JPS5939157B2 - Washing machine water level control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water level control device for a washing machine that uses capacitance, and particularly to one that prevents chattering caused by slight fluctuations in the water level in a washing tub.

Conventional water level detection means for washing machines is such that a hole is provided in the side wall of the washing and dehydration tank so that water accumulates at the same water level in a fixed outer tank provided around the outside of the washing and dehydration tank. Generally, the pressure switch was operated at a predetermined water level by utilizing the fact that the pressure in the air trap provided inside the tank rose as the water level in the outer tank rose.

However, this method requires a large amount of water because water is also stored in the outer tank.

In recent years, in order to conserve water, the washing and dehydrating tub has been made without holes, and water is stored only in the washing and dehydrating tub (hereinafter referred to simply as the washing tub), and the water level is detected using the water inside the washing tub and the electrodes placed outside the tub. A method has been proposed that detects when the capacitance between the two reaches a predetermined value.

However, this water level detection method using capacitance has the disadvantage that it responds to even the slightest decrease in the water level in the washing tub, causing frequent chattering when the water supply valve opens and closes during washing.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional water level control device for a washing machine, and to provide a capacitance type washing machine water level control device that does not cause chattering even when the water level fluctuates to some extent.

In order to achieve the above object, in the present invention, when the water level in the washing tub reaches a predetermined water level, the capacitance value between the water in the washing tub and the electrode outside the tub reaches a predetermined value or more. If it is detected that the oscillation circuit has started oscillating,
A capacitor of an appropriate value was connected in parallel to the capacitance, and the connection was cut off when oscillation stopped.

FIG. 1 is a cross-sectional view of a fully automatic washing machine using a water level control device based on capacitance change detection.

1 is an outer frame, 2 is a timer 3 and a water level detection circuit 4 according to the present invention
, a panel housing control parts such as a water supply valve 5, and 6 a water supply port.

The washing and dewatering tank 7 is a holeless tank made of an insulating material such as plastic and stores washing water.

Reference numeral 8 denotes an outer tank for receiving waste water from the washing and dewatering tank 7, which is made of an insulating material such as plastic, and an annular electrode 9 (outer tank electrode) made of aluminum foil or the like is attached to the upper outer periphery of the outer tank.

10 is a shielded wire that transmits the capacitance value sensed by the annular electrode 9 to the water level detection circuit 4 without being influenced by the outside.

Reference numeral 11 denotes an electric motor, and reference numeral 12 denotes a bearing cylinder section containing a clutch device, a brake device, etc., which is made of a conductor and is in electrical conduction with the washing water, and one terminal of the shielded wire 10 is attached thereto.

FIG. 2 is a schematic explanatory diagram of a water level detection circuit using capacitance change detection.

When water enters the washing/drying tank 7 made of an insulating material, the water in the tank and the bearing tube 12 become electrically conductive, so that the annular electrode 9 attached to the outer tank 8 and the washing water in the tank 7 are connected. The capacitance between the two electrodes increases as the water surface approaches the height of the annular electrode 9, and this increase is transmitted to the water level detection circuit 4 through the shielded wire 10.

FIG. 3 is a diagram showing an example of measurement of the relationship between the washing water level H (tomo) and the washing water capacitance value C3 (pF) of the annular electrode 9.

Figure 4 shows the present invention in which the increase in capacitance to a predetermined value corresponding to a predetermined water level as the water level rises is taken as the start of oscillation in the oscillation circuit, and the oscillation signal is amplified to operate the relay. FIG. 2 is a block diagram showing an example of a water level detection circuit 4 according to the present invention.

In the figure, F is an oscillation circuit, A is an amplifier circuit, R is a relay, and other symbols are the same as in FIG. 1.

Here, the relay R is combined with the timer 3, and when it is detected that the washing water level has reached a predetermined value, it closes the water supply valve 5 to stop the water supply and rotates the electric motor 11, and at the same time, the washing water and the annular electrode are connected to each other. A capacitor with an appropriate capacitance value Ca is connected in parallel to the capacitance Cs between the two.

The capacitor additionally connected in parallel is placed in the oscillation circuit F.

FIG. 5 is a detailed diagram of the water level detection circuit 4 according to the present invention.

13 is a power supply (AClooV), which is stepped down by a transformer 14, half-wave rectified by a diode 15, smoothed by a capacitor 16, and supplies a DC voltage to the transistor circuit.

In the oscillation circuit F, a transistor 22, a capacitor 19,
The coils 18 and 20 constitute a reflector-tuned anticoupling oscillation circuit.

Resistor 17 together with resistor 23 provides a fixed bias for transistor 22, but at the same time acts as an impedance inserted into the coupling circuit of coils 18 and 20.

The variable capacitor 21 is a negative feedback capacitor for canceling the influence of the capacitance inherent in the washing tub and the shield wire, and for adjusting the water level by changing the oscillation conditions of the oscillation circuit.

When the water level in the washing and dehydrating tank 7 rises and reaches the specified water level, the capacitance value C5 between the annular electrode 9 of the outer tank and the water in the washing and dehydrating tank 7 reaches point W as shown in the figure. and the bearing cylinder portion, that is, the eight ground points.

