Cleaning device and method for operating cleaning device taking into account fouling

Abstract

The invention relates to a cleaning device (10) comprising: a cleaning element (8); a liquid container (1); an electrically operated temperature-controlled heating device (2) for heating a liquid (100), in particular with a steam generator; and a control unit (3) for controlling the cleaning device (10). According to the invention, the control unit (3) has a device for determining the electrical power consumption (E) of the heating device and at least one reference curve (R) stored in the control unit (3). The invention also relates to a method for operating a cleaning device (10), in which the electrical power consumption (E) is compared with a reference curve (R) stored in the control unit (3) in order to determine a degree of fouling of the heating device (2), and outputting information to the plant operator as a function of the result of the comparison, i.e. The requirement for the required descaling. In this way, long-term functionality and high cleaning performance of the cleaning device can be ensured in an advantageous manner.

Description

Technical Field

[0001] The invention relates to a cleaning device comprising a liquid container, a current-operated heating device for heating the liquid, and a control unit for operation. The invention also relates to a method for operating such a cleaning device. Background Art

[0002] Various cleaning devices are known for cleaning surfaces, such as floors. A particularly effective method for cleaning hard surfaces is to use steam. For example, WO 2016 / 046554 A1 describes a steam cleaning device comprising a steam generator and a cleaning element. Steam is applied to the contact area between the cleaning element and the surface to be cleaned. To heat water in a container and generate steam, the steam generator comprises a heating device, such as a boiler.

[0003] Only when the operating temperature is reached and a sufficient amount of steam is generated can the cleaning device be used for cleaning. For this reason, it is known in the prior art to supply the heating device with current regularly and thus activate the heating device, thereby for example maintaining a temperature in the range between 150 and 220°C.

[0004] Household appliances similar to cleaning appliances such as steam cleaning appliances, which comprise a liquid container and a heating device, are, for example, irons, steam steamers or coffee machines.

[0005] Depending on the quality of the water used, particularly its hardness, scale deposits may form on the heating device of the cleaning appliance. As scale deposits increase on the boiler, heat transfer, and therefore the heating of the water, deteriorates. The scale deposits form an insulating layer on the surface of the boiler that comes into contact with the water to be heated. This can result in the water being heated less hotly or in smaller quantities. When steam is generated by the heating device, the amount of steam available may be reduced, or the water may not be fully evaporated. This can result in a reduced cleaning effect of the cleaning appliance.

[0006] Therefore, it is common to descale household and cleaning appliances regularly, for example, after a certain operating time or depending on the operating time related to the water hardness, using citric acid. The water hardness can be stored in a control unit by the appliance operator for this purpose. The cleaning appliance can then output a request for descaling to the appliance operator, for example, using a warning light or an audible warning tone. This conventional solution in the prior art fails to take into account the actual scaling of the heating device and the essential need for descaling. This can result in unnecessary descaling or descaling being performed too late to ensure the long-term, reliable functionality of the cleaning appliance.

[0007] It is therefore worthwhile to determine the actual fouling and to be able to make operational recommendations for descaling based on this. However, it is not possible to directly measure the degree of fouling with acceptable effort.

[0008] It is generally known in the prior art to equip household appliances with sensors for monitoring and controlling them. It is also possible to equip the household appliance with a temperature sensor and monitor the boiler temperature. Inferring scaling from the boiler temperature can be done. In other words, the degree of scaling can be determined indirectly through temperature measurement. This approach is employed in EP 0 947 767 A2. Alternatively, it is also possible to measure the water temperature and / or the water or steam flow rate. A solution for the latter approach is described in US Pat. No. 7,966,683 B2.

[0009] However, a disadvantage of such solutions that include additional sensors is that, in addition to the cost and integration effort for the additional sensors, they also require complex isolation of the wiring. The sensor wiring must be thermally stable in the boiler area, meaning that relatively expensive materials with high melting points must be used. Otherwise, there is a risk of short circuits if the wiring melts. Consequently, such solutions are associated with increased complexity and expense in the design of the cleaning device. Summary of the Invention

[0010] The object of the present invention is to provide a cleaning device and to specify a method for operating the cleaning device, in which the necessary descaling can be initiated depending on the degree of scaling of the heating device without making the cleaning device more complex in design, in order to at least partially eliminate the disadvantages of the prior art. This should ensure long-term functionality and high cleaning performance of the cleaning device.

