GB2100883A

GB2100883A - An arrangement for the determination of temperature in cooking apparatus

Info

Publication number: GB2100883A
Application number: GB08213460A
Authority: GB
Inventors: Dr Hartmut Dittrich; Arno Bauer
Original assignee: Diehl GmbH and Co
Current assignee: Diehl Verwaltungs Stiftung
Priority date: 1981-05-09
Filing date: 1982-05-10
Publication date: 1983-01-06
Also published as: FR2505597A1; DE3118399A1; FR2505597B1; DE3118399C2; GB2100883B

Abstract

For a cooker having electrically- heatable hot-plates, a circuit arrangement (2) for the sensorless ascertainment of temperature is proposed which consists of a calculating part (12), a store arrangement (13) and an interface for a display arrangement (3). The store arrangement (13) contains data regarding the heating up period and the cooking and the time, as well as preferably also data regarding the cooling-down curves of the hot plates. From this data, as well as the switch- on duration of the heating arrangements (6), by means of the calculating part (12) the respective temperature of the hot-plates is ascertainable; moreover, preferably by means of the display arrangement (3) for different temperature ranges different symbols are displayed. <IMAGE>

Description

SPECIFICATION An arrangement for the determination of temperature in cooking apparatus The invention relates to an arrangement for the determination of temperature in cooking apparatus in which the temperature of a heating element, for example, a hot-plate may be determined without sensing the temperature of the element itself.

Such arrangements are known, for example, from German Offenlegungsschrift No. 28 08 181 which shows a glass-ceramic cooking panel defining several hot-plates, the temperature of which is determined by a simulation arrangement.

For this purpose, a heating resistor having two bimetal spring snap-action switches is used, which resistor is accommodated in a common, heat-insulated housing. If one or more of the heating units belonging to the hot-plates are switched on, then the heating resistor is automatically switched on, and heats the simulation arrangement. One of the two bimetal spring switches snaps the heating resistor off once more when an upper limiting temperature is reached. The second bimetal switch, above a specific lower temperature, switches a lamp on as a warning display. The heat insulation of the housing is so designed that the time which is needed for the lamp to be switched off corresponds to the time in which the glassceramic cooking panel is cooled down from its highest temperature as far as a predetermined temperature of about 700C.

Furthermore, it is proposed therein that the simulation arrangement, preferably, be arranged directly underneath the cooking panel so that when all the heating units have been switched on for a long time period, through the thermal action of the panel on the simulation arrangement an additional delay in cooling-down of the arrangement and therefore in the lamp being switched off is achieved. Finally, it is additionally proposed to replace the bimetal snap-action springs by other temperature-sensitive component parts, such as, for example, temperature dependent resistors with positive temperature co-efficients.

In this arrangement, it is not the temperature of a specific hot-plate which is determined, since it can only be determined that over the entire area of the glass-ceramic cooking panel no point exceeds a temperature of, for example, 700C.

More especially in the case of the cooling-down duration the maximum achievable temperature of the hot-plates is always taken as a basis, and not the temperature of the individual hot-plates actually achieved.

In contrast, an object of the present invention is to provide an arrangement and method which (with knowledge of the technical and thermal parameters of the heating element or elements, for example of the hot-plates and of the heating arrangements) is capable of determining the temperature of an individual heating element or part. Furthermore, this may be possible without incorporating a special heat source underneath the cooking panel, and additionally the arrangement for temperature determination may be so connectable to an already existing power control that circuit parts thereof can be jointly used. Also, an arrangement for controlling a display arrangement of the cooking apparatus may be usable which, after the power supply to, for example, the hot-plates is switched off, makes possible a utilisation of the existing residual heat in order to save energy.

