[0001] The present invention relates to a method for controlling a drying cycle of a laundry
dryer in dependence of the amount of load inside a laundry drum. Further, the present
invention relates to a corresponding laundry dryer.
[0002] Often the full capacity of a laundry drum in a laundry dryer is not exploited. It
is not unusual that only about the half of the maximum load capacity is loaded in
the laundry drum of the laundry dryer. Thus, it would be advantageous to adapt the
drying cycle of the laundry dryer to the reduced load inside the laundry drum in order
to avoid consumption of energy, which is not required, and/or to reduce drying cycle
time.
[0003] It is an object of the present invention to provide a method for controlling a drying
cycle of a laundry dryer in dependence of the amount of load inside a laundry drum,
wherein said method maximises the performance of the machine. It is further an object
of the present invention to provide a corresponding laundry dryer.
[0004] The object of the present invention is achieved by the method according to claim
1.
[0005] The method according to the present invention is provided for controlling a drying
cycle of a laundry dryer in dependence of the amount of load inside a laundry drum,
comprising the steps of:
- detecting an electric resistance and/or an electric conductivity between two or more
electrodes (12, 14) at least partly contacting the laundry inside the laundry drum
(16) and,
- estimating the amount of load inside the laundry drum (16) by evaluating the noise
and/or fluctuation of the detected electric resistance and/or conductivity, and
- controlling a rotation speed (v) of a drying air stream fan (30) for conveying a drying
air stream through the laundry drum (16) in response to the estimated amount of load
inside the laundry drum (16), wherein the rotation speed (v) of the drying air stream
fan increases with a decreasing amount of load in the laundry drum (16).
[0006] One aspect of the present invention bases on the fact that it has been found a correlation
between the electric signal and the amount of load in the laundry drum. Another aspect
of the present invention is that the rotation speed of an drying air stream fan for
conveying a drying air stream through the laundry drum is made dependent on the amount
of load inside the laundry to improve the drying performances of the laundry dryer.
Particularly, the rotation speed of the drying air stream fan increases with a decreasing
amount of load in the laundry drum.
[0007] In particular, noise and/or fluctuations of a electric signal corresponding to the
electric resistance and/or an electric conductivity between the electrodes are used
for estimating the amount of load in the laundry drum.
[0008] It has been found that the value of peaks, and/or the number of peaks within a time
span and/or the area subtended by peaks of an electric signal corresponding to the
detected electric resistance and/or conductivity is/are related to the amount of laundry
load inside the laundry drum.
[0009] For example the number of peaks within a time span of said electric signal increases
with a decreasing amount of load in said laundry drum. The smaller is the load inside
the laundry drum, the higher is the number or frequency of the detected peaks, and
the higher is an electrical noise measured by the conductimetric system.
[0010] Further, it has been found that the area subtended by peaks of an electric signal
corresponding to the detected electric resistance and/or conductivity increases with
a decreasing amount of load in said laundry drum and similarly the value of peaks
of an electric signal corresponding to the detected electric resistance and/or conductivity
increases with a decreasing amount of load in said laundry drum
[0011] Evaluating the noise and/or fluctuation of the detected electric resistance and/or
conductivity comprises:
- measuring the value of peaks of an electric signal corresponding to the detected electric
resistance and/or conductivity, and/or
- measuring the number of peaks within a time span of an electric signal corresponding
to the detected electric resistance and/or conductivity, and/or
- measuring the area subtended by peaks of an electric signal corresponding to the detected
electric resistance and/or conductivity.
[0012] Preferably, the rotation speed of the drying air stream fan increases when the estimated
amount of load inside the laundry drum is above a predetermined threshold.
[0013] Preferably, a rotation speed of the laundry drum is controlled, wherein the rotation
speed of the laundry drum is proportional to the rotation speed of the drying air
stream fan. In this case, only one motor is required for the drying air stream fan
and the laundry drum.
[0014] Further, the electric resistance and/or electric conductivity between the electrodes
may be detected within a predetermined time interval at the beginning of the drying
cycle after the laundry starts to rotate
[0015] For example, the time interval takes between two minutes and ten minutes, in particular
five minutes.
