U.S. patent application number 12/745697 was filed with the patent office on 2010-09-23 for method for the drying time control in dishwashers.
This patent application is currently assigned to BSH BOSCH UND SIEMENS HAUSGERATE GMBH. Invention is credited to Heinz Heissler, Kai Paintner.
Application Number | 20100236575 12/745697 |
Document ID | / |
Family ID | 40230007 |
Filed Date | 2010-09-23 |
United States Patent
Application |
20100236575 |
Kind Code |
A1 |
Heissler; Heinz ; et
al. |
September 23, 2010 |
METHOD FOR THE DRYING TIME CONTROL IN DISHWASHERS
Abstract
A dishwasher and a method for controlling a drying time in the
dishwasher. The dishwasher may comprise a washing compartment for
receiving items to be washed, wherein the items to be washed are
heated to a defined initial temperature which is above the
temperature of a condensation surface communicating with the
washing compartment. The method of the invention may include
detecting a temperature gradient of a characteristic temperature
during the drying of the items to be cleaned, and using the
temperature gradient of the characteristic temperature to detect a
property that is characteristic of the degree of evaporation of
water on the surface of the items to be cleaned.
Inventors: |
Heissler; Heinz; (Dillingen,
DE) ; Paintner; Kai; (Adelsried, DE) |
Correspondence
Address: |
BSH HOME APPLIANCES CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
100 BOSCH BOULEVARD
NEW BERN
NC
28562
US
|
Assignee: |
BSH BOSCH UND SIEMENS HAUSGERATE
GMBH
Munich
DE
|
Family ID: |
40230007 |
Appl. No.: |
12/745697 |
Filed: |
November 11, 2008 |
PCT Filed: |
November 11, 2008 |
PCT NO: |
PCT/EP2008/065296 |
371 Date: |
June 2, 2010 |
Current U.S.
Class: |
134/18 ;
134/56D |
Current CPC
Class: |
A47L 15/4295 20130101;
A47L 15/48 20130101; A47L 2401/04 20130101; A47L 2501/30 20130101;
A47L 15/0034 20130101 |
Class at
Publication: |
134/18 ;
134/56.D |
International
Class: |
A47L 15/42 20060101
A47L015/42 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2007 |
DE |
10 2007 059 516.8 |
Claims
1-11. (canceled)
12. A method for regulating a drying period in a dishwasher having
a washing compartment for receiving items to be washed, the items
to be washed being heated to a predetermined initial temperature,
which is above a temperature of a condensation surface
communicating with the washing compartment, the method comprising
the steps of: detecting a temperature gradient of a characteristic
temperature during drying of the items to be washed, using the
temperature gradient of the characteristic temperature to detect a
feature that is characteristic of a degree of evaporation of water
from a surface of the items to be washed.
13. The method as claimed in claim 12, wherein reaching of an end
temperature or a start of an asymptotic behavior of a time
dependency of the characteristic temperature is detected as the
feature.
14. The method as claimed in claim 12, wherein rises in the
temperature gradient of the characteristic temperature are
evaluated to detect the feature.
15. The method as claimed in claim 12, wherein the characteristic
temperature is a temperature characteristic of at least one of a
temperature of the items to be washed and a temperature
characteristic of the condensation surface.
16. The method as claimed in claim 12, further comprising at least
one of measuring a temperature characteristic of a temperature of
the items to be washed and detecting a temperature gradient of the
temperature characteristic of the temperature of the items to be
washed.
17. The method as claimed in claim 16, wherein the characteristic
temperature is a differential temperature between the temperature
characteristic of the temperature of the items to be washed and a
temperature characteristic of the temperature of the condensation
surface.
18. The method as claimed in claim 17, wherein the dishwasher
includes a water reservoir and the temperature characteristic of
the temperature of the condensation surface is a temperature
characteristic of the temperature of the water reservoir.
19. The method as claimed in claim 18, wherein at least one of a
temperature characteristic of the items to be washed and a
temperature characteristic of the condensation surface are detected
and evaluated.
