JPH034088B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a water level detection device that continuously detects changes in water level in a water tank in a washing machine or the like.

<Prior art> Conventionally, water level detection devices have used float switches, water electrodes, devices that use the weight or capacitance of water, and washing machines usually use a diaphragm-type water level detection device with the structure shown in Figure 1. is used.
In Figure 1, 1 is an aquarium, 2 is water in the aquarium 1,
3 is a drainage pipe, 4 is a drain port, 5 is an air reservoir communicating with the aquarium 1 at the bottom, 6 is a communication pipe, 7 is air,
Reference numeral 8 denotes a lid of a case described below that connects the opening 8a to the upper opening of the air reservoir 5 via the communication pipe 6, 9 a diaphragm movable valve, and 10 a case that holds the outer circumference of the movable valve 9 between the lid 8 and the lid 8. , 11 is a caulking metal fitting, 12
13 is a compression type spring inserted into the cylindrical portion of the case 10; 14 is a spring retainer that presses the spring 13 toward the movable piece 12; 15 is an adjustment screw; 16 17 is a movable contact, 17 is a normally closed contact, and 18 is an open contact. The base ends of these contacts 16, 17, and 18 are attached to the case 10, and the movable contact 16 has its tip engaged with the movable piece 12. match. In this configuration, when water 2 is poured into the water tank 1, the air 7 between the water surface in the air reservoir 5 and the diaphragm movable valve 9 is compressed and presses the diaphragm movable valve 9, and the pressure changes due to a change in the water level, i.e., inside the water tank 1. is proportional to the vertical change in the water surface. On the other hand, when the adjustment screw 15 is turned, the spring presser 14 presses the spring 13, and the spring pressure is applied to the movable piece 12, so that the pressure of the spring 13 is higher than the pressure of the air 7 until water reaches a certain predetermined water level. The pressure is greater, and neither the movable diaphragm valve 9 nor the movable piece 12 moves, so that the movable contact 16 is in contact with the normally closed contact 17. Then, when the water level reaches the specified level, air 7
The pressure overcomes the pressure of the spring 13, the diaphragm movable piece 9 and the movable piece 12 move to the left, and the movable contact 16 contacts the normally open contact 18.

In this way, the diaphragm type water level detection device
It is only possible to detect at a fixed point whether the water level mechanically set by the adjustment screw 15 has been reached, and it is not possible to continuously detect changes in the water level. Also, with this type of diaphragm type, only small stroke changes can be obtained. ,
The drawback was that water level detection could not be performed over a wide area.

<Purpose> The present invention has been made in view of the above points, and it changes the inductance of the coil by moving a magnetic body in and out of the coil in response to changes in the water level in the aquarium, and changes the water level by changing the inductance of the coil. By configuring it to detect changes, it is possible to continuously detect changes in the water level in the aquarium over a wide range.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 2 to 6. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals as in FIG.

In FIG. 2, reference numeral 19 denotes a cylindrical case made of a non-magnetic material, whose lower opening 19a communicates with the upper opening 5a of the air reservoir 5 through the communicating pipe 6, and has a stopper 19b on the inner periphery of the lower part. 20 is a permanently magnetized magnetic body, a so-called magnet, and has N and S magnetic poles at the top and bottom. 21 is a magnetic fluid that seals the gap between the magnet 20 held by the magnet 20 by its magnetic force and the inner surface of the case 19, and moves up and down inside the case 19 together with the magnet 20;
Together with this, they constitute a movable part. Reference numeral 22 denotes a coil provided on the outer periphery of the case 19, whose self-inductance changes as the magnet 20 moves in and out of the coil, and serves as a fixed part together with the case 19. 23 is a compression type spring, 24 is a spring presser that presses the spring 23 toward the magnet 20, and 25 is an adjustment screw. The magnetic fluid 21 is a liquid ferromagnetic material in which magnetic particles (ferromagnetic material) are dispersed in a solvent (base oil) with the help of a surfactant. For example, ferrite is used as the magnetic particle,
Base oils include water, hydrocarbon oil, ether,
Esters are used.

In the above configuration, when water is poured into tank 1,
Since the gap between the case 19 and the magnet 20 is sealed by the magnetic fluid 21, the air 7 between the water surface of the air pocket 5, the magnet 20, and the magnetic fluid 21 is compressed and presses the magnet 20. Therefore, if the air above the magnet 20 inside the case 19 is allowed to leak out of the case 19, the balance of force is the sum of the weights of the magnet 20, magnetic fluid 21, spring 23, and spring retainer 24 (hereinafter referred to as self-weight). ) plus the pressure of the spring 23 becomes equal to the pressure of the air 7. On the other hand, when the adjustment screw 25 is turned, the spring presser 24 presses the spring 23 and the spring pressure is applied to the magnet 20. Therefore, up to a certain water level, the sum of the dead weight and the pressure of the spring 23 is higher than the pressure of the air 7. The sum is larger, magnet 2
0 remains in contact with the stopper 19b and does not move, and the inductance of the coil 22 does not change.
When the water level exceeds a certain level, the pressure of the air 7 overcomes the sum of the pressure of the spring 23 and the sum of its own weight, causing the magnet 20 to move upward, and as a result, the magnetic fluid 21
The magnet 20 moves inside the coil 22, causing a change in inductance. still,
As the water level rises in FIG. 2, the magnet 20 moves upward and the inductance of the coil 22 increases.

