JPH05184777A - Water level detector for washing machine - Google Patents

Abstract

PURPOSE:To enable highly sensitive detection of a water level free from effect of variations in electric parts, temperature and the like by performing a detection of the water level by an interference wave between an oscillation wave of an oscillation circuit and a resonance frequency component of a resonance circuit appearing only when water in a washing tank does not reach a water level detecting section. CONSTITUTION:An oscillation circuit 5 containing a first coil 1 is set in addition to a washing tank 11 and a resonance circuit 10 made up of the second coil 2 inductance connected to the first coil 1 and a 3 is mounted on the washing tank 11. A resonance frequency of the resonance circuit 10 is set to approximate an oscillation frequency of the oscillation circuit 5 and an output of the oscillation circuit 5 is made to contain an interference wave which is generated by interference between an oscillation wave thereof and a resonance frequency component. The capacitor 3 has a pair of electrodes 4 connected in parallel as water level detecting section and when water in the washing tank 11 reaches the pair of electrodes 4, resonance conditions of the resonance circuit 10 break to vanish the resonance frequency component. Thus, with the stoppage of the interference wave, the water level reaching a specified value is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a washing machine water level detecting device for detecting the water level in a washing tub of a washing machine.

[0002]

2. Description of the Related Art A fully automatic washing machine used in a general household has a large number of holes in its peripheral wall and covers the circumference of the spin-drying tub that rotates during spin-drying and the role of a water receiver during rinsing and rinsing. There is a two-tab structure that is composed of a fixed water tank (outer tank) and a one-tab structure that has a washing and spin-drying tank that has a non-perforated peripheral wall except at least the upper end and has no outer tank. is there. The one-tub structure washing machine has advantages that the amount of water used is small and the volume of the washing machine can be reduced.

The operation of any of the above washing machines is roughly divided into three steps: washing, rinsing, and dehydration.
Water level control such as water supply and drainage is performed during the operation of these three strokes. Regarding taking out the information on the water level in the washing tub, which is indispensable for controlling the water level, since the outer tub is fixed in the 2-tab structure, the water level is communicated outside the outer tub via the air communicating with the outer tub. The mainstream method is to determine the water level from the pressure of water by providing a pipe for deriving the pressure of the water by connecting the pipe to a diaphragm type pressure sensor.

On the other hand, in the one-tab structure washing machine, it is difficult to derive the pressure because the washing / dehydrating tank from which the water level information is to be rotated rotates, and the same system as the two-tab structure is used. I can't. For this reason, a method has been adopted in which information on the water level can be transmitted even if a spatial gap is provided between the washing tub and the washing tub. Among them, a water level detection device of the type that transmits information on the water level in the washing tub by inductance coupling is considered.

FIG. 6 shows a first conventional example utilizing such inductance coupling. In the figure, 1
1 is a washing tub, 12 is water, and outside the washing tub 11, the first
An oscillating circuit 14 including the coil 13 and a rectifying circuit 15 that rectifies an oscillating wave of the oscillating circuit 14 and outputs a DC voltage are installed. On the other hand, in the washing tub 11, the first coil 13
A resonance circuit composed of a second coil 16 and a capacitor 17 which are inductively coupled with is attached. Further, a ceramic vibrator 18 installed at a predetermined height position in the washing tub 11 is connected in parallel to the capacitor 17.

Utilizing the fact that the Q of the ceramic vibrator 18 varies depending on the presence or absence of water 12 up to a predetermined height position in the washing tub 11, that is, whether or not the ceramic vibrator 18 is in contact with the water 12. Then, the water level in the washing tub 11 is detected by detecting the change in the oscillation frequency of the oscillation circuit 14 including the ceramic vibrator 18 and the inductance coupling portion of the first coil 13 and the second coil 16. ing. FIG. 7A shows that the ceramic vibrator 18 has water 12
Shows the oscillating frequency of the oscillating circuit 14 and the DC voltage output of the rectifying circuit 15 when they are not in contact with each other. FIG. The DC voltage output of circuit 15 is shown.

In the first conventional example, even if a small amount of water 12 is attached, the resonance frequency fluctuation of the ceramic vibrator 18 can be surely caused, and the responsiveness in that sense is good. On the other hand, there is a risk of erroneous detection due to the attachment of one or two drops of water due to the scattering of the water 12.

