EP2649860B1 - Heating device for a household appliance and household appliance comprising such a heating device - Google Patents

Description

The invention relates to a heating device for a household appliance, wherein the heating device has a substrate to be heated with a use side and a rear side facing away from the use side, at least one surface heating, which is arranged on the back of the substrate, and at least one temperature sensor. The invention also relates to a household appliance with at least one such heating device.

There are known heaters for household appliances in the manner of the preamble, in which the at least one temperature sensor is attached to the surface heating. The at least one temperature sensor is typically used for temperature control of one of the use side directly or spaced facing medium (food, liquor, process air, etc.). However, since a temperature at the heater may differ considerably from a temperature at the usage side, characteristic curves are often used to determine a temperature at the use side, which information about an experimentally determined difference between the temperature at the heater of the temperature the usage side depending on one or more variables (eg the temperature at the heater).

DE 20 32 151 A1 discloses an electric heater with a flat support body made of inorganic material, such as glass ceramic, fused silica, porcelain, the upper side has at least one heating surface for receiving the material to be heated, wherein the support body is formed as a profiled press or cast body. The support body may have a bedding for receiving a temperature sensor or regulator.

GB 2 103 910 A discloses a glass ceramic hotplate in which at least one radiant heater is disposed beneath a glass ceramic cooking surface and wherein the or each radiant heater comprises a continuous base layer of electrically and thermally insulating material, a peripheral wall also of electrically and thermally insulating material, and a heating element disposed on the base layer having. The radiant heater also includes means, for example a backing, on the base layer for insulating a region in the peripheral wall from the heat emitted by the heating element and a temperature sensor such as a thermocouple or a platinum resistor within the isolated region to substantially only in operation the temperature of a cooking vessel, which is heated by the heater, to react sensitively. The temperature sensor is effective because a cold area is created on the glass ceramic plate, by which the temperature of the cooking vessel can be determined.

FR 2 283 618 A1 discloses a heater having a low temperature gradient, the device having an electrical resistance protected by an electrically insulating material, the heating resistor having a thin heating conductor sandwiched between two sheets of electrically insulating material.

It is the object of the present invention to provide a simpler to implement, robust and accurate measuring heater for household appliances.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a heating device for a domestic appliance, comprising a substrate to be heated with a use side and a rear side facing away from the use side, at least one surface heating, which is arranged on the back of the substrate, and at least one temperature sensor, wherein the at least one temperature sensor an associated recess in the surface heating is performed and fixed to the substrate.

The use side may in particular represent that side or surface of the substrate which is intended to be exposed to a medium to be treated (feed, liquor, process air, etc.). The rear side can be shielded in particular by the substrate against the medium to be treated.

This heating device has the advantage that a direct influencing of the temperature sensed by the at least one temperature sensor is reduced on account of the surface heating, that is to say a temperature measurement which is relatively independent of the temperature of the heating is made possible. Rather, the temperature at its side of use more accurate and reliable reproducing substrate is sensed. Also, the at least one temperature sensor can now respond more quickly to temperature changes on the use side of the substrate, allowing for improved temperature control.

Furthermore, since the substrate is not broken through the recess, the at least one temperature sensor remains protected from the medium to be treated, which allows a further long service life. Also, the at least one temperature sensor remains hidden when looking at the use side, and the use side is easier to clean. The recessed construction also allows a flatter construction. The long service life is further extended by the fact that a temperature at the substrate due to a heat spread and due to a smoothing of temperature fluctuations of the heater (which may occur, for example, in a pulse-like operation of the heater) lower maximum values and temperature fluctuations than in a direct on the heater attached temperature sensor.

The substrate may comprise, for example, metal, including enameled metal, glass or glass-ceramic.

According to the invention, the at least one temperature sensor is mounted in a rear recess or depression of the substrate. This further reduces an influence of the heating on a temperature measurement. Also, the at least one temperature sensor is brought even closer to the use side, which further improves, for example, a measurement accuracy and a response time with respect to a temperature change on the use side.

It is, for example, a preferred embodiment for better heat distribution and / or for increased stability that the substrate has a plurality of layers or layers and the rear depression is formed by at least one recess in at least one of the layers. In this case, at least in that layer which forms the use side of the substrate ("uppermost layer"), no such recess is provided in order to avoid a breakthrough. It is a development that all layers except for the uppermost layer have a recess for generating the respective depression in order to bring the at least one temperature sensor as close as possible to the use side.

