EP2734667B1 - Method for operating a heat pump dryer - Google Patents

Description

The invention relates to a method for operating a heat pump dryer, in particular circulating air heat pump dryer, so that an imminent or already occurred error in operation is recognizable. The invention further relates to a designed for carrying out the method heat pump dryer.

Recirculating heat laundry dryers typically include a laundry treatment space connected to a circulating process air duct so that the laundry treatment space and process air duct form a closed process air loop in which process air is circulated. For circulating the process air, a fan is provided in the process air duct. Fluidically before the laundry treatment room is a heater which heats the process air flowing into the laundry treatment room so that it heats laundry located in the laundry treatment room. Still wet laundry releases moisture to the process air, which emerges from the laundry treatment room as moist-warm process air. Fluidically behind the laundry treatment room is located in the process air duct, a condensation device which cools the moist-warm process air, whereupon it condenses out. The now condensed cool process air is conveyed to the heater where it is heated and returned to the laundry treatment room.

In a particularly economical working recirculating heat pump, a heat pump is provided instead of a dedicated heater and a dedicated condensation device. The heat pump operates as a heat recovery unit and has at least one evaporator, a condenser or condenser, a compressor or compressor and a relaxation device. The evaporator takes over the function of the condensation device and the condenser the function of heating. As a result, the evaporator is disposed on and thermally coupled to a warmer portion of the process air loop, and the condenser is at a colder portion of the process air loop and is thermally coupled thereto. The thermal coupling can be achieved for example via a coolant / process air heat exchanger. About the heat pump or its refrigerant is from the evaporator Heat from the process air taken and delivered to the condenser, and discharged from the condenser to the process air. The heat transfer in the heat pump is done essentially by a refrigerant that flows in a refrigerant circuit formed by the heat pump.

It is known for circulating air heat pump driers that a restricted or blocked process air duct can be identified by means of a temperature difference of the process air at different positions. The temperature difference can be sensed, for example, between an input and an output of the laundry treatment room, the condenser, etc. These two temperature sensors are needed, which is relatively complex and expensive.

Out DE 10 2005 041 145 A1 discloses a clothes dryer in which the warm air used to dry the laundry is heated using a heat pump heating system. The heat pump heating system includes a variable power compressor. The power of the compressor can be adjusted depending on a temperature of a refrigerant.

DE 10 2008 041 019 A1 describes a condensation dryer with a drying chamber for the objects to be dried, a process air circuit, a first fan in the process air circuit, a heat pump in which a refrigerant circulates, with an evaporator, a compressor, a condenser and a throttle, and a temperature sensor for measuring a Temperature of the refrigerant, and a controller, wherein the controller includes first means for comparing a temperature of the refrigerant with an upper limit temperature stored for the refrigerant in the controller; second means for the temperature-based switching off of the compressor and for switching on the compressor after the expiration of a delay period each after a shutdown; a counting device for detecting a number n of cases in which the compressor is turned off, which counting device is incremented in each case of turning off; and third means for comparing the number n with a predetermined limit number stored in the controller and for evaluating the difference in the presence of an inadmissible operating condition.

DE 10 2007 016 077 A1 discloses a condensation dryer with a drying chamber for objects to be dried, a process air circuit in which a heater for heating the process air and the heated process air is feasible by means of a first blower on the objects to be dried, an air-to-air heat exchanger and a heat pump circuit with an evaporator, a compressor and a condenser, wherein the heat pump circuit and the heater are arranged to act with a heating power in the process air circuit, a control and regulating unit is provided, through which the heating power is controlled depending on at least one parameter of the heat pump cycle. One possibility is that the parameter is detected as the power consumption of the compressor. For this purpose, corresponding data of the power supply of the compressor can be detected by the control and regulation unit, for which purpose possibly already existing sensors can be used, and evaluated accordingly.

It is the object of the present invention to provide a less complicated method for detecting a fault condition, in particular a clogging of a process air cycle, a heat pump dryer, in particular a circulating air heat pump dryer.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a method for operating a heat pump dryer, wherein at least one operating parameter of a compressor of a heat pump is monitored for a change. This heat pump dryer makes use of the fact that a disturbance of a circulation of the process air in the process air circulation on the compressor becomes noticeable. It has additionally been shown that a disturbance of a circulation of a refrigerant in the heat pump to the compressor is noticeable. In order to recognize this fault (s), only the operating parameters of the compressor, which are already monitored or can be monitored without further expenditure on equipment, need to be considered. In particular, dedicated sensors can be dispensed with. The method is used in particular for detecting an error case.