[0011] Technical Solutions

[0012] This object is achieved by a cleaning device and a method for operating a cleaning device as described and claimed below.

[0013] According to the invention, it has been recognized that it is advantageous to compare the electrical energy consumption of the heating device with a previously stored profile value in the control unit.

[0014] The cleaning device is equipped with a cleaning element, a liquid container, a current-operated, temperature-controlled heating device for heating the liquid (especially with a steam generator), and a control unit for operating the heating device. The cleaning device is connected to a voltage source, such as a household outlet. Alternatively, the cleaning device may have an onboard battery. A temperature-controlled heating device is one that maintains a specific or predetermined temperature range and is switched on and off, i.e., supplied with current, so that the temperature range remains between a lower and an upper switching temperature.

[0015] If necessary, a pump for transporting the liquid can be provided in the cleaning appliance, which pump transports the liquid from the liquid container to the heating device.

[0016] According to the present invention, the control unit includes a device for determining the electrical power consumption of the heating device or a variable proportional thereto, and includes at least one reference curve stored in the control unit for the course of the electrical power consumption of the heating device or a variable proportional thereto. The reference curve can be determined during testing and stored in production before the cleaning device is sold. The reference curve represents the course of the electrical power consumption of the heating device or a variable proportional thereto over time. It has been found that the electrical power consumption of a temperature-controlled heating device or a variable proportional thereto is inversely proportional to the degree of scaling of the heating device. As scaling increases on the surface of a heating device, such as a boiler, the scaling forms an insulating layer on the heating device because the thermal conductivity of the scaling is poorer than that of the material of the heating device. For example, aluminum, which has good thermal conductivity, is often used on boiler surfaces.

[0017] Due to the increasing insulating layer and the insulating effect of the scaling, the heat transfer from the heating device to the cleaning liquid is impaired. The heating device thus retains heat for a longer time and must be activated less frequently to maintain a specific or predetermined temperature range, which means a reduction in the electrical power consumption of the heating device or a variable proportional thereto.

[0018] The degree of fouling can therefore be inferred from the electrical power consumption of the heating device or the value of a variable proportional thereto and determined by indirect measurement. Such a solution can be realized simply and cost-effectively.

[0019] In a particularly advantageous and therefore preferred cleaning appliance, the heating device is operable with a constant heating power and a temperature controller is provided for switching the heating device on and off, wherein the temperature controller has a fixed switching temperature. For example, the temperature controller may have a switching temperature below 150°C and a switching temperature above 250°C. The specific switching temperature depends on the intended use of the cleaning appliance. In steam cleaning, the switching temperature is naturally higher than in hot water cleaning.

[0020] Such a cleaning device has a particularly simple and cost-effective construction.

[0021] When using a bimetallic switch, a possible particularly simple and cost-effective design of the temperature regulator is produced. Alternatively, it is also possible to realize the temperature regulator by integrating a microcontroller in the control unit via a temperature sensor.

[0022] In a further embodiment, the cleaning device has an output unit for outputting information to the device operator. The output unit can be implemented, for example, as a display unit including one or more warning lights or as an acoustic device that generates, for example, a buzzer or a bird's chirp.

[0023] The information provided to the system operator can be a notification about reduced cleaning performance or a request to descale the cleaning system. It can also be a request to adjust the pump power. In the case of a heating device designed as a steam generator, it can also be a notification to take into account the increased residual water volume, which can be harmful to water-sensitive floors, such as wooden floors. It can also be a request to shut down the system due to an operationally critical scale content in order to prevent harm to the system operator or damage to the cleaning system.

