EP3031296B1 - Cooking equipement and method to control the said equipement - Google Patents

Description

The present invention relates to a cooking device and a method for operating such a cooking device.

In the prior art cooking appliances have become known that offer automatic functions. A prerequisite for such an automatic operation of a cooking device is sometimes a detection of various parameters that are characteristic of the cooking process, such. B. the temperature of the food container and in particular the pot bottom. Depending on the detected parameters then the automatic function and in particular the heating power of the cooking device are controlled. The heat source must be controlled so that z. B. an undesirable overheating of the food is avoided. Therefore, the reliability or accuracy of the detected parameters is crucial to the functionality of the automatic function.

In the prior art, for example, devices have become known for determining temperatures during cooking and cooking processes, which determine the temperature on the underside of a food container without contact. This is how z. B. the WO 2008/148 529 A1 a heat sensor below a hob plate, which detects the radiated heat radiation and determines therefrom the temperature of the Gargutbehälters or the pot bottom.

Furthermore, the documents show JP 2004 095 313 A and JP 2009181 963 A in each case a cooking device, with at least one hob and with at least one heater for heating at least one cooking area provided and at least one sensor device for detecting at least one characteristic size for temperatures of the cooking area and at least one control device, wherein the control device, the heater at least in dependence of the sensor device detected size controls.

The known devices and methods are with regard to a use in automatic functions of cooking appliances, such. As a stove, but still capable of improvement. For example, an automatic boil-up of milk without overcooking the milk places very high demands on the corresponding devices and methods with regard to the reproducibility and the accuracy. An important step is z. B. the calculation of the temperature of the pot bottom from the heat radiation detected by the heat sensors. For this purpose, the output signals of the heat sensors must be prepared and evaluated in accordance with the rule.

It is therefore the object of the present invention to provide a cooking device and a method which improve the reliability of temperature determinations in cooking operations.

This object is achieved by a method having the features of claim 1 and a cooking device having the features of claim 11. Preferred features are the subject of the dependent claims. Further advantages and features will become apparent from the general description of the invention and the description of the embodiments.

The inventive method is suitable for operating a cooking device with at least one hob and at least one heating device for heating at least one cooking area. At least one sensor device is provided for detecting at least one characteristic variable for temperatures of the cooking area. At least one control device controls the heating device as a function of the size detected by the sensor device. In this case, at least one output signal of the sensor device is adjusted by at least one adjustable offset and then amplified.

The method according to the invention has many advantages. A significant advantage is that the output signal is adjusted by the adjustable offset and then amplified. The adjustable offset allows the output signal to be adjusted before it is amplified. This has the advantage that with a corresponding adjustment of the offset overdriving the amplifier is prevented. It is also particularly advantageous that the output signal can be displaced by the offset in a range which allows a gain with an optimum resolution of the signal. A complex adaptation of the gain or of an amplifier to different signals or different signal ranges can be avoided.

Preferably, the sensor device detects heat radiation from the cooking area and in particular a cooking vessel set up in the cooking area. For this purpose, the sensor device can have at least one thermopile, also called thermopile, or at least one thermocouple. The output signal is then the voltage of such a sensor.

In particular, in the adaptation, the output signal of the sensor device is shifted. In this case, the offset shifts the output signal of the sensor device. This adjusted signal can then be supplied to the amplifier device as an input signal. The output signal of the sensor device can be obtained directly or indirectly from the sensor device. For example, the output signal can be modulated and / or preamplified. The adapted output signal of the sensor device can then be amplified by at least one amplifier device, for example by an operational amplifier. In this case, the shifted output signal is then in particular an input signal for the amplifier device.

Preferably, the offset is at least a predetermined voltage. The offset can also be a so-called offset or an offset voltage.

The offset is preferably set by a reference voltage. By the height of the reference voltage while the height of the differential voltage, which then enters as an input signal in an amplifier device, can be adjusted. In this case, the difference voltage results in particular from the difference between the voltage of the output signal of the sensor device and the respectively set reference voltage. The reference voltage may be the reference voltage of a subtraction device connected between the sensor device and the amplifier device or may be the reference voltage of an amplifier device connected downstream of the sensor device and in particular of a differential amplifier.

The offset is preferably set as a function of the voltage of the output signal of the sensor device. This is particularly advantageous because the offset can be optimally adjusted to the respective output signal, even if the output signal changes over time. As an alternative or in addition, the already amplified output signal, that is to say the output signal of the amplifier device, termed the amplifier signal for short, is particularly preferably considered, and the offset is adjusted by virtue of its voltage and / or at least one other characteristic with which the output signal of the sensor device is adjusted. According to the invention, the offset is set as a function of a calibration of the sensor device, and a different offset is set for a calibration than for the acquisition of measured variables for temperature determination. This has the advantage that the offset can be adjusted accordingly if there is a changed output signal during a calibration.

It is possible for at least one radiation source to emit electromagnetic radiation at least temporarily to calibrate the sensor device. In this case, at least part of the radiation emitted by the radiation source is received again by the sensor device. A calibration value is then derived with the output signal output by the sensor device and used to calibrate the sensor device. The output signal provided for deriving the calibration value is preferred by at least one adjusted offset adjusted. The offset can be downsampled, increased or decreased to derive the calibration value. The calibration can z. B. be a reflection measurement, by means of which the reflection or emission properties of a cooking vessel are determined in the cooking area.

