JPH0768083A - Water level detector for washing machine - Google Patents

Abstract

(57) [Summary] [Purpose] To realize cost reduction, improvement of external noise resistance, simplification of adjustment, and improvement of water pressure detection accuracy. A part of the copper foil pattern 16 of the printed wiring board 14 is used as one electrode 17, and the other electrode 20 arranged so as to face the one electrode 17 is provided on a diaphragm 19 movable by the water pressure of a water tank. , A water level detection device for a washing machine configured to detect the water level in the water tub based on the capacitance value between the electrodes 17 and 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level detecting device installed in a washing machine and capable of continuously detecting a water level change in a water tank.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 14, for example, as shown in FIG. 14, a water level detecting device of this type is provided with an air trap 52 at the bottom of a water tub 51 installed in a washing machine body (not shown). 52 is connected to a water pressure detecting section 54 via a pressure guiding hose 53, and an output end of the water pressure detecting section 54 is electrically connected to a control circuit 56 provided in the washing machine via a lead wire 55. In order to detect the water level change in the water tank 51 based on the detection data of the pressure change in the control circuit 56, the water pressure detection unit 54 electrically converts the change in the air pressure in the air trap 52 due to the water level change in the water tank 51. Is configured.

FIG. 15 shows an example of the water pressure detector 54. As shown in this figure, in the conventional water pressure detector 54,
A rubber diaphragm 59 is sandwiched between a case 57 and a case cover 58, which communicate with the air trap 52 via a pressure guiding hose 53, and the movable member 6 is mounted on the diaphragm 59.
0 and the movable member 60 is attached to the spring 6
1, a magnetic body 62 such as a ferrite core is attached to the movable member 60, a coil 63 is fixed to the inner peripheral surface of the case cover 58, and a lead wire is connected from the coil 63 to the control circuit 56. 55 is pulled out.

In the case of the water pressure detector 54, the amount of change in the shape of the diaphragm 59 is determined by the relationship between the change in pressure given from the air trap 52 and the urging force of the spring 61, and the change in shape of the diaphragm 59 is determined. As the magnetic body 62 moves up and down and moves in and out of the coil 63, the inductance of the coil 63 changes.

FIG. 16 shows an example of the control circuit 56. As shown in this figure, the conventional control circuit 56 includes an oscillation circuit 64 and a microcomputer 65,
The inductance change of the coil 63 in the water pressure detection unit 54 is converted into a frequency by the oscillation circuit 64, and the microcomputer 65 is configured to detect the water level as a frequency change.

Further, as an improvement of the above problems in the conventional configuration, for example, even if noise is placed on the lead wire 55 wired between the coil 63 and the control circuit 56, noise is prevented from entering the oscillation circuit 64. , The oscillation circuit 64
In which the coil is arranged separately from the coil 63 (Japanese Patent Application Laid-Open No. 2-29)
294) or the magnetic body 62 and the coil 6 in the water pressure detector 54 in order to avoid the influence of the expansion and contraction of the spring 61 on the inductance change of the coil 63 as much as possible.
A device in which the arrangement of No. 3 is devised (Japanese Utility Model Publication No. 3-23186) is proposed.

Incidentally, in the conventional method for detecting the change in the water level in the water tank 51 by utilizing the change in the inductance of the coil 63 as described above, even if other than the above examples,
Similar to the above-mentioned conventional example, the water pressure detection unit 54 is configured separately from the control circuit 56, and the electrical connection between the two 54, 56 is established by the lead wire 55. It is also possible to provide the oscillation circuit 64 in the water pressure detection unit 54, but in this case as well, a lead wire for connecting the oscillation circuit 64 and the microcomputer 65 is required.

[0008]

However, as in each of the above-mentioned conventional examples, the water pressure detection section 54 and the control circuit 56 are separately configured, and the two 54, 56 are electrically connected by using the lead wire 55. There are the following problems with the one that employs the connected configuration. First, the water pressure detection unit 54, including the oscillator circuit 64 built-in, is installed separately from the control circuit 56, so that not only must a case be prepared separately, but also the cost of parts of the lead wire itself. In addition, the cost of assembling the wiring is also required, which causes a high cost.