According to the present invention there is provided an arrangement for the determination of temperature for cooking apparatus having one or more heating elements, for example, hot-plates with electrical heating arrangements, with an input arrangement and a switching arrangement, by which the heating arrangements are settable to several switching stages, said temperature determination arrangement comprising a circuit arrangement for determining a predetermined temperature of the heating elements with the heating arrangements switched off, characterised in that the circuit arrangement consists of a calculating part, and of a store arrangement and of an interface for a display arrangement, in that the calculating part is connected to an operating arrangement, in that the store arrangement contains data regarding cooking performance, for example ANKOCH "heating up or cooking boost period" duration and the FORTKOCH ("cooking on period") duration for the various switching stages, and in that through the circuit arrangement by virtue of further data, stored in the store arrangement and/or in the calculating part, regarding the switch-on duration of the individual heating arrangements, as well as of the set switching stages, the temperature of respective heating elements with the heating arrangements switched on and off can be determined.

It is an advantage of the present invention that an electronic circuit arrangement for determining the temperature of the hot-plate may be used which neigher needs a temperature sensor nor has to be arranged in the vicinity of, for example, the hot-plates.

Further advantages can be gathered from the sub-claims.

Thus, the calculating part and the store part of the arrangement may be used to control the power supply to the heating arrangement of the hot-plates. More especially a microprocessor can be used as the calculating part, or a one-chip microcomputer which, together with suitable interface switching replaces the circuit arrangement.

The temperature determination arrangement can be used to control a display arrangement which informs a user about the residual heat of an individual hot-plate, and thus makes possible a special energy-saving operation.

Further according to the present invention there is provided cooking apparatus comprising a temperature determination arrangement having: an information store; a calculating part; an operating arrangement; and timing means; said temperature determination arrangement being adapted to determine the temperature of a, or of a respective, heating element of the apparatus without using a sensor in co-operation with said element, the information store and calculating part having sufficient information, in use, to enable the calculating part to calculate the temperature of said element after a period of time measured by the timing means, the calculating part being responsive to a switching stage selected for said heating element on the operating arrangement and responsive to said timing means to determine the temperature of said element using information from the store and said calculating part being capable of issuing control signals based thereon to control, for example a residual heat display and/or warning display and/or the power supplied to said heating element.

Still further according to the present invention there is provided a method of determining the temperature of at least one individually defined heating element, for example a hot plate, of cooking apparatus, and issuing control signals based thereon, the method comprising: a) manually setting an operating arrangement to select a switch-on switching stage for the or each heating element, the switching stage being selected by way of a circuit arrangement which produces control signals to control a switching arrangement connected to the or each heating element, b) timing how long the or each element has been switched on by using timing means, for example, an integrated clock, c) In a calculating part of the circuit arrangement comparing the length of time the or each element has been switched on with stored information in the circuit arrangement regarding technical and thermal parameters of the or each heating element and enough other information, for example regarding the type of power supply associated with possible switching stages selectable, in order to enable the temperature of the or each element to be determined without sensing the temperature of the or each element, and thereby determining the temperature of the or each heating element, d) issuing control signals based on said temperature determination from the circuit arrangement to control, for example a residual heat display and/or warning display of said cooking apparatus and/or the power supplied to the or each heating element.

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a block schematic circuit diagram of a cooker with an electronic circuit for the power control and for sensorless temperature determination; Figure 2 shows a block schematic circuit diagram of the electronic circuit in accordance with Figure 1; Figure 3 shows a block schematic circuit diagram of a further preferred electronic circuit in accordance with Figure 1; Figure 4 shows a preferred circuit arrangement for temperature determination with a microcomputer.

Shown schematically in Figure 1 is a cooker 1, with a circuit arrangement 2, a display arrangement 3, an operating arrangement 4, and with a switching arrangement 5 for regulating the power supply to a heating arrangement 6 associated with a heating element or elements of the cooker, for example, a hot-plate. The heating element may be in an oven, or other heating portion of a cooker.

