CN112971659A

CN112971659A - Method for operating a dishwasher

Info

Publication number: CN112971659A
Application number: CN201911273879.6A
Authority: CN
Inventors: 杨华
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2021-06-18

Abstract

A method of operating a dishwasher, comprising: (1) adding a detergent to a cleaning liquid circulating within the dishwasher; (2) measuring the conductivity of the cleaning liquid and determining the rate of change of the conductivity due to dissolution of the cleaning agent in the cleaning liquid; (3) comparing the rate of change of conductivity to a predetermined threshold to determine the rate of dissolution of the detergent that has been added to the cleaning solution in step (a); and adjusting the operating parameter based on the determination of step (C).

Description

Method for operating a dishwasher

Technical Field

The invention relates to a method for operating a dishwasher.

Background

In modern dishwashers, there is always a greater effort to provide automatic selection and self-regulation of the operating parameters of the washing program with which the dishwasher is operated, in order to optimize such washing programs in terms of efficiency, washing effect, power consumption, water consumption, duration, etc.

To this end, modern dishwashers may be equipped with a plurality of sensors which determine some prevailing conditions within the dishwasher in order to obtain information about parameters which may vary between different washing cycles, such as the type, number and degree of soiling of the articles loaded into the dishwasher or the properties of the cleaning liquid circulating in the dishwasher, such as temperature, water hardness, detergent concentration, etc.

One type of sensor that has been used in washing machines or dishwashers is a conductivity sensor, i.e. a sensor adapted to measure the conductivity of the washing liquid circulating in the dishwasher.

In most existing examples of use of conductivity sensors in dishwashers or washing machines, the conductivity sensor is used to determine the detergent concentration to maintain a constant detergent supply or concentration. Thus, for example, in DE-a-102004002647, it is proposed to provide a washing machine or dishwasher with a conductivity sensor which can be used to determine the detergent concentration in order to adjust the dosage of detergent.

Similarly, in WO-A-00/27703A detergent dispenser for A commercial dishwasher is proposed, wherein the detergent dispenser comprises A conductivity sensor for measuring the detergent concentration of the washing liquid, and wherein the detergent dispenser is designed to provide additional detergent in case the conductivity sensor detects that the detergent concentration has fallen below A certain level.

A similar arrangement is proposed in US-A-4211517, where A commercial dishwasher is proposed, equipped with A conductivity sensor measuring the pH level in the dishwasher sump, to maintain A desired constant detergent supply.

Furthermore, in EP-B-0117471, a washing machine or dishwasher is disclosed which comprises a conductivity sensor for detecting the detergent concentration, and which is designed to supply more detergent if the detergent concentration drops below a certain level, in order to provide a substantially constant detergent concentration in the washing liquid circulating throughout the washing machine or dishwasher.

In US-A-5765724, A dispenser of pasty cleaning agent is disclosed, wherein A conductivity sensor measures the concentration of cleaning agent, so that if the concentration of cleaning agent drops below A certain level, an alarm signal is generated to inform the user that the cleaning agent paste has run out and that new cleaning agent should be added.

In addition to the use of ｃA conductivity sensor for measuring the detergent concentration, EP- ｃA-1688529 proposes ｃA washing machine equipped with ｃA conductivity sensor arranged in the water circulation pipe downstream of the detergent container. Here, the washing machine is designed for measuring the conductivity of the washing liquid during the flushing of the detergent container. If the measurement signal generated by the conductivity sensor no longer changes, it is assumed that the detergent has completely flushed out of the detergent container and the water supply through the detergent container is stopped.

DE-a-19534431 discloses a washing machine equipped with a conductivity sensor for detecting the degree of soiling of the washload. For this purpose, the conductivity sensor measures the change in conductivity during the wash load soak, i.e. before the addition of detergent. The degree of soiling is determined by comparison of measurements made at the beginning and at the end of the soaking step, in order to adjust the amount of detergent to be added to the subsequent washing step.

Also, there is known from EP-B-0686721 a washing machine in which a motor driving a tub is first operated at a varying speed, and during the operation at the varying speed, a load on the motor is detected to determine the amount of laundry that has been loaded into the tub. In addition, a conductivity sensor is used to determine the quality of the water in rinsing the tub, wherein, depending on the determination, the amount of water to be used in the subsequent rinsing step is selected.