Further, since the water pressure detector 54 and the lead wire 55 have high impedance, they are easily affected by electromagnetic noise from the surroundings. Therefore, a noise component other than the original detection signal may be input to the control circuit 56, which may cause erroneous detection of the water level or malfunction of the microcomputer 65 due to noise, such as reset or latch-up.

Further, in the case where the water pressure detection unit 54 does not include the oscillation circuit 64 forming a part of the control circuit 56, the water level is taken into consideration while taking into consideration the variation in the accuracy of the water pressure detection unit 54 and the variation in the constant number of the oscillation circuit 64. Since it is necessary to improve the detection accuracy, the adjustment value width of the water pressure detection unit 54 is extremely narrowed, or a highly accurate capacitor of, for example, about ± 1% is used in the oscillation circuit 64. For this reason, the total cost of the device is inevitably high in combination with the above-mentioned cost problem.

The present invention has been made in order to solve the above-mentioned conventional problems, and by constructing the water pressure detector integrally with the inside of the control circuit, a significant cost reduction can be achieved. It is an object of the present invention to provide a novel water level detection device for a washing machine, which can improve external noise resistance and simplify initial adjustment, and which can realize excellent water level detection accuracy.

[0012]

In order to achieve the above object, according to the present invention, a load such as a motor of a washing machine or a valve for supplying and draining a washing machine is provided in a switch provided in an operating portion or a required place of the washing machine. A printed wiring board on which a control circuit for controlling based on an input signal from a provided sensor is mounted is used, and one electrode is formed by a part of a conductive pattern formed on the printed wiring board. ing.

Further, a movable body that responds to a change in water pressure due to a change in water level in the water tank is provided, and the other electrode disposed so as to face the one electrode by this movable body has a relative distance from the one electrode. The control circuit is configured to be displaced in a changing direction, and further, the control circuit is configured to detect the water level in the water tank based on a change in the electrostatic capacitance between the two electrodes accompanying a change in the distance between the two electrodes. .

In the above structure, the movable body is composed of a rubber diaphragm which changes its shape in response to a change in water pressure due to a change in water level in the water tank, and the amount of change in the shape of the diaphragm corresponds to the amount of displacement of the other electrode. Can be converted. In this case, a conductive layer can be formed on the surface of the diaphragm facing the one electrode, and this conductive layer can be used as the other electrode. Further, in order to improve the assembling property, the other electrode may be formed in a shape such that a part thereof can be directly electrically connected to the conductive pattern of the printed wiring board.

In the above construction, it is desirable to provide a means for adjusting the distance between both electrodes. In this case, as the adjusting means, the other electrode is separated from the printed wiring board between the other electrode and the printed wiring board. An example is one in which a spring that urges in the direction is interposed, and the position of the end of the spring on the printed wiring board side can be adjusted in the direction that changes the spring pressure of the spring.

Further, by connecting a variable capacitor for adjusting the capacitance in parallel or in series with the capacitance body formed by both electrodes, the capacitance serving as a reference for the water level determination in the control circuit. You can make initial adjustments to the values.

Further, by providing an electrically rewritable nonvolatile memory for storing the water level detection data of the control circuit when the reference pressure corresponding to the water pressure in the water tank is applied to the movable body, the software water level detection is performed. Will be possible.

Furthermore, a CR oscillating circuit for frequency-converting the electrostatic capacitance of the electrostatic capacitance body formed by both electrodes is provided, and the control circuit judges the water level in the water tank based on the output data of the CR oscillating circuit. Or a fixed resistor for charging and discharging the electrostatic capacitance body is interposed between the electrostatic capacitance body formed by both electrodes and the control circuit, and the electrostatic capacitance is provided in the control circuit. By measuring the charging or discharging time of the body, the capacitance value of the capacitance body can be determined.

