EP2887764B1 - Domestic appliance and monitoring method for a domestic appliance - Google Patents

Description

The present invention relates to a household appliance, for example a dishwasher, and a monitoring method for such a household appliance.

Heating elements of household appliances, such as dishwashers, can be controlled by means of relays. In order to ensure the function of the heating elements, such a circuit may consist of a safety relay and a respective working relay for each heating element. Existing processes use relays with changeover contacts to monitor the heating elements. One of the contacts can be used as a feedback signal. However, this arrangement is unfavorable in terms of robustness of the monitoring against false errors, since the contact used as a feedback signal must be used in the small signal range and thus is prone to oxide formation.

Another possibility of monitoring is the measurement of the heating current of a heating element. In this method, however, the respective heating element must be completely switched to the mains in order to detect whether the heating element has burned out. Furthermore, this error can not be distinguished from a relay error.

EP 2 386 806 B1 discloses a domestic appliance comprising a heating circuit for heating a fluid, wherein the fluid heating circuit comprises a heating element which can optionally be supplied with power to effect the heating of the fluid, and a monitoring unit for monitoring the operation of the heating circuit. The monitoring unit is configured to monitor at least one electrical potential inherent in the heating circuit, wherein the at least one electrical potential inherent in the heating circuit is at least one of an internal electrical potential connected to a first terminal of the heating element connected to an on / off switch of the heating circuit , and an internal electrical potential connected to a second terminal of the heating element connected to a power switch of the device or to a circuit breaker for switching off the heating circuit in case of malfunction of the on / off switch connected is detected. The monitoring unit is further configured to determine a value of the voltage of the power distribution network and calculate a first and a second electrical reference potential based on the detected value of the voltage of the power distribution network, comparing the at least one detected internal electrical potential with the first and second electrical reference potential, and Detecting a condition of proper operation or malfunction of the heating circuit, wherein the condition of malfunction is detected in the event that the at least one detected internal electric potential does not fall within a range of values lying between the first and second electrical reference potentials.

EP 0 924 331 B1 discloses a safety circuit for a heating circuit of a washing machine, a dishwasher or a dryer, the heating circuit having a series circuit comprising a heating switch contact, a heating resistor and a safety switch. A monitoring arrangement monitors the heating circuit for faults and, in the event of an error, causes the heating circuit or the machine to be shut down.

Against this background, an object of the present invention is to provide an improved monitoring of a household appliance.

According to the invention, a household appliance, in particular a water-conducting household appliance is proposed, which is at least two heating elements, wherein a respective heating element of the at least two heating elements is coupled via a respective first node to a respective working relay for driving the respective heating element, wherein the first node via a feedback device for providing a common working relay feedback signal are high impedance coupled, and having a monitoring device for monitoring the provided work relay feedback signal to detect a fault condition of the household appliance.

Several heating elements can be controlled in this way in the household appliance, taking into account the functional safety. Detecting an error condition, and in particular a fault diagnosis, can result in an unsafe one Operation of the household appliance can be avoided. Since the monitoring device does not receive a feedback signal from a contact of a relay, the monitoring is robust with respect to fake errors. The switching state of the relay can be monitored with little effort and cost, since only a high-impedance coupling of the first node by the feedback device, such as a feedback circuit, is realized.

The household appliance is for example a dishwasher.

The working relay feedback signal is formed by this high-impedance coupling. The heating elements act in this constellation as short circuits, so have low-resistance properties. An error of one of the heating elements or one of the working relay thus leads to a change in the working relay feedback signal and can therefore be easily detected. The at least two heating elements are, for example, as heaters, in particular as a thin-film heating and a heater for drying a drying material, for. As zeolite formed.

In one embodiment of the household appliance, the feedback device has a voltage divider.

The voltage divider can be formed for example by resistors. These can be made high impedance compared to the heating elements in order to realize the high-impedance coupling of the heating elements to the first node.

In a further embodiment, the at least two heating elements are coupled to a second node and connected to a safety relay.