[0016] In particular, before the amount of load inside the laundry drum has been estimated,
the drying air stream fan is driven with an average rotation speed.
[0017] According to one embodiment, the drying air stream fan is activated with a constant
rotation speed, after the amount of load inside the laundry drum has been estimated.
Alternatively, the drying air stream fan is activated with a rotation speed oscillating
around a mean value, after the amount of load inside the laundry drum has been estimated,
wherein said mean value depends on the amount of load inside the laundry drum.
[0018] According to a further embodiment, the drying air stream fan and the laundry drum
change periodically the sense of rotation, after the amount of load inside the laundry
drum has been estimated.
[0019] Preferably, the method includes the step of controlling the speed of a heat pump
compressor motor of the laundry dryer, wherein the speed of the heat pump compressor
motor increases in response to an increasing of the rotation speed of the drying air
stream fan.
[0020] The object of the present invention is further achieved by the laundry dryer according
to claim 12.
[0021] A laundry dryer of the present invention comprises a laundry drum, a drying air stream
fan for conveying a drying air stream through the laundry drum and
- at least two electrodes provided for detecting an electric resistance and/or an electric
conductivity of the laundry inside the laundry drum,
- a control unit is provided for estimating the amount of load inside the laundry drum
by evaluating electric resistance and/or an electric conductivity, wherein
- the control unit is provided for controlling a rotation speed of the drying air stream
fan in response to the estimated amount of load inside the laundry drum, and wherein
- the control unit is adapted to drive the drying air stream fan to a first rotation
speed corresponding with a first amount of load in the laundry drum and to a second
rotation speed corresponding with a second amount of load in said laundry drum, wherein
the first rotation speed is higher than the second rotation speed and the first amount
is smaller than the second amount.
[0022] The laundry dryer of the present invention uses the fact that it has been found a
correlation between the electric signal and the amount of load in the laundry drum.
Another aspect of the laundry dryer of the present invention is that the rotation
speed of an drying air stream fan for conveying an air stream through the laundry
drum is made dependent on the amount of load inside the laundry to increase the drying
performance of the laundry dryer. A higher rotation speed corresponds with the smaller
amount of load and a lower rotation speed corresponds with the bigger amount of load
in the laundry drum.
[0023] In particular, noise and/or fluctuations of the electric signal are used for estimating
the amount of load in the laundry drum, wherein the frequency of the electric signal
and/or the number of peaks within a time span of said electric signal increases with
a decreasing amount of load in said laundry drum. The smaller is the load inside the
laundry drum, the higher is the number or frequency of the detected peaks, and the
higher is an electrical noise measured by the conductimetric system.
[0024] Further, it has been found that the area subtended by peaks of an electric signal
corresponding to the detected electric resistance and/or conductivity increases with
a decreasing amount of load in said laundry drum and similarly the value of peaks
of an electric signal corresponding to the detected electric resistance and/or conductivity
increases with a decreasing amount of load in said laundry drum
[0025] Preferably, the control unit is provided for controlling the rotation speed of the
laundry drum.
[0026] Preferably a single motor is provided for driving into rotation both the laundry
drum and the drying air stream fan.
[0027] Preferably a first motor is provide for driving into rotation the laundry drum and
a second motor independent from the first motor is provided for driving into rotation
the drying air stream fan.
[0028] In particular, the electrodes are arranged at a rear side of a front frame of the
laundry dryer and at an opening of said laundry dryer.
[0029] For example, the electrodes are elongated and arranged in parallel.
[0030] According to a preferred embodiment of the present invention, the laundry dryer comprises
a heat pump system. In this case, additionally the rotation speed of a compressor
motor of said heat pump system may be controlled by the control unit so that the control
unit is adapted to increase the rotation speed of the compressor motor in response
to the rotation speed variation of the drying air stream fan.
[0031] Alternatively, the laundry dryer may comprise an air-to-air heat exchanger thermally
connected to an air stream circuit of the laundry dryer.
[0032] At last, the laundry dryer is provided for the method for controlling a drying cycle
mentioned above.
[0033] The novel and inventive features believed to be the characteristic of the present
invention are set forth in the appended claims.
