EP1768461B1 - Method to generate, process and evaluate a temperature-correlated signal and corresponding device - Google Patents

Abstract

The method involves recording the temperature of an electrical cooking device, cookware (13) provided in the device and/or a cooking ware content by a temperature-sensor device (S). The temperature signal (T) recorded by the temperature-sensor device in a temporal process is once differentiated after a time. The result is inverted and the inverted result is exponentiated with exponential values between 0.5 and 1.0 to provide an initial value, which is further processed and evaluated. An independent claim is also included for a method for operating an electrical cooking device and hob under application of results of temperature evaluation.

Description

Field of application and state of the art

The invention relates to a method for generating, processing and evaluating a temperature or a correlated with the temperature of an electric cooking appliance or a hob signal in the operating state of the device, and a corresponding apparatus and a method for operating an electric cooking appliance or a hob.

There are various methods known to detect temperature conditions on a hob, both for the protection of the hob plate itself against overheating and for performing so-called automatic cooking programs, see for example US 6118105 . EP 858722 A . DE 10329840 A . DE 19906115 C or DE 10356432 A ,

The US 5,437,002 describes a method for turning off a coffee machine when the liquid in the tank has come to an end. This can be detected by a temperature sensor in the tank, which may be a thermistor, for example. The temperature signal of the sensor is monitored to control a heater for the water tank depending thereon. In this case, it is monitored whether the temperature in accordance with the temperature signal measured by the temperature sensor is above or below a limit value. In this case, a certain hysteresis can be provided in the switching process.

The US 4,629,852 describes a control circuit for controlling the operation of a heating element with a temperature sensor. Not only the absolute value of the temperature sensor is evaluated, but also the rise or fall of the temperature signal over time.

The US 4,523,084 describes a control method for a heating element. In this case, the change in a voltage across the heating element is monitored as a function of the temperature. This voltage across the heating element can either be monitored analogously or with a voltage amplification circuit with simultaneous measurement of the current by means of a current amplification circuit on a current measuring resistor. Then amplifier lines are connected downstream.

Task and solution

The invention is based on the object to provide alternative methods of the type mentioned above and a corresponding device, with which in particular a value detected via a temperature sensor device value can be provided as output value that can be further processed or used as well as possible.

This object is achieved by a method having the features of claim 1, a method for operating an electrical appliance with the features of claim 13 and a corresponding device having the features of claim 15. Advantageous as preferred embodiments of the invention are the subject of further claims explained in more detail below. The wording of the claims is incorporated herein by express reference. Some features apply to both the methods and the device. They are explained in part only once in the following, but can apply to both process and device independently.

According to the invention, it is provided that the temperature of the electric cooking appliance or of the cooking hob, of a cooking utensil heated thereon or heated in operation, and / or of a cooking utensil content contained therein, such as a foodstuff, is detected by a temperature sensor device. The temperature signal detected by the temperature sensor device over time is differentiated once in a while. This result is then inverted and the result of the inversion is in turn raised to a power of between 0.5 and 1, preferably between 0.6 and 0.8. This results in an initial value, which in turn is then used for further processing and evaluation. For example, As mentioned above, too high temperatures avoided or certain cooking programs or automatic processes are controlled.

mit c positiv, konstant und aus dem Intervall 0,5 bis 1 gewählt. Die zeitlichen Intervalle Δx(t')=x(t1)-x(t2) sind groß genug zu wählen, um mit dem Rauschen der Messwerte nicht in Konflikt zu kommen. Dieses würde ansonsten unter ungünstigen Umständen den Ausgangswert so stark verrauschen, dass eine Steuerung sehr stark störungsabhängig wäre. T(t') entspricht hierbei dem Signal des Temperatursensors und t(t') entspricht der Zeit, welche während der Messung gemessen wird.Expressed in terms of formulas, this method means that the output value A (t) is formed as $$A\left(\mathit{t\; \text{'}}\right)={\left(\frac{\mathrm{\Delta }\begin{array}{}\end{array}t\left(\mathit{t\; \text{'}}\right)}{\mathrm{\Delta }\begin{array}{}\end{array}T\left(\mathit{t\; \text{'}}\right)}\right)}^{c=\mathit{const}\mathrm{,}}$$

with c positive, constant and chosen from the interval 0.5 to 1. The time intervals Δx (t ') = x (t1) -x (t2) are to be chosen large enough so as not to conflict with the noise of the measured values. Otherwise under unfavorable circumstances, this would cause the output value to be so violent that a controller would be very dependent on interference. T (t ') corresponds to the signal of the temperature sensor and t (t') corresponds to the time which is measured during the measurement.

