HOME APPLIANCE HEATING DEVICE

Description

[0001] The invention is based on a household appliance heating device according to the preamble of patent claim 1.

[0002] A domestic appliance heating device is already known from the prior art, which has a first heating connection and a second heating connection, each of which can be connected to a supply connection of a supply network. A first switching element is connected between the first heating connection and a first supply connection. In order to start a heating operating state and thus heat the heating element, a conduction path between the heating element and the supply connections is established by means of the first switching element. To interrupt or terminate the heating operating state, the conduction path between the heating element and the supply connections is interrupted by means of the first switching element. The first switching element is actuated, for example, by means of an operating element. In addition, the domestic appliance heating device has a measuring unit with a measuring input to which a potential is applied in the heating operating state.In order to enable a clear measurement using the measuring unit, the type of supply network to which the supply connections are connected must be known. The type of network depends on the country, which is why different household appliance heating devices may be used, and in particular sold, depending on the country. With a known type of network, in some countries, such as Europe or Japan, a clear polarity of the heating connections must also be ensured, since in these countries the neutral conductor is connected to one of the supply connections. On the one hand, this can be achieved using a complex device that requires at least phase detection, a control unit and a corresponding relay circuit. On the other hand, correct polarity of the heating connections could be ensured when the heating connections are connected to the supply connections, in particular by an electrician and / or fitter.

[0003] From DE 10 2014 206279 A1 a household appliance heating device with a measuring unit and a control unit is already known, whereby the polarity of the connections can be determined based on the potentials present at the supply connections.

[0004] The object of the invention is, in particular, to provide a generic device with improved properties with respect to low effort in determining a network configuration applied to heating connections. This object is achieved by the features of patent claim 1, while advantageous embodiments and further developments of the invention can be found in the subclaims.

[0005] The invention is based on a household appliance heating device, in particular a cooking appliance heating device, with at least one heating element which has at least two heating connections, each of which is provided for connection to one of at least two supply connections of a supply network, in particular a household network, with at least one first switching element which is connected between a first heating connection of the heating connections and a first supply connection of the supply connections, with at least one second switching element which is connected between a second heating connection of the heating connections and a second supply connection of the supply connections, and with a measuring unit which has at least one measuring input to which a potential is applied in at least one heating operating state.

[0006] According to the invention, the domestic appliance heating device comprises a control unit configured to interrupt a conduction path through the heating element by means of the first switching element when the second switching element is closed in at least one network type detection operating state, and to take into account a first potential present at the measuring input when determining a network type present at the heating element. A "domestic appliance heating device" is understood to mean, in particular, at least one part, in particular a subassembly, of a domestic appliance, in particular a cooking appliance, advantageously an oven. In particular, the domestic appliance heating device can also comprise the entire domestic appliance, in particular the entire cooking appliance.A "heating element" is to be understood in particular as an element which, in at least one heating operating state, is intended for preferably inductive heating, in particular with a heating power of at least 100 W, in particular of at least 500 W, preferably of at least 1000 W, particularly advantageously of at least 1500 W, and preferably of at least 3000 W. A "connection" of an object is to be understood in particular as an electrical contact point via which the object can be electrically connected to another object and at which an electrical potential is advantageously present in at least one operating state, in particular in the heating operating state. A "switching element" is to be understood in particular as an element which is intended to establish and / or break an electrically conductive connection between at least two points, in particular between at least two contacts of the switching element.The switching element is particularly designed as an electrical element and preferably has at least one control contact for receiving a control signal. The switching element can be actuated via the control contact and, in particular, can be switched between the contacts, in particular depending on a control signal generated by the control unit. The phrase "connecting" the switching element "between" two terminals is intended to mean, in particular, that a conducting path connecting the terminals to one another leads via the switching element, wherein the conducting path can conduct electrical current, in particular, only when the switching element is in a closed switching position. A "conducting path" is intended to mean, in particular, an electrically conductive connection intended to conduct an electrical current in at least one operating state, in particular in the heating operating state.A "measuring unit" is understood, in particular, to be a unit designed to detect a value of a potential present at the measuring input in the heating operating state and, in particular, to have at least one measuring output for advantageously outputting the detected value of the potential present at the measuring input to the control unit. A "measuring input" of the measuring unit is understood, in particular, to be a connection of the measuring unit to which an electrical potential to be detected is present, at least in the heating operating state. A "heating operating state" is understood, in particular, to be an operating state in which electrical current flows through the heating element, in particular to deliver electrical power.A "control unit" is to be understood in particular as an electronic unit that is preferably at least partially integrated into a control and / or regulating unit of a household appliance, in particular a cooking appliance, and that is preferably intended to control and / or regulate at least the heating element and / or the first switching element and / or the second switching element. The control unit preferably comprises a computing unit and, in particular, in addition to the computing unit, a memory unit with a control and / or regulating program stored therein, which is intended to be executed by the computing unit. A "network shape detection operating state" is to be understood in particular as an operating state in which a network shape applied to the heating terminals of the heating element can be detected.In particular, the control unit is provided to advantageously deactivate the heating element in the network type recognition operating state by opening the first switching element while the second switching element is closed, wherein in particular a heating power emitted by the heating element assumes a value of at least substantially zero. Advantageously, the second switching element is designed as a main switch. According to the invention, the control unit is designed to bring the first switching element into an open switching position and the second switching element into a closed switching position in the network type recognition operating state, whereby in particular a first electrical potential is applied to the measuring input, which the control unit takes into account when determining the network type applied to the heating element. In particular, the control unit is provided to store the first potential in the memory unit of the control unit in the network type recognition operating state.The network configuration defines and / or characterizes, in particular, a type of low-voltage network and / or a type of low-voltage network. For example, a network configuration could define a three-phase alternating current. In the case of a three-phase alternating current, the network configuration could, in particular, define a voltage with a value of at least substantially 400 V and / or of at least substantially 415 V and / or of at least substantially 200 V and / or of at least substantially 380 V. Alternatively or additionally, a network configuration could, in particular, define a TN system and / or a TT system and / or an IT system. In particular, the network configuration could, alternatively or additionally, define a single-phase alternating current.In the case of single-phase alternating current, the network type could, in particular, define a voltage with a value of at least substantially 230 V and / or at least substantially 240 V and / or at least substantially 200 V and / or at least substantially 220 V. The network type could, in particular, define different low-voltage networks in different countries. In particular, the network type could vary depending on the country. "Intended" is understood to mean, in particular, specially programmed, designed, and / or equipped. The fact that an object is intended for a specific function is understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0007] Such a design makes it possible, in particular, to achieve low effort in determining a network type applied to the heating connections. This preferably makes it possible to achieve low costs. Particularly advantageously, the household appliance heating device can be connected to a respective power grid in different countries without any problems. Furthermore, a quick assembly and / or production process can be achieved, both during manufacture of the household appliance heating device and during connection of the household appliance heating device by an end user, who in particular can do without the assistance of an electrician and / or fitter. This also makes it possible to provide a high level of comfort for the end user. Furthermore, a simple, uncomplicated circuit and thus, in particular, low maintenance effort can be achieved.In particular, a cost-effective determination of a network configuration can be achieved using a software algorithm, whereby additional hardware can be dispensed with. The domestic appliance heating device and / or a domestic appliance comprising the domestic appliance heating device can be used worldwide, whereby special adaptations regarding wiring and / or electronics and / or software due to different network configurations can be dispensed with.