In particular, the heat pump dryer may be a household appliance (for example also referred to as "white goods"). The heat pump dryer can be a washer-dryer or a pure tumble dryer. The heat pump dryer may in particular be a circulating air heat pump dryer, since there the heat pump can work very effectively. However, the heat pump dryer may alternatively be used e.g. be an exhaust air heat pump dryer.

The heat pump dryer may in particular be a heat pump dryer as described above. The heat pump may in particular be a compression heat pump. The expansion device may be an expansion valve (also called a throttle valve), e.g. a controllable expansion valve or a capillary with a fixed flow cross-section.

An operating parameter of the compressor may, in particular, be understood as meaning a parameter (directly) relating to the compressor as such, for example a rotational speed or a power or power consumption. However, under an operating parameter of the compressor, in particular, no parameter can be understood which acts only indirectly on the compressor, such as a temperature of a refrigerant.

In particular, the compressor may be a variable speed or variable speed compressor.

It is a preferred embodiment that the compressor is operated at a constant speed ω and an electric power P of the compressor is monitored. Under an electric power can be understood in particular at least one parameter from which the power can be derived, for example, a motor current of a drive motor of the compressor at a constant motor voltage. The determination of the electrical power can be determined, for example, by means of a determination of a value of a current which passes through a stator winding of the drive motor.

It is an alternative preferred embodiment that the compressor is operated at a constant electric power P and a speed w of the compressor is monitored. In both modes, a (fast or slow) change in power P are used to detect an announcing or already existing error case.

It is still a preferred embodiment that is monitored for a rapid change of at least one operating parameter p out. As a result, in particular, a threatening or occurred fault can be detected which considerably impairs operation of the heat pump drier in a short time, prevents further operation or even damages the heat pump drier, e.g. an immediate clogging of the process air duct or a break in the refrigeration cycle.

It is a preferred development that is monitored by means of a gradient method on the temporal change of the at least one operating parameter p out. A change with time of one or more variable operating parameters p (for example the rotational speed, the power and / or the load torque) that is variable for a particular operating mode is determined and compared with a predetermined limit value. In particular, the at least one operating parameter p may be detected at regular time intervals Δt and the gradient Δp / Δt compared with the predetermined threshold value. The gradient method can also be carried out, for example, with average values of the at least one operating parameter p over a plurality of time intervals Δt.

It is still a preferred development that is monitored for the change by means of an integral method. In this case, in particular, a plurality of values of the at least one operating parameter p can be recorded at different times t and summed or integrated into a total value and the total value compared with a predetermined limit value.

It is yet another preferred embodiment that is monitored for reaching or passing through a predetermined threshold value of the at least one operating parameter p as such. Thus, not the temporal change of the at least one operating parameter p is considered, but the at least one operating parameter p itself. This has the advantage that a slowly developing, eg over several operating cycles, erroneous event can be detected, for example a slow clogging of the Process air duct or a hairline crack in the refrigeration cycle. Also In this way, errors can be detected which are already present at the beginning of an operating cycle.

It is a preferred embodiment for the case that the compressor is operated at a constant speed w, that an abnormal (not a normal, error-free operation corresponding performance increase) is detected and subsequently initiated by the heat pump dryer at least one action.

The at least one action may include (at least) a notification signal to a disabled process air circulation. Because with a clogging of the process air duct and thus a reduced process air volume flow heat transfer between the evaporator and the condenser is reduced. The resulting increased temperature difference between the evaporator and the condenser leads to an increased pressure difference between an inlet and an outlet of the compressor, which in turn leads to an increased compression load. Consequently, a power increase is needed to keep the speed ω of the compressor constant.

The alert signal may be a warning signal (e.g., visual and / or audible) to a user. The warning signal for the user may, for example, also include a text with an indication of possible causes and, if necessary, a troubleshooting (for example a change of a lint filter).

The at least one action may also include at least one action that affects operation of the heat pump dryer, e.g. switching off or switching to a fault mode of the heat pump dryer.

At least one action can therefore be triggered if an electric power P of the compressor within a predetermined period .DELTA.t increased more than a predetermined (upper) threshold .DELTA.Pmax, ie .DELTA.P / .DELTA.t = .DELTA.Pmax or .DELTA.P / .DELTA.t> .DELTA.Pmax (in particular for a detection a quick change). Alternatively or additionally, the at least one action can be triggered if a power P of the compressor reaches or exceeds a predetermined upper threshold value Pmax, ie P = Pmax or P> Pmax (in particular for a detection of a slow change).

