Heating apparatus for a household appliance for the care of laundry items and method for operating such a heating apparatus

Abstract

A household appliance for the care of laundry items, which heating apparatus is embodied for generating heat by combusting gaseous media and has a device for supplying the gaseous medium to a burner, wherein a means is provided which is thermally coupled to the burner and the device and is embodied for changing a temperature of the device in order to control the flow of the medium through the device, in particular the metering unit of the device. The invention also relates to a method for operating a heating apparatus for a household appliance for the care of laundry items, in particular a gas laundry dryer.

Description

BACKGROUND OF THE INVENTION

[0001] The invention relates to a heating apparatus for a household appliance for the care of laundry items, which heating apparatus is embodied for generating heat by combusting gaseous media, and to a device for supplying the gaseous medium to a burner. The invention also relates to a method for operating such a heating apparatus for a household appliance for the care of laundry items.

[0002] A gas laundry dryer is known which is embodied with a heating apparatus that is designed to provide heating power at one level only, which means that controlling the generation of heat is possible only by switching the heating apparatus on and off. In this case, when the apparatus is in the switched-on state, essentially the full heating power available is delivered at all times. By way of bimetal temperature switches or NTC resistors ("NTC" stands for "Negative Temperature Coefficient") it is then possible to control the switching-on and switching-off of the gas burner by, if necessary, cyclically repeated opening and closing of the gas valve. Adjusting the heating power of the gas burner and thereby reducing the loading on the gas burner, in particular in critical exhaust air and air resistance situations, such as in the case of a clogged lint filter for example, is not possible.

[0003] According to conventional practice, controlling the heating power is only possible by way of a multi-stage gas valve or by way of a gas control valve operating continuously or on a multi-stage basis. However, valves of this kind are much too expensive for use in laundry dryers in the low-price segment and consequently are not used in such applications.

BRIEF SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide a heating apparatus for a household appliance for the care of laundry items as well as a method for operating such a heating apparatus, wherein controlling the heating power can be effected on a multi-stage basis and therefore is possible with greater flexibility also in the case of household appliances without a complex gas control valve.

[0005] An inventive heating apparatus for a household appliance for the care of laundry items is embodied for generating heat by combusting gaseous media. The heating apparatus includes a device for supplying the gaseous medium to a burner of the heating apparatus. In addition, the heating apparatus includes at least one means which is thermally coupled to the burner and the device and is embodied for changing a temperature of the device in order to control the flow of the gaseous medium through the device.

[0006] By means of this embodiment of the heating apparatus it can be ensured that flexible and hence also multi-stage control of the heating power can be realized even without a relatively complex gas control valve. Owing to the means and its thermal coupling to the burner and the device, the volumetric flow rate of the medium through the device can therefore be set as a function of temperature. The invention therefore relates to a self-regulating burner system of a heating apparatus, in particular a gas burner system, which can adjust to different resistance situations in the household appliance and reduce or increase the heating power. In this case the invention turns to account specific behavioral characteristics of a flame of the gaseous medium (in particular of a gas flame, at different volumetric air flow rates across the burner). Given a high volumetric flow rate over the burner, the gas burner flame is in this case short and small in diameter. If the volumetric flow rate across the burner is reduced, due, for example, to clogging of the lint filter or other air-reducing influences, a long exhaust air pipe for example, the flame opens out similar to a tulip and in addition the flame becomes longer. A further aspect in this connection is given by the fact that the burner output of a burner, in particular a gas burner, is determined by the volumetric flow rate of the gaseous medium, in particular of the combustion gas, or of the molecular weight of the gaseous medium. If, for example, the temperature of the gaseous medium increases upstream of a metering unit for metering the gaseous medium, in particular a pressure control valve, then although the same volume continues to be supplied to the burner by way of the metering unit, the molecular mass contained in the volume is smaller at higher temperature due to the expansion of the gas, as a result of which the burner loading decreases and the heating power can be reduced.