The operating arrangement 4 serves for the manual setting of the desired switching stage (as later defined), and for switching on and off the hot-plates, and controls, by way of input lines 7, the circuit arrangement 2. The circuit arrangement 2 produces, in accordance with the selected switching stage, first control signals which, by way of control lines 8, control the switching arrangement 5. The switching arrangement 5 is connected by way of mains lines 9 to the current mains and regulates, in accordance with the first control signals produced in the circuit arrangement 2, the power supply to the heating arrangement 6, which is connected by way of power supply lines 10 to the switching arrangement 5. Furthermore, the circuit arrangement 2 produces second control signals for controlling the display arrangement 3 by way of display lines 11.

The phrase "switching stage" refers here to both a temperature stage and a power stage, i.e.

with a specific switching position which can be introduced by means of the operating arrangement 4 there is associated therewith both a specific end temperature setting of the hot-plate and a specific power supply setting, without definition of the achievable end temperature of the hot-plate.

The function of the circuit arrangement 2 in accordance with the invention will now be explained hereinunder with reference to Figures 2 and 3.

Figure 2 shows the circuit arrangement 2, consisting of a calculating part 12, a store arrangement 13, and an interface 14 for the display arrangement 3. The calculating part 12 is controlled by way of the input lines 7 by the operating arrangement 4 in accordance with the set switching stage. Furthermore, the calculating part 12 is connected by way of command and data lines 1 5 to the store arrangement. Moreover, the calculating part 12 has at its disposal the interface 14 which, by way of the display lines 11 controls the display arrangement 3.

As has already been mentioned above, the circuit arrangement 2, or respectively the calculating part 12, is controlled by way of the input lines 7 by means of the operating arrangement 4. If now a specific switching position is introduced at the operating arrangement 4, then there is fed to the calculating part 12, by way of the input lines 7, a signal by which the part 1 2 can associate the selected switching position. Contained in the store arrangement 13 are items of information regarding the type of the power supply to the heating arrangements 6, which information is associated with the selected switching position.

For example, the duration of the "heating up or cooking boost period", i.e. that period of time at the start of a cooking operation during which the maximum power is fed to the heating arrangement 6, and moreover of the "cooking on period" period can be stored, i.e. in the case of a clocked or cycled power supply the period duration and the pulse-interval ratio of a timing step. From this information contained in the store arrangement 13 the calculating part 12 produces control signals for controlling the switching arrangement 5 by way of the control line 8, which switching arrangement 5 then accordingly switches the power supply to the heating arrangement 6. Furthermore, the calculating part 12 ascertains, for example by means of an integrated clock, the switch-on duration of the heating arrangement 6.Stored away in the store arrangement 1 3 are further items of information regarding the technical and thermal parameters of the hot-plate. With the aid of these parameters, the calculating part 12 is in a position to calculate the temperature of the hot-plate from the timed switch-on duration of the heating arrangement 6 as well as from the selected switching stage.

Since the circuit arrangement 2 receives no information of any kind regarding the actual temperature of the hot-plate by, for example, a sensor, it is necessary, upon calculation of the temperature during heating-up of the hot-plate, to begin calculating from a specific initial temperature of the hot-plate.

In this embodiment allowance is made for the fact that after a specific time, the hot-plate will have cooled down to room temperature.

Allowance is also made for the fact that a hotplate may again be switched-on before it has cooled-down to room temperature, as when the hot-plate is switched on and off and on again at short intervals. For this reason it is preferable also to calculate the temperature of the hot-plate after the power supply has been cut-off to the heating arrangements 6. These values can then in the appropriate circumstances serve as initial values for the temperature calculation when a hot-plate is switched on again. In a preferred development of the circuit arrangement 2, stored therefore in the store arrangement 14 is a table of coolingdown curves of the hot-plates or equivalent information. By means of these cooling-down curves or equivalent information the calculating part 12 is able to calculate the temperature of the hot-plates when the heating arrangements 6 are switched on and off.Similarly, allowance can be made for a change of the switching stage for the hot-plate in which respect the temperature reached in the first switching stage may serve as initial value for the calculation of the temperature in the new switching stage.