Also, it is a preferred embodiment, in the case where the compressor is operated at a constant speed ω, that abnormal power reduction is detected, and subsequently, an action related to refrigerant loss is triggered. Because it has been shown that with a loss of coolant, a lower power is needed to keep the speed ω constant. The at least one action can be configured analogously as described above. In particular, the warning signal may give the user an indication of a loss of refrigerant and / or give an indication to notify a customer service or issue such notification itself, e.g. over the internet with a networked heat pump dryer. In particular, the at least one action may e.g. include switching off or switching to an error mode of the heat pump dryer in order to avoid a total failure of the heat pump dryer and thus high repair costs.

In particular, at least one action may then be initiated if a power P of the compressor decreases more than a predetermined (lower) threshold Pmin within a predetermined period of time Δt, i. ΔP / Δt = Pmin or ΔP / Δt <ΔPmin (in particular for detection of a rapid change). Alternatively or additionally, the at least one action may be triggered if a power P of the compressor reaches or falls below a predetermined threshold Pmin, i. P = Pmin or P <Pmin (especially for a slow change detection).

It is a preferred embodiment for the case that the compressor is operated at a constant power P, that an abnormal speed decrease is detected and following, e.g. analogously as described above, at least one action is triggered. The at least one action may include an output of at least one notification signal to a disabled process air circulation.

The at least one action can thus be triggered, in particular, if a speed ω of the compressor falls more sharply within a predetermined period Δt than a predetermined (lower) threshold Δωmin, ie Δw / Δt = Δωmin or Δω / Δt <Δωmin (in particular for detection a quick change). Alternatively or additionally, the at least one action can be triggered if a speed ω of the compressor reaches or falls below a predetermined threshold value ωmin, ie ω = ωmin or ω <ωmin (in particular for detection of a slow change).

It is still a preferred embodiment for the case that the compressor is operated at a constant power, that an abnormal speed increase is detected and following, e.g. analogously as described above, at least one action is triggered. The at least one action may include an output of at least one notification signal for a loss of refrigerant.

The at least one action can therefore be triggered, in particular, if a speed w of the compressor increases more than a predetermined (upper) threshold value Δωmax within a predetermined time period Δt, i. Δω / Δt = Δωmax or Δω / Δt> Δωmax (in particular for detection of a rapid change). Alternatively or additionally, at least one action may be triggered if a speed w of the compressor reaches or exceeds a predetermined threshold ωmax, i. w = ωmax or w> ωmax (especially for a slow change detection).

In place of or in addition to the speed and / or power, generally also a load torque T may be used as an operating parameter, i.e. as an operating parameter to be regulated or as an operating parameter to be monitored.

Generally, at least the method may also be triggered based on the integral method or based on any other suitable method.

The at least one limit value can be dependent on an arbitrarily adjustable but then at least temporarily fixed operating parameter (eg a constant speed or power). In particular, a plurality of limit values can be used or stored by the heat pump drier in dependence on at least one other operating parameter, for example in the form of a table or characteristic curve. For example, the limit values of the rotational speed ωmax or Δωmax and / or ωmin or Δωmin can be dependent on the currently regulated power, ie = Δωmin (P). Analogously, the limit values of the power P Pmax and / or Pmin can be dependent on the currently controlled rotational speed w, ie ΔPmax = ΔPmax (ω), Pmax = Pmax (ω), and / or ΔPmin = ΔPmin (ω), Pmin = Pmin ( ω). In general, the threshold values can also be dependent on other operating parameters, eg on the load torque T, eg as ΔPmax = ΔPmax (ω, T), etc.

The above statements regarding a threshold value comparison based on a temporal gradient and / or an absolute value can be carried out for each suitable operating parameter p.

It is also a preferred embodiment that additionally a temperature difference of a process air and / or the refrigerant is measured. Thus, a (occurred or announcing) error case with a further improved accuracy and increased security can be determined.

The object is also achieved by a heat pump dryer, in particular circulating air heat pump dryer, wherein the heat pump dryer is set up for carrying out the method. The heat pump dryer can be designed analogously to the method and also achieve the same advantages. An advantage is for example a fault detection without or with only a small additional expenditure on equipment. In particular, the compressor may be a variable speed or variable speed compressor.

It is a preferred embodiment that the method runs at least partially in a central control unit of the heat pump dryer.

It is a preferred embodiment that the method at least partially runs in a motor control of the heat pump dryer.

Fig.1

zeigt einen als Haushaltsgerät ausgestalteten erfindungsgemäßen Umluft-Wärmepumpentrockner 1 und

Fig.2

zeigt als Ablaufdiagramm einen möglichen Ablauf für eine Fehlererkennung.

