JPH0422117B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a water level detection device for a washing machine.

Prior Art As a new method for water level detection in washing machines, the inventors have proposed a method that utilizes the fact that induction from a commercial power source occurs via straight capacitance when electrodes come into contact with water in the washing tub. ing. That is,
As shown in FIG. 4, an electrode 8 is held at an appropriate position to detect the water level of the washing tub 1, and whose surface is covered with an electrically insulating layer having an appropriate thickness.
A shielded wire 10 is composed of a core wire 11 and a shield member 12, one end of the core wire 11 is connected to the electrode 8, and an appropriate potential is applied to the shield member 12 to perform electrostatic shielding.
and a load resistor 15 inserted via a capacitor 14 between the other end of the core wire 11 of the shield wire 10 and a reference potential section 13 having an appropriate reference potential.
and an induced electromotive force detection section 16 that detects the induced electromotive force generated in the load resistor 15, and an induced electromotive force generated in the load resistor 15 in response to the output of the induced electromotive force detection section 16 is equal to or higher than a predetermined level. The determination unit 17, which determines that the water level has reached the electrode portion when the above conditions are satisfied, constitutes a water level detection device for a washing machine or the like. The potential of the reference potential section 13 is made to match the potential of one power supply line of the commercial power supply 6. In addition, 7 is a control part which controls the drive means 3 etc. which drive the pulsator 2 of the inner bottom part of the washing tub 1 by the signal from the determination part 17.

The operation of the water level detection device for a washing machine or the like configured as described above will be explained. That is, when the water level reaches the position of the electrode 8, the entire water is capacitively coupled to the electrode 8 via the electrical insulation layer, so that the induced electromotive force from the commercial power supply 6 induced from the wiring of the motor etc. is transferred to the load resistance 15. This occurs to detect when the water level has reached the water level. Furthermore, by providing an electrically insulating layer on the electrode, safety against electric shock was improved.

Problems to be Solved by the Invention However, in these cases, the measures are perfect for the electrode 8 and the core wire 11 of the shielded wire 10 that connects it, but the measures are insufficient for the shield member 12 of the shielded wire 10. There was a risk of electric shock if the cover was torn and the unit was submerged in water.
As a countermeasure to this problem, a method has been proposed in which the shielding member 12 is connected to the circuit through an element with sufficiently high impedance, but with this method, the shielding effect is slightly reduced, the S/N ratio is slightly degraded, and large disturbances are caused. However, there are cases where it becomes undetectable.

An object of the present invention is to provide a water level detection device for a washing machine that solves this problem.

Means for Solving the Problems In order to achieve the above object, the present invention is provided at an appropriate position to detect the water level of the washing tub, and the surface is covered with an electrically insulating layer having an appropriate thickness. Consists of a single electrode, a covered lead wire to which this electrode is connected, a core wire and a shield member,
One end of the core wire is connected to the coated lead wire, and one end is connected to the other end of the core wire of the shield wire and the shield wire, which is electrostatically shielded by applying an appropriate potential to the shield member. A load that is inserted between the other end of this capacitor and a reference potential section having an appropriate reference potential, and that detects the current leaking from the electrode to the wiring inside the washing machine via the stray capacitance. a resistor, an induced electromotive force detection unit that detects an induced electromotive force generated in the load resistance, and when the induced electromotive force generated in the load resistance upon receiving the output of the induced electromotive force detection unit is equal to or higher than a predetermined level; a part that determines that the water level has reached the area of the electrode; It is a device.

Effect When the water level reaches the electrode position with the above configuration, the entire water is capacitively coupled to the electrode via the electrical insulating layer, so the induced electromotive force from the commercial power source induced from the wiring of the motor etc. is applied to the load resistance. It is possible to detect when the water level has reached the water level. In addition, if a covered lead wire without a shielding member is constructed in a part that is easily touched by the user or may be submerged in water, the shielding member of the shielded wire may be exposed due to some kind of breakage. However, it can prevent electric shock.

