EP1897414A1

EP1897414A1 - Device for heating up a heating element

Info

Publication number: EP1897414A1
Application number: EP06754805A
Authority: EP
Inventors: Dirk Hoffmann; Jochen Bühner; José Miguel Burdio Pinilla; Jose Ramon Garcia Jim Nez; Pablo Jesus Hernandez Blasco; Sergio Llorente Gil; Alfonso Lorente Perez; Fernando Monterde Aznar
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2005-06-08
Filing date: 2006-04-24
Publication date: 2008-03-12
Anticipated expiration: 2026-04-24
Also published as: ES2289872B1; US20090294437A1; WO2006131419A1; ES2393201T3; EP1897414B1; ES2289872A1

Abstract

The invention relates to a device (2), in particular, for inductively heating up a heating element (4) by means of an inductor (10) and an element (14)for recording a reference quantity (F) which is dependent on the temperature (TH) of the heating element (4) and derived from the electric quantity of the inductor (10) in such a way that it makes it possible to form the reference value (F1, F2, F3) from the reference quantity (F) and to adjust the temperature (TH) according to the reference quantity (F) adjustment by means of the reference value (F1, F2, F3). The aim of said invention is to carry out a reliable adjustment of a water temperature (TW ) or of a cooked product even at extreme conditions or when the reference value (F1, F2) is incorrect. For this purpose, the device (2) comprises a correction means (16)for correcting the reference value (F1, F2).

Description

Device for heating a heating element

The invention relates to a device for in particular inductive heating of a heating element according to the preamble of claim 1.

From WO 2004/103028 A1, a temperature control for an induction cooker is known, in which an operator can start the control at a desired time by entering a corresponding command. A control unit registers a value of a controlled variable associated with the temperature of a cooking vessel at this starting time and regulates the power of the inductor so that the controlled variable remains as close as possible to this guide value. The controlled variable of the temperature control is derived from an electrical variable of the inductor of the induction cooker. If, for example, water in the cooking container begins to boil easily after the cooking container has been heated up, the operator can continue to simmer the water as desired by starting the regulation process.

It is the object of the present invention to provide a generic device with which the temperature of a heating element or the temperature of a food can be controlled reliably on the heating element. This object is achieved by the features of claim 1. Advantageous embodiments and further developments of the invention can be taken from the subclaims.

The invention relates to a device for heating a heating element, in particular with an inductor, a radiant heater or a gas burner, and a means for detecting a dependent of a temperature of the heating element and derived from an electrical variable of the inductor reference variable to form a guide value from the reference variable and for regulating the temperature by means of the regulation of the reference variable with the aid of the reference value.

It is proposed that the device comprises a correction means for correcting the reference value. The leader value can be manually set by an operator or automa- be corrected or adapted to new needs, so that in a simple manner, a uniform maintenance of a desired temperature can be achieved. A dependent on the temperature of the heating element reference variable, which is derived from an e- lektrischen size of the inductor, usually correlates with the temperature of only a very thin layer of the heating element, for example, a pot bottom, which faces the inductor. The temperature of this thin layer does not necessarily match the temperature of, for example, food or water in the pot. In a rapid heating of the pot by a large supplied heating power, for example, the bottom of the pot, especially the bottom layer of the pot bottom, already much hotter than the boiling point of the water when the water begins to boil. If the automatic temperature control is started by an operator at this time, the guide value is formed from the reference variable and the reference variable is kept as close as possible to the guide value, it may be that the pot bottom is kept at a very hot temperature to strongly bubble the initially simmering water begins and an operator wants to reduce the supplied heating power. The correction means can be used to correct the management value and to regulate the reference variable with the aid of the new management value, in particular to the new management value. This applies correspondingly to devices in which the temperature of a wall of the heating element is cooled in a known manner with an infrared sensor, or in which a temperature sensor is arranged below a storage plate for the heating element. In this case, the device z. As a radiant heater or a gas burner.

Depending on the choice of electrical size or the electrical sizes of the inductor, from which or from which the reference variable is derived, the reference variable may also depend on the performance of the inductor. In the event of a sudden change in power, for example, by an operator starting temperature control, the command variable may vary widely and the temperature control may be unreliable and undesirable. Again, by a correction of the guide value, for example, after a settling of the heating system, in a simple manner, a reliable temperature control can be achieved. The same applies to devices with radiant heaters or gas burners.

The acquisition of the reference variable can be done by measuring and / or calculating. As a guide value, the value of the reference variable at a fixed point in time, for example, the start time. The means for detecting the reference variable may include the correction means. It is also possible that a control unit, for example a microcontroller, contains both the means for detecting the reference variable and the correction means. The correction means may be an adjusting means for adjusting the guidance value to a new condition or a new condition. The reference variable can be used as a controlled variable. It is expediently regulated to the management value. The leader value may be constant over time or a function of time.

