DE102007059516A1 - Method for drying time control in dishwashers - Google Patents

Abstract

Process for controlling the drying time in a dish washer with a rinsing chamber for reception of the material to be dried, where this material is heated to a predetermined starting temperature which is higher than the condensation surface which communicates with the rinsing chamber. The method involves the steps:(a) determination of the temperature course of a characteristic temperature T during drying of the material and (b) detection of a characteristic feature of the extent of water evaporation from the surface of the material on the basis of the temperature course of the characteristic temperature. An independent claim is included for a dish washer with a rinsing chamber for the material to be dried.

Description

The The invention relates to a method according to the preamble of the claim 1.

For one dishwashers are the for the different operations required energy consumption or the time required for it, important performance parameters, not self-sufficient, but closely linked, sometimes even in reverse the sense that minimizing one at the expense of another goes. The last step is usually the washed dishes in the rinsing chamber dried in a drying cycle. There are different procedures for this or principles known.

at one on self-heating based process type leads a heater to heat the interior of the washing chamber, which becomes moisture but not discharged. It increases The temperature of the interior air of the washing chamber, causing an increased relative Humidity can take. A cold surface increases the Drying performance. At her, the moisture from the indoor air condense, whereby the moisture absorption capacity of the inside air obtained or increased becomes.

conventional dishwashers with self-heat drying to lead the dishwasher independently from the load, d. H. the amount and heat capacity of the dishes to be dried, a predetermined (heat) amount of energy to. For the drying cycle is provided for a predetermined, fixed period of time. The amount of heat and the duration is such that even for a large load a sufficient Drying result is achieved. This procedure takes into account a small load is not. Also are in the self-heat drying Moisture sensors can not be used because of the moisture level in the rinsing chamber during the Drying always saturated, probably even oversaturated.

The The object of the present invention consists in a dishwasher to optimize the drying cycle. The optimized drying should economical and be technically easy to implement, especially without it technically elaborate Sensor technology and / or without specially required for drying Get along devices.

The invention is based on a method for regulating a drying time in a dishwasher with a rinsing chamber for receiving items to be washed, in which the item to be washed is heated to a predetermined initial temperature (T ₀ ), which is above the temperature of a condensation surface communicating with the rinsing chamber ,

• (a) Erfassen eines Temperaturverlaufs einer charakteristischen Temperatur (T) während des Trocknens des Spülguts,
• (b) Detektieren eines für den Verdampfungsgrad von Wasser von der Oberfläche des Spülguts (28a, 28b) kennzeichnenden Merkmals anhand des Temperaturverlaufs der charakteristischen Temperatur.

The object of the invention is achieved by the following steps:

• (a) detecting a temperature characteristic of a characteristic temperature (T) during drying of the dishes,
• (b) detecting one for the degree of evaporation of water from the surface of the dishes ( 28a . 28b ) Characteristic feature based on the temperature profile of the characteristic temperature.

The for the Achieving complete drying of the dishes characteristic feature can be achieved or over- or Below a suitably chosen, for complete drying characteristic, critical value, d. H. a threshold of be characteristic temperature (T). The recognition of the characteristic Feature, the recognition of reaching a final temperature or the beginning of an asymptotic behavior of time dependence include the characteristic temperature. That's how achievement can be achieved of the complete Drying recognized and the drying process prematurely, d. H. for example before the end of a programmed drying time, ended and thus saving time.

The Characteristic feature can also achieve a characteristic of complete drying Value of the time derivative of the characteristic temperature be, d. H. a threshold for dT (t) / dt. It can also achieve a characteristic value a temperature difference (ΔT : = T1 - T2) or the time derivative of the temperature difference (d (ΔT) / dt) of two temperatures T1 measured at two different positions and T2, d. H. a threshold for ΔT or for d (ΔT) / dt. The time derivative The temperature signals can be generated by software running in a processor a central control unit is processed, calculated and the Evaluation be provided.

The Detecting such characteristic features of the characteristic Temperature allows an automatic drying detection. By a suitable choice of characteristic temperature and the characteristic feature The automatic drying detection can be independent or largely independent of the (heat- and noise) insulation of scullery environmental conditions such as ambient temperature (e.g. in summer or winter) and the specific installation situation of the Dishwashers (z. B. freestanding or installed in a kitchenette between a right and left neighbor cabinet).