The offset is preferably adjusted prior to calibration. Also possible is a setting at the beginning and / or during calibration. The adjustment or at least one further adjustment can also be made after the calibration. The adjustment of the offset can be z. B. done depending on the switching of the radiation source.

It is preferred that the output signal provided for deriving the calibration value is adjusted by a different offset than the output signal upon detection of at least one characteristic variable for temperatures of the cooking region. It can z. B. different predetermined voltages are applied, depending on whether to calibrate or the temperature of a pot to be determined.

The offset for the output signal for temperature determination and / or for calibration can also be adjusted depending on the particular cooking situation, for. B. if the cooking vessel is still cold or already very hot. In this case, the temperature of a support means for parking the cooking vessel, z. As a glass ceramic plate, are taken into account.

The offset is preferably set upon reaching a predetermined value of the output signal of the sensor device and / or the output signal of the amplifier device. The adjustment on the basis of a value of the output signal of the sensor device takes place, in particular, if the output signal can be expected to no longer lie in a linear or optimum range of the amplifier device in the case of a subsequent amplification. It is also possible that the offset is adjusted based on a value of the output signal of the amplifier device, e.g. The amplifier signal is no longer linear or coming from the sensor device input signal signal can no longer be amplified distortion-free by the amplifier device.

In this case, the offset can be adjusted automatically when the output signal and / or the amplifier signal reach a certain threshold. For example, from a certain voltage of the output signal, the offset can be adjusted so that the output signal is then at a suitable or lower voltage level. Such an adjustment can also be made several times. The respective offset is in particular an integer multiple of a basic offset and preferably the maximum permissible input voltage, which does not lead to overdriving the amplifier.

For example, the output signal of the sensor device can be adjusted from a predetermined threshold value with a first offset. If the output signal adjusted by the first offset again reaches a threshold value, it is then adjusted by a second offset. Such an adaptation can follow one another as often as desired. The advantage of such an offset adjustment is that the shifted output signal can be optimally amplified. The corresponding amplifier signal is then in a linear range, which can be evaluated particularly reliably, so that an accurate and reproducible calculation of the temperature from the output signal is possible.

It is also possible that the offset is set if the output signal leads to overdriving the amplifier device used for amplification and / or would lead. Alternatively or in addition to the adjustment of the offset and the amplifier device can be adjusted, for. B. can be switched to another amplifier stage.

It is also possible to adjust the voltage of the output signal by at least a predetermined voltage as an offset. Such a voltage is in particular the reference voltage. There are also two or more predetermined voltages possible. In this case, the offset is adjusted in particular by at least one voltage from a group of predetermined voltages when at least one predetermined value of the output signal is reached. Preferably, upon reaching an amplifier signal that is at least partially non-linear over time, the output signal is adjusted.

Preferably, a predetermined gain is set in response to the output signal. Also, depending on the set offset, a predetermined gain can be set. The gain is preferably set so that a favorable evaluation of the amplifier signal is possible.

The cooking device according to the invention has at least one hob and at least one heating device provided for heating at least one cooking area. At least one sensor device is provided for detecting at least one characteristic variable for temperatures of the cooking area. Furthermore, at least one control device is provided for controlling the heating device as a function of the variable detected by the sensor device. In this case, at least one adjustable offset device is provided for setting an offset in order to shift an output signal of the sensor device with the offset. In addition, at least one amplifier device is provided for amplifying the shifted output signal.

The cooking device according to the invention is particularly advantageous since an adjustable offset device is provided. The offset device can be the output signal of the sensor device, for. As a voltage, move in a range that can be amplified by the amplifier device in an optimally evaluable signal. In addition, the offset device is adjustable, so that the offset can be adjusted so that the amplifier device does not overdrive. This has the considerable advantage that it is not necessary to set the gain itself or to install a multi-stage amplifier device. This makes it possible to dispense with a complex calibration of the amplifier device for several areas.

The amplifier device may have at least two amplifier stages. In this case, a predetermined amplifier stage is preferably set as a function of the output signal and / or the set offset. As a result, a different gain possible, for. B. depending on whether an output signal with a lower or higher voltage is applied. The amplifier stages are preferably already factory calibrated for at least one signal range to be amplified.

For calibrating the sensor device, at least one radiation source for emitting electromagnetic radiation is preferably provided. The sensor device is suitable and designed to receive at least a portion of the radiation emitted by the radiation source again and output as a signal. At least one control device is suitable and designed to derive a calibration value for calibrating the sensor device with the signal output by the sensor device. In this case, the offset device is suitable and designed to adapt the output signal provided for deriving the calibration value by an adjustable offset. The amplifier device is particularly suitable and designed to amplify the adjusted output signal.

Further advantages and features of the invention will become apparent from the embodiments, which will be explained below with reference to the accompanying figures.

Figur 1

eine schematische Darstellung einer erfindungsgemäßen Kocheinrichtung an einem Gargerät in perspektivischer Ansicht;

Figur 2

eine schematisierte Kocheinrichtung in einer geschnittenen Ansicht;

Figur 3

eine weitere Kocheinrichtung in einer schematischen, geschnittenen Ansicht;

Figur 4

eine andere Kocheinrichtung in einer einer schematischen, geschnittenen Ansicht;

Figur 5

skizzierte Verläufe verschiedener Ausgangssignale der Sensoreinheit;

Figur 6

eine stark schematisierte Verstärkereinrichtung und eine Versatzeinrichtung; und

Figur 7

eine Skizze eines Verlaufs eines Verstärkersignals.