In an advantageous embodiment of the invention, the correction means comprises an input means for inputting a correction command by an operator to correct the command value. The guide value and thus the temperature control can be easily adapted manually and reliably to the needs of the operator.

Conveniently, the correction means is prepared to change the guide value to a correction command by a correction value. The guide value is thereby corrected in discrete steps, whereby the correction per se, the correction of the correction and the handling by an operator are kept simple.

In a further embodiment of the invention, the correction means is prepared to automatically correct the guide value at the beginning of the temperature control, in particular in order to change a correction value. This correction is particularly useful for systematic errors, which are caused for example by a dependence of the reference variable of the power of the inductor. The guide value can be calculated at the beginning of the temperature control and then corrected. It is also possible for the guide value to be determined at the beginning of the temperature control on the basis of an already corrected calculation or from the corrected reference variable, without it having previously been determined uncorrected. The start of the temperature control can be automatic or based on an operator command.

A particularly simple correction is made when the correction value is a preset value. The correction value may be an absolute value or a relative value, which depends, for example, on the size of the reference variable. If the correction value depends on the reference variable - as a preset or non-defaulted one - A -

Value - a particularly user-friendly correction can be achieved, since multiple corrections can be avoided. For example, at a high temperature of the heating element, the correction value may be greater than at a low temperature. Even with a high power of the inductor to start the temperature control, a higher correction value can be selected than at a lower power.

Advantageously, the correction value is dependent on a heating parameter determined before the control, for example the heating power, the temperature of the heating element or, for example, a temperature gradient of the heating element. This can be corrected very quickly and a multiple correction can be avoided. A rapid and effective correction can also be achieved by the fact that the correction value is dependent on a determined property of a food to be heated. If, for example, a lot of water - also referred to below as food to be cooked - in the pot to be heated, the correction value can be made large, and with little water, this can be chosen small.

It is also proposed that the correction means is prepared to correct the command value after a signal start to start the temperature control and to form the command value from the corrected command value. As a result, the device can be brought out of an extreme situation, for example the application of a maximum power, and brought to the state which it has during the temperature control before a determination of the guide value. The command value may be formed of a command value determined at a state at least similar to the state during the temperature control, and a systematic error in the determination of the command value may be corrected and a reliable temperature control may be achieved.

Particularly easy, the state of the device can be led out of an extreme state when the correction z. B. comprises a reduction of the power of the inductor to an intermediate value. An intermediate value is to be understood as a power value that lies behind the start signal and before the control phase in terms of time.

The intermediate value is advantageously a value already set before the start signal, whereby a very simple correction is achieved. A particularly effective correction can be achieved if the intermediate value substantially corresponds to the power required to maintain a desired temperature of the heating element, in particular the temperature which the heating element has at the start signal. As a result, the state of the device in the determination of the guide value is similar to the state that it assumes during the control, so that a dependence of the reference variable of, for example, the performance of the inductor as a trigger for a systematic error can be largely overcome.

Further advantages emerge from the following description of the drawing. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Show it:

1 shows a device for inductive heating of a heating element in a schematic representation,

2 shows a diagram in which a reference variable for a temperature control, the power of the inductor and the water and pot temperature are plotted against time,

3 is the diagram as shown in Figure 2 with a larger amount of water in the pot,

Fig. 4 shows the diagram of Figure 2 with a systematic error in the reference variable and

Fig. 5 is the diagram of Figure 4, in which the systematic error is eliminated.

1 shows a device 2 for inductive heating of a heating element 4 in the form of a pot bottom of a pot 6. To heat the pot 6 is on a support plate 8, under which an inductor 10 is arranged. Connected to the inductor 10 is a control unit 12, which comprises a means 14 for detecting a dependent of a temperature of the heating element 4 and derived from an electrical variable of the inductor 10 reference variable. The device 2 also has a correction means 16 comprising parts of the control unit 12 and an input means 18 for inputting a correction command by an operator. The input means 18 has two keys 20 with which one of The control unit 12 formed guide value - and thus a target temperature of the heating element 4 - can be corrected up or down. Alternatively, a radiant heater or a gas burner can be assigned as a heat source. The means 14 may be formed on a above or below the support plate 8 second-order temperature sensor. The measured temperature forms the reference variable F; it may deviate more or less from the actual temperature T of the pot 6.