The Method has the advantage that the drying process can be controlled depending on the load can. At a low load so energy can be saved and at a high yet sufficient drying result can be achieved. The optimization is generally in the shutdown of the drying cycle with sufficient drying result. For this is according to the invention only one technically easier and cheaper Temperature sensor with an associated Signal evaluation required. Of course, two or more can used in different positions mounted temperature sensors whose temperature signals to obtain the characteristic Temperature linked together be such as by forming a temperature difference.

at usual Dishwashers is for the Duration of the drying cycle and for its initial temperature in a program flow control respectively one for a predetermined standard loading suitable value for the duration and programmed the start temperature of the drying cycle firmly.

In a further embodiment According to the invention, the dishwasher comprises means for detecting the load or the load. The initial temperature for one Drying cycle with own heat is before the start of the drying cycle depending on the detected Loading determined. For this purpose, a suitable initial temperature and / or one for heating the dishes supplied Amount of heat energy before heating the dishes dependent on be predetermined from the loading. The loading can be, for example by the amount, heat capacity and / or the total surface of the dishes expressed be. Thus, the drying cycle can be optimized depending on the load be, for. B. be abbreviated at a low load.

The characteristic temperature can basically be different places in the dishwasher be detected. You can z. B. a condensation surface characterizing Be temperature. The characteristic temperature can also be a the temperature of the dishes be characteristic temperature.

A Difference temperature can, for example, from the temperature of the wash items characterizing temperature and the temperature of the condensation surface characterizing Temperature are formed. As the temperature of the condensation surface can possibly also a heat storage serve. By evaluating the differential temperature becomes the influence the ambient temperature and / or the installation situation and / or the Influence of the rinsing chamber surrounding heat and noise reduction is reduced or eliminates, whereby the characteristic feature recognized even more reliable can be.

to solution The object mentioned above is also a dishwasher proposed with a rinsing chamber for ware and one with the rinsing chamber in communication condensing surface and means for heating of the dishes in the rinsing chamber.

According to the invention the dishwasher further means for detecting a time dependence (T (t)) of a characteristic Temperature (T) and means for detecting one for the degree the evaporation of water from the surface of the washware characteristic feature the time dependence the characteristic temperature. This can be the actual Be determined at the end of the drying process. It can be also load-dependent determine so that the drying process ends as needed becomes.

When condensing surface For example, the loading door serve. Because the loading door in conventional dishwashers anyway already electronic components and elements of the flow control can there a temperature sensor with low technical Extra effort installed cost-effectively become. The condensation surface is preferably in heat-conducting communication with an element with big Heat capacity, for example with a water temperature controlled to a relatively low temperature. or heat storage. The condensing surface can then one with the rinsing chamber in communication surface of the heat storage be. It changes the temperature of the condensation surface during the heating of the dishes only insignificant, what an effective condensation and therefore drying effect causes. By a big one Heat capacity of the water or heat storage the influence of the ambient temperature (eg summer, winter) or the installation situation (eg proximity to other heat-generating Devices) at least reduced to the characteristic temperature.

The Detection means can be adapted to the time dependence one for the temperature of the condensation surface characterizing temperature and, for example, one with the condensing surface thermally be coupled temperature sensor. Alternatively, the detection means be adapted to the time dependence of one for the temperature of the dishes to detect characteristic temperature, and may, for example one with through the rinsing chamber circulated water be thermally coupled temperature sensor. A suitable place for his Arrangement can be, for example, the pump sump of the machine.

The Detecting means may comprise one or more of the following means: (i) means for detecting the achievement of a final value, (ii) means to recognize the onset of asymptotic behavior as it approaches the final value of the characteristic temperature, (iii) means for Detecting the achievement of a threshold of the time dependence, and / or (iv) means for detecting a threshold value of the derivative after the Time or the time derivative of the time dependence of the characteristic Temperature. These funds can in the form of software modules that evaluate temperature measurement signals of the detection means, will be realized. For this purpose, a central control unit (controller) with be provided with a software programmable processor.