In the figures show:

FIG. 1

a schematic representation of a cooking device according to the invention on a cooking appliance in a perspective view;

FIG. 2

a schematic cooking device in a sectional view;

FIG. 3

another cooking device in a schematic, sectional view;

FIG. 4

another cooking device in a schematic, sectional view;

FIG. 5

sketched gradients of various output signals of the sensor unit;

FIG. 6

a highly schematic amplifier means and a shifter; and

FIG. 7

a sketch of a course of an amplifier signal.

The FIG. 1 shows a cooking device 1 according to the invention, which is designed here as part of a cooking appliance 100. The cooking appliance 1 or the cooking appliance 100 can be designed both as a built-in appliance and as a self-sufficient cooking appliance 1 or stand-alone cooking appliance 100.

The cooking device 1 here comprises a hob 11 with four cooking zones 21. Each of the cooking zones 21 here has at least one heatable cooking area 31 for cooking food. In order to heat the cooking area 31, a heating device 2, not shown here, is provided in total for each hotplate 21. The heating devices 2 are designed as induction heating sources and each have an induction device 12 for this purpose.

But it is also possible that a cooking area 31 is not associated with any particular cooking area 21, but represents any location on the hob 11. In this case, the cooking area 31 may have a plurality of induction devices 12 and in particular a plurality of induction coils and be formed as part of a so-called full-surface induction unit. For example, in such a cooking area 31 simply a pot can be placed anywhere on the hob 11, wherein during cooking only the corresponding induction coils are driven in the pot or are active. Other types of heaters 2 are also possible, such. As gas, infrared or Widerstandsheizquellen.

The cooking device 1 can be operated here via the operating devices 105 of the cooking appliance 100. The cooking device 1 can also be designed as a self-sufficient cooking device 1 with its own operating and control device. Also possible is an operation via a touch-sensitive surface or a touch screen or remotely via a computer, a smartphone or the like.

The cooking appliance 100 is here designed as a stove with a cooking chamber 103, which can be closed by a cooking chamber door 104. The cooking chamber 103 can be heated by various heat sources, such as a Umluftheizquelle. Other heating sources, such as a top heat radiator and a bottom heat radiator and a microwave heat source or a vapor source and the like may be provided.

Furthermore, the cooking device 1 on a sensor device 3, not shown here, which is suitable for detecting at least one characteristic size for temperatures of the cooking area (31). For example, the sensor device 3 can detect a variable, via which the temperature of a pot can be determined, which is turned off in the cooking area 31. In this case, each cooking area 31 and / or each cooking place 21 may be assigned a sensor device 3. It is also possible that several cooking areas 31 and / or cooking zones 21 are provided, but not all of which have a sensor device 3.

The cooking device 1 is preferably designed for an automatic cooking operation and has various automatic functions. For example, with the automatic function, a soup can be boiled briefly and then kept warm, without a user having to supervise the cooking process or set a heating level. For this he sets the pot with the soup on a hob 21 and selects the corresponding automatic function via the operating device 105, here z. As a boil with subsequent keeping warm at 60 ° C or 70 ° C or the like.

When using the automatic function, the temperature of the pot bottom is determined by means of the sensor device 3 during the cooking process. Depending on the measured values, a control device 106 adjusts the heating power of the heating device 2 accordingly. When the desired temperature is reached or when the soup boils, the heating power is reduced. For example, it is also possible by the automatic function to perform a longer cooking process at one or more different desired temperatures, for. B. to slowly let rice pudding draw.

In the FIG. 2 a cooking device 1 is shown in a sectional side view very schematic. The cooking device 1 here has a carrier device 5 designed as a glass ceramic plate 15. The glass ceramic plate 15 may in particular be designed as a ceramic hob or the like or at least comprise such. Also possible are other types of support means 5. On the glass ceramic plate 15 is here a cookware or food containers 200, such as a pot or a pan, in which food or food can be cooked.

Below the glass ceramic plate 15, an induction device 12 for heating the cooking area 31 is attached. The induction device 12 is here annular and has in the middle a recess in which the sensor device 3 is mounted. Such an arrangement of the sensor device 3 has the advantage that it is still in the detection range 83 of the sensor device even if the food container 200 is not centered on the cooking point 21.

Furthermore, a sensor device 3 is provided which detects heat radiation in a detection region 83 here. The detection area 83 is provided in the installed position of the cooking device 1 above the sensor device 3 and extends upward through the glass ceramic plate 15 to the food container 200 and beyond, if there is no food container 200 is placed there.

The detected thermal radiation is converted by the sensor device 3 into electrical voltage. For this purpose, the sensor device 3 has one or more sensor units 13, 23, not shown here, which supply this voltage as a function of the detected thermal radiation as an output signal 130 (cf. FIG. 6 ) output. So that it can be evaluated for temperature determination, the output signal 130 is amplified accordingly. For this purpose, an amplifier device 620 is provided here. Since the output signal 130 may vary due to different temperature conditions in the cooking region 31, signal values can occur that are no longer in the linear region of the amplifier device 620. The amplifier overrides then and a reliable temperature determination is difficult.

Therefore, a displacement device 610 is provided here, which causes the output signal 130 coming from the sensor unit 13 to be shifted into a region which does not lead to overdriving of the amplifier device 620. As a result, the amplifier device 620 can be supplied with an optimally amplifiable signal even in very different cooking situations. A change in the gain is therefore not necessary. Since a change in the gain would require a complex calibration for the corresponding areas, thus costs can be saved.

