Dishwasher and method for operating a dishwasher

Abstract

The invention relates to a method for operating a dishwasher to carry out a cleaning program, wherein a target temperature of the wash liquor is predetermined in at least one heating phase. The method is characterized by the following steps: - Detecting the energy (E) absorbed by a heating element (8) during the at least one heating phase for heating the wash liquor; - Comparing the energy (E) absorbed during the at least one heating phase with a predetermined maximum energy; and - Operating the heating element (8) as long as the absorbed energy (E) is less than the predetermined maximum energy. The invention further relates to a dishwasher configured for carrying out the method.

Description

[0001] The invention relates to a method for operating a dishwasher to carry out a cleaning program, wherein a temperature to be achieved for a wash liquor during a heating phase is predetermined. The invention further relates to a dishwasher suitable for carrying out the method.

[0002] Dishwashers clean loaded dishes and cutlery by spraying a cleaning liquid, also called rinsing water, onto the dishes and cutlery from below, usually with the help of rotating spray arms. To achieve the desired cleaning effect, the rinsing water is heated before and during the cleaning phase, among other things to dissolve the cleaning agent in the rinsing water and activate its active ingredients. The cleaning phase is usually followed by a final rinse phase, in which the cleaning agent is washed off the dishes and cutlery in a similar way using clear water and a rinse aid. This also runs more effectively at a higher temperature, so that the fresh water added for the final rinse phase is also heated.The final rinse phase is followed by a drying phase, during which the dishes are dried based on the temperature at the end of the final rinse phase and the associated stored heat. The effectiveness of the final rinse process depends on the temperature of the wash liquor during the final rinse phase. The drying effect during the drying process is primarily influenced by the stored heat and thus by the temperature at the end of the final rinse phase.

[0003] A high temperature is beneficial for the effectiveness of the cleaning and drying processes. However, achieving high temperatures requires a lot of energy. In an effort to make dishwashers energy-efficient and to raise consumer awareness of the importance of high energy efficiency, many countries have introduced energy efficiency classes ("energy labels") that specify certain maximum energy consumption of dishwashers for a defined standard load, also known as the reference load. In order for a dishwasher to achieve a certain energy efficiency class, the manufacturer specifies cleaning process parameters that lead to good washing and drying results with the underlying standard load of the dishwasher, without exceeding the specified amount of energy. The specification of maximum temperatures for the washing solution that can be used in the cleaning phase orThe temperature achieved in the final rinse phase is an important and decisive factor. The cleaning and final rinse phases are then operated with temperature control for the wash liquor, such that the wash liquor usually just reaches the specified temperature at the end of the cleaning phase or the end of the final rinse phase.

[0004] Since process optimization is based on standardized tableware and cutlery composition, a deviating dishwasher load may result in less than optimal cleaning and drying results in all respects. Drying of tableware and cutlery items with low heat retention capacity, such as plastic or thin-walled sheet metal items, such as cookware, is often suboptimal.

[0005] EP0953890 discloses a method for operating a dishwasher in which a limit value for energy consumption is provided, the reaching of which influences the further course of a cycle. During a heating phase, the heater for heating the wash liquor is switched off when a predetermined wash liquor temperature is reached, but also when a predetermined heating time has been reached without the predetermined wash liquor temperature being reached.

[0006] It is an object of the present invention to provide an operating method for a dishwasher of the type mentioned at the outset and a dishwasher carrying out this method, in which good drying results are achieved even for different types of dishes or cutlery and yet predetermined energy quantities for the cleaning program are maintained.

[0007] This object is achieved by a method and a dishwasher having the features of the respective independent claim. Advantageous embodiments and further developments are the subject of the dependent claims.

[0008] In a method according to the invention, during at least one heating phase of the cleaning program, energy consumed for heating is recorded and heating is continued even above the predetermined temperature as long as a maximum amount of energy provided for the at least one heating phase is not reached.

[0009] Dishware with a lower heat capacity, which according to the prior art is only heated to the specified temperature in the final rinse phase, dries inadequately in the subsequent drying phase. The invention is based on the finding that, due to the lower heat capacity, less energy is consumed when heating such dishware than is planned for this process for a standard load. Accordingly, with a temperature-controlled heating phase, a residual amount of energy would remain unused. This residual energy is used according to the invention to heat the dishware to a higher temperature, which in turn leads to better drying and / or cleaning.By recording the amount of energy during the heating process and carrying out the heating process based on a comparison of the maximum amount of energy allocated to this heating process and the amount of energy actually used for the process, it is automatically achieved that when loaded with wash items with a lower heat capacity, the wash items are brought to a higher initial temperature for the drying process than when loaded with wash items with a high heat capacity.

[0010] The at least one heating phase can be part of a cleaning phase and / or a final rinse phase of the cleaning program. In a preferred embodiment of the operating method, the total energy consumed is determined across the cleaning phase and the final rinse phase of the cleaning program. A heating phase of the cleaning phase is terminated based on temperature or time control, and a heating phase of the final rinse phase is controlled based on a comparison of the consumed energy and the maximum energy. This ensures that cleaning is carried out at the intended temperature and that the total available energy is used for an optimal drying result.