Finally, the method of operating a dishwasher described in DE-B-19650915 makes use of the fact that detergents of different chemical compositions, such as, for example, enzyme-containing detergents and alkaline detergents, lead to different conductivities of the washing liquids to which the detergents are added. In the method described in DE-B-19650915, the conductivity of the washing liquid is measured after detergent has been added thereto, in order to obtain an absolute conductivity value, from which the detergent type is determined, and the process steps of the corresponding washing program are activated. Although the method proposed in DE-B-19650915 is capable of distinguishing detergents of different chemical compositions, it is not possible to distinguish detergents having similar chemical compositions but having different physical compositions, as is the case for example in detergents for dishwashers which are available in powder form and in tablet form.

Disclosure of Invention

It is an object of the present invention to provide a method of operating a dishwasher which enables further adjustment and thus optimization of the washing program, and in particular to provide a method of operating a dishwasher which provides optimal dissolution of a detergent which has been added to the washing liquid.

According to the invention, this object is solved by a method of operating a dishwasher as defined in claim 1 of the present invention.

Unlike prior art methods, in which the conductivity of the cleaning liquid is measured to provide an indication of whether a certain concentration of detergent is contained in the cleaning liquid, to control the addition of detergent to the cleaning liquid or to adjust the duration of the water supply or the amount of water supply used in the rinsing step, in the method according to the invention a conductivity sensor is used to detect how fast the detergent is dissolved, thereby adjusting the washing program according to this determination. This way of determination is particularly advantageous in dishwashers, since it enables to detect whether a fast dissolving detergent or a slow dissolving detergent, for example a detergent in powder form or a detergent in tablet form, has been added to the dishwasher, which was not possible in the methods and systems known hitherto. Thus, especially when multi-component detergent tablets are applied (e.g. so-called 3 in 1, 4 in 1, 5 in 1 etc. detergents, where different types of agents, such as detergents, glass protection agents, rinse aids, salt components, dish treatment agents etc. are compressed in one tablet), since the components of the detergent tablet should be effective at different times of the wash cycle, these tablets are designed to dissolve much slower than detergents provided in powder form into the dishwasher and thus require a completely different set of operating parameters of the wash cycle to provide optimum efficiency of the wash cycle.

Preferred embodiments of the invention are defined in the dependent claims.

According to a preferred embodiment, before step (a), i.e. before adding detergent to the washing liquid, the conductivity of the washing liquid is measured to obtain a reference value, which is used in the determination step of step (B), i.e. in the determination step of the rate of change of the conductivity caused by the dissolution of the detergent in the washing liquid. By applying this reference value, the determination step of step (B) is more reliable, since it takes into account any change in conductivity of the washing liquid that has been caused before the addition of detergent, for example by dirty particles or detergent residues present in the dishwasher from a previous washing cycle or from items loaded in the dishwasher.

Preferably, the method further comprises determining a conductivity reference value representative of the conductivity of the fresh water supplied to the dishwasher, and then using the conductivity reference value of the fresh water in the determining step of step (B). By applying the fresh water conductivity reference value in step (B), the determination step of the change in conductivity caused by the dissolution of the detergent takes into account any change in conductivity that may be caused by a change in conductivity of the fresh water supplied to the dishwasher.

The fresh water conductivity reference value can also be preset in the operating program of the dishwasher. That is, considering that although the conductivity of the fresh water may have regional differences, in a particular region the conductivity of the fresh water is usually more or less constant and thus may be preset with sufficient accuracy in the operating program of the dishwasher when the dishwasher is installed in a certain region, instead of measuring the fresh water conductivity at the start of each new washing cycle, the conductivity reference value of the fresh water may thus be permanently set by the user in the operating program of the dishwasher.

According to a preferred embodiment of the method proposed herein, in step (B), the conductivity of the washing liquid is measured more than once, to provide a more accurate and thus more reliable measurement.

In step (B) of the method, the change in conductivity may be recorded as a function of time, such that the slope of the function may be determined in step (B) and compared to a predetermined threshold slope in step (C).

Additionally or alternatively, absolute conductivity values may be measured and compared to one or more threshold values to determine detergent dissolution rates.

When a plurality of predetermined thresholds are provided and wherein the rate of change of conductivity is specified (associated to) in step (C) as one of a plurality of ranges defined by said predetermined thresholds, the washing program can be more accurately adjusted to accommodate the detergent dissolution rate. In this way, it is possible not only to distinguish essentially between a detergent in powder form and a detergent in tablet form, but also to distinguish between slower and faster dissolving detergents in the detergent classification, for example between different types of detergent tablets.

