HOB APPARATUS

Abstract

A hob apparatus includes a heating unit, a sensor unit separate from the heating unit and configured to include an electric resonant circuit and to detect a sensor signal, and a control unit configured to control the sensor unit and to analyze the sensor signal. The control unit determines in an operating state a state variable relating to the heating unit based on a phase shift and/or an amplitude ratio between the sensor signal and a further signal.

Claims

1-13. (canceled)

14. A hob apparatus, comprising: a heating unit; a sensor unit separate from the heating unit, said sensor unit configured to include an electric resonant circuit and to detect a sensor signal; and a control unit configured to control the sensor unit and to analyze the sensor signal, said control unit determining in an operating state a state variable relating to the heating unit based on a phase shift and/or an amplitude ratio between the sensor signal and a further signal.

15. The hob apparatus of claim 14, embodied as an induction hob apparatus.

16. The hob apparatus of claim 14, further comprising a plate unit arranged above the heating unit and including at least part of the sensor unit.

17. The hob apparatus of claim 14, further comprising a holding unit configured to attach a heating element of the heating unit and at least one part of the sensor unit to one another.

18. The hob apparatus of claim 14, wherein the control unit includes a signal generation unit to generate a signal for controlling the sensor unit.

19. The hob apparatus of claim 18, wherein the control unit includes a signal amplification unit for amplifying the signal and for increasing the signal to noise ratio in respect of an interference signal.

20. The hob apparatus of claim 18, wherein the signal has a frequency which corresponds substantially to a resonant frequency of the resonant circuit.

21. The hob apparatus of claim 14, wherein the control unit is configured to store a reference signal, which comprises a difference between a variable of the sensor signal and a variable of the further signal measured in a reference state.

22. The hob apparatus of claim 14, wherein the control unit includes a detection unit for detecting the phase shift and/or an amplitude.

23. The hob apparatus of claim 22, wherein the detection unit is configured as a lock-in amplifier.

24. The hob apparatus of claim 14, wherein the control unit is configured in at least one of two ways for determining the state variable in the operating state, a first way in which the control unit compares a phase angle of the sensor signal with a phase angle of the further signal, a second way in which the control unit compares an amplitude of the sensor signal with an amplitude of the further signal.

25. The hob apparatus of claim 21, wherein the control unit is configured to vary the frequency of the signal until a phase angle of the sensor signal and a phase angle of the reference signal correspond for determining the state variable in the operating state.

26. A hob, comprising a hob apparatus, said hob apparatus comprising a heating unit, a sensor unit separate from the heating unit and configured to include an electric resonant circuit and to detect a sensor signal, and a control unit configured to control the sensor unit and to analyze the sensor signal, wherein the control unit determines in an operating state a state variable relating to the heating unit based on a phase shift and/or an amplitude ratio between the sensor signal and a further signal.

28. A method for operating a hob apparatus including a heating unit and a sensor unit arranged separate from the heating unit and including an electric resonant circuit, said method comprising: detecting by the sensor unit a sensor signal; and determining a state variable relating to the heating unit based on a phase shift and/or an amplitude ratio between the sensor signal and a further signal.

29. The method of claim 28, further comprising generating with a signal generation unit a signal for controlling the sensor unit.

30. The method of claim 28, further comprising storing a reference signal, which comprises a difference between a variable of the sensor signal and a variable of the further signal measured in a reference state.

31. The method of claim 28, further comprising detecting the phase shift and/or an amplitude.

32. The method of claim 28, further comprising comparing a phase angle of the sensor signal with a phase angle of the further signal and/or an amplitude of the sensor signal with an amplitude of the further signal for determining the state variable in the operating state.

33. The method of claim 30, further comprising varying a frequency of the signal until a phase angle of the sensor signal and a phase angle of the reference signal correspond for determining the state variable in the operating state.

Description

[0029] In the drawing:

[0030] FIG. 1 shows a schematic top view of a hob with a hob apparatus, comprising a heating unit, a sensor unit and a control unit,

[0031] FIG. 2 shows a schematic exploded view of the hob apparatus with a plate unit arranged above the heating unit,

[0032] FIG. 3 shows a schematic electrical circuit diagram of an electric resonant circuit of the sensor unit,

[0033] FIG. 4 shows two schematic diagrams of a sensor signal detected by the sensor unit and a reference signal,

[0034] FIG. 5 shows a schematic diagram of the control unit,

[0035] FIG. 6 shows a schematic flow diagram of a method for operating the hob apparatus,

[0036] FIG. 7 shows a schematic diagram of a holding unit for a further exemplary embodiment of a hob apparatus, and

[0037] FIG. 8 shows a schematic diagram of a control unit for a further exemplary embodiment of a hob apparatus.