The FIG. 3 shows a schematic cooking device 1 in a sectional side view. The cooking device 1 has a glass ceramic plate 15, below which the induction device 12 and the sensor device 3 are mounted.

The sensor device 3 has a first sensor unit 13 and another sensor unit 23. Both sensor units 13, 23 are suitable for non-contact detection of thermal radiation and designed as a thermopile or thermopile. The sensor units 13, 23 are each equipped with a filter device 43, 53 and provided for detecting heat radiation emanating from the cooking area 31. The thermal radiation emanates, for example, from the bottom of a food container 200, penetrates the glass ceramic plate 15 and reaches the sensor units 13, 23. The sensor device 3 is advantageously mounted directly underneath the glass ceramic plate 15 in order to maximize the proportion of heat radiation emanating from the cooking region 31 without great losses to be able to capture. Thus, the sensor units 13, 23 are provided close to below the glass ceramic plate 15.

Furthermore, a magnetic shielding device 4 is provided, which consists of a ferrite body 14 here. The ferrite body 14 is essentially designed here as a hollow cylinder and surrounds the sensor units 13, 23 in an annular manner. The magnetic shielding device 4 shields the sensor device 3 against electromagnetic interactions and in particular against the electromagnetic field of the induction device 12. Without such shielding, the magnetic field generated by induction device 12 during operation could undesirably heat parts of sensor device 3 as well, resulting in unreliable temperature sensing and inferior measurement accuracy. The magnetic shielding device 4 thus considerably improves the accuracy and reproducibility of the temperature detection.

The magnetic shielding device 4 may also consist at least in part of at least one at least partially magnetic material and an at least partially electrically non-conductive material. The magnetic material and the electrically non-conductive material may be arranged alternately and in layers. Also possible are other materials or materials which have at least partially magnetic properties and also have electrically insulating properties or at least low electrical conductivity.

The sensor device 3 has at least one optical screen device 7, which is provided to shield radiation influences and in particular heat radiation, which act on the sensor units 13, 23 from outside the detection zone 83. For this purpose, the optical shield device 7 is designed here as a tube or a cylinder 17, wherein the cylinder 17 is hollow and the sensor units 13, 23 surrounds approximately annular. The cylinder 17 is made of stainless steel here. This has the advantage that the cylinder 17 has a reflective surface which reflects a large portion of the heat radiation or absorbs as little heat radiation as possible. The high reflectivity of the surface on the Outside of the cylinder 17 is particularly advantageous for the shielding against heat radiation. The high reflectivity of the surface on the inside of the cylinder 17 is also advantageous in order to direct thermal radiation from (and in particular only out) the detection area 83 to the sensor units 13, 23. The optical screen device 7 can also be configured as a wall, which surrounds the sensor device 13, 23 at least partially and preferably annularly. The cross section may be round, polygonal, oval or rounded, a design as a cone is possible.

Furthermore, an insulation device 8 for thermal insulation is provided, which is arranged between the optical shield device 7 and the magnetic shielding device 4. The insulation device 8 consists here of an air layer 18, which is between the ferrite 14 and the cylinder 17. Preferably, there is no exchange with the ambient air to avoid convection. But it is also possible an exchange with the ambient air. By the insulation device 8 in particular a heat conduction from the ferrite 14 to the cylinder 17 is counteracted. In addition, the cylinder 17, as already mentioned above, equipped with a reflective surface to counteract heat transfer from the ferrite 14 to the cylinder 17 by heat radiation. Such an onion-dish-like arrangement with an outer magnetic shielding device 4 and an inner optical shield device 7 and an insulating device 8 located between them provides a particularly good shielding of the sensor units 13, 23 from radiation influences from outside the detection range 83. This has a very advantageous effect on the reproducibility or reliability of the temperature detection. The insulation device 8 has, in particular, a thickness of between approximately 0.5 mm and 5 mm and preferably a thickness of 0.8 mm to 2 mm and particularly preferably a thickness of approximately 1 mm.

The isolation device 8 may also be at least one medium with a correspondingly low heat conduction, such. For example, a foam material and / or a polystyrene plastic or other suitable insulating material.

The sensor units 13, 23 are arranged here in a thermally conductive manner on a thermal compensation device 9 and in particular are coupled in a thermally conductive manner to the thermal compensation device 9. The thermal compensation device 9 has for this purpose two coupling devices, which are formed here as recesses in which the sensor units 13, 23 are embedded accurately. This ensures that the sensor units 13, 23 are at a common and relatively constant temperature level. In addition, the thermal compensation device 9 ensures a homogeneous temperature of the sensor unit 13, 23, when they are in operation of the cooking device. 1 heated. An unequal own temperature can lead to artefacts during the detection, in particular in the case of sensor units 13, 23 designed as thermopiles. To avoid heating the thermal compensation device 9 by the cylinder 17, a spacing between cylinder 17 and thermal compensation device 9 is provided. The copper plate 19 may also be provided as the bottom 27 of the cylinder 17.

In order to enable a suitable thermal stabilization, the thermal compensation device 9 is designed here as a solid copper plate 19. However, it is also possible at least in part another material with a correspondingly high heat capacity and / or a high thermal conductivity.

The sensor device 3 here has a radiation source 63, which can be used to determine the reflection properties of the measuring system or the emissivity of a food container 200. The radiation source 63 is embodied here as a lamp 111, which emits a signal in the wavelength range of the infrared light and the visible light. The radiation source 63 may also be formed as a diode or the like. The lamp 111 is used here in addition to the reflection determination for signaling the operating state of the cooking device 1.