The parameter adjusted in step (D) may be an operation parameter of the pre-washing stage, the main washing stage and/or the intermediate washing stage according to the determination result obtained in step (C). Thus, for example, if it is detected in step (C) that detergent in powder form has been added to the washing liquid, the pre-wash stage can be shortened or even omitted, so that no detergent is consumed in the pre-wash stage, but is saved for the main wash stage.

The parameter adjusted in step (D) in dependence of the determination of the detergent dissolution rate may be any operational parameter of the washing program, such as the selection of the individual program steps, the duration of the individual program steps, the timing of the individual program steps, the temperature of the washing liquid circulated in the dishwasher, the temperature of the air in the dishwasher (which is different from the temperature of the washing liquid and which may be adjusted by further heating elements, such as electrical heating elements arranged in or near the washing compartment), the amount of fresh water supplied to the dishwasher, the speed of the circulation pump (i.e. the timing, when, how long and how fast the pump is driven), and the speed of a similar drain pump, etc.

In order to provide optimum utilization of the cleaning agent added in step (a), the method may be designed such that: if it is determined in step (C) that the dissolution rate is below the predetermined threshold, then in step (D) a longer program duration is selected for the washing step that is to use the detergent added in step (A). Preferably, if a longer duration is selected in step (D), the heating in said step is delayed to provide an interval with a substantially constant temperature. When designing the method in this way, the washing program takes into account that the detergent takes longer to dissolve completely and that longer circulation within the washing compartment of the dishwasher takes place for a sufficient time to provide a satisfactory cleaning effect. Although it has been found that there are some temperature ranges that are optimal for the detergent to function fully and most effectively, it is preferred that the heating step provides an interval (interval) with a substantially constant temperature. For example, for enzyme-containing cleaners, a temperature range of 40 to 45 ℃, particularly about 42 ℃ has proven most effective.

If a longer program duration is selected in step (D), this lengthening in time can be at least partially compensated by shortening the subsequent program steps, by carrying out the individual program steps at a higher temperature and/or by carrying out the individual program steps at a higher speed of the circulation pump for the circulation of the washing liquid in the dishwasher. In case the duration of the washing program is of no consequence, for example when the dishwasher is operated at night, such a compensation can be omitted in order to avoid any possible energy increase or washing efficiency reduction that may be caused by the aforementioned measures.

As mentioned above, the method proposed herein can be used to determine in step (C) whether a detergent in powder form or a detergent tablet has been added in step (a). In such embodiments, the method may further comprise predetermining an average detergent tablet dissolution duration that is generally required for the detergent tablet to dissolve in the cleaning liquid. Then in step (B) the rate of change of conductivity is determined by measuring the conductivity of the cleaning liquid at a time after the addition of detergent which is shorter than the average detergent tablet dissolution time.

Furthermore, an average detergent powder dissolution time period, which is typically required for a detergent powder to dissolve in the cleaning liquid, may be determined, such that the rate of change of the electrical conductivity may be determined in step (B) by measuring the electrical conductivity of the cleaning liquid at a time after the addition of detergent which is shorter than the detergent tablet dissolution time period, but longer than the average detergent powder dissolution time period. By thus selecting the point in time for measuring the conductivity of the cleaning liquid, at which the cleaning agent should be completely dissolved if cleaning agent in powder form is supplied, but at which the cleaning agent tablet should only be partially dissolved, it is possible to reliably distinguish whether cleaning agent or cleaning agent tablet in powder form has been added.

Alternatively, an average detergent powder dissolution time period required for the detergent powder to dissolve in the cleaning liquid is predetermined, and the rate of change of the conductivity is determined in step (B) by measuring the conductivity of the cleaning liquid at a time after the detergent addition that is shorter than said average detergent powder dissolution time period. When at such a point in time that neither the powder form detergent nor the tablet form detergent is completely dissolved, it is still possible to reliably distinguish whether the powder form detergent or the tablet form detergent has been added or not, due to the higher dissolution rate of the powder form detergent.

Drawings

Preferred embodiments of the present invention are described in more detail by reference to the accompanying drawings, in which:

FIG. 1 shows a graph illustrating the determination of dissolution rate according to the present invention; and

fig. 2 shows an example of the operation of a dishwasher according to the method proposed herein.