Therefore, the impedance between W and E, that is, the coil 1
Since the combined impedance of 8 and 20 decreases, the feedback current from the collector circuit to the base circuit of transistor 22 increases, making transistor 22 conductive and causing oscillation circuit F to start oscillating due to the effect of amplified feedback.

After the oscillation circuit F starts oscillating as described above, the relay contact portion 33' maintains the oscillation state even if the water level decreases to some extent and therefore the capacitance value C5 decreases. , if the oscillation is amplified by the amplifier circuit A described later and the relay 33 operates, an appropriate value Ca is applied in parallel to the capacitance C8.
This is to connect a capacitor 34 having .

When the oscillation circuit F starts oscillating, an alternating current voltage is excited in the coil 25 through the coupling between the coils 20 and 25, and this voltage is rectified by the diode 26 and the capacitor 27, causing a base current to flow through the transistor 29 of the amplifier circuit A. Transistor 29 is made conductive.

This causes a current to flow through the transistor 31 and makes the transistor 31 conductive.

2 by DC two-stage amplification by transistors 29 and 31.
The circuit operates the two-contact electromagnetic relay 33 (33').

The diode 35 is connected to the transistor 3 due to the high back electromotive force generated in the relay coil when the relay excitation current is cut off.
This is to protect 1.

Next, the operation of the relay 33 will be explained with reference to FIG.

While the water level in the tank 7 does not reach the specified water level, there is no oscillation, so the coil of the relay 33 is not energized, and the relay is in the OFF state, with the A contact in both circuits closed and the B contact open. .

In this state, the first circuit of the relay 33 supplies power to the water supply valve 5 via the timer 3 to open the valve, and water supply continues.

Contact of the second circuit of relay 33 (contact part 33' mentioned above)
) is also closed, and only the capacitance Cs between the water in the washing/drying tank 7 and the annular electrode 9 outside the tank is connected between W and E of the oscillation circuit F in FIG. ing.

However, when the water level in the tank 7 reaches the specified value and the oscillation circuit starts oscillating, the coil of the relay 33 is energized and the relay is turned on as described above, and the b contacts of both circuits are closed and the a
The contact opens.

The first circuit of the relay 33 cuts off the power supplied to the water supply valve 5 via the timer 3, and is switched to supply power to the electric motor 11, thereby starting washing.

At the same time, in the contact part 33' of the second circuit of the relay 33, the a contact opens and the b contact closes, and the capacitor 3 with an appropriate capacitance Ca
4 is connected in parallel to the capacitance C8 between the washing water and the electrode outside the tank, and the capacitance value between W and E increases to C5+Ca.

Therefore, the water level decreases slightly due to hot water during washing, and the capacity C.
Even if the value of 5 decreases from the value at the start of oscillation, the oscillation state is maintained because the capacitor Ca is added.

As a result, the opening/closing chuckling phenomenon of the water supply valve 5 is prevented.

When the water level drops considerably and the capacitance value C50a between W and E becomes below the oscillation level (due to a decrease in C3), oscillation stops.

According to the experimental results, when there is a relationship between the water level H (tomo) and the capacitance C3 (pF) as shown in Fig. 3, the capacitance value Ca of the capacitor 34 connected in parallel with C5 is 5. ~
10 pF is appropriate, and when Ca-6 pF, the water level decreases by 30
If it was within mw, oscillation did not stop.

Note that in this embodiment, it takes 2 to connect Ca in parallel to the capacitor C8.
Although a two-contact electromagnetic relay was used in the circuit, it is not necessary to use such a relay, and it is of course possible to obtain the same effect by using an electronic switch or a capacitive element other than a normal capacitor. The materials to be used are determined in such a way that costs can be reduced.

As explained above, according to the present invention, when a capacitance detection method is adopted for the water level control device of a washing machine, chattering of one relay, frequent opening and closing of the water supply valve, and the accompanying noise and accidents can be prevented. This makes the capacitance-based water level detection method practical, and provides many benefits, including significant water savings.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a fully automatic washing machine using a capacitance change detection type water level control device, Fig. 2 is an explanatory diagram of a water level detection circuit using capacitance change detection, and Fig. 3 shows the washing water level. Diagram 4 showing the relationship between the capacitance between the external electrode and the washing water inside the tank.
5 is a detailed diagram of the water level detection circuit according to the present invention, and FIG. 6 is an explanatory diagram of the relay operation of the water level detection circuit according to the present invention. 3...Timer, 4...Water level detection circuit,
5... Water supply valve, 7... Washing and dehydration tank,
8... Outer tank, 9... Annular electrode, 10.
... Shield wire, 11 ... Electric motor. 12...Bearing cylinder part, 33...Relay,
34... Capacitor.

Claims (1)

[Claims] 1. When the water level in the washing tub rises to a predetermined water level, it is detected by the increase in capacitance between the water in the washing tub and the electrode outside the tub, and a relay is activated to stop water supply, start motor operation, etc. When the water level control device of a washing machine performs the following operations, when it detects that the capacitance has reached the set value, the water level control device performs the above operations and also controls the water in the washing tub and the external electrode. A water level washing machine characterized in that a capacitor of a predetermined value is connected in parallel to the capacitance between the washing machine and the connection is cut off when the detected capacitance value significantly decreases. Control device.