Now, the water level is Hcm, the density of water is Gg/ ^cm3 , and the magnet is 20
The pressure receiving area is Scm ² and the spring coefficient of the spring 23 is Kg/
cm, the contracted length of the spring 23 is lcm, and the sum of its own weight (the sum of the weights of the magnet 20, magnetic fluid 21, spring 23, and spring retainer 24) is Mg, then the balance of forces is H・G・S=K・It is indicated by l+M. Adjustment screw 25 for a certain water level H _p
If the stroke l _p of is determined so that H _p・G・S=K・l _p +M, the inductance of the coil 22 remains at L=L _p (initial value) in the range of water level H≦H _p . In the range of water level H>H _p , the change in inductance is L-L _p ∝l-l _p ∝H-H _p and is proportional to the water level change as shown in the fourth diagram.

Therefore, if the spring coefficient of the spring 23, the pressure-receiving area of the magnet 20, and the sum of its own weight are appropriately selected, any water level H _p can be set.
is set using the adjustment screw 25, and changes in the water level above this level can be continuously detected as changes in the inductance of the coil 22.

Next, FIG. 3 is an electric circuit diagram of the water level detection device of the present invention, in which 30 indicates a detection circuit section, 31 indicates a water level display circuit section, and 32 indicates a relay drive circuit section.

In the detection circuit section 30, a comparator
IC1, resistors R1 to R6, and capacitor C1 form an oscillation circuit, coil 22, variable adjustment coil L1, and capacitor C2 form a resonant circuit, and diode D
1 and capacitor C3 constitute a rectifying/smoothing circuit, respectively. When a DC voltage is applied between points A and C, the output of the comparator IC1 repeats high and low level changes due to charging and discharging of the capacitor C1, and the output waveform is shown in FIG. Now, the output voltage of comparator IC1 is V ₁ and the voltage at point F is
Assuming V _p , V _p = 1/jWC2+1/jW(L+L1)/R6+1/jWC2+1/
jW(L+L1)×V _I =1/1+jR6×(2πf) ² (L+L1)C2−1/2πf(
L+L1) ×V _I , as shown in Figure 6, (2πf) ² (L+L1)C2=
1 is the resonance point. However, L is the inductance of the coil 22, f is the oscillation frequency of the comparator IC, R6 is the value of the resistor R6, and C2 is the capacitor C.
The value is 2. If the constants of f, L, L1, and C2 are set within the range of (2πf) ² (L+L1)C2<1, then as the inductance L of the coil 22 increases, the amplitude of the voltage V _p at point F also increases; output
Rectify V _p with diode D1 and capacitor C3.
A DC voltage signal corresponding to a change in the inductance L of the coil 22 (i.e. a change in the water level) is expressed as B.
It can be taken out to the point.

Next, the water level display circuit section 31 is a circuit section for displaying the water level in stages by changing the voltage at point B, and includes, for example, three light emitting diodes (hereinafter referred to as LEDs), and includes high, medium, and low levels. The water level is displayed in three stages. In the water level display circuit 31, if the power supply voltage between points D and E is V _S and the values of resistors R7 to R10 are R7 to R10, respectively, as the water level rises, the voltage V _B at point B becomes V _B ≧ R10 /R7+R8+R9+R10×V _S , the output of comparator IC2 becomes a low signal and LED1 lights up to indicate the low water level. When V _B ≧R9+R10/R7+R8+R9+R10×V _S , the output of comparator IC3 becomes a low signal and LED2 lights up to indicate the middle water level, and when V _B ≧R8+R9+R10/R7+R8+R9+R10×V _S , the output of comparator IC4 becomes a low signal and LED3 lights up to indicate the high water level. still,
By increasing the number of LEDs, it is possible to display water level changes almost steplessly, that is, continuously. In the figure, R11 to R13 indicate resistance.

