Description A HOUSEHOLD APPLIANCE

[0001] The present invention relates to a household appliance wherein the temperature of the heated water can be measured accurately.

[0002] In household appliances, in tea, coffee machines, washers or dishwashers and the like wherein the water has to be heated to a certain temperature; the water temperature has to be detected accurately for purposes of control and safety.

[0003] In conventional applications, an NTC sensor (Negative Thermal Coefficient) is used in the chamber wherein the water is heated, the resistance of which changes, decreasing with temperature and the resistance change can be detected by means of a voltage divider circuit. Even though the use of an NTC sensor is practical and inexpensive, alternative temperature detecting methods are needed due to reasons like assembly problems, causation of electric leakage, and the nonlinearity of the resistance value.

[0004] The object of the present invention is to design a household appliance wherein the temperature of the liquids utilized during operation can be measured accurately and inexpensively without being in contact with the heated liquid.

[0005] The household appliance designed to fulfill the object of the present invention is explicated in the first claim whereas its other features are explicated in the respective claims.

[0006] In the embodiment of the present invention, the household appliance comprises a heater that heats the liquids within, a control card, connected to the heater and feeds the heater, having a measurement circuit with a resistor. Measurement the temperature of the water used in the household appliances is maintained by monitoring the current that passes over the heater that heats the water. The resistance of the heater changes with respect to the temperature of the water heated. Accordingly, the current drawn by the heater changes and the current drawn by the resistor in the circuit that feeds the heater also changes together with the heater. The temperature of the water can easily be determined by the control card that monitors this change. Consequently, the temperature of the water can be determined without putting in an extra sensor in the chamber containing the liquid.

[0007] The household designed to fulfill the object of the present invention is illustrated in attached figures, where:

[0008] Rgure 1 - is the schematic view of a household appliance.

[0009] Rgure 2 - is the schematic view of a measurement circuit.

[0010] The elements illustrated in the figures are numbered as follows:

1. Household appliance

2. Heater

3. Control card

4. Measurement circuit

5. Chamber

6. Resistor

[0011] The household appliance (1) comprises a chamber (5) wherein the liquid is contained, a heater (2) situated in the chamber (5) providing the heating of the liquid in the chamber (5), the resistance value of which changes with respect to the liquid it is situated in, and a control card (3) that regulates the operation thereof.

[0012] The control card (3) comprises a measurement circuit (4) situated outside the chamber (5), providing to determine the temperature of the heated liquid. The measurement circuit (4) comprises a resistor (6) connected parallel to the line coming from the heater (2) that does not contact the liquid in the chamber (5). In the embodiment of the present invention, the control card (3) constantly monitors the current on the resistor (6) with the help of the measurement circuit (4) for safety and control purposes, providing to correlate the current change with the temperature variation values predetermined by the producer with experimental data and to determine the liquid temperature by e.g. a micro controller (M). The resistor (6) acts as a means for measuring the temperature of water.

[0013] In the embodiment of the present invention, as the temperature of the heater (2) being in contact with liquid in the chamber (5) changes, the resistance of the heater (2) and thus the current it draws changes with respect to the temperature of the liquid it is situated in. In the meantime, the temperature and the current values also change on the resistor (6) connected to the heater (2) but not in contact with the heated liquid, and the current that flows therefrom decreases. At the same time, the current variation effect emerging on the heater (2) is monitored by the measurement unit (4) through the resistor (6) and the temperature values of the liquid that is tried to be heated are determined by the control card (3) with the normalized current variation values determined by the producer.

[0014] In an embodiment of the present invention, a resistor (6) of high sensitivity with low value (10 mW,, 20 mW,, etc) is utilized.

[0015] In the embodiment of the present invention wherein the household appliance (1) is a

washer, the heater (2) is used in heating the water necessary for washing the laundry and the washing water temperature in all phases of washing is determined by monitoring the current change of the resistor (6) connected to the heater (2). The control card (3) determines how much the heater (2) has to operate according to the determined temperature and the heater (2) is energized and/or de-energized at the required time for as long as required in the required washing phases. Consequently while heating is done by the heater (2) also the temperature of the washing water is measured sensitively and safely without using any extra sensors. Hereby, with the embodiment of the present invention, in household appliances (1) wherein the liquids contained therein are heated, heat transfer is provided with the heater (2) that heats the liquids and also measures the temperature of the heated liquid without using extra sensors. Consequently, cost advantage, ease of assembly and maintenance are provided. Furthermore, since measurement is done directly from the heat source, sensitivity of measurement values is maintained and safe operation is provided since probable electric leaks are prevented.