EP1217873A2 - Temperature of cooking vessels sensing method and device - Google Patents

Abstract

The device has at least one flat measurement element (15,17) near a heating zone (3) on the upper side of the cooking plate (2) with an upper side for contact with the bottom of the cooking vessel (25) and a device (8) for determining the temperature of the measurement element in the form of one or more infrared sensors. Independent claims are also included for the following: an electric heating device with as cooking plate and a method of detecting temperature of cooking vessel.

Description

Field of application and state of the art

The invention relates to a method and a device for detection the temperature of a cooking vessel according to the preamble of claims 1 and 9 and claim 10. The cooking vessel is advantageously on a hotplate or heating plate, for example a glass ceramic plate, a preferably electrically operated heating device set up in the area of a heating zone of the heating device.

For heating food and other heating materials when cooking, Frying, deep frying or the like are nowadays often heating devices with in usually made of glass ceramic material, on which one or more cooking or heating zones are defined, the heating devices arranged below the hotplate are heated. The heating devices can, for example, in In the form of electric radiant heaters or in the form of induction devices with one or more induction coils for inductive Heating the cooking vessels set up on the assigned cooking zone be trained.

Most of the conventional cookers use a cooking process controlled by means of an operating element assigned to the cooking zone a power level suitable for the desired cooking process the cooking zone and then the cooking process by one Operator is monitored. The quality of the cooking result depends on it significantly depending on the experience of the operator, as a rule no exact recording of the temperature of the cooking vessel or the heating material contained therein is carried out.

Automatic cooking systems have also been proposed which is a more or less accurate temperature measurement of the installed Enable cooking vessels to, for example, an automatic, allow cooking controlled by temperature detection. at a known system special cooking vessels are used in to the side a little above the bottom of the cooking vessel black color marking is attached. Through one from the side this color marking directed infrared sensor can do that from the color marking radiated radiation spectrum detected and the Temperature of the cooking vessel. The measured value can be used Control of the heating device assigned to the cooking zone is used be, for example in the event of overheating, the heating power of the associated heating device shutdown or the hotplate off. The cooking system requires special, with appropriate Colored cooking vessels. Will be on color markers waived, one faces the problem that usually the surface areas observed with regard to their heat radiation the structure and color of the cooking vessel are different, so that change the surface emissivity in an uncontrollable manner can, which results in an inaccurate measurement. In addition arise Due to the lateral observation of the cooking vessels, there are usually restrictions with regard to the installation and handling of those on the hotplate erected cooking vessels.

Task and solution

The invention has for its object a method and an apparatus for recording the temperature of hotplates To create cooking vessels that have the disadvantages of the prior art Avoid technology. In particular, without limitation at Handling of the cooking vessels enables precise temperature measurement become.

To achieve this object, the invention proposes a device the features of claims 1 and 9 and a method with the Features of claim 10. Preferred further developments are in the dependent claims. The wording of all Claims become the content of the content by express reference Description made.

According to the invention is in the area of a heating zone to be monitored the top of the hotplate facing the cooking vessel at least one flat measuring element is provided, which the one Bottom of a cooking vessel to be set up facing and for touch contact provided with the bottom of the cooking vessel top whose area is normally a fraction of the total area of the assigned heating zone. The temperature of this measuring element is determined, for which purpose at least one sensor is usually used for detection the temperature of the measuring element is provided. Because the measuring element is designed so that the normally largely flat or slightly arched bottom of a standing cooking vessel under the influence of the cooking vessel weight over a large area on the measuring element is pressed, the temperature of the measuring element arises due to of heat conduction usually quickly to the temperature of the bottom of the cooking vessel on. For fast, reliable temperature adjustment to ensure, the measuring element consists appropriately a good heat-conducting material and has a low heat capacity. In addition, there is a certain wear resistance or scratch resistance or abrasion resistance advantageous, so even after many years Operation no wear-related functional impairments are to be feared. By providing at least one regarding its properties defined measuring element in the area of Heating zone, an exact temperature measurement on the cooking vessel is possible, as long as this is set up in such a way that a sufficiently good touch contact to the measuring element. The measurement can be done in this Case largely independent of other properties of the cooking vessel be, for example, of the heat radiation ability of its Surface. By measuring elements according to the invention are largely standardized measuring points for the precise temperature determination of the cooking vessel temperature created in the bottom area of the cooking vessel.