[0008] According to the invention, the control unit is designed to interrupt a conduction path through the heating element by means of the second switching element when the first switching element is closed in the network shape recognition operating state, and to take into account a second potential present at the measuring input when determining the network shape applied to the heating element. In particular, the control unit is designed to store the second potential in the memory unit of the control unit in the network shape recognition operating state. According to the invention, the control unit is designed to interrupt a conduction path through the heating element by means of the first switching element when the second switching element is closed in the network shape recognition operating state, and to take into account a first potential present at the measuring input when determining the network shape applied to the heating element.Particularly advantageously, the control unit is provided to interrupt a conduction path through the heating element in the network type detection operating state, first by means of any one of the switching elements when the other switching element is closed, and then by means of the other switching element when any one of the switching elements is closed, and to take both potentials present at the measuring input into account when determining the network type applied to the heating element. According to the invention, the control unit is designed to compare the first potential and the second potential with each other in the network type detection operating state and to calculate a difference between the first potential and the second potential.In particular, the control unit is designed to determine the magnitude of the difference between the first potential and the second potential in the network shape detection operating state and, in particular, to compare the magnitude of the difference between the first potential and the second potential with a differential reference potential stored in the memory unit of the control unit. This allows the network shape to be determined in a particularly simple manner. In particular, the potentials present at the heating terminals can be treated separately and / or differentiated from one another. Particularly advantageously, any type of network shape can be detected based on two measurements.

[0009] Furthermore, it is proposed that the control unit be designed to detect, in the network type detection operating state, the presence of a neutral conductor at one of the supply terminals based on the potentials present at the measuring input. In particular, the control unit is provided to infer, in the network type detection operating state, the presence of a neutral conductor at one of the supply terminals if the absolute value of the difference between the first potential and the second potential is greater than the differential reference potential stored in the memory unit of the control unit. This makes it possible to distinguish between different network types, in particular through simple software operations.

[0010] It is further proposed that the control unit be designed, particularly in the case of a neutral conductor being present at one of the supply connections in at least one polarity detection operating state, to determine the supply termination to which the neutral conductor is present, particularly based on the potentials present at the measuring input. In the case of a neutral conductor being present at one of the supply connections, the control unit is particularly provided to compare the first potential in the polarity detection operating state with a lower reference potential stored in the memory unit of the control unit. In particular, the control unit is provided to detect the presence of a neutral conductor at the first heating connection and, in particular, additionally the presence of a phase conductor at the second heating connection in the polarity detection operating state if the first potential is lower than the lower reference potential.The control unit is particularly provided to compare the first potential with an upper reference potential stored in the memory unit of the control unit in the polarity detection operating state. In particular, the control unit is provided to detect, in the polarity detection operating state, if the first potential is greater than the upper reference potential, the presence of a neutral conductor at the second heating connection and, in particular, additionally the presence of a phase conductor at the first heating connection. Alternatively or additionally, the control unit is particularly provided to compare the second potential with a lower reference potential stored in the memory unit of the control unit in the event of a neutral conductor being present at one of the supply connections in the polarity detection operating state.In particular, the control unit is provided to detect, in the polarity detection operating state, the presence of a neutral conductor at the second heating connection and, in particular, additionally, the presence of a phase conductor at the first heating connection if the second potential is lower than the lower reference potential. In particular, the control unit is provided to compare the second potential with an upper reference potential stored in the memory unit of the control unit in the polarity detection operating state. In particular, the control unit is provided to detect, in the polarity detection operating state, the presence of a neutral conductor at the first heating connection and, in particular, additionally, the presence of a phase conductor at the second heating connection if the second potential is higher than the upper reference potential.A "polarity detection operating state" is to be understood in particular as an operating state in which a polarity direction applied to the heating terminals of the heating element can be detected.

[0011] In particular, the control unit is provided to advantageously deactivate the heating element in the polarity detection operating state by opening the first switching element while the second switching element is closed, wherein in particular a heating power emitted by the heating element assumes a value of at least substantially zero. Alternatively or additionally, the control unit is provided to advantageously deactivate the heating element in the polarity detection operating state by opening the second switching element while the first switching element is closed, wherein in particular a heating power emitted by the heating element assumes a value of at least substantially zero. This makes it possible to operate the household appliance and / or in particular to detect overheating of the heating element at an early stage, regardless of the plug-in direction of a device plug in a connection socket of the supply network.

[0012] The control unit is particularly provided to conclude, in the network type detection operating state, that a neutral conductor is absent at one of the supply terminals and, in particular, that phase conductors are present, if the absolute value of the difference between the first potential and the second potential is smaller than the differential reference potential stored in the memory unit of the control unit. Preferably, the control unit is designed to detect, in the network type detection operating state, that phase conductors are present at the supply terminals based on the potentials present at the measuring input. In particular, the control unit is provided to check the validity of the first potential and / or, in particular, the second potential in the network type detection operating state, in particular for use in detecting the presence of phase conductors at the supply terminals.The control unit is particularly designed to compare the first potential and / or, in particular, the second potential with a validity range stored in the memory unit of the control unit in the network configuration detection operating state and, in particular, to conclude that phase conductors are present at the supply terminals if the first potential and / or, in particular, the second potential are within the validity range. This allows for a high level of operator convenience and / or for the simple detection of phase conductors present at the supply terminals.