[0011] To determine the energy consumed by the heating element, the heating element's power is preferably determined and integrated. The heating element's power can be determined from measured current and / or voltage values. If instantaneous current and voltage values ​​are measured, the power determination is accurate even for an AC-operated heating element with inductive load components. A simplified power determination can be performed assuming a purely resistive load by determining the heating element's power based on a measured voltage value and a specified resistance of the heating element.

[0012] In an advantageous embodiment of the method, energy quantities required to operate components of the dishwasher other than the heating element are deducted from the total energy available for the cleaning program in order to determine the maximum energy available for the at least one heating phase. This makes it possible to focus on the total energy quantity actually of interest. Preferably, a control device of the dishwasher can perform this calculation itself. For this purpose, energy quantities required by the other components (e.g. a rinse water pump) during the cleaning program can be predetermined. It is also conceivable for the control device to determine these energy quantities itself in previously completed cleaning programs.

[0013] A dishwasher according to the invention is characterized in that an energy measuring device is provided for determining the energy consumed by the heating element during at least one heating phase of the wash liquor, and in that the dishwasher is configured to carry out the aforementioned method. The advantages mentioned in connection with the method result.

[0014] The invention is explained in more detail below using an exemplary embodiment with the aid of figures. The figures show: Fig. 1 shows a schematic sectional view of a dishwasher; and Fig. 2 shows diagrams of time courses of various variables during an operating process for a dishwasher.

[0015] Fig. 1 shows a schematic diagram of a dishwasher in a vertical sectional view.

[0016] The dishwasher, which can be a household appliance as well as a machine for professional use, has a body 1 with a door 2, which surrounds a washing chamber 3. Within the washing chamber 3, there are usually several, here for example two, wash baskets 4 arranged one above the other. In addition, a Fig. 1 An unspecified cutlery carrier is provided. Various items 12 are arranged in the dishware baskets 4, for example. In alternative embodiments of the dishwasher, a cutlery basket may be provided in one of the dishware baskets 4 instead of or in addition to the cutlery carrier.

[0017] Typically, each of the wash baskets 4 is assigned a spray arm 5, which rotates during washing operation and sprays washing liquid, also called rinsing liquor, onto the wash items 12. In a lower area (base area) of the dishwasher, the washing liquor collects in a washing sump 6, also called a washing liquor pot, from which it can be pumped to the spray arms 5 by means of a washing liquor pump 7. Also arranged in the washing sump 6 is a heating element 8, usually a resistance heater, whose supply lines are connected to an energy measuring device 9. The energy measuring device 9 and its function within the scope of an operating method according to the invention will be described in connection with Fig. 2explained in more detail below. Furthermore, a temperature sensor 10 is arranged in the wash sump 6 in order to determine the temperature of the wash liquor in the wash sump 6. Furthermore, the dishwasher has a control device 11, which in the model shown is arranged in the door 2 and which controls the sequence of the operating method.

[0018] Fig. 2 shows, in three schematic diagrams, the time profiles of various parameters or variables changing during the operating process. On a horizontal axis, which applies equally to all three diagrams, the elapsed time t of the operating program is indicated in seconds.

[0019] The upper diagram shows the example with the temperature sensor 10 according to Fig. 1Measured temperature T of the wash liquor during the operating process in the form of a temperature curve 13. The temperature curve 13 is shown as a solid curve. In the middle diagram, a power P, specified in watts, absorbed by, for example, the heating element 8 is shown as a power curve 14 in a dash-dotted curve. Finally, the lower diagram shows the cumulative energy E absorbed by the heating element 8 during the operating process in an energy curve 15 as a dashed curve. The energy E is given, for example, in watt-seconds (Ws).

[0020] From the representation in the middle diagram of the Fig. 2Two longer heating periods emerge, during which the heating element 8 is energized to heat the wash liquor. In the temperature curve 13 of the wash liquor, the heating phases are shown in sections in which the temperature T increases essentially linearly. The first heating phase, which lies approximately between 500 and 1800 seconds of the time t, serves to heat the wash liquor during or for a cleaning phase. The second heating phase, which lies approximately between 4100 and 4800 seconds of the time t, serves to heat the wash liquor in the final rinse phase.

[0021] According to the application, the amount of energy supplied to the heating element 8 is recorded at least during the heating phase of the final rinsing step and, if applicable, additionally during the heating phase of the cleaning step. For this purpose, the energy measuring device 9 is used, which, for example, performs a power measurement, whereby the absorbed energy is determined as the integral of the absorbed power over time.

[0022] This relationship is also evident from the lower diagram of the Fig. 2 visible. In the phases in which the heating element 8 is operated and a substantially constant power P is consumed, the energy E increases linearly.