Further developments in which the determination is particularly preferred the temperature of the measuring element from below through the hotplate he follows. This makes it possible to use temperature detection devices of the external measuring elements, for example, largely hermetically sealed space below the glass ceramic plate to accommodate a hob protected. On lines or The like, which lead to the measuring element on the top of the plate to be dispensed with. For example, directly below a measuring element a measuring resistance element on the inside of the hotplate be attached, for example by printing, with the under utilization the heat conduction through the hotplate the measuring element temperature can be determined. In particular, however, below the Hotplate, possibly at a distance from it, at least one infrared sensor be arranged, with the help of the temperature of the hotplate facing Bottom of the measuring element can be detected. The material In this case, the hotplate should have sufficient permeability or transmission for the thermal radiation used for the measurement exhibit. Since the bottom of the measuring element is independent of the Cooking vessel properties one of the type of measuring element and possibly of the hotplate surface certain, defined emissivity for Such a system can be used with any type of cooking vessel work precisely without taking any special precautions on the cooking vessel itself to ensure a certain radiation ability Need to become. This allows users of such systems without special investments in the purchase of cooking vessels the advantages use a temperature measurement using infrared sensors.

A measuring element can for example by a on the top of the Hotplate self-adhesive material layer formed, for example, by using a thin-film process or a thick-film process applied material layer, especially a temperature-resistant Coat of paint. This can be a particularly good one Adhesion of the measuring element on the top of the hotplate reached be, can also shape and / or thickness of the measuring element the procedure for the coating in a simple manner to the desired measuring element design can be adapted. For example suitable layers of paint can be used, as in the usual decoration of glass ceramic surfaces become. The order can be placed in the same process step. at If necessary, metal particles can be added.

Alternatively or additionally, it is also possible for at least one measuring element by a separate piece of material, for example a piece a metal foil is formed, which with the help of suitable fasteners, for example by gluing on the top of the hotplate can be attached. This is especially true in the case of infrared temperature measurement from the bottom of the hotplate to an adequate one Emissivity and / or heat radiation transparency of the adhesive material to watch out for.

To ensure sufficient contact, which is as large as possible it is between the measuring element and the underside of the cooking vessel useful if the top of the measuring element is the top of the Slightly protruding hotplate, i.e. opposite the hotplate top is sublime. Here are small protrusion heights of less than about 0.2 mm is preferred, around the height of an air gap that may arise between the top of the hotplate and the bottom of the cooking vessel. The protruding heights are expediently between approximately 0.05 mm and about 0.2 mm, especially at about 0.1 mm.

Furthermore, it can be useful if in the area of the cooking zone several measuring elements arranged at a lateral distance from each other are provided, which can be ensured that also at Cooking vessel sizes that are not optimally suited for the size of the cooking zone are, at least one measuring element always accurate temperature measurements supplies. A triangular arrangement of three is normally preferred idenitic measuring elements which can be used to ensure that a cooking vessel with sufficient floor space cannot tip over on three points is supported and cannot wobble. To avoid a the pot or the like. is not moved by a measuring element during stirring formed support surface rotates, it is advantageous if none Measuring element is located in the central area of the heating zone. Usually will an arrangement of several measuring elements on a circle advantageous be, the diameter of which is slightly smaller or approximately equal to that Typical diameter to be placed on the corresponding heating zone Cookware corresponds, so that a support in the outer edge area a cooking vessel base is guaranteed.

The invention, one or several reference measuring surfaces for infrared temperature measurement from Proposing out inside a ceramic hob also affects Heating devices with a temperature detection device according to the invention are equipped, in particular electric heating devices. she is Particularly advantageous for use in induction hobs where the heat for heating up cooking vessels in the wall material of the cooking vessel itself, especially in the bottom of the cooking vessel inductively generated eddy currents. Especially with such Electric heating devices is the exact determination of the cooking vessel temperature useful as indirect temperature monitoring, for example by monitoring the hotplate temperature, may be inaccurate because there may be large temperature differences between the hotplate and the cooking vessel exist. Inductive cooking systems are also possible Radiant heating systems are therefore particularly suitable because that's usually the case with radiant heating systems a measuring element heated directly from below by heat radiation is, so that there may be temperature differences to the cooking vessel temperature can result. It is also the case with inductive cooking systems Usually easier, below the hotplate, for example nearby an induction coil, one or more heat-sensitive infrared sensors protected because in this area compared to Radiant heating systems typically have significantly lower temperatures rule what the functionality and lifespan of Infrared sensors can improve.

In the case of inductive systems, the material of the hotplate can also be so be chosen to be more typical, especially in the temperature range Pot bottom temperatures, which are usually when cooking below approx. 140 ° and for example when frying at a maximum of 250 ° C 300 ° C, especially for the corresponding heat radiation is permeable. A transmissibility at higher temperatures, that is, at shorter wavelengths of heat radiation, such as, for example required for glass ceramic plates in radiant heating systems is not absolutely necessary, so the hotplate material in terms of its transmission properties optimally to the requirements can be coordinated during temperature detection.