[0013] The control unit is particularly designed to dispense with the use of the first potential and / or, in particular, the second potential when detecting the presence of phase conductors at the supply terminals in the network type detection operating state, particularly if the first potential and / or, in particular, and, the second potential are / are outside the validity range. Preferably, the control unit is designed to detect at least one device defect based on the potentials present at the measuring input in the network type detection operating state, particularly if the first potential and / or, in particular, and, the second potential are / are outside the validity range. This makes it possible to achieve, in particular, a high level of safety for an operator.

[0014] It is further proposed that the control unit be designed to determine a switch-off limit value for the heating element in the network type recognition operating state based on the determined network type. In particular, at least two, advantageously at least three, particularly advantageously at least four, and preferably several different switch-off limit values ​​for the heating element are stored in the memory unit of the control unit. In particular, a respective switch-off limit value is assigned to a network type. The control unit is particularly provided to determine a switch-off limit value assigned to the determined network type in the network type recognition operating state and, in particular, to take the determined switch-off limit value for the heating element into account in the heating operating state.As a result, the heating element can be protected from overheating, particularly regardless of the type of network connected to the heating terminals, which in particular allows a long-lasting design to be achieved.

[0015] It is further proposed that the household appliance heating device comprise at least one sensor element configured to detect a leakage current from the heating element in the heating operating state. A "sensor element" is understood, in particular, to be an element designed to receive an electrical current, in particular a leakage current, emerging from the heating element in the heating operating state and advantageously transmit it to at least one further unit, in particular to the measuring unit.A "leakage current" from the heating element is understood to mean, in particular, an electrical current that differs from an electrical current exiting the heating element via one of the heating connections and that exits the heating element via at least one path that differs from an electrical connection between one of the heating connections and one of the supply connections and advantageously represents a high-impedance conduction path in at least one operating state, in particular with resistance values ​​in a range of several to several MΩ. This makes it possible, in particular, to achieve precise detection of the leakage current and / or early fault detection. Furthermore, by detecting the leakage current, a temperature of the heating element can be determined.

[0016] For example, the control unit could be provided to immediately execute an emergency shutdown upon detection of a leakage current from the heating element by deactivating the heating element, in particular by means of the first switching element and / or advantageously by means of the second switching element. Preferably, the control unit is designed to determine at least one parameter dependent on the leakage current of the heating element in the heating operating state. For example, the parameter could comprise a value of the leakage current. It is also conceivable for the parameter to comprise a point at which the leakage current exits the heating element. Preferably, the parameter comprises a temperature of the heating element. This advantageously makes it possible to achieve a high level of safety in the heating operating state. Furthermore, overheating of the heating element can be detected at an early stage and, in particular, countermeasures can be initiated.

[0017] It is further proposed that, at least in the heating operating state, at least two parallel conduction paths lead from one of the supply connections to the measuring input, wherein a first conduction path of the conduction paths has a region between the heating element and the sensor element through which the leakage current flows. As a result, in particular, a polarity of the heating element can be determined independently of a heating operating state, whereby a high level of precision can be achieved. If the control unit is designed, in the heating operating state, to take into account the network type applied to the heating element when determining the parameters dependent on the leakage current of the heating element, in particular a precise determination of the parameters dependent on the leakage current of the heating element, in particular the temperature of the heating element.

[0018] For example, the heating element could be designed as a wound conductor, advantageously as a wound wire. The heating element is preferably designed as a layer. A "layer" is understood, in particular, to mean a configuration of an object in which a smallest cuboid that just barely encloses the object has a shortest edge and two long edges, wherein a shorter edge of the two long edges is at least 5 times, in particular at least 10 times, advantageously at least 15 times, and particularly advantageously at least 20 times as large as the shortest edge of the cuboid. The layer, in particular, has an at least substantially constant material thickness, which advantageously assumes a value of a maximum of 5 mm, in particular of a maximum of 1 mm, advantageously of a maximum of 0.5 mm, and particularly advantageously of a maximum of 0.1 mm.The phrase "the layer has an at least "substantially constant material thickness" is to be understood in particular as meaning that the material thickness in the region of the layer changes by a maximum of 20%, in particular by a maximum of 10%, and advantageously by a maximum of 5%. The heating element can be designed in particular as an induction heating element. Preferably, the heating element is designed as a radiant heating element and / or particularly advantageously as a resistance heating element. This allows, in particular, a compact design to be achieved. Furthermore, low costs can be achieved.

[0019] For example, the sensor element could be designed as a wound conductor, advantageously as a wound wire. Preferably, the sensor element is designed as a layer, which allows for a particularly space-saving design.

[0020] Advantageously, the heating element and the sensor element together form a capacitor, which allows, in particular, precise detection of the leakage current emerging from the heating element. Particularly in the case of a layered design of the heating element and the sensor element, the two together preferably form a plate capacitor.

[0021] It is also proposed that the household appliance heating device comprise at least one dielectric which is arranged at least partially between the heating element and the sensor element and has a temperature-dependent specific resistance, wherein the control unit is provided to utilize the temperature-dependent specific resistance of the dielectric to determine the characteristic variable. The temperature-dependent specific resistance of the dielectric changes only slightly, in particular by a maximum of 5%, advantageously by a maximum of 1%, particularly advantageously by a maximum of 0.5%, and preferably by a maximum of 0.1% of an amount of the specific resistance at a temperature of zero degrees Celsius, in particular below a threshold value, in particular of at least substantially 200°C and / or of at least substantially 300°C.At temperatures above the threshold value, a resistance value of the temperature-dependent specific resistance of the dielectric decreases sharply, wherein the resistance value of the dielectric at temperatures above the threshold value in particular has a resistance value of a maximum of 70%, advantageously of a maximum of 50%, particularly advantageously of a maximum of 30% and preferably of a maximum of 10% of a resistance value at temperatures below the threshold value, and wherein the value of the temperature-dependent specific resistance could, for example, assume a linear and / or exponential curve.The phrase "the control unit is designed to exploit" the temperature-dependent resistivity of the dielectric to determine the characteristic variable is to be understood in particular as meaning that the control unit is designed to determine a leakage current emerging from the heating element based on knowledge of a potential present at the measuring input in the heating operating state, and in particular to draw conclusions about a current resistance value of the dielectric from the determined leakage current emerging from the heating element, and advantageously to determine the characteristic variable based on knowledge of the profile of the temperature-dependent resistivity of the dielectric stored in the memory unit. This allows, in particular, an exact determination of the characteristic variable to be achieved. Furthermore, a cost-effective design can advantageously be achieved.