[0023] The washing liquor is heated up until a predetermined maximum energy is reached, even if the temperature T rises above a value that is higher than a predetermined value that was determined when the dishwasher was loaded with reference wash ware. This ensures that precisely those wash ware 12 that have a low heat capacity and whose temperature would not be sufficient for satisfactory drying at the start of the drying process are heated to a higher temperature. Conversely, even under particularly unfavorable ambient conditions (e.g. very cold water in the inlet, a particularly large amount of dishes), the washing liquor is only heated up until a predetermined maximum energy is reached, even if the temperature T has not yet reached a predetermined value that was determined when the dishwasher was loaded with reference wash ware.By recording the energy absorbed by the heating element 8, it is ensured in any case that specifications for the total energy consumption of the operating process are not exceeded, but are fully utilized.

[0024] A similar procedure can be used for the first heating period, i.e., heating the wash water for the cleaning step. In this case, the higher temperature leads to better cleaning results, which is also advantageous in connection with, for example, pots that have a lower heat capacity.

[0025] A maximum energy can be specified separately for each of the two heating phases. Alternatively, a maximum energy can be specified that applies to both heating phases in total. The first heating phase (during the cleaning phase) is then terminated based on temperature or time control, while the second heating phase (during the final rinse phase) is carried out taking the allocated maximum energy into account.

[0026] Advantageously, it can be provided that the control device 11 itself calculates the maximum energy permitted for the heating phase(s) based on a predetermined maximum total energy consumption of the cleaning program. For this purpose, the control device 11 can be predefined with the energy quantities required by all other components (e.g., the rinse water pump 7) during the cleaning program. It is also conceivable for the control device 11 to determine these energy quantities itself in previously completed cleaning programs. However, this requires an additional device for measuring the energy consumed, either for these additional components or for the entire dishwasher.

[0027] To determine the energy consumed by the heating element 8, the energy measuring device 9 can perform a "true" power measurement ("true RMS" power measurement). Since the dishwasher is typically operated on an AC power supply network, a time-resolved current and voltage measurement is required to measure the actual power consumed. The product of the currently measured current and voltage values ​​represents the instantaneous power consumed, which is integrated over the operating time to determine the energy consumed.

[0028] Since heating element 8 is a resistive load in which current and voltage are in phase, power measurement can be simplified by determining only the effective values ​​of current and voltage, with the power then being the product of the measured effective values ​​of voltage and current. Assuming that the resistance of heating element 8 changes only insignificantly during operation, a significant simplification could be assumed to assume a constant current during operation. With a known mains voltage, power could then be determined solely from the operating time.

[0029] However, this approach presents a potential source of error: the calculated power deviates from the actual power consumption, since the mains voltage is not the same at all grid connection points and not at all times. As a compromise for a simple yet accurate determination of the power consumption and thus the energy consumption, it is possible to assume a constant resistance R of the heating element 8, but to measure the voltage U and calculate the power consumption P using the relationship P = U 2< / R.

[0030] In summary, the operating procedure according to the application results in a cleaning program sequence of the dishwasher which guarantees compliance with the specified energy consumption values ​​of the respective energy label while achieving the best possible cleaning and drying results. Reference symbol

[0031] 1 Body 2 Door 3 Washing chamber 4 Dish basket 5 Spray arm 6 Wash sump 7 Wash liquor pump 8 Heating device 9 Energy measuring device 10 Temperature sensor 11 Control device 12 Dishes 13 Temperature curve 14 Power curve 15 Energy curve

Claims

1. Method for operating a dishwasher in order to carry out a cleaning program, a temperature to be reached of a washing solution being specified in at least one heating phase, comprising the following steps: - detecting energy (E) of a heating element (8) absorbed during the at least one heating phase for heating the washing solution; - comparing the energy (E) absorbed in the at least one heating phase with a specified maximum energy; and - operating the heating element (8) as long as the absorbed energy (E) is less than the specified maximum energy, characterised in that the heating of the washing solution is continued in the heating phase by continuing to operate the heating element (8) even above the specified temperature of the washing solution, as long as the absorbed energy (E) is less than the specified maximum energy.

2. Method according to claim 1, in which the at least one heating phase is part of a cleaning phase and / or final rinsing phase of the cleaning program.

3. Method according to claim 2, in which the absorbed energy is determined in total over the cleaning phase and the final rinsing phase of the cleaning program, wherein a heating phase of the cleaning phase is ended in a temperature- or time-controlled manner and a heating phase of the final rinsing phase is controlled based on the comparison of the absorbed energy (E) and the maximum energy.

4. Method according to any of claims 1 to 3, in which a power (P) of the heating element (8) is determined and integrated in order to determine the absorbed energy (E).

5. Method according to claim 4, in which the power (P) of the heating element (8) is determined from measured values for current and / or voltage.

6. Method according to claim 4, in which the power (P) of the heating element (8) is determined based on a measured voltage value and a specified resistance of the heating element (8).

7. Method according to any of claims 1 to 6, in which known amounts of energy required to operate components of the dishwasher other than the heating element (8) are deducted from a total amount of energy available for the cleaning program in order to determine the maximum energy available for the at least one heating phase.

8. Dishwasher comprising a heating element (8) for heating a washing solution, characterised by an energy measuring device (9) for determining energy absorbed by the heating element (8) during at least one heating phase of the washing solution, the dishwasher being designed to carry out an operating method according to any of claims 1 to 7.

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