DE102019100010A1 - Operating method for a dishwasher with a heat pump cycle and dishwasher with a heat pump cycle - Google Patents

Abstract

The invention relates to a method for operating a dishwasher (1) for cleaning items in a washing compartment (2) comprising a heat pump circuit with a heat exchanger (13), together with at least one fan (14, 14 ') for generating an air flow in an air channel (10) is positioned, has. The method is characterized in that in the air duct (10) at least one temperature sensor (17) in the air flow direction behind the heat exchanger (13) is arranged, wherein a speed of the at least one fan (14, 14 ') depends on a by the temperature sensor ( 17) measured temperature (T2) is varied.

Description

The invention relates to a method for operating a dishwasher, in particular a domestic dishwasher. The dishwasher is used to clean dishes in a dishwasher and has a heat pump circuit with a heat exchanger, which is arranged together with at least one fan for generating an air flow in an air duct.

To reduce the energy consumption of dishwashers, the use of heat pumps is known. For example, the document describes EP 2 682 038 A2 a dishwasher with an air-to-water heat pump, which extracts energy from the ambient air to support energy-intensive steps of the washing program, eg heating up of washing liquid. In this case, an air duct is formed with a fan in a base of the dishwasher, in which a heat exchanger of an evaporator of the heat pump circuit is arranged. The evaporator removes heat from the air passing by. It is intended to position an air inlet on the front side of the base of the dishwasher, wherein an air outlet in the rear region of the base is arranged to the rear or to one side.

From the publication WO 2015/185086 A1 a comparable arrangement of a heat pump cycle in a dishwasher is known, wherein a variable speed fan is used to generate the air flow through the heat exchanger. A temperature of the rinsing liquid is determined by a correspondingly arranged temperature sensor and the speed of the fan is controlled as a function of the measured temperature. In this way, the heat exchanger and thus the heat pump cycle can be operated in its efficiency adjusted to the temperature of the rinsing liquid.

However, a process control of the heat pump cycle tailored exclusively to the temperature of the rinsing liquid is not optimal for all operating situations.

It is therefore an object of the present invention to provide an operating method of the type mentioned, which leads in as many operating situations to the most energy-efficient operation of the heat pump cycle as well as a dishwasher, which allows such an operating method.

This object is achieved by an operating method and a dishwasher with the features of an independent claim. Advantageous embodiments and further developments are the subject of the dependent claims.

An inventive method for operating a dishwasher is characterized in that at least one temperature sensor is arranged in the air duct in the air flow direction behind the heat exchanger, wherein a speed of the at least one fan is varied depending on a temperature measured by the temperature sensor. The temperature of the air behind the heat exchanger in the air duct allows conclusions about the operating situation of the heat exchanger, which is crucial for an efficient operation of the heat pump cycle. In this case, the temperature sensor can be arranged directly behind the heat exchanger of the heat pump or in the end region of the air duct so close to the air outlet. In this case, the temperature in the air duct, measured downstream of the heat exchanger, typically corresponds essentially to the temperature of the air at the air outlet of the air duct. This value is not only a relevant operating parameter for the heat pump cycle itself, but also for the convenience of the user, e.g. is reduced by a too cold exhaust air from the air duct. By a temperature-dependent speed control, the temperature of the discharged air can be controlled. Thereby, e.g. Condensation of liquid on surfaces (walls) behind the air outlet can be prevented. Preferably, it may be provided to increase a speed of the at least one fan when the temperature falls below a predetermined value.