20. A dishwasher, comprising: a washing compartment for items to be
washed; a condensation surface communicating with the washing
compartment; a heater for heating the items to be washed in the
washing compartment to a predetermined initial temperature, which
is above a temperature of the condensation surface; means for
detecting a time dependency of a characteristic temperature; and
means for detecting a feature of the temperature gradient of the
characteristic temperature that is characteristic of a degree of
evaporation of water from a surface of the items to be washed.
21. The dishwasher as claimed in claim 20, wherein the detection
means comprise at least one of: means for identifying that an end
value is reached; means for identifying a start of an asymptotic
behavior as an end value of the characteristic temperature is
approached; means for identifying that a threshold of time
dependency is reached; and means for identifying a threshold of a
derivation of the time dependency of the characteristic temperature
according to time.
22. The dishwasher as claimed claim 20, wherein the means for
detecting a time dependency comprise: a first temperature sensor
structured to detect the time dependency of the temperature
characteristic of the temperature of the items to be washed; and a
second temperature sensor structured to detect the time dependency
of the temperature characteristic of the condensation surface.
Description
[0001] The invention relates to a method as claimed in the preamble
of claim 1.
[0002] For an automatic dishwasher the energy consumption required
for the various operations and the time required for these are
important performance parameters, which are not independent but
closely linked, to some extent even conversely in that one is
minimized at the cost of the other. In the last operation the
washed dishes are generally dried in the washing compartment in a
drying operation. Various methods and principles are known for
this.
[0003] In the case of a method type based on inherent heat drying a
heating facility supplies heat to the interior space of the washing
compartment but the moisture is not conducted away. The temperature
of the interior air of the washing compartment rises in this
process, with the result that it can take on an increased relative
air humidity. A cold surface enhances the drying performance. The
moisture from the interior air can condense on it, thereby
maintaining or increasing the capacity of the interior air to
absorb moisture.
[0004] Conventional dishwashers with inherent heat drying supply a
predetermined quantity of (thermal) energy to the washing
compartment regardless of the load, i.e. the quantity and thermal
capacity of the dishes to be dried. A predetermined fixed time
period is provided for the drying operation. The quantity of heat
and the time period are measured so that an adequate drying result
is achieved even for a large load. This method does not take a
small load into account. Also moisture sensors cannot be used with
inherent air drying, as the degree of moisture in the washing
compartment during drying is always saturated, probably even
over-saturated.
[0005] The object of the present invention is to optimize the
drying operation in a dishwasher. It should be possible to achieve
optimized drying economically and in a technically simple manner;
in particular it should be possible without technically complex
sensors and/or without apparatus that is required specifically for
drying.
[0006] The invention is based on a method for regulating a drying
period in a dishwasher having a washing compartment for receiving
items to be washed, the items to be washed being heated to a
predetermined initial temperature (T.sub.0), which is above the
temperature of a condensation surface communicating with the
washing compartment.
[0007] The object of the invention is achieved by the following
steps:
(a) detecting a temperature gradient of a characteristic
temperature (T) during the drying of the items to be washed, (b)
using the temperature gradient of the characteristic temperature to
detect a feature that is characteristic of the degree of
evaporation of water from the surface of the items to be washed
(28a, 28b).
[0008] The feature characteristic of achieving the complete drying
of the items to be washed can be the reaching of or being above or
below an appropriately selected critical value that is
characteristic of complete drying, i.e. a threshold of the
characteristic temperature (T). Identification of the
characteristic feature can include identification of the reaching
of an end temperature or the start of an asymptotic behavior of the
time dependency of the characteristic temperature. It is thus
possible to identify that complete drying has been achieved and to
terminate the drying operation prematurely, i.e. for example before
the end of a programmed drying period, thereby saving time.
[0009] The characteristic feature can also be the reaching of a
value of the temporal derivation of the characteristic temperature
that is characteristic of complete drying, i.e. a threshold for
dT(t)/dt. It can also be the reaching of a characteristic value of
a temperature difference (.DELTA.T:=T1-T2) or the temporal
derivation of the temperature difference (d(.DELTA.T)/dt) between
two temperatures T1 and T2 measured at two different positions,
i.e. a threshold for .DELTA.T or for d(.DELTA.T)/dt. The temporal
derivation of the temperature signals can be calculated and
supplied for evaluation by software processed in a processor of a
central control unit.