[0024] Alternatively or in addition to the output of the information, a control circuit for carrying out automatic descaling of the cleaning appliance can also be provided in the control unit.

[0025] The cleaning device can advantageously include a controllable and, if necessary, adjustable pump for transporting the liquid. The pump can be operated with different pump powers, allowing the pump power to be adjusted variably or in stages by selecting between different fixed pump powers. A reference curve for the electrical power consumption of the heating device or a variable proportional thereto is then stored in the control unit for each of the different pump powers. For example, in the case of stepless adjustability with variable pump power using a rotary potentiometer (potentiometer), an infinite number of reference curves must be stored. For an economical design of the cleaning device, multiple reference curves can be stored, with each reference curve being assigned to a specific power range of the pump.

[0026] The cleaning device can be designed, for example, as a steam cleaning device or as a floor cleaning device for floor cleaning, and the cleaning element can be designed as a textile wiping mop.

[0027] The invention also relates to a method for operating a cleaning device as described above.

[0028] In the method for operating a cleaning device, in a first step, in a measuring mode, the electrical power consumption of the heating device or a variable proportional thereto is detected by a device for determining the electrical power consumption of the heating device or a variable proportional thereto. In a next step, the detected value is then compared with a reference curve stored in a control unit to determine the degree of fouling of the heating device. These two steps are repeated continuously or at least at certain time intervals. Depending on the result of the comparison, information is output to the device operator in an output unit, for example, optically, tactilely and / or acoustically. The output can be a one-time operation - for example, a short beep - or continuous operation - for example, a continuous display of a warning. If, after a renewed measuring mode (detection and comparison), the conditions for outputting the information are no longer met, the output of the information can be terminated.

[0029] In one embodiment of the method for operating a cleaning appliance, the reference curve can have at least one limit value, beyond which an output of the information via the output unit occurs.

[0030] Depending on the type of reference curve, passing here means exceeding or falling below. If the reference curve—as described below—depicts the activation time, then falling below the limit value generally leads to the output of a message to the system operator.

[0031] Alternatively or in addition to the output of said information, it is also possible to initiate automatic descaling of the cleaning device.

[0032] As already explained above, different limit values ​​are possible: a warning that the cleaning performance has been affected, a request for descaling or for adapting the pump power, a request for a system shutdown, wherein this information can be output with increasing scaling.

[0033] In one possible embodiment variant of the method for operating a cleaning device, the device for determining detects the activation time of the heating device within at least one switching cycle of the heating device. A switching cycle is defined as the time from "on" to "on again," i.e., from the start of current flow to the heating device until the next start of current flow. In particular, a relative activation time, i.e., the relative time portion of activation within at least one switching cycle, can also be determined. If the evaluation is performed over multiple switching cycles, fluctuations between individual switching cycles can be filtered out.

[0034] In this embodiment variant, the at least one reference curve depicts the activation time with increasing fouling of the heating device over time.

[0035] In a further embodiment of the method for operating a cleaning device, the type of surface to be cleaned is determined in a preceding method step, for example, by input by the device operator or by testing the cleaning device itself, for example, using sensor systems and / or evaluation electronics. This allows a distinction to be made between different types of surfaces to be cleaned, such as stone surfaces, wooden surfaces, textile surfaces, plastic surfaces, etc. In this case, for example, in the case of a design of the heating device as a steam generator, the reference curve has specific limit values ​​for cleaning wooden surfaces via type-specific limit values, which provide a warning before water ingress due to excessive scaling occurs.

[0036] In a further development of the method for operating a cleaning device, after the output of the information to the device operator, the device operator can confirm receipt of the information by actuating a switching element (eg, a reset button) and then terminate the information output.

[0037] To avoid providing unnecessary information to the system operator, the electrical power consumption of the heating device or a parameter proportional thereto can be continuously monitored, or a comparison with a reference curve stored in the control unit can be performed only after a start-up time. The start-up time can be specified or determined by the control unit. The degree of fouling should only be determined when the process and temperature in the cleaning system are stable. The start-up time should be taken into account when switching on the cleaning system and when switching on the pump power. A fixed start-up time can be implemented in the electronic circuit of the control unit, for example, using a delay element. When determined by the control unit, the start-up time can be considered to have expired when the determined value no longer fluctuates but becomes stable.

