Note: Descriptions are shown in the official language in which they were submitted.
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1 PROCESS FOR OPERATING A DISHWASHER
2 BACKGROUND OF THE INVENTION
3 The invention concerns a process for operating a
4 dishwasher according to the amount of water required and
the temperature gradient in heating the water.
6 When a dishwasher with a wash compartment is operated,
7 usually a wash program with a drying cycle is performed, in
8 which any rinse liquid still adhering to the objects being
9 washed is dried off. To do this, the inherent heat stored
in the objects being washed, which was transferred to the
11 objects when they were washed with hot wash liquid, is used
12 as a heat source during an evaporation cycle.
13 It is also common to turn on a heater during the
14 drying cycle to heat the wash liquid, at least for a time,
as an additional heat source. The evaporated liquid
16 condenses on the walls of the wash compartment, which are
17 cooler than the objects being washed.
18 Dishwashers are also known in which the moist air in
19 the wash compartment is removed by blow drying, and fresh
air is mixed in.
21 All these drying processes are based on a fixed basic
22 setting with a fixed drying time. In some cases, the
23 operator of the dishwasher can choose extra power and/or
24 blow drying.
However, the amount of objects being washed and their
26 composition do not enter into determining the process of
27 the drying cycle. In practice, it has been shown that some
28 dishes with a low specific heat capacity, for example,
29 those made of plastic, are not dried very thoroughly
because of the rigid drying cycle. Dishes with a high
31 specific heat capacity, for example dishes made of
32 earthenware, need only a slight addition of energy for good
33 drying results. The preset drying parameters are based on
34 a standard load, and so there is no adjustment of the
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1 drying cycle when most of the load contains dishes that
2 have a greater of lesser specific heat capacity.
3 German patent application P 195 05 552 proposes
4 determining the amount of water necessary to wet the
objects being rinsed so as to be able to use that value to
6 figure out the surface area of the objects being rinsed.
7 Information can also be obtained on the mass of the objects
8 being rinsed via a value for the gradient of the
9 temperature increase measured.
These variables, the wetting value and the temperature
11 gradient value, which are both indefinite variables in the
12 sense of fuzzy logic, are preferably converted into an
13 approximate degree of wash load using a fuzzy logic
14 control. Individual cycies in the wash program or other
parameters, like for example the spray pressure on the
16 objects being rinsed, are influenced by this degree of
17 load.
18 SUMMARY OF THE INVENTION
19 The invention provides a process for operating a
dishwasher that considers the surface area of objects being
21 washed and their composition during the drying cycle in
22 order to adjust the process to the load in the drying
23 cycle. The parameters of the drying cycle are set
24 depending on the wetting value and the value of the
temperature gradient.
26 By having the parameters for the drying cycle in the
27 dishwasher dependent on the wetting value and the
28 temperature gradient of the objects, the amount of objects
29 and their composition are considered during the drying
cycle in that the process is adjusted to the load in the
31 drying cycle.
32 In one mode of operation according to the invention,
33 conclusions can be drawn on the surface and mass of the
34 objects using a wetting value corresponding to the amount
of water necessary to wet the objects and a value for the
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1 gradient of the temperature increase.
2 Using these two variables, an estimate of the amount
3 of objects and their composition can be made. Thus, for
4 example, a very high wetting value and at the same time a
high gradient for the temperature change suggests a high
6 proportion of plastic dishes. Since they have a low
7 specific heat capacity, the drying time is extended and/or
8 the energy is increased compared to a basic drying cycle,
9 which comes from a standard load, for example. The extra
energy can be achieved with timed heat by extending the
11 turned-on phases and/or increasing the switching frequency
12 of the heater.
13 On the other hand, if a smaller wetting value with a
14 very small gradient for ~he temperature change is detected,
this can show that most of the dishes are made of
16 earthenware. In this case, it may be possible to reduce
17 the drying time, or potentially even do without the extra
18 heating.
19 The invention will be explained in greater detail
below using an example of embodiment.