Under certain circumstances, for example, after cooling off or during the cycle, it is possible that the slope underlying the initial value becomes negative. In order to avoid that mathematical problems occur during potentiation, in such cases the amount of the parenthesis can be used and in addition the sign of the value within the bracket can be included separately in the consideration. In this sense, the sign of the output value can be understood as a sign, which would result for the case c = 1.

In the context of the invention, it has been shown that the processing of the temperature signal detected in the course of time in accordance with the invention results in a very readily evaluable course in the aforementioned manner. This has relatively characteristic properties in its course and is also suitable for further evaluation. In particular, as described in detail below will be explained, certain characteristic events are well recognized.

It should be noted that for the output value, the fact that the temperature change is in the denominator of the output value makes such small changes very noticeable. This is especially true in cases where the temperature changes only slightly.

Advantageously, the exponentiation value is about 2/3, particularly advantageously exactly 2/3. In the context of the invention, it has been shown that with this exponentiation value, a particularly readily processable output value results, in particular with a fairly linear profile, which is advantageous for the evaluation.

Formally, the value of 2/3 for the exponentiation value results from a consideration of the dynamic course of temperature signals. Thus, consideration is given to the effect that a change in the temperature at a point, for example at the heating conductor, does not reflect directly at the sensor. Namely, the temperature signal takes a certain time to get from this point to the sensor and to heat it.

The value detected in the course of time can be interrogated electronically at the temperature sensor device. For this purpose, many different temperature sensors and measurement structures with such temperature sensors, which are known in the art.

The initial value obtained can be used, for example, to perform a cooking program on the hob as an electric cooking appliance, which runs at least partially automatically. Such a cooking program can cook a cookware and its contents to a desired Heat the temperature, for example bring water to a boil. For this purpose, the heating power can be selected as high as possible at the beginning to bring the water to a boil as quickly as possible. After reaching the boiling point at just under 100 ° C, the heating power can be reduced to save energy so far that just always this cooking point is maintained.

For example, it can be provided that upon detection of a drop in the initial value below a certain first limit, which may be, for example, almost zero, the power at the hob or at a certain selected cooking position of the hob, where the detected cooking process takes place, is reduced , This means that in this temporal behavior of the output value, a state has been detected, which sensibly entails a reduction of the heating power. For example, this may mean that the temperature does not rise any further, which means, in particular, reaching a cooking point of water. In other e-lektrokochgeräten such as an oven, the temperature on an introduced baking dish or the like. be measured.

As a further possibility, it can be provided that the output is reduced when the overshoot or undershooting of a second limit value is detected by the output value. Under certain circumstances, it can even be switched off for a certain time, because such a temperature behavior is caused, for example, by the fact that after the temperature has remained in a constant range, in particular at the abovementioned boiling point, the temperature rises again. This is a sign that a cookware contents or, for example, water in a saucepan is completely evaporated, whereby a further rise in temperature is possible and occurs. However, as this would lead to an unwanted and even dangerous overheating of cooking and cookware, which is absolutely avoided should be, after recognizing this condition the power is reduced or even switched off.

As a further possibility, it may be provided that a warning signal is emitted when the sign of the output value changes, or that the power at the cooking station is switched off with the monitored cooking process. In particular, the temporal course of the generated heating power is monitored for this purpose. For example, it can be detected whether a detected increase or decrease of the temperature coincides with the time course of the heating power or whether there is possibly an error in the temperature detection. For example, a detected increase in temperature at a time when no heating power is applied is considered to be an error in the temperature detection. This should be displayed to an operator or at least this hotplate of the hob should be turned off. In particular, when using radiant heaters with clocking operation and thus relatively easy determination of the generation of heating power, this is possible and advantageous.