FIG. 8 shows a second conventional example using inductance coupling. In this conventional example, the washing tub 11
A pair of electrodes 19 is installed at a predetermined height position inside the
A pair of electrodes 19 is connected in parallel with the capacitor 17 in the resonance circuit.

This prior art example utilizes the fact that the conduction state between the pair of electrodes 19 changes depending on the presence or absence of water, and the oscillation circuit 1 including the first coil 13 is used.
The oscillating wave determined by 4 is canceled when the first coil 13 and the second coil 16 are sufficiently strongly coupled. When there is water between the pair of electrodes 19, the canceling state is canceled by the change in conductivity. Therefore, as shown in FIG. 9A, the oscillator circuit 14 is provided until the water 12 reaches the pair of electrodes 19.
Nothing appears in the output of, but as shown in FIG.
When the water 12 reaches the pair of electrodes 19, an oscillation waveform determined by the oscillation circuit 14 including the first coil 13 appears.
Thereby, the water level in the washing tub 11 is detected.

[0010]

In the first conventional example, erroneous detection may occur even if one or two drops of water adhere to the ceramic vibrator due to water splashing or the like. Also,
Both the first conventional example and the second conventional example are the first and second examples.
This is effective only when the coupling between the coils is sufficiently strong, and particularly in the second conventional example, if the distance between the two coils is increased due to the displacement of the coils, the influence of the resonance circuit on the oscillation circuit is significantly reduced.

Considering the position where the second coil is attached to the washing tub, particularly in the case of a washing liquid having a high detergent concentration and a high electric conductivity, the magnetic field of the coil causes the movement of mobile ions, and the influence of the magnetic field thereby. Therefore, the transmission efficiency of water level information decreases. For this reason, the mounting position of the second coil on the washing tub is preferably a place where the washing liquid is unlikely to be splashed during drainage or dehydration, and the upper end of the washing tub is preferable. On the other hand, since the washing tub is fixed only by the rotating shaft at the center of the bottom, when the second coil is attached at a position such as the upper end, which is far from the fixed shaft, the first coil depends on the amount of laundry and the processing accuracy. , There is a high possibility that the distance between the second coils will shift.

Now, the relation between the first and second inter-coil distances and the sensitivity is taken by taking the ratio of the DC voltage output with and without water in the pair of electrode parts, which are the water level detecting parts, as the sensitivity. Then, the point where the distance is zero has the highest sensitivity, and the sensitivity decreases remarkably as the distance increases (comparative example in FIG. 4 described later). As described above, when the distance between the first and second coils is long, the influence of the resonance circuit is weakened and the sensitivity is lowered.
When there is no water, there is a possibility that it will be judged that there is water. In order to avoid this, the boundary value of the output for judging the presence or absence of water is set higher, and if the output is lower than this, it is judged that there is no water, and if it is high, it is judged that there is water, but this time there is water. In case of, it becomes difficult to judge. Since the inductance coupling is due to the change in the number of magnetic fluxes generated by the first coil passing through the second coil, the decrease in sensitivity is caused by factors other than the distance between the first and second coils, such as electrical It is also likely to occur due to fluctuations in the characteristics of parts, fluctuations in magnetic flux caused by fluctuations in characteristics due to temperature changes, and the like.

The present invention has been made in view of the above,
It is an object of the present invention to provide a water level detection device for a washing machine, which is capable of detecting water level with high sensitivity with little fluctuation in sensitivity due to the first and second coil distances and temperature.

[0014]

In order to solve the above problems, the present invention provides an oscillation circuit including a first coil mounted outside a washing tub, and an inductance circuit attached to the washing tub and the first coil. A resonance circuit including a second coil to be coupled and having a resonance frequency close to the oscillation frequency of the oscillation circuit; and an interference wave extracting means for extracting an interference wave between the resonance frequency component of the resonance circuit and the oscillation wave of the oscillation circuit. And a water level detection unit which is installed at a predetermined height position in the washing tub and is connected to the resonance circuit to cause a collapse of the resonance condition in the resonance circuit when water is detected.

