A HOUSEHOLD APPLIANCE WITH INCREASED SAFETY CONTROL

[0001] The present invention relates to a household appliance wherein the switches, located in the control unit, are provided to operate safely.

[0002] Components such as motor, door, valve and pump, which are located in household appliances, are generally controlled by electronic switches such as relay and triac. These switches are of vital importance in terms of providing safety since they, for example, provide the door to remain closed while the washing machine operates. Therefore, in accordance with the safety standards, a failure detection circuit, which controls whether the switch operates properly or not, is certainly situated in the switch driving circuits. However, in the situation that a failure occurs also in this failure detection circuit, the failure circuit cannot detect the failure that occurs in the switch and cannot transmit the message saying that a failure occurred, to the control unit. This situation causes a safety problem.

[0003] In the state of the art European Patent Application No EP 1308975, a microcomputer, which detects the failure in the relay, controlling whether there is a failure or not by comparing the output voltage of the relay and the threshold voltage by activating and deactivating the relay, is described.

[0004] The aim of the present invention is the realization of a household appliance wherein the switch, providing the components to be driven, is guaranteed to operate safely.

[0005] The household appliance realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof, comprises switches and detection circuits which perform the failure control of the switches.

[0006] In order to be able to detect whether a failure occurred in the detection circuit or not, the control unit does not drive the switch for a short time and controls the operation of the detection circuit. Thus, the detection of the failure existence is controlled by creating an artificial failure.

[0007] In an embodiment of the present invention, when the switch is not driven, by the change in the output signal of the detection circuit, it is inferred that a failure occurred. [0008] In an embodiment of the present invention, the switch is a triac which allows the current to flow bidirectionally.

[0009] In an embodiment of the present invention, the switch is a relay. [0010] In an embodiment of the present invention, the control unit is operated by a microprocessor. [0011] In different embodiments of the present invention, the household appliance can be a washing machine, a dryer or a dishwasher. [0012] By means of the embodiment of the present invention, the operation of the switch, the failure-free operation of which is critical in terms of safety, and of the detection circuit, which controls the failure of the switch, without any problems is guaranteed. [0013] The household appliance realized in order to attain the aim of the present invention is illustrated in the attached figures, where: [0014] Figure 1 - is the schematic view of a household appliance. [0015] Figure 2 - is the schematic view of a control unit in an embodiment of the present invention. [0016] Figure 3 - is the graph of the input signal, which provides the switch to be driven for a while and not to be driven for a while, with respect to time in an embodiment of the present invention. [0017] Figure 4 - is the graph of the output signals, which are observed when the switch is driven and not driven while the detection circuit operates normally, with respect to time in an embodiment of the present invention. [0018] Figure 5 - is the graph of the output signals, which are observed when the switch is driven and not driven while the detection circuit is faulty, with respect to time in another embodiment of the present invention. [0019] The elements illustrated in the figures are numbered as follows:

1. Household appliance

2. Component

3. Switch

4. Detection circuit

5. Control unit

[0020] The household appliance (1) comprises more than one electrically controlled component (2) such as motor, door, valve and pump, an electronic switch (3) which provides the component (2) to be turned on and off, and a detection circuit (4) which controls whether the switches (3) of the door and pump operate properly or not (Figure 1).

[0021] In the household appliances (1), the components (2) are controlled by the electronic switch (3). The switch (3) provides electricity to be supplied to the components (2) by being driven by the commands received from the control unit (5). In order that the switches (3) of the components (2) operate in a safe manner, the switches (3) are controlled by the detection circuit (4).

[0022] The household appliance (1) of the present invention comprises a control unit (5)

- which stops driving the switch (3) throughout a period of time that will not affect the operation of the component (2) the switch (3) controls, and

- which determines that there is a failure in the detection circuit (4) if the detection circuit (4) does not transmit a message saying that a failure occurred, throughout the period of time wherein the control unit (5) stops driving the switch (3).

[0023] While the detection circuit (4) operates failure-free, it controls whether the switch (3) operates properly or not, and when a failure occurs in the switch (3), it transmits a message saying that a failure occurred, to the control unit (5). In order that the detection circuit (4) can be controlled whether it operates properly or not, the control unit (5) does not drive the switch (3) for a short time, that is, creates an artificial failure in the switch (3), and controls whether the detection circuit (4) can detect the failure or not. The period of time wherein the control unit (5) does not drive the switch (3) for test purposes, is a period of time which does not change the on or off situation of the switch (3) and which does not affect the operation of the component (2). Thus, the control unit (5) can control the operation of the detection circuit (4) by not driving the switch (3) for a short time at certain periods.