[0019]

According to the above construction, the movable body operates in response to the change in the water level in the water tank, and the movement of the movable body moves the other electrode, so that the distance between the two electrodes changes, and accordingly, the distance between both electrodes changes. The capacitance between the electrodes also changes. The water level in the water tank can be determined by determining this change in capacitance with the control circuit.

Further, since the capacitance conversion method is used in which a part of the conductive pattern inside the control circuit is used, the structure of the water pressure detecting portion can be integrated with the control circuit, which results in low cost and durability. Noise can be improved, and since there is no combination of parts, adjustment can be done easily and at low cost.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a water level detecting device for a washing machine according to the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a control device in a general washing machine. In this figure, 1 is a control circuit, 2 is various switches provided in an operating section, 3 is a water pressure detecting section which will be described later, 4 is a motor which is a drive source for a pulsator and a dehydration and washing tub, 5 is a drain valve, and 6
Is a water supply valve.

The control circuit 1 includes a microcomputer 7 as a central control unit, an interface 8 common to various switches 2, an oscillation circuit 9 described later, and an operation display circuit 1.
0, a drive circuit 11, 12 and 13 that drives a motor 4 as a load, a drain valve 5 and a water supply valve 6 based on a command from a microcomputer 7, and is installed in various switches 2 and required parts of a washing machine. The load is controlled based on the input signals from the various sensors provided.

FIG. 2 shows the water pressure detector 3 in the first embodiment of the present invention. In this figure, 14 is a printed wiring board on which the components of the control circuit 1 shown in FIG. 1 are mounted. In FIG. 2, the printed wiring board 1 is used as an example.
4 shows a state in which the resistor component 15 is mounted, but in addition, the microcomputer 7, the oscillating circuit 9, the driving circuits 11 to 13, and the electronic components constituting the circuit such as the transistor, the capacitor, and the triac are also mounted. Needless to say.

In this embodiment, this printed wiring board 14 is used.
Uses a copper foil pattern 16 as a conductive pattern for connecting the components of the control circuit 1, and the copper foil pattern 16 is formed on the lower surface of the printed wiring board 14 and one of the copper foil patterns 16 is formed. The part is configured to function as one electrode 17. The one electrode 17
Even if a surface treatment such as a solder resist treatment is applied to the above, the present invention is not specified at all.

A case 18 is hermetically attached to the lower surface portion of the printed wiring board 14 including the formation area of the one electrode 17. The inner space of the case 18 has a two-tier structure in which the upper stage is wide and the lower stage is narrow, and a rubber diaphragm 19 as a movable body is fixed to the step portion at its peripheral end portion, and a central portion. Is attached in a state of being vertically deformable, and the other electrode 2 made of, for example, a copper foil is provided on the upper surface of the diaphragm 19 at a portion facing the one electrode 17.
0 is formed. The other electrode 20 is electrically connected via a flexible wire 21 to a predetermined connection pattern 16a formed on the printed wiring board 14.

Further, a pressure-conducting hose 22 is connected to the lower side of the case 18 partitioned by the diaphragm 19, and the printed wiring board 14 is provided with air at the upper part of the case between the board 14 and the diaphragm 19. An air escape hole 23 is formed to open the valve to the atmospheric pressure. In addition,
The air escape hole 22 does not necessarily have to be provided in the printed wiring board 14, but may be formed in the side surface portion of the case 18 above the diaphragm 19, for example.

FIG. 3 shows the arrangement of the apparatus A of this embodiment in the washing machine. As shown in this figure, an air trap C is provided in the lower part of a water tub B installed in a washing machine main body (not shown).
The air trap C via a pressure-conducting hose 22 connected to
Is connected to. In addition, in FIG. 3, L has shown the water level in the water tank B.

In such a configuration, the air pressure in the air trap C changes in accordance with the water level L in the water tank B, that is, the water pressure, and the diaphragm 19 moves in response to the pressure change given from the air trap C. , Its shape changes so that its central portion moves in the vertical direction. At this time, the air in the space inside the case 18 above the diaphragm 19 is released to the atmospheric pressure through the air escape hole 23, and thus the differential pressure between the water pressure side and the atmospheric pressure side can be detected.