FIG. 2 shows a diagram in which the temperature T _{H of} the heating element 4 is plotted over inductive heating over time t. Also, the temperature T _w of water over the time t is applied, which is heated in the pot 6 by the heating of the heating element 4 with. The temperature T _w here indicates the temperature T _{w of} the lowermost water layer in the pot 6, which is adjacent to the heating element 4. Overlying layers of water are slightly colder when the water is heated. With a thick solid line, the heating power P of the inductor 10 is plotted against time t in FIG. In addition, a reference variable F is plotted against the time t, which is detected from the inductance of the system with the inductor 10 and the heating element 4 and in particular from the current flow through the inductor 10 from the means 14.

At the beginning of a heating process at time t ₀ , both the heating element 4 and the water above it, for example, room temperature. For heating the heating element 4 and the water, the heating power P is switched to a relatively high level, the heating element 4 is heated and with him - delayed in time - the water located above the heating element 4. As the temperature T _H increases, the inductance of the system comprising the heating element 4 and thus also the reference variable F decrease.

At time ti, the water has reached the temperature T ₁ that an operator wishes to hold. For example, the water has started to boil easily. By simultaneously pressing the two buttons 20, the operator generates a start signal for starting a temperature control. In this temperature control, the reference variable F, and with it the temperature T _{H of} the heating element 4, is maintained at a constant level in order to keep the water above it at a constant temperature level. At the time ti has the heating element 4 in its lowest and most relevant for the detection of the reference variable layer temperature T ₂ , which is for example at 115 ° C and thus not insignificant above the temperature T ₁ of 100 ⁰ C of the water. Would that be Heating element 4 now remain kept constant at the temperature T ₂ of 115 ° C, the heating element 4 would continue to give off heat as in the heating process to the water, and the water would be heated more and finally bubble strong.

In order to prevent this, the control method is started as follows: The reference variable F has fallen very far at time ti and has reached a reference value F ₁ which can be detected by the means 14 or derived from the reference variable F. In response to the start signal, the reference value F _{1 is raised} by the correction means 16 by a preset correction value F _K1 to a new reference value F ₂ . The reference variable F is now controlled to the new reference value F ₂ by the heating power P of the inductor 10 is greatly reduced. As a result, the heating element 4 cools from the temperature T ₂ of 115 ° C to the temperature T ₃ , for example 107 ⁰ C, down. The water temperature T _w still oscillates slightly above the temperature T ₁ , since a certain amount of heat of high temperature T _{H is still} stored in the heating element 4 and is released to the water. By mixing the layers of water in the pot 6, however, the lower layer of water now cools slowly and, for example, drops below the temperature T _{1 set} by the operator as the desired temperature, the water stops to boil and is perceived by the operator to be too cold , By actuating the key 20 with the "+", it triggers a correction of the guide value F ₂ by a new, preset correction value F _K2 to a new reference value F _3. As a result, the temperature T _{H of} the heating element 4 is raised to a somewhat higher temperature T. ₄ regulated, whereby the water is slightly heated, reaches the desired temperature T ₁ and, for example, simmer gently again.

Figure 3 shows the control method as shown in Figure 2, wherein the pot 6, however, in contrast to Figure 2 contains a considerably larger amount of water. With the same heating power P of the inductor 10 after a heating start, which is not shown in Figure 3, the temperature T _{H of} the heating element 4 and with it the temperature T _{w of} the water increases much slower than in Figure 2. This lower temperature gradient of the heating element 4th is registered by the control unit 12. When the start signal at the time ti, the guide value F ₁ is corrected by a correction value F _K3 to the new guide value F ₂ , which is greater than the correction value F _K1 of Figure 2, because of the heating power P in conjunction with the low temperature gradient of the heating element. 4 closed to a large amount of water and the correction value F _K3 was set depending on the amount of water. As in FIG. 2, the temperature T _w also decreases in FIG. 3 of the water by the mixing of the water below the desired temperature T ₁ , and the operator corrects the temperature T _H by pressing the button 20 with the "+" at the time t _2. By this correction, the guide value F ₂ by a correction value F _K4 corrected to a new command value F _3, wherein the correction value F _K4, due to the large amount of water is greater than the correction value F _K2 of Figure 2. In another method, the correction values R _K3 and R _K4 are dependent on the reference variable F and, for example, in the selection of a high temperature T ₁ by a large operator and small at a low temperature T ₁ selected.