[0034] The invention will be described in further detail with reference to the drawings,
in which
- FIG 1
- illustrates a schematic sectional side view of a laundry dryer with two electrodes
according to a preferred embodiment of the present invention,
- FIG 2
- illustrates a detailed sectional side view of the electrodes of the laundry dryer
according to the preferred embodiment of the present invention,
- FIG 3
- illustrates a schematic perspective rear view of a front frame of the laundry dryer
with the electrodes according to the preferred embodiment of the present invention,
- FIG 4
- illustrates a schematic diagram of a first embodiment of the laundry dryer with a
heat pump system according to the present invention,
- FIG 5
- illustrates a schematic diagram of a second embodiment of the laundry dryer with the
heat pump system according to the present invention,
- FIG 6
- illustrates a schematic diagram of a first embodiment of the laundry dryer with an
air-to-air condenser according to the present invention,
- FIG 7
- illustrates a schematic diagram of a second embodiment of the laundry dryer with the
air-to-air condenser according to the present invention,
- FIG 8
- illustrates three diagrams of rotation speeds of an drying air stream fan as function
of the time according to a first example of the present invention,
- FIG 9
- illustrates three diagrams of rotation speeds of the drying air stream fan as function
of the time according to a second example of the present invention,
- FIG 10
- illustrates a diagram of the rotation speed of the drying air stream as function of
the time according to a third example of the present invention,
- FIG 11
- illustrates a diagram of the rotation speed of the drying air stream fan as function
of the time according to a fourth example of the present invention, and
- FIG 12
- illustrates a diagram of the rotation speed of the drying air stream fan as function
of the time according to a fifth example of the present invention.
[0035] FIG 1 illustrates a schematic sectional side view of a laundry dryer 10 with two
electrodes 12 and 14 according to a preferred embodiment of the present invention.
The laundry dryer 10 includes a laundry drum 16, a front door 18 and a front frame
20. A front free end 17 of the laundry drum 16 is rotatably connected to a rear side
of the front frame 20 via a sealing member 21 interposed between the front free end
17 of the laundry drum 16 and the rear side of the front frame 20 as shown in figure
2.
[0036] The electrodes 12 and 14 are attached at the rear side of the front frame 20. Further,
the electrodes 12 and 14 are arranged at a lower portion of a laundry loading front
opening of the laundry drum 12 and below the front door 18. A first electrode 12 is
arranged above a second electrode 14.
[0037] FIG 2 illustrates a detailed sectional side view of the electrodes 12 and 14 of the
laundry dryer 10 according to the preferred embodiment of the present invention. FIG
2 shows that the distance between the electrodes 12 and 14 is relative small.
[0038] FIG 3 illustrates a schematic perspective rear view of a front frame 20 of the laundry
dryer with the electrodes 12 and 14 according to the preferred embodiment of the present
invention. The electrodes 12 and 14 are elongated and arranged in parallel to each
other. The electrodes 12 and 14 extend substantially horizontally.
[0039] The electrodes 12 and 14 are parts of a conductimetric system. Said conductimetric
system is provided for detecting the dryness degree of the laundry inside the drum
and for estimating the amount of load in the laundry drum 16. For this purpose a level
of electrical noise and/or fluctuation during the first minutes of a drying cycle
is used. The wet load can connect electrically the first electrode 12 to the second
electrode 14, when a part of the wet load touches simultaneously the first electrode
12 and the second electrode 14. If the wet load in the laundry drum 16 does not touch
simultaneously the first electrode 12 and the second electrode 14, then a peak is
detected by the conductimetric system.
[0040] It has been found that there is a correlation between the number or frequency of
peaks of the electric signal and the amount of load in the laundry drum 16. The smaller
the load is inside the laundry drum 16, the higher is the number or frequency of the
detected peaks, and the higher is an electrical noise measured by the conductimetric
system. Further, it has been found that also the value of peaks of an electric signal
corresponding to the detected electric resistance and/or conductivity, and also the
area subtended by peaks of an electric signal corresponding to the detected electric
resistance and/or conductivity are related to the amount of load inside the laundry
drum 16.
[0041] FIG 4 illustrates a schematic diagram of a first embodiment of the laundry dryer
10 with a heat pump system according to the present invention.
