JPH0422118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a water level detection device for detecting the water level in a tank of a washing machine, a dishwasher, or the like.

BACKGROUND ART Conventionally, a pressure switch has been used in a water level detection device for detecting the water level in a tank of a washing machine, a dishwasher, or the like. This pressure switch utilizes the fact that the pressure in the air trap that communicates with the bottom of the tank is correlated with the water level in the tank.The water level is converted into pressure and applied to the diaphragm, and the contact point is set depending on the size of the pressure. It was configured to open and close.

Problems to be Solved by the Invention However, the conventional configuration required contacts and movable parts, and had problems with the reliability of these parts.
Additionally, there were problems such as errors caused by converting water level into pressure. Furthermore, since it is operated mechanically, adjustments are required to reduce variations in water level detection due to variations in parts.

In view of the above problems, it is an object of the present invention to improve detection accuracy and durability, and to eliminate the need for adjustment.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a unit that is arranged at a predetermined position to detect the water level of the tank and is configured to come into contact with water directly or through an insulating layer. one electrode, an induced electromotive force detection section that generates as induced noise from the commercial power supply induced in the electrode with respect to a predetermined reference potential, and an induced electromotive force detected by the induced electromotive force detection section that is generated at a predetermined level. The structure includes a determination section that determines that water has reached the electrode position when the water reaches the level above.

Function According to the above configuration, when the electrode comes into contact with water, the entire water in the tank becomes a kind of antenna, and the induced noise of the commercial power source is detected through the electrode. Therefore, the induced electromotive force detection section detects the induced electromotive force due to this noise, and if the level is sufficiently large and exceeds a predetermined level, the judgment section determines that the water level has reached the position of the electrode.

Embodiment FIG. 1 shows an embodiment of the present invention. In the figure, 1 is a washing tub, and 2 is an electrode, which are arranged in a communicating pipe path 1' whose water level is the same as the water level in the washing tub 1. 3 is an induced electromotive force detection section, 4 is a judgment section, and the electrode 2 is connected to the input section of the induced electromotive force detection section 3;
A determining unit 4 is connected to the output unit.

FIG. 2 shows the configuration of the induced electromotive force detection section 3. In the figure, 5 is an amplifier, 6 is a load resistor, 7 is an input terminal, and 8 is an output terminal. The electrode 2 is connected to the input terminal 7, and the determination unit 4 is connected to the output terminal 8. The amplifying section 5 amplifies the voltage across the load resistor 6, that is, the potential difference between the electrodes 2 with the circuit ground as a reference potential, and outputs the amplified voltage to the determining section 4.

FIG. 3 shows the output voltage of this induced electromotive force detection section 3. Figure 3a shows the state when the water level has not reached the position of the electrode 2. At this time, no voltage is generated across the load resistor 6, so the output remains at OV.
When the water level reaches the position of the electrode 2, the water in the washing tub 1 is electrically connected to the electrode 2. At this time, an induced electromotive force is generated in the load resistor 6, which is induced in the electrode 2 using the ground of the circuit shown in FIG. 2 as a reference potential, and the output voltage of the induced electromotive force detection section 3 becomes as shown in FIG. 3b. This is because the entire water in the washing tub 1 acts like a kind of antenna, and the electrode 2 detects the dielectric noise from the commercial power supply that is radiated from the wiring to the electrical load such as the motor inside the housing. Depends on what you're doing.

In order to determine the presence or absence of the induced electromotive force detected in this way, the determination unit 4 determines whether the amplitude of the output voltage of the induced electromotive force detection unit 3 is larger than Vr, as shown in FIG. 3b. ing. When it is determined that this induced electromotive force is generated, it is determined that the water level has reached the position of the electrode 2.

Note that the electrode 2 may have a structure in which it is in direct contact with water or in a structure in which it is in contact with water through an insulating layer such as a resin. electrical connection is possible.

Further, the cable between the electrode 2 and the induced electromotive force detection section 3 is electrostatically shielded using a shielded wire in order to eliminate the influence of unnecessary radiation.

In this embodiment, there is a large difference in the amplitude of the induced electromotive force between the case of only the electrode 2 and the case of the electrode 2 and the entire water, so that stable water level detection is possible.

Although the present embodiment has been described in the case of a washing machine, it can also be applied to a dishwasher, and in short, the same effect can be achieved if used to detect the water level of a device having a tank for supplying water.

Effects of the Invention As described above, according to the present invention, water level can be detected by detecting the induced electromotive force from a single electrode. It is possible to provide a highly reliable water level detection device. In addition, there is no error when converting water level to pressure, and in essence, the determination of whether or not water has reached the electrode is made based on the difference in the detection level of the induced electromotive force. Furthermore, there is no need to make adjustments due to variations in parts.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of the induced electromotive force detection section,
FIG. 3 is a diagram showing the output voltage of the induced electromotive force detection section. 1... Washing tub, 2... Electrode, 3... Induced electromotive force detection section, 4... Judgment section.

Claims (1)

[Claims] 1. A single electrode arranged at a predetermined position to detect the water level in the tank and configured to be in contact with the water either directly or through an insulating layer, and a voltage induced in the electrode with respect to a predetermined reference potential. A washing machine comprising: an induced electromotive force detection unit that detects induced electromotive force generated as induced noise from a commercial power supply; and a judgment unit that determines that water has reached the position of the electrode when the induced electromotive force exceeds a predetermined level. Water level detection device such as.