EP1448024B1 - Heating device with two areas - Google Patents

Abstract

Heating unit (11), especially for a cooker with a glass-ceramic hob, is divided into at least two heating regions (17, 19; 21). The first area is protected by a first excess-temperature fuse (13) and has a maximum power output, while the second region is not monitored by the excess-temperature fuse and has a maximum power output of approximately 2.5 W per cm2>.

Description

Field of application and state of the art

The invention relates to a heating device according to the preamble of claim 1 and a method for operating a heating device according to the preamble of claim 11. Such a heating device and such a method are particularly suitable for a hotplate with a glass ceramic hob.

The heating time or warm-up time for radiant heaters as heating devices depends on the one hand on a adjusted glass-ceramic surface temperature and the quality of the cookware used and on the other hand on the rated power of the radiant heater and thus its power density. In many cases, it is desirable to shorten this cooking time to achieve comfortable operation and fast cooking. However, the power density of a radiant heater can not be increased to infinity. at Radiant heaters with Bandheizleitern can be held at a certain power density, the heat conductor temperature is no longer within the specified limits.

Values for power densities in such radiant heaters are called, which represent a good compromise between the cooking time, quality of the cookware used and the heating conductor temperature. An advantageous power density can be close to 8 watts / cm ² . For radiant heaters with a nominal diameter of 140mm and 180mm, such a power density is used successfully.

However, this power density has certain limits. From a nominal diameter of the radiator of 210mm with a theoretical 2700 watts of power, the switching capacity of the electromechanical rod controller or protection temperature limiter, which represent the protection of the glass ceramic cooktop from overheating, exceeded. The switching capacity of the protection temperature limiter is at a certain current, which results from the predetermined mains voltage of 230 volts and a certain power value.

The US-A-4,327,280 describes a radiant heater with a round main area and a laterally adjoining additional area. A rod regulator overlaps the main area as an excess temperature fuse only. By contrast, the additional area is not overlapped by the bar regulator and thus can not be influenced by it.

The EP-A-0 551 172 describes a radiant heater with three concentric heated areas. A rod controller as over-temperature fuse covers all areas and extends far beyond the center, so that it is influenced by the temperature of all areas. All heating elements of the areas of the radiant heater are connected via the rod controller to a power supply, so that all areas and heating elements are monitored by the rod controller and in the event of an excess temperature at the rod controller are also switched off by this.

Task and solution

The invention has for its object to provide a heating device mentioned above and a method mentioned, with which the problems of the prior art can be avoided and in particular the size of a radiant heater regardless of the power density or a switching capacity of protection temperature limiters can be designed variable.

This object is achieved by a heating device with the features of claim 1 and by a method having the features of claim 11. Advantageous and preferred embodiments of the invention are the subject of further claims and are explained in more detail below. The wording of the claims is incorporated herein by express reference.

According to the invention, a heating device is divided into at least a first and a second region. A first area can be monitored by a first over-temperature fuse. This can be, for example, a rod regulator or a protective temperature limiter which at least partially overlaps or extends over this first region.

The first area has a maximum first power. This is matched to the above values. A second area of the heater is operated without monitoring by the first overtemperature fuse. In particular, the second area is operated at all without over-temperature protection. This is achieved by the maximum area coverage of the second area being approximately 2.5 watts / cm ² . Here it is possible to operate a radiant heater under a glass ceramic hob without rod controller or protection temperature limiter. With such a power value has been found within the scope of the invention that a conventional glass-ceramic is not endangered.

Thus, in a preferred embodiment of the invention, the heating device is divided into two areas, so to speak. A first area is operated at a critical power density and therefore must have a protection temperature limiter. This first range can be chosen so large that the protective temperature limiter can just manage or switch the resulting power. In order to increase beyond this maximum switchable power beyond the surface of the radiant heater, a second area is added. In any case, this second area is operated without monitoring by the over-temperature protection of the first area, preferably without any monitoring by an over-temperature fuse. For this purpose, a value is chosen as power density, which is technically possible and permissible for a glass ceramic.

