WO2009112150A2

WO2009112150A2 - Method and device for controlling a cooktop

Info

Publication number: WO2009112150A2
Application number: PCT/EP2009/001314
Authority: WO
Inventors: Wolfgang Thimm
Original assignee: E.G.O. Elektro-Gerätebau GmbH
Priority date: 2008-03-04
Filing date: 2009-02-25
Publication date: 2009-09-17
Also published as: WO2009112150A3; DE102008014268A1

Abstract

The invention relates to a method for controlling a cooktop (11) having an empty burner detector as a protection against an empty burner at a cooking location, wherein the temperature of the cooking location (14) is detected. For the empty burner detector, exceeding a specific limit value for temperature increase at the cooking location (14) within a short time causes the power to be switched off. After each switch procedure or operation of the cooktop (11), a timer (18) is started again in a cooktop controller (17) and, depending on the elapsed time captured by the timer (18) since each start thereof, the limit value for temperature increase is modified such that as the time increases, the limit value is reduced for the temperature increase for triggering the empty burner detector by switching off the power.

Description

Description Method and device for controlling a hob

Field of application and state of the art

The invention relates to a method for controlling a hob, wherein the hob has a empty cooking detection as empty cooking protection at a cooking point of the hob, and a trained for performing the method device.

It is known from EP 1 028 602 A1 and EP 1 768 461 A1 to monitor a temperature at a hotplate of a hob. This is mainly a so-called empty cooking protection is to be achieved, it should therefore be established and prevented that a potted pot is completely evaporated with liquid or is empty and then an inadmissibly strong or large temperature increase takes place at the hob. In this case, both the cooking pot and the hob or a glass ceramic plate of the hob damage take, which is prone to temperatures of 500 ⁰ C and more.

Task and solution

The invention has for its object to provide an aforementioned method and an aforementioned device for its implementation, with which problems of the prior art can be avoided and in particular a both reliable and practical embryo protection is achieved.

This object is achieved by a method with the features of claim 1, 2 or 10 and an apparatus for its implementation with the features of claim 12. Advantageous and preferred embodiments of the invention are the subject of further claims. and will be explained in more detail below. The wording of the claims is incorporated herein by express reference. Furthermore, the wording of the German priority application DE 102008014268.9 of March 4, 2008 of the same Applicant is incorporated by express reference into the content of the present description.

According to the invention, it is provided that the temperature at the cooking point is detected in a manner known per se. In empty cooker detection, exceeding a certain temperature rise threshold within a short time, for example 4O ⁰ C more within a one minute rise time, at the cooking surface results in a reduction in power or even a power cut. After each switching operation or after each operation on the hob by an operator, a present in a cooktop control timer is restarted and counts from this time the elapsed time. Depending on this elapsed time, the limit value for the temperature rise is changed so that, with increasing elapsed time, the limit value for the temperature rise leading to the triggering of the idle power detection with power cut becomes lower. In particular, the limit value for the temperature rise is changed so that at the same time leading to the power reduction or power-off temperature difference is lower or a lesser increase in temperature sufficient for power reduction. The hob control is an electronic control and not electromechanical.

Thus, it is possible with the invention that, as it were, any operation on the hob is interpreted as a sign and used that an operator is present and would notice a possibly critical or inadmissible or unwanted state on the hob or a cooking area. Shortly after such by a operation of the operator, a relatively high limit is required for the temperature rise, which leads to activation of the empty cooking protection. So this means that the temperature must be relatively high increase within a given short period of time, for example, the aforementioned 4O ⁰ C within a minute or half a minute to activate the no-boil protection. After all, the operator is with a certainty yes still near the hob. If, on the other hand, a certain amount of time has elapsed since the last operating procedure, for example 15 minutes, it does not matter which cooking station has been operated, then it is more likely that an operator is no longer directly involved in the operation of the cooking field and thus possibly also already no longer close to the hob. Then even a lower limit, for example, 2O ⁰ C, that this temperature increase activated within the said very short time, the empty cooking protection. Still more time passes, for example, 30 minutes or even more, so this limit will be reduced further, for example to 1O ⁰ C as a temperature rise within the very short time to activate the empty burner protection.

