 is then not sufficient to exceed the only slightly reduced limit value. Dry running is only recognized and the power supply is interrupted shortly after the power is restored.
  • the effects of the configurations according to FIG. 4, by means of which the heat is rapidly dissipated for the most part from the carrier 3 and before reaching the carrier 4, can e.g. can be achieved in a simple manner only in that the carrier 3, 4 is formed by the flange 31 or 36 and this is provided on its current-carrying side with an electrically insulating, glass-hard coating which receives the current-carrying tracks.
  • This coating can be laminated on or laminated on or produced by enamelling.
  • the electrically conductive flange can be grounded to avoid 2 short circuits if the unit breaks. This can also be achieved in that a metal layer by printing or the like on the unit 2. applied or an electronic protection circuit is provided.
  • the thickness of the flange 31 or 36 can be less than 3 or 2 mm, in particular approximately 1.5 mm. All stated properties and values can be provided exactly as described or only approximately or essentially as described and can also deviate greatly therefrom. The fact that heating elements and their electronic control are combined to form an inherently rigid module results in a very compact design.

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  • Control Of Resistance Heating (AREA)
EP97118676A 1996-11-01 1997-10-28 Chauffage électrique et sa commande Withdrawn EP0840534A1 (fr)

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DE1996145095 DE19645095A1 (de) 1996-11-01 1996-11-01 Beheizung
DE19645095 1996-11-01

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Cited By (4)

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EP0901311A3 (fr) * 1997-09-02 1999-06-09 GKR Gesellschaft für Fahrzeugklimaregelung mbH Appareil de chauffage électrique, en particulier pour véhicule
EP0967836A1 (fr) * 1998-06-25 1999-12-29 White Consolidated Industries, Inc. Système de commande de interrupteur de panneau de chauffage avec annulation du courant de fuite
EP1157867A1 (fr) * 2000-05-23 2001-11-28 Catem GmbH & Co.KG Dispositif de chauffage électrique, utilisé en particulier dans les véhicules
EP1510381B2 (fr) † 2003-08-29 2013-11-20 Valeo Systemes Thermiques Elément de chauffage électrique pour appareil de ventilation, de chauffage et/ou de climatisation d'habitacle

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FR2793104B1 (fr) * 1999-04-29 2001-06-15 Moulinex Sa Procede de pilotage d'un element chauffant d'appareil electrique de chauffage de liquide
DE102004060949A1 (de) * 2003-12-23 2006-02-09 BSH Bosch und Siemens Hausgeräte GmbH Dickschichtheizung für Fluide und Durchlauferhitzer
DE102005029921A1 (de) * 2005-06-22 2007-01-04 BSH Bosch und Siemens Hausgeräte GmbH Heizvorrichtung für Fluide und Haushaltsgerät
DE102010050007A1 (de) * 2010-11-02 2012-05-03 Böhm GmbH & Co. KG Beheizungssteuerung
DE102012213385A1 (de) * 2012-07-30 2014-05-22 E.G.O. Elektro-Gerätebau GmbH Heizeinrichtung und Elektrogerät mit Heizeinrichtung

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GB1187595A (en) * 1966-04-27 1970-04-08 Telefunken Patent Improvements in or relating to Integrated Circuits
DE2354719A1 (de) * 1973-11-02 1975-05-15 Licentia Gmbh Anordnung zur temperaturstabilisierung
US4374316A (en) * 1979-08-29 1983-02-15 Kyoto Ceramic Co., Ltd. Semiconductor integrated circuit supporter having a heating element
US4841170A (en) * 1986-12-08 1989-06-20 John Fluke Mfg. Co., Inc. Temperature controlled hybrid assembly
GB2228634A (en) * 1989-01-26 1990-08-29 Otter Controls Ltd Liquid heater controller with boil and dry-boil detection
GB2283156A (en) * 1993-10-21 1995-04-26 Otter Controls Ltd Association of heating element and thermal control
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0901311A3 (fr) * 1997-09-02 1999-06-09 GKR Gesellschaft für Fahrzeugklimaregelung mbH Appareil de chauffage électrique, en particulier pour véhicule
EP1530405A2 (fr) 1997-09-02 2005-05-11 Behr GmbH & Co. KG Dispositif de chauffage électrique, particulièrement pour véhicules automobiles.
EP1492384A3 (fr) * 1997-09-02 2005-12-07 Behr GmbH & Co. KG Dispositif de chauffage électrique, utilisé en particulier pour des véhicules
EP1530405A3 (fr) * 1997-09-02 2007-04-18 Behr GmbH & Co. KG Dispositif de chauffage électrique, particulièrement pour véhicules automobiles.
DE19738318C5 (de) * 1997-09-02 2014-10-30 Behr Gmbh & Co. Kg Elektrische Heizeinrichtung für ein Kraftfahrzeug
EP0967836A1 (fr) * 1998-06-25 1999-12-29 White Consolidated Industries, Inc. Système de commande de interrupteur de panneau de chauffage avec annulation du courant de fuite
EP1157867A1 (fr) * 2000-05-23 2001-11-28 Catem GmbH & Co.KG Dispositif de chauffage électrique, utilisé en particulier dans les véhicules
US6392207B2 (en) 2000-05-23 2002-05-21 Catem Gmbh & Co. Kg Electric heating device, especially for use in motor vehicles
EP1510381B2 (fr) † 2003-08-29 2013-11-20 Valeo Systemes Thermiques Elément de chauffage électrique pour appareil de ventilation, de chauffage et/ou de climatisation d'habitacle

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