In the relay drive circuit section 32, RY is, for example, a relay that controls a water supply valve, a water supply pump, etc., or an LED.
4 is a light emitting diode for displaying water supply, and VR is a variable resistor for setting a desired water level. now,
When the value of variable resistor VR is set according to the desired water level, if the water level is lower than the desired water level, the voltage at point B is smaller than the divided voltage between variable resistor VR and resistor R14, and the output of coparator IC5 becomes a high signal. , and transistor Q1 turns on. Then, relay RY
is in the ON state and continues water supply, and
LED4 lights up to indicate that water is being supplied.
When the water level rises to the desired level, the voltage at point B becomes larger than the voltage divided by the variable resistors VR and R14, and the output of the comparator IC5 becomes a low signal, and accordingly, the transistor Q1 is turned off. , relay RY is also turned off, stopping the water supply and turning off LED4. R15, R1 in the diagram
6 represents a resistor, and D2 represents a diode.

7 is a diagram showing the flow of magnetic lines of force, and 26 is a line of magnetic force generated when a current flows through the coil 22 at the alternating voltage shown in FIG. This results in a self-inductance of 22. Note that the cored coil self-inductance is proportional to the magnetic permeability of the magnetic core, and is expressed by the following equation.

L=π _r ²・μ・N/x However, L is self-inductance, π is pi,
r is the radius of the coil, μ is the magnetic permeability of the magnetic core, N is the number of turns of the coil, and x is the length of the coil.

27 is a line of magnetic force that comes out from the north pole of the magnet 20, enters the magnetic fluid 21, and returns to the south pole, which attracts the magnetic fluid 21 and attaches it to the magnet 20, sealing the space between it and the inner surface of the case 19. The magnetic fluid 21 allows the magnet 20 to move up and down smoothly. Therefore, by selecting a large pressure-receiving area of the magnet 20 and a small spring coefficient of the spring 23, a large amount of displacement relative to the water level can be obtained, and water level detection with high resolution performance can be performed.

As described above, in the embodiment of the present invention, the inductance of the coil 22 is changed by moving the magnet 20 in and out of the coil 22 in response to changes in the water level in the water tank 1, and the change in inductance is detected. This allows for continuous water level detection and water level display, as well as automatic water supply control.

FIG. 8 shows another embodiment of the present invention, in which the movable part is formed by a magnetic core 2 made of an unmagnetized ferromagnetic material.
8. It is composed of a joint 29 made of a non-magnetic material, a magnet 20 and a magnetic fluid 21, so that a large change in inductance can be obtained in the coil 22. The magnetic permeability of a magnet (permanently magnetized magnetic material) is much higher than that of air, but it is much lower than that of an unmagnetized ferromagnetic material, so the structures shown in Figures 2 and 7 Although it has a simple structure and is advantageous in terms of cost, it is not possible to obtain a large inductance. On the other hand, in the embodiment shown in FIG. 8, a large change in inductance can be obtained.
Note that the interference between the magnetic lines of force 26 and the lines of magnetic force 27 is as follows:
This can be eliminated by increasing the dimensions of the joint portion 29 to a certain extent.

<Effects> As described above, the water level detection device of the present invention converts changes in the water level in the aquarium into changes in air pressure, and moves the movable part made of a magnetic material into and out of the coil in response to the changes in air pressure. Since changes in the inductance of the tank are changed and changes in water level are detected based on changes in inductance, changes in the water level in the aquarium can be continuously detected over a wide range with a small movement range of the movable parts.

Moreover, by interposing the magnetic fluid between the fixed part and the movable part to prevent air leakage, compared to conventional sealing members made of synthetic resin, etc.
Since the resistance between the movable part and the fixed part when it moves is reduced, and the movable part can be moved smoothly, it is possible to detect water level changes with high accuracy and less influence from movement resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration explanatory diagram showing a conventional water level detection device, FIG. 2 is a schematic configuration explanatory diagram showing an embodiment of the water level detection device of the present invention, FIG. 3 is an electric circuit diagram of the same, and FIG. A diagram showing the relationship between the water level change and the inductance change, Figure 5 is the same as the above comparator.
Output waveform diagram of IC1, Figure 6 is a diagram showing the resonance point of the voltage at point F as above, Figure 7 is a diagram showing the flow of magnetic lines of force as above, Figure 8 is another embodiment of the water level detection device of the present invention. FIG. 2 is a schematic configuration explanatory diagram of main parts. 1: Water tank, 20: Magnet, 22: Coil.

Claims (1)

[Claims] 1. A water level detection device that detects water level by converting changes in water level in an aquarium into changes in air pressure, including a fixed cylindrical coil having a coil that does not respond to changes in air pressure accompanying changes in water level in the aquarium. a movable part made of a magnetic material that responds to changes in air pressure due to changes in the water level in the water tank and moves in and out of the coil in response to the change in inductance of the coil; a movable part and the fixed part; It is characterized by comprising a magnetic fluid interposed between the movable part and the fixed part to prevent air from leaking between the movable part and the fixed part, and configured to detect a change in water level based on a change in the inductance of the coil. Water level detection device.