Thus, the invention for better embryo protection, the recognition that usually with still running on the hob cooking operations, an operator is at least not too far away from the hob or over again makes a changed setting and thus their presence can be determined. In this context, as an operating procedure, a touching of the pot by lifting the lid to check the contents of the pot could also be considered as an operating procedure, as is known for example from DE 10 2004 059 822 A1 or DE 10211047 A1, whose content is hereby incorporated by express reference is made to the content of the present description. In other words, can be exploited with the invention that each time when the presence of an operator can be reliably determined by an operation, the limit for the temperature rise is set high again and is reduced again over time. The present operator would notice an empty cook, and thus this risk is lower.

Furthermore, it can be provided in an embodiment of the invention that a so-called unclear or critical state of the cooking area is defined by the fact that in this unclear or critical state, the temperature rise is close to the limit value, but has not yet exceeded. In this case, an unclear state of the invention may be provided in a development that the timer continues to run and at the same time the hotplate is significantly reduced in their performance. If there is still a so-called normal cooking process, in which there is still water in a saucepan on the cooking surface of the hob, so this reduction in temperature, the temperature rise is significantly lower or the temperature remains the same or even drops. If, on the other hand, empty-cooking is imminent or has even begun, the temperature increase continues to rise sharply despite the power reduction and exceeds the limit value, so that empty-cooking protection is then rightly activated. Thus, this power reduction in unclear state serves to clarify the state in one direction or the other. In this case, it can be advantageously provided that, as the past time counted by the timer increases, the power reduction in the event of an unclear state is greater. In this way, as described above, the fact is taken into account that after a long counted time of the timer, the probability is correspondingly high that an operator is no longer present. Conversely, it can also be said that with only a little time in the past, there is a high probability that an operator will still be present. In a further basic embodiment of the invention can be provided that the power reduction is changed such that with increasing time the power reduction is increased when the limit is exceeded. The power reduction may be combined with or alternatively provided with the aforesaid reduction of the threshold value leading to the triggering of the cookie detection.

In a further embodiment of the invention, the detection of a previously described unclear or critical condition on the one hand and a shutdown of the cooking area after recognizing an empty cooking on the other hand visually and / or acoustically be indicated by a signal. It is possible to distinguish by signaling the unclear state on the one hand from the shutdown of the hob on the other. This is on the one hand by an optical signal display well possible, for example, can be displayed for a long time and by blinking or the like. Can give information. Furthermore, acoustic signals are also considered to be advantageous because they attract the attention of an operator even at a slightly greater distance from the hob, for example in another room. Signals can be changed over time, for example become stronger, especially if they are not noticed or if they cause no reaction. It can further be provided that during a certain time interval, the power remains unchanged when the limit value is exceeded, and instead only an acoustic and / or optical signal is emitted.

In yet another embodiment of the invention, a single timer is provided on the hob, which is integrated in particular in the hob control. It is just restarted by any switching operation or operation on the hob, for example se also by the above-mentioned touching a saucepan. Under certain circumstances, the timer may also consider the absolute duration of a cooking process for the formation of the limit. Shortly after the start of a cooking process, the risk of emptying can still be great, for example, when a pot has been put on empty. Then the danger is initially lower again, and then rise again after a few minutes, when a previously filled pot could be cooked empty.

In a further embodiment of the invention, it is possible that after detecting an unclear or critical condition or a power reduction at a cooking position of the hob, other cooking zones of the same hob are reduced in their performance. Thus, an occurrence of such a condition can be prevented at another hotplate, even if it is actually not yet critical in this. In yet another embodiment of the invention can be provided after switching off a hotplate due to a recognized empty cooking in the context of the empty cooking protection that also more, especially all, cooking zones of the same hob are reduced in their performance. Particularly advantageous they are even turned off or the entire hob is turned off. A prescribed signal display should still work. Even so, the overall reliability of the hob can be increased.

As has been stated above, the temperature rise may be as a threshold value in dependence on an elapsed time after 3 minutes, about 4O ⁰ C, after 15 minutes about 2O ⁰ C and after 30 minutes about 1 O ⁰ C. In still a long time, the limit value should but not or only slightly below 1O ⁰ C fall. Furthermore, the said very short time within which this limit value for the temperature rise must be exceeded in order for the empty cooking protection to be activated to lie at one minute, possibly even present, may advantageously take place. under, for example, at 20 to 30 seconds. Instead of changing the limit for the temperature rise, this time can be extended, which has similar effects on the value for the temperature rise.