[0042] The heat pump system comprises an air stream circuit 22, preferably closed, and a
closed refrigerant circuit 24. The air stream circuit is formed by the laundry drum
16, an evaporator or gas heater 26, a condenser or gas cooler 28 and a drying air
stream fan 30. The refrigerant circuit 24 is formed by a compressor 32, the condenser
28, an expansion device 34 and the evaporator 26. For example, the expansion device
34 is an expansion valve. The evaporator 26 and the condenser 28 are heat exchangers
and form the thermal interconnections between the air stream circuit 22 and the refrigerant
circuit 24.
[0043] Further, the heat pump system comprises a motor 36 and a control unit 40. The motor
36 is connected to the control unit 40 by a motor control line 44. The drying air
stream fan 30 and the laundry drum 16 are driven by the motor 36. The first electrode
12 and the second electrode 14 are arranged inside the laundry drum 16. The first
electrode 12 and the second electrode 14 are connected to the control unit 40 by a
detection line 42. The first electrode 12, the second electrode 14, the detection
line 42 and the control unit 40 form the conductimetric system.
[0044] In the air stream circuit 22, the evaporator 26 cools down and dehumidifies an air
stream, after the air stream has passed the laundry drum 16. Then, the condenser 28
heats up the air stream, before the air stream is re-inserted into the laundry drum
16 again. The air stream is driven by the drying air stream fan 30 arranged preferably
but not necessarily between the condenser 28 and laundry drum 16. In the refrigerant
circuit 24, a refrigerant is compressed and heated up by the compressor 32, cooled
down and condensed in the condenser 28, expanded in the expansion device 34 and then
vaporised in the evaporator 26.
[0045] The first electrode 12, the second electrode 14, the detection line 42 and the control
unit 40 form the conductimetric system for estimating the amount of load inside the
laundry drum 16. In dependence of the amount of the load the rotation speed of the
motor 36 and thereby the rotation speed of the drying air stream fan 30 and the laundry
drum 16 are controlled by the control unit 40. The rotation speed of the drying air
stream fan 30 is proportional to the rotation speed of the laundry drum 16. For example,
the air stream drying 30 is directly driven by the motor 36, while the laundry drum
16 is indirectly driven by the motor 36 via a belt-pulley system. If the conductimetric
system estimates a reduced load in the laundry drum 16, which is lower than the maximum
load of said laundry drum 16, then the control unit sets the motor 36 and thereby
the drying air stream fan 30 and the laundry drum 16 to a rotation speed higher than
the rotation speed for the maximum load. Preferably, the estimation of the load in
the laundry drum 16 is performed during the first few minutes of the drying cycle,
for example during the first five minutes.
[0046] FIG 5 illustrates a schematic diagram of a second embodiment of the laundry dryer
10 with the heat pump system according to the present invention.
[0047] The heat pump system for the laundry dryer 10 of the second embodiment comprises
substantially the same components as the first embodiment. Instead of the motor 36
for driving the drying air stream fan 30 and the laundry drum 16, the second embodiment
comprises a fan motor 37 for driving the drying air stream fan 30 and a drum motor
38 for driving the laundry drum 16. Instead of the motor control line 44, the second
embodiment comprises a fan control line 45 and a drum control line 46. The fan control
line 45 connects the control unit 40 to the fan motor 37. In a similar way, the drum
control line 46 connects the control unit 40 to the drum motor 38.
[0048] The conductimetric system includes the first electrode 12, the second electrode 14,
the detection line 42 and the control unit 40. If the conductimetric system estimates
a reduced load in the laundry drum 16, which is lower than the maximum load of said
laundry drum 16, then the control unit sets the fan motor 37 and thereby the drying
air stream fan 30 to a rotation speed higher than the rotation speed for the maximum
load. Preferably, the estimation of the load in the laundry drum 16 is performed during
the first few minutes of the drying cycle, for example during the first five minutes.
[0049] In the second embodiment of the laundry dryer 10 with the heat pump system, the rotation
speed of the drying air stream fan 30 and the rotation speed of the laundry drum 16
are independent of each other.
[0050] In both the embodiment shown in figure 4 and 5, the laundry dyer can comprise a variable
speed compressor 32 and the control unit 40 is adapted to increase the rotational
speed of the compressor motor in response to an increasing of the rotational speed
of the drying air stream fan 30.