The dishwasher may further comprise means for providing the first derivative after Time of time dependence of the characteristic temperature, and the detecting means may comprise means for detecting the achievement of a final value or the beginning an asymptotic behavior when approaching the final value of temporal Derive the characteristic temperature. alternative It may be means for detecting the achievement of a threshold of time dependency or a threshold of the time derivative of the time dependence include the characteristic temperature. These funds can also be used in the form of software modules running in the processor.

For the calculation a differential temperature can characterize the temperature of the dishes Temperature and the temperature of the condensation surface or the surface temperature characteristic of the temperature memory can be used. For measuring the temperature of the items to be washed, a first temperature sensor in a circulation circuit of the through the rinsing chamber circulated Be arranged in water, for example in a circulating pump. alternative the temperature measurement can be done on a medium in heat exchange with the items to be washed, like the dishes receiving loading basket, or in the washing chamber, z. B. near the receiving place for the Wash ware to be performed. To measure the temperature of the condensation surface, a second temperature sensor in thermal contact with the condensation surface or the surface of the Temperature memory serve. By forming and evaluating a temperature difference can influence the environmental conditions or the installation situation on the control of the drying cycle also reduced or be eliminated.

Further is preferably provided that the washware characterizing temperature and / or one the condensation surface characteristic temperature recorded and evaluated. For this It can also be provided that the different measured values differ weighted before being evaluated.

A embodiment Such a detection and calculation device may, for example in a dishwasher with a heat storage have a first temperature sensor in the memory. A second Sensor can in the washing room and a third in the encore for Detergent in the loading door to be appropriate. From simultaneously recorded values of the second and of the third sensor, the calculation device each forms a ratio value (Quotient), which they get from a simultaneously measured temperature value of the first sensor. For several times recorded within a period results a curve with falling course, which is a temperature as Threshold approaches asymptotically. The threshold symbolizes complete drying. Himself approached the curve up to a certain approximation or reaches the threshold itself, receives the control unit corresponding signal, whereupon it ends the drying process.

The Principle of the invention will be described below with reference to a drawing by way of example explained in more detail. In show the drawings:

1 the time dependence of a temperature during the operations in the washing compartment of a dishwasher with self-heat drying;

2 the time dependence of the temperature in the washing compartment of the dishwasher during the rinse and dry cycle for different loads;

3 a schematic cross section (in side view) of a dishwasher; and

4 a schematic cross section (in front view) of a dishwasher with a temperature storage.

1 shows operations in a dishwasher with self-heat drying according to the prior art. They include a prewash cycle 2 , a first cleaning cycle 4 , a second cleaning cycle 6 , an intermediate rinse 8th , a rinse cycle 10 and a final drying operation 12 , In the pre-wash cycle 2 is fed cold fresh water (about 3.4-3.9 l) and for a preset duration of about 15 min by means of a below the rinsing chamber 14 attached circulation pump 20 through the rinsing chamber 14 (please refer 3 and 4 ) circulated. In the subsequent cleaning cycle 4 detergent is added to the rinsing chamber 14 introduced and added to the pre-rinse led fresh water to an initial cleaning temperature of about 51 ° C during a period of about 13-14 min warmed up. A heating device (not shown) arranged in the hydraulic circuit heats the circulated water to the respectively desired temperature in a single operation. In the subsequent cleaning cycle 6 The heated and provided with detergent water is circulated. The cleaning process 6 forms the main cleaning course for those in the rinsing chamber 14 arranged crockery parts 28 ,

Between the cleaning cycle 6 and the intermediate rinse cycle 8th the rinse water is removed from the rinsing chamber 14 pumped out and fed clean cold fresh water. The fresh water is during the intermediate rinse cycle 8th circulated for a period of about 5 min and thereby heats up by contact with those from the cleaning cycle 6 still warm parts in the rinsing chamber 14 , such as the dishes 28 . 28a . 28b , a loading basket 30 , a water spray rotary arm 24 and the walls of the washing chamber 14 as well as parts in a recirculation cycle 22a . 20 . 22b , To change from the intermediate rinse cycle 8th in the subsequent rinse cycle 10 the intermediate rinse water will come out of the rinse chamber 14 pumped and fed again cold fresh water.