[0022] A particularly low effort in determining a network form applied to the heating connections can be achieved by a household appliance, in particular by a cooking appliance, with at least one household appliance heating device according to the invention.

[0023] The effort involved in determining a network configuration applied to the heating connections can be further reduced by a method for operating a domestic appliance heating device according to the invention, comprising at least one heating element having at least two heating connections, each of which is provided for connection to one of at least two supply connections of a supply network, comprising at least one first switching element connected between a first heating connection of the heating connections and a first supply connection of the supply connections, comprising at least one second switching element connected between a second heating connection of the heating connections and a second supply connection of the supply connections, and comprising a measuring unit having at least one measuring input to which a potential is applied in at least one heating operating state,wherein, in at least one network shape recognition operating state, a conduction path through the heating element is interrupted by means of the first switching element when the second switching element is closed, and a first potential applied to the measuring input is taken into account when determining a network shape applied to the heating element, wherein, in the at least one network shape recognition operating state, a conduction path through the heating element is interrupted by means of the second switching element when the first switching element is closed, and a second potential applied to the measuring input is taken into account when determining the network shape applied to the heating element, wherein, in the at least one network shape recognition operating state, the first and second potentials are compared with one another, and a difference between the first and second potentials is calculated.

[0024] The household appliance heating device is not intended to be limited to the application and embodiment described above. In particular, the household appliance heating device may have a number of individual elements, components, and units that differs from the number stated herein to fulfill a functionality described herein.

[0025] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0026] They show: Fig. 1 shows a domestic appliance with a domestic appliance heating device in a schematic perspective view, Fig. 2 shows a heating element, a dielectric, a sensor element, a further dielectric and a base element of the domestic appliance heating device in a schematic sectional view, Fig. 3 shows a schematic circuit diagram of the domestic appliance heating device in a network shape recognition operating state in a schematic view, Fig. 4 shows a schematic circuit diagram of the domestic appliance heating device in a heating operating state in a schematic view and Fig. 5 shows a diagram of a method for operating the domestic appliance heating device in a schematic view.

[0027] Fig. 1shows a household appliance 34 configured as a cooking appliance, with a household appliance heating device 10 configured as a cooking appliance heating device. For example, the household appliance 34 could be configured as a steamer and / or an induction oven and / or a stove and / or a kettle and / or a coffee machine and / or a toaster and / or a teppanyaki plate. In the present case, the household appliance 34 is configured as an oven.

[0028] The household appliance 34 has a housing 36, which forms an outer boundary, in particular, of the household appliance 34. On a front side of the housing 36 facing an operator in an installed state, the housing 36 has an appliance door 38.

[0029] The appliance door 38 provides access to a cooking chamber 40 located in the housing 36. The domestic appliance 34 has a muffle 42 that defines the cooking chamber 40. The muffle 42 forms a lateral boundary of the cooking chamber 40. To ventilate the cooking chamber 40, the domestic appliance 34 has a fan 44, which is arranged on a rear side facing away from the appliance door 38.

[0030] To heat the cooking chamber 40, the household appliance heating device 10 has a heating element 12. As an alternative to a design with a single heating element, the household appliance heating device could also comprise a different number of heating elements. For example, the household appliance heating device could have two heating elements. The heating elements could be arranged on an upper side and on an underside of the muffle. Alternatively, both heating elements could be arranged on the same side of the muffle. A first heating element of the heating elements could be arranged on the upper side and designed to generate upper heat. A second heating element of the heating elements could be arranged on the underside and designed to generate lower heat. Alternatively or additionally, heating elements arranged laterally on the muffle, in particular on side walls of the muffle, could be provided.For example, the heating element could be designed as an induction heating element and / or as a radiant heating element. In the present embodiment, the heating element 12 is designed as a resistance heating element.

[0031] For entering and / or selecting operating parameters, the household appliance heating device 10 has an operating unit 46 (cf. Fig. 1 ). For example, the operating parameter could include a cooking time and / or a cooking program and / or a heating power level. In particular, an operating parameter is a temperature, advantageously a target temperature, wherein the operating unit 46 is provided for entering and / or changing a value of a target temperature of the cooking chamber 40. The operating unit 46 is arranged on the front. The operating unit 46 has, in particular, a display unit and is advantageously provided for outputting a value.

[0032] The domestic appliance heating device 10 has a control unit 28, which executes actions and / or makes and / or changes settings depending on the operating parameters entered and / or selected via the operating unit 46. The control unit 28 is provided for controlling and regulating the heating element 12. The domestic appliance heating device 10 has a sensor (not shown) that is provided for detecting an actual temperature of the cooking chamber 40. Alternatively, it is conceivable for the domestic appliance heating device to have multiple sensors.

[0033] To supply the heating element 12 with energy, the heating element 12 has two heating connections 14, 16 (cf. Fig. 3 and 4). Each of the heating connections 14, 16 is provided for connection to a supply connection 18, 20 of a supply network. Alternatively, it is conceivable for the household appliance heating device to have a power supply provided for supplying the heating element with energy. The power supply could be a converter circuit, in particular with at least one DC / AC inverter. Furthermore, the power supply could have a connection to a supply network, in particular a power supply network.

