EP2857753A1 - Pot detection method and detection - Google Patents

Abstract

In a method for pan detection of a set up on a cooking pot with a reflex light barrier sends a light emitter light to the pot, the pot reflects the light and it is received by the light receiver, the emitted light is modulated with at least three frequencies. In a pan detection control it is checked at how many frequencies of the light emitter the light receiver receives reflected light signals of the light emitter, a pot being detected as placed only if at least two out of three frequencies or more than half of the number of emit frequencies Light receiver detects light signals from the light transmitter.

Description

Field of application and state of the art

The invention relates to a method and a device for pot detection of a set up on a cooking pot with a reflex light barrier. Such an optical pot detection can serve to increase the operational safety, so that, for example, a hotplate is switched off when the pot has been removed too long, whereby the term pot means any upright cooking vessel or even a pan.

From the US-A-5658478 and the EP 1094688 B1 It is known to quasi optically perform a pot detection at a hotplate with a light transmitter and a light receiver. This works on the principle of a reflex photoelectric sensor and it will be used per cooking area or per pot to be recognized in each case exactly one light emitter and a light receiver, which are assigned to this hotplate. The light receiver serves to detect the light emitted by the light emitter and sent back or reflected by an attached pot or light and to appreciate this recognition as recognizing an attached pot.

Task and solution

The invention has for its object to provide an aforementioned method and an aforementioned device with which problems of the prior art can be avoided and it is particularly possible to perform an optical pot detection with the lowest possible component complexity with high reliability and reliability of pot detection as well as detection and elimination of disturbances.

This object is achieved by a method having the features of claim 1 and a device having the features of claim 14. Advantageous and preferred embodiments of the invention are subject matter of further claims and are explained in more detail below. Some of the features are mentioned only for the method or only for the device. However, they should be able to apply independently for both the method and the device independently. The wording of the claims is incorporated herein by express reference.

It is envisaged for the method and for the device that a reflex photoelectric sensor can be provided at the cooking point or under the cooking position, as for example from the German patent application DE 102013218950.8 the same applicant with the filing date of 20 September 2013. The reflex light barrier has a light transmitter and a light receiver. A light emitter emits light or a light signal to the pot or to the cooking area and to the pot, which is placed on the cooking area. The pot in turn reflects the light or light signal, which is then received by the light receiver. In this case, between the light emitter and light receiver on the one hand and pot or hob on the other hand are a greater distance and in particular may be provided therebetween light guide, as described in the aforementioned patent application of the same Applicant. The emitted light or light signal of the light emitter is modulated with at least three frequencies. It may also be more to increase the immunity to interference or reliability, as will be explained below. In a control of pan detection or the cooking area or a hob to which the hotplate belongs, it is checked at how many frequencies of the light emitter, the light receiver receives light signals from the light emitter, which have been reflected. A pot is only recognized as being set up if at least two frequencies and / or if at least half of the number of emitted frequencies, preferably more than half the number of emitted frequencies, the light receiver clearly recognizes the light signals of the light transmitter. In addition to this, the phase position of the light signals can also be checked or compared between the light transmitter and the light receiver, preferably evaluated by a lock-in filter which is explained in more detail below. In this case, the reflected light signal received by the light receiver, ie the frequency and phase-identical signal, is evaluated as a valid and positive response only with the same phase position and the same frequency. Thus, a pot is only considered set up or is recognized accordingly, if returned in several checks a correct and expected signal. Of course, the number of frequencies could be further increased, so that both the effort in the evaluation and the duration is negatively increased. In this case, a threshold can preferably be defined, above which an information "pot set up" is generated. For this purpose, for example, a DC signal formed in a lock-in filter consisting of phase angle and frequency can have a deviation of less than 10%, advantageously less than 5%, from the nominal value. To increase security this can be set to 2% or 1%.

In an advantageous embodiment of the invention, the number of frequencies is increased, for example, four frequencies or five frequencies for the modulation of the emitted light or the emitted light signals. It can be advantageously provided that a Pot is only recognized as placed when at least three frequencies of the light receiver detects light signals of the light transmitter with the above evaluation or threshold.