In known dishwashing machines with self-heat drying, the supplied, cold fresh water in the rinse cycle 10 during a predetermined, fixed time, z. B. about 15 minutes, circulated and thereby with a predetermined, fixed heating power to the initial temperature T0 for the final drying process 12 , z. B. to about 65 ° C, heated.

2 illustrates the time course of the temperature or the time dependence of the temperature in the washing chamber for different loads during the rinse cycle 10 and the drying cycle 12 , The in 2 shown temperature be the aforementioned characteristic temperature. You can also do one for the temperature of a part 28a or 28b loading or by means of a first temperature sensor 32 be measured temperature T _{1 of} the circulated water. 2 shows the time course T _n (t) for a defined as normal and a certain amount of crockery and cutlery comprehensive load n and the time course T _n- (t) for a lower than normal loading n-load and the time course T _{+ n} (t) for an assumed as compared to a standard load higher loading of n +. The supply of heating power raises the temperature in the rinsing chamber 14 and thus also the temperature of the dishes 28a . 28b during the rinse cycle 10 essentially proportional to time t. The in 2 The less than proportional increase in temperature that results from the loss of heat transfer, including through the walls of the washing chamber 14 and through the loading door 16 on device parts outside the rinsing chamber 14 , For normal loading, the temperature rises during the rinse cycle 10 in accordance with the mean curve T _n (t) up to a temperature T ₀ , the initial temperature for the subsequent drying cycle 12 , For the lower or higher load n- or n +, the temperature rises more strongly according to the upper curve T _n- (t) or less strongly corresponding to the lower curve T _{n +} (t) for the same supplied heating power up to the corresponding initial temperatures T _{0, n} or T _{0, n +} for the subsequent drying cycle 12 ,

When the heating power is switched off, the drying cycle begins 12 , For the normal loading n, the temperature T (t) changes its course essentially in accordance with a decreasing exponential function. With the decrease of the characteristic temperature T _{n is} the loading dried increasingly, ie on the ware 28a . 28b existing moisture film evaporates and condenses on a cold surface, e.g. B. a cold wall or the inside of the loading door 16 in the rinsing chamber 14 , At a time t _{12, n} , the temporal temperature profile T _n (t) reaches a temperature T _{12, n} , which subsequently only changes insignificantly and marks the achievement of an asymptotic state. This is the moisture film on the items to be washed 28 completely evaporated. The drying cycle 12 for loading n at time t _{12, n} can be ended.

In this example, the temperature profile T _n (t) corresponds to the characteristic feature for the degree of evaporation to be detected. The achievement of the asymptotic state is the characteristic feature for the complete drying of the dishes 28 , By detecting the time course T (t) of the characteristic temperature T, the end of the drying cycle 12 recognized and the drying cycle 12 to be ended. For example, an optical or audible signal for "drying completed" or a device-internal control signal can be generated, after which the drying cycle 12 finished and the dishwasher off and / or in a ready state to open the loading door 16 and clearing the rinsing chamber 14 is offset.

In the example of 2 the temperature T _n- (t) for the lower loading n- drops more steeply or more rapidly at the beginning of the drying cycle than for the normal loading n, and the asymptotic state is at the temperature T _{12, n-} at the time t _{12, n -} reached earlier than for the normal load, because with the lower load n- overall a smaller amount of moisture from the surface of the rinse goods 28 to evaporate. Conversely, for the higher loading n + at the beginning of the drying cycle, the temperature T _{n +} (t) drops less steeply than for the normal loading n, and the asymptotic state is reached at the temperature T _{12, n +} at the time t _{12, n +} later.

By detecting the achievement of the asymptotic state of the temperature history, the complete drying of the washware becomes 28 detected depending on the load. This can be exploited to the drying cycle 12 To finish when complete drying and therefore always depending on the load to achieve a sufficient drying result (complete drying). This optimizes the drying cycle compared to a drying cycle with permanently programmed process parameters (fixed start temperature, fixed drying time). Because at low load, the drying cycle 12 finished earlier than in conventional automatic dishwashers with fixed set drying time.

In the previous description, it has been assumed that the characteristic temperature is a temperature in the rinsing chamber 14 , z. As the temperature of the dishes 28a . 28b is. However, the characteristic temperature can also be another temperature measurement variable, such as. B. in the in the 3 and 4 illustrated embodiments of the invention.