[0024] If the detection circuit (4) transmits a signal regarding that the switch (3) is driven while the control unit (5) does not drive the switch (3), the control unit (5) determines that there is a failure in the detection circuit (4).

[0025] The control unit (5) controls the output signal (Vout) of the detection circuit (4) and determines that there is a problem if there is no change in the output signal (Vout) while not driving the switch (3).

[0026] In an embodiment of the present invention, when the control unit (5) detects a failure in the detection circuit (4), it terminates the program and provides a failure signal to be given. In an embodiment of the present invention, the control unit (5) drives the switch (3) by the impulse signal (Vin) oscillating between (-5V - OV) (Figure 2 and 3). The detection circuit (4) is connected to the switch (3), and when the switch (3) is driven (T1) and not driven (T2) by the control unit (5), different signals at its output (Vout) are observed (Figures 4 and 5). When the control unit (5) drives (T1) the switch (3), the output signal (Vout) of the detection circuit (4) is read as -2,5V and the detection circuit (4) transmits a no failure-message to the control unit (5) (Figures 2 and 4). When the control unit (5) receives this signal, it determines that the detection circuit (4) is not faulty. When the control unit (5) does not drive (T2) the switch (3), the input signal (Vin) of the switch (3) is OV (Figure 3). When the control unit (5) does not drive (T2) the switch (3), the output signal (Vout) becomes the impulse signal oscillating between (-5V - OV) and the detection circuit (4) transmits a message saying that a failure occurred, to the control unit (5) (Figure 4). If the control unit (5) measures the required values in the output signal (Vout) of the detection circuit (4) while driving (T1) and not driving (T2) the switch (3), it concludes that the detection circuit (4) operates properly (Figure 4).

[0027] In the situation that a resistor (R), located in the detection circuit (4), is short circuited, when the control unit (5) does not drive (T2) the switch (3), the output signal (Vout) is measured -2,5V, that is, the same value as the output signal (Vout) measured while the switch (3) is driven (T1), whereas the output signal (Vout) is required to be the impulse signal oscillating between (-5V - OV). In this situation, the detection circuit (4) detects the switch (3) as being driven although it is not, and transmits a signal as if the switch (3) is being driven (Figures 2 and 5). In this situation, since the control unit (5) does not receive the message saying that the switch (3) is not driven, from the detection circuit (4) although the control unit (5) does not drive the switch (3), the control unit (5) concludes that there is a failure in the detection circuit (4).

[0028] In the household appliance (1) of the present invention, by a safety algorithm, which is installed in the microprocessor located in the control unit (5), the switch (3) is not driven for a short time at a period, the data of which is stored in the memory of the microprocessor, and throughout this time, it is tested whether a change occurs in the detection circuit (4) or not.

[0029] In an embodiment of the present invention, the switch (3) is a triac which allows the current to flow bidirectionally (Figure 2).

[0030] In another embodiment of the present invention, the switch (3) is a relay.

[0031] In an embodiment of the present invention, the household appliance (1) is a washing machine. For example, the switch (3), which controls the door of the washing machine, is controlled by the control unit (5) by not being driven for 3 periods at every 10 seconds. This 3 period-time is much shorter than the time required for the switch (3) to change to the on position after the electricity is cut off by the switch (3) not being driven.

[0032] In another embodiment of the present invention, the household appliance (1) is a laundry dryer. In these embodiments, the component (2) is the door or the pump.

[0033] In another embodiment of the present invention, the household appliance (1) is a dishwasher. In this embodiment, the component (2) is the pump.

[0034] By means of the embodiment of the present invention, the control unit (5) is provided not to drive the switch (3) for a short time at certain periods and thus, the detection circuit (4) is provided to be controlled whether it can detect this artificial failure, created in the switch (3), or not. Thus, without making any hardware changes and increasing the cost, only by changing the software of the control unit (5), the failure-free operation of the switch (3) is guaranteed.

[0035] It is to be understood that the present invention is not limited to the embodiments disclosed above and a person skilled in the art can easily introduce different embodiments. These should be considered within the scope of the protection postulated by the claims of the present invention.