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Heating device and electric appliance with heating device

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Heating device and electric appliance with heating device


A heating device for heating a liquid in the through-flow comprises a carrier with heating conductors thereon and at least two surface mounted device (SMD) temperature sensors. A first temperature sensor is arranged closed to the heating conductor at a distance of less than twice the heating conductor width. A second temperature sensor has a greater distance to the heating conductor than the first temperature sensor, preferably more than twice the distance of the first temperature sensor to the heating conductor.

Browse recent E.g.o. Elektro-geraetebau Gmbh patents - Oberderdingen, DE
USPTO Applicaton #: #20140029928 - Class: 392479 (USPTO) -
Electric Resistance Heating Devices > Specific Application: >Continuous Flow Type Fluid Heater >Externally Heated Line Connected Section

Inventors: Holger Koebrich, Roland Muehlnikel

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The Patent Description & Claims data below is from USPTO Patent Application 20140029928, Heating device and electric appliance with heating device.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Application No. 10 2012 213 385.2, filed Jul. 30, 2012, the contents of which are hereby incorporated herein in its entirety by reference.

TECHNOLOGICAL FIELD

The invention relates to a heating device for heating a medium, in particular a liquid, as well as to an electric appliance having a flow channel for a medium or a liquid, respectively.

BACKGROUND

A corresponding heating device is known from EP 1152639 A2 which can be configured either as a flat carrier plate or as a flow heater. There, the temperature sensors are attached to the carrier in flat conductor technology or thick film technology, respectively. Since the heating conductors are attached to the carrier as well in thick film technology, but of a different material, two coating steps are required.

BRIEF

SUMMARY

The object underlying the invention is to provide an aforementioned heating device as well as an electric appliance provided therewith, by means of which problems of the prior art can be prevented and by means of which in particular a simple and reliable structure of a heating device for a secure and reliable operation can be achieved.

The object is achieved by a heating device as well as by an electric appliance. Advantageous as well as preferred embodiments of the invention are included in the further claims and will be explained in more detailed in the following. Here, some of the features are only described for the heating device or only for the electric appliance. However, regardless thereof, they shall be applicable to both the heating device and the electric appliance. The wording of the claims is incorporated into the content of the description by explicit reference.

It is provided that the heating device heats the medium or the liquid, respectively, either through-flow or past-flow or, in the type of a cooking plate, it may also be a heating for a stagnant medium, for example in a cooking vessel. The heating device comprises a carrier, wherein heating conductors are attached to the carrier and at least a first and a second temperature sensor are arranged on the carrier. The carrier may be configured as generally known, for example be made of an insulating material such as ceramics or the like, as an alternative be made of metal or steel, respectively, with an insulating layer thereon.

According to the invention, a first temperature sensor is arranged close to the heating conductor, whereby predominantly the heating conductor temperature is to be monitored most directly. Here, a distance may be smaller than twice the heating conductor width, advantageously even smaller than one full heating conductor width, or approximately half a heating conductor width. Another measure for the distance of the first temperature sensor to the heating conductor may advantageously refer to the thickness of the carrier instead of to the heating conductor width, i.e. to the path that the heat flow has into the medium starting from the heating conductor on the one hand and on the other hand to the first temperature sensor as a heat transverse conduction in the carrier. Here, the distance of the first temperature sensor to the heating conductor may preferably be smaller than the ten-fold of the thickness of the carrier, advantageously smaller than the five-fold or even only approximately the three-fold of the thickness of the carrier. Naturally, a sufficient electric insulation distance is to be complied with.

According to the invention, the second temperature sensor has a greater distance to the heating conductor than the first temperature sensor, wherein the two temperature sensors do not necessarily have to be arranged close to one another or it does not necessarily have to be the same location of the heating conductor in the vicinity of which the temperature sensors are arranged, respectively. Advantageously, the distance of the second temperature sensor to the heating conductor is more than twice the heating conductor width or even more than the threefold of the heating conductor width, for example the threefold to fivefold. As an alternative, the distance may be such that it is greater than twice the distance of the first temperature sensor to the heating conductor, advantageously approximately the threefold to fivefold.

Similar to the indications made regarding the first temperature sensor, the thickness of the carrier may be consulted as another measure for the distance of the second temperature sensor to the heating conductor, so that a distance to the heating conductor may be greater than the fifteen-fold of the thickness of the carrier. Particularly advantageous, the distance is greater than the thirty-fold of the thickness of the carrier or it is approximately the thirty-fold to fifty-fold of the thickness of the carrier, respectively.

As a result of the different distances of the two temperature sensors to the heating conductor, predominantly the heating conductor temperature may be detected by the first temperature sensor, which is arranged close to the heating conductor. That way, in particular an undesired high temperature may be detected and corresponding counter measures may be initiated, for example a switching-off of the heating device or a reducing of the electric performance. Naturally, due to the small distance, the temperature at the first temperature sensor is influenced essentially by the heating conductor and to a lesser extent by the environment or by the medium to be heated due to the aforementioned short paths for the heat flow.

In turn, the second temperature sensor is located at a greater distance to the heating conductor so that its temperature is determined essentially by the medium to be heated. The aforementioned distances between the second temperature sensor and the heating conductor are generally considered to be sufficient, in particular if the medium is a liquid, so that the heating conductor temperature does not have a direct influence on the temperature measured at the second temperature sensor. First of all, that becomes clear from the indication of the distances regarding the thickness of the carrier.

