JPH0425839B2 - - 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 takes advantage of the fact that induction from a commercial power source occurs via stray 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, and a core wire. 10 and shield member 11
a shielded wire 9, one end of which is connected to the electrode 8, and which is electrostatically shielded by applying an appropriate potential to the shielding member 11; and the core of the shielded wire 9. A load resistor 15 is inserted via a capacitor 14 between the other end of the line 10 and a reference potential section 12 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. A water level detection device for a washing machine is constituted by a determining section 17 that determines that the water level has reached the electrode portion when the above conditions are satisfied. 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 the proposed method, the measures are perfect for the electrode 8 and the core wire 10 of the shielded wire 9 that connects it, but the measures are taken for the shield member 11 of the shielded wire 9. was insufficient, and there was a risk of electric shock from the water if the coating was torn and submerged in water.

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 whose surface is covered with an insulating layer having an appropriate thickness. Consisting of a single electrode, a core wire, and a shield member, one end of the core wire is connected to the electrode, and the shield member is connected to a reference potential section having an appropriate reference potential via a capacitor or a resistor. A shielded wire is inserted directly or via a capacitor between the other end of the core wire of the shielded wire and the reference potential section, and is connected to the wiring inside the washing machine from the electrode through a stray capacitance. A load resistor that detects a leaking current, an induced electromotive force detector that detects an induced electromotive force generated in this load resistor, and an induced electromotive force that is generated in the load resistor in response to the output of this induced electromotive force detector. The water level detection device for a washing machine includes a determination unit that determines that the water level has reached the electrode portion when the water level is equal to or higher than a predetermined level.

Effect With the above configuration, when the water level reaches the electrode position, the entire water is capacitively coupled to the electrode via the electrical insulating layer, so that the induced electromotive force from the commercial power source induced from the wiring of the motor etc. is applied to the load resistance. This can be used to detect when the water level has reached the water level. Furthermore, since the shield member of the shield wire is connected to the reference potential section via the capacitor or resistor, it is possible to eliminate the risk of electric shock when the sheath of the shield wire is torn.

Embodiment FIG. 1 shows an embodiment of the present invention. Note that the same members as in the configuration of FIG. 4 shown in the prior art are given the same numbers. 1 is a washing tub, 2 is a pulsator,
3 is a driving means for driving the pulsator 2. 4
is a communication part, which is provided on the side wall of the washing tub 1, through which water from the washing tub 1 is guided through the slit 5,
The water level is the same as that of 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 a commercial power source 6 to control the drive means 3 and notify the user. Power is supplied from the (+) and (-) terminals of the control unit 7 shown in FIG. 1 to the water level detection device 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 be matched with one side of the power supply line since the control section 7 controls the energization to the driving 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.

Reference numeral 9 denotes a shield wire, the core wire 10 of which is connected to an electrode, and the shield member 11 is connected via a capacitor 12 to a reference potential section 13, that is, the ground of the circuit. A capacitor 14 is connected to the core wire 10 of the shielded wire 9, and a load resistor 15 is connected between the capacitor 14 and the reference potential section 13. 16 is an induced electromotive force detection section, and a load resistance 15
The induced electromotive force from the commercial power supply 6 to the electrode 8 generated at both ends of the electrode is amplified, rectified, and smoothed, and its level is detected. 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 judgment section 17 is connected to the control section 7, and the induced electromotive force detection section 16
The power to the determination unit 17 is supplied from the control unit 7.

The reason why the shield wire 9 is used here is to remove unnecessary induction picked up by the wiring when detecting the induced electromotive force. Although the shielding effect is somewhat reduced by inserting the capacitor 12, the capacitance value of 470 pF is adopted as a practical value, and the shielding effect is maintained.

Furthermore, by inserting this capacitor 12, even if the shielding member 11 were to come into contact with the water in the washing tub 1 due to the sheathing of the shield wire 9 and the user touching this, the current limiting effect is large (100V (approximately 15μA even if commercial AC is directly applied)
Therefore, there is no risk of electric shock.