The safety relay is used to disconnect the heating elements from the power supply. In addition, this safety relay can be included in the monitoring by the monitoring device.

In another embodiment, the monitoring device is configured to monitor a safety relay feedback signal provided at the second node and dependent on the safety relay.

The safety relay feedback signal is affected by both the safety relay and the heating elements. To all three relays, i. Both the safety relay and the safety relay can be monitored using the safety relay feedback signal and the working relay feedback signal.

In another embodiment, the monitoring device is configured to monitor a relationship of the safety relay feedback signal and the working relay feedback signal to each other and to detect a fault condition when the ratio changes.

In error-free operation of the household appliance, i. the heating elements and the relays, there is an adjusting signal relationship between the safety relay feedback signal and the working relay feedback signal. If, for example, one of the heating elements has burned out, the working relay feedback signal shifts and the fault state can be detected by means of a ratio formation of the two feedback signals without one of the heating elements having to be switched on.

In a further embodiment, the resistors of the feedback device are selected such that the safety relay feedback signal and the working relay feedback signal are identical in error-free operation of the heating elements, the working relay and the safety relay.

In one implementation, the two feedback signals may be at identical or nearly identical levels in error-free operation. A deviation between the signals can thus be regarded as an error case.

In another embodiment, the monitoring device is configured to perform a predefined switching sequence of the working relay and the safety relay and to evaluate the ratio of the working relay feedback signal to the safety relay feedback signal in each switching state of the switching sequence.

Whether one of the relays can not be switched on can be checked using the predefined switching sequence. In each switching state of the sequence, certain signal ratios are expected. If these do not set within a defined time, it can be assumed that one of the relays does not switch. Which relay is this can be determined via the respective switching step of the sequence.

In another embodiment, the monitoring device is configured to turn on one of the work relays and to evaluate the resulting work relay feedback signal.

To determine which heater is blown or has some other fault, one of the work relays can be turned on and the resulting work relay feedback signal evaluated.

In another embodiment, the monitoring device is configured to perform a predefined switching sequence of the working relay and to evaluate the resulting work relay feedback signal.

In the predefined switching sequence, for example, first one and then the other working relay can be switched on. Subsequently, the respective work relay feedback signal can then be evaluated or evaluated.

In a further embodiment, the monitoring device is a microcontroller.

The microcontroller may be a microcontroller of the household appliance, which also has other functions.

In a further embodiment, the monitoring device is configured to detect a shifting of the potential of the safety relay feedback signal.

Such a shifting of the potential gives an indication of whether one of the heating elements has a ground fault. Ground fault in this context means that one of the heating elements is an unintentional electrically conductive connection got to earth potential. This may be the case, for example, if the PE conductor is incorrectly connected.

In a further embodiment, the fault state of the household appliance has one of the fault conditions: an error state of one of the heating elements, a fault state of both heating elements, a fault state of a safety relay, a fault state of a working relay and / or a faulty connection of one of the heating elements to the protective conductor.

An error condition of the heating elements may be a burnout of one or both heating elements. A fault condition of the relay may be a stuck relay or a non-switched relay. A faulty connection of one of the heating elements to the protective conductor can be a ground fault of one of the heating elements.

Further, a method for monitoring a household appliance, in particular a water-conducting household appliance, which has at least two heating elements, wherein a respective heating element of the at least two heating elements is coupled via a respective first node with a respective working relay for driving the respective heating element proposed. The method includes providing a common working relay feedback signal via a feedback device to which the first nodes are high impedance coupled, and monitoring the provided working relay feedback signal to detect a fault condition of the household appliance.

According to one embodiment, the at least two heating elements are switched off in the provision of the common working relay feedback signal.

In this case, the heating elements are simple low-resistance resistors. In case of failure of one of the heating elements, ie when one of the heating elements has burned out, one of the low-resistance connections represented by the heating elements is missing, which is detected as a change in the working relay feedback signal.

Furthermore, a computer program product is proposed, which on a program-controlled device causes the execution of the method explained above.