[0034] A first heating connection 14 of the heating connections 14, 16 and a first supply connection 18 of the supply connections 18, 20 are electrically connected to one another. A second heating connection 16 of the heating connections 14, 16 and a second supply connection 20 of the supply connections 18, 20 are electrically connected to one another. The household appliance heating device 10 has a first switching element 22 and a second switching element 48. The first switching element 22 is connected between the first heating connection 14 of the heating connections 14, 16 and the first supply connection 18 of the supply connections 18, 20. A first connection of the first switching element 22 and the first supply connection 18 are electrically connected to one another. A second connection of the first switching element 22 and the first heating connection 14 are electrically connected to one another.

[0035] The second switching element 48 is connected between the second heating connection 16 and the second supply connection 20. A first connection of the second switching element 48 and the second heating connection 16 are electrically connected to one another. A second connection of the second switching element 48 and the second supply connection 20 are electrically connected to one another. The second switching element 48 represents a main switch of the household appliance 34. Each switching element 22, 48 comprises a relay. Alternatively, at least one of the switching elements could comprise, for example, a power semiconductor switch.

[0036] The household appliance heating device 10 has a measuring unit 24 having a measuring input 26. A potential is present at the measuring input 26, at least in one heating operating state. The measuring input 26 and the second heating connection 16 are electrically connected to one another. The measuring input 26 and the first connection of the second switching element 48 are electrically connected to one another. The measuring input 26 branches off at a connection point 50 from the electrical connection between the second heating connection 16 and the first connection of the second switching element 48. An electrical resistor 52 is connected between the measuring input 26 and the connection point 50. The resistor 52 has a resistance value of substantially 10 kΩ.

[0037] The measuring unit 24 has a measuring output 54. A first connection of the control unit 28 and the measuring output 54 are electrically connected to one another. The measuring unit 24 outputs a peak value of a potential applied to the measuring input 26 via the measuring output 54. The measuring unit 24 has a rectifier 56. The rectifier 56 has a rectifier input that is electrically connected to the measuring input 26. A measuring capacitor 58 branches off from an electrical connection between the measuring input 26 and the rectifier 56. The measuring capacitor 58 has a capacitance of essentially 100 nF. The measuring unit 24 has the measuring capacitor 58, which is provided for filtering out a high-frequency component. A first connection of the first measuring capacitor 58 is electrically connected to the connection between the measuring input 26 and the rectifier 56. A second terminal of the first measuring capacitor 58 is electrically connected to ground.Rectifier 56 is formed by an operational amplifier with a downstream diode. Alternatively, rectifier 56 could be formed by a bridge rectifier.

[0038] The measuring unit 24 has a further measuring capacitor 60, which is provided for smoothing a voltage output by the rectifier 56. The measuring capacitor 60 has a capacitance of substantially 10 nF. The further measuring capacitor 60 branches off at a measuring connection point 62 from a connection between the rectifier 56 and the measuring output 54. A first connection of the further measuring capacitor 60 and the measuring connection point 62 are electrically connected to one another. The rectifier 56 has a further rectifier input, which is electrically connected to the measuring connection point 62. A second connection of the further measuring capacitor 60 is electrically connected to ground.

[0039] If a potential is present at the measuring input 26, as is the case, for example, in the heating mode, the additional measuring capacitor 60 is charged via the rectifier 56. Since the first terminal of the additional measuring capacitor 60 is connected to the additional rectifier input via the measuring connection point 62, the additional measuring capacitor 60 is charged to a voltage value that corresponds to the value of the potential present at the measuring input 26. This value is then output to the control unit 28 via the measuring output 54. As a result, in a method for operating the domestic appliance heating device 10, the control unit 28 can determine a potential present at the measuring input 26 in the heating mode. The potential present at the measuring input 26 is variable in the heating mode and changes depending on a function of the heating element 12.

[0040] To monitor a function of the heating element 12 in the heating operating state, the household appliance heating device 10 has a sensor element 30 (cf. Fig. 2 ). In the heating operating state, the sensor element 30 is designed to detect a leakage current from the heating element 12. A leakage current escaping from the heating element 12 is undesirable, although it always occurs when the heating element 12 is heated. The leakage current escaping from the heating element 12 is negligibly small at temperatures below a threshold value. At temperatures above the threshold value, the leakage current increases sharply and indicates a malfunction of the heating element 12. The sensor element 30 and the measuring input 26 are electrically connected to one another. An electrical connection between the sensor element 30 and the measuring input 26 and an electrical connection between the connection point 50 and the measuring input 26 have a common contact point 64.

[0041] At least in the heating operating state, two parallel conduction paths 66, 68 lead from one of the supply connections 18, 20 to the measuring input 26. A first conduction path 66 of the conduction paths 66, 68 leads from one of the supply connections 18, 20 via the heating element 12 and the sensor element 30 to the measuring input 26. The first conduction path 66 of the conduction paths 66, 68 has a region between the heating element 12 and the sensor element 30 through which the leakage current flows. A second conduction path 68 of the conduction paths 66, 68 leads from one of the supply connections 18, 20 via the connection point 50 and the electrical resistor 52 to the measuring input 26. The electrical resistor 52 located in the second conduction path 68 is connected between the connection point 50 and the contact point 64.

[0042] A capacitance and an ohmic resistance, specifically a capacitor 70, a first resistor 72, and a second resistor 74, are connected in series between the sensor element 30 and the contact point 64. The capacitor 70 has a capacitance of substantially 100 nF. The first resistor 72 has a resistance value in a range from 30 kΩ to 50 kΩ, specifically substantially 33 kΩ. The second resistor 74 has a resistance value in a range from 30 kΩ to 50 kΩ, specifically substantially 33 kΩ. The sensor element 30 and a first terminal of the capacitor 70 are electrically connected to one another. A capacitor 76 branches off from the connection between the sensor element 30 and the first terminal of the capacitor 70. A first terminal of the capacitor 76 and the connection between the sensor element 30 and the first terminal of the capacitor 70 are electrically connected to one another.A second terminal of capacitor 76 is electrically connected to ground. The series circuit comprising capacitor 70, first resistor 72, and second resistor 74 has a resistivity substantially ten times greater than the electrical resistance 52 located in second conduction path 68.