In order to focus the radiation of the lamp 111 on the detection region 83, a region of the thermal compensation device 9 and the copper plate 19 is formed as a reflector. For this purpose, the copper plate 19 has a concave-shaped depression, in which the lamp 111 is arranged. The copper plate 19 is also coated with a gold-containing coating to increase the reflectivity. The gold-containing layer has the advantage that it also protects the thermal compensation device 9 from corrosion.

The thermal compensation device 9 is attached to a holding device 10 designed as a plastic holder. The holding device 10 has a connecting device, not shown here, by means of which the holding device 10 can be latched to a support means 30. The support device 30 is formed here as a printed circuit board 50. On the support means 30 and the circuit board 50 also other components may be provided, such. As electronic components, control and computing devices and / or mounting or mounting elements.

Between the glass ceramic plate 15 and the induction device 12, a sealing device 6 is provided, which is designed here as a micanite layer 16. The micanite layer 16 is used for thermal insulation, so that the induction device 12 is not heated by the heat of the cooking area 31. In addition, here is a micanite layer 16 for thermal insulation between the ferrite 14 and the glass ceramic plate 15th intended. This has the advantage that the heat transfer from the hot in the glass ceramic plate 15 to the ferrite 14 is severely limited. As a result, hardly any heat emanates from the ferrite body 14, which could be transmitted to the insulation device 8 or the optical screen device. The micanite layer 16 thus counteracts an undesirable heat transfer to the sensor device 3, which increases the reliability of the measurements. In addition, the micanite layer 16 seals the sensor device 3 dust-tight against the remaining regions of the cooking device 1. In particular, the micanite layer 16 has a thickness between about 0.2 mm and 4 mm, preferably from 0.2 mm to 1.5 mm and particularly preferably a thickness of 0.3 mm to 0.8 mm.

The cooking device 1 has on the underside a cover 41, which is designed here as an aluminum plate and the induction device 12 covers. The covering device 41 is connected to a housing 60 of the sensor device 3 via a screw connection 122. Within the housing 60, the sensor device 3 is arranged elastically relative to the glass ceramic plate 15. For this purpose, a damping device 102 is provided which has a spring device 112 here.

The spring device 112 is connected at a lower end to the inside of the housing 60 and at an upper end to the printed circuit board 50. The spring device 112 presses the printed circuit board 50 with the ferrite body 14 and the micanite layer 16 mounted thereon upwards against the glass ceramic plate 15. Such an elastic arrangement is particularly advantageous since the sensor device 3 should be arranged as close as possible to the glass ceramic plate 15 for metrological reasons , This directly adjacent arrangement of the sensor device 3 on the glass ceramic plate 15 could cause damage to the glass ceramic plate 15 in the event of impacts or impacts. Due to the elastic reception of the sensor device 3 relative to the carrier device 5, shocks or impacts are damped on the glass ceramic plate 15 and thus reliably prevent such damage.

An exemplary measurement in which the temperature of the bottom of a standing on the glass ceramic plate 15 pot is to be determined with the sensor device 3 is briefly explained below:

During the measurement, the first sensor unit 13 detects heat radiation emanating from the bottom of the pot as mixed radiation together with the heat radiation which is emitted by the glass-ceramic plate 15. In order to be able to determine therefrom a radiation power of the pot bottom, the portion of the radiation output emanating from the glass ceramic plate 15 is calculated out of the mixed radiation power. To determine this proportion, the other sensor unit 23 is provided to heat only the heat To detect glass ceramic plate 15. For this purpose, the other sensor unit 23 has a filter device 53, which transmits essentially only radiation having a wavelength greater than 5 μm to the sensor unit 23. The reason for this is that radiation with a wavelength greater than 5 microns is not or hardly transmitted by the glass ceramic plate 15. The other sensor unit 23 thus essentially detects the heat radiation emitted by the glass ceramic plate 15. With the knowledge of the proportion of the heat radiation, which is emitted from the glass ceramic plate 15, the proportion of heat radiation emanating from the pot bottom, can be determined in a conventional manner.

For a good measurement result, it is desirable for as much of the heat radiation emanating from the bottom of the pot to reach the first sensor unit 13 and to be detected by it. For radiation in the wavelength range of about 4 microns, the glass ceramic plate 15 here has a transmission of about 50%. Thus, in this wavelength range, a large part of the heat radiation emanating from the bottom of the pot can pass through the glass-ceramic plate 15. Detection in this wavelength range is therefore particularly favorable. Accordingly, the first sensor unit 13 is equipped with a filter device 43 which is very permeable to radiation in this wavelength range, while the filter device 43 substantially reflects radiation from other wavelength ranges. The filter devices 43, 53 are each designed here as an interference filter and in particular as a bandpass filter or as a longpass filter.

The determination of a temperature from a specific radiant power is a known method. The decisive factor is that the emissivity of the body is known, from which the temperature is to be determined. In the present case, therefore, the emissivity of the pot bottom must be known or determined for a reliable temperature determination. The sensor device 3 here has the advantage that it is designed to determine the emissivity of a Gargutbehälters 200. This is particularly advantageous, since thus any cookware can be used and not just a specific food container whose emissivity must be known in advance.