In this case, the other electrode 20 fixed to the diaphragm 19 moves upward as shown by the arrow a in FIG. When the water level L in the water tank B becomes lower, the other electrode 20 moves downward and the facing distance to the one electrode 17 becomes wider. The capacitance becomes smaller. In this way, the change in the water level in the water tank B is converted into the change in capacitance.

By the way, in the above structure, the other electrode 20 is formed of copper foil or the like, and the diaphragm 1
Since it is a separate member from 9, the step of fixing it to the diaphragm 19 is required at the time of manufacture. Therefore, as shown in FIG. 4, if the other electrode 20 is replaced with a copper foil and is formed of a metal film deposited on the surface of the diaphragm 19 facing the one electrode 17, the electrode attaching step can be omitted.

In the above structure, the other electrode 2
0 and the connection pattern 16a of the printed wiring board 14 are connected by the flexible wire 21.
As shown in, a part of the case 18, that is, the other electrode 2
If the side wall portion of the case 18 that abuts the metal film forming 0 and the connection pattern 16a of the printed wiring board 14 is formed by the conductor 18a, the connection member such as the flexible wire 21 and the attaching step thereof are unnecessary. Therefore, both the assembly cost and the component cost can be reduced.

Further, as shown in FIG. 5, the other electrode 2
0 is formed by bending a thin metal plate to form a leaf shape with one end bent, while a through hole 24 is formed in a predetermined portion of the printed wiring board 14, and a connection pattern 16a is formed in the through hole 24. By inserting the bent end portion 20a of the other electrode 20 attached to 19 into the through hole 24, the other electrode 20 is directly
It becomes possible to make solder connection to the connection pattern 16a of the printed wiring board 14.

In this case, the shape of the diaphragm 19 is devised so that the other electrode 20 attached to the diaphragm 19 can move up and down only on the other end side as shown by the arrow b. . Also, as shown in FIG.
By providing the printed wiring board 14 with a double-sided wiring structure in which the connecting patterns 16a are provided on both sides, soldering of the other electrode 20 is facilitated and the assembling property can be further improved.

Although the basic structure of the water pressure detecting unit 3 has been described above, in any of the water pressure detecting units 3, the other electrode 20 is moved up and down by using a mechanical structure such as the diaphragm 19. Therefore, a sensitivity adjustment process is required for commercialization. However, since it is not necessary to consider the combination of the water pressure detection unit 54 and the control circuit 56 as in the conventional example, the sensitivity adjustment can be performed extremely easily.

FIG. 6 shows a construction in which a sensitivity adjusting structure is incorporated in the water pressure detecting section 3 shown in FIG. In the sensitivity adjusting mechanism shown in FIG. 6, a screw hole 25 is provided in a portion of the printed wiring board 14 that faces the center of the upper surface of the diaphragm.
5, a spring pressure adjusting screw 26 as an adjusting means is screwed, while a spring receiving member 27 is provided on the diaphragm 19, and a spring 28 is interposed between the spring receiving member 25 and the spring pressure adjusting screw 26. The spring 28 is configured to press the diaphragm 19 downward with an appropriate biasing force.

In the case of this sensitivity adjusting mechanism, the air trap C
The amount of change in the shape of the diaphragm 19 is determined by the force relationship between the pressure change given from the above and the biasing force of the spring 28. Therefore, by appropriately adjusting the protruding amount of the spring pressure adjusting screw 26 from the screw hole 25 and displacing the upper end position of the spring 28, the amount of pressurization of the spring 28 with respect to the diaphragm 19 can be adjusted to an appropriate value. .

FIG. 7 shows both electrodes 17, 2 in response to changes in water pressure.
The capacitance characteristic between 0 is shown. Now, assuming that the water pressure detection unit 3 equipped with the above-mentioned sensitivity adjustment mechanism has the characteristic shown by the solid line p in the unadjusted state in FIG. 7, for example, if the upper end position of the spring 28 is displaced downward, the same water pressure is applied. Even if there is, the amount of change in the shape of the diaphragm 19 becomes small, and the characteristic shifts to the characteristic indicated by the broken line q.