In a further embodiment of the invention, the heat capacity of an empty hotplate or a hotplate without attached cookware may be known and stored in a memory of a corresponding control, as well as several hotplates or heaters. Starting from the initial value mentioned above, after a certain operating time, in particular a few minutes, the heat capacity of a heating device of the electric cooking appliance, for example as a hob, can be calculated. For this purpose, the introduced power is multiplied by the output value and this value is compared with the aforementioned stored value for the heat capacity. If the deviation exceeds or exceeds 10% or 15%, an inadmissible, possibly critical condition is detected and defined as such. As a result, a warning signal can be sent out and / or the power can be reduced at least at this cooking point, in particular it can be switched off. Such a change in heat capacity means that something has changed significantly on the cookware or that it has been taken from the cooking area. An aforementioned calculation of the heat capacity can also be performed several times during a cooking process. This is preferably done at regular time intervals. Likewise, a hotplate with reduced heat dissipation can be operated by, for example, a pot lid resting thereon or a hotplate with a well or poorly fitting pot or pan.

wobei die zugeführte Energie E aus der Leistung P, der Zeit t und dem Wirkungsgrad η berechnet werden kann. Die zeitliche Wärmekapazität erhält man durch Umstellen als $$C_p\left(\mathit{tʹ}\right)=\eta \begin{array}{}\end{array}P\left(\mathit{tʹ}\right)\frac{\mathrm{\Delta }\begin{array}{}\end{array}t\left(\mathit{tʹ}\right)}{\mathrm{\Delta }\begin{array}{}\end{array}T\left(\mathit{tʹ}\right)}\mathrm{.}$$

Formally, the heat capacity C _{p is} given as $$C_p\mathrm{\Delta }\begin{array}{}\end{array}T=e.$$

wherein the supplied energy E from the power P, the time t and the efficiency η can be calculated. The temporal heat capacity is obtained by switching as $$C_p\left(\mathit{t\; \text{'}}\right)=\eta \begin{array}{}\end{array}P\left(\mathit{t\; \text{'}}\right)\frac{\mathrm{\Delta }\begin{array}{}\end{array}t\left(\mathit{t\; \text{'}}\right)}{\mathrm{\Delta }\begin{array}{}\end{array}T\left(\mathit{t\; \text{'}}\right)}\mathrm{,}$$

It should be noted that the heat capacity refers to the entire system in the vicinity of the temperature sensor. The heat capacity determined in this sense thus depends on the sensor arrangement.

For the ideal case, that the temperature sensor was directly in the water bath of a cookware to be heated together with water as content, one would find approximately constant values until reaching the boiling point. In this ideal case, it would not be necessary to consider the dynamic properties mentioned above. As can be seen from the formulas, in this case the constant exponent for the formation of the initial value would be "1". Since this is not the case, the output value is chosen to be lower, just in the range around 2/3.

In a further embodiment, only the cooling of the temperature sensor, during which no power is supplied, are evaluated. Thus, a better evaluation is achievable.

It can be advantageously provided that cooling during a cycle operation of a cycle-operated heating device on the one hand and cooling as a result of a reduction of the power to the value "zero" on the other hand be treated in separate calculation methods. Due to the distinction, a precisely adapted calculation is possible in each case.

The absolute value of the temperature sensor can also be included in the evaluation. This is especially true when comparing with default values.

As a further independent aspect of the invention may be provided in an electric cooking appliance or a hob, that the entire electric cooking appliance or at least one hotplate of the hob can be operated in two modes. In a first so-called normal mode, any possible power change can be made. In a second so-called safety mode, an automatic operation of the cooking area or an automatically controlled, which is based on a prescribed cooking program with predetermined time sequences for the performance. In the context of this safety mode or the cooking program, the power can only be kept or reduced, at least there is no increase. This can only be done when an operator manually and deliberately deliberately intervenes, in which case advantageously the safety mode is terminated and is changed to normal operation. In this method, the result of an aforementioned temperature evaluation can be used with advantage. Thus, for an automatic operation it can be provided that the occurrence of critical states at least This is avoided or reduced by the fact that an increase in performance can not take place automatically.

Basically, the method described in this application, regardless of the type of heating on any types of heating transferable, for example, induction heating, heating with thin or thick-film heating elements or tubular heaters. Likewise, the method can be transferred to various electrical appliances, for example as an alternative to a hob on an oven or steamer.

These and other features will become apparent from the claims but also from the description and the drawings, the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into intermediate headings and individual sections does not limit the general validity of the statements made thereunder.

