DE102017117133A1 - Method for wireless signal transmission, use of a method for wireless signal transmission and cooking appliance - Google Patents

Abstract

A method for wireless signal transmission in a cooking appliance during its operation is described, in which a radio channel period (F) is divided into N equal time intervals (ΔT). A first signal is transmitted N times at a first frequency in the radio channel period (F). The received first signals are averaged. Furthermore, the use of a method for wireless signal transmission for temperature measurement and a cooking appliance are described.

Description

The invention relates to a method for wireless signal transmission in a cooking appliance during its operation, the use of a method for wireless signal transmission for temperature measurement and a cooking appliance.

Cooking appliances are known from the prior art, which are used in professional or commercial kitchens. These cooking appliances can include a so-called core temperature sensor as a cooking accessory with which the core temperature of a food can be measured. The temperature measurement can be wireless, so that the temperature detected by the core temperature sensor is transmitted wirelessly by means of a signal to an evaluation that evaluates the corresponding temperature.

It is known that a so-called SAW sensor structure can be used for such core temperature sensors, where SAW stands for "Surface Acoustic Wave". Accordingly, the signal transmission takes place by means of a high-frequency signal (RF signal), which is transmitted via a high-frequency transmission path between a transmitting unit and a receiving or evaluation unit. The method used in the SAW technology is known from the prior art, as among others from the DE 10 2010 033 632 A1 evident. The method makes it possible to obtain from a complex amplitude response per frequency point in the frequency domain by means of inverse Fourier transformation response signals from SAW components such as the SAW sensor structure in the time domain and thus to determine correlatable temperature information. The SAW sensor structure is, for example, at least one completely passive sensor which can be read out without contact. For this purpose, an interrogation signal is generated by the transmitting unit (similar to the radar technique) and sent to the sensor, and the sensor reflects a response signal that can be received and evaluated by the receiving unit. The SAW sensor is a sensor chip that works with surface acoustic waves (SAW = Surface Acoustic Wave). Among other things, the surface wave has a temperature-dependent phase velocity, so that the temperature can be concluded on the basis of the transit time of the surface wave, preferably to a reflector structure and back. Thus, from the response signal returned by the SAW chip, one can infer the temperature to which the SAW chip in the core temperature probe is exposed. It is known to use so-called delay line SAW sensors or resonance SAW sensors for temperature measurement.

It is furthermore known that the high-frequency transmission path provided for signal transmission is disturbed, for example, by a fan wheel rotating during operation of the cooking appliance, which is assigned to the cooking chamber, since the rotating fan wheel acts like a high-frequency mode mixer for the high-frequency signal to be transmitted acts.

In order to minimize or eliminate the disturbance of the fan, it is known from the prior art that the temperature determination by means of the SAW technology via a so-called trigger signal. For example, in each case a temperature measurement is carried out during a period of the fan wheel, ie a complete rotation of the fan wheel, wherein several measurements are made at different frequencies per period of the fan wheel in a sequential manner. For temperature determination, several acquired spectra are then averaged for initialization, so that subsequently changes in the spectrum are used for the evaluation of the temperature.

However, it has proved to be disadvantageous that the susceptibility of the temperature measurement due to the fan continues to be relatively high, and also the temperature measurement requires a long period of time, especially their initialization time at the beginning, since a temperature measurement with a certain frequency only in a period of the fan can be done. Furthermore, a trigger signal must be provided, which causes additional costs.

The object of the invention is to provide a less interference-sensitive, inexpensive and faster method for wireless signal transmission, a use of such a method for temperature measurement and a cooking appliance, with which this is possible.

The object is achieved according to the invention by a method for wireless signal transmission in a cooking appliance during its operation, in which a radio channel period is divided into N equal time intervals, wherein a first signal having a first frequency in the radio channel period is transmitted N times, and wherein the received first signals are averaged.

wobei F die Funkkanalperiode, T die Periode der Lüfterraddrehung und S die Symmetrie des Lüfterrads sind. Insofern umfasst eine Funkkanalperiode einen Winkelbereich von $\propto =\frac{360°}{s}.$