[0038] In a possible further development of the method for operating a cleaning device, a calibration is advantageously provided which allows for taking into account properties of the heating device that deviate from the tolerance range, which in turn can significantly increase the accuracy of the report on the actual degree of fouling:

[0039] When the cleaning device is put into use for the first time, calibration of the at least one reference curve stored in the control unit is performed, comprising the following steps:

[0040] a) determining the electrical power consumption of the heating device or a variable proportional thereto;

[0041] b) Correction, ie shifting, of the reference curve of the electrical power consumption of the heating device or of a variable proportional thereto so that the initially determined value corresponds to the stored initial value.

[0042] In this case, steps a) and b) are carried out for all available power levels of the pump and all power-specific reference curves are corrected.

[0043] In a possible further development of the method for operating a cleaning device, in operating mode, the activation time of the heating device within a switching cycle of the heating device is extended as a function of the degree of fouling of the heating device. For this purpose, a correction factor (t_corr or T_corr) can be provided. In a first embodiment, the correction factor can be a time correction factor, i.e., a fixed time value (t_corr), which is used starting from a specific degree of fouling, i.e., a specific value of the electrical power consumption of the heating device or a variable proportional thereto, such as 5 seconds for a low degree of fouling, 10 seconds for a medium degree of fouling, and 15 seconds for a high degree of fouling. A design as a separately calculated correction factor is also possible.

[0044] An alternative correction factor T_corr could change the upper switching temperature of the temperature-controlled heating device and increase it with increasing fouling level, for example to 5° C. at a low fouling level, 10° C. at a medium fouling level and 15° C. at a high fouling level.

[0045] In terms of circuitry, the correction factor can be determined or calculated by the microcontroller as a function of the specific degree of fouling, ie starting from a specific value of the electrical power consumption of the heating device or a parameter proportional thereto.

[0046] This refinement advantageously achieves that, despite an increased degree of fouling, the liquid is heated and optionally evaporated completely, and no liquid with an excessively low temperature or steam with a high residual liquid content is produced.

[0047] If the measuring mode of the cleaning device is to be repeated, i.e., if the degree of fouling is to be re-determined, the use of the correction factor t_corr or T_corr for the duration of the determination of the electrical power consumption of the heating device or a variable proportional thereto is suppressed. Therefore, the determination of the electrical power consumption of the heating device or a variable proportional thereto is not falsified by the correction factor t_corr or T_corr.

[0048] In one possible further development of the method for operating a cleaning device, after the cleaning device is switched on, the activation time t_initial of the heating device, which can also be referred to as the preheating time, is adapted as a function of the degree of fouling of the heating device by extending it with a correction factor t_corr, i.e., as a function of the detected value of the electrical power consumption of the heating device or a parameter proportional thereto. To enable the control unit to perform such an adaptation of the activation time, the value of the degree of fouling detected during the last operation of the cleaning device is stored in a memory. The correction factor t_corr can be the same value as that used to extend the activation time in the operating mode, as previously described. Alternatively, the correction factor can be another value stored in the control unit or calculated by the microcontroller of the control unit.

[0049] In contrast to the constant preheating time known from the prior art, by taking into account a correction factor dependent on the degree of fouling, it can be ensured that the pump of the cleaning device is only switched on when the temperature is sufficient despite existing fouling of the heating device. This is particularly relevant when the heating device has a steam generator and liquid is being evaporated.

[0050] The present invention and the advantageous further developments of the invention described above also constitute advantageous further developments of the invention in combination with one another—insofar as this is technically appropriate. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] For further advantages and advantageous structural and functional configurations of the invention, reference is made to the dependent claims and to the description of exemplary embodiments with reference to the drawings.

[0052] The invention will be explained in more detail with the aid of the accompanying drawings.