Brief description of the drawing

An embodiment of the invention is shown in the single drawing figure 1 and will be explained in more detail below, wherein Fig. 1 a schematic sectional view through a hob with a radiant heater and a temperature sensor represents.

Detailed description of the embodiment

In Fig. 1 is a hob 11 shown as electric cooking appliance. It has a hob plate 12, below which a conventional radiant heater is arranged as a radiant heater 14. On the hob plate 12 is above the radiant heater 14, a cookware 13 and a saucepan set up to bring its contents to a boil or to heat. On the underside of the hob plate 12, a temperature sensor S is mounted in the area above the radiant heater 14, for example, glued to the hob plate 12. Such temperature sensors are also known for the expected temperature range of up to about 630 ° C for the expert and it need not be discussed in detail. The temperature sensor S supplies the temperature T or a corresponding temperature signal to a controller 16.

The temperature sensor S is electronically interrogated, via the controller 16. This means that the temperature signal T is present in the controller 16 and can be further processed. This further processing takes place in a prescribed manner in that the temperature signal T is differentiated according to the time. This result is inverted and the result of the inversion is raised to 2/3. This results in an initial value A, or the like for further evaluation activities and / or performing a cooking program. is used. He is also advantageous because he has a reasonably linear course. Changes can be recognized very well.

Certain events that may occur on a hob 11, such as maintaining a maximum temperature upon reaching the boiling point of water or emptying a cookware, and a concomitant re-rise in temperature, are generally known, and the temperature profiles obtained thereby as well. If these characteristic temperature curves are now taken from the hob 11 and the resulting curves of the above-determined output value in the controller 16 or an associated memory, not shown, are stored, then the output value determined in one operation can be used A be compared with it. If, owing to the current course of the initial value, it is possible to recognize a known pattern from the store or correspond to a known pattern, for example for reaching the boiling point of water in the cookware 13, the controller 16 can produce the result evaluate that just boiling water in a set up on the hob 11 cookware 13. On this basis, for example, as part of a corresponding cooking program, the performance can be reduced somewhat. The power reduction can be carried out so that, although less power is generated by the radiant heater 14, but the temperature does not or only slightly below 100 ° C drops. This can also be done via the evaluation by means of the temperature sensor S and the temperature signal T and its associated output value after conversion according to the invention.

The other options described above, run with the controller 16 a cooking program or warning signals or the like. give and other signals are known to the skilled person, in particular from the aforementioned prior art documents. In this respect need not be further discussed here.

Advantageously, the controller 16 also monitors the power supply to the radiant heater 14. Thus, by detecting the time profile of the supplied electrical energy, a plausibility check with respect to the generated temperature profile or the detected temperature level at the temperature sensor S done. If, for example, no or only a very small heating power is generated by the radiant heater 14 at a certain point in time, but the temperature at the temperature sensor S increases, then a fault condition must be present. This is especially true when the temperature at the Temperature sensor S is so high that it can be generated only by operation of the radiant heater 14 and not by, for example, setting up a very hot cookware on the hob plate 12 above the temperature sensor S. Here then a warning signal can be issued or possibly the radiant heater 14th or the entire hob 11 are turned off. In this case, either there is a fault in the radiant heater 14, the controller 16 or at the temperature sensor S. Each of these sources of error is relatively serious, which is why a shutdown should take place.

This in Fig. 1 shown system, together with the set up cookware 13, the system whose heat capacity can be calculated in the aforementioned manner. This is then compared with the same system without placed cookware 13, so to speak, as an empty hob.

In the controller 16 and the aforementioned safety mode can be realized. If a prescribed automatic operation is carried out here, for example by a prescribed cooking program being carried out, then the electric power for the radiant heater 14 can be kept or reduced by the controller 16. However, it can not be increased in any case, so that overheating in case of malfunction of the temperature detection via the temperature sensor S is avoided. By preventing the increase of the power in the automatic mode, high safety can be ensured.