The layers may in particular be metal layers, wherein at least one of the layers may in particular comprise stainless steel or aluminum. For example, an uppermost layer forming the use side of the substrate may be made of durable stainless steel while an underlying layer forming the backside of the substrate is made of highly thermally conductive aluminum. The heater is then attached to the aluminum layer. In this case, the recess may be e.g. be formed by a recess in the aluminum layer. The at least one temperature sensor can then be attached to a rear side of the stainless steel layer.

The layers preferably have at least one independently producible and / or freestanding layer or layer.

The recesses in the layers may be introduced after applying or joining the layers, e.g. by etching, lasing, etc. Alternatively, the recesses may be introduced into the respective layers prior to joining the layers and the layers then joined together. The assembly may be used in independently producible layers e.g. done by soldering and / or whipping.

It is an alternative embodiment that the substrate is a homogeneous material and the rear recess is formed by a material removal of the substrate, for example by milling, etching, drilling or lasing. The depression is preferably brought as close as possible to the use side.

It is still an embodiment that the recess on an area of max. about 400 mm ² , in particular to a diameter of about 20 mm, is limited, so that the good heat distribution in the heating is not interrupted.

The recess is not limited in shape and may be, for example, angular, round, elliptical or equipped with a freeform contour, etc., with a circular or cylindrical recess is preferred.

Attachment of a temperature sensor may be accomplished in any suitable manner, e.g. by means of soldering, welding, clamping, press-fitting, gluing etc.

The heater may in particular be a thin-film heater or a thick-film heater.

The heater may comprise an electrically conductive heating conductor layer. The heating conductor layer may be applied directly to a substrate to be heated, in particular if the substrate is an electrically non-conductive substrate, e.g. made of glass, glass ceramic or plastic. The heating conductor layer may alternatively be applied indirectly over an electrically insulating insulating layer on a substrate to be heated, in particular if the substrate is an electrically conductive substrate, e.g. made of metal.

The heat conductor layer may in particular consist of CrNi. In this case, a thickness of the heating conductor layer between one and 300 micrometers, in particular between 25 and 50 micrometers, is preferred.

The insulating layer preferably comprises a dielectric material, preferably aluminum oxide. A thickness of the insulating layer between 150 and 500 micrometers, in particular between 250 and 300 micrometers, is preferred.

In addition, for example, a protective layer ("top coat") may have been applied to the heater, which may for example prevent moisture from penetrating into the hygroscopic insulating layer.

For electrical contacting, e.g. by means of a template, e.g. Bronze surfaces are applied, which contact the Heizleiterschicht and attached to which electrical lines, e.g. welded, can be.

It is still a development that the at least one heating track has been applied by means of a plasma process. In particular, a use of a thermal plasma spraying is advantageous.

By means of the plasma spraying, the heating conductor layer and optionally the insulating layer can be applied to the substrate. For example, a plasma torch can be used for plasma spraying. The plasma spraying has the advantage that it is easy to carry out and allows a high accuracy of the produced layers. In addition, many materials can be plasma sprayed. The substrate hardly heats up during the coating (up to a maximum of 200 ° C.), which is likewise advantageous.

The object is also achieved by a household appliance with at least one heating device as described above.

The household appliance may in particular be a cooking appliance. It is an embodiment that the household appliance is a cooking appliance in the form of a Garraumeinschubs. The cooking compartment insert can in particular be a food support, e.g. an actively heated baking sheet, food tray or cooking space divider.

In particular, in the case of a food support, the use side is typically also serving as a food storage top, his ceiling or top is directly heated by means of the rear mounted heater.

By bringing the at least one temperature sensor close to the top of the food support, in particular by means of the depression (s), the temperature measurement can be so accurate that a temperature at an underside of a resting food can also be determined. Even later additions of cold foods, liquids, etc. (for example, fish sticks or infusions) may then be detected by the at least one temperature sensor. This makes it possible to realize a fast-response temperature control. Such a temperature control can be used advantageously to prevent burning and burning (empty cooking protection). In addition, there are additional possibilities for designing cooking programs. Furthermore, a preparation of particularly sensitive foods is facilitated. Even a successful cooking for beginners can be simplified.