[0043] If one of the switching elements 22, 48 is closed and another of the switching elements 22, 48 is open, a potential with a value dependent on the network type connected to the heating element 12 is present at the measuring input 26. Depending on the country in which the household appliance 34 is used, different network types are connected to the heating element 12. Since the potential applied to the measuring input 26 changes depending on the network type connected to the heating element 12, the network type connected to the heating element 12 should be known for precise detection of the leakage current emerging from the heating element 12 in the heating operating state.

[0044] The following incomplete table provides some examples of network shapes for different countries: country Three-phase alternating current Single-phase alternating current Germany 400 V 230 V Switzerland 400 V 230 V Great Britain 415 V 240 V Australia 415 V 240 V Japan 200 V 100 V Philippines 380 V 220 V

[0045] In a method for operating the domestic appliance heating device 10, in particular when the domestic appliance 34 is activated for the first time, a network form recognition operating state is started in a first method step 82 (cf. Fig. 5 ). The control unit 28 starts the network type detection operating state automatically. In the network type detection operating state, the control unit 28 interrupts a conduction path through the heating element 12 in a first measuring step 84 by means of the first switching element 22 while the second switching element 48 is closed. In the first measuring step 84, a first potential is applied to the measuring input 26. In the network type detection operating state, the control unit 28 takes into account the first potential applied to the measuring input 26 when determining a network type applied to the heating element 12. The control unit 28 stores the first potential in the network type detection operating state in a memory unit of the control unit 28.

[0046] In a second measuring step 86, the control unit 28 interrupts a conduction path through the heating element 12 in the network shape detection operating state by means of the second switching element 48 while the first switching element 22 is closed. In the second measuring step 86, a second potential is present at the measuring input 26. In the network shape detection operating state, the control unit 28 takes the second potential present at the measuring input 26 into account when determining a network shape present at the heating element 12. The control unit 28 stores the second potential in the network shape detection operating state in the memory unit of the control unit 28.

[0047] In the network shape recognition operating state, the control unit 28 determines a magnitude of a difference between the first potential and the second potential in a first test step 88. In the network shape recognition operating state, the control unit 28 compares the magnitude of the difference between the first potential and the second potential with a differential reference potential stored in the memory unit of the control unit 28. In the present exemplary embodiment, the differential reference potential is essentially 30 mV.

[0048] In the event that the amount of the difference between the first potential and the second potential is greater than the difference reference potential stored in the memory unit of the control unit, the control unit 28 concludes in the network type detection operating state that a neutral conductor is present at one of the supply connections 18, 20. In the network type detection operating state, the control unit 28 detects the presence of a neutral conductor at one of the supply connections 18, 20 based on the potentials present at the measuring input 26. In the case of a neutral conductor being present at one of the supply connections 18, 20, the first potential and the second potential differ significantly from one another.

[0049] Depending on the plug-in direction of a device plug in a power supply socket, the neutral and phase conductors are reversed. Since the potential at the measuring input 26 changes depending on the polarity applied to the heating element 12, a clear polarity must be ensured for precise detection of the leakage current escaping from the heating element 12 in the heating mode.

[0050] If the control unit 28 detects the presence of a neutral conductor at one of the supply terminals 18, 20, the control unit 28 initiates a polarity detection operating state in a polarity detection step 90. In the polarity detection operating state, the control unit 28 determines the supply terminal 18, 20 to which the neutral conductor is connected.

[0051] In the polarity detection operating state, the control unit 28 compares the first potential with a lower reference potential stored in the memory unit of the control unit 28. In the polarity detection operating state, if the first potential is lower than the lower reference potential, the control unit 28 detects the presence of a neutral conductor at the first heating terminal 14. In the polarity detection operating state, if the first potential is lower than the lower reference potential, the control unit 28 detects the presence of a phase conductor at the second heating terminal 16. The lower reference potential in the present embodiment is essentially 30 mV.

[0052] In the network type detection operating state, the control unit 28 determines a shutdown threshold for the heating element 12 in the polarity detection step 90 based on the determined network type. In the network type detection operating state, the control unit 28 retrieves a shutdown threshold associated with the determined network type from the memory unit of the control unit 28. If a neutral conductor is present at the first heating terminal 14, the determined shutdown threshold for the heating element 12 in the present exemplary embodiment is essentially 600 mV.

[0053] In the polarity detection operating state, the control unit 28 compares the first potential with an upper reference potential stored in the memory unit of the control unit 28. In the polarity detection operating state, if the first potential is greater than the upper reference potential, the control unit 28 detects the presence of a phase conductor at the first heating terminal 14. In the polarity detection operating state, if the first potential is greater than the upper reference potential, the control unit 28 detects the presence of a neutral conductor at the second heating terminal 16. In the present embodiment, the upper reference potential is essentially 500 mV.

[0054] In the network type detection operating state, the control unit 28 determines a shutdown threshold for the heating element 12 in the polarity detection step 90 based on the determined network type. In the network type detection operating state, the control unit 28 retrieves a shutdown threshold associated with the determined network type from the memory unit of the control unit 28. If a neutral conductor is present at the second heating terminal 16, the determined shutdown threshold for the heating element 12 in the present exemplary embodiment is essentially 1200 mV.

[0055] In the event that the magnitude of the difference between the first potential and the second potential is smaller than the differential reference potential stored in the memory unit of the control unit 28, the control unit 28 concludes that there is no neutral conductor at the supply terminals 18, 20.

[0056] If the difference between the first potential and the second potential is smaller than the difference reference potential stored in the memory unit of the control unit 28, the control unit 28 checks the validity of the first potential and the second potential in a second check step 92 in the network shape recognition operating state. In the network shape recognition operating state, the control unit 28 compares the first potential and the second potential with a validity range stored in the memory unit of the control unit 28.

[0057] If the first potential and the second potential are each within the validity range, the control unit 28, in the network configuration detection operating state, detects, in a conclusion step 94, the presence of phase conductors at the supply terminals 18, 20 based on the potentials present at the measuring input 26. In the present exemplary embodiment, the validity range is essentially from 300 mV to 420 mV. The validity range is relevant for the presence of phase conductors at the supply terminals 18, 20. The validity range is irrelevant for the presence of a neutral conductor at one of the supply terminals 18, 20. If phase conductors are present at the supply terminals 18, 20, the first potential and the second potential differ only slightly from one another.