[0038] FIG. 1 shows a schematic top view of a hob 42a. The hob 42a is configured as an induction hob. The hob 42a has a hob apparatus 10a. The hob apparatus 10a is configured as an induction hob apparatus. The hob apparatus 10a comprises a heating unit 12a. The heating unit 12a has a plurality of heating elements 32a, each of which is configured as an induction heating element.

[0039] Where a number of objects is present only one is shown with a reference character in the figures.

[0040] The hob apparatus 10a comprises a sensor unit 14a. The sensor unit 14a is separate from the heating unit 12a. The sensor unit 14a has an electric resonant circuit 16a (see FIG. 3). The sensor unit 14a is provided for detecting a sensor signal 18a (see FIG. 4).

[0041] The hob apparatus 10a comprises a control unit 20a. The control unit 20a is provided for controlling the sensor unit 14a. The control unit 20a is provided for analyzing the sensor signal 18a. When the hob apparatus 10a is in an operating state the control unit 20a determines at least one state variable 22a relating to the heating unit 12a (see FIG. 5) based on a phase shift 24a and/or an amplitude ratio between the sensor signal 18a and a further signal.

[0042] A reference signal 26a is stored in the control unit 20a. The reference signal 20a comprises a difference between a variable of the sensor signal 18a and a variable of the further signal measured in a reference state. The variable of the sensor signal 18a here is a phase angle and the variable of the further signal is a further phase angle.

[0043] FIG. 2 shows a schematic exploded view of the hob apparatus 10a. The hob apparatus 10a has a plate unit 28a. When the hob apparatus 10a is in an assembled state, the plate unit 28a is arranged above the heating unit 12a and below a hob plate 62a of the hob 42a. The plate unit 28a includes at least part of the sensor unit 14a. The plate unit 28a includes the resonant circuit 16a of the sensor unit 14a. The resonant circuit 16a of the sensor unit 14a is attached to a printed circuit board, which is connected to the plate unit 28a.

[0044] FIG. 3 shows a schematic electrical circuit diagram of the sensor unit 14a. The sensor unit 14a comprises the electric resonant circuit 16a. The sensor unit 14a comprises a signal input 44a and a signal output 46a, each of which is connected in an electrically conducting manner to the electric resonant circuit 16a. The electric resonant circuit 46a comprises an electrical resistance 48a, an induction coil 50a and a capacitor 52a.

[0045] The signal input 44a of the sensor unit 14a is connected in an electrically conducting manner to a signal amplification unit 38a and to a signal generation unit 34a of the control unit 20a. In an operating state a signal generated by means of the signal generation unit 34a and amplified by means of the signal amplification unit 38a is fed into the electric resonant circuit 16a by way of the signal input 44a. The signal output 46a is configured as an electrical shunt resistor 64a.

[0046] FIG. 4 shows two diagrams. A frequency in megahertz is shown on an x-axis 54a of the left-hand diagram. A value of an impedance in ohms is shown on a y-axis 56a of the left-hand diagram. The left-hand diagram shows the reference signal 26a with a solid line. The left-hand diagram shows the sensor signal 18a with a broken line. The value of the impedance of the reference signal is at a maximum at a resonant frequency 66a of the resonant circuit.

[0047] The frequency in megahertz is shown on an x-axis 58a of the right-hand diagram. A phase angle is shown on a y-axis 60a of the right-hand diagram. The right-hand diagram shows the reference signal 26a with a solid line. The left-hand diagram shows the sensor signal 18a with a broken line. A phase angle of the reference signal 26a, which can be measured in the electric resonant circuit 16a of the sensor unit 14a in a reference state at the resonant frequency 66a, is for example 20°. A phase angle of the sensor signal 18a, which can be measured in the electric resonant circuit 16a of the sensor unit 14a when the hob apparatus 10a is in an operating state, in which cookware (not shown) is positioned above the sensor unit 14a, at the resonant frequency 66a, is for example −20°. This results in the phase shift 24a, in this example 40°.