As has been mentioned above, the calculating part 12 has an interface 14 which by way of display line 11 controls the display arrangement 3. The calculating part 12 can thus, in accordance with a preset programme, produce different displays on the display arrangement 3. With the heating arrangements 6 switched off, the display arrangement 3 can in the simplest case show a symbol for "switched off" or no display at all may appear. With the heating arrangements 6 switched on, in accordance with the selected switching position symbols can be displayed which are associated with this switching position.

These symbols may be, for example, consecutive numbers in accordance with the number of possible switching stages.

Moreover, it is possible to display the hot-plate temperatures calculated by the calculating part 12; this may be a numerical value, so that on the display arrangement 3, for example, the value "1 500 C" is shown. The display is, preferably, variable in accordance with the accuracy of the determined temperature values in 10 or 20 degree steps. Furthermore, it is possible to use consecutive numbers for displaying the temperature, in which respect the individual numbers are associated with a specjfic temperature range; for example, in the case of a hot-plate temperature between 1400C and 1 600C a "7" is displayed. The individual numbers are, preferably, associated with the end temperatures achievable by the hot-plate in the respective switching stage with the same number.Also, for the display of temperature, specific symbols may be used which are associated with the expressions customary to the cooking operation. As an example, upon use of a suitable display arrangement 3 (for example 16segment or matrix display arrangements) the temperature ranges associated with the three expressions "FORTKOCHEN" (cooking on period"), "GAREN" (medium heat or simmering) and "WARMHALTEN" (low heat) can be represented by display of the initial letters F, G, W. With a seven-segment display arrangement, to display the temperature exclusively three horizontai bars can be utilised, in which respect three bars correspond to the temperature range "FORTKOCHEN", two bars correspond to the temperature range "GAREN" and one bar corresponds to the temperature range "WARMHALTEN".

The display of temperature of the hot-plate can now be effected manually by the user, either with the heating arrangements 6 switched on and off, or else permanently. In a preferred development, for the display of the selected switching stage and for the display of the determined temperature the same display element in the display arrangement 3 is used. This display element may work, for example, intermittently, i.e. it displays, with the heating arrangements 6 switched on, alternatively the switching stage and the determined temperature, whilst with the heating arrangements 6 switched off the display of the temperature can be effected permanently or intermittently, in which respect, upon intermittent operation, the display of the temperature can alternate with the display of the symbol for "switched off".To improve the distinguishability of the display of the switching stage and the display of the determined temperature, a display arrangement 3 which can be changed over to two different colours can be used; for example, the display of the switching stage is shown in red, and the display of the determined temperature in yellow.

The use of the display arrangement 3 to display the residual heat after the heating arrangements 6 are switched off makes possible the controlled utilisation of this residual heat for a further cooking operation or for keeping hot and thus serve to save energy.

Figure 3 shows a block diagram of a further preferred circuit arrangement 2, which corresponds generally to the block diagram in accordance with Figure 2. As compared with Figure 2 here, however, additionally a timing production circuit 1 6 is provided, which is connected by way of a timing line 1 7 to the calculating part 12. The timing signal produced by this timing production circuit 1 6 is fed to the calculating part 12 for ascertaining the switch-on duration of the heating arrangement 6 and for establishing the period of time which has elapsed after the power supply is switched off.In this respect, the timing production circuit 1 6 is, preferably, connected directly by way of a further mains line 1 8 or by way of a transformer to the current mains, and derives the timing signal directly from the mains frequency. As compared with the integrated clock mentioned in the description regarding Figure 2, this represents a considerably reduced component expenditure. It is only necessary to provide, in the programme for the calculating part 12, a programme part for the counting of the timing impuises. From this count state, in a simple manner the time which has elapsed can be ascertained.

Figure 4 shows a preferred exemplary embodiment of the arrangement for the determination of temperature with a microcomputer 1 9 from the series TMS 1000.

The references, used in Figure 4, of the connections of the microcomputer 1 9 are from the "TMS 1000 Series Data Manual" of Texas Instruments.