In order to determine the emissivity of the pot bottom, the lamp 111 emits a signal which has a proportion of heat radiation in the wavelength range of the infrared light. The radiant power or thermal radiation of the lamp 111 passes through the glass ceramic plate 15 on the bottom of the pot and is partially reflected there and partially absorbed. The reflected radiation passes through the glass ceramic plate 15 back to the sensor device 3, where it is detected by the first sensor unit 13 as mixed radiation from the bottom of the pot and the glass ceramic plate 15. At the same time as the reflected signal radiation, the own thermal radiation of the bottom of the pot and the Glass ceramic plate on the first sensor unit 13. Therefore, then the lamp 111 is turned off and only the heat radiation of the pot bottom and the glass ceramic plate detected. The proportion of the reflected signal radiation then results in principle from the previously detected total radiation minus the heat radiation of the pot bottom and the glass ceramic plate.

With knowledge of the proportion of reflected signal from the bottom of the pot signal radiation, the degree of absorption of the pot bottom and thus its emissivity can be determined in a known manner, since the absorption capacity of a body corresponds in principle to the emissivity of a body and the proportion of absorbed by the pot radiation is 1 minus reflected radiation.

The emissivity is redetermined here at certain intervals. This has the advantage that a subsequent change in the emissivity does not lead to a falsified measurement result. A change in the emissivity may occur, for example, when the cookware bottom has different emissivities and is displaced on the cooking surface 21. Different emissivities are very common in cookware trays observed because z. B. already light soiling, corrosion or even different coatings or coatings can have a major impact on the emissivity.

The lamp 111 is also used here for signaling the operating state of the cooking device 1 in addition to the determination of the emissivity or the determination of the reflection behavior of the measuring system. In this case, the signal of the lamp 111 also includes visible light, which is perceptible by the glass-ceramic plate 15. For example, the lamp 111 indicates to a user that an automatic function is in operation. Such an automatic function can, for. B. be a cooking operation, in which the heater 2 is controlled automatically in dependence of the determined pot temperature. This is particularly advantageous because the lighting up of the lamp 111 does not confuse the user. The user knows from experience that the lighting is an operation indicator and belongs to the normal appearance of the cooking device 1. He can therefore be sure that a flash of the lamp 111 is not a malfunction and the cooking device 1 may not work properly.

The lamp 111 may also light up in a certain duration and at certain intervals. It is possible z. B. also that different operating states can be output via different flashing frequencies. Different signals are also possible via different on / off sequences. Advantageously, for each hotplate 21 and each (possible) cooking area 31, a sensor device 3 is provided with a radiation source 63, which is suitable for displaying at least one operating state.

At least one arithmetic unit may be provided for the necessary calculations for determining the temperature and for the evaluation of the detected variables. The arithmetic unit can be at least partially provided on the circuit board 50. However, it is also possible, for example, for the control device 106 to be designed accordingly, or at least one separate arithmetic unit is provided.

The FIG. 4 shows a development in which below the glass ceramic plate 15, a security sensor 73 is attached. The safety sensor 73 is formed here as a temperature-sensitive resistor, such as a thermistor or an NTC sensor, and thermally conductively connected to the glass ceramic plate 15. The safety sensor 73 is provided here to be able to detect a temperature of the cooking area 31 and in particular of the glass ceramic plate 15. If the temperature exceeds a certain value, there is a risk of overheating and the heaters 2 are switched off. For this purpose, the safety sensor 73 is operatively connected to a safety device, not shown here, which can trigger a safety state depending on the detected temperature. Such a security condition has z. B. the shutdown of the heaters 2 and the cooking device 1 result.

In addition, the safety sensor 73 is assigned here as a further sensor unit 33 of the sensor device 3. In this case, the values detected by the safety sensor 73 are also taken into account for the determination of the temperature by the sensor device 3. In particular, when determining the temperature of the glass-ceramic plate 15, the values of the safety sensor 73 are used. So z. B. the temperature, which was determined by means of the other sensor unit 23 on the detected thermal radiation, are compared with the temperature detected by the safety sensor 73. This adjustment can on the one hand serve to control the function of the sensor device 3, but on the other hand can also be used for a tuning or adjustment of the sensor device 3.

The task of the other sensor unit 23 can also be taken over by the safety sensor 73 in an embodiment not shown here. The safety sensor 73 serves to determine the temperature of the glass ceramic plate 15. For example, with knowledge of this temperature from the heat radiation, which detects the first sensor unit 13, the proportion of a pot bottom can be determined. Such a configuration has the advantage that the other sensor unit 23 and an associated filter device 53 can be saved.

The FIG. 5 shows, by way of example, various amplifier signals 621.1, 621.2, 621.3 of the amplifier device 620 based on different output signals 130 (cf. FIG. 6 ) of the first sensor unit 13. For this purpose, the output voltage 662 of the amplifier device 620 was tapped here and plotted over time 302. To illustrate the advantages of offset matching, the amplifier signals 621.1, 621.2, 621.3 shown here are based on different output signals 130 that have not been adjusted by an offset 600. Due to the lack of offset matching, the amplifier device 620 is overdriven at the upper amplifier signal 621.3, while the lower two amplifier signals 621.1, 621.2 are in the linear amplifier range.

The amplifier signals 621.1, 621.2, 621.3 shown here, which are thus output signals of the amplifier device 620, for better clarity reflect the signal profile at essentially constant temperature conditions in the cooking region 31. During the reflectance measurements to determine the emissivity of the cooking vessel bottom, the lamp 111 is turned on 631 and the output voltage 662 rises accordingly. When the 630 lamp 111 is switched off, the output voltage 662 drops accordingly. The lamp state 632 is entered as a dashed curve.