[0007] Precisely these cited properties are exploited in an advantageous manner by the inventive heating apparatus, in that owing, as it were, to the thermal coupling of the means to the burner and the device the flow control can be precisely ensured as a function of the temperature applied to the device and as a result the heating power can be varied very flexibly and on a multi-stage basis, in particular continuously.

[0008] Preferably the means of the heating apparatus is embodied in such a way that if the temperature of the device increases due to the means, the flow of the gaseous medium through the device is reduced.

[0009] The means is preferably embodied for sensing the temperature in the region of the flame of the burner. It is thus possible to establish the temperature effectively in the region of the burner flame, thereby also enabling inferences to be made about the shape and widening-out of the burner flame, and consequently also enabling an undesirable flame profile to be detected. As a function thereof, the flow of the gaseous medium through the device can then be varied automatically owing to the thermal coupling of the device.

[0010] A self-regulation of this kind is embodied to be highly precise and flexible, and allows a very finely metered setting or control and consequently also a very finely adjustable change in heating power.

[0011] Preferably the means is embodied for changing the temperature of the gaseous medium. What is thus achieved by the means is effectively also a direct thermal feedback to the gaseous medium conducted in the device, as a result of which the aforementioned behavioral characteristics can be exploited particularly effectively in order to enable the heating power control of the heating apparatus to be set.

[0012] Preferably the device comprises a metering unit, in particular a nozzle, for metering the gaseous medium. The metering unit can also be a pressure control valve. In particular the means is embodied for changing the flow cross-section of the metering unit by applying a temperature to the metering unit. In this way it is possible to enable a direct influence to be exerted on the flow cross-section of the metering unit, as a result of which the precise setting and also quick changing of the cross-section and therefore a fast regulation of the heating power can be accomplished in this case too.

[0013] Preferably the means comprises a heating unit which is thermally coupled to the device and can be controlled electrically as a function of the temperature in the region of the burner. The central component in this embodiment is therefore an electric heating unit which can actively heat the device, in particular a supply line for the gaseous medium to the burner, in the appliance. The heating unit is preferably monitored by means of a temperature monitoring device, in particular a temperature controller, which monitors the burner heater, in particular the gas burner heater, and switches the heater on or off. The air resistance state in the household appliance can be detected as a function of the temperature gradient at the control element. If the air resistance is high, the heating unit is switched on, the gaseous medium expands, and the burner loading decreases. When the air resistance is normal, the heating unit remains switched off.

[0014] It can also be provided that the heating apparatus includes a heat exchanger as means. The thermal coupling to the burner and the device can also be provided by the heat exchanger to the extent that a change in temperature of the device can be effected in order to control the flow of the medium through the device by means of the heat exchanger.

[0015] In a preferred embodiment the means is at least a heating and cooling element, in particular a Peltier element, which can be controlled as a function of the temperature in the region of the burner for the purpose of heating or cooling the device, in particular the metering unit, and is thermally coupled to the device. In this embodiment a central component is given by the heating and cooling element which is coupled to the device, in particular a supply line for supplying the gaseous medium to the burner. A heating and cooling element of the kind is disposed in such a way that it can actively heat the device, in particular the supply line, but can also actively cool it by polarity reversal. A system of the kind, in particular a Peltier system, is controlled by way of a temperature controller which monitors the burner heater, in particular the gas burner heater. The air resistance state in the appliance can be detected as a function of the temperature gradient at the control element. If the air resistance is high, the heating and cooling element is switched to "heating", the gaseous medium expands in the device upstream of the burner, and the burner output decreases. If the air resistance is normal, the system, in particular a Peltier system, is switched off.

[0016] Since the burner output in such a household appliance for the care of laundry items, in particular a laundry dryer, basically decreases (approx. 5 to 10% loss in power) with the process time due to the heating-up of the gas-conducting components, which include, for example, the valve, a nozzle and piping, this behavior can be compensated for by active cooling on the side of the Peltier system. It is even possible to increase the heating power above the nominal value of the burner loading, which leads to a shortening of the drying time.