It is further proposed a dishwasher for cleaning items in a Spülraum, comprising a heat pump circuit with a heat exchanger, which is positioned together with at least one fan for generating an air flow in an air duct, and wherein in the air duct at least one temperature sensor in the air flow direction behind the heat exchanger is arranged. The dishwasher further has a control device, which is set up to vary a rotational speed of the at least one fan depending on a temperature measured by the temperature sensor.
According to a further aspect, a dishwashing machine for cleaning dishes in a wash cabinet is proposed, comprising a heat pump cycle with a heat exchanger which is positioned together with at least one fan for generating an air flow in an air channel, and wherein at least one pressure sensor is arranged in the air channel, and wherein a control device is provided which is adapted to vary a rotational speed of the at least one fan depending on a pressure measured by the pressure sensor

The dishwasher preferably has an air-water heat pump, with the energy from the ambient air can be removed. This energy-intensive steps of the washing program, such as a heating of rinsing liquid, performed or supported. In this case, the air duct is preferably formed in a base of the dishwasher with the fan, wherein in the air duct, a heat exchanger of an evaporator of the heat pump cycle is arranged. Heat is withdrawn from the air passing or passing through the evaporator. In particular, it is provided to position an air inlet on the front side of the base of the dishwasher, wherein an air outlet is arranged in the rear region of the base to the rear or to one side.

In an advantageous embodiment of the method or the dishwasher, a further temperature sensor is present in the air duct. This is arranged in particular in the air flow direction in front of the heat exchanger. The further temperature sensor measures a further temperature, wherein the speed of the at least one fan is varied depending on a difference between the two measured temperatures, in particular between the temperatures before and after the heat exchanger. In this way, in addition a temperature difference, or the temperature reduction is achieved by the heat exchanger, used to control the speed of the at least one fan, which may also be relevant to an effective operation of the heat pump.

In a further advantageous embodiment of the invention or according to another aspect of the invention, the speed of the at least one fan is additionally or alternatively varied depending on a measured pressure. At least one pressure sensor is preferably arranged in the air duct.

In a further advantageous embodiment of the invention, at least two pressure sensors, of which at least one is arranged in the air duct, are provided for measuring two pressures. Preferably, the speed of the at least one fan is varied depending on a pressure difference between the measured pressures.

In order to be able to detect the operating situation of the heat exchanger in the best possible way, it is preferable to position a pressure sensor in front of and a pressure sensor in the airflow direction behind the heat exchanger. It can be provided, for example, to increase the speed of the at least one fan when the pressure difference exceeds a predetermined pressure difference limit. In this way it is prevented that e.g. due to dew of the heat exchanger whose efficiency falls too far. The volume air flow in the air duct is also an important parameter for the operation of the heat exchanger and the heat pump. The pressure measurement in combination with the influence of the volume air flow through the speed variation of the at least one fan allows the setting of the most optimal, energy-efficient operation of the heat pump cycle.

In a further advantageous embodiment of the invention, a pressure sensor is positioned in front of and a pressure sensor in the air flow direction behind an air filter arranged in the air duct. It may then be provided to monitor at a predetermined speed of the at least one fan, whether the pressure difference exceeds a predetermined pressure difference limit, wherein when exceeded, a signal is issued, which prompts for a change and / or cleaning of the air filter. This ensures that the efficiency of the heat pump cycle is not reduced by an overly clogged air filter. It is exploited that, given a given rotational speed and known other operating situation (for example a measurement at the beginning of a washing program when there is still no condensation of the heat exchanger), the pressure difference allows statements about the soiling state of the air filter.

• 1 eine schematische Schnittdarstellung einer Geschirrspülmaschine mit einem Wärmepumpenkreislauf;
• 2-6 jeweils eine schematische Darstellung eines Luftkanals mit Wärmetauscher und Ventilator(en) eines Wärmepumpenkreislaufs in verschiedenen Ausgestaltungen; und
• 7, 8 jeweils ein Diagramm zur Verdeutlichung eines Betriebsverfahrens für eine Geschirrspülmaschine.

The invention will be explained in more detail using an exemplary embodiment with the aid of figures. The figures show:

• 1 a schematic sectional view of a dishwasher with a heat pump cycle;
• 2-6 in each case a schematic representation of an air duct with heat exchanger and fan (s) of a heat pump cycle in various configurations; and
• 7 . 8th in each case a diagram to illustrate an operating method for a dishwasher.