The first output signal 621.1 shows the signal profile when the food container 200 and the glass ceramic plate 15 are still cold or have room temperature. The second output signal 621.2 reflects the waveform when the food container 200 and the glass ceramic plate 15 are hot, z. B. during a usual cooking process. The signal characteristics of both amplifier output signals 621.1, 621.2 unambiguously reflect the lamp state 632, so that a reliable reflectance determination is possible.

The third output signal 621.3 shows the waveform when the food container 200 is hot and the glass-ceramic plate 15 is very hot and in particular hotter than 150 ° C, which z. B. can occur even with induction hobs in frying operations. In this case, an overdriving of the amplifier device 620 occurs. With such a signal curve, reliable determination of the reflectance is no longer possible.

One approach would be, for example, to reduce the gain, which would however corresponding losses with respect to the resolution and thus the accuracy of the reflectance measurement result, since the output signal 130 of the sensor unit must be suitably high amplified in order to obtain a sufficient resolution for the reflection measurement. In addition, a change in gain would also require a corresponding calibration for that range, which adversely affects the manufacturing cost.

The cooking device 1 presented here and the method now have the advantage that the reinforcement can remain the same, regardless of the temperatures of the glass ceramic plate 15 and the cooking vessel and independently of a reflection measurement. Instead, the output signal 130 of the respective sensor unit is first adjusted by the adjustable offset 600 and only then amplified. The offset 600 (cf. FIG. 7 ) is advantageously selected such that the voltage of the input signal based on the output signal 130 for the amplifier device 620 is shifted into a voltage range in which a possible linear amplification is ensured.

The FIG. 6 shows a schematic amplifier device 620 with a shifter 610 and a differentiation device 650. In this case, the output signal 130 of the first sensor unit 13 is supplied via the intermediate difference formation device 650 as an input signal 651 of the amplifier device 620 and amplified by this. The now amplified by the amplifier means 620 output signal 130 of the first sensor unit 13 leaves the amplifier means 620 as the amplifier signal 621 and can be further evaluated for temperature determination, for. B. from the sensor device 3 itself or from the controller 106th

Further signals of the sensor device 3 and in particular the output signal 130 of the other sensor unit 23 can likewise be supplied to the amplifier device 620. In order to further increase the degree of amplification, two or more amplifier stages may be provided.

In order to obtain the offset 600 (cf. FIG. 7 ), the amplifier signal 621 is forwarded to the shifter 610. The shifter 610 evaluates the incoming amplifier signal 621. If the signal lies in an overdriven area or outside a range defined by a threshold value 663 (cf. FIG. 7 ), the shifter 610 effects an adjustment of the output signal 130 of the sensor unit, before it is supplied as an input signal 651 to the amplifier device 620, by an offset 600, in order to push the resulting amplifier signal 621 back into a region which does not overdrive. For this purpose, for example, the reference voltage 641 applied to the second input of the intermediate device 650 connected between the sensor unit and amplifier device is adapted via a fine adjustment.

Between the respective voltage of the output signal 130 at the first input of the difference formation device 650 and the reference voltage 641 at the second input of the difference formation device 650 then results in a differential voltage, which can then be amplified by the amplifier device 620, so that the difference voltage Voltage of the input signal 651 for the amplifier device is. For example, if the voltage of the output signal 130 is too high to be optimally amplified so that the corresponding amplifier signal 621 is in an overdriven range or out of a threshold range, a suitably high reference voltage is set. This results from the reference voltage minus the output signal voltage, a differential voltage which is smaller than the voltage of the output signal 130 and thus can be amplified without overdriving.

For fine adjustment or adjustment is in the in FIG. 6 shown as Versatzeinrichtung 610 at least one microcontroller 611 with at least one input module 612 and at least one output module 614 is provided. In particular, the input module 612 comprises an A / D converter, which preferably also serves to measure the incoming amplifier signal 621. The output module 614 comprises a D / converter and / or a PWM output for switching over reference voltages, preferably in combination with a low-pass filter, and / or at least one digital output. It may also be provided as shown here, an additional circuit 640 for fine adjustment. The fine adjustment takes place in particular before the actual reflection measurement is carried out. With this solution, an equivalent measurement of the reflectance is independent of the instantaneous temperature of the glass ceramic plate 15 and the cooking vessel possible.

Unlike in FIG. 6 represented, the amplifier means may also be formed as an operational amplifier and thereby include the difference-forming means, so that it is not carried out separately. Such an amplifier device would have two inputs, wherein the output signal of the sensor device is applied to one input and the reference voltage set in each case by the offset device is present at the other input.

In the FIG. 7 a profile of an amplifier signal 621 is sketched. The output voltage 662 at the amplifier was plotted against the output voltage 661 of the sensor signal, that is, the voltage of the output signal 130 of the sensor unit. At this time, the output signal 130 to be amplified is automatically adjusted by the offset 600 when the amplifier signal 621 reaches a threshold 663 at which overdriving is imminent. The offset 600 is set by the microcontroller 611, which applies a suitable reference voltage to the subtraction device 650. The reference voltage is set here so that the maximum permissible input voltage 651 results as the differential voltage, which does not lead to overdriving the amplifier.

The offset 600 is selected here from a group of skews 601, 602, 603, 604, depending on how high the exceeded threshold value is. Each offset 600 is characterized by a predetermined voltage. The result is the characteristic Z offset shown here, i. This allows signals with a very wide voltage range to be amplified without the amplifier device 620 having to have multiple stages or amplifier regions. As a result, calibrations of amplifier ranges can be saved.