[0017] In a further advantageous embodiment, a central component is the metering unit of the heating apparatus, in particular a gas burner nozzle, which is thermally coupled from at least two sides to heating and cooling elements of the kind. The metering unit can thus be either cooled or heated by polarity reversal. This system, too, can be controlled by way of a temperature controller which monitors the gas burner heater. The air resistance state in the appliance can be detected as a function of the temperature gradients at the control element. In this case, too, in the event of a high air resistance the Peltier system can be switched to "cooling", with the result that the diameter and consequently the flow cross-section of the metering unit, in particular of the nozzle, is reduced in size, and the volumetric flow rate lowered, thereby reducing the burner output. If the air resistance is normal, the Peltier system is simply switched off.

[0018] Since the burner output in a household appliance for the care of laundry items, in particular a laundry dryer, basically decreases, as has also already been cited above, with the process time due to the heating-up of the gas-conducting components, as have likewise already been cited above, this behavior can be compensated for by active heating of the metering unit, whereby this leads to a greater diameter and hence a larger flow cross-section of the metering unit and as a result a higher volumetric flow rate of the gaseous medium through the metering unit is ensured. It is even possible to increase the heating output therewith above the nominal value of the burner loading, thereby leading to a shortening of the drying time.

[0019] The means can have at least one heating element, in particular a Peltier element, which can be controlled as a function of the temperature in the region of the burner for heating the device, in particular a supply line for supplying the gaseous medium to the burner, and is thermally coupled to same. In this embodiment, therefore, in addition to or instead of the aforementioned approach, it is not, or not only, the metering unit that can accordingly be subjected to a temperature, but a further component of the device, in particular the supply line, can be accordingly thermally coupled. The means preferably includes a pipe which is thermally coupled to the device for supplying the gaseous medium to the burner and to the burner, and in which a medium is disposed which is embodied for applying a temperature to the device, in particular the gaseous medium transported therein, by way of the pipe wall as a function of a separate application of temperature by the burner, in particular the burner flame. In this embodiment a central component is to be seen in the fact that the pipe is provided which in particular is at least partially filled with a gaseous medium. The pipe is preferably embodied around a supply line assigned to the device for the purpose of supplying the gaseous medium to the burner and additionally extends in the region of the burner flame. In particular the pipe is wrapped around the supply line. Furthermore it is preferably provided that the pipe is disposed on the inside of a duct arranged around the burner head. The pipe is preferably embodied from a material that conducts heat well, for example copper. The medium present in the pipe can be a fluid which is a good conductor of heat.

[0020] During normal operation of the household appliance the burner flame is relatively tightly concentrated and the heat-conducting medium disposed in the pipe assumes the temperature of the wall of the heating duct at the burner head. The temperature is typically below 40.degree. C.

[0021] If increased air resistance conditions now arise in the household appliance, the gas flame opens out and the temperature of the heat-conducting medium disposed in the pipe increases significantly. The medium then conducts the heat as far as the supply line of the device, to which it is thermally coupled, and thereby heats the gaseous medium that has flowed through in the supply line. The gaseous medium in the supply line then expands and the burner output decreases in accordance with the principles explained above. In that way also the heating power of the heating apparatus can be realized in a precise and continuous self-regulating manner.

[0022] A further aspect of the invention relates to a household appliance for the care of laundry items, in particular a gas laundry dryer, which has a heating apparatus according to the invention or an advantageous embodiment thereof.