In 1 is first a dishwasher 1 , which is suitable for carrying out an operating method according to the application, shown in a schematic sectional view. The section is a vertical plane perpendicular to a lying in the figures on the right front of the dishwasher 1 runs.

The dishwasher 1 has a sink 2 on, in the ware can be admitted and is sprayed in the rinse liquid for cleaning the dishes. By way of example, two washing utensils are provided 3 presented with items to be washed. For spraying the rinsing liquid, for example rotating spray arms are present, which for reasons of Clarity are not shown here. From items to be washed or walls of the washroom 2 Dripping rinse liquid collects in a collection pot 4 in a lower area of the washing compartment 2 , From there, the rinsing liquid is pressurized via a circulating pump back into the washing compartment 2 used for cleaning, whereby a rinse cycle is formed. The collection pot 4 is just like the circulation pump in a pedestal 5 the dishwasher 1 below the sink 2 arranged.

The dishwasher 2 the dishwasher 1 is accessible from the front via a hinged door, on which a (furniture) front is attached to a kitchenette, into which the dishwasher 1 is built to give a uniform appearance. For reasons of clarity, the pivoting door together with the (furniture) front in the figure is not shown in detail.

In the pedestal 5 runs from front to back an air duct 10 in which there is a heat exchanger 13 an evaporator and at least one fan 14 located. The evaporator is part of a heat pump cycle, not shown further, is absorbed by the heat from the environment and is used to heat the rinsing liquid.

In the area of the front of the dishwasher 1 is an air intake 11 arranged over the air in the air duct 10 can be sucked. In the front area of the air duct 10 An air filter may be positioned by the dishwasher during operation 1 when using the heat pump via the fan 14 Air in the air duct 5 is sucked in. As a result, during operation of the heat pump, an air flow is created in 1 schematically sketched by corresponding flow arrows.

In the following 2 to 6 are different designs of air ducts 10 reproduced in a heat pump cycle, for example, the in 1 shown dishwasher 1 can be used and allow the implementation of an operating procedure according to the application. In all figures, like reference numerals designate the same or equivalent elements.

2 shows a schematic sectional view of a first example of an air duct 10 who was at the dishwasher 1 the 1 can be used. The air duct 10 has an air inlet 11 , in the incoming air 6 enters, and an air outlet 12 , from the escaping air 7 exit, up. In the air duct 10 is - here schematically and exemplarily arranged centrally - a heat exchanger 13 positioned by the incoming air 6 is flowed through. In the flow direction of the inflowing or outflowing air 6 . 7 is in this example behind the heat exchanger 13 an (axial) fan 14 in the air duct 10 arranged.

The ventilator 14 is coupled with a controller, not shown here, which can control it variable speed. Preferably, the control is in a higher-level control device of the dishwasher 1 integrated. The ventilator 14 may for example be a DC motor with collector, which is driven in a PWM (Pulse Width Modulation) - method. By a variation of the pulse width ratio, a speed of the fan 14 essentially lossless and can be set in wide speed limits.

The ventilator 14 can - as shown - in the air flow direction behind the heat exchanger 13 be arranged. It is also possible in alternative embodiments, the fan 14 in front of the heat exchanger 13 to arrange. Furthermore, two or more fans positioned one behind the other can also be used 14 can be used before, behind or partially before and partly behind the heat exchanger 13 are positioned.