[0048] The sensor signal 18a describes a ratio between a signal 36a (see FIG. 5) and an output signal 92a of the electric resonant circuit 16a and can be considered as an equivalent impedance of the electric resonant circuit 16a in the operating state. The reference signal 26a can be considered as an equivalent impedance of the electric resonant circuit 16a in the reference state.

[0049] FIG. 5 shows a schematic diagram of the control unit 20a. The control unit 20a includes the signal generation unit 34a. The signal generation unit 34a is provided for generating the signal 36a for controlling the sensor unit 14a.

[0050] The control unit 20a includes the signal amplification unit 38a. The signal amplification unit 38a is provided for amplifying the signal 36a and increasing a signal to noise ratio in respect of interference signals. Interference signals could be caused in the operating state for example by an electromagnetic field supplied by a heating element 32a of the heating unit 12a for heating purposes.

[0051] In the operating state the signal 36a generated by means of the signal generation unit 34a and amplified by means of the signal amplification unit 38a is fed into the electric resonant circuit 16a of the sensor unit 14a by way of the signal input 44a (see FIG. 3). The signal 36a has a frequency, which corresponds substantially to the resonant frequency 66a of the electric resonant circuit 16a. The resonant frequency 66a is stored in a storage unit 70a of the control unit 20a and is sent to the signal generation unit 34a for generating the signal 36a in the operating state.

[0052] The control unit 20a has a detection unit 40a. The detection unit 40a is provided for detecting the phase shift 24a and/or an amplitude. The detection unit 40a is configured as a lock-in amplifier. A voltage dropping at the signal output 46a configured as an electrical shunt resistor 64a in the operating state can be detected as the output signal 92a and is sent to the detection unit 40a. The signal 36a is also sent to the detection unit 40a.

[0053] To determine the state variable 24a in the operating state the control unit 20a compares a phase angle and/or amplitude of the sensor signal 18a and a phase angle and/or amplitude of the reference signal 26a. In the present exemplary embodiment the phase angle comparison is carried out by means of the detection unit 40a. In the operating state the detection unit 40a detects the phase shift 24a and sends this to the computation unit 68a of the control unit 20a. The reference signal 26a is stored in the storage unit 70a. In the operating state the computation unit 68a accesses the storage unit 70a and determines the state variable based on the phase shift 24a between the sensor signal 18a and the further signal. In the present exemplary embodiment the state variable 24a contains for example information about a degree of cover of a heating element 32a of the heating unit 12a (see FIG. 1) by cookware (not shown).

[0054] FIG. 6 shows a schematic flow diagram of a method for operating the hob apparatus 10a. In the method the at least one sensor signal 18a is detected and at least the state variable 22a relating to the heating unit 12a is determined based on the phase shift 24a and/or amplitude ratio between the sensor signal 18a and the further signal, which is stored as the reference signal 26a in the control unit. The method comprises a number of method steps. In a method step 80a a microprocessor in the signal generation unit 34a generates a rectangular signal. In a further method step 82a the rectangular signal is converted to the signal 36a by means of the signal generation unit 34a. The signal 36a is now sinusoidal and is sent to the signal amplification unit 38a. In a further method step 84a the signal 36a is amplified and then fed into the electric resonant circuit 16a of the sensor unit 14a by way of the signal input 44a (see FIG. 3) and sent to the detection unit 40a. In a further method step 86a the output signal 92a at the signal output 46a of the electric resonant circuit is detected and sent to the detection unit 40a. In a further method step 88a the detection unit 40a detects the phase shift 24a between the sensor signal 18a and the stored further signal and sends this to the computation unit 68a of the control unit 20a. In a further method step 90a the computation unit 68a determines the state variable 22a based on the phase shift 24a.

[0055] FIGS. 7 and 8 show two further exemplary embodiments of the invention. The descriptions that follow are restricted substantially to the differences between the exemplary embodiments, it being possible to refer to the description of the exemplary embodiment in FIGS. 1 to 6 for components, features and functions that remain the same. To distinguish between the exemplary embodiments the letter a in the reference characters of the exemplary embodiment in FIGS. 1 to 6 is replaced by the letters b and c in the reference characters of the exemplary embodiments in FIGS. 7 and 8. Reference can also be made in principle to the drawings and/or the description of the exemplary embodiment in FIGS. 1 to 6 for components of identical designation, in particular for components with identical reference characters.