Da die ersten Signale mit der ersten Frequenz über die Funkkanalperiode gleichmäßig verteilt übertragen werden, wird der störende Einfluss der Funkkanalmodulation für die Temperaturauswertung so stark unterdrückt, dass es nicht mehr notwendig ist, ein Triggersignal zu verwenden, wodurch das Verfahren zur Signalübertragung entsprechend vereinfacht und die Implementierung günstiger ist.The invention is based on using the symmetrical design of the fan wheel used in a cooking appliance, since this example includes six equally trained and symmetrically distributed fan blades. In this respect, the fan wheel has a six-fold symmetry, whereby the period of a fan wheel (360 °) can be divided into six equal radio channel periods (60 °). Furthermore, the method uses that by the Fan-induced disturbance is a periodic function. In the case of periodicity, however, the radio channel period is used instead of the period of the fan wheel, which means that correspondingly more signals can be transmitted in one period. The measuring rate is correspondingly higher. A radio channel period is therefore dependent on the symmetry of the fan and the period of the fan. This can be expressed as follows: $F=\frac{T}{S\text{'}}$

in which F the radio channel period, T the period of the fan wheel rotation and S the symmetry of the fan are. In this respect, a radio channel period comprises an angular range of $\alpha =\frac{360°}{s},$

Since the first signals at the first frequency are transmitted evenly distributed over the radio channel period, the disturbing influence of the radio channel modulation for the temperature evaluation is suppressed so much that it is no longer necessary to use a trigger signal, whereby the method of signal transmission is simplified accordingly and the Implementation is cheaper.

Furthermore, the subdivision of the radio channel period into N has equal time intervals in each of which the first signal is transmitted at the first frequency and then averaged, with the result that the averaging number is also N. The higher the averaging number, the better the disturbances can be averaged, but with increasing averaging the measurement duration increases.

By the corresponding method of the fan position-dependent averaging of the received signals, undesired high-frequency disturbances induced by the fan wheel are very effectively eliminated, so that the accuracy of the temperature measurement is improved. At the same time, the signal-to-noise ratio (SNR) of the transmitted signals is improved so that correspondingly more robust temperature measurements are possible.

In other words, the radio channels used in the signal transmission are periodically varied by the rotation of the fan. The period of this modulation, which corresponds to the "radio channel period", results from the period of the fan wheel revolution divided by the symmetry of the fan wheel. The phase within this radio channel modulation is called the radio channel phase.

If the amplitude measurements for a temperature measurement in each case at the same radio channel phases in successive Funkanalperioden would be recorded, then there would be only one amplitude measurement with a certain frequency in a radio channel period, which would require a corresponding number of amplitude measurements for a temperature measurement. This, however, delays the process. Since the disturbance caused by the fan is a periodic function, the radio channel period can be subdivided into N equal time intervals in which a signal for amplitude measurement is transmitted, so that a plurality of signals with a certain frequency can be used for amplitude measurement in one radio channel period the entire measuring process accelerates accordingly.

One aspect provides that the first signals are transmitted at intervals of one time interval in each case. For example, a radio channel period is divided into three equal time intervals (N = 3), wherein the distance between the first signals is exactly the same, so that there are equidistant measuring points, which are separated from one another by the interval of the time interval. The averaging of the received first signals, which correspond to the equidistant measuring points in the radio channel period, gives a far better result than an averaging of randomly distributed measured values.

Another aspect provides that in a time interval several signals with different frequencies are transmitted in a time interval. Thus, the time interval between two signals of the same frequency (for example, two first signals of the first frequency) can be filled by further intervening signals having different frequencies. In this way, signal groups each having a different frequency result, in which the measurement is performed N times during a radio channel period, ie in the correspondingly formed time interval. Each signal group is transmitted exactly once in a time interval. For example, in a time interval five different signals with five different frequencies are transmitted, whereby a frequency band can be transmitted quickly, which includes several frequencies, such as the ISM band from 2.4 GHz to 2.4835 GHz.

In particular, signals are transmitted at the same frequency in each case at a distance from a time interval. This means that all signals which have the same frequency are transmitted in each case equidistant from one another, ie at a distance of exactly one time interval. This ensures that the signals with different frequencies are transmitted periodically, in particular periodically with respect to the radio channel period. This ensures that the corresponding measurement results can be well averaged to obtain a robust result.