In an area in front of and behind the heat exchanger 13 is each a temperature sensor 16 . 17 arranged. With the two temperature sensors 16 . 17 can correspondingly a temperature T1 . T2 the incoming air 6 or the outflowing air 7 be measured. The measured temperature T2 the outflowing air 7 and possibly additionally one of the measured temperatures T1 . T2 certain temperature difference passing through the heat exchanger 13 is achieved, in one embodiment of the application according to the application method for controlling the fan 14 be used. These are the temperature sensors 16 . 17 with the said control of the fan 14 coupled. The temperature sensors 16 . 17 are evaluated to the temperatures T1 . T2 to determine. Depending on the measured temperatures T1 . T2 (and possibly other sizes) is the speed of the fan 14 varied. For example, if the temperature of the outflowing air is too low 7 , which can be perceived by users of a kitchen, in which the dishwasher is set up, as unpleasant, as they z. B. can lead to cold feet, the air flow can be increased by the speed of the fan 14 is increased.

3 shows an alternative embodiment of the air duct 10 the 2 , In this example, instead of a fan 14 two smaller (based on the diameter of the wings and thus the radial installation dimension) fans 14 ' used. This results in an advantageous in many installation situations flat rectangular cross-sectional shape of the air duct 10 ,

A variation of the airflow through the air duct 10 can be done in this embodiment, characterized in that one or both of the fans 14 ' be operated speed controlled. Alternatively, one of the fans 14 ' be switched on or off to vary the air flow in at least two stages. In that case, a check valve, for example in the form of a flap or a slide, may be provided to prevent backflow of air.

In one too 2 and 3 alternative arrangement, only one temperature sensor is present in the air duct, namely behind the heat exchanger 13 positioned temperature sensor 17 ie the temperature sensor is missing 16 , According to the invention depends on the measured temperature T2 the speed of the fan 14 varied.

In addition to a temperature measurement can, as in 4 shown, in front of and behind the heat exchanger 13 also a pressure measurement with the help of one or more pressure sensors 18 . 19 respectively. The temperature sensors 16 . 17 are for the sake of clarity in the 4-6 not shown.

In the example of 4 becomes a first pressure p1 in front of the heat exchanger 13 and a second pressure p2 behind the heat exchanger 13 determined. From a pressure difference ( p1 - p2 ), the delivered air volume flow can be determined. It can then be provided, for example, the fans 14 ' depending on the measured pressure difference to control the heat exchanger 13 and thus to operate the heat pump cycle in an advantageous range of operating parameters. Of course, the pressure measurement shown can also be used with only one fan 14 be used.

Furthermore, the pressure measurement and in particular the determined pressure difference allows a conclusion about a degree of contamination of the heat exchanger 13 to. Depending on a derived degree of contamination, for example, a signal can be generated which indicates the user to a necessary or reasonably carried out maintenance.

An alternative arrangement of the pressure sensors 18 . 19 is in 5 shown. The pressure sensor 18 does not measure the pressure in the air duct 10 in front of the heat exchanger 13 but an ambient pressure. A pressure difference measured in this way p1 - p2 allows not only a degree of contamination of the heat exchanger 13 but also, if necessary, the heat exchanger 13 upstream air filter to measure.

An air duct 10 with an air filter 15 is exemplary in the 6 shown. Here is the air filter 15 the heat exchanger 13 upstream to contamination of the difficult-to-clean heat exchanger 13 to prevent by sucked dirt particles. A pressure difference p1 - p2 allows conclusions about the degree of contamination of the air filter 15 to. If the determined degree of contamination exceeds a predetermined value, a signal can be output to the user, for changing the air filter 15 prompts.

This procedure is indicated by the diagram of 7 The diagram shows a measured pressure difference on a vertical axis Ap depending on a period of operation t _B played. The pressure difference Ap is used in this operating method for a fixed speed of the fans 14 ' carried out. This can be done, for example, in a short measuring cycle at the beginning of each dishwashing cycle of a dishwasher.

The course of the measured pressure difference Ap during the operating time t _B The dishwasher is in a curve 20 shown. It turns out that the pressure difference Ap with increasing operating time t _B increases, this increase is increasingly steep over the operating time. Next is a predetermined pressure difference limit Δp _G drawn as a horizontal line in the diagram. The rise of the curve 20 indicates an increase in the clogging of the air filter 15 out. Once the pressure difference Ap the pressure difference limit Δp _G reached, the signal is called to the user, to change the air filter 15 asks, spent.