Embodiment FIG. 1 shows an embodiment of the present invention. Components that are the same as those shown in FIG. 4 are given the same numbers. 1 is a washing tub, 2 is a pulsator, and 3 is a driving means for driving the pulsator 2. Reference numeral 4 denotes a communication section, which is provided on the side wall of the washing tub 1, through which the water in the washing tub 1 is guided through a slit 5, and is brought to the same water level as the washing tub 1. A commercial power supply 6 serves as a power source for the entire embodiment. A control section 7 controls the operation of the entire embodiment, and is supplied with power from the commercial power source 6 to control the driving means 3 and report to the user. Power is supplied from the (+) and (-) terminals of the control unit 7 shown in FIG. 1 to the water level detection device which will be described below. Further, this (+) terminal is connected to one side of the commercial power supply 6 so as to have the same potential. This is also because the circuit voltage of the control section 7 itself needs to match one side of the power supply line since the control section 7 controls the energization of the drive means 3 using a triac.

Reference numeral 8 denotes an electrode fixed by suitable support means for detecting the water level, and is movable in the vertical direction so that it can be placed at a position desired by the user. 9 is a covered lead wire to which the electrode 8 is connected. Reference numeral 10 denotes a shielded wire, the core wire 11 of which is connected to the covered lead wire 9. The shield member 12 of the shield wire 10 is connected to a reference potential section 13, that is, the ground of the circuit. A capacitor 14 is connected to the core wire 11 of the shielded wire 10, and a load resistor 15 is connected between the capacitor 14 and the reference potential section 13. Reference numeral 16 denotes an induced electromotive force detection section that amplifies, rectifies, and smoothes the induced electromotive force generated at both ends of the load resistor 15 from the commercial power source 6 to the electrode 8, and detects its level. Reference numeral 17 denotes a determination unit which receives the output of the induced electromotive force detection unit 16 and determines whether the magnitude of the induced electromotive force is equal to or higher than a predetermined level. The output of the determination section 17 is connected to the control section 7 , and the induced electromotive force detection section 16 and the determination section 17 are supplied with power from the control section 7 .

The reason why the shield wire 10 is used here is to remove unnecessary induction thrown away by the wiring when detecting the induced electromotive force.

FIG. 2 shows the structure of the electrode 8. In the same figure, a shows electrode 8.
is a plan view seen from above, and b is a plan view of the X-
It is an X′ cross-sectional view. In the figure, 18 is a conductor portion of the electrode 8, to which the core wire 11 of the shield wire 10 is connected. Reference numeral 19 denotes an electrically insulating layer covering the surface of the conductor portion 18 of the electrode 8. This electrical insulating layer 19 is provided so that the conductor portion 18 does not come into direct contact with water.
The electrical insulating layer 19 is provided on the surface of the electrode because
When the conductor part 18 comes into direct contact with water, the capacitor 14
This is because there is a risk of electric shock if the user comes into contact with water when there is a short circuit due to some kind of malfunction.

When the electrode 8 contacts the water surface, the conductor portion 18 and the water are capacitively coupled by the electrically insulating layer 19 . This capacitance is approximately 280 pF when the diameter of the conductor portion 18 is 3 cm, the thickness of the electrical insulating layer 19 is 0.1 mm, and the material of the electrical insulating layer 19 is vinyl chloride (relative permittivity: 4.5). The resulting current is approximately 10 μA even if 100 V from the commercial power source 6 is applied directly between the conductor portion 18 and water, so there is no risk of electric shock.

Next, the operation of water level detection will be explained. Figure 3 shows the principle diagram. Reference numeral 20 denotes a power supply circuit, which is a power supply for the circuit generated in the control unit 7.
Reference numerals 6, 14, and 15 represent a commercial power source, a capacitor, and a load resistor shown in FIG. 1, and are given the same numbers. In FIG. 1, the load resistor 15 is connected to the reference potential section 13, and one power line of the commercial power supply 6 is connected to the positive power supply side of the circuit, so the voltage drop due to the power supply circuit 20 matches the power supply voltage of the circuit. do. Since this voltage drop is about several volts, it can be almost ignored compared to the 100V of the commercial power supply 6. In other words, the potential of the reference potential section 13 substantially matches the potential of the power supply line on one side of the commercial AC 6. On the other hand, the electrode 8 and the opposite side of the power supply line are connected through the wiring around the driving means 3 by a stray capacitance, as shown in FIG. Figure 3 2
1 indicates this stray capacitance.

When the electrode 8 is not in contact with the water in the washing tub 1, the strain capacitance 21 is 1 to 2 pF, but when it is in contact with water, it reaches around 100 pF. This is thought to be because the entire water acts as the electrode of the capacitor.