Alternatively, a separate over-temperature fuse could be provided for the second area. Although this would increase the effort, but also improve security.

The second region may rest against the first region, advantageously at least along half the outer border. This results in an approximately elongated heater. Advantageously, the second region surrounds the first region, wherein they may be arranged concentrically. While the lateral connection of a second area to a first area corresponds approximately to a known elongated roaster heater, a concentric arrangement is advantageous for the use of either small or large round cookware.

In order to additionally increase the power of cooking, the power for the first range may be more than the standard power common to a radiant heater of this size. In particular, the power can approach the maximum value of the excess temperature fuse, for example a bar regulator. For example, a power for the first range of a maximum of 2500 or 2700 watts may be provided with a round area with a diameter of 230mm.

Furthermore, advantageously, the first region can have a switchable power, which can be connected to the basic power. It is provided that the maximum first power is present when the switchable power is also applied. Such a switchable power can be, for example, a parboiling or the like.

The power for the second range may be much lower, especially due to the lower power density. For example, 600 watts can be provided here. Since this power is advantageously present in the outer or edge region as a second region, in which also Cooking pots with not very even floor get up, this achievement is taken off in each case. Thus, excessive heating of a glass ceramic cooktop is avoided here. Furthermore, in the heating mode without pot, so if no heat output is removed, the glass ceramic in the edge region due to the larger area, the largest heat loss. This also protects it from overheating.

In a further embodiment of the invention, the heating device may have a control unit or be connected thereto. This control unit may have an additional contact for switching a basic power of the heating device or a switchable power for the first range to the total added maximum first power. Thus, the additional power can be defined and used for example as a boost.

Furthermore, the heating device may have an electronic control, for example with a touch switch arrangement for input. Another relay may be provided to switch the switchable power in addition to the base load to the total maximum first power.

Advantageously, a radiant heater which can have a heating conductor of resistance material is used as heating device. The heating conductor is preferably in a so-called flat band shape, wherein it is mounted upright on an insulating substrate and may be partially embedded therein.

These and other features are set forth in the description and drawings, with the individual features in each case alone or in the form of subcombinations in one embodiment of the invention and on others Be realized areas and can represent advantageous and protectable versions for which protection is claimed here.

Brief description of the drawings

Fig. 1

eine Draufsicht auf einen Strahlungsheizkörper mit einer Aufteilung in drei Heizbereiche sowie einem Stabregler und

Fig. 2

ein Wärmebild des Strahlungsheizkörpers aus Fig. 1 im Betrieb.

An embodiment of the invention is shown schematically in the drawings and will be explained in more detail below. In the drawings show:

Fig. 1

a plan view of a radiant heater with a division into three heating areas and a rod controller and

Fig. 2

a thermal image of the radiant heater of FIG. 1 in operation.

Detailed description of the embodiment

In Fig. 1, a radiant heater 11 is shown in plan view, as it is known per se. Its heated area is overlapped by a rod regulator 13. The temperature limiter or rod regulator 13 is fastened with its housing 14 on the side of the radiant heater 11. The sensor rod 15 protrudes in the radial direction over the center of the radiant heater 11 a piece out.

With this rod controller 13, an over-temperature protection is achieved by ensuring that the temperature generated above the radiant heater 11 at the bottom of a glass ceramic cooktop does not exceed a certain maximum temperature. This maximum permissible temperature is around 700 ° C. Such a rod controller and its function, for example, go from the DE 33 33 645 or the DE 34 23 086 out.

The heating region of the radiant heater 11 is subdivided into a first innermost region 17. The first region 17 is surrounded by an annular middle second region 19. This in turn is surrounded by a relatively narrow circumferential third region 21, which forms the outermost heating region.

The first region 17 is formed by first heating coils 18 which are laid in meandering fashion. This basic structure of a radiant heater is apparent for example from the EP 590 315 , to which expressly referred.