The in the 4-6 illustrated pressure measurement and in particular the determination of a differential pressure also makes it possible to carry out the operation of the heat pump cycle in the dishwasher more efficient. With the help of known system characteristics of the air duct 10 , which reproduce, for example, the air flow in dependence on the measured differential pressure, can be determined from a measurement of the differential pressure of the air flow. The plant characteristic can be stored in a control unit of the dishwasher. It can then by speed variation of the fans 14 . 14 ' the air volume flow in the direction of an optimal for the process air volume flow can be adjusted.

Optionally, the room and / or ambient temperature can be used to determine the optimum air volume flow. This can be done by in the 2 and 3 shown standalone temperature sensors 16 . 17 be determined or by a temperature sensor, the is already present in the dishwasher and determines, for example, the temperature of the rinsing liquid. A value of such a temperature sensor, measured at the beginning of the rinsing process, reflects the room / ambient temperature. Possibly. For example, a temperature value can also be queried by the control device of the dishwasher via a building control system.

Further, depending on the results of the pressure measurement in the air duct 10 Also, a power of a compressor in the heat pump cycle are controlled when a speed controllable compressor is used. The mentioned control possibilities of the process can be combined, and also be selected depending on a washing program carried out by the dishwasher. The process control can be configured differently, for example, depending on whether a particularly energy-efficient wash program or a particularly fast or particularly quiet wash program should be performed.

An embodiment of another operating method is described below with reference to a diagram in the 8th explained in more detail. The diagram shows a time dependence of a differential pressure Δp = p1-p2, where the pressures p1 and p2 before or after the heat exchanger 13 , for example, according to the 4 to be measured. The time dependence is this time (unlike the diagram of the 7 ) in the course of a wash program, wherein the time ts the program start and the time t _E indicate the end of the program. The change of the pressure difference Ap from an initial value Δp ₀ runs according to the illustrated curve 21 for a constant speed of the fans 14 . 14 ' , A reason for the increase in pressure difference Ap lies in an increasing dew of the heat exchanger 13 caused by the dew curve rising during the program 24 is symbolized.

According to the application again is a differential pressure limit Δp _G defined by the curve 21 is exceeded in the middle of the program duration. In the operating method according to the application, a speed of the fans is provided 14 . 14 ' after exceeding the pressure difference limit Δp _G to increase. The increase in the speed of the fans 14 . 14 ' leads to a further increase in the differential pressure Ap who is in the from this time until the end of the program t _E traversed curve 22 shows.

With increasing condensation according to the curve 24 decreases at constant speed of the fans 14 . 14 ' the achievable air volume flow. This is in the curve 23 played. The method according to the application prevents the air volume flow from falling to too low a value. When exceeding the limit value of the pressure difference Δp _G and after raising the speed of the fans 14 . 14 ' increases the air flow, resulting in the sudden increase in the curve 23 reflects. In this way achieved by the operating method according to the application, that even at the end of the program, a sufficiently high air flow rate is achieved and the heat pump cycle runs with optimal energy efficiency.

LIST OF REFERENCE NUMBERS

1

dishwasher

2

Wash cabinet

3

washing items

4

purge pot

5

base

6

incoming air

7

outgoing air

10

air duct

11

air intake

12

air outlet

13

heat exchangers

14, 14 '

fan

15

air filter

16, 17

temperature sensor

18, 19

pressure sensor

20, 21, 22

Curve (pressure difference)

23

Curve (air flow)

24

Curve (condensation)

T1, T2

temperature

p1, p2

print

Ap

pressure difference

Δp ₀

Initial value of the pressure difference

Δp _G

Differential pressure limit

V

Airflow

t

Time

t _s

Start time

t _E

end time

t _B

uptime

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2682038 A2 [0002]
• WO 2015/185086 A1 [0003]