[0058] In the network type detection operating state, the control unit 28 determines a shutdown threshold for the heating element 12 in the inference step 94 based on the determined network type. In the network type detection operating state, the control unit 28 extracts a shutdown threshold associated with the determined network type from the memory unit of the control unit 28. In the case of phase conductors being connected to the supply terminals 18, 20, the determined shutdown threshold for the heating element 12 in the present exemplary embodiment is essentially 900 mV.

[0059] In the event that at least one of the potentials lies outside the validity range, the control unit 28 refrains from using the potentials in the network type detection operating state when detecting the presence of phase conductors at the supply terminals 18, 20. In the network type detection operating state, in the event that at least one of the potentials lies outside the validity range, the control unit 28 detects a device defect in an error detection step 96 based on the potentials present at the measuring input.

[0060] In the event that at least one of the potentials lies outside the validity range, the control unit 28 issues a warning, in particular to an operator, via the display unit of the operating unit 46 in the error detection step 96. In this case, the control unit 28 detects an existing hardware error, which could be caused, for example, by the heating element 12 and / or by one of the switching elements 22, 48, and / or a software error.

[0061] The heating element 12 and the sensor element 30 together form a capacitor (cf. Fig. 2 ). The sensor element 30 and the heating element 12 are arranged adjacent in an assembled state. The heating element 12 and the sensor element 30 are each formed as a layer. The household appliance heating device 10 has a base element 78, on which the heating element 12 and the sensor element 30 are applied in the assembled state. The base element 78 is grounded (cf. Fig. 3 ).

[0062] The household appliance heating device 10 has a dielectric 32 which is arranged between the heating element 12 and the sensor element 30 (cf. Fig. 2). The dielectric 32 has a temperature-dependent specific resistance. Below a threshold value, the temperature-dependent specific resistance of the dielectric 32 changes only slightly. At temperatures of the heating element 12 below the threshold value, such as in the network shape recognition operating state and / or in the polarity detection operating state, the dielectric 32 at least substantially blocks a current flow between the heating element 12 and the sensor element 30. The temperature-dependent specific resistance of the dielectric 32 decreases with increasing temperature at temperatures above the threshold value. A value of the threshold value is selected in a range of incipient overheating of the heating element 12. In the present exemplary embodiment, the threshold value is substantially 300°C.

[0063] The sensor element 30 and the base element 78 together form a capacitor. The household appliance heating device 10 has a further dielectric 80 arranged between the sensor element 30 and the base element 78. The further dielectric 80 has a substantially temperature-independent resistivity that changes only insignificantly with increasing temperature. Regardless of the operating state, the further dielectric 80 at least substantially blocks a current flow between the sensor element 30 and the base element 78.

[0064] If an operator specifies a heating output for the heating element 12 using the control unit 46, the control unit 28 starts the heating operating state. To start the heating operating state, the control unit 28 closes the switching element 22 and the second switching element 48 (see Fig. 4). At temperatures of the heating element 12 below the threshold value, the dielectric 32, by means of the specific resistance of the dielectric 32, at least substantially prevents a leakage current escaping from the heating element 12.

[0065] If the heating element 12 reaches temperatures above the threshold value, a leakage current that is significantly different from zero escapes from the heating element 12. The leakage current exiting the heating element 12 assumes different values ​​depending on the temperature of the heating element 12. The leakage current exiting the heating element 12 assumes higher values ​​for higher temperatures of the heating element 12.

[0066] In the heating operating state, the control unit 28 determines a parameter dependent on the leakage current of the heating element 12. The parameter comprises a temperature of the heating element 12. In the heating operating state, the control unit 28 uses the parameter to check whether the heating element 12 is overheating. In the heating operating state, the control unit 28 uses the temperature-dependent resistivity of the dielectric 32 to determine the parameter. An expected value of the leakage current as a function of a temperature of the heating element 12 is stored in the memory unit of the control unit 28. In the heating operating state, the control unit 28 compares the determined value of the leakage current, which the control unit 28 determines from the potential applied to the measuring input 26, with the leakage current values ​​stored in the memory unit. From this, the control unit 28 determines the parameter in the heating operating state.

[0067] When determining the characteristic variable dependent on the leakage current of the heating element 12, the control unit 28 takes into account the network configuration applied to the heating element 12 in the heating operating state. In the heating operating state, the control unit 28 selects different shutdown limit values ​​stored in the memory unit of the control unit 28, depending on the network configuration applied to the heating element 12, for comparison with the value of the potential applied to the measuring input 26 transmitted from the measuring unit 24 to the control unit 28.

[0068] If the leakage current emerging from the heating element 12 assumes a value above the switch-off limit value stored in the memory unit and determined by the control unit 28, the control unit 28 deactivates the heating element 12 in the heating operating state, in particular by opening the switching element 22 and / or the second switching element 48. Alternatively or additionally, the control unit 28 issues a warning in the heating operating state, in particular to an operator, should the leakage current emerging from the heating element 12 assume a value above the switch-off limit value stored in the memory unit and determined by the control unit 28.

[0069] In the heating operating state, a value of the potential applied to the measuring input 26 depends on a heated surface of the heating element 12. The potential applied to the measuring input 26 assumes different values ​​in the heating operating state depending on the number of activated heating circuits of the heating element 12. In the heating operating state, the control unit 28 detects a number of activated heating circuits of the heating element 12 using the potential applied to the measuring input 26. In the heating operating state, the control unit 28 detects defective heating circuits of the heating element 12 based on the potential applied to the measuring input 26. In the case of one and / or more defective heating circuits of the heating element 12, the control unit 28 issues a warning, in particular to an operator, via the display unit in the heating operating state and / or deactivates the heating element 12, in particular by opening the first switching element 22 and / or the second switching element 48.

[0070] If the heating element 12 is used to heat water, limescale residue can build up on the heating element 12. Limescale residue on the heating element 12 has an insulating effect and, in the heating mode, reduces maximum heat transfer from the heating element 12 to the food being heated by the heating element 12, such as water. In the heating mode, limescale residue on the heating element 12 results in an increase in the temperature of the heating element 12. In extreme cases, the heating element 12 could overheat and be destroyed, particularly due to limescale residue on the heating element 12.