These and other features go beyond the claims from the description and the drawings, the individual Features each individually or in groups in the form of sub-combinations in one embodiment of the invention and others Areas to be realized and advantageous as well as protectable Can represent designs.

Brief description of the drawings

An embodiment of the invention is shown in the drawings and is explained in more detail below. The first drawing figure 1 shows a preferred embodiment in a schematic representation a temperature detection device according to the invention, the is installed in an induction hob. Fig. 2 shows a top view to the induction hob on Fig. 1.

Detailed description of the embodiment

The schematic vertical section of FIG. 1 shows a section of a electric stove, the top or worktop through a horizontal glass ceramic plate 2 is defined, the one or several hotplates or cooking or May have heating zones 3. The intended for the individual heating zones Heaters 4 are opposite the inside or bottom 5 of the plate 2 and are arranged in the inductive shown Electric heating device by multi-winded, flat in the example shown Induction coils 6 are formed, each with a short distance below the glass ceramic plate 2 are attached. The induction coil shown as an example 6 is connected to a radio frequency generator, not shown Cooking appliance connected. In the radially outer area of the flat induction coil 6 are cylindrical in their plate-facing area and funnel-shaped heat shields 7 attached, which ensure that inside and below the shield 7 the electromagnetic alternating field generated by the coil 6 is greatly weakened and radiating downwards from the area of the plate 2 Heat is largely shielded.

In the shielded area there is visual contact to the underside of the plate 5 schematically illustrated infrared sensors 8, for example with a infrared-sensitive diode, arranged on an electronic evaluation system 9 for processing the voltage signals provided by the infrared sensors are connected. The evaluation electronics 9 can a circuit board can be arranged in the hermetically sealed Space below the glass ceramic plate 2 is attached and the electronic Components of an electronic control device for the electrical device 1 wears.

The shape and size of the induction coil 6 assigned, in the example circular heating zone 3 is in the interior of the hob a surrounding the induction coil with radial distance up to the Underside 5 of the glass ceramic plate 2 reaching ring 10 defined, the one that shields the electromagnetic radiation from the coil 2, electrically conductive material, such as aluminum can. On the flat top 11 of the approximately one centimeter thick, plane-parallel hotplate 2 can the outer limit of round heating zone 3 by a ring not shown from printed Decor color to be marked in order to provide a user with a correct, to allow the most central possible placement of cooking vessels. In the case of hot plates 2 from one for light in the visible Spectrum of transparent material can border the cooking zone through the ring 10 visible in this case from above.

Inside the heating zone 3 there are three on the hotplate top 11 flat, circular color layer areas 15, 16, 17 applied, the Diameter in each case a fraction, for example about a tenth of the diameter of the cooking zone. The color layer circles can for example in thin film or thick film technology e.g. by printing be applied and have typical thicknesses in the range of approx. 0.1 mm, so that the largely flat tops 18, 19, 20 of the color circles are evenly raised against the top of the plate 11. With the undersides 21, 22, 23 of the paint layers adhere firmly to the Top of the plate 11. The centers of the color circles 15, 16, 17 lie with even distance from each other on a circle, its diameter can be about 10% to 30% smaller than the cooking zone diameter. As a result, the raised layers of paint form a triangular arrangement, to the size of the cooking zone 3 adapted cooking vessel 25 is tilt-proof and wobble-free. Becomes the cooking vessel 25 more or less centrally in the area of the cooking zone set up, it touches the largely flat or slightly dome-shaped curved cooking vessel bottom 26 the tops 18, 19, 20 of the Color dots 15, 16, 17 each over essentially the entire area, so that under the weight of the cooking vessel and the inside A flat contact pressure between the colored layer elements 15, 16, 17 and the bottom of the cooking vessel 26 is ensured.

The color layer circles that can be reliably attached in a cost-effective manner 15, 16, 17 form measuring elements of a temperature detection device, which allows the temperature of the cooking vessel, in particular of the cooking vessel base 26, in an economical manner to be determined reliably and precisely. For this, at least one of the Measuring elements 15, 16, 17 in relation to those located below the plate 2 Infrared sensor 8 arranged so that the in contact with the top of the plate 11 standing underside of the measuring element in line of sight stands with the infrared sensor 8. As an alternative to the direct one outlined Line of sight can be a connection that conducts heat radiation between the infrared sensor and the underside of the measuring element also using a or more mirrors suitable for reflecting infrared radiation and / or created with the aid of heat radiation-conducting optical fibers become.