The second heating area 19 is formed by second heating coils 20. The third region 21 is again formed by third heating coils 22, which, as can be seen from FIG. 1, consist of a single loop.

The Heizwindungen 18, 20 and 22 are for example advantageously formed from a heating tape in an upright ribbon shape. They may be specially selected for their characteristics in order to achieve a given power distribution or operating area performance or overall performance. It can also be seen that the heating coils 18 of the first region 17 extend at a smaller distance from one another than the second heating coils 20 of the second region 19.

By means of a plurality of terminal lugs 24, the heating coils are connected to a power supply, for example power electronics or a so-called clocking energy regulator. The heating coils 18 and 20 of the first and second regions are each contacted via the uppermost terminal lug 24a, as can be seen. This terminal lug 24a is connected to the housing 14 of the rod controller 13. Your electrical connection is thus monitored by the rod controller 13 and interrupted in a case of over-temperature to turn off the first heating area 17 and the second heating area 19. As can be seen, although it is not possible by means of the rod controller 13 in this way a distinction between the first region 17 and the second region 19 in the overtemperature case. It would be possible in a further embodiment of the embodiment, to make such a distinction possible by a further rod controller. However, this does not matter for the invention in the frame discussed here.

The third heating coil 22 of the outer third region 21 is connected via the terminal lugs 24c and 24d. These are connected without the interposition of the rod controller 13 with a power supply. They are therefore not recognizable monitored by the rod controller 13 with respect to overtemperature.

function

Already from Fig. 1 it can be seen, as has been previously mentioned, that the heating coils of the first region 17 are more dense than in the two other areas, and in the area 19 again denser than in the third region 21. So there is a certain gradation. Already by this gradation is given a gradation of area performance, since the area performance is higher, the more dense heating coils of the same kind are laid.

Furthermore, as has also been mentioned above, by means of the special configuration of the individual heating conductors, their power and thus, in turn, the area output can be influenced.

FIG. 2 is a schematic thermal image of the radiant heater 11 of FIG. 1 in operation. FIG. Due to the different surface markings the temperature that prevails is displayed. The brighter, the higher the temperature. The gradation is 10 ° C per brightness level. The first area 17 is predominantly the brightest, the temperature here being between 545 ° C and 564 ° C and at about 555 ° C. The second region 19 has temperatures in the range of 524 ° C to 544 ° C. The third region 21 has predominantly temperatures in the range between 494 ° C and 514 ° C and about 500 ° C.

It should be noted here in comparison with the claims that the first region 17 and the second region 19 of the radiant heater 11 according to the embodiment of FIG. 1 correspond to the first region according to claim 1. The third region 21 of the radiant heater 11 corresponds to the second region according to claim 1.

As was already apparent from the description of FIG. 1, the first region 17 and the second region 19 can be activated separately. However, they are monitored jointly by the bar controller 13.

The radiant heater 11 is a two-circuit radiant heater. It has a diameter of 230 mm and a total nominal power of 2800 W. It accounts for the first area 17 1100 W, the second area 19 also 1100 W and the third area 21 600 W. This 600 W are the so-called unprotected or unregulated performance. From Fig. 2 it can be seen that here the temperature in about 50 ° to 60 ° lower than in the first or second region, which are centrally in the radiant heater 11. Further, the area power of the third region 21 is less than 2.5 W / cm ² , while the power density in the first and second regions is 7.8 W / cm ² .

By Fig. 2 is thus proven that with heating areas with the properties described above, ie in particular the outermost Heating area with low area performance, a radiant heater can be provided with additional power, which does not have to be controlled by a rod controller or not a single common rod controller.

In operation of the radiant heater, it is such that in single-circuit operation, only the first region 17 is active. In the two-circuit operation, the second region 19 and the third region 21 are electrically connected separately but temporally together.

Due to the fact that the power of the third region 21 does not have to be monitored by the rod controller 13 and therefore does not have to be switched off by the latter, its maximum switching limit can be maximized by the power of the first and second regions 17 and 19.