[0056] FIG. 7 shows a schematic diagram of a holding unit 30b of a hob apparatus 10b. The hob apparatus 10b has a sensor unit 14b and a heating unit 12b. The holding unit 30b attaches a heating element 32b of the heating unit 12b and at least a part of the sensor unit 14b to one another. The hob apparatus 10b differs from the hob apparatus 10a of the preceding exemplary embodiment substantially in respect of an arrangement of the sensor unit 14b. Reference should be made here to the above description of the exemplary embodiment in FIGS. 1 to 6 for a mode of operation of the hob apparatus 10b.

[0057] The holding unit 30b comprises a first holding element 76b and a second holding element 78b. An induction coil 50b of the sensor unit 14b is attached to the first holding element 76b of the holding unit 30b. The heating element 32b of the heating unit 12b is attached to the second holding element 78b of the holding unit 30b. The first holding element 76b and the second holding element 78b are connected to one another and form the holding unit 30b in an assembled state.

[0058] FIG. 8 shows a further exemplary embodiment of a hob apparatus 10c. The hob apparatus 10c differs from the hob apparatus 10a of the exemplary embodiment in FIGS. 1 to 6 substantially in respect of an embodiment of a control unit 20c. Reference should be made here to the above description of the exemplary embodiment in FIGS. 1 to 6 for further components of the hob apparatus 10c.

[0059] FIG. 8 shows a schematic diagram of the control unit 20c. When the hob apparatus 10c is in an operating state, the control unit 20c determines at least one state variable 22c based on a phase shift 24c between a sensor signal 18c and a stored reference signal 26c. When the hob apparatus 10c is in the operating state the control unit 20c determines the state variable 22c by varying a frequency 94c of a signal 36c until a phase angle of the sensor signal 18c and a phase angle of the reference signal 26c correspond.

[0060] The control unit 20c has a signal generation unit 34c, which is provided for generating the signal 26c for controlling a sensor unit 14c. When the hob apparatus 10c is in the operating state, the signal generation unit 34c generates the signal 36c initially based on a resonant frequency 66c stored in a storage unit 70c of the control unit 20c and sends the signal 36c to the sensor unit 14c and a detection unit 40c of the control unit 20c. The detection unit 40c determines the phase shift 24c from the signal 36c and an output signal 92c of the sensor unit 14c. While the phase shift 24c has a value that is not zero, the control unit 20c varies the frequency 94c, by sending either a frequency decrease 72c or a frequency increase 74c to the signal generation unit 34c. When the phase angle of the sensor signal 18c and the phase angle of the reference signal 26c correspond, in other words the phase shift 24c is zero, the control unit 20c stores the associated frequency 94c in the storage unit 70c. A computation unit 68c of the control unit 20c accesses the storage unit 20c, compares the frequency 94c with the resonant frequency 66c and determines the state variable 22 therefrom.

REFERENCE CHARACTERS

[0061] 10 Hob apparatus [0062] 12 Heating unit [0063] 14 Sensor unit [0064] 16 Resonant circuit [0065] 18 Sensor signal [0066] 20 Control unit [0067] 22 State variable [0068] 24 Phase shift [0069] 26 Reference signal [0070] 28 Plate unit [0071] 30 Holding unit [0072] 32 Heating element [0073] 34 Signal generation unit [0074] 36 Signal [0075] 38 Signal amplification unit [0076] 40 Detection unit [0077] 42 Hob [0078] 44 Signal input [0079] 46 Signal output [0080] 48 Electrical resistance [0081] 50 Induction coil [0082] 52 Capacitor [0083] 54 x-axis [0084] 56 y-axis [0085] 58 x-axis [0086] 60 y-axis [0087] 62 Hob plate [0088] 64 Electrical shunt resistor [0089] 66 Resonant frequency [0090] 68 Computation unit [0091] 70 Storage unit [0092] 72 Frequency decrease [0093] 74 Frequency increase [0094] 76 Holding element [0095] 78 Holding element [0096] 80 Method step [0097] 82 Further method step [0098] 84 Further method step [0099] 86 Further method step [0100] 88 Further method step [0101] 90 Further method step [0102] 92 Output signal [0103] 94 Frequency