In an embodiment of the invention, a digital filter with the principle of a lock-in amplifier can be used in the evaluation of the light receiver, ie an aforementioned lock-in filter. So you can achieve a very flanking bandpass filter, which allows a sharp separation.

In an advantageous embodiment of the invention, the light transmitter transmits at least partially, preferably exclusively, light signals in the IR frequency range. This has the advantage that it is not visible to an operator and thus is not annoying or confusing. Furthermore, all visible light sources can not actually cause any interference. By appropriate choice of the frequencies of the IR light emitter, interference signals that could emanate from IR remotes or lighting means can be suppressed. Likewise, infrared light components without modulation content, which originate from the hotplate of hot parts or from the pot, can be suppressed.

Ideally, modulation of a light signal is generally sinusoidal. For pot detection, however, a rectangular modulation of the light signals which are emitted by the light emitter is advantageously preferred. As a result, on the one hand a power-saving control of the light transmitter is possible. Furthermore, a simpler control is possible because virtually the light transmitter only has to be switched on and off.

A driving or switching on and off of the light emitter is advantageously carried out by means of an electrical or mechanical switch, preferably by means of a transistor or bipolar transistor, particularly advantageously by means of a MOSFET transistor.

It is possible to generate the reference signal of the lock-in filter, which is phase and frequency equal to the modulated light signal, in the same rectangular shape. As a result, digital signal processing in a microcontroller of a control of the pot detection or the hotplate or a hob can be considerably simplified.

However, a rectangular modulation of the light signals has the disadvantage that when multiplied by a sinusoidal reference signal, the signal strength is weakened. With regard to the selectivity of the lock-in filter, there is the disadvantage of a rectangular reference signal with regard to reduced suppression of harmonic interference frequencies. This can be avoided by generating instead of the rectangular reference signal a phase and frequency equal sinusoidal reference signal in the lock-in filter. Thus, even if increased noise immunity is required, the harmonic interference can be suppressed. By sampling only a few periods of the signal frequencies, the frequencies emitted by the emitted light signal can also be filtered only to a limited extent. If an interferer now has the same frequency as the light signal and its amplitude is on the order of a valid or expected reflected light signal, the controller can not distinguish this from the actual light signal. Although no pot is set up, which is why the interfering signal in most cases can even reach the receiver at all, there still seems to be a reflected light signal here. This makes a safe pan detection difficult and should just be compensated by the use of multiple frequencies. Namely, if multiple frequencies used or multiple light signals, preferably in the manner of packets, with different frequency using the light emitter, the reference frequency of the lock-in filter is adapted to the respective frequency of the light emitted from the light transmitter light signal, so a disturber with Nevertheless, a constant frequency can be eliminated. It sends its signal only at one frequency, so that at this frequency possibly a seemingly valid answer comes back. Since, however, in fact no pot is set up, there is very probably no valid answer for the other frequencies, so that the disturber can be recognized.

In a general embodiment of the invention, it may be systemic that the signal level of the lock-in filter decrease with increasing signal frequency. This is because the signals usually become weaker. Furthermore, the introduction of n individual limit values in generating or using n signal frequencies for the light signals can make sense here.

It is of great advantage if these frequencies in Hz of the emitted light signals are not an integer multiple of one of these frequencies. Thus, errors can be excluded by harmonics.

At three frequencies for the light signals, two valid and positive responses can be considered to have a pot set up. Since, however, if this case is actually present, a disturbing influence is usually rather low, this state is relatively easy to discover. It is actually more difficult to say with certainty that there is no pot, but it should be noted that only one of the two conditions can exist. At the same time, possible consequences are more serious if a pot is considered to be set up, although not true. If the pot is not set up, for example, the cooking area will not be switched on. Although this is annoying for an operator, but may be transferred by moving the pot in a correctly recognized state under certain circumstances. If, on the other hand, a pot is evaluated as recognized, then the hotplate can be operated, for example. In the best case, it is only an unnecessary waste of energy, but it has major consequences if an unexpected danger for the operator occurs through a heated cooking area or, for example, through open gas flames of a gas hob.