[0015]

In the above structure, when the water in the washing tub does not reach the water level detecting portion, a part of the magnetic flux generated in the first coil by the oscillating wave of the oscillating circuit penetrates the second coil, and this magnetic flux The component affects the resonance circuit including the second coil, and penetrates the first coil again as a magnetic flux including the resonance frequency component. The magnetic flux component that has not penetrated the second coil includes the oscillation frequency of the oscillation circuit as it is. Therefore, magnetic fluxes of two kinds of frequency components penetrate through the first coil, and two kinds of frequency components exist in the oscillation circuit. Since the two types of frequency components have close values, they interfere with each other to generate an interference wave, and the interference wave is extracted from the interference wave extraction means.

When the water in the washing tub reaches the water level detector, the resonance condition of the resonance circuit is broken, the magnetic flux containing the resonance frequency component disappears, and the generation of the interference wave is stopped. When the interference wave is stopped, it is detected that the water level in the washing tub has reached a predetermined height.

As described above, the water level is detected by the interference wave component that appears only when the water does not reach the water level detecting portion. This interference wave is generated at a distance within a range where the magnetic flux generated by the first coil penetrates the second coil even if the first and second coils are separated by a certain distance. No decrease occurs. Therefore, if the distance between the first and second coils is within this range, fluctuations in sensitivity due to fluctuations in the number of magnetic fluxes are less likely to occur, and fluctuations in sensitivity due to variations in the characteristics of electrical components and the effects of temperature characteristics are reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 are views showing a first embodiment of the present invention.

First, the construction of a water level detecting device for a washing machine will be described with reference to FIG. An oscillation circuit 5 including the first coil 1 is installed outside the washing tub 11. On the other hand, washing tub 1
1 is a second coil that is inductance-coupled to the first coil 1.
A resonance circuit 10 including a coil 2 and a capacitor 3 is attached. The resonance frequency of this resonance circuit 10 is
The frequency is set to be close to the oscillation frequency of the oscillation circuit 5 including the first coil 1, and the output of the oscillation circuit 10 includes an interference wave generated by the interference between the oscillation wave and the resonance frequency component. It has become. Further, to the condenser 3, a pair of electrodes 4 as a water level detecting unit installed at a predetermined height position in the washing tub 11 are connected in parallel. When the water in the washing tub 11 reaches the pair of electrodes 4, the resonance circuit 1
The resonance condition of 0 is broken, the resonance frequency component disappears, and the generation of the interference wave is stopped.

The present embodiment detects that the water level in the washing tub 11 has reached a predetermined level due to the stop of the interference wave. Therefore, this interference is provided in the next stage of the oscillation circuit 5. A low-pass filter 6 is connected as an interfering wave extracting means that allows only waves to pass. A rectifier circuit 7 that rectifies the output of the low-pass filter 6 and outputs a DC voltage is connected to the next stage. The rectifier circuit 7 in the figure includes an amplifier circuit having an appropriate amplification degree.

FIG. 3 shows a concrete circuit example, and a buffer circuit 8 is connected between the oscillation circuit 5 and the low-pass filter 6.

Next, the operation of the present embodiment constructed as described above will be described with reference to FIGS.

When the water 12 in the washing tub 11 does not reach the pair of electrodes 4, the oscillation circuit 5 including the first coil 1
Oscillates an oscillating wave of frequency f ₄ . A part of the magnetic flux generated in the first coil 1 by this oscillating wave penetrates the second coil 2, the magnetic flux component affects the resonance circuit 10, and the first coil is again converted into the magnetic flux including the resonance frequency f ₅ component. 1
Pierce The magnetic flux component that has not penetrated the second coil 2 includes the oscillation frequency f ₄ of the oscillation circuit 5 as it is. Therefore, the first coil 1 has two frequency components f ₄ and f ₅
The magnetic flux of is penetrated, and the oscillation circuit 5 has two kinds of frequency components f ₄ and f ₅ . Since the two frequency components f _4, f ₅ is the value close, interference wave component f ₆ occurs interfere with each other, only the interference component f ₆ is extracted from the low pass filter 6 is amplified appropriately After that, the DC voltage is output from the rectifier circuit 7 (see FIG. 2).
(A)).

When the water 12 in the washing tub 11 reaches the pair of electrodes 4, the pair of electrodes 4 is short-circuited due to the conductivity of the water 12, and the resonance condition of the resonance circuit 10 is broken and the resonance frequency. The component f ₅ disappears. As a result, the interference wave component f ₆ also disappears, and the oscillation frequency f ₇ (f ₄ <f ₄ <
Only the oscillating wave of f ₇ <f ₅ ) appears. Since the low-pass filter 6 cuts off this oscillation wave, an extremely low DC voltage is output from the rectifier circuit 7 and it is detected that the water level in the washing tub 11 has reached a predetermined height (FIG. 2 (b)).