[0071] In the heating operating state, a value of the potential applied to the measuring input 26 depends on the extent of contamination of the heating element 12. The contamination could, for example, be in the form of calcification. The potential applied to the measuring input 26 assumes different values ​​in the heating operating state depending on the extent of contamination of the heating element 12. In the heating operating state, the control unit 28 detects the presence of contamination of the heating element 12 by means of the potential applied to the measuring input 26. In the heating operating state, the control unit 28 outputs information, in particular to an operator, about the presence of contamination of the heating element 12 via the display unit. Alternatively or additionally, the control unit 28 deactivates the heating element 12 in the heating operating state, in particular by opening the first switching element 22 and / or the second switching element 48.

[0072] In this way, in particular, emergency operation of the heating element 12 can be achieved, in particular in the case of one and / or more defective heating circuits of the heating element 12 and / or in the case of existing contamination of the heating element 12. Furthermore, in the case of overheating of the heating element 12, measures can be taken to protect against overheating of the heating element 12, in particular by actions carried out by the control unit 28.

[0073] Alternatively, the base element could be omitted. Designs with different numbers of heating elements and / or sensor elements are also conceivable. Reference symbol

[0074] 10Household appliance heating device 12Heating element 14First heating connection 16Second heating connection 18First supply connection 20Second supply connection 22Switching element 24Measuring unit 26Measuring input 28Control unit 30Sensor element 32Dielectric 34Household appliance 36Housing 38Appliance door 40Cooking chamber 42Muffle 44Fan 46Control unit 48Further switching element 50Connection point 52Resistor 54Measuring output 56Rectifier 58Measuring capacitor 60Further measuring capacitor 62Measuring connection point 64Contact point 66First conduction path 68Second conduction path 70Capacitor 72First resistor 74Second resistor 76Capacitor 78Base element 80Further dielectric 82First process step 84First Measurement step 86Second measurement step 88First test step 90Polarity detection step 92Second test step 94Conclusion step 96Fault detection step

Claims

1. Household appliance heating apparatus with at least one heating element (12), which has at least two heating connections (14, 16), which are each provided for connection to one of at least two supply connections (18, 20) of a supply network, with at least one first switching element (22), which is connected between a first heating connection (14) of the heating connections (14, 16) and a first supply connection (18) of the supply connections (18, 20), with at least one second switching element (48), which is connected between a second heating connection (16) of the heating connections (14, 16) and a second supply connection (20) of the supply connections (18, 20), and with a measuring unit (24), which has at least one measuring input (26), at which a potential is present in at least one heating operating state, characterised by a control unit (28), which is designed to interrupt a conduction path through the heating element (12) by means of the first switching element (22) with the second switching element (48) closed in at least one network form recognition operating state and to take into account a first potential present at the measuring input (26) when determining a network form present at the heating element (12), wherein the control unit (28) is designed to interrupt a conduction path through the heating element (12) by means of the second switching element (48) with the first switching element (22) closed in the at least one network form recognition operating state and to take into account a second potential present at the measuring input (26) when determining the network form present at the heating element (12), wherein the control unit (28) is designed to compare the first and the second potential with one another in the at least one network form recognition operating state and to calculate a difference between the first and the second potential.

2. Household appliance heating apparatus according to claim 1, characterised in that the control unit (28) is designed to recognise a presence of a zero conductor at one of the supply connections (18, 20) from the potentials present at the measuring input (26) in the network form recognition operating state.

3. Household appliance heating apparatus according to claim 2, characterised in that the control unit (28) is designed to determine the supply connection (18, 20) at which the zero conductor is present in at least one polarity detection operating state.

4. Household appliance heating apparatus according to one of the preceding claims, characterised in that the control unit (28) is designed to recognise a presence of phase conductors at the supply connections (18, 20) from the potentials present at the measuring input (26) in the network form recognition operating state.

5. Household appliance heating apparatus according to one of the preceding claims, characterised in that the control unit (28) is designed to recognise at least one appliance defect from the potentials present at the measuring input (26) in the network form recognition operating state.

6. Household appliance heating apparatus according to one of the preceding claims, characterised in that the control unit (28) is designed to determine a trip limit value for the heating element (12) from the determined network form in the network form recognition operating state.

7. Household appliance heating apparatus according to one of the preceding claims, characterised by at least one sensor element (30), which is designed to detect a leakage current from the heating element (12) in the heating operating state.

8. Household appliance heating apparatus according to claim 7, characterised in that the control unit (28) is designed to determine at least one characteristic variable that is a function of the leakage current from the heating element (12) in the heating operating state.

9. Household appliance heating apparatus according to claim 8, characterised in that the control unit (28) is designed to take into account the network form present at the heating element (12) when determining the characteristic variable that is a function of the leakage current from the heating element (12) in the heating operating state.

10. Household appliance with at least one household appliance heating apparatus according to one of the preceding claims.

11. Method for operating a household appliance heating apparatus with at least one heating element (12), which has at least two heating connections (14, 16), which are each provided for connection to one of at least two supply connections (18, 20) of a supply network, with at least one first switching element (22), which is connected between a first heating connection (14) of the heating connections (14, 16) and a first supply connection (18) of the supply connections (18, 20), with at least one second switching element (48), which is connected between a second heating connection (16) of the heating connections (14, 16) and a second supply connection (20) of the supply connections (18, 20), and with a measuring unit (24), which has at least one measuring input (26), at which a potential is present in at least one heating operating state, characterised in that a conduction path through the heating element (12) is interrupted by means of the first switching element (22) with the second switching element (48) closed in at least one network form recognition operating state and a first potential present at the measuring input (26) is taken into account when determining a network form present at the heating element (12), wherein a conduction path through the heating element (12) is interrupted by means of the second switching element (48) with the first switching element (22) closed in the at least one network form recognition operating state and a second potential present at the measuring input (26) is taken into account when determining the network form present at the heating element (12), wherein the first and the second potential are compared with one another in the at least one network form recognition operating state and a difference between the first and the second potential is calculated.