In a further development of the invention it can be provided that during the temperature fluctuations not the complete course of the temperature itself is observed, but an increase of the temperature profile. With increasing time after starting the timer, a smaller slope of the temperature curve is sufficient to cause the above-described reducing or switching off the power of the cooking area as empty cooking protection. Thus, the limit value for the temperature rise, which is measured as the temperature difference within the predetermined very short time, is replaced by the value for the slope of the temperature curve.

In a further basic embodiment of the invention can be provided that the hob has a empty cooker detection as empty cooking protection at a hob of the hob, the temperature is detected at the hob. After each switching operation on the cooktop, a timer is restarted in a cooktop control, and depending on the elapsed time detected by the timer after its respective start, the value for the glass-ceramic limit temperature of a cooktop panel of the cooktop of the cooktop is changed in such a way that the value for the glass-ceramic limit temperature is lowered as time goes on. Thus, too high a temperature can be avoided on the glass ceramic and especially on the pot.

In addition, it is possible to detect the mains voltage and / or a heating current through a heater of the hob. From this, the heating power can then be determined. Temperature changes will be then compared with changes in performance on the radiator. Such comparisons can significantly increase the stability of the system to interference. If it is unclear whether a temperature increase results from a power increase or an actual empty cooking, an increase in capacity is more likely to be assumed for shorter times, and a higher degree of probability is assumed for longer times and correspondingly reacted accordingly.

These and other features will become apparent from the claims but also from the description and drawings, wherein 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 individual sections and subheadings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Embodiments of the invention are shown schematically in the drawings and will be explained in more detail below. In the drawings show:

1 is a schematic sectional view through a hob with a radiant heater, a temperature sensor and a controller including timer,

2 a simulated temperature profile with an empty cooking of a pot after about 60 minutes,

3 shows the first derivative of the temperature profile from FIG. 2, FIG.

4 shows a modification of the temperature profile from FIG. 2 with simple disturbances at intervals of approximately 10 minutes, FIG. 5 shows the first derivative of the temperature profile from FIG. 4, FIG.

FIG. 6 shows the second derivative of the temperature profile from FIG. 2, FIG.

7 shows the second derivative of the temperature profile of FIG. 4,

8 shows a course of the inverted derivative of the temperature profile from FIG. 2, and FIG. 9 shows the inverted derivative of the temperature profile from FIG. 4.

Detailed description of the embodiments

In Fig. 1, a hob 11 is shown as Elektrokochgerät. It has a hob plate 12, in particular of glass ceramic, below which a heater 14 is arranged in the form of a conventional radiant heater. On the hob plate 12, a pot 13 is placed above the heater 14 to heat its contents or bring to a boil. On the underside of the hob plate 12, a temperature sensor 15 is mounted in the region of the heater 14. Such temperature sensors are also known to the person skilled in the art Temperature ranges from a few 100 ⁰ C up to 800 ⁰ C. The temperature sensor 15 detects the temperature and passes it on to a controller 17, where it is electronically queried about this. This means that the temperature signal T is present in the controller 17 and can be further processed. This further processing can be carried out, for example, in particular according to EP 1 768 461 A1 and also according to DE 10 2006 057885 A1, to which reference is expressly made with regard to this further processing and the content of which is hereby incorporated by express reference into the content of the present description.

In the controller 17, a timer 18 is still arranged or provided. In addition, the controller 17 is schematically connected to the heater 14 to reduce or shut down their power, which is usually done via corresponding circuit breakers. Furthermore, the controller 17 is connected to or controls an LED 20, which is also arranged below the cooking plate 12. A lighting effect of the LED 20 is, as shown, through the hob plate 12 visible therethrough.