If the control of the heating areas at the terminal lugs 14 via a switching electronics, it is possible in a further embodiment of the invention to detect the response of the rod controller 13. Depending on this, the third heating area 21 could additionally be switched off in the same way, but not indirectly by the bar controller 13, but indirectly by its characteristic as a signal generator. Although this would not be necessary in every case because of the thermal surface load of the third region 21. However, this would allow a uniform operation of all heating areas, so that the glowing image of the radiant heater does not cause the outermost area to continue to glow brightly while the central area is dark.

Claims (13)

1. Heating device (11), particularly for a cooking point with a glass ceramic cooking area, which is subdivided into at least one first area (17, 19) and one second area (21), an excess temperature protection means (13) engaging over all the areas (17, 19, 21) for influencing and determining the temperature of the areas (17, 19, 21), a first area (17, 19) having a maximum, first power and is monitored by the excess temperature protection means (13) and for this purpose the first area (17, 19) is connected by means of the excess temperature protection means (13) to a power supply for disconnecting the first area (17, 19) in the case of an excess temperature, a second area (21) having a maximum surface heating power of approximately 2.5 W/cm², characterized in that the second area (21) is operated without monitoring by the first excess temperature protection means (13) and for this purpose is connected to a power supply without interconnection of the excess temperature protection means (13).
2. Heating device according to claim 1, characterized in that the second area (21) is operated entirely without monitoring by an excess temperature protection means and for this purpose is without excess temperature protection.
3. Heating device according to claim 1 or 2, characterized in that the second area (21) engages on the first area (17, 19) at least along half the outer border and preferably the second area surrounds the first area and in particular the areas are arranged concentrically.
4. Heating device according to claim 3, characterized in that the areas (17, 19, 21) are round, particularly circular.
5. Heating device according to one of the preceding claims, characterized in that the power for the first area (17, 19) is higher than the standard basic power for such a radiant heater (11) and is preferably max 2500 Watt in a round, first area with a diameter of 230 mm, the first area (17, 19) having a switched-in power, which can be switched into the basic power and in a state with said switched-in power said maximum first power is applied.
6. Heating device according to one of the preceding claims, characterized in that the power for the second area (21) is 600 Watt.
7. Heating device according to one of the preceding claims, characterized in that the excess temperature protection means is a rod controller (13).
8. Heating device according to one of the preceding claims, characterized in that it has a control device with an additional contact for switching a basic power or a switched-in power for the first area (17, 19) to said total, maximum, first power.
9. Heating device according to claim 7 or 8, characterized by an electronic control, preferably with a contact switch arrangement for inputting into the control and has a further relay for switching the switched-in power to said maximum, total, first power, in addition to the basic power.
10. Heating device according to one of the preceding claims, characterized in that the heating device is a radiant heater (11) with a heating conductor made from a resistance material, preferably in flat strip form.
11. Method for operating a heating device (11), particularly for a cooking point with a glass ceramic cooking area, which is subdivided into at least one first area (17, 19) and a second area (21), a first excess temperature protection means (13) engaging over all areas (17, 19, 21) for influencing and determining the temperature of the areas (17, 19, 21), a first area (17, 19) having a maximum first power and by connection to a power supply via the excess temperature protection means (13) is monitored by the latter and is switched off by said excess temperature protection means (13) in the case of an excess temperature, a second area (21) having a maximum surface heating power of approximately 2.5 W/cm², characterized in that the second area (21) is connected to a power supply without interconnection of the excess temperature protection means (13) and is operated without monitoring by said excess temperature protection means (13).
12. Method according to claim 11, characterized in that the second area (21) is operated entirely without monitoring by an excess temperature protection means.
13. Method according to claim 11 or 12, characterized in that with respect to the first area (17, 19) a power is switched in in addition to the basic power of the first area and a maximum, first power is applied when in the switched-in power state.

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