The device for carrying out the method has at least one light transmitter, at least one light receiver and a controller for controlling them. Likewise, the controller evaluates the light receiver or carries out, for example, the above-mentioned comparison between the light signals emitted by the light transmitter, which it knows about its control, and the light signals received by the light receiver. A device may, for example, the aforementioned DE 102013218950.8 be removed.

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-combination in one embodiment of the invention and in other areas be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections as well as intermediate headings does not restrict the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1

eine schematische Schnittdarstellung eines Kochfelds mit mehreren Kochstellen und mit Reflex-Lichtschranken zur Topferkennung und

Fig. 2 bis 4

verschiedene Auswertemöglichkeiten für Signale am Lichtempfänger.

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

Fig. 1

a schematic sectional view of a hob with multiple burners and with reflex photoelectric sensors for pot detection and

Fig. 2 to 4

Various evaluation options for signals at the light receiver.

Detailed description of the embodiments

In Fig. 1 an inventive hob 11 is shown with hob plate 13, on which a device 12 according to the invention is provided for pot detection. Here, four hobs KS ₁ to KS _{4 are} provided, each with possibly four pots T ₁ to T ₄ thereon. The device 12 has four light-guiding means L ₁ to L ₄ . Each light guide L has two optical fibers, which each go to one of the light emitter S ₁ or S ₂ or light receiver R ₁ or R ₂ . The light guides are provided with end pieces E towards the cooking point KS and toward light transmitters S and light receivers R with connectors V. The end pieces E each have only a single light guide, while two light guides are led into a connector V.

Concretely, the cooking station KS ₁ as well as the cooking station KS ₂ via a light guide L _S1 and L _S1 'connected to a light transmitter S ₁ or associated with this. Accordingly, the hob KS ₃ with a light guide L _S2 and the hob KS ₄ with a light guide L _{S2 associated with} the light transmitter S ₂ . Here are still the connectors V ₁ and V ₃ and the end pieces E _S1 , E _S1 . and E _S2 , E _S2 provided.

The hob KS ₁ is assigned via a light guide L _R1 and a connector V _{2 to} the light receiver R ₁ , as well as the hob KS ₃ via a light guide L _{R1 '.} The cooking station KS ₂ is assigned via a light guide L _R2 and a connector V ₄ a light receiver R ₂ , as well as the hob KS ₄ via a light guide L _{R2 '} . For four cooking areas KS, four light-guiding means or eight light guides and four electrical components, namely two light transmitters S and two light receivers R, are required.

In the Fig. 1 is shown as a schematically illustrated heater H _4, an induction heater, but in principle could also be a radiant heater. Since the end pieces E _{S2 '} and E _R2' advantageously pass through the region of the induction heating device, this can be done either through a central region, in which usually also no turns are present in an induction heating device. Alternatively, the end pieces E _{S2 '} and E _{R2' are} relatively thin or narrow and can also run in the middle through a winding field of a conductor of the induction heater. At the hob KS ₃ , a gas burner with a pot carrier 15 and a pot T ₃ is shown on it. It can also be seen here how a distance exists between the end pieces E _S2 and E _R1 and the underside of the pot T ₃ .

In Fig. 2 an example is shown in which four frequencies are used and a pot is only recognized as being set up if at least two frequencies have a light receiver R receives a corresponding matching light signal of the light transmitter S. Where "X" corresponds to a disturber, "_" corresponds to a signal that no pot is set, and "U" corresponds to a signal that a pot is set up. In the upper two lines, only one of the frequencies f1 to f4 has an interferer, namely both times at the first frequency f1 for the sake of simplicity. Since a disturber can generate or cause both signals, so that both a pot is set up and that a pot is not set up, the probability for one of the two states is random. In the example of the first line, no pot is placed, and since only one frequency has an interferer "X", and the other three frequencies f2 to f4 have the same and consistent results, namely that no pot is set up corresponding to "_" the result that no pot is set up. The reverse case, namely that a pot is placed, is shown in the line below, and then just leads to the correct result that a pot is set up. The interferers are always in the examples at one or two of the signal frequency (s).

In the two lower double lines of Fig. 2 There are two interferers or interferers at two frequencies, here for example the frequencies f1 and f2. If no pot is set up here, the correct recognition of this condition at the frequencies f3 and f4 still can not give an exact result and the result is therefore "X", ie an interference signal or an error function of pot detection.