Now, the voltage of the commercial AC 6 is V〓 _s , and the load resistance 15 is
R _L , the capacitor 14 is C _O , the stray capacitance 21 is C _S , and the capacitance 22 due to the electrical insulation layer 19 is
If C _C , the induced electromotive force V〓 _r generated at both ends of the load resistor 15 is V〓 _r = V〓 _s R _L /R _L +1/jωC _C +1/jωC _s +1/jωC
_O However, V〓 _s = 100 [V〓 _rns ], R _L = 100 [KΩ], C
_O
= 1000 [pF], C _C = 280 [pF], = 50 [Hz], when the electrode 8 is not in contact with water (C _s =
1 [pF]) V〓 The amplitude of _r is approximately 4.4 mV, and when they are in contact (C _s = 100 [pF]), it is 305 mV.

The induced electromotive force detection unit 16 amplifies, rectifies, and smoothes this induced electromotive force _Vr , and the determination unit 17 determines whether this is equal to or higher than a predetermined level. In this example
When the amplitude of V〓 _r becomes 100 mV or more, it is determined that the water level has reached the part of the electrode 8. In this way, it is possible to detect the arrival of the water level during water supply.

In this example, the capacitor 14 is 1000pF,
Compared to the stray capacitance 21, its impedance is negligibly small. Furthermore, even if the induced electromotive force detection section 16 is short-circuited due to some kind of failure and the user directly touches the conductor section 18 of the electrode 8 while the potential of the power supply line is directly applied to the capacitor 14, the current that flows will be 40 μA at the worst. There is no need to worry about electric shock. Therefore, by inserting this capacitor 14, it is possible to take measures against electric shock regardless of the detection sensitivity.

Furthermore, as described above, since the conductor portion 18 is covered with the electrically insulating layer 19, a double safety measure is taken, and the safety is extremely high.

In addition, for areas that may be easily touched by the user or submerged in water, the electrode 8 should be connected to the covered lead wire 9.
Since it is connected to the shielded wire 10 by
Even if the covering of the covered lead wire 9 is torn, there is no risk of electric shock at this location because the capacitor 14 is present. In other words, in the past, all of this section was made up of shielded wires, so if the covering of the shielding member was torn, there was a risk that the potential of the circuit would be directly applied to the human body. This can be avoided by constructing only the covered lead wire 9.

Also, since there is no shielding effect in this section, there is a possibility that it will be affected by external disturbances, but since this section is about 20 cm, it can be considered that there is no problem of inability to detect due to this.

Effects of the Invention As described above, according to the present invention, areas that may be touched by the user or submerged in water are
By using a covered lead wire instead of using a shielded wire, the risk of electric shock can be completely eliminated.
Furthermore, this does not reduce the shielding effect to the extent that it becomes undetectable, so it is very effective in actual use.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the water level detection device for a washing machine according to the present invention, FIGS. is a principle diagram of the water level detection device of the same washing machine, and FIG. 4 is a configuration diagram of the water level detection device proposed by the inventor. 8... Electrode, 9... Covered lead wire, 10... Shield wire, 11... Core wire, 12... Shield member, 13... Reference potential section, 14... Capacitor,
15... Load resistance, 16... Induced electromotive force detection section, 17... Judgment section, 18... Conductor section, 19...
Electrical insulation layer.

Claims (1)

[Claims] 1. This electrode is connected to a single electrode which is provided at an appropriate position to detect the water level of the washing tub and whose surface is covered with an electrically insulating layer having an appropriate thickness. A shielded wire consisting of a covered lead wire, a core wire, and a shield member, one end of the core wire is connected to the covered lead wire, and an electrostatic shield is applied by applying an appropriate potential to the shield member. , a capacitor whose one end is connected to the other end of the core wire of the shield wire, and a reference potential portion having an appropriate reference potential and the other end of the capacitor, and a strain capacitance from the electrode. A load resistor that detects the current leaking into the wiring inside the washing machine through the load resistor, an induced electromotive force detector that detects the induced electromotive force generated in this load resistor, and a a determination unit that determines that the water level has reached the electrode portion when the induced electromotive force generated in the load resistance is equal to or higher than a predetermined level; and the covered lead wire is at least easily touched by a user or submerged in water. A washing machine water level detection device used in areas where there is a possibility of 2. The water level detection device for a washing machine according to claim 1, wherein the potential of the reference potential section to which the load resistor is connected is made substantially equal to the potential of one power line of the commercial power supply. 3. The water level detection device for a washing machine according to claim 1, wherein the induced electromotive force detection section amplifies, rectifies, and smoothes the induced electromotive force generated in the load resistance.