However, the household appliance may also be another cooking appliance, e.g. an oven (oven, microwave oven etc.) or a hob. The substrate of the hob can e.g. be a glass ceramic plate. The medium to be heated can then be in particular a cookware (pot, pan, etc.).

However, the household appliance may also include, for example, a washing machine (e.g., with the heating device for heating liquor), a tumble dryer (e.g., with the heating device for heating process air), or a dishwasher (e.g., with the heating device for heating rinse water).

In the following figure, the invention will be described schematically with reference to an embodiment schematically.

The figure shows a heating device 1 for a domestic appliance H, e.g. a heated food support. The heating device 1 has a substrate 2 to be heated with a use side 3 and a rear side 4 facing away from the use side 3. On the back 4 of the substrate 2, a surface heating 5 is mounted flat. The heating device 1 further has two temperature sensors 6, which are performed by a respectively associated recess 7 in the surface heating 5 and fixed to the substrate 2.

More specifically, the substrate 2 comprises a plurality of sheets or layers 2a, 2b, of which a first or uppermost substrate layer 2a of stainless steel defines the use side 3. A second substrate layer 2 b consists of highly conductive aluminum and supports the surface heating 5.

The surface heating 5, in turn, has an electrically insulating insulating layer 5a made of aluminum oxide lying flat on the second substrate layer 2b, on which facing away from the second substrate layer 2b, a heat conductor layer 5b is applied flat. The Heizleiterschicht 5b can be energized to generate heat. The recess 7 is achieved by corresponding congruent recesses in the insulating layer 5a and the heating conductor layer 5b.

For an improved thermal shielding of the surface heating 5 and for a particularly close approach of the temperature sensors 6 to the use side 3, the substrate 2 has two rear recesses 8. The recesses 8 are formed by a respective recess in the second substrate layer 2b, so that the temperature sensors 6 are inserted into a respective recess 7 and congruent recess 8 and fixed to the back of the uppermost substrate layer 2a. The temperature sensors 6 may be attached to the uppermost substrate layer 2a directly or via a thermal interface material (TIM), such as a thermal interface material. The recess 7 and the recess 8 are each configured in a circular plan view with a diameter of not more than about 20 mm. The temperature sensors 6 are connected via corresponding electrical lines 9 to an evaluation unit, in particular a control unit. The control unit may, in the case of a food support as the household appliance H, for. be a control unit of the Gargutträger receiving cooking appliance.

Of course, the present invention is not limited to the embodiments shown.

LIST OF REFERENCE NUMBERS

1

heater

2

substratum

2a

first substrate layer

2 B

second substrate layer

3

use page

4

back

5

panel heating

5a

insulation layer

5b

heat conductor

6

temperature sensor

7

recess

8th

deepening

9

electrical line

H

household appliance

Claims (8)

1. Heating device (1) for a domestic appliance (H), having

   - a substrate (2) to be heated with a usage side (3) and a rear side (4) facing away from the usage side (3),

   - at least one surface heater (5), which is arranged on the rear side (4) of the substrate (2), and

   - at least one temperature sensor (6),

   characterised in that
   the at least one temperature sensor (6) is guided through an associated recess (7) in the surface heater (5) and fastened in a rear depression (8) of the substrate (2).
2. Heating device (1) according to claim 1, characterised in that the substrate (2) has a plurality of layers (2a; 2b) and the rear depression (8) is formed by a recess (7) in at least one of the layers (2b), wherein there is no such recess (7) at least in that layer (2a) which forms the usage side (3) of the substrate (2).
3. Heating device according to claim 2, characterised in that that layer (2a) which forms the usage side (3) of the substrate (2) consists of stainless steel and an underlying layer (2b) which forms the rear side (4) of the substrate (2) consists of aluminium.
4. Heating device according to claim 2, characterised in that the substrate is a homogenous material and the rear depression is formed by a removal of material from the substrate.
5. Heating device (1) according to one of the preceding claims, characterised in that the recess (7) is limited to an area of approx. 400 mm², in particular to a diameter of approx. 20 mm.
6. Domestic appliance (H) with at least one heating device (1), characterised in that the heating device (1) is a heating device (1) according to one of the preceding claims.
7. Domestic appliance (H) according to claim 6, characterised in that the domestic appliance (H) is a cooking appliance.
8. Domestic appliance (H) according to claim 6, characterised in that the domestic appliance (H) is a cooking chamber insert.

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