A dishwasher according to 3 includes a rinsing chamber 14 in which the dishes 28 namely plates and cups, in a loading basket 30 is placed, one to the rinsing chamber 14 hinged loading door 16 during the in 1 is closed, one in the rinsing chamber 14 rotatably arranged water spray rotary arm 24 with several spray nozzles 26 one below a bottom wall 19 the rinsing chamber 14 arranged circulation pump 20 , a feed 22a the circulation line, the one pressure outlet side of the circulation pump 20 with the water spray rotary arm 24 connects, a process 22b the circulation line, with a suction side of the circulation pump 20 connected, and a first temperature sensor 32 and a second temperature sensor 34 , each via electrical or optical lines to corresponding temperature sensing devices for evaluating the temperature sensors 34 . 36 generated temperature measuring signals are connected.

The first temperature sensor 32 is in the circulation pump 20 arranged. It is used to measure a temperature T1 or to detect the time dependence T1 (t) of the rinsing eye in the circulation circuit. However, it can also be at other positions in the circulation, such as in the inlet 22a , Procedure 22b or in a depression in the bottom wall of the washing chamber 14 near the opening of the drain 22b be arranged.

The second temperature sensor 34 is in contact with the inside wall, ie the rinsing chamber 14 facing wall of the loading door 16 arranged. It is used for measuring a reference temperature T2 or for detecting the time dependence of the reference temperature T2 (t), which corresponds to the temperature of a cold surface in the rinsing chamber 14 is characteristic. However, it can also be arranged at other positions, such as in a control panel 18 in the loading temperature 16 Where it can easily be connected to the associated temperature reading device with electrical cables already present there.

The temperature T (t) characteristic for detecting a characteristic feature is the difference of the temperatures T1 and T2, ie T (t) = ΔT ₁₂ (t): = T1 (t) - T2 (t). The from the first temperature sensor 32 Temperature T1 of the water measured in the recirculation cycle will drop after the heat output has been switched off at the end of the rinse cycle from the beginning of the drying cycle. The time course T1 (t) can be represented by a curve falling over time with a shape similar to that in FIG 2 shown form. That of the second temperature sensor 34 Temperature T2 measured at the condensing surface increases during the rinse cycle by heat transfer into and through the walls of the rinsing chamber, but slower than temperature T1. After the start of the drying cycle, the temperature T2 continues to rise due to the heat of condensation liberated on the cold surface in the rinsing chamber during the condensation of the water evaporated by the items to be washed. However, this further increase of T2 is weaker than the fall of T1, so that the time course of the temperature difference .DELTA.T ₁₂ (t) = T1 (t) - T2 (t) has an overall decreasing course. The feature characteristic of achieving complete drying of the items to be washed is the undershooting of a suitably selected, critical for complete drying, critical value, ie a threshold value for ΔT ₁₂ .

The dishwasher in 4 includes compared to the in 3 additionally shown a heat storage 38 as a temperature storage, on a side wall of the washing chamber 14 is applied. The heat storage 38 is formed in the shape of a parallel to the side wall of the washing chamber 14 arranged container. It essentially comprises two walls arranged parallel to one another, a feed line 40a with a controllable inlet valve 42 for filling the heat accumulator 38 with water and a drain pipe 40b for emptying the heat storage. As in the embodiment of 3 is a first temperature sensor 32 for measuring a temperature T1 or for detecting the time dependence T1 (t) of the rinsing eye in the circulation circuit. Instead of the second temperature sensor mounted in the loading door 34 (please refer 3 ) is a third temperature sensor 36 in contact with the rinsing chamber 14 facing wall of the heat storage 38 arranged. It is used to measure a reference temperature T3 or to record its time dependence T3 (t), which is the temperature of the water in the heat accumulator 38 is characteristic.

The heat storage 38 is filled at the beginning of the rinse cycle or at the beginning of the drying cycle with compared to the circulating flushing liquid relatively fresh cold water. The temperature T3 in the heat storage 38 rises during the rinse cycle by heat transfer into and through the walls of the wash chamber 14 but slower than the temperature T1. For the increase in temperature T3 from the beginning of the drying cycle, ensures heat, by condensation of the dishes 28a . 28b evaporated water on the cold side wall of the washing chamber 14 becomes free, at the heat storage 38 is applied. The characteristic temperature T (t) for detecting the characteristic feature is the temperature T3 in the heat accumulator, ie T (t) = T3 (t). The feature characteristic for achieving complete drying of the items to be washed is here the exceeding of a suitably selected critical value, which is characteristic for complete drying, ie a threshold value for T3.