[0010] The detection of such characteristic features of the
characteristic temperature allows automatic drying identification.
By selecting the characteristic temperature and the characteristic
features appropriately it is possible for automatic drying
identification to be independent or largely independent of the
(heat and noise) insulation of the washing compartment, ambient
conditions such as the ambient temperature (e.g. in summer and
winter) and the specific installation situation of the automatic
dishwasher (e.g. freestanding or built into a kitchen unit between
adjacent cabinets on the right and left).
[0011] The method has the advantage that the drying operation can
be controlled as a function of load. With a small load it is
therefore possible to save energy and with a larger load an
adequate drying result can still be achieved. Optimization is
generally a matter of terminating the drying operation when the
drying result is adequate. For this just one technically simple and
economical temperature sensor with associated signal evaluation is
required according to the invention. Naturally two or more
temperatures disposed in different positions can also be used,
their temperature signals being linked to obtain the characteristic
temperature, for example by forming a temperature difference.
[0012] With conventional dishwashers a value for the duration and
initial temperature respectively of the drying operation that is
suitable for a predetermined standard load is permanently
programmed in for the duration of the drying operation and its
initial temperature in a program sequence controller.
[0013] In a further embodiment of the invention the dishwasher has
means for detecting the load or the load quantity. The initial
temperature for a drying operation with inherent heat is determined
before the start of the drying operation as a function of the
detected load. A suitable initial temperature and/or a quantity of
thermal energy to be supplied to heat the items to be washed can
also be predetermined as a function of the load before the items to
be washed are heated. The load here can be expressed for example by
the quantity, thermal capacity and/or total surface of the items to
be washed. The drying operation can thus be optimized as a function
of the load, for example being shortened in the case of a smaller
load.
[0014] The characteristic temperature can essentially be detected
at different places in the dishwasher. It can be a temperature
characteristic of the condensation surface for example. The
characteristic temperature can also be a temperature that is
characteristic of the temperature of the items to be washed.
[0015] A differential temperature can be formed for example from
the temperature characteristic of the temperature of the items to
be washed and the temperature characteristic of the temperature of
the condensation surface. The temperature of a thermal reservoir
can optionally also serve as the temperature of the condensation
surface. Evaluating the differential temperature reduces or
eliminates the influence of the ambient temperature and/or the
installation situation and/or the influence of the heat and sound
insulation around the washing compartment, thereby allowing the
characteristic feature to be identified even more reliably.
[0016] To achieve the abovementioned object a dishwasher is also
proposed that has a washing compartment for items to be washed and
a condensation surface communicating with the washing compartment
and also means for heating the items to be washed in the washing
compartment.
[0017] According to the invention the dishwasher also has means for
detecting a time dependency (T(t)) of a characteristic temperature
(T) and means for detecting a feature of the time dependency of the
characteristic temperature that is characteristic of the degree of
evaporation of water from the surface of the items to be washed.
This allows the actual end of the drying operation to be
determined. It can also be determined as a function of load so that
the drying operation is terminated as required.
[0018] The loading door can serve as the condensation surface for
example. Since in the case of conventional dishwashers the loading
door already holds electronic components and elements of the
sequence controller, a temperature sensor can be built in there
economically with little additional technical outlay. The
condensation surface preferably communicates in a thermally
conducting manner with an element of high thermal capacity, for
example with a water or thermal reservoir regulated to a relatively
low temperature. The condensation surface can then be a surface of
the thermal reservoir communicating with the washing compartment.
The temperature of the condensation surface only changes
insignificantly as the items to be washed are heated, bringing
about an effective condensation and therefore also drying effect.
The influence of the ambient temperature (e.g. summer, winter) or
the installation situation (e.g. proximity to other heat-generating
appliances) on the characteristic temperature is at least reduced
due to the high thermal capacity of the water or thermal
reservoir.