Advantageously, exactly the two aforementioned temperature sensors are provided on the heating device no further ones. As an alternative, yet another temperature sensor could be provided such that the second temperature sensor and the additional temperature sensor are most distant to one another in the through-flow direction of the medium. Thereby, a heating of the medium flowing through or a heat flow introduced by the heating device, respectively, can be determined.

The temperature sensors may be positive temperature coefficient (PTC) resistors. In an advantageous embodiment of the invention, the temperature sensors are configured as negative temperature coefficient (NTC) resistors, in particular having a most linear characteristic line in a range between 0° C. and 200° C. or 300° C.

In yet another advantageous embodiment of the invention, the first temperature sensor and the second temperature sensor or all temperature sensors, respectively, are identically constructed.

It is preferred if at least one of the temperature sensors is configured as a surface mounted device (SMD) component, advantageously both sensors. As a result of the small construction type, little space is required on the carrier. As a result of their low heat capacity, a very good and rapid temperature detection may be achieved. They may also easily be attached to the carrier by means of SMD technology and they abut the carrier through the soldering connection and the typical SDM construction type for a most good temperature transfer. Here, a temperature transfer can be improved by means of a heat-conductive paste or the like.

In another embodiment of the invention, it can be provided that one or the temperature sensor(s) is/are attached to the carrier not in a fixed manner or not in a permanent manner, i.e. not soldered thereon as described above. They may, for example, be pressed onto the carrier or applied on the carrier by another mounting device and also be electrically contacted by means of the mounting device. That way, a step of soldering the temperature sensors to the carrier may be omitted.

In another embodiment of the invention, the first temperature sensor may be configured to be elongate and extend essentially parallel to a longitudinal course of that heat conductor that it has the shortest distance to. The arrangement of the temperature sensor is advantageous in that now the heat flow coming from the heating conductor encounters the temperature sensor in a transverse manner, so to say, and the sensor is heated over its length most uniformly. That improves the measuring accuracy as well as the response rate of the first temperature sensor. The first temperature sensor per se may face to any region of the heating conductor or be located very close thereto, respectively. Advantageously, it is a region of a loop of the heating conductor.

The heating conductor may advantageously extend meander-shaped or in loops, respectively, on the carrier. The curvatures of the loops can be configured such that the heating conductor extends around the carrier approximately with its width. Advantageously and for prevention of so-called hot spots as a result of current crowding, the two heating conductor arms of the loop may terminate and their ends may be connected or contacted, respectively, by means of an electrically very well conducting contact bridge. That is known from the prior art, see EP 1905271 B1.

Advantageously, the second temperature sensor is arranged in the region of such an aforementioned curvature or loop, respectively, that means that the heating conductor gets closest to the second temperature sensor with such a curvature or loop, respectively. That is advantageous in that here the generated heating power is slightly lower and thus the second temperature sensor is even slightly less exposed to the direct temperature influence of the heating conductor.

The heating conductor is advantageously formed of a resistance material in thick film technology. A thickness may be at least 5 μm, advantageously at least 20 μm up to more than 50 μm. The width of a heating conductor is advantageously approximately constant over its longitudinal course and may be between 2 mm and 10 mm, advantageously approximately 5 mm to 7 mm. In the case of a parallel connection of the heating conductors, the width may even be smaller.

Advantageously, the electric appliance according to the invention comprises a flow channel for a medium or a liquid, respectively, in particular water. Particularly advantageous, such an electric appliance is a washing machine, a dishwasher or in general a flow heater. A heating device according to the invention is located on the flow channel or it forms the flow channel at least partially, respectively. In one embodiment of the invention, it is possible that the heating device is configured tubular with a tubular carrier. However, it may also be a partial tube. Then, the medium flows through the heating device. In that case, heating conductors and temperature sensors are arranged on the outer face of the heating device or of the carrier, so that they do not get into contact with the medium or the liquid, respectively, and are also easier accessible for an electric contacting. Advantageously, it is possible that the second temperature sensor is arranged behind the first temperature sensor in flow direction of the medium.

In another embodiment of the invention, an electric appliance according to the invention may comprise a heating device according to the invention having a flat or plate-shaped carrier, respectively, for example as a cooking device or cooktop for placing a pot or another vessel.

If a heating device is configured tubular, it is advantageously installed in an electric appliance such that at least one of the temperature sensors is arranged in a vertically topmost region of the heating device. Particularly advantageous that is the first temperature sensor close to the heating conductor. If there is a medium or a liquid, respectively, in the flow channel, with air bubbles or air inclusions therein in turn, they are usually located in the topmost region, if their location can be specified at all. Since in that case the heat transfer from the heating device to the medium is not good due to the air bubbles, there is a risk of a local overheating of the heating device or of the heating conductor, which can then be very well and very rapidly be detected by the temperature sensor arranged there.

The second temperature sensor for detecting the temperature of the medium or of the liquid per se, respectively, can on the one hand also be arranged in a vertically upper region or in the vertically topmost region. As an alternative, the second temperature sensor may be provided far below, in particular because the sensor aims at measuring the temperature of the medium, regardless of such air inclusions or even with such inclusions, respectively.



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stats Patent Info
Application #
US 20140029928 A1
Publish Date
01/30/2014
Document #
13951025
File Date
07/25/2013
USPTO Class
392479
Other USPTO Classes
International Class
24H1/00
Drawings
4



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