A computer program product, such as a computer program means may, for example, be used as a storage medium, e.g. Memory card, USB stick, CD-ROM, DVD, or even in the form of a downloadable file provided by a server in a network or delivered. This can be done, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program means.

The embodiments and features described for the proposed domestic appliance apply correspondingly to the proposed method.

Fig. 1

zeigt eine schematische Ansicht eines ersten Ausführungsbeispiels einer Geschirrspülmaschine;

Fig. 2

zeigt eine schematische Ansicht eines zweiten Ausführungsbeispiels einer Geschirrspülmaschine;

Fig. 3

zeigt eine mögliche Schaltsequenz der Arbeitsrelais und des Sicherheitsrelais zur Erkennung eines Fehlerzustands; und

Fig. 4

zeigt ein schematisches Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zur Überwachung einer Geschirrspülmaschine.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. Furthermore, the invention will be explained in more detail by means of preferred embodiments with reference to the attached figures.

Fig. 1

shows a schematic view of a first embodiment of a dishwasher;

Fig. 2

shows a schematic view of a second embodiment of a dishwasher;

Fig. 3

shows a possible switching sequence of the working relay and the safety relay for detecting an error condition; and

Fig. 4

shows a schematic flow diagram of an embodiment of a method for monitoring a dishwasher.

In the figures, the same or functionally identical elements have been given the same reference numerals, unless stated otherwise.

Fig. 1 shows a schematic view of a first embodiment of a household appliance 1, in particular a dishwasher.

The dishwasher 1 has a first heating element 3 and a second heating element 4. These are connected via a respective first node K1, K2 to a respective working relay 5, 6. The working relay 5 controls the first heating element 3 and the working relay 6, the second heating element 4 at.

The first nodes K1, K2 are coupled in a high-impedance manner via a feedback device FB for providing a common working relay feedback signal 7. The high-impedance coupling can be done for example by a voltage divider formed by the resistors R1, R2, R3. The values of the resistors R1, R2, R3 are high-resistance compared to the resistance values representing the two heating elements 3, 4. A monitoring device 2 monitors the provided working relay feedback signal 7 to detect a fault condition of the dishwasher 1. Such a fault condition may be an error of one of the heating elements 3, 4 or one of the working relay 5, 6.

Fig. 2 shows a schematic view of a second embodiment of a dishwasher 1.

According to this embodiment, the two heating elements 3, 4 are connected via a second node 3 to a safety relay 8. Parallel to this safety relay 8, a resistor R6 is connected. Other resistors R4, R5, R7 may be provided in the assembly. The safety relay 8 is connected to potential L (high). The working relay 5, 6 are connected to potential N (low, ground). The monitoring device 2 receives in this embodiment not only the

Working relay feedback signal 7, but also a safety relay feedback signal 9, which depends on the safety relay 8 and the heating elements 3, 4.

As in Fig. 2 Also shown, a ground fault of a heating element, here heating element 3, via a resistor R _PE done (reference numeral 10). This can also be detected by the monitoring device 2.

The following states may occur and be detected by the monitoring device 2. Here, exemplary signal values will be specified. Furthermore, it is assumed that the feedback signals 7, 9 have the same signal level in error-free operation. However, this may vary depending on the specific embodiment.

occurring Conditions:

Heating elements 3, 4 off and no error: the two feedback signals 7, 9 have the same signal level in the error-free state. The signal level is approximately in the middle of the measuring range at 1.

Heating elements 3, 4 and a working relay 5, 6 glued: The working relay feedback signal 7 and the safety relay feedback signal 9 are connected to ground (N) low resistance. Both signals are equal to 0.

Heating elements 3, 4 and the safety relay 8 glued: The work relay feedback signal 7 and the safety relay feedback signal 9 are low impedance connected to mains potential (L). Both signals are equal to 3.

Heating elements 3, 4 and a heating element 3, 4 blown: The work relay feedback signal 7 and the safety relay feedback signal 9 are no longer the same, since the low-resistance connection through a heating element 3, 4 is missing. This shifts the voltage divider ratio of the work relay feedback signal 7 and the error condition can be detected by a ratio of the two feedback signals 7, 9. However, it can not be distinguished as to which of the heating elements 3, 4 is burned.