[0019] The detection means can be configured to detect the time
dependency of a temperature characteristic of the temperature of
the condensation surface and can for example be a temperature
sensor coupled thermally to the condensation surface. Alternatively
the detection means can be configured to detect the time dependency
of a temperature characteristic of the temperature of the items to
be washed and can for example be a temperature sensor coupled
thermally to water circulated through the washing compartment. An
appropriate location for this can be the pump sump of the automatic
machine for example.
[0020] The detection means can comprise one or more of the
following means: (i) means for identifying that an end value is
reached, (ii) means for identifying the start of an asymptotic
behavior as the end value of the characteristic temperature is
approached, (iii) means for identifying that a threshold of time
dependency is reached and/or (iv) means for identifying a threshold
of the derivation according to time or the temporal derivation of
the time dependency of the characteristic temperature. These means
can be implemented in the form of software modules, which evaluate
temperature measurement signals of the detection means. A central
controller can also be provided with a processor that can be
programmed using software.
[0021] The dishwasher can also have means for supplying the first
derivation according to time of the time dependency of the
characteristic temperature and the detection means can have means
for identifying that an end value is reached or the start of an
asymptotic behavior as the end value of the temporal derivation of
the characteristic temperature is approached. Alternatively it can
have means for identifying that a threshold of time dependency or a
threshold of the temporal derivation of the time dependency of the
characteristic temperature has been reached. These means can also
be provided in the form of software modules executed in the
processor.
[0022] It is possible to use the temperature characteristic of the
temperature of the items to be washed and the temperature
characteristic of the temperature of the condensation surface or
the surface of the temperature reservoir to calculate a
differential temperature. To measure the temperature of the items
to be washed a first temperature sensor can be disposed in a
circulation circuit of the water circulated through the washing
compartment, for example in a circulation pump. Alternatively the
temperature measurement can be carried out on a medium that
exchanges heat with the items to be washed, for example the basket
holding the items to be washed, or in the washing compartment, e.g.
in proximity to the receiving site for the items to be washed. To
measure the temperature of the condensation surface it is possible
to use a second temperature sensor in thermal contact with the
condensation surface or the surface of the temperature reservoir.
By forming and evaluating a temperature difference it is also
possible to reduce or eliminate the influence of the ambient
conditions or the installation situation on the control of the
drying operation.
[0023] Provision is also preferably made for a temperature
characteristic of the items to be washed and/or a temperature
characteristic of the condensation surface to be detected and
evaluated. To this end provision can also be made for the various
measured values to be weighted differently before they are
evaluated.
[0024] In a dishwasher with a thermal reservoir for example one
embodiment of such a detection and calculation facility can have a
first temperature sensor in the reservoir. A second sensor can be
disposed in the washing compartment and a third in the detergent
dispenser in the loading door. The calculation facility in each
instance forms a ratio value (quotient) from simultaneously
detected values of the second and third sensors and subtracts this
from a simultaneously measured temperature value of the first
sensor. A curve with a falling gradient, which approximates
asymptotically to a temperature as a threshold, results for a
number of time points detected within a time interval. The
threshold symbolizes complete drying. If the curve has approximated
to this up to a certain approximation sum or even reaches the
threshold, the control unit receives a corresponding signal,
whereupon it terminates the drying operation.
[0025] The principle of the invention is described in more detail
below by way of example with reference to a drawing, in which:
[0026] FIG. 1 shows the time dependency of a temperature during the
operations in the washing compartment of a dishwasher with inherent
heat drying;
[0027] FIG. 2 shows the time dependency of the temperature in the
washing compartment of the dishwasher during the final rinse and
drying operations for different loads;
[0028] FIG. 3 shows a schematic cross section (side view) of a
dishwasher; and
[0029] FIG. 4 shows a schematic cross section (front view) of a
dishwasher with a temperature reservoir.
[0030] FIG. 1 shows operations in a dishwasher with inherent heat
drying according to the prior art. They comprise a prewash
operation 2, a first cleaning operation 4, a second cleaning
operation 6, an intermediate rinse operation 8, a final rinse
operation 10 and a drying operation 12 that completes the
operations. In the prewash operation 2 cold fresh water (approx.