A suitable control circuit prevents the loading door 16 during the rinse and dry process 10 and 12 can be opened. As a result, moistening of the items to be washed by recondensation when opening the loading door can be prevented.

2

/ Prewash prewash

4

/ Clean cleaning cycle

6

/ Clean cleaning cycle

8th

/ Rinse between intermediate rinsing

10

/ Rinse rinse cycle

12

/ Dry drying cycle

14

rinsing chamber

16

loading door

18

control panel

19

baseplate

20

circulating pump

22a

Intake the circulation line

22b

procedure the circulation line

24

Water spray rotating arm

26

spray nozzles

28

ware

30

load basket

32

first temperature sensor

34

second temperature sensor

36

third temperature sensor

38

water-tank

40a

supply line

40b

drain line

42

inlet valve

Claims (11)

A method for controlling a drying time in a dishwasher with a wash chamber for receiving items to be washed, wherein the items to be washed is heated to a predetermined initial temperature (T ₀ ), which is above the temperature of a communicating with the washing chamber condensation surface; characterized by the following steps: (a) detecting a temperature characteristic of a characteristic temperature (T) during drying of the dishes, (b) detecting one for the degree of evaporation of water from the surface of the dishes ( 28a . 28b ) Characteristic feature based on the temperature profile of the characteristic temperature. Method according to claim 1, characterized in that that as a feature reaching a final temperature (T (t → ∞)) or the beginning of an asymptotic behavior of time dependence (T (t)) of the characteristic temperature is detected. Method according to one of claims 1 or 2, characterized that for detecting the feature slopes of the temperature profile the characteristic temperature are evaluated. Method according to one of claims 1 to 3, characterized in that the characteristic temperature (T) is a temperature of the items to be washed (T ₁ ) characterizing temperature and / or the condensation surface ( 18 . 36 ) Characteristic temperature (T _2). Method according to one of claims 1 to 5, further comprising measuring a temperature characteristic of the washware temperature and / or detecting the temperature profile (T ₁ (t)) of the temperature of the washware characteristic temperature (T ₁ ). Method according to one of claims 1 to 5, characterized in that the characteristic temperature (T) is the differential temperature (.DELTA.T) between the temperature of the washware characteristic temperature (T ₁ ) and the temperature of the condensation surface characteristic temperature (T ₂ ). Method according to one of claims 4 to 6, characterized in that the dishwasher is a water storage ( 38 ) and that the temperature of the condensation surface characteristic temperature (T ₂ ) a the temperature of the water reservoir ( 38 ) is characteristic temperature (T ₂ = T _WT ). Method according to claim 7, characterized in that a temperature (T ₁ ) characterizing the washware and / or a temperature (T ₂ ) characterizing the condensation surface are detected and evaluated. Dishwashing machine having a wash chamber for items to be washed and a condensation area in communication with the wash chamber and means for heating the wash item in the wash chamber to a predetermined start temperature which is above the temperature of the condensation area, characterized by means for detecting a time dependence (T (t) ) of a characteristic temperature (T), and means for detecting a degree of evaporation of water from the surface of the dishes ( 28a . 28b ) characterizing feature of the temperature characteristic of the characteristic temperature. dishwasher according to claim 9, characterized in that the detection means one or more of the following means comprises: (i) means for recognizing the achievement of a final value, (ii) means for Recognizing the onset of asymptotic behavior as you approach the final value of the characteristic temperature, (iii) means for detecting the achievement of a threshold of the time dependence, and or (iv) means for detecting a threshold value of the derivative the time dependence the characteristic temperature after the time. Dishwasher according to one of claims 9 or 10, characterized in that the means for detecting a time dependence comprise: a first temperature sensor ( 32 ) for detecting the time dependence of the temperature characteristic of the temperature of the washware (T ₁ ) and a second temperature sensor ( 34 ) for detecting the time dependence of the characteristic for the condensation surface temperature (T ₂ ).