[0023] In the case of an inventive method for operating a heating apparatus for a household appliance for the care of laundry items, a gaseous medium is supplied to a burner of the heating apparatus by way of a device for supplying the gaseous medium. A means is thermally coupled to the burner and the device, the temperature of the device being changed by the means in accordance with specific operating phases and the flow of the medium through the device being varied in accordance with specific operating phases as a function of the change in temperature. In that way, too, the heating power can be controlled very precisely and on a multi-stage basis, in particular continuously, and this can be realized in particular in the case of household appliances which do not have a gas valve that is embodied for multi-stage control.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Exemplary embodiments of the invention are explained in more detail below with reference to schematic drawings, in which:

[0025] FIG. 1 shows a perspective view of an inventive heating apparatus according to one exemplary embodiment;

[0026] FIG. 2 shows a schematic sectional view of a portion of the heating apparatus according to FIG. 1; and

[0027] FIG. 3 shows a schematic sectional view of a further exemplary embodiment of a specific detail of an inventive heating apparatus.

[0028] Identical or functionally identical elements are labeled with the same reference signs throughout the figures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION

[0029] FIG. 1 shows a schematic perspective view of a heating apparatus 1 which is disposed in a gas laundry dryer. The heating apparatus 1 is embodied for generating heat by combusting a gaseous medium. The heating apparatus 1 additionally includes a device 3 for supplying the gaseous medium to a burner 2. The device 3 comprises a supply line 4 for supplying the gaseous medium to the burner 2 and in addition has a metering unit which, in the exemplary embodiment, is embodied as a nozzle 5. The nozzle 5 is preferably a simple low-cost component which is not embodied as a multi-stage gas control valve.

[0030] The nozzle 5 is disposed in the flow direction of the gaseous medium in the supply line 4 upstream of the burner 2. The heating apparatus 1 further includes a heating duct 6 which is embodied in the manner of a pipe and into which the burner 2 extends at least for a section.

[0031] The heating apparatus 1 also includes a means which is thermally coupled to the burner 2 and the device 3 and is embodied for changing a temperature of the device 3 in order to control the flow of the gaseous medium through the device 3.

[0032] In this regard FIG. 1 shows an exemplary embodiment in which the means has a pipe 7 which is mounted at least partially around the outside of the supply line 4 or is disposed surrounding the latter. In particular the pipe 7 is wrapped around the supply line 4. Furthermore, the pipe 7 also extends in the region up to the burner 2. In particular the pipe 7 is disposed in the region of the burner head 8 (FIG. 2) on an inside surface of the heating duct 6. Preferably the portion of the pipe 7, which is disposed adjacent to the burner head 8, extends around the burner head 8, and encircles the latter at least partially in an annular manner. As can be seen in this regard from the view according to FIG. 2, the portion of the pipe 7 is positioned adjacent to the burner flame 9 or 10. The thermal coupling to the burner 2 or burner head 8 and in particular to the burner flame 9 or 10 is established particularly effectively thereby.

[0033] The means forming the pipe 7 is therefore thermally coupled to the device 3 and the burner 2 and is embodied in such a way that a medium which conducts heat well, in particular a heat-conducting fluid, is disposed in the pipe 7. The heat-conducting medium is embodied for the purpose of applying a temperature to the device 3, in particular the gaseous medium transported in the supply line 4. The temperature is applied via the walls of the pipe 7 and the supply line 4, the application of temperature being dependent on a separate application of temperature to the heat-conducting medium disposed in the pipe 7 by means of the burner 2, in particular the burner flame 9, 10.

[0034] The pipe 7 is embodied as a tubular pipe and formed from a material containing copper. A different heat-conducting material may also be provided as the pipe material.