Claims (15)

1. A method of generating, processing and evaluating a signal correlated with the temperature at an electric cooking appliance when the electric cooking appliance is in the operating state, the temperature of the electric cooking appliance, of a cooking vessel (13) standing thereon and/or of the contents contained in the cooking vessel being detected by a temperature sensor device (S), characterised in that the temperature signal (T) detected by the temperature sensor device over time is differentiated once as a function of time, the result is inverted and then the result of the inversion is raised to an exponent of between 0.5 and 1.0 in order to obtain an initial value, this initial value being taken as the basis for further processing and evaluation.
2. A method according to claim 1, characterised in that the exponent is between 0.6 and 0.8, with it amounting in particular to approx. 2/3, preferably precisely 2/3.
3. A method according to claim 1 or claim 2, characterised in that the temperature sensor device (S) is interrogated electronically, preferably with a control means (16).
4. A method according to any one of the preceding claims, characterised in that a cooking program proceeding at least in part automatically is performed on the electric cooking appliance (11), this making use of the initial value.
5. A method according to any one of the preceding claims, characterised in that, if the initial value is identified as having fallen below a predetermined first limit value or having risen above the predetermined first limit value, the power is reduced at the electric cooking appliance (11) or at a given cooking zone or heating device (15) of the electric cooking appliance at which the temperature sensor device (S) is provided, the predetermined first limit value in particular being virtually zero.
6. A method according to any one of the preceding claims, characterised in that, if the initial value is identified as having exceeded or fallen below a second limit value, the power is reduced, preferably is switched off for a given time.
7. A method according to any one of the preceding claims, characterised in that, in the event of a change in the sign of the first derivative of the temperature as a function of time, a warning signal is emitted and/or the power is switched off at the cooking zone having the temperature sensor device (S).
8. A method according to any one of the preceding claims, characterised in that the thermal capacity or thermal capacities of the cooking zone or cooking zones or heating devices (14), preferably an empty cooking zone, a cooking zone with reduced heat emission and/or a cooking zone with a saucepan (13) or frying pan resting well and/or poorly thereon, are known to the temperature sensor device (S) and stored therein, the thermal capacity being calculated, on the basis of the initial value after a given operating time of a cooking zone or heating device (14) of the electric cooking appliance (11) having a temperature sensor device (S), by multiplying the power introduced by the initial value, said value being compared with the stored value for the thermal capacity of the cooking zone, a warning signal being emitted and/or the power being switched off in the event of an upwards or downwards deviation greater than 10%, calculation of the thermal capacity preferably being performed repeatedly during a cooking procedure, preferably at regular time intervals.
9. A method according to any one of the preceding claims, characterised in that a temperature increase or decrease is monitored and compared with the power supplied to the cooking zone or heating device (14), the cooking zone or the entire electric cooking appliance (11) being switched off and/or a warning signal being emitted if the detected temperature deviates significantly from the power supplied.
10. A method according to any one of the preceding claims, characterised in that only cooling of the temperature sensor (S) is evaluated, no power being supplied during this time.
11. A method according to any one of the preceding claims, characterised in that cooling during cyclic operation of a cyclically operated heating device (14) and cooling as a consequence of a reduction in power to the value "zero" are processed in separate calculation procedures.
12. A method according to either one of the two preceding claims, characterised in that the absolute value of the temperature sensor (S), in particular on comparison with predetermined standard values, is also included in the evaluation.
13. A method of operating an electric cooking appliance or a hob (11), characterised in that the electric cooking appliance (11) or a heating device (14) or cooking zone thereof is operated according to two different modes of operation, wherein in a first, normal mode any possible power modification may be made and in a second, safety mode the heating device is operated automatically with a cooking program, the cooking program allowing merely for the power to be maintained or reduced, without any increase.
14. A method according to claim 13, characterised in that it is performed using the result of a temperature evaluation by a method according to any one of claims 1 to 12.
15. A device for processing and evaluating a signal correlated with the temperature at an electric cooking appliance or hob (11) when the electric cooking appliance is in the operating state, for carrying out the method according to any one of the preceding claims, having a temperature sensor device (S) for detecting the temperature of the electric cooking appliance or the heating device (14) thereof, of a cooking vessel (13) standing thereon and/or of the contents contained in the cooking vessel, characterised by a sensor signal processing means or a control means (16) for detecting the profile over time of the temperature signal (T) of the temperature sensor device (S), for differentiating the temperature signal once as a function of time, for inverting the result and subsequently raising the result of the inversion to an exponent of between 0.5 and 1.0 for an initial value, for further processing and evaluation of said initial value.

Images