Next, the structure of the electrode 8 will be explained with reference to FIG.

FIG. 2a is a plan view of the electrode 8 viewed from above;
FIG. 2b shows its XX' cross section. In the figure, 18 is the conductor part of the electrode 8, and the shield wire 9
The core wires 10 are connected. 19 is the conductor part 18
It is an electrically insulating layer that covers the surface of the This electrical insulating layer 19 is provided so that the conductor portion 18 of the electrode 8 does not come into direct contact with water. This is because if the conductor portion 18 directly comes into contact with water, there is a risk of electric shock if the user comes into contact with the water when the capacitor 14 is short-circuited due to some kind of failure.

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). Even if a commercial current 6 of 100 V is applied directly between the conductor portion 18 and water, the current generated by this is about 10 μA, so there is no risk of electric shock.

The operation of water level detection will be explained. Figure 3 shows the principle diagram. In the figure, reference numeral 20 denotes a power supply circuit, which represents a power supply for the circuit generated in the control section 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 Figure 1, load resistance 1
5 is connected to the reference potential unit 13, and one power line of the commercial power supply 6 is connected to the positive power supply side of the circuit, so that the voltage drop due to the power supply circuit 20 matches the power supply voltage of the circuit. 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 opposite side of the electrode 8 and the power supply line is the first
As shown in the figure, the driving means 3 is connected to the driving means 3 by a straight capacitance through wiring around the driving means 3. 21 in FIG. 3 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 _p , 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 _p , where ω=2π( is the frequency of the commercial power supply 6). V〓 _s = 100 [V _rns ], R _L = 100 [KΩ],
Assuming that C _p = 1000 [pF], C _C = 280 [pF], = 50 [Hz], if the power supply 8 is not in contact with water (C _s = 1 [pF]
The amplitude of V〓 _r is about 4.4 mV, when they are in contact (C _s = 100
[pF]) is 305mV.

The induced electromotive force detection section 16 amplifies, rectifies, and smoothes this induced electromotive force _Vr , and the judgment section 17 judges whether this is above a predetermined level. In this example
When the amplitude of V〓 _r becomes 100 mV or more, it is determined that the part of the electrode 8 has reached the water level. 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 swings directly to 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.

Further, as mentioned above, the electrode 8 has an electrically insulating layer 1
9 is provided, providing double safety measures. Note that this capacitor 14 may be omitted if the electrode 8 is sufficiently safe with only the electrical insulating layer 19. However, in that case, the thickness and material of the electrical insulating layer 19 must be carefully considered.

Furthermore, as described above, the shield member 11 of the shield wire 9 also has a double safety measure in case the covering is broken by inserting the capacitor 12. Also this capacitor 1
2, the same effect can be obtained by using a resistor having the same impedance.

Effects of the Invention As described above, according to the present invention, by connecting the shield member of the shield wire to the reference potential part through the capacitor or resistor, the sheath of the shield wire is torn due to some kind of destruction, and the shield member Electric shock can be prevented even if exposed.

[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 inventors. 8... Electrode, 9... Shield wire, 10... Core wire, 11... Shield member, 13... Reference potential section, 12, 14... Capacitor, 15... Load resistance, 16... Induced electromotive force detection Part, 17... Judgment part, 18... Conductor part, 19... Electrical insulating layer.

Claims (1)

[Claims] 1. A single electrode provided at an appropriate position to detect the water level of a washing tub and whose surface is covered with an insulating layer having an appropriate thickness, a core wire, and a shield member. a shield wire configured such that one end of the core wire is connected to the electrode, and the shield member is connected to a reference potential section having an appropriate reference potential via a capacitor or a resistor, and the core of the shield wire. A load resistor is inserted directly or via a capacitor between the other end of the wire and the reference potential section, and detects the current leaking from the electrode to the wiring inside the washing machine via the stray capacitance; an induced electromotive force detection section that detects an induced electromotive force generated in a load resistor; A water level detection device for a washing machine that includes a determination unit that determines when the water level has reached a certain part. 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 source. 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.