3.4-3.9 l) is fed in and circulated through the washing compartment
14 (see FIGS. 3 and 4) for a preset period of approx. 15 mins by
means of a circulation pump 20 disposed below the washing
compartment 14. In the subsequent cleaning operation 4 detergent is
introduced into the washing compartment 14 and the fresh water fed
in for the prewash is heated to an initial cleaning temperature of
approx. 51.degree. C. for a period of approx. 13-14 mins. A heating
apparatus (not shown) disposed in the hydraulic circuit heats the
circulated water to the temperature desired in each instance in an
operation. In the subsequent cleaning operation 6 the heated water,
now provided with detergent, is circulated. The cleaning operation
6 represents the main cleaning operation for the dishes 28 disposed
in the washing compartment 14.
[0031] Between the cleaning operation 6 and the intermediate rinse
operation 8 the washing water is pumped out of the washing
compartment 14 and clean fresh water is fed in. The fresh water is
circulated for a period of approx. 5 mins during the intermediate
rinse operation 8 and is heated in the process by contact with the
elements in the washing compartment 14 that are still warm from the
cleaning operation 6, for example the items to be washed 28, 28a,
28b, a basket 30, a water spray rotating arm 24 and the walls of
the washing compartment 14 as well as elements in a circulation
circuit 22a, 20, 22b. To switch from the intermediate rinse
operation 8 to the subsequent final rinse operation 10 the
intermediate rinse water is pumped out of the washing compartment
14 and cold fresh water is fed in again.
[0032] In known dishwashers with inherent heat drying the cold
fresh water fed in is circulated for a predetermined fixed time,
e.g. approx. 15 mins, in the final rinse operation 10 and in this
process heated with a predetermined fixed heat output to the
initial temperature T0 for the final drying operation 12, e.g. to
approx. 65.degree. C.
[0033] FIG. 2 shows the gradient of temperature over time or the
time dependency of the temperature in the washing compartment for
different loads during the final rinse operation 10 and the drying
operation 12. The temperature shown in FIG. 2 can be the
abovementioned characteristic temperature here. It can also be a
temperature T.sub.1 of the circulated water measured for the
temperature of a part 28a or 28b of the load or measured by means
of a first temperature sensor 32. FIG. 2 shows the gradient over
time T.sub.n(t) for a load n defined as standard and comprising a
specified quantity of dishes and cutlery as well as the gradient
over time T.sub.n-(t) for a smaller load n-than the standard load
and the gradient over time T.sub.n+(t) for a larger load n+ than an
accepted standard load. The heat output supplied raises the
temperature in the washing compartment 14 and therefore also the
temperature of the items to be washed 28a, 28b during the final
rinse operation 10 essentially in proportional to the time t. The
temperature rise shown in FIG. 2, which is less than proportional,
is due to heat transfer loss, for example through the walls of the
washing compartment 14 and through the loading door 16 to elements
of the appliance outside the washing compartment 14. For the
standard load n the temperature rises during the final rinse
operation 10 according to the middle curve T.sub.n(t) up to a
temperature T.sub.0, the initial temperature for the temporally
subsequent drying operation 12. For the smaller and larger loads n-
and n+ with the same supplied heat output the temperature rises
more according to the upper curve T.sub.n-(t) and less according to
the lower curve T.sub.n+(t) up to the corresponding initial
temperatures T.sub.0,n- and T.sub.0,n+ for the subsequent drying
operation 12.
[0034] The drying operation 12 starts when the heat output is
deactivated. For the standard load n the temperature T.sub.n(t)
changes its gradient essentially according to a falling exponential
function. As the characteristic temperature T.sub.n decreases, the
load dries increasingly, in other words a film of moisture on the
items to be washed 28a, 28b evaporates and condenses on a cold
surface, e.g. a cold wall or the inside of the loading door 16 in
the washing compartment 14. At a time t.sub.12,n the gradient of
temperature over time T.sub.n(t) reaches a temperature T.sub.12,n,
which then only changes insignificantly and marks the reaching of
an asymptotic state. The film of moisture on the items to be washed
28 is then completely evaporated. The drying operation 12 for the
load n can be terminated at time t.sub.12,n.