[0053] in:

[0054] Figure 1 A diagram showing functional elements of a cleaning device;

[0055] Figure 2 An equivalent circuit diagram showing a cleaning device;

[0056] Figure 3a a and b show diagrams of the activation time (on time) of the heating device in the new and fouled state;

[0057] Figure 3c A diagram showing activation times taking into account correction factors;

[0058] Figure 4a shows a reference curve comprising three limit values ​​stored in the control unit;

[0059] Figure 4b shows the calibration process by moving the reference curve;

[0060] Figure 4c Different reference curves are shown, wherein the respective reference curve is assigned to a specific pump power;

[0061] Figure 5 The diagram shows the activation time after switching on the cleaning device, taking into account the correction factor. DETAILED DESCRIPTION

[0062] Figure 1 A diagram shows the functional elements of a cleaning device 10. In cleaning device 10, liquid 100 is transported from a liquid container 1 to a heating device 2, where it is converted into steam 101 by heating. Steam 101 is applied to a cleaning element 8, which can be implemented as a fabric pad like a mop. The surface 1000 to be cleaned is cleaned by the relative movement of cleaning element 8 over the surface.

[0063] A control unit 3 is provided for operating the cleaning device 10. The control unit 3 can be connected to an output unit 3.1 or have such an output unit for outputting information to the machine operator. Furthermore, the control unit can have an input unit, such as an electric switch.

[0064] The heating device 2 is operated electrically (power supply 5 is not shown here). The heating device 2 and its heating element 2.1 are temperature-controlled and maintained within a defined or predetermined temperature range. For switching on and off, i.e., temporarily applying current, a temperature regulator 4 is provided, which here has a fixed switching temperature. In the example shown, the temperature regulator is designed as a bimetallic switch.

[0065] Heat transfer from the heating device 2 to the liquid 100 takes place on the surface of the heating element 2 that is in contact with the liquid. As shown in the figure, this surface is already covered with a scaling layer 20 that impairs the heat transfer.

[0066] Figure 2 The equivalent circuit diagram of a cleaning device 10 is shown. A heating element 2.1 is connected to a power source 5 and can be supplied with current. A temperature controller 4 is provided for timed activation of the heating element 2.1, which ensures that the heating device 2 maintains a predetermined or fixed temperature. To protect the heating element 2.1, an optional electrical fuse 6 is also provided in the illustrated embodiment. A hydraulic pump 7 is provided for transporting the liquid 100, which is also connected to the power source 5. The pumping power of the hydraulic pump 7 can be adjusted continuously or by selecting different power levels.

[0067] The control unit 3 (not shown) has means for determining the electrical energy consumption (E) of the heating device 2 or a variable (ROT) proportional thereto and at least one reference curve R stored in the control unit 3 .

[0068] The device for determining this continuously monitors the electrical power consumption (E) of the heating device 2 or a variable proportional thereto (ROT). In a subsequent step, a comparison is then performed with a reference curve (R) stored in the control unit 3 to determine the degree of fouling of the heating device 2. Tests for determining the reference curve are performed in advance during production. The values ​​of the electrical power consumption (E) of the heating device 2 or a variable proportional thereto (ROT) that are relevant for determining the degree of fouling are thus known. Depending on the result of the comparison, information is output to the system operator via the output unit 3.1.

[0069] Figure 3a a and b show diagrams of the activation time (on time) of the heating device 2 in the a) new and b) fouled state. For this purpose, the activation time of the heating device, as detected by a device for determining the electrical energy consumption (E) of the heating device 2 or a variable proportional thereto (ROT), is recorded over time. The switching cycle of the heating device here extends over the sum of the activation time t_on and the time t_off during which the heating device 2 is inactive. It should be understood that the time interval between the activation time t_on of the heating device 2 and the energy consumption E thereby decreases with increasing fouling, i.e., t_on becomes smaller. Alternatively, the relative activation time decreases, i.e., t_on / (t_on+t_off) decreases. This variable is represented as ROT, i.e., relative on time, in the diagrams described below.