As described above, in this embodiment, since the water level is detected by the presence or absence of the interference wave component f ₆ that appears only when the water 12 does not reach the pair of electrodes 4, this interference wave component f ₆ Can be sufficiently amplified to increase the sensitivity.

Further, as shown in FIG. 4, the first coil 1
And the distance between the second coil 2 and the second coil 2, the generated magnetic flux of the first coil 1 penetrates the second coil 2,
For example, as shown in FIG. 1B, the first and second coils 1 and 2 are circular and have the same diameter, the planes formed by the two coils 1 and 2 are parallel to each other, and the center lines perpendicular to them are overlapped. Under such conditions, the coil diameter should be 10
If the distance is within the range of about 50% to 50%, as shown by the characteristic line a in FIG. Therefore, if the distance is within this range, the sensitivity is unlikely to change due to the number of magnetic fluxes, so that the sensitivity is not deteriorated due to the characteristic variations of the electric parts and the influence of the temperature characteristics.
On the other hand, as a comparative example, in the conventional example shown by the characteristic curve b in FIG. 10A, the sensitivity is remarkably lowered as the distance between the first and second coils increases. Further, in this conventional example, since the ceramic oscillator is not used in the water level detection unit, erroneous detection due to water scattering does not occur.

Next, FIG. 5 shows a second embodiment of the present invention. In this embodiment, three water levels in the washing tub 11 can be detected.

The washing tub 11 is provided with three resonance circuits composed of three sets of second coils and capacitors 2a and 3a, 2b and 3b, 2c and 3c, and each resonance circuit has a washing tub. A pair of electrodes 4a and 4b, 4a and 4c, 4a and 4d installed at required height positions in 11 are connected. In this embodiment, the first coil 1 is sequentially moved so that it can be connected to the first coil 2a or 2b or 2c at the water level to be detected. If it is difficult to move the first coils 1, the first coils may be installed in the same number as the second coils.

[0030]

As described above, according to the present invention,
Since the water level is detected by the interference wave between the oscillation wave of the oscillation circuit and the resonance frequency component of the resonance circuit, which appears only when the water in the washing tub does not reach the water level detection unit, the first and second coil intervals are set. Even if the distance is a certain distance, an interference wave can be generated as long as the generated magnetic flux of the first coil is within a range that penetrates the second coil, and the remarkable difference due to the distance between the first and second coils There is no reduction in sensitivity. Therefore, there is little variation in the sensitivity due to the distance between the first and second coils, variations in the characteristics of electrical components, and temperature, and water level detection can always be performed with high sensitivity.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a water level detection device for a washing machine according to the present invention.

FIG. 2 is a diagram showing output characteristics and the like of the first embodiment.

FIG. 3 is a diagram showing a specific circuit configuration example of FIG.

FIG. 4 is a diagram showing a relationship between first and second inter-coil distances and sensitivity in the first embodiment together with a comparative example.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a first conventional example of a water level detection device for a washing machine.

FIG. 7 is a diagram showing output characteristics and the like of a first conventional example.

FIG. 8 is a configuration diagram showing a second conventional example.

FIG. 9 is a diagram showing output characteristics and the like of a second conventional example.

[Explanation of symbols]

 1 1st coil 2 2nd coil 4 A pair of electrodes (water level detection part) 5 Oscillation circuit 6 Low pass filter (interference wave extraction means) 10 Resonance circuit 11 Washing tub

Claims (1)

[Claims] 1. An oscillating frequency of the oscillating circuit, which includes an oscillating circuit including a first coil attached outside the washing tub and a second coil attached to the washing tub and inductance-coupled to the first coil. A resonance circuit having resonance frequencies close to each other, an interference wave taking-out means for taking out an interference wave of the resonance frequency component of the resonance circuit and an oscillation wave of the oscillation circuit, and installed at a predetermined height position in the washing tub. A water level detection device for a washing machine, comprising: a water level detection unit that is connected to the resonance circuit and causes the resonance circuit to break the resonance condition when water is detected.