[0035] In this example the temperature gradient T.sub.n(t)
corresponds to the characteristic feature to be detected for the
degree of evaporation. The reaching of the asymptotic state is the
characteristic feature of complete drying of the items to be washed
28. By detecting the gradient T(t) of the characteristic
temperature T over time it is possible to identify the end of the
drying operation 12 and terminate the drying operation 12. It is
possible for example to generate a visual or acoustic signal for
"Drying terminated" or even a control signal internal to the
appliance, whereupon the drying operation 12 is terminated and the
automatic dishwasher is turned off and/or switched to a ready state
for opening the loading door 16 and emptying the washing
compartment 14.
[0036] In the example in FIG. 2 the temperature T.sub.n-(t) for the
smaller load n-drops more steeply or quickly at the start of the
drying operation than for the standard load n and the asymptotic
state is reached earlier at the temperature T.sub.12,n- at time
t.sub.12,n- than for the standard load, because overall there is a
smaller quantity of moisture to be evaporated from the surface of
the items to be washed 28. Conversely the temperature T.sub.n+(t)
for the larger load n+ drops less steeply at the start of the
drying operation than for the standard load n and the asymptotic
state is reached later at the temperature T.sub.12,n+ at time
t.sub.12,n+.
[0037] The complete drying of the items to be washed 28 as a
function of the load is identified by detecting the reaching of the
asymptotic state of the temperature gradient. This can be used to
terminate the drying operation 12 when complete drying has been
achieved and thus always to achieve an adequate drying result
(complete drying) as a function of the load. The drying operation
is therefore optimized compared with a drying operation with
permanently programmed sequence parameters (fixed initial
temperature, fixed drying time), as the drying operation 12 can be
terminated earlier for a smaller load than it can with conventional
automatic dishwashers with a permanently set drying period.
[0038] In the description above it has been assumed that the
characteristic temperature is a temperature in the washing
compartment 14, e.g. the temperature of the items to be washed 28a,
28b. The characteristic temperature can however also be another
measured temperature variable, as in the embodiments of the
invention illustrated in FIGS. 3 and 4.
[0039] A dishwasher according to FIG. 3 comprises a washing
compartment 14, in which the items to be washed 28, specifically
plates and cups, are placed in a basket 30, a loading door 16
hinged to the washing compartment 14, which is closed during the
operations shown in FIG. 1, a water spray rotating arm 24 with a
number of spray nozzles 26 which is disposed in a rotatable manner
in the washing compartment 14, a circulation pump 20 disposed below
a base wall 19 of the washing compartment 14, an inlet 22a of the
circulation line, which connects a pressure output side of the
circulation pump 20 to the water spray rotating arm 24, an outlet
22b of the circulation line, which is connected to an intake side
of the circulation pump 20, and a first temperature sensor 32 and a
second temperature sensor 34, each connected by way of electrical
or optical lines to corresponding temperature readout apparatuses
for evaluating the temperature measurement signals generated by the
temperature sensors 34, 36.
[0040] The first temperature sensor 32 is disposed in the
circulation pump 20. It serves to measure a temperature T1 or to
detect the time dependency T1(t) of the washing liquor in the
circulation circuit. It can however also be disposed at different
positions in the circulation circuit, for example in the inlet 22a,
outlet 22b or in a depression in the base wall of the washing
compartment 14 in proximity to the opening of the outlet 22b.
[0041] The second temperature sensor 34 is disposed in contact with
the inner wall, i.e. the wall of the loading door 16 facing the
washing compartment 14. It serves to measure a reference
temperature T2 or to detect the time dependency of the reference
temperature T2(t), which is characteristic of the temperature of a
cold surface in the washing compartment 14. It can however also be
disposed in different positions, for example in a control panel 18
in the loading temperature 16, where it can easily be connected to
the associated temperature readout apparatus by means of electric
cables that are present there anyway.