[0051] FIG 6 illustrates a schematic diagram of a first embodiment of the laundry dryer
10 with an air-to-air condenser 48 according to the present invention.
[0052] The laundry dryer 10 comprises a closed air stream circuit 22 formed by the laundry
drum 16, the air-to-air condenser 48, the drying air stream fan 30 and a condenser
fan 50. The air-to-air condenser 48 is an air-to-air heat exchanger and forms a thermal
interconnection between the air stream circuit 22 and the ambient air. The air-to-air
condenser 48 includes two separate channels. A first channel is provided for the air
stream of the air stream circuit 22. A second channel is provided for the ambient
air. The ambient air is blown through the second channel by the condenser fan 50.
[0053] Further, the laundry dryer 10 comprises the motor 36 and the control unit 40. The
motor 36 is connected to the control unit 40 by the motor control line 44. The drying
air stream fan 30 and the laundry drum 16 are driven by the motor 36. The first electrode
12 and the second electrode 14 are associated to a rear portion of the front frame
20. Said rear portion of the front frame 20 is substantially arranged face to face
with the front opening of the laundry drum 16. The first electrode 12 and the second
electrode 14 are connected to the control unit 40 by a detection line 42. The first
electrode 12, the second electrode 14, the detection line 42 and the control unit
40 form the conductimetric system.
[0054] The air-to-air condenser 48 cools down and dehumidifies the air stream by ambient
air, after the air stream has passed the laundry drum 16. Then, the air stream is
heated up by a heating device, for example by an electric heating element, before
the air stream is re-inserted into the laundry drum 16 again. The heating device is
not shown. The drying air stream is driven by the drying air stream fan 30 arranged
between the air-to air condenser 48 and the laundry drum 16.
[0055] If the conductimetric system estimates the reduced load in the laundry drum 16, which
is lower than the maximum load of said laundry drum 16, then the control unit sets
the motor 36 and thereby the drying air stream fan 30 and the laundry drum 16 to a
rotation speed higher than the rotation speed for the maximum load. Preferably, the
estimation of the load in the laundry drum 16 is performed during the first few minutes
of the drying cycle, for example during the first five minutes.
[0056] FIG 7 illustrates a schematic diagram of a second embodiment of the laundry dryer
10 with the air-to-air condenser 48 according to the present invention.
[0057] The laundry dryer 10 with the air-to-air condenser 48 of the second embodiment comprises
substantially the same components as the first embodiment in FIG 6. Instead of the
motor 36 for driving the drying air stream fan 30 and the laundry drum 16, the second
embodiment comprises a fan motor 37 and a drum motor 38. The fan motor 37 is provided
for driving the drying air stream fan 30. The drum motor 38 is provided for driving
the laundry drum 16. Instead of the motor control line 46 in FIG 6, the second embodiment
comprises a fan control line 45 and a drum control line 46. The fan control line 45
connects the control unit 40 to the fan motor 37. In a similar way, the drum control
line 46 connects the control unit 40 to the drum motor 38.
[0058] If the conductimetric system estimates a reduced load in the laundry drum 16, which
is lower than the maximum load of said laundry drum 16, then the control unit sets
the fan motor 37 and thereby the drying air stream fan 30 to a rotation speed higher
than the rotation speed for the maximum load. Preferably, the estimation of the load
in the laundry drum 16 is performed during the first few minutes of the drying cycle,
for example during the first five minutes.
[0059] In the second embodiment of the laundry dryer 10 with the air-to-air condenser 48
in FIG 7, the rotation speed of the drying air stream fan 30 and the rotation speed
of the laundry drum 16 are independent of each other.
[0060] FIG 8 illustrates three diagrams of rotation speeds v of an drying air stream fan
30 as function of the time t according to a first example of the present invention.
[0061] In the beginning of the drying cycle an average rotation speed v of the drying air
stream fan 30 is set for a few minutes, for example about five minutes. During this
time interval the load inside the laundry drum 16 is estimated. In dependence of the
estimated load inside the laundry drum 16 the rotation speed v is set. In FIG 8 three
examples of constant rotation speeds v are shown. A lower rotation speed v is provided
for the maximum load inside the laundry drum 16. A medium rotation speed v is provided
for a reduced load inside the laundry drum 16. A higher rotation speed v is provided
for a more reduced load inside the laundry drum 16.