Both electrodes 1 in the water pressure detection unit 3 having the above-mentioned structure
The capacitance value obtained between 7 and 20 can be electrically adjusted. FIG. 8 shows a circuit for performing the adjustment. In the structure shown in this figure, a first variable capacitor 30 is connected in series with a capacitance body 29 formed by both electrodes 17, 20.
And the second variable capacitor 31 is connected in parallel.

If it is desired to lower the above-mentioned sensitivity in such a configuration, a capacitor having a larger electrostatic capacity than the electrostatic capacity body 29 is added at the position of the first variable capacitor 30, and the solid line in FIG. It is possible to shift from the characteristic p to the characteristic s shown by the one-dot chain line, and the adjusting function substantially similar to that of the mechanical sensitivity adjusting mechanism shown in FIG. 6 is exhibited. The sensitivity is adjusted to be lower as the capacitance of the first variable capacitor 30 is reduced.

Further, by adjusting the electrostatic capacitance value of the second variable capacitor 31, it becomes possible to move the characteristics in FIG. 7 in parallel, which is not possible with the sensitivity adjusting mechanism shown in FIG. For example, if the capacitance value of the second variable capacitor 31 is adjusted to be large, in the characteristic diagram of FIG. 7, the solid line characteristic p can be moved in parallel to the dotted line characteristic r. The combination can further improve the sensitivity adjusting function as compared with the mechanical type.

In the present invention, the automatic adjustment using the microcomputer software, which is possible only when the control circuit 1 and the water pressure detector 3 are integrated, can be realized. The frequency conversion circuit 32 shown in FIG. 8 will be described later, but here, the microcomputer 7 to which the pulse frequency from the frequency conversion circuit 32 is input will be described as an example. An EEPROM 33 is an electrically rewritable non-volatile memory, and is a semiconductor memory capable of writing, reading, and erasing the internal memory by communicating with the microcomputer 7.

Microcomputer 7 and EEPR
The capacitance adjustment process using the OM 33 will be described with reference to the flowchart of FIG. 9. A characteristic data writing program which is not used in a normal washing operation is created in advance in the ROM inside the microcomputer, and step # 10 is performed.
Then, the input mode is changed to the characteristic data writing mode under the input condition that a general user cannot operate. The input condition is that a specific terminal of the microcomputer 7 is forcibly set to high or low from the outside, or the operation display circuit 1 shown in FIG.
This means multiple pressing of the 0 switch.

After shifting to the write mode, in step # 20,
The microcomputer 7 is set to the writing state of 50 mmH ₂ O hydraulic pressure data by the determined operation switch of the operation display circuit 10. It should be noted that, including this operation, in performing the following status setting or data writing operation to the memory, the present invention is not limited even if the above-described operation switch or the setting of the specific terminal of the microcomputer is used. Absent.

Next, in step # 30, a pressure of 50 mmH ₂ O is applied to the water pressure detection unit 3 from an external pressure generator.
In step # 40, the frequency data D50 input from the frequency conversion circuit 32 is changed to E by some operation described above.
Write to EPROM 33. After that, in steps # 50 to # 70, the above-mentioned steps # 20 to #
The frequency data D400 of 400 mmH ₂ O water pressure is written in the EEPROM 33 using the same method as in 40.

The data written in the EEPROM 33 is a, b in the water pressure-frequency characteristic shown in FIG.
Corresponding to the points, the straight line determined by these two points allows the frequencies at other water pressures to be calculated by calculation inside the microcomputer. Here, when the characteristic of the water pressure detection unit 3 is not linear as indicated by the broken line s in FIG. 10, two steps of step # 20 to step # 40 and step # 50 to step # 70 in FIG. 9 are performed. The operation of may be set finely. In the example of the broken line s in FIG. 10, 200 mmH ₂ O
(C point) and 300mmH ₂ O (d point) are added to set at 4 points.

Needless to say, the frequency data corresponding to the water pressure during operation is read out by reading out the memory contents of the memory address determined for each water pressure.