Claims (13)

Method for operating a dishwasher (1) for cleaning items to be washed in a washing compartment (2) comprising a heat pump circuit with a heat exchanger (13), which together with at least one fan (14, 14 ') for generating an air flow in an air channel (10 ), characterized in that in the air duct (10) at least one temperature sensor (17) in the air flow direction behind the heat exchanger (13) is arranged, wherein a rotational speed of the at least one fan (14, 14 ') depending on a by the temperature sensor (17) measured temperature (T2) is varied. Method according to Claim 1 in which the rotational speed of the at least one fan (14, 14 ') is increased when the temperature (T2) falls below a predetermined or predeterminable value. Method according to Claim 1 or 2 in which a further temperature sensor (16) in the air duct (10) in the air flow direction in front of the heat exchanger (13) is arranged, which measures a further temperature (T1), wherein the speed of the at least one fan (14, 14 ') depending on a Difference between the measured temperatures (T1, T2) is varied. Method according to one of Claims 1 to 3 in which the rotational speed of the at least one fan (14, 14 ') is also varied depending on a pressure. Method according to Claim 4 in which at least one pressure sensor (18, 19) is arranged in the air duct (10), the speed of the at least one fan (14, 14 ') being dependent on a pressure (p1, p2) measured by the pressure sensor (18, 19) is varied. Method for operating a dishwasher (1) for cleaning items to be washed in a washing compartment (2) comprising a heat pump circuit with a heat exchanger (13), which together with at least one fan (14, 14 ') for generating an air flow in an air channel (10 ), characterized in that in the air duct (10) at least one pressure sensor (18, 19) is arranged, wherein a speed of the at least one fan (14, 14 ') depends on a by the pressure sensor (18, 19 ) measured pressure (p1, p2) is varied. Method according to one of Claims 4 to 6 in which at least two pressure sensors (18, 19) are provided for measuring two pressures (p1, p2), of which at least one is arranged in the air duct (10). Method according to Claim 6 wherein the speed of the at least one fan (14, 14 ') is dependent on a pressure difference (Δp) between the measured pressures (p1, p2). Method according to one of Claims 4 to 8th in which at least two pressure sensors (18, 19) are arranged in the air duct (10), of which a pressure sensor (18) is positioned in front of and a pressure sensor (19) in the air flow direction behind the heat exchanger (13). Method according to one of Claims 8 to 9 in which the rotational speed of the at least one fan (14, 14 ') is increased when the pressure difference (Δp) exceeds a predetermined or predefinable pressure difference limit value (Δp _G ). Method according to one of Claims 4 to 10 in which a pressure sensor (18) is positioned in front of and a pressure sensor (19) in the air flow direction behind an air filter (15) arranged in the air duct (10). Method according to one of Claims 8 to 11 in which is monitored at a predetermined speed of the at least one fan (14, 14 '), whether the pressure difference (.DELTA.p) exceeds a predetermined pressure difference limit value (.DELTA.p _G ), wherein when exceeding a signal is output, which is to change and / or cleaning the air filter (15) prompts. Dishwasher (1) for cleaning items to be washed in a washing compartment (2), comprising a heat pump circuit with a heat exchanger (13) positioned together with at least one fan (14, 14 ') for generating an air flow in an air channel (10), wherein the dishwasher (1) is arranged in particular for carrying out the method according to one of the preceding claims, characterized in that in the air duct (10) at least one temperature sensor (17) in the air flow direction behind the heat exchanger (13) is arranged, and wherein a control device is present, which is adapted to a speed of the at least one fan (14, 14 ') depending on a by the temperature sensor (17) measured temperature (T2) to vary, and / or that in the air duct (10) at least one pressure sensor (18, 19) is arranged, and wherein a control device is provided which is adapted to a rotational speed of the at least one V Entilators (14, 14 ') depending on a by the pressure sensor (18, 19) measured pressure (p1, p2) to vary.

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