[0070] Figure 3c The diagram shows the activation time t_on taking into account the correction factor t_corr.

[0071] If, despite an increased degree of fouling, the liquid 100 should be heated and, if necessary, evaporated completely, and no liquid 100 with an excessively low temperature or steam 101 with an excessively high residual liquid content should be produced, then in the operating mode of the cleaning device 10 shown here, the activation time t_on of the heating device 2 within a switching cycle of the heating device 2 can be extended depending on the degree of fouling of the heating device 2. For this purpose, a correction factor t_corr is set. As a result, the duration of the electrical energy consumption E in the corresponding switching cycle is extended.

[0072] Figure 4aA reference curve R stored in the control unit 3 is shown with three defined limit values ​​G1, G2, G3. At a first time t1, the first limit value G1 is reached or passed, at a second time t2, the second limit value G2 is reached or passed, and at a third time t3, the third limit value G3 is reached or passed.

[0073] When the corresponding limit values ​​G1, G2, G3 are exceeded, the control unit 3 causes the output of information to the system operator via the output unit 3.1. For possible configuration and output of this information, reference is made to the above-described embodiments.

[0074] Here and in the figures described below, the reference curve is shown as a linearly descending straight line. This representation was chosen for simplicity. The curves obtained from experiments and measurements usually deviate from this and have various curvatures.

[0075] Figure 4b The calibration process by moving the reference curve R is shown.

[0076] When the cleaning device 2 is put into operation, at time t0 a calibration of at least one reference curve R stored in the control unit 3 is performed, comprising the following steps:

[0077] a) Determining a variable (ROT) proportional to the electrical power consumption (E) of the heating device 2

[0078] b) The reference curve R is corrected by correcting it, i.e., shifting it, so that its starting value corresponds to the value determined in step a) at time t0. If the determined value is higher, for example, approximately 90% in the example shown, the reference curve R0 is shifted upward (see arrow) so that its value at t0 increases from approximately 75% to approximately 90%. The calibrated reference curve is denoted by Rcal in the figure.

[0079] Figure 4c By way of example, various reference curves are schematically illustrated, wherein the respective reference curves are assigned to specific pump powers of the hydraulic pump 7 of the cleaning device 10, i.e., a first reference curve R1 is assigned to a first pump power, a second reference curve R2 to a second pump power, and a third reference curve R3 to a third pump power. The reference curves are thus pump power-specific and are selected according to the prevailing pump power.

[0080] Figure 5 The diagram shows the activation time t_on after the cleaning device 10 is switched on at the time t0 , taking into account the correction factor t_corr.

[0081] In order to ensure a sufficiently long preheating of the heating device 2 before activating the pump 7 of the cleaning device 10 at the activation time t_P, the activation time t_initial of the heating device 2 can be extended by the correction value t_corr after switching on the cleaning device 10, depending on the degree of fouling of the heating device 2. This extends the duration of the electrical energy consumption E during preheating.

[0082] Reference Signs List

[0083] 1 liquid container

[0084] 2 Heating device (such as boiler)

[0085] 2.1 Heating element

[0086] 3Control unit

[0087] 3.1 Output Unit

[0088] 4. Temperature regulator (e.g. temperature switch)

[0089] 5. Power Supply

[0090] 6. Electrical safety device

[0091] 7 pumps

[0092] 8 Cleaning element (e.g. wiping pad)

[0093] 10. Cleaning Equipment

[0094] 20 scaling layer

[0095] 100 liquid (such as water)

[0096] 101 Steam (e.g. water vapor)

[0097] 1000 surfaces to be cleaned (e.g. the floor of a room)

[0098] E Electricity consumption

[0099] t_on The time interval during which the heating device is activated (switched on)

[0100] t_off Time interval during which the heating is inactive (off)