FIG. 4 shows another method carried out by the device for inductive heating of the heating element 4, which is the same as the method of FIG. 2 up to the time t.sub.i, at which the operator simultaneously presses the two buttons 20 and triggers the starting signal 2, the heating power P of the inductor 10 after the start signal has been greatly reduced in order to end the heating process of the water. Depending on the type of derivation of the reference variable from one or more electrical variables of the inductor 10, the systematic error may occur that the reference variable F depends on the heating power P of the inductor 10. FIG. 4 shows a dependency of the reference variable F on the heating power P at which the reference variable F likewise drops when the heating power P drops. If now the guide value F _{1 determined} immediately after the start signal and before the Ablegingin the heating power P, then the means 14 and the control unit 12 is lowered by the fall of the heating power P from the guide value F ₁ to a value F ₄ command value F on the Guide value F ₁ up, as shown in Figure 4. This is associated with a lowering of the temperature T _{H of} the heating element 4 from the temperature T ₂ to the temperature T ₃ , whereby the water cools strongly and rapidly drops below the desired temperature T ₁ . By a manual correction at time t ₂ , this systematic error can be corrected manually.

FIG. 5 shows a method by which the systematic error shown in FIG. 4 is counteracted. The guide value F ₁ is not formed immediately after the start signal, but the heating power P is first reduced to an intermediate value P _z and held there for a little while until time t ₂ . Due to the systematic error, the reference variable F decreases to the value F ₄ and increases until the time t ₂ - due to a cooling of the heating element 4 from the temperature T ₂ to the temperature T ₃ - easily. During this time, the entire system may Heating state before the time ti settle in a less dynamic state, wherein the guide value F _{3 is formed} only at time t ₂ and the reference variable F is adjusted to this guide value F ₃ . The water, which has become too cool after a brief further heating by residual heat in the heating element 4 and a cooling by mixing in the pot 6, is hereby again guided to the desired temperature T ₁ .

The intermediate value P _z is chosen to be substantially equal to the power required to maintain a desired temperature T ₁ , as shown in FIG. Alternatively, it is possible to set the intermediate value P _z to a value already set before the start signal, whereby the control is particularly simple.

reference numeral

2 device

time

4 heating element

6 pot

8 support plate

10 inductor

12 control unit

14 funds

16 correction means

18 input devices

20 button

F reference variable

Fi guide value

F ₂ leadership value

F ₃ leadership value

F ₄ value

Fκi correction value

Fκ2 correction value

Fκ3 correction value

F _K 4 correction value

P heating power

Pz intermediate value

TH temperature

Tw temperature

Ti temperature

T ₂ temperature

T ₃ temperature

T ₄ temperature to time ti time

Claims

claims

1. Device (2) for heating a heating element (4), in particular with an inductor (10) a radiant heater or a gas burner and a means (14) for detecting a temperature (T _H ) of the heating element (4) dependent reference variable ( F), to form a reference value (F ₁ , F ₂ , F ₃ ) from the reference variable (F) and to regulate the temperature (T _H ) based on the control of the reference variable (F) by means of the reference value (F ₁ , F ₂ , F ₃ ), characterized by a correction means (16) for correcting the guide value (F ₁ , F ₂ ).

2. Device (2) according to claim 1, characterized in that the correction means (16) has an input means (18) for inputting a correction command by an operator to correct the guide value (F ₁ , F ₂ ).

3. Device (2) according to claim 1 or 2, characterized in that the correction means (16) is prepared, the guide value (F ₁ , F ₂ ) to a correction command to a correction value (F _K1 , F _K2 , F _K3 , F _K4 ) to change.

4. Device (2) according to one of the preceding claims, characterized in that the correction means (16) is prepared to automatically correct the guide value (F ₁ ) at the beginning of the temperature control, in particular to change a correction value (F _K1 ).

5. Device (2) according to claim 3 or 4, characterized in that the correction value (F _K i, F _K2 ) is a preset value.

6. Device (2) according to one of claims 3 to 5, characterized in that the correction value (F _K3 , F _K4 ) of the reference variable (F) is dependent.

7. Device (2) according to one of claims 3 to 6, characterized in that the correction value (F _K3 , F _K4 ) is dependent on a determined before the control heating parameters.

8. Device (2) according to one of claims 3 to 7, characterized in that the correction value (F _K3 , F _K4 ) is dependent on a determined property of a food to be heated.

9. Device (2) according to one of the preceding claims, characterized in that the correction means (16) is prepared to correct the reference variable (F) for a start signal for starting the temperature control and the guide value (F ₃ ) from the corrected reference variable (F) to form.

10. Device (2) according to claim 9, characterized in that the correction comprises a reduction of the heating power (P) for the heating element (4) to an intermediate value (Pz).

11. The device according to claim 10, characterized in that the intermediate value (Pz) is already determined before the start signal value.

12. Device (2) according to claim 10 or 11, characterized in that the intermediate value (Pz) substantially corresponds to the power required to maintain a desired temperature (T ₁ ) of the heating element (4).

13. Device according to one of the preceding claims, characterized in that the Führunsgröße (F) of an electrical size of an inductor (10) is derived.