Detailed Description

Figure 1 shows a graph showing the change in conductivity over time during the first part of the wash phase. At the beginning of this washing phase, in phase a, the water inlet is opened, supplying fresh water into the sump of the dishwasher; the wash phase may be a main wash phase in a wash cycle comprising the main wash phase, an optional pre-wash phase and one or more rinse phases and a drying phase. During such a filling phase, the conductivity of the fresh water can be measured to obtain a fresh water conductivity reference value, or the fresh water conductivity reference value can be preset in the operating program of the dishwasher.

When the water circulation supplied into the dishwasher is started in phase B, as in the phase for wetting or prewashing the items loaded into the dishwasher, residues which may be present on the washing compartment walls, on the dishwasher interior (for example on the dishwasher basket surface), within the circulation system (i.e. the spray arms, the water supply lines or within a filter screen provided in the dishwasher sump) and which may of course also be present on the items to be cleaned themselves, are entrained into the washing liquid and may thus cause a change in the electrical conductivity, which is shown in fig. 1 as an increase in the electrical conductivity.

In order to obtain a reference value for the conductivity of the washing liquid before the addition of detergent, point m in time during phase C₁A reference measurement is taken here, i.e. during circulation of the washing liquid through the dishwasher, before the addition of detergent is started, but after starting the washing liquid circulation process and a certain amount of time has elapsed (corresponding to phase B in fig. 1) which is required to obtain a substantially constant conductivity value of the washing liquid.

In stage D, detergent is added to the cleaning solutionThis is achieved, for example, by rinsing the detergent container, which can be designed as a detergent compartment, which is closed with a movable lid, which is opened at the beginning of stage D. At a predetermined time after the start of the addition of detergent, said time point being designated m in fig. 1₂The conductivity of the cleaning liquid is measured and compared with at least one and preferably a plurality of predetermined threshold values.

The lower conductivity value a and the upper conductivity value B are shown in fig. 1. If at time m₂Determining that the measured conductivity is above the upper limit value B during the comparison of the measured conductivity value with the threshold levels a and B, it is determined that a fast dissolving detergent, for example a detergent in powder form, has been added to the washing liquid. However, if time m₂Is higher than the lower limit a but does not exceed the upper limit B, it is determined that the detergent added to the washing liquid is a slowly dissolving detergent, for example a detergent in the form of a tablet. If time m₂Is also below the lower limit a, this is considered to indicate that no detergent is added.

Based on the result of this determination, program selection is run and the subsequent stages of the washing cycle are adjusted. For example, if it is determined that no detergent is added, a warning message, for example an optical indication, is given, which informs the user of the dishwasher that no detergent is detected in the washing liquid and that the washing cycle can be adjusted.

An example of how the operation of the dishwasher may be adjusted in the case where it is determined that a slowly dissolving detergent is added will now be described with reference to figure 2. If a slowly dissolving detergent is detected, it is often desirable to select a longer wash program. Accordingly, if a fast dissolving detergent is detected, it is often desirable to select a shorter wash program.

Fig. 2 shows an example of adjusting the operating parameters of the washing program, in particular how the temperature in the washing compartment is adjusted. The curve shown in fig. 2 with a solid line shows the temperature of the washing liquid, which in the initial pre-washing phase is at a relatively low temperature, for example the temperature of a water supply line, which may be a domestic cold water line.Then, during the main washing phase, the washing liquid is heated until a temperature level T is reached₁For example, 40 to 45 deg.c. In the particular example shown in fig. 2, the cleaning liquid is first kept at this temperature and then heated to a higher temperature level T₂Wherein a higher temperature T is reached₂In the meantime, the heating is stopped so that the temperature of the cleaning liquid is again lowered during the time period in which the cleaning liquid is circulated in the dishwasher. When the main wash step is finished, the drain pump is activated to draw a part or all of the washing liquid out of the wash compartment.

Figure 2 shows in dashed lines the adjusted temperature profile when the use of a slowly dissolving detergent was detected. As shown in fig. 2, in this case, the heating of the cleaning liquid is delayed to provide an interval having a substantially constant temperature. In the embodiment illustrated by the dashed curve in fig. 2, in addition to a constant temperature interval at the temperature T1, another constant temperature interval is provided at the temperature T3 which is lower than the temperature T1.