[0101] t_initial warm-up phase

[0102] t_P Pump switch-on time

[0103] t0 activation time

[0104] t1 The first moment when the first limit value G1 is reached

[0105] t2 The second moment when the second limit value G2 is reached

[0106] t3 The third moment when the third limit value G3 is reached

[0107] R reference curve

[0108] R0 uncalibrated reference curve

[0109] Rcal is the reference curve to be calibrated

[0110] R1 Pump power specific reference curve for the first pump power

[0111] R2 Pump power specific reference curve for the second pump power

[0112] R3 Pump power specific reference curve for the third pump power

[0113] Relative activation time of the ROT heater

Claims

1. Cleaning equipment (10), including: Cleaning element (8); Liquid container (1); a current-operated, temperature-controlled heating device (2), in particular with a steam generator, for heating a liquid (100); and a control unit (3) for operating the cleaning device (10), It is characterized in that The control unit (3) has means for determining the electrical power consumption (E) of the heating device or a variable (ROT) proportional thereto and at least one reference curve (R) stored in the control unit (3).

2. The cleaning device according to claim 1, It is characterized in that The heating device (2) can be operated with a constant heating power and is provided with a temperature regulator (4) for switching the heating device (2), wherein the temperature regulator (4) has a fixed switching temperature, and The temperature regulator (4) is in particular designed as a bimetallic switch.

3. The cleaning device according to claim 1, It is characterized in that The cleaning device (10) has an output unit (3.1) for outputting information to a device operator.

4. The cleaning device according to claim 1, It is characterized in that The cleaning device (10) has a controllable pump (7) for transporting the liquid (100), which can be operated with different pump powers, and a reference curve (R1, R2, R3) of the electrical power consumption (E) of the heating device or a variable (ROT) proportional thereto is stored in the control unit (3) for each of the different pump powers.

5. Method for operating a cleaning device (10) according to one of the preceding claims, It is characterized in that In a measuring mode, detection is performed by means of a device for determining the electrical power consumption (E) of the heating device (2) or a variable (ROT) proportional thereto, A comparison is made with a reference curve (R) stored in the control unit (3) for determining the degree of fouling of the heating device (2) and Information is output to the plant operator depending on the result of the comparison.

6. Method for operating a cleaning device according to claim 5, It is characterized in that The reference curve (R) has at least one limit value (G1, G2, G3), beyond which the output of the information occurs.

7. Method for operating a cleaning device according to claim 5, It is characterized in that The means for determining detects an activation time (t_on) of the heating device (2) within at least one switching cycle of the heating device (2), and The reference curve (R) depicts the activation time (ROT) as the degree of fouling of the heating device (2) increases over time (t).

8. Method for operating a cleaning device according to claim 7, It is characterized in that In a preceding method step, the type of the surface to be cleaned is determined, and the reference curve (R) has type-specific limit values ​​(G1, G2, G3).

9. Method for operating a cleaning device according to claim 7 or 8, It is characterized in that The system operator can confirm the receipt of this information by actuating the switching element and subsequently terminate the output of this information.

10. Method for operating a cleaning device according to any one of claims 5 to 9, It is characterized in that The electrical power consumption (E) of the heating device (2) or a variable (ROT) proportional thereto is detected or compared with a reference curve (R) stored in the control unit (3) only after the start-up time.

11. Method for operating a cleaning device according to any one of claims 5 to 10, It is characterized in that When the cleaning device (2) is put into use, calibration of the at least one reference curve (R) stored in the control unit (3) is performed, comprising the following steps: a) determining the electrical power consumption (E) of the heating device (2) or a variable proportional thereto (ROT), b) A reference curve (R) for correcting the electrical power consumption of the heating device or a variable proportional thereto.

12. Method for operating a cleaning device according to any one of claims 5 to 11, It is characterized in that In operating mode, the activation time (t_on) of the heating device (2) within one switching cycle of the heating device (2) is extended by a correction factor (t_corr) depending on the degree of fouling of the heating device (2).

13. Method for operating a cleaning device according to any one of claims 5 to 12, It is characterized in that After switching on the cleaning device (10), the activation time (t_initial) of the heating device (2) is extended by a correction factor (t_corr) depending on the degree of fouling of the heating device (2).

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