In addition to the error detection, the monitoring device 2 can perform a fault diagnosis.

With the help of a test sequence can be checked in the case of a blown heating element 3, 4, which of the two heating elements 3, 4 is burned. In the test sequence, one of the two working relays 5, 6 is switched on and the working relay feedback signal 7 is evaluated.

Whether one of the relays 5, 6, 8 can not be switched on can be checked with the aid of a defined switch-on sequence, as described by way of example in FIG Fig. 3 is shown. In each switching state of the sequence, certain signal ratios are expected. If these do not set within a defined time, it can be assumed that one of the relays 5, 6, 8 does not switch. Which relay 5, 6, 8 is that can be determined via the switching step of the sequence.

In the case of a ground fault of one of the heating elements 3, 4, the signal levels of the two feedback signals 7, 9 shift in the direction of GND or L. This signal shift can be used as a measure of a ground fault.

In the in Fig. 3 shown switching sequence represents S0 the initial state. In switching state S1, both working relay 5, 6 are turned on. In switching state S2, both working relay 5, 6 are turned off. In switching state S3, the safety relay 8 is turned on. In switching state S4, a working relay 5, 6 and the associated heating element 3, 4 are turned on. In the switching state S5 a working relay 5, 6 and the associated heating element 3, 4 are turned off again. In switching state S6, the safety relay 8 is turned off.

Again Fig. 3 In the switching state S4, the work relay feedback signal 7 (value 1.5) and the safety relay feedback signal 9 (value 3) differ.

The following table shows possible errors with the associated switching states of the relays 5, 6, 8 and the heating elements 3, 4, a ground fault 10 and the level of the feedback signals 7, 9 are removed. error case Safety Relay 8 Working relay 6 Working relay 5 Heating element 4 burned Heating element 3 blown Ground fault GND = N Ground fault GND = L Working relay feedback signal 7 Safety Relay Feedback Signal 9 No mistake 0 0 0 0 0 0 0 1 1 Ground fault GND = L 0 0 0 0 0 0 1 2.5 2.5 Ground fault GND = N 0 0 0 0 0 1 0 0.2 0.2 Heating element 4 burned 0 0 0 1 0 0 0 0.8 1.2 Heating element 3 blown 0 0 0 0 1 0 0 0.8 1.2 Safety relay 8 glued 1 0 0 0 0 0 0 3 3 Working relay 6 glued 0 1 0 0 0 0 0 0 Working relay 5 glued 0 1 0 0 0 0 0 0

Dishwasher 1 described here can detect whether one or more heating relays 5, 6, 8 are glued. It can also be recognized whether a relay 5, 6, 8 can not be turned on. It is also possible to detect a burned-out heating element 3, 4 without connecting the heating element 3, 4 to the mains. Furthermore, a ground fault 10 of the heating elements 3, 4 can be detected without connecting the heating elements 3, 4 to the mains. For the monitoring of three relay switching states only two signals 7, 9 are required. In particular, no changeover relays are necessary.

Fig. 4 shows a schematic flow diagram of an embodiment of a method for monitoring a dishwasher 1, as shown in Fig. 1 or 2 is shown.

In a first step 201, a common working relay feedback signal 7 is provided via a feedback device FB, with which the first nodes K1, K2 are coupled in a high-impedance manner.

Subsequently, the provided work relay feedback signal 7 is monitored in a second step 202 to detect a fault condition of the household appliance 1. This can be done, as described above, by changing the working relay feedback signal 7 or by changing a ratio between this and another feedback signal 9.

Although the present invention has been described with reference to embodiments, it is variously modifiable.