[0035] The embodiment according to FIG. 1 of the heating apparatus 1 turns to account behavioral characteristics of the gas flames or burner flames 9 or 10 for different volumetric air flows over the burner 2. In this connection, if the volumetric flow over the burner 2 is high, the gas burner flame 9 or 10 is short and small in diameter. If the volumetric flow over the burner 2 is reduced due to clogging of the lint filter (not shown) of the gas laundry dryer or to other air-reducing factors such as, for example, a long exhaust air pipe, etc., the burner flame 9 or 10 opens out like a tulip and the flame additionally becomes longer. A further behavioral characteristic is characterized in that the burner output of the gas burner 3 is determined by the volumetric rate of flow of the combustion gas or the molecular weight of the combustion gas. If, for example, the temperature of the combustion gas increases upstream of the pressure control valve or the nozzle 5, then although the same volume continues to be supplied to the gas burner 2 by way of the pressure controller, the molecular mass contained in the volume is smaller at higher temperature due to the expansion of the gas, and the burner loading decreases. By combining these two behavioral characteristics it is possible to realize a self-regulating system according to FIG. 1. In the system, during normal operation of the gas laundry dryer the burner flame is tightly concentrated and the fluid in the pipe 7 takes on the temperature of the walls of the heating duct 6 at the burner head 8. This temperature is generally less than 40.degree. C. If increased air resistances now occur in the gas laundry dryer, the gas flame 9 opens outward, with the result that the gas flame 10 is produced and the temperature of the fluid in the pipe 7 increases significantly. The fluid in the pipe 7 conducts the heat as far as the gas supply pipe or, as the case may be, to the supply line 4 and thereby heats the gaseous medium flowing through in the supply line 4 upstream of the nozzle 5. The gaseous medium in the supply line 4 expands and the burner output decreases on account of the above-explained behavioral characteristics.

[0036] It can also be provided that in addition to or instead of the embodiments explained with reference to FIG. 1 and FIG. 2 with the pipe 7 as a central component, the means has an electric heater which can actively heat the supply line 4. The electric heating unit is preferably switched on or switched off by way of a temperature controller which monitors the gas burner heater. The air resistance state in the appliance can be detected as a function of the temperature gradient at the control element. If the air resistance is high, the electric heating unit is switched on, the gaseous medium in the supply line 4 expands, and the burner output decreases. If the air resistance is normal, the electric heating unit remains switched off.

[0037] In a further embodiment which is not shown explicitly, it can be provided that the means for changing a temperature of the device in order to control the flow of the medium through the device 3 has at least one Peltier element which is disposed in such a way that it can actively heat the supply line 4 or, by polarity reversal, also actively cool same. The Peltier system is controlled by way of a temperature controller which monitors the gas burner heater. The air resistance state in the appliance can be detected as a function of the temperature gradient at the control element. If the air resistance is high, the Peltier system is switched to "heating", the gaseous medium transported in the supply line 4 expands, and the burner output decreases. If the air resistance is normal, the Peltier system is switched off.

[0038] Since the burner output in gas laundry dryers basically decreases (approx. 5 to 10% loss in power) with the process time due to the heating-up of the gas-conducting components (valve, nozzle, pipework, etc.), this behavior can be compensated for by active cooling of the Peltier system, or it is even possible to increase the heating power thereby above the nominal value of the burner loading, which leads to a shortening of the drying time.

[0039] FIG. 3 shows a schematic sectional view of a detail of a further exemplary embodiment of the heating apparatus 1. In this embodiment the means includes at least two heating and cooling elements, in particular two Peltier elements 11 and 12, which are disposed adjacent to the metering unit. In this embodiment the metering unit is designed as a nozzle 5, though in the other already explained embodiments it can also be embodied as a pressure control valve.

[0040] The nozzle 5 is fitted with the Peltier elements 11 and 12 on two sides, such that they can either cool or heat the nozzle 5, which can be effected by polarity reversal. The Peltier system can be controlled by way of a temperature controller which monitors the gas burner heater. Here, too, the air resistance state in the appliance can be detected as a function of the temperature gradient at the control element. If the air resistance is high, the Peltier system is switched to cooling, with the result that the diameter of the nozzle 5 and hence the flow cross-section of the nozzle 5 is automatically reduced, and the volumetric rate of flow across the nozzle 5 is lowered, which also leads to a decrease in the burner output. If the air resistance is normal high, the Peltier system is simply switched off.