Due to the delay in the heating of the cleaning liquid, the main washing step takes longer to obtain the same cleaning effect than the washing program shown in solid lines in fig. 2. Such extension of the main washing step can be achieved by selectively heating the washing liquid to a higher temperature T₄Compensation is made, as shown in dotted lines in fig. 2, or by using a higher speed circulation pump, i.e. by using a higher water pressure of the water sprayed from the spray arm onto the items to be cleaned.

Alternatively, the extended compensation of the main washing step can also be achieved by shortening subsequent steps, such as rinsing and/or drying steps.

Claims

1. A method of operating a dishwasher, comprising the following successive steps:

(A) adding a detergent to a cleaning liquid circulating within the dishwasher;

(B) measuring the conductivity of the cleaning liquid and determining the rate of change of the conductivity due to dissolution of the cleaning agent in the cleaning liquid;

(C) comparing the rate of change of conductivity to a predetermined threshold to determine the rate of dissolution of the detergent that has been added to the cleaning solution in step (a); and

(D) adjusting the operating parameter based on the determination of step (C).

2. The method of claim 1, wherein the conductivity of the cleaning fluid is measured prior to step (a) to obtain a reference value, the reference value being applied in the determining step of step (B).

3. The method according to any of the preceding claims, further comprising determining a conductivity reference value representative of the conductivity of the fresh water supplied to the dishwasher, and using the conductivity reference value of the fresh water in the determining step of step (B).

4. The method according to claim 3, wherein the reference value for the conductivity of the fresh water is preset in an operating program of the dishwasher.

5. A method according to any one of the preceding claims, wherein in step (B) the conductivity of the cleaning liquid is measured a plurality of times.

6. A method according to any preceding claim, wherein in step (B) the change in conductivity over time is recorded, the slope of the change in conductivity is determined in step (B), and compared to a predetermined threshold slope in step (C).

7. A method according to any preceding claim, wherein a plurality of predetermined threshold values are provided, and wherein in step (C) the rate of change of conductivity is specified as one of a plurality of ranges defined by the predetermined threshold values.

8. The method according to any of the preceding claims, wherein in step (D) the operating parameters of the pre-wash stage, the main wash stage and/or the intermediate wash stage are adjusted.

9. The method according to any one of the preceding claims, wherein the parameters adjusted in step (D) are selected from the following list of parameters:

selection of various program steps;

the duration of the individual program steps; timing of various program steps;

the temperature of the cleaning liquid circulating within the dishwasher; air temperature within the dishwasher;

a fresh water amount supplied into the dishwasher; the speed of the circulation pump; and the speed of the drain pump.

10. The method according to any of the preceding claims, wherein if it is determined in step (C) that the dissolution rate is below the predetermined threshold, a longer program duration is selected in step (D) for a washing step in which the detergent added in step (A) is to be used.

11. The method of claim 10, wherein if a longer program duration is selected in step (D), the heating in the washing step is delayed to provide an interval with a substantially constant temperature.

12. A method according to claim 10 or 11, wherein if a longer program duration is selected in step (D), this extension in duration is at least partly compensated for by:

by shortening the subsequent program steps;

by carrying out the individual procedural steps at higher temperatures; and/or

The various program steps are carried out by using a higher circulation pump speed, wherein the circulation pump is used for circulating the washing liquid within the dishwasher.

13. A method according to any preceding claim, wherein it is determined in step (C) whether a detergent in powder form or a detergent tablet has been added in step (a).

14. The method of claim 13, further comprising predetermining an average detergent tablet dissolution time period required for a detergent tablet to dissolve in the cleaning liquid, and wherein in step (B) the rate of change of conductivity is determined by measuring the conductivity of the cleaning liquid a time after detergent addition that is shorter than the average detergent tablet dissolution time period.

15. The method of claim 14, further comprising predetermining an average detergent powder dissolution time period required for detergent powder to dissolve in the cleaning liquid, and wherein in step (B) the rate of change of conductivity is determined by measuring the conductivity of the cleaning liquid after detergent addition for a time period shorter than the average detergent tablet dissolution time period, but longer than the average detergent powder dissolution time period.

16. The method of claim 14, further comprising predetermining an average detergent powder dissolution time period required for detergent powder to dissolve in the cleaning liquid, and wherein in step (B) the rate of change of conductivity is determined by measuring the conductivity of the cleaning liquid a shorter time after detergent addition than the average detergent powder dissolution time period.