In the following figures, the invention will be described schematically with reference to a preferred embodiment schematically.

Fig.1

shows a designed as a household appliance according to the invention convection heat pump drier 1 and

Fig.2

shows as a flowchart a possible procedure for error detection.

Fig.1 shows a designed as a household appliance heat pump dryer in the form of a circulating air heat pump dryer 1. The circulating heat pump dryer 1 has a laundry treatment room in the form of a rotatable laundry drum 2, which is connected to a circulating process air duct 3. The laundry drum 2 and the process air duct 3 form a closed process air circuit in which process air L is circulated. For circulating the process air L, a fan 4 is present in the process air duct 3. In terms of flow technology, in front of the laundry drum 2 there is a condenser 8 of a heat pump acting as a heater (as will be described in more detail below), which heats the process air L flowing into the laundry drum 2 so that this laundry W warming up in the laundry drum 2 warms up. Still wet laundry W gives off moisture to the process air L, which emerges as a moist-warm process air L from the laundry drum 2. Fluidically behind the laundry drum 2 is located in the process air duct 3 serving as a condenser evaporator 7 of the heat pump, which cools the hot-humid process air L, whereupon it condenses out. The now condensed cool process air L is conveyed to the condenser 8 acting as heating, heated there and fed back into the laundry drum 2.

For particularly energy-saving operation of the recirculating heat pump dryer 1 is a heat pump 7 to 10 with an evaporator 7, a condenser 8, a variable speed compressor or compressor 9 and a relaxation device here in the form of a capillary 10 as a heat recovery unit. At the heat pump 7 to 10, heat is taken up by the evaporator 7 from the process air L and passed to the condenser 8, and discharged from the condenser 8 back to the process air L. The heat transfer in the heat pump 7 to 10 takes place essentially by a refrigerant K, which flows in a formed by the heat pump 7 to 10 refrigeration cycle.

The circulating-air heat pump drier 1 furthermore has a control device 11, which, inter alia, receives and / or evaluates operating parameters of the compressor 9 and controls or regulates the compressor 9. The control device 11 is coupled to two temperature sensors 12 and 13, which here measure a temperature difference of the process air L, here purely by way of example in front of and behind the laundry drum, alternatively, for example, also upstream of and behind the evaporator 7.

In an operation of the recirculating heat pump dryer 1, it may happen that the process air circuit clogged, e.g. due to clogging of a lint filter or blower 4. This can be done quickly, e.g. suddenly or within a few seconds or minutes. With a slow blockage of the process air cycle, the clogging can build up over several operating cycles. Also, there may be a slow leakage and thus escape of the refrigerant K from the heat pump 7 to 10, e.g. by a leaking seal or hairline crack, or to a quick leak, e.g. due to breakage of a pipe or loosening of a connection of the refrigeration cycle.

The error detection will be described in the following with reference to an exemplary operation of the circulating air heat pump dryer 1 in an operating mode, as well as a flowchart in Fig.2 shown. As shown in step S1, the control device 11 regulates the compressor 9 to a predetermined rotational speed ω. Alternatively, the compressor 9, for example, be adjusted to a constant power or a constant torque. At a predetermined speed ω, the control unit 11 monitors an electric power (alternatively or additionally: a load torque) of the compressor 9 by monitoring a stator current of a drive motor (o.Fig.) Of the compressor 9, for example, is measured or calculated at regular time intervals .DELTA.t.

The controller 11, as shown in step S2, monitors whether the power P is greater than or equal to a predetermined time Δt or a multiple thereof. increased by a first threshold ΔPmax (ω) predetermined (fast blockage). If yes ("J"), at least one action A1 can be initiated by the control unit 11, e.g. together with an acoustic warning signal a text "process air circulation clogged, please check lint filter" or similar output, possibly together with a transfer of the circulating air heat pump dryer 1 in a failure mode in which the drying process is stopped.

Exceeds as in step S3 of Fig.2 shown, the power P as such a second threshold Pmax (ω) (slow blockage), can be performed by the control unit 11 an action A2, eg a text "process air circulation is threatening to clog, please check lint filter" or similar. spent, possibly together with a transfer of the circulating heat pump dryer 1 in a failure mode in which the drying process is stopped.

On the other hand, it decreases as in step S4 of FIG Fig.2 shown, the power P within a predetermined period .DELTA.t or a multiple thereof, for example by a first threshold .DELTA.Pmax (ω) predetermined (quick coolant outlet), the control unit 11 also at least one action A3 are triggered, for example, together with an audible warning a text "coolant outlet, heat pump defective, please contact Customer Service" or similar be issued, advantageously together with a transfer of the circulating air heat pump dryer 1 in an error mode in which the drying process, in particular the operation of the heat pump 7 to 10, is stopped.