According to one embodiment, the signals are transmitted at different frequencies over several radio channel periods. As already explained, In a radio channel period, in each case one signal group with signals of different frequencies is transmitted N times, wherein in the next radio channel period, a next signal group with signals, again of different frequencies, follows, which are also transmitted N times. As a result, signals having a plurality of different frequencies are transmitted during complete rotation of the fan wheel (period), so that a frequency range for signal transmission can be transmitted faster, for example, a corresponding ISM band.

According to a further aspect, the signals with different frequencies cover an intended frequency range with a predefined resolution, in particular a frequency range from 2.4 GHz to 2.4835 GHz. The frequency range from 2.4 GHz to 2.4835 GHz corresponds to a predefined ISM band type B in which, for example, 800 different frequencies can be used for signal transmission, so that a resolution of about 0.1 MHz is given.

Furthermore, the invention relates to a use of a method for wireless signal transmission of the aforementioned type for temperature measurement. In this respect, the method for wireless signal transmission is used to transmit temperature information from a temperature sensor, for example a core temperature sensor, to a corresponding evaluation unit. The signal to be transmitted is less disturbed, since this is transmitted as a function of the radio channel period, ie the period of the fan and the symmetry of the fan. Due to this, the signal transmission over a corresponding frequency range is also faster than a signal transmission in which only one signal is transmitted during a period of the fan wheel.

Furthermore, the invention relates to a cooking appliance, with a transmitting unit, a receiving unit, a cooking chamber and the cooking chamber associated fan wheel, which is constructed rotationally symmetric, so that the fan during a period of the fan includes several radio channel periods, wherein between the transmitting unit and the receiving unit a wireless Transmission line is formed, and wherein the transmitting unit is adapted to transmit a first signal having a first frequency N times during a radio channel period. In this respect, it is possible that a plurality of signals are transmitted during a radio channel period, whereby in particular the number of transmitted signals during a period of Lüfterraddrehung can be increased.

In addition, the cooking device is designed to transmit during a radio channel period, further signals with different frequencies, which are each transmitted with a defined, temporally constant offset to each other. This makes it possible with the cooking device to perform the wireless signal transmission quickly and easily, at the same time the susceptibility of the signal transmission is reduced.

One aspect provides that a wireless core temperature sensor is provided, which is provided in the wireless transmission path between the transmitting unit and an evaluation unit designed as a receiving unit. The evaluation unit can be, for example, an evaluation unit in the higher-level control of the cooking appliance, so that the information or signals transmitted by the core temperature sensor are evaluated accordingly by the cooking appliance. The transmitting unit can also be part of the higher-level control of the cooking appliance.

In particular, the transmitting and receiving unit are provided in a common assembly.

As already explained at the outset, the core temperature sensor with SAW sensor structure is a passive component which is activated via an interrogation signal in order to emit a corresponding response signal, via which the temperature can be determined. The corresponding interrogation signal originates from the transmitting unit. The interrogation signal accordingly corresponds inter alia to the first signal having the first frequency and the further signals having the different frequencies in order to contain a corresponding response signal with temperature information. The core temperature sensor receives the first signal at the first frequency and the other signals at the other (different) frequencies and sends out a corresponding response signal. The resulting time delay through the transmission path between the antenna of a readout unit and the antenna of the core temperature sensor is the one hand for all signals the same and negligible on the other hand. In this respect, the (response) signals emitted by the core temperature sensor are constantly offset in time with each other in the same way as the signals emitted by the transmitting unit, in particular the signals with the same frequency around the time interval.

In particular, the cooking appliance is designed to carry out a method of the aforementioned type.

In general, the method is also applicable to cooking appliances that include a plurality of fan wheels that rotate, for example, with a similar frequency.

• - 1 eine schematische Ansicht eines erfindungsgemäßen Gargeräts,
• - 2 eine schematische Darstellung eines Lüfterrads, das bei einem erfindungsgemäßen Gargerät verwendet wird, und
• - 3 eine schematische Darstellung der übertragenen Signale, anhand derer das erfindungsgemäße Verfahren verdeutlicht wird.

Further advantages and features of the invention will become apparent from the following description and the drawings, to which reference is made. In the drawings show:

• - 1 a schematic view of a cooking appliance according to the invention,
• - 2 a schematic representation of a fan wheel, which is used in a cooking appliance according to the invention, and
• - 3 a schematic representation of the transmitted signals, based on which the inventive method is illustrated.