In the Fig. 3 is shown as at four different frequencies f1 to f4 and the requirement that at least three frequencies a match between emitted light signal and reflected light signal must be present. The upper lines show similar to the two upper lines of the Fig. 2 indicates that in the case of a fault "X", only at a frequency or, for example, the frequency f1 and otherwise consistent detection, a correct result is also obtained. In the two lines below it is shown, similar to the previous one in Fig. 2 in that two interferers "X" at two frequencies, here by way of example f1 and f2, in the condition that a pot is actually set up, provide an interference signal. This can be, for example, because both interfering signals have caused the answer "pot not set up".

If only one interferer needs to be eliminated, then it is not really necessary to run the effort to test at four frequencies; one test at three frequencies is sufficient if, for example, the gaps of the frequency f4 are omitted. This is in fact simpler, and two simultaneously occurring disturbances can not be recognized practically even with the evaluation of four frequencies actually practicable.

Therefore, a detection with five frequencies can be made, as in Fig. 4 is shown. At the top two lines, three frequencies must give a correct answer, which works in the case of the two upper frequencies. Given that four out of five frequencies must be correct, the occurrence of two interferers can not be reliably detected or eliminated, as shown in the lower double line. Therefore, the additional effort of five frequencies compared to three frequencies is only worthwhile if two interference frequencies can be eliminated instead of one interference frequency, which ensures the evaluation of only three out of five and not four out of five.

Claims (14)

Method for pot detection of a pot set up on a cooking surface with a reflex photoelectric sensor, wherein the reflex photoelectric sensor has a light transmitter and a light receiver, with the steps: a light transmitter emits light to the pot or to the cooking point and to the pot set up on the cooking surface, wherein the emitted light is modulated with at least three frequencies, - the pot reflects the light and it is received by the light receiver, in a pan detection control it is checked at how many frequencies of the light emitter the light receiver receives reflected light signals of the light emitter, - A pot is detected as set up only if at least two frequencies and / or at least half of the number of emitted frequencies of the light receiver detects light signals of the light transmitter. A method according to claim 1, characterized in that the emitted light is modulated with four or five frequencies, wherein preferably a pot is only recognized as being set up when at least three frequencies of the light receiver detects light signals of the light transmitter. A method according to claim 1, characterized in that the emitted light is modulated with more than five frequencies, wherein preferably a pot is only detected as established if at more than half of the frequencies of the light receiver detects light signals of the light transmitter. Method according to one of the preceding claims, characterized in that in the evaluation of the light receiver, a digital filter with the principle of a lock-in amplifier is used for a very edge-band bandpass filter. A method according to claim 4, characterized in that system-dependent signal level of the lock-in filter decrease with increasing frequency of the light signals, and in particular n individual limits are used in generating n frequencies of the light signals. Method according to one of the preceding claims, characterized in that the light transmitter at least partially transmits light in the IR frequency range. A method according to claim 6, characterized in that the light emitter sends light exclusively in the IR frequency range. Method according to one of the preceding claims, characterized in that a modulation of the light signals emitted by the light signals is rectangular or sinusoidal. Method according to one of the preceding claims, characterized in that the light transmitter is switched on and off by means of an electrical switch, in particular a MOSFET transistor. Method according to one of the preceding claims, characterized in that the light receiver evaluates the frequency, phase position and amplitude of the light signals received by it and compares them with those of the light signals emitted by the light transmitter. Method according to one of the preceding claims, characterized in that the reference signal which is multiplied by the receiver signal in a lock-in filter is due to simplified signal processing in the pC rectangular and identical in shape to the modulated light signal instead of sinusoidal. Method according to one of the preceding claims, characterized in that the frequencies of the light emitted by the light emitter light have no common integer divider. Method according to one of the preceding claims, characterized in that all frequencies used are not an integer multiple of one of the frequencies. Device for pan detection of a set up on a cooking pot with a reflex light barrier, characterized in that the device comprises a light transmitter, a light receiver and a controller for controlling the light emitter and for evaluating the light receiver, wherein the controller is adapted to the method to carry out any of the preceding claims.

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