[0042] The characteristic temperature T(t) for detecting a
characteristic feature is the difference between the temperatures
T1 and T2, i.e. T(t)=.DELTA.T.sub.12(t):=T1(t)-T2(t). The
temperature T1 of the water measured by the first temperature
sensor 32 in the circulation circuit will drop after the heat
output is deactivated at the end of the final rinse operation from
the start of the drying operation. The gradient over time T1(t) can
be illustrated by a curve that drops over the course of time with a
form similar to the form shown in FIG. 2. The temperature T2
measured by the second temperature sensor 34 at the condensation
surface rises during the final rinse operation due to heat transfer
into and through the walls of the washing compartment, but more
slowly than the temperature T1. After the start of the drying
operation the temperature T2 continues to rise due to the
condensation heat released during condensation of the water
evaporated from the items to be washed at the cold surface in the
washing compartment. This further rise of T2 is however smaller
than the drop of T1, so the gradient over time of the temperature
difference .DELTA.T.sub.12(t)=T1(t)-T2(t) generally has a falling
gradient. The feature characteristic of the achievement of complete
drying of the items to be washed is the falling below an
approximately selected critical value characteristic of complete
drying, i.e. a threshold for .DELTA.T.sub.12.
[0043] Unlike the dishwasher illustrated in FIG. 3 the dishwasher
in FIG. 4 also has a thermal reservoir 38 as a temperature
reservoir, which is located on a side wall of the washing
compartment 14. The thermal reservoir 38 is configured in the form
of a vessel disposed parallel to the side wall of the washing
compartment 14. It essentially comprises two walls disposed
parallel to each other, a supply line 40a with a controllable inlet
valve 42 for filling the thermal reservoir 38 with water and an
outlet line 40b for emptying the thermal reservoir. As with the
embodiment in FIG. 3 a first temperature sensor 32 for measuring a
temperature T1 or for detecting the time dependency T1(t) of the
washing liquor is disposed in the circulation circuit. Instead of
the second temperature sensor 34 located in the loading door (see
FIG. 3) a third temperature sensor 36 is disposed in contact with
the wall of the thermal reservoir 38 facing the washing compartment
14. It serves to measure a reference temperature T3 or to detect
its time dependency T3(t), which is characteristic of the
temperature of the water in the thermal reservoir 38.
[0044] At the start of the final rinse operation or at the start of
the drying operation the thermal reservoir 38 is filled with
relatively cold fresh water compared with the circulated washing
liquor. The temperature T3 in the thermal reservoir 38 rises during
the final rinse operation due to heat transfer into and through the
walls of the washing compartment 14, but more slowly than the
temperature T1. The rise in the temperature T3 from the start of
the drying operation is produced by heat released by condensation
of the water evaporated from the items to be washed 28a, 28b on the
cold side wall of the washing compartment 14, adjacent to which the
thermal reservoir 38 is located. The characteristic temperature
T(t) for detecting the characteristic feature is the temperature T3
in the thermal reservoir, i.e. T(t)=T3(t). The characteristic
feature for achieving complete drying of the items to be washed
here is the exceeding of an appropriately selected critical value
characteristic of complete drying, i.e. a threshold for T3.
[0045] A suitable control circuit makes it impossible to open the
loading door 16 during the final rinse and drying operations 10 and
12. This makes it possible to prevent the items to be washed being
wet due to back condensation when the loading door is opened.
LIST OF REFERENCE CHARACTERS
[0046] 2 Prewash operation/prewashing [0047] 4 Cleaning
operation/cleaning [0048] 6 Cleaning operation/cleaning [0049] 8
Intermediate rinse operation/intermediate rinsing [0050] 10 Final
rinse operation/final rinsing [0051] 12 Drying operation/drying
[0052] 14 Washing compartment [0053] 16 Loading door [0054] 18
Control panel [0055] 19 Base plate [0056] 20 Circulation pump
[0057] 22a Inlet of circulation line [0058] 22b Outlet of
circulation line [0059] 24 Water spray rotating arm [0060] 26 Spray
nozzles [0061] 28 Items to be washed [0062] 30 Basket [0063] 32
First temperature sensor [0064] 34 Second temperature sensor [0065]
36 Third temperature sensor [0066] 38 Water reservoir [0067] 40a
Supply line [0068] 40b Outlet line [0069] 42 Inlet valve
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