JPS6392393A - Water level detector of washing machine etc. - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

BACKGROUND OF THE INVENTION Conventionally, a pressure switch has been commonly used as a means for detecting the water level in a washing machine. This method using a pressure switch converts water level into pressure and opens and closes contacts by the movement of a diaphragm.

Problems to be Solved by the Invention However, since this pressure switch has contacts, there are problems with electrical reliability such as poor switching life and poor continuity due to corrosion, and there are also problems with moving parts such as diaphragms. Therefore, it was necessary to consider mechanical durability.

3. The object of the present invention is to provide a water level detection device for a washing machine that eliminates all of these problems.

Means for Solving All Problems In order to achieve the above objects, the present invention provides an electrode which can be held in a suitable position and whose entire surface is covered with an electrically insulating layer having a suitable thickness to detect the water level in a washing tub; A shielded wire consisting of a core wire and a shield member, one end of the core wire being connected to the electrode and electrostatically shielded by applying an appropriate potential to the shield member; A load resistor inserted directly or via a capacitor between the other end and a reference potential section having an appropriate reference potential, an induced electromotive force detection section that detects the induced electromotive force generated in this load resistance, and The induced electromotive force generated in the load resistor in response to the output of the electromotive force detection section is below a predetermined level.
A water level detection device for a washing machine is constituted by a determining section that determines that the water level has reached the electrode portion when the condition is 2.

When the water level reaches the position of the electrode with the configuration described in 2.2 above, the entire water is capacitively coupled to the electrode via the electrical insulation layer, so the induced electromotive force from the commercial power source induced from the wiring of the motor etc. becomes a load. This occurs in resistance, which can be used to detect when the water level has been reached. By providing an electrically insulating layer on the gray electrode, it is possible to provide a water level detection device with improved safety against electric shock.

Embodiment FIG. 1 shows an embodiment of the present invention. 1 is a washing tub, 2 is a pulsator, and 3 is a potential for driving the pulsator 2. A commercial power supply 6 serves as a power source for the entire embodiment. Reference numeral 7 denotes a control section which performs all operational control of the entire embodiment, is supplied with power from a commercial power source 6, and controls the driving means 3 and notifies the user. 1st
Power is supplied from the (+) and (-) terminals of the control unit 7 shown in the figure to the water level detection device that will be described below. ! f, the octopus (→ terminal is connected to have the same potential as one side of the commercial power supply 6. This is done by the control section 7 using a triac to control the energization to the drive means 3. This is also because the circuit voltage of the section 7 itself needs to match one side of the entire power supply line.

Reference numeral 8 denotes an electrode fixed within the communication portion 4 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 shielded wire, one end of which is connected to the electrode 8, and the shield member 11 is connected to the reference potential section 12, that is, the ground of the circuit. 13 is a capacitor,
One end thereof is connected to the other end of the core wire 10 of the shielded wire 9. A load resistor 14 is connected between the other end of the capacitor 13 and the reference potential section 12. Reference numeral 15 denotes an induced electromotive force detection unit, which is connected to the connection point between the load resistor 14 and the capacitor 13, and amplifies, rectifies, and smoothes the induced electromotive force generated at both ends of the load resistor 14 from the commercial power supply 6 to the electrode 8. Detect the level. Reference numeral 16 denotes a determination unit which receives the output of the induced electromotive force detection unit 15 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 16 is sent to the control section 7.
The induced electromotive force detection section 15 and the judgment section 16 are supplied with power from the control section 7 .

The reason why the shield wire 9 is used here is to remove all unnecessary induction picked up by the wiring when detecting the induced electromotive force.

FIG. 2 shows the structure of the electrode 8. FIG. 2(a) is a plan view seen from the top, and FIG. 2(b) is a sectional view taken along the line x-x'. 17 is the conductor part of the electrode 8, and the core wire 1 of the shield wire 9
Connected to 0. 18 is an electrically insulating layer covering the surface of the conductor portion 17. This electrical insulating layer 18 is provided so that the conductor portion 17 does not come into direct contact with water. This is because if the conductor portion 17 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 13 is short-circuited due to some kind of failure.

When the electrode 8 contacts the water surface, the conductor portion 17 and the water are capacitively coupled by the electrical insulating layer 18 . This capacitance is the conductor part 1
7 has a diameter of 3 cm, the thickness of the electrically insulating layer 18 is 01mm, and the material of the electrically insulating layer 18 is vinyl chloride (relative dielectric constant of 45), which is approximately 280 pF.

Even if 10OV of the commercial power supply 6 is directly applied between the conductor part 17 and water, the current generated by this is about 10μ8, so electric shock is caused by contact between the electrode 8 covered with the electrically insulating layer 18 and the water. There is no danger at all.