Used reference signs:

1

Household appliance, in particular dishwasher

2

monitoring device

3.4

heating elements

5.6

Operating relay

7

Operating relay feedback signal

8th

safety relay

9

Safety relay feedback signal

10

Connection between PE conductor and ground

FB

Feedback device

K1, K2

first node

K3

second node

PE

Protective conductor (PE conductor)

R1, R2, R3

voltage divider

R4, R5, R6, R7, R _PE

resistors

N, L

potentials

GND

Dimensions

S0-S6

switching states

201-202

steps

Claims (15)

1. Domestic appliance (1) having: at least two heating elements (3, 4), wherein one respective heating element of the at least two heating elements (3, 4) is coupled by way of a respective first node (K1, K2) to a respective operating relay (5, 6) for actuating the respective heating element (3, 4), wherein the first nodes (K1, K2) are coupled with high resistance via a feedback facility (FB) in order to provide a shared operating relay feedback signal (7), and
   a monitoring facility (2) for monitoring the operating relay feedback signal (7) provided in order to recognise an error status of the domestic appliance (1).
2. Domestic appliance (1) according to claim 1, characterised in that the feedback facility (FB) has a voltage divider (R1, R2, R3).
3. Domestic appliance (1) according to claim 1 or 2, characterised in that the at least two heating elements (3, 4) are coupled to a second node (K3) and connected to a safety relay (8).
4. Domestic appliance (1) according to claim 3, characterised in that the monitoring facility (2) is designed to monitor a safety relay feedback signal (9) provided on the second node (K3) and dependent on the safety relay (8).
5. Domestic appliance (1) according to claim 4, characterised in that the monitoring facility (2) is designed to monitor a ratio of the safety relay feedback signal (9) and the operating relay feedback signal (7) and to recognize an error status with a change in the ratio.
6. Domestic appliance (1) according to claim 5, characterised in that the resistances (R1, R2, R3) of the feedback facility (FB) are selected such that the safety relay feedback signal (9) and the operating relay feedback signal (7) are identical in the error-free operation of the heating elements (3, 4), the operating relays (5, 6) and the safety relay (8).
7. Domestic appliance (1) according to one of claims 4 to 6, characterised in that the monitoring facility (2) is designed to perform a predefined switching sequence of the operating relays (5, 6) and the safety relay (8) and to assess the ratio of the operating relay feedback signal (7) relative to the safety relay feedback signal (9) in each switching state of the switching sequence.
8. Domestic appliance (1) according to one of claims 1 to 7, characterised in that the monitoring facility (2) is designed to switch on one of the operating relays (5, 6) and to assess the operating relay feedback signal (7) resulting therefrom.
9. Domestic appliance (1) according to one of claims 1 to 8, characterised in that the monitoring facility (2) is designed to perform a predefined switching sequence of the operating relays (5, 6) and to assess the operating relay feedback signal (7) resulting therefrom.
10. Domestic appliance (1) according to one of claims 1 to 9, characterised in that the monitoring facility (2) is a microcontroller.
11. Domestic appliance (1) according to one of claims 1 to 10, characterised in that the monitoring facility (2) is designed to recognize a shift in the potential of the safety relay feedback signal (9).
12. Domestic appliance (1) according to one of claims 1 to 11, characterised in that the error status of the domestic appliance (1) has one of the error statuses: an error status of one of the heating elements (3, 4), an error status of both heating elements (3, 4), an error status of a safety relay (8), an error status of an operating relay (5, 6) and/or a faulty connection of one of the heating elements (53, 4) to the protective conductor (PE).
13. Method for monitoring a domestic appliance (1) which has at least two heating elements (3, 4), wherein one respective heating element (3, 4) of the at least two heating elements (3, 4) is coupled by way of a respective first node (K1, K2) to a respective operating relay (5, 6) for actuating the respective heating element (3, 4), with:

    provision (201) of a shared operating relay feedback signal (7) by way of a feedback facility (FB), to which the first nodes (K1, K2) are coupled with high resistance, and

    monitoring (202) the provided operating relay feedback signal (7) in order to recognize an error status of the domestic appliance (1).
14. Method according to claim 13, characterised in that the at least two heating elements (3, 4) are switched off when the shared operating relay feedback signal (7) is provided.
15. Computer program product which triggers the performance of the method according to claim 14 on a program-controlled facility.

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