FIGS. 2 to 9 show temperature profiles, discharges and curves further processed in FIGS. 8 and 9, which have been determined on the basis of the temperature profiles. As described above, it is desired on the one hand, so-called empty cooking, so if a content of the pot 13, for example, water is evaporated as quickly as possible to detect, so that the power of the heater 14 can be reduced or turned off, so that no harmful excess temperature at the Hob plate 12 and the pot 13 may occur. On the other hand, malfunctions should be detected and hidden, so that the cooking process is interrupted or terminated only in an emergency. From the temperature profile according to FIG. 2, it can be seen that the temperature at the temperature sensor 15 rises sharply in the first minutes of the cooking process, and then always weaker, until it increases only slowly and gradually from about 20 minutes. At about 60 minutes, a sharp rise in temperature is again detectable, which means that at this time the pot 13 is cooked empty and therefore the temperature rises noticeably strong. Usually, in the case of a hob, a so-called bar regulator is provided as over-temperature protection, above all for the hob plate 12, which is arranged at a short distance below it. However, this rod regulator is only provided for controlling the temperature of the glass ceramic of the hob plate 12. The temperature of the cookware could thus still increase significantly, up to the limit temperature of the glass ceramic, which could destroy the cookware or even be dangerous for the user.

However, such a rod regulator is not always fast enough to detect a rapid and sharp increase in temperature in the case of emptying, and then to turn off the heater 14 power. Above all, he can give no feedback as to whether there is generally too high a temperature or whether the case of empty cooking is present in particular.

A further general embodiment of the method according to the invention is that the temperature of the sensor, which is adjusted to protect the glass ceramic from too high a temperature and a consequent damage, namely the so-called glass ceramic limit temperature, is reduced with increasing time.

In Fig. 3, the first derivative of the temperature profile of Fig. 2 is shown. Here is by the very strong increase in the slope of the temperature curve just before 60 minutes, ie when emptying, this case of Empty cooking actually very well recognizable. On this basis, then the heater 14 could be reduced in power or switched off. It is assumed, however, that according to FIG. 2, the temperature profile is very uniform and, above all, can be detected very well and evenly. However, this is often not the case in reality, because during operation of the heating device 14, the temperature profile may exhibit fluctuations or small disturbances or glitches. Reasons for such disturbances can be varied, for example clocking heaters at the same or an adjacent phase, mains voltage fluctuations, coupled Störinduktionen, temperature susceptibility of components and much more.

Such a temperature profile with glitches at intervals of 10 minutes is shown in Fig. 4. The glitches are placed on a temperature profile corresponding to that of FIG. The problem arising from this is very clear when looking at the first derivative in FIG. 5 of the temperature profile according to FIG. 4. The interference peaks also lead to a short-term sharp increase in the course according to FIG. 5 or the gradient. At the same time, these glitches, which do not signify emptying yet, are not yet intended to reduce the heating power at the heating device 14.

In Fig. 6, the second derivative of the temperature profile of Fig. 2 is shown. Here, too, the case of empty cooking is recognizable by the strong increase. However, as is clear from Fig. 7 with the course of the second derivative of the temperature profile of the disturbances of FIG. 4, such interference in the second derivative affect much more, so this actually does not represent a sufficiently good method for detecting an empty cooking.

FIG. 8 shows a further processing of the temperature profile of FIG. 2, similar to the aforementioned EP 1 768 461 A1, in which the method of FIG. 2 is differentiated once by time, which then results in the course of FIG. 3. This result is then inverted, but then no longer potentiated. The simulation assumes a simple In t behavior. Similarly, the trajectory can be easily calculated, since the 1st derivative of the In t is a 1 / t law, the 2nd derivative is -1 / t ^2, and the inverse of the 1st derivative is simply a linear increase with t.

The case of empty cooking at about 60 minutes can be clearly recognized by the very sharp drop in the curve. However, here too, the illustration of FIG. 9, which, similar to FIG. 8, has been determined from the temperature profile with glitches according to FIG. 4, shows that the glitches likewise have a very harmful effect again. As with the first derivatives of the temperature profile according to FIGS. 3 and 5 or the second derivative according to FIGS. 6 and 7, empty cooking can only be recognized a few minutes after the occurrence of the change in the curve. In FIG. 5, only if the course of the first derivative drops again after the steep rise and then possibly rises again, one would be able to recognize that there is a disturbance here and no emptying. However, since it can not wait a few minutes each time for this detection, this is problematic. The same applies to an evaluation of the courses according to FIGS. 6 and 7 as well as according to FIGS. 8 and 9.