In 1 is a cooking appliance 10 shown that a housing 12 which has a technical room 14 as well as a cooking space 16 encloses.

The cooking space 16 is opposite the engineering room 14 through an insulation wall 18 thermally insulated, being in the oven 16 a cooking product shown here 20 can be cooked.

The cooking appliance 10 includes a heating source 22 , For example, a hot air source, on the including a cooking chamber atmosphere in the oven 16 is generated, which via a fan 24 with a fan 26 is circulated. In addition, the warm air can be distributed accordingly homogeneous, if desired, so that forms a substantially uniform cooking chamber atmosphere.

In addition, the cooking appliance includes 10 a transmitting unit 30 and a receiving unit 32 which are formed separately from each other as in the embodiment shown. Alternatively, the two units may be formed in a common assembly, such as a control and evaluation.

The transmitting unit 30 communicates via a wireless transmission link 34 with the receiving unit 32 , where a wireless core temperature probe 36 in the transmission line 34 is provided, which in the food 20 is plugged in. The core temperature probe 36 includes, for example, a SAW sensor structure, so the core temperature probe 36 is designed as a passive sensor.

In this respect, the transmitting unit sends 30 Signals off, the core temperature probe 36 stimulate, a response signal over the wireless transmission link 34 to the receiving unit 32 to transmit, with that of the core temperature probe 34 transmitted signal depends on the temperature and thus includes corresponding temperature information received from the receiving unit 32 can be evaluated in a known manner. For example, the temperature information is contained in the frequency of the response signal of a resonator SAW sensor structure, which can be evaluated accordingly, in particular the frequency difference from the frequency of the transmitter unit 30 emitted excitation signal. Alternatively, the temperature-dependent phase velocity can be adjusted so that the temperature results from the transit time of the surface wave, preferably to a reflector structure and back.

The wireless signal transmission takes place in dependence on a so-called radio channel period F , based on the 2 is explained in which the fan 26 is shown schematically in a front view.

The fan wheel 26 has a symmetry S in the embodiment shown by six equally formed fan blades 38 is defined, which is also symmetrical over the entire fan 26 are distributed.

The fan wheel 26 can rotate about its own axis A by 360 °, this being a period T of the fan wheel 26 corresponds, ie a complete rotation of the fan 26 , Furthermore, the fan wheel 26 because of its symmetry S and the corresponding six equally trained blades 38 a radio channel period F on, one-sixth of the period T of the fan wheel 26 equivalent. The radio channel period F thus covers an angular range of 60 °, as clearly from the 2 evident.

Generally, the radio channel period depends F thus from the period T of the fan wheel 26 and the symmetry S of the fan wheel 26 from.

Because the fan 26 is symmetrical, results from the symmetrically arranged and identically shaped blades 38 that is one from the fan 26 on the wireless transmission link 34 trained disturbance periodically with the radio channel period F repeated.

This knowledge is used to optimize the wireless signal transmission in terms of susceptibility and duration, since the radio channel period F in N equal time intervals .DELTA.T is divided, wherein a first signal having a first frequency in each time interval .DELTA.T is transmitted, that is N times. The first signal with the first frequency is therefore transmitted N times with a fixed time interval to each other, the time interval .DELTA.T equivalent. In this respect, the first signal is transmitted periodically, the detected first signals being averaged to eliminate corresponding errors or disturbances. This succeeds particularly well since the first signals are transmitted with the periodicity of the disturbance.

In 3 the corresponding method is shown schematically in which within a radio channel period F three equal time intervals .DELTA.T are provided (N = 3), in each of which five different signals are transmitted at different frequencies, these five signals a first signal group 40 form.

Each of the five different signals are characterized by their frequency indices 1 5 and in the embodiment shown each have the same time offset from one another in the time interval .DELTA.T on, who with .delta.t can be designated.

Alternatively it can be provided that the five different signals of the signal group 40 have different time offenses to each other.

Especially with the last signal within the time interval .DELTA.T , ie the signal with the frequency index 5 , it can be provided that the time offset to the next signal is greater .delta.t is, because then the first signal with the first frequency or the frequency index 1 is transmitted repeatedly (second or third) times.

The time offset is optimal .delta.t however, equal and as small as possible to encompass as many different frequencies as possible with a signal group.