If a pot or the like is now placed on the measuring elements 15, 16, 17 and heated by turning on the induction heater, so be due the expediently high thermal conductivity and low heat capacity the measuring elements and due to the large contact pressure the undersides of the measuring elements between the bottom of the pot and the measuring elements largely the temperature with only a slight time delay assume that the one in contact with the respective measuring element Area of the pot bottom. A particular advantage of the invention lies now that this largely corresponds to the pot bottom temperature Temperature precisely defined with regard to their emission properties There is a reference surface, namely in contact with the top of the hotplate standing measuring element underside 21, 22, 23. Thereby it is possible with the help of the infrared sensor 8 through the infrared transparent Plate 2 through a very precise temperature measurement from below perform because there are differences in the radiation ability different cookware bases with this type of temperature measurement not or only negligibly. The The measurement result of this temperature measurement method is therefore largely regardless of the emissivity of the bottom of the pot, so that cooking vessels any surface texture without affecting the Temperature measurement can be used as long as the pan bottom shape a sufficiently large contact to the Measuring element used for the measurement allowed. This touch contact is useful to ensure that the measuring element by Heat conduction quickly adapts to the pot bottom temperature.

Since the invention enables the pot bottom temperature or the To determine the floor temperature of other cooking vessels promptly and relatively accurately, A temperature detection according to the invention is particularly suitable good for automatic, sensor-supported cooking systems, at which the heating power of the heating devices assigned to each cooking zone depending on the temperature of the food or cooking vessel is controllable. However, the sensed temperature can only to be displayed to an operator the cookware to enable gentle and effective cooking, roasting, deep-frying or the like.

Claims (11)

Device for detecting the temperature of a cooking vessel placed on a hotplate, in particular a glass ceramic plate, of a heating device in the area of a heating zone, characterized in that in the area of the heating zone (3) on the top (11) of the hotplate (2) at least one Flat measuring element (15, 16, 17) is arranged, which has a top (18, 19, 20) provided for contact with a bottom (26) of the cooking vessel (25), and that a device (8) for determining the temperature of the Measuring element is provided. Apparatus according to claim 1, characterized in that at least one sensor, in particular an infrared sensor (8), for detecting the temperature of the measuring element (15, 16, 17) is arranged below the hotplate (2). Apparatus according to claim 1 or 2, characterized in that at least one measuring element (15, 16, 17) is formed by a material layer applied to the upper side (11) of the hotplate (2), in particular by a printed color layer. Device according to one of the preceding claims, characterized in that at least one measuring element is formed by a separate, thin piece of material, in particular a metal foil, attached to the top (11) of the hotplate. Device according to one of the preceding claims, characterized in that the upper side (18, 19, 20) of the measuring element (15, 16, 17) slightly projects above the upper side (11) of the hotplate, preferably by less than 0.2 mm, in particular by between 0.05 mm and 0.15 mm. Device according to one of the preceding claims, characterized in that several measuring elements (15, 16, 17) are provided in the region of the cooking zone (3), in particular three measuring elements arranged in a triangular arrangement. Device according to one of the preceding claims, characterized in that at least one measuring element (15, 16, 17) is arranged eccentrically to a center of the cooking zone (3) and / or that no measuring element is arranged in the center of the cooking zone. Device according to one of the preceding claims, characterized in that the measuring element (15, 16, 17) consists essentially of a good heat-conducting material with low heat capacity. Electric heating device with a hotplate, in particular a glass ceramic plate, on which at least one heating zone which is heated by means of a heating device arranged below the hotplate is defined, and with a device for detecting the temperature of a cooking vessel set up on the heating zone, characterized in that the device for detecting the temperature of the cooking vessel (25) is designed according to one of claims 1 to 8. Method for detecting the temperature of a cooking vessel, which is placed on a hotplate, in particular a glass ceramic plate, of a preferably electrical heating device in the area of a heating zone, characterized by the following steps: Providing at least one flat measuring element (15, 16, 17) with an upper side (18, 19, 20) provided in the region of the cooking zone (3) for contacting a bottom (26) of the cooking vessel (25); Setting up a cooking vessel (25) in the region of the cooking zone such that a bottom surface of the cooking vessel comes into contact with the top of the measuring element; Determination of the temperature of the measuring element. Method according to Claim 10, characterized in that the temperature of the measuring element (15, 16, 17) is determined from below through the hotplate, preferably the heat radiation emitted by the hotplate from the underside (21, 22, 23) is detected.

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