Next, the operation of water level detection will be explained. Figure 3 shows the principle diagram. That is, 191"j power supply circuit indicates the power supply of the circuit generated in the control unit 7.6,1
3.14 are the commercial power supply, capacitor, and load resistor shown in Figure 1, and are all given the same numbers. In FIG. 1, the load resistor 14 is connected to the reference potential section 12, 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 19 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 100 volts of the commercial power supply 6. In other words, the potential of the reference potential section 12 substantially matches the potential of one side power line of the commercial AC 6.

On the other hand, the electrode 8 and the opposite side of the power supply line are coupled by a stray capacitance through wiring of three drive means as shown in FIG. 20 in FIG. 3 indicates this stray capacitance. In addition, 21 is an electrode 8
The capacitance due to the electrical insulating layer 18 is shown.

When the electrode 8 is not in contact with the water in the washing tub 1, the stray capacitance 2o 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 power supply 6 is divided by 8, and the resistance of the load resistor 14 is R.
L, capacitance of capacitor 13 00, stray capacitance 2o capacitance 'icB, capacitance due to electrical insulating layer 18 2
1 is Cc, the induced electromotive force generated across the load resistor 140 is expressed by ω-2πfcf (the frequency of the commercial power supply 6). V,=1oo(Vrm,),RL
=100 [Kjl], C0=1000 (pF), CC
= 280 (p F ], f = 50 [Hz] 9 He-
7, when the electrode 8 is not in contact with water (Cs = 1
(pF)] The amplitude of i is approximately 4.4 mV, and when they are in contact (Cs = 100 [pF]), it is 305 mV.

The induced electromotive force detection section 15 amplifies, rectifies, and smoothes this induced electromotive force vr, and the judgment section 16 judges whether this is above a predetermined level. In this example, the amplitude of vr is 100 m
When the water level exceeds V, it is determined that the water level has reached the electrode 8 portion. In this way, it is possible to detect the arrival of the water level during water supply.

In this embodiment, the capacitor 13 is 1000 pF, and its impedance is negligibly small compared to the stray capacitance 2o. In addition, if the induced electromotive force detection unit 15 is short-circuited due to some kind of failure and the potential of the power supply line is applied to the capacitor 13 as it is, the user temporarily
Even if you touch the conductor part 17 directly, the current that flows is about 40 μ8 at worst, so there is no risk of electric shock. Therefore, by inserting this capacitor 13, measures against electric shock can be taken regardless of the detection sensitivity.

Page 10/Furthermore, as mentioned above, since the conductor portion 17 is covered with the insulating layer 18, a double safety measure is taken, and the safety is extremely high. Note that the capacitor 13 has an electrical insulating layer 18
Since the effect of this can be sufficient as a countermeasure against electric shock, safety can be ensured even without special measures.

Effects of the Invention As described above, the present invention provides a non-contact, non-moving part water level detection device that dramatically improves safety against electric shock by providing an electrical insulating layer on the electrode. can do.

Further, by inserting a capacitor in series with the electrode, a double safety structure can be achieved, and a water level detection device with higher reliability and safety can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the water level detection device for a washing machine according to the present invention, and FIGS. 2(a) and (b) are a plan view and a side cross section showing the structure of the electrodes of the water level detection device for the washing machine. FIG. 3 is a diagram showing the principle of the water level detection device of the washing machine. 8... Electrode, 9... Shield wire, 1o
... Core wire, 11 ... Shield member, 12
...Reference potential section, 13... Capacitor, 14... Load resistance, 15... Induced electromotive force detection section, 16... Judgment section, 17... Conductor portion, 18... Electrical insulating layer. Name of agent: Patent attorney Toshio Nakao and 1 other person f-
g sinker e tank 2 --- pal e-, y 4-advance letter 8-' to pole f3 ---gon shoin η- 14-load''A resistance ■ 5 faction

Claims (3)

[Claims] (1) Consisting of an electrode held at an appropriate position to detect the water level of the tank and whose surface is covered with an electrically insulating layer having an appropriate thickness, a core wire, and a shield member, one end of the core wire is connected to the electrode, and is electrostatically shielded by applying an appropriate potential to the shielding member; and a reference potential portion having an appropriate reference potential with the other end of the core wire of the shielding wire. A load resistor inserted directly or through a capacitor, an induced electromotive force detection unit that detects the induced electromotive force generated in this load resistance, and an induced electromotive force detection unit that detects the induced electromotive force generated in the load resistance, and a A water level detection device for a washing machine, comprising a determination unit that determines that the water level has reached the electrode portion when the induced electromotive force generated is equal to or higher than a predetermined level. (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 to substantially match 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.