It is important that the signals have the same frequency, ie the same frequency index 1 - 5 which is in a radio channel period F N times are transmitted, each by the distance of a time interval .DELTA.T be transferred from each other, so that there are equidistant transmission points, which can be averaged for each frequency accordingly. Since the radio channel period F present in three equal time intervals .DELTA.T is divided, results in an averaging number of 3, since each signal with associated frequency index is transmitted three times.

Each signal of the first signal group 40 that from the sending unit 30 is sent, stimulates the core temperature probe 36 , in particular its SAW sensor structure, accordingly, so that the core temperature sensor 36 sends back a response signal coming from the receiving unit 32 received and evaluated. Depending on the above the core temperature probe 36 detected temperature results in a correspondingly differently designed response signal, so that the receiving unit 32 from this the core temperature of the food 20 can determine.

Furthermore, goes from the 3 show that in a second radio channel period F to the first radio channel period F connects, a second signal group 42 which, in the embodiment shown, the frequency indices 6 - 10 whose different signals in turn each at a distance of exactly one time interval .DELTA.T be transmitted. The signal transmission of the second signal group 42 corresponds in an analogous manner to the signal transfer of the signals of the first signal group 40 apart from the different frequencies of the signals of the second signal group 42 , In this respect, several different frequencies in the successive radio channel periods F be transferred, resulting in a correspondingly high measuring rate.

This is repeated until all intended frequencies have been transmitted. In the exemplary embodiment shown, there are 800 different frequency indices, ie 800 frequencies with which, for example, the ISM band can be transmitted in the frequency range from 2.4 GHz to 2.4835 GHz.

Because instead of the period T of the fan wheel 26 the radio channel period F is used as a periodic reference, the wireless signal transmission method is correspondingly faster. Because within a radio channel period F In addition, several signals with different frequencies several times in corresponding time intervals .DELTA.T be transmitted, the method for wireless signal transmission is again correspondingly faster. In addition, the method is improved over the known from the prior art method in that the occurring disturbances can be better eliminated. The improvement therefore relates to the robustness of the signal transmission, since the same frequencies are transmitted several times at a periodic interval, and the speed of the signal transmission in a certain frequency range.

With the method according to the invention, the use of the method for wireless signal transmission for temperature measurement and a correspondingly designed cooking appliance 10 It is therefore possible to obtain a susceptible and fast signal transmission. For example, the method is 5-10 times faster than conventional methods known in the art, although the measurements are more robust at the same time.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102010033632 A1 [0003]

Claims (10)

A method for wireless signal transmission in a cooking appliance (10) during its operation, in which a radio channel period (F) is divided into N equal time intervals (ΔT), wherein a first signal having a first frequency in the radio channel period (F) N times transmitted and wherein the received first signals are averaged. Method according to Claim 1 , characterized in that the first signals in each case at a distance of a time interval (.DELTA.T) are transmitted. Method according to Claim 1 or 2 , characterized in that in a time interval (.DELTA.T) a plurality of signals having different frequencies in a time interval (.DELTA.T) are transmitted. Method according to Claim 3 , characterized in that signals at the same frequency in each case at a distance of a time interval (.DELTA.T) are transmitted. Method according to Claim 3 or 4 , characterized in that signals of different frequency in the different time intervals (.DELTA.T) are each transmitted with a defined, temporally constant offset to each other. Method according to one of the preceding claims, characterized in that the signals are transmitted at different frequencies over a plurality of radio channel periods (F). Method according to one of the preceding claims, characterized in that the signals with different frequency cover a designated frequency range with a predefined resolution. Use of a method for wireless signal transmission according to one of the preceding claims for temperature measurement. Cooking appliance (10), with a transmitting unit (30), a receiving unit (32), a cooking chamber (16) and a cooking chamber (16) associated fan wheel (26) which is rotationally symmetrical, so that the fan (26) during a period (T) of the fan wheel a plurality of radio channel periods (F), wherein between the transmitting unit (30) and the receiving unit (32) a wireless transmission path (34) is formed, and wherein the transmitting unit (30) is formed, a first signal having a first Frequency during a radio channel period (F) to transmit N times. Cooking appliance (10) after Claim 9 , characterized in that a wireless core temperature sensor (36) is provided, which is provided in the wireless transmission path (34) between the transmitting unit (30) and an evaluation unit designed as a receiving unit (32).

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