[0041] Since the burner output in laundry dryers basically drops by a certain percentage, as already explained above, with the process time due to the heating-up of gas-conducting components, as likewise already cited above, this behavior can be compensated for by active heating of the nozzle 5, which results in the nozzle 5 having a greater diameter and consequently leads to a higher gas volume flow; alternatively, it is even possible to increase the heating power thereby above the nominal value of the burner loading, which leads to a shortening of the drying time.

Claims

1. A heating apparatus for a household appliance for the care of laundry items for generating heat by combusting gaseous media, the apparatus comprising: a device for supplying the gaseous medium to a burner; and a means, thermally coupled to the burner and the device, for changing a flow of the medium through the device by changing a temperature of the device.

2. The heating apparatus of claim 1, wherein the means controls a flow through a metering unit of the device.

3. The heating apparatus of claim 1, wherein the means reduces the flow of the gaseous medium through the device if the temperature of the device is increased by the means.

4. The heating apparatus of claim 1, wherein the means senses the temperature in a region of a flame of the burner.

5. The heating apparatus of claim 1, wherein the means changes the temperature of the gaseous medium.

6. The heating apparatus of claim 1, further comprising a metering unit for metering the gaseous medium.

7. The heating apparatus of claim 6, wherein the metering unit comprises a nozzle or a valve.

8. The heating apparatus of claim 6, wherein the means varies a flow cross-section of the metering unit by applying heat to the metering unit.

9. The heating apparatus of claim 1, wherein the means comprises a heating unit which is thermally coupled to the device and can be controlled electrically as a function of a temperature in a region of the burner

10. The heating apparatus of claim 1, wherein the temperature in the region of the burner is a temperature in a region of the burner flame.

11. The heating apparatus of claim 1, wherein the means comprises a heat exchanger.

12. The heating apparatus of claim 1, wherein the means comprises a heating and cooling element is controlled as a function of a temperature in a region of the burner for the purpose of heating or cooling the device, in particular the metering unit, and is thermally coupled to the device.

13. The heating apparatus of claim 12, wherein the heating and cooling element comprises a Peltier element.

14. The heating apparatus of claim 12, wherein the heating and cooling element is controlled as a function of a temperature in a region of the burner for the purpose of heating or cooling a metering unit.

15. The heating apparatus of claim 1, wherein the means comprises a heating element, thermally coupled to the device, the heating element being controlled as a function of a temperature in a region of the burner for heating the device.

16. The heating apparatus of claim 15, wherein the heating element comprises a Peltier element.

17. The heating apparatus of claim 15, wherein the heating element is controlled as a function of a temperature in the region of the burner for heating a supply line for supplying the gaseous medium to the burner.

18. The heating apparatus of claim 1, wherein the means comprises a pipe which is thermally coupled to the device and the burner and in which a medium is disposed which applies heat to the gaseous medium transported in the device by way of the wall of the pipe as a function of a separate application of temperature by the burner.

19. The heating apparatus of claim 18, wherein the pipe applies heat to the gaseous medium as a function of a temperature by a burner flame.

20. The heating apparatus of claim 18, wherein the pipe is around a supply line and extends in a region of a burner flame.

21. The heating apparatus of claim 20, wherein the pipe is wrapped around the supply line.

22. The heating apparatus of claim 20, wherein the pipe is on an inside surface of a duct around a burner head.

23. A household appliance for the care of laundry items, comprising: a device for supplying a gaseous medium to a burner; and a means, thermally coupled to the burner and the device, for changing a flow of the medium through the device by changing a temperature of the device.

24. A method for operating a heating apparatus for a household appliance for the care of laundry items, the method comprising: supplying a gaseous medium to a burner of the heating apparatus by way of a device; and varying a flow of the gaseous medium through the device by changing a temperature of the device by a means that is thermally coupled to the burner and the device.

25. The method of claim 24, wherein the device comprises a metering unit.