[0062] FIG 9 illustrates three diagrams of rotation speeds v of the drying air stream fan
30 as function of the time t according to a second example of the present invention.
[0063] In the beginning of the drying cycle the average rotation speed v of the drying air
stream fan 30 is set for a few minutes, for example about five minutes. During this
time interval the load inside the laundry drum 16 is estimated. Then, the rotation
speed v is set in dependence of the estimated load inside the laundry drum 16. The
three examples of rotation speeds v oscillate around corresponding mean values shown
by dashed lines. The lower rotation speed v is provided for the maximum load inside
the laundry drum 16. The medium rotation speed v is provided for the reduced load
inside the laundry drum 16. The higher rotation speed v is provided for the more reduced
load inside the laundry drum 16.
[0064] FIG 10 illustrates a diagram of the rotation speed v of the drying air stream fan
30 as function of the time t according to a third example of the present invention.
In this example, the constant rotation speed v of the drying air stream fan 30 is
set. The rotation speed v of the drying air stream fan 30 may be coupled to the rotation
speed of the laundry drum 16, wherein the rotation speed v of the drying air stream
fan 30 is proportional to the rotation speed of the laundry drum 16. Further, the
rotation speed v of the drying air stream fan 30 may be independent of the rotation
speed of the laundry drum 16.
[0065] FIG 11 illustrates a diagram of the rotation speed v of the drying air stream fan
30 as function of the time t according to a fourth example of the present invention.
In this example, the rotation speed v of the drying air stream fan 30 is coupled to
the rotation speed of the laundry drum 16, so that the rotation speed v of the drying
air stream fan 30 is proportional to the rotation speed of the laundry drum 16. The
drying air stream fan 30 and the laundry drum 16 change periodically the sense of
rotation.
[0066] FIG 12 illustrates a diagram of the rotation speed of the drying air stream fan as
function of the time according to a fifth example of the present invention. In this
example, the rotation speed v of the drying air stream fan 30 oscillates around a
corresponding mean value shown by the dashed line. Also in this example, the rotation
speed v of the drying air stream fan 30 may be coupled to the rotation speed of the
laundry drum 16. In this case, the rotation speed v of the drying air stream fan 30
is proportional to the rotation speed of the laundry drum 16. Alternatively, the rotation
speed v of the drying air stream fan 30 may be independent of the rotation speed of
the laundry drum 16.
[0067] Although illustrative embodiments of the present invention have been described herein
with reference to the accompanying drawings, it is to be understood that the present
invention is not limited to those precise embodiments, and that various other changes
and modifications may be affected therein by one skilled in the art without departing
from the scope or spirit of the invention. All such changes and modifications are
intended to be included within the scope of the invention as defined by the appended
claims.
List of reference numerals
[0068]
- 10
- laundry dryer
- 12
- first electrode
- 14
- second electrode
- 16
- laundry drum
- 17
- front free end of laundry drum
- 18
- front door
- 20
- front frame
- 21
- sealing member
- 22
- air stream circuit
- 24
- refrigerant circuit
- 26
- evaporator
- 28
- condenser
- 30
- drying air stream fan
- 32
- compressor
- 34
- expansion device
- 36
- motor
- 37
- fan motor
- 38
- drum motor
- 40
- control unit
- 42
- detection line
- 44
- motor control line
- 45
- fan control line
- 46
- drum control line
- 48
- air-to-air condenser
- 50
- ambient air fan
- v
- rotation speed
- t
- time
1. A method for controlling a drying cycle of a laundry dryer (10) in dependence of the
amount of load inside a laundry drum (16), comprising the steps of:
- detecting an electric resistance and/or an electric conductivity between two or
more electrodes (12, 14) at least partly contacting the laundry inside the laundry
drum (16) and,
- estimating the amount of load inside the laundry drum (16) by evaluating the noise
and/or fluctuation of the detected electric resistance and/or conductivity, and
- controlling a rotation speed (v) of a drying air stream fan (30) for conveying a
drying air stream through the laundry drum (16) in response to the estimated amount
of load inside the laundry drum (16), wherein the rotation speed (v) of the drying
air stream fan increases with a decreasing amount of load in the laundry drum (16).