According to the invention, in order to classify the time which can be left until a decision as to whether or not there is empty cooking, depending on a situation that is likely to be present, it can be changed as the duration of a cooking process progresses. At the beginning of a cooking process, so in Fig. 2 even further left, one can leave a little more time to observe a temperature rise and just then to determine as borderline high within a certain time. Takes a cooking process For some time, for example 60 minutes according to FIG. 2 or even longer, so is the given absolute temperature on the hob plate 12 already higher, so that a lower limit for a temperature increase within a short time must be used. Further, after such a long time, the likelihood that a pot 13 set on the heater 14 is empty is larger at the beginning of a cooking process.

For this reason, it is shown in Fig. 2, as over time, this threshold of initially above 4O ⁰ C temperature rise to 1O ⁰ C at 30 minutes drops, and then strives for an exemplary value of about 8 ⁰ C for very long cooking times. This may be the limit value for a temperature increase within a time of one minute, which causes a shutdown as measured on the absolute temperature profile according to FIG. 2 or then also according to FIG. 4 with glitches. Time is always the last operation or how much time has passed since the last operation.

Claims

claims

1. A method for controlling a hob (11), wherein the hob (11) has an empty cooking detection as empty cooking protection at a cooking position (14) of the hob, wherein the temperature is detected at the cooking surface and the empty cooking detection exceeding a certain limit for the Temperature increase within a short time at the cooking surface for power reduction or power cut leads, wherein after each switching operation or operation on the hob (11) a timer (18) is restarted in a hob control (17) and depending on the past time, the the timer is detected after its respective start, the limit value for the temperature rise is changed such that, with increasing time, the limit value for the temperature rise leading to the triggering of the empty cooker recognition with power shutdown becomes smaller.

2. A method for controlling a hob (11), wherein the hob has a empty cooking detection as empty cooking protection at a cooking position (14) of the hob (11), wherein the temperature is detected at the cooking surface and in the empty cooking detection exceeding a certain limit for the Increase in temperature within a short time at the cooking surface for power reduction or power shutdown, wherein after each switching operation or ßedienvorgang the hob (11), a timer (18) is restarted in a hob control (17) and depending on the past time, the the timer (18) has been detected after its respective start, the power reduction is changed such that with increasing Over time, the power reduction is increased when the limit is exceeded.

3. The method of claim 1 or 2, characterized in that in addition an optical and / or acoustic signal display (20) is activated upon detection of a critical or unclear state or when switching off the cooking surface (14) after detecting an empty cooking, wherein preferably warning tones are changed or intensified at intervals.

4. The method according to claim 2 and 3, characterized in that during a certain time interval, the power remains unchanged when the limit value is exceeded and an acoustic signal is emitted.

5. The method according to any one of the preceding claims, characterized in that per hob (11) a single timer (18) is provided, which is restarted by any switching operation or operation on the hob.

6. The method according to any one of the preceding claims, characterized in that after detecting a critical condition and / or consequent reduction in power at a cooking point (14) of the hob (11) other cooking zones of the same hob are reduced in their performance.

7. The method according to any one of the preceding claims, characterized in that after switching off a hotplate (14) due to a recognized empty cooking more hotplates of the same hob (11) are reduced in their performance, preferably switched off, in particular the entire hob (11) is switched off.

8. The method according to any one of the preceding claims, characterized in that after a past time of 3 minutes, a temperature increase by 4O ⁰ C, after 15 minutes elapsed time, a temperature increase of 20 ° C and after 30 minutes elapsed time, a temperature increase of 10 ° C. , in each case within 1 minute, a shutdown of the hotplate (14) causes.

9. The method according to any one of the preceding claims, characterized in that at the temperature fluctuations, a slope of the course of the temperature is observed and with increasing time after starting the timer (11) a lower slope of the temperature curve is sufficient for reducing or switching off the power of the cooking area ( 14).

10. A method for controlling a hob, wherein the hob has a empty cooking detection as empty cooking contactor at a cooking point (14) of the hob (11), wherein the temperature is detected at the cooking surface, wherein after each switching operation or operation on the hob a timer ( 18) is restarted in a cooktop controller (17) and, depending on the elapsed time detected by the timer (18) after its respective start, the value for the glass-ceramic limit temperature of a cooktop ceramic cooktop panel (12) (1 1) is changed such that with increasing time the value for the glass ceramic limit temperature is lowered.

1 1. A method according to any one of the preceding claims, characterized in that in addition the mains voltage and / or a heating current by a heating device (14) of the hob (11) is detected.

12. Apparatus for carrying out the method according to one of the preceding claims for controlling a hob (11).