Next, referring to FIG. 8, the water pressure detector 3
A method for frequency conversion of the electrostatic capacitance of 1 by the CR oscillation circuit will be described. The frequency conversion circuit 32 is a comparator 3
4 and peripheral resistors R1 to R5, R1 is a pull-up resistor of the comparator 34, and R2 is a capacitance body 2.
9 and charging / discharging resistors of the first and second variable capacitors 30 and 31, R3 and R4 are voltage dividing voltages that generate a voltage that determines a voltage comparison value of the electrostatic capacitance body 29 and the first and second variable capacitors 30 and 31. A resistor, R5, is a hysteresis resistor for changing the voltage setting of the non-inverting terminal of the comparator 34.

FIG. 11 is a time chart showing the operation of the frequency conversion circuit 32. The voltage V (-) shown by the solid line in FIG.
Is the input voltage to the inverting terminal of the comparator 34,
Capacitance body 29 and first and second variable capacitors 30, 3
1 voltage. The voltage V (+) shown by the dotted line is the input voltage to the non-inverting terminal. The signal shown in FIG. 7B is a frequency signal that is input to the microcomputer 7 at the output of the comparator 34.

At time t1, the comparator 34 is turned off.
Then, the charging / discharging current flows through the capacitance body 29 and the first and second variable capacitors 30 and 31 via the charging / discharging resistors R1 and R2, and the voltage V (−) rises. However, at time t2 when the voltage V (+) combined by the voltage dividing resistors R3 and R4 and the hysteresis resistor R5 is exceeded, the comparator 34 turns on O.
N, and it becomes low level. At the same time, the resistance for hysteresis R
Since the right side of 5 becomes the low level, the voltage V (+) becomes similar to that connected to the pull-down side, and the voltage V (+) decreases.

The capacitance 29 and the first and second variable capacitors 30 and 31 are discharged toward the output of the comparator 34 via the charging / discharging resistor R2, and the voltage gradually decreases,
At time t3 has reached the reduced voltage V (+), the process proceeds to the same charging period and again t ₁ and later. Here, when the capacitance of the capacitance body 29 and the first and second variable capacitors 30 and 31 are large (high water pressure), the charging / discharging time constant becomes large and the slope of V (-) becomes small, so t1 The period represented by ~ t3 becomes longer and the frequency decreases (see FIG. 10).

As described above, the frequency pulse corresponding to the water pressure is input to the microcomputer 7. The CR oscillation circuit is only one embodiment of the present invention,
It may be a CR oscillation circuit of another system.

Next, a method of converting electrostatic capacitance into frequency without using an oscillation circuit will be described with reference to FIGS. 12 and 13. The electrostatic capacitance body 29 is charged / discharged by the charging / discharging resistor R6. Inside the output port 35 of the microcomputer 7, Pch and Nch FETs (field effect transistors) are provided.
It has a three-state configuration in which 36 and 37 are connected.
Further, the A / D port provided in the microcomputer 7 for converting an analog input voltage into a digital voltage detects the voltage of the electrostatic capacitance body 29.

Now, at time t1 in FIG. 13, Pch FET 36
When is turned on, a charging current flows from Vcc to the capacitance body 29 through the charging / discharging resistor R6, and the voltage Vc of the capacitance body 29 rises. When the A / D port of the microcomputer 7 detects that the preset voltage value V (H) has been reached, the Pch FET 36 is turned off and the Nch FET 37 is turned on (t2). After that, the electrostatic capacitance body 29 is discharged to the GND side through the charging / discharging resistor R6 and the Nch FET 37, and the voltage Vc decreases and reaches a preset voltage value V (L) (t3). Return to the state of t1 again.

The cycle of t1 to t3 becomes longer if the electrostatic capacity is large (high water pressure) as in the characteristic of FIG. 11, so that the water pressure (water level) can be detected by this cycle. Needless to say, this t1 to t3 time can be measured by a timer inside the microcomputer, but conversely, ON / OF of the Pch FET 36 or the Nch FET 37 for a fixed time
If the number of times of F is counted, it can be detected as a frequency.

[0