The microcomputer 1 9 replaces, in circuit respects, the calculating part 12, the store arrangement 1 3 and the interface 14 in the circuit arrangement 2 in accordance with Figure 3. The outputs 00 to 07 and RO to R3 of the microcomputer 1 9 are connected by way of display lines 11 to the display arrangement 3.

Preferably, in this case there can be used as display arrangement 3 fluorescent displays which can then be controlled without a driver circuit directly from the microcomputer 19. The outputs R4 to R7 of the micro-computer 19 control, by way of the control lines 8, the switching arrangement 5. The switching arrangement 5 contains several interface circuits consisting of a transistor 20 and a relay 21, in which respect here only one interface circuit is shown. The base of the transistor 20 is controlled directly from the output R7 of the microcomputer 19. The emitter of the transistor 20 is connected by way of the coil of the relay 21 to the earth pole of a voltage stabilisation circuit 22, the collector is connected to the positive pole U55 of the voltage stabilisation circuit 22.The switch of the relay 21 is connected into one of the power supply lines 10 and can interrupt the power supply to the heating arrangement 6. The heating arrangement 6 consists of a heating resistor 23, which is coupled thermally to a load 24, consisting of a hot-plate, pot or other cooking element.

Furthermore, a transformer 25 is connected at the primary side by way of mains lines 9 to the current mains. On the secondary side, the transformer 25 is connected by way of a bridge rectifier 26 in a conventional circuit to the voltage stabilisation circuit 22. The voltage stabilisation circuit 22 supplies the positive voltage Uss and a negative voltage UDE), and a further output signal INIT for resetting the microcomputer 1 9 by way of the input INIT thereof, for example after switching-on.

The transformer 25 is additionally connected, on the secondary side, by way of the further mains line 18 to the timing production circuit 16.

The timing production circuit 1 6 produces, preferably, a 50 Kz timing, which serves as time base for measuring, for example, the switch-on duration of the heating arrangement 6. This 50 Hz timing is fed by way of the timing line 17 to the input K 8 of the microcomputer 19. The timing production circuit 1 6 consists, preferably, of a rectifier diode 27 and a current limiting resistor 28 connected in series, and at the output of the timing production circuit 1 6 is an additional capacitor 29 connected to earth.

The connections OSC 1 and OSC 2 of the microcomputer are connected, and are connected by way of a resistor 30 to the output UDD, and by way of a further capacitor 31 to the output Uss of the voltage stabilisation circuit 22. The voltage supply inputs Uss, or respectively UDD of the microcomputer 1 9 are connected to the corresponding outputs of the voltage stabilisation circuit 22.

The inputs K1 and K4, as well as the outputs R9 and R10 of the microcomputer 19 are connected by way of the input line 7 to the operating arrangement 4. The operating arrangement 4 consists, preferably, of a keyboard or control panel, which can be connected to a buffer store. An input is called up by commands which are issued by way of the outputs R9 and R10 of the microcomputer 19, ana are read in by way of the inputs K1, K2 and K4 of the microcomputer 19.

The output R8 of the microcomputer 19, which is not connected-lip in Figure 4, can in a preferred manner < carve to control an arrangement which issues acoustic signals, for example as t warning which may signal input error.

The function of the circuit arrangement in accordance with Figure 4 corresponds to the description given in the case of the preceding figures.

Claims

1. An arrangement for the determination of temperature for cooking apparatus having one or more heating elements, for example, hot-plates with electrical heating arrangements, with an input arrangement and a switching arrangement, by which the heating arrangements are settable to several switching stages, said temperature determination arrangement comprising a circuit arrangement for determining a predetermined temperature of the heating elements with the heating arrangements switched off, characterised in that the circuit arrangement consists of a calculating part, and of a store arrangement and of an interface for a display arrangement, in that the calculating part is connected to an operating arrangement, in that the store arrangement contains data regarding cooking performance, for example ANKOCH ("heating up or cooking boost period") duration and the FORTKOCH ("cooking on period") duration for the various switching stages, and in that through the circuit arrangement, by virtue of further data, stored in the store arrangement and/or in the calculating part, regarding the switch-on duration of the individual heating arrangements, as well as of the set switching stages, the temperature of respective heating elements with the heating arrangements switched on and off can be determined.