2. The method according to claim 1,
characterized in, that
the rotation speed (v) of the drying air stream fan (30) increases when the estimated
amount of load inside the laundry drum (16) is above a predetermined threshold.
3. The method according to claim 1 or 2,
characterized in, that
a rotation speed of the laundry drum (16) is controlled, wherein the rotation speed
of the laundry drum (16) is proportional to the rotation speed (v) of the drying air
stream fan (30).
4. The method according to any one of the preceding claims,
characterized in, that
the electric resistance and/or electric conductivity between the electrodes (12, 14)
are detected within a predetermined time interval at the beginning of the drying cycle
after the laundry drum starts to rotate.
5. The method according to any one of the preceding claims,
characterized in, that
before the amount of load inside the laundry drum (16) has been estimated, the drying
air stream fan (30) is driven with an average rotation speed (v).
6. The method according to any one of the preceding claims,
characterized in, that
the drying air stream fan (30) is driven with a constant rotation speed (v), after
the amount of load inside the laundry drum (16) has been estimated.
7. The method according to any one of the claims 1 to 5, characterized in, that
the drying air stream fan (30) is driven with a rotation speed (v) oscillating around
a mean value, after the amount of load inside the laundry drum (16) has been estimated,
wherein said mean value depends on the amount of load inside the laundry drum (16).
8. The method according to any one of the preceding claims,
characterized in, that
the drying air stream fan (30) and the laundry drum (16) change periodically the sense
of rotation, after the amount of load inside the laundry drum (16) has been estimated.
9. The method according to any one of the preceding claims,
characterized in, that
evaluating the noise and/or fluctuation of the detected electric resistance and/or
conductivity comprises:
measuring the value of peaks of an electric signal corresponding to the detected electric
resistance and/or conductivity, and/or
measuring the number of peaks within a time span of an electric signal corresponding
to the detected electric resistance and/or conductivity, and/or
measuring the area subtended by peaks of an electric signal corresponding to the detected
electric resistance and/or conductivity.
10. The method according to claim 9,
characterized in, that
the number of peaks within a time span of said electric signal increases with a decreasing
amount of load in said laundry drum (16).
11. The method according to any one of the preceding claims,
characterized in, that
controlling the speed of a heat pump compressor motor of the laundry dryer (10), wherein
the speed of the heat pump compressor motor increases in response to an increasing
of the rotation speed (v) of the drying air stream fan (30)
12. A laundry dryer (10) comprising a laundry drum (16), a drying air stream fan (30)
for conveying a drying air stream through the laundry drum (16) and
- at least two electrodes (12, 14) provided for detecting an electric resistance and/or
an electric conductivity of the laundry inside the laundry drum (16),
- a control unit (40) is provided for estimating the amount of load inside the laundry
drum (16) by evaluating electric resistance and/or an electric conductivity, wherein
- the control unit (40) is provided for controlling a rotation speed (v) of the drying
air stream fan (30) in response to the estimated amount of load inside the laundry
drum (16), and wherein
- the control unit (40) is adapted to drive the drying air stream fan (30) to a first
rotation speed corresponding with a first amount of load in the laundry drum (16)
and to a second rotation speed corresponding with a second amount of load in said
laundry drum (16), wherein the first rotation speed is higher than the second rotation
speed and the first amount is smaller than the second amount.
13. The laundry dryer (10) according to claim 12, characterized in, that
a motor is provided to drive into rotation both the laundry drum (16) and the drying
air stream fan (30).
14. The laundry dryer (10) according to claim 12 or 13, characterized in, that
the electrodes (12, 14) are arranged at a rear side of a front frame (20) of the laundry
dryer (10) and at an opening of said laundry dryer (10).
15. The laundry dryer (10) according to any one of the claims 12 to 14,
characterized in, that
the laundry dryer (10) comprises a heat pump system with a variable speed compressor
motor, wherein the control unit (40) is adapted to increase the rotation speed of
the variable speed compressor motor in response to an increasing of the rotation speed
of the drying air stream fan (30).