If the power P is lower than in step S5 of FIG Fig.2 shown as such a second threshold Pmin (ω) (slower coolant outlet), the controller 11 as at least one action A4, for example, also the text "coolant outlet, heat pump defective, please contact customer service" or similar. be issued, advantageously together with a transfer of the circulating air heat pump dryer 1 in an error mode in which the drying process, in particular the operation of the heat pump 7 to 10, is stopped.

In order to provide redundancy and thus increased security of error detection with respect to blocking the process air cycle, the controller may additionally determine a temperature difference across the temperature sensors 12 and 13 (eg, by the gradient method, the integral method, or by direct comparison with a threshold) and at least following to resolve an action A5 (step S6). For example, action A5 may be similar to actions A1 and / or A2.

Of course, the present invention is not limited to the embodiment shown.

Thus, the laundry drying device (dryer or washer-dryer) can also be configured as an exhaust air dryer, in which no circulating process air circuit is present, but from outside a cooling air inlet channel to the laundry treatment room leads and a cooling air outlet channel leads from the laundry treatment room to the outside. In particular, in one embodiment as exhaust air dryer drying device may be present in the process air cycle upstream of the laundry treatment room to accelerate a drying process.

Also may be measured and evaluated for an additional increase in accuracy of error detection, a temperature difference at the heat pump, for example in front of and behind the evaporator, the condenser, the compressor and / or the expansion device.

LIST OF REFERENCE NUMBERS

1

Forced-air heat pump dryer

2

washing drum

3

Process air duct

4

fan

7

Evaporator

8th

condenser

9

compressor

10

capillary

11

control device

12

temperature sensor

13

temperature sensor

A

action

S

step

K

refrigerant

L

process air

ω

Speed of the compressor

P

electrical power of the compressor

Apmax

upper limit

ΔPmin

lower limit

Pmax

upper limit

pmin

lower limit

Claims (12)

1. Method (S1-S6) for operating a heat pump dryer (1), especially an air circulation heat pump dryer (1), wherein, in order to identify a disruption to a circulation of process air or a disruption to a circulation of a coolant in a heat pump (7 to 10), at least one operating parameter (ω, P) of a compressor (9) of the heat pumps (7 to 10) is monitored (S2 to S5) for a change.
2. Method (S1-S6) according to claim 1, wherein the compressor (9) is operated at a constant speed (ω) and a power (P) of the compressor (9) is monitored.
3. Method according to claim 1, wherein the compressor (9) is operated at a constant power (P) and a speed (ω) of the compressor (9) is monitored.
4. Method (S1-S6) according to one of the preceding claims, wherein there is monitoring (S2, S4) for a change (ΔP/Δt) in the at least one operating parameter (P).
5. Method (S1-S6) according to one of the preceding claims, wherein there is monitoring (S3, S5) for the reaching or exceeding of a predefined threshold value (Pmax, Pmin) of the at least one operating parameter (P).
6. Method (S1-S6) according to claim 2 and one of claims 4 and 5, wherein an increase in power (S2, S3) is identified and subsequently at least one action (A1, A2) is initiated, especially a warning signal regarding an impeded flow of process air.
7. Method (S1-S6) according to claim 2 and one of claims 4 or 5, wherein a decrease in power (S4, S5) is identified and subsequently at least one action (A3, A4) is initiated, especially a warning signal regarding a loss of coolant.
8. Method according to claim 3 and one of claims 4 or 5, wherein a lowering of speed is identified and subsequently at least one action is initiated, especially a warning signal regarding an impeded flow of process air.
9. Method according to claim 3 and one of claims 4 or 5, wherein an increase in speed is identified and subsequently at least one action is initiated, especially a warning signal regarding a loss of coolant.
10. Method (S1 to S6) according to one of the preceding claims, wherein a temperature difference of process air (L) is additionally measured (S6) via a laundry drum (2), in which laundry items (W) to be dried are stored.
11. Heat pump dryer (1), especially air circulation heat pump dryer (1), which heat pump dryer (1) has a heat pump (7 to 10), a compressor (9) and a central control unit (11), wherein the central control unit (11) is designed to carry out the method (S1 to S6) according to one of the preceding claims.
12. Heat pump dryer (1) according to claim 11, which heat pump dryer (1) has a speed-regulated compressor (9).

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