2. An arrangement as claimed in Claim 1 in which the calculating part is connected to the store arrangement by way of command and data lines, in that the calculating part is connected to a timing production circuit, and in that through the calculating part the switch-on duration of the individual heating arrangements is determinable.

3. An arrangement as claimed in Claim 1 or Claim 2, in which the calculating part is connected to a switching arrangement for regulating the power supply to the heating arrangements.

4. An arrangement as claimed in Claim 3, in which the switching arrangement is controllable by the calculating part with reference to the data deposited in the store arrangement, in which respect the data associated with the switching stage is introduced by means of the operating arrangement.

5. An arrangement as claimed in any one of Claims 2 to 4, in which through the timing production circuit a timing signal derived from the frequency of the power supply of the heating arrangement can be produced.

6. An arrangement as claimed in any one of Claims 1 to 5, in which the display arrangement is Sc ontrollable by way of the interface that for different presettable ranges of the temperature of the heating elements different symbols are representable.

7. An arrangement as claimed in Claim 6, in which the display of the temperature of the heating elements corresponds to that display which is associated with the switching stage at which. with the heating arrangements switched on, the same tempelature is achievable as end temperature.

8. An arrangement as claimed in Claim 6, in which the display of the temperature of the heating elements is distinguishable from the display of the switching stage by colouration, type of operation or selection of the symbols.

9. An arrangement as claimed in any one of Claims 1 to 8, in which a table of the cool-down curves of the heating elements is stored in the store arrangement.

10. An arrangement as claimed in any one of Claims 1 to 9, in which a microprocessor is used as the calculating part, and in that the store arrangement contains a work programme for the microprocessor.

11. Use of an arrangement as claimed in any one of Claims 1 to 10 to control a display arrangement for displaying various symbols which are associated with at least three consecutive ranges of the temperature of the heating element after the switching-off of the power supply.

12. Cooking apparatus comprising a temperature determination arrangement having: an information store; a calculating part; an operating arrangement; and timing means, said determination arrangement being adapted to determine the temperature of a, or of a respective, heating element of the apparatus without using a sensor in co-operation with said element, the information store and calculating part having sufficient information, in use, to enable the calculating part to calculate the temperature of said element after a period of time measured by the timing means, the calculating part being responsive to a switching stage selected for said heating element on the operating arrangement and responsive to said timing means to determine the temperature of said element using information from the store and said calculating part being capable of issuing control signals based thereon to control, for example a residal heating display and/or warning display and/or the power supplied to said heating element.

1 3. An arrangement for the determination of temperature substantially as herein described and illustrated with reference to Figures 1 and 2 or 1 and 3 or 1 and 4.

1 4. A method of determining the temperature of at least one individually defined heating element, for example a hot plate, of cooking apparatus, and issuing control signals based thereon, the method comprising: a) manually setting an operating arrangement to select a switch-on switching stage for the or each heating element, the switching stage being selected by way of a circuit arrangement which produces control signals to control a switching arrangement connected to the or each heating element, b) timing how long the or each element has been switched on by using timing means, for example, an integrated clock, c) in a calculating part of the circuit arrangement comparing the length of time the or each element has been switched on with stored information in the circuit arrangement regarding technical and thermal parameters of the or each heating element and enough other information, for example regarding the type of power supply associated with possible switching stages selectable, in order to enable the temperature of the or each element to be determined without sensing the temperature of the or each element, and thereby determining the temperature of the or each heating element, d) issuing control signals based on said temperature determination from the circuit arrangement to control, for example a residual heat display and/or warning display of said cooking apparatus and/or the power supplied to the or each heating element.

15. A method as claimed in Claim 14 substantially as herein described and illustrated with reference to Figures 1 and 2, or 1 and 3, or 1 and 4.