21 BRIEF DESCRIPTION OF THE DRAWINGS
22 Fig. 1 Shows a basic diagram of an electronic
23 program control of a dishwasher with input variables
24 according to the invention and controlled components and
output variables influenced;
26 Fig. 2 Shows a simplified graph of the fill-level
27 process correlated with time; and
28 Fig. 3 Shows the temperature of two different loads
29 B1 and B2 and a standard load BN in the heat-up phase
correlated with the time.
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1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
2 A dishwasher is provided with a wash compartment (not
3 shown). Referring to Fig. 1, the dishwasher has a sensor
4 TS and a pneumatically switched pressure monitor DW that
senses the fill level of the liquid running in. This
6 pressure monitor DW stops the water feed when the fill
7 amount f~ is sufficient for washing by closing a magnetic
8 valve MV controlling water flow into the wash compartment.
9 Two conditions that are particularly relevant for
saving resources, namely reaching a necessary temperature Tm
11 and fill quantity f~, are detected by an electronic program
12 control EL via the respective sensor device, temperature
13 sensor TS or pressure monitor DW.
14 Exemplary dishwasher loads B1 and B2 are washed in the
dishwasher in two separate wash cycles. The two loads Bl,
16 B2 have approximately the same total surface area, but load
17 B1 has a higher proportion of plastic dishes while load B2
18 contains mostly earthenware. BN represents a standard load
19 with predefined plastic and earthenware proportions and
also approximately the same total surface area as Bl and
21 B2. Using the standard load BN' a basic program for the
22 drying cycle is defined with standard values for wetting
23 value and temperature gradient.
24 The electronic program control EL detects the length
of inlet times ~ t1 and a t2 in each rinse cycle from the
26 fill level time in Fig. 2. Here, ~ t1 is the time from
27 when the water flows in up to the first time the pressure
28 monitor DW is turned on indicating that the water level is
29 sufficient. This time ~ t1 is approximately the same for
all rinse cycles. After the pressure monitor DW is turned
31 on at time tu, water circulation is started.
32 The fill level falls as a result of the liquid that
33 circulates and sticks to the objects being washed in the
34 dishwasher. When a set, decreased fill level fR is reached,
the pressure monitor DW is switched off. Water then flows
36 in again depending on the total surface area of the objects
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1 being washed, which represent a surface to which the
2 circulating liquid can adhere. If the surface area of the
3 objects being washed is large, a lot of li~uid is adhered
4 to the ob;ects, and the fill level in the starting phase of
the circulating cycle falls sharply. The time A t2 for
6 this new water to flow in and balance out the fall in the
7 fill level is thus a variable and depends on the liquid
8 adhered to the surface of the objects being rinsed. In the
9 case of the two loads B1 and B2, if the total surface area
lo of the objects being rinsed is approximately the same, the
11 refill time is approximately equal to ~ t2 in both.
12 The electronic program control EL detects the time
13 difference necessary to heat the rinse liquid to a
14 temperature Tm as another parameter for the load. Fig. 3
shows the temperature over time of the ]oads B1 and B2.
16 The two different temperature curves and heat-up times ~ t3
17 and Q t4 result from the different specific heat capacities
18 of the loads B1 and B2.
19 These two time differences dependent on the load ~ t2
20 and ~ t3 or ~ t4 are input to the electronic program
21 control EL, which preferably contains a fuzzy logic
2 2 control. The amount and type of load is determined using
23 fuzzy logic curves stored in tables.
24 The load B1 with a high proportion of plastic, because
25 of the relatively low inherent heat stored in the objects
26 being washed, requires more drying compared to the standard
27 load BN. The extra drying is accomplished by providing
28 extra energy to the heater Hzg and/or by extending the
29 drying time tT. If ~ t3 and the heat-up time ~ tN dependent
on a st~n~rd load BN deviate sharply from one another, in
31 addition to the measures mentioned above, a blow dryer GT
32 in the dishwasher is activated that does not operate in the
33 basic program for the standard load BN.
34 In the case of load B2 with a high proportion o~
earthenware, the extra energy from the heater ~zg is
36 completely omitted. The high inherent heat stored in the
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1 objects, which is indicated by the long heat-up time ~ t4,
2 is enough by itself for good drying results.
3 The embodiments described herein are exemplary. The
4 invention includes modifications within the scope of the
claims~