When the voltage of the output signal 130 falls below a corresponding threshold again, e.g. As the temperature in the cooking area 31 decreases, the offset 600 is taken back accordingly. This is z. B. reduces the reference voltage. As a result, the corresponding amplifier signal 621 always lies in a linear range and thus offers an optimum resolution, so that a reliable temperature determination based on the output signal 130 is possible.

LIST OF REFERENCE NUMBERS

1

cooking facility

2

heater

3

sensor device

4

magnetic shielding device

5

support means

6

seal means

7

optical screen device

8th

isolation facility

9

thermal compensation device

10

holder

11

hob

12

inductor

13

sensor unit

14

ferrite

15

Glass ceramic plate

16

Mika Nitsch layer

17

cylinder

18

layer of air

19

copperplate

21

cooking

23

sensor unit

27

ground

30

support device

31

cooking area

33

sensor unit

41

cover

43

filtering device

50

PCB

53

filtering device

60

casing

63

radiation source

73

security sensor

83

detection range

100

Cooking appliance

102

attenuator

103

oven

104

oven door

105

operating device

106

control device

111

lamp

112

spring means

122

screw

130

Output signal of the sensor device or sensor unit

200

food to be cooked

302

Time

600

offset

601

first offset

602

second offset

603

third offset

604

fourth offset

610

offset means

611

microcontroller

612

input module

614

output module

620

amplifier means

621

amplifier signal

621.1

amplifier signal

621.2

amplifier signal

621.3

amplifier signal

630

Lamp switched off

631

Lamp switched on

632

lamp status

640

circuit

641

reference voltage

650

Differencing means

651

Input signal of the amplifier device

661

Output voltage of the sensor signal

662

Output voltage of the amplifier signal

663

threshold

Claims (13)

1. Method for operating a cooking device (1) comprising at least one hob (11), at least one heating device (2) provided for heating at least one cooking region (31), at least one sensor device (3) for detecting at least one characteristic value for temperatures of the cooking region (31), and at least one control device (106),
   the control device controlling the heating device (2) at least on the basis of the value detected by the sensor device (3),
   at least one output signal (130) from the sensor device (3) being adapted by means of at least one adjustable offset (600) and being subsequently amplified,
   characterised in that
   the offset (600) is adjusted on the basis of calibration of the sensor device (3), a different offset (600) being adjusted for calibration than for the detection of measured values for determining temperature.
2. Method according to the preceding claim, characterised in that the offset (600) is adjusted by means of a reference voltage.
3. Method according to any of the preceding claims, characterised in that the offset (600) is adjusted on the basis of the voltage of the output signal (130).
4. Method according to claim 1, characterised in that in order to calibrate the sensor device (3), at least one radiation source (63) emits electromagnetic radiation, at least temporarily, and at least some of the radiation emitted by the radiation source (63) is received again by the sensor device (3), a calibration value being derived from the output signal (130), which is emitted by the sensor device (3), and used to calibrate the sensor device (3), and the output signal (130) provided for deriving the calibration value being adapted by means of at least one offset (600) that has been adjusted.
5. Method according to any of the preceding claims, characterised in that the offset (600) is adjusted before calibration.
6. Method according to any of the preceding claims, characterised in that the output signal (130) provided for deriving the calibration value is adapted by means of an offset (600) that is different from that for the output signal (130) when detecting at least one characteristic value for temperatures of the cooking region (31).
7. Method according to any of the preceding claims, characterised in that the offset (600) is adjusted when a predefined value for the output signal (130) is reached.
8. Method according to any of the preceding claims, characterised in that the offset (600) is adjusted when the output signal (130) leads to an amplifier device (620) used for amplification being overloaded.
9. Method according to any of the preceding claims, characterised in that the voltage of the output signal (130) is adapted to at least one predefined voltage in the form of an offset (600).
10. Method according to any of the preceding claims, characterised in that a predefined amplification is adjusted on the basis of the output signal (130) and/or the offset (600) that has been adjusted.
11. Cooking device (1) comprising at least one hob (11), at least one heating device (2) provided for heating at least one cooking region (31), at least one sensor device (3) for detecting at least one characteristic value for temperatures of the cooking region (31), and at least one control device (106) for controlling the heating device (2) on the basis of the value detected by the sensor device (3),
    at least one adjustable offset device (610) being provided for adjusting at least one offset (600) in order to shift at least one output signal (130) from the sensor device (3) by the offset (600), and at least one amplifier device (620) being provided for amplifying the shifted output signal (130),
    characterised in that the offset (600) is adjusted on the basis of calibration of the sensor device (3), the output signal (130) provided for deriving the calibration value being adapted by means of an offset (600) that is different from that for the output signal (130) when detecting at least one characteristic value for temperatures of the cooking region (31).
12. Cooking device (1) according to the preceding claim, characterised in that the amplifier device (620) comprises at least two amplifier stages,
    a predefined amplifier stage being adjusted on the basis of the output signal (130) and/or the offset (600) that has been adjusted.
13. Cooking device (1) according to any of the preceding claims, characterised in that in order to calibrate the sensor device (3), at least one radiation source (63) is provided for emitting electromagnetic radiation, the sensor device (3) being suitable and designed for again receiving at least some of the radiation emitted by the radiation source (63) and for outputting said radiation as a signal,
    and a control device (106) being suitable and designed for deriving a calibration value for calibrating the sensor device (3) from the signal emitted by the sensor device,
    the offset device (610) being suitable and designed for adapting the output signal (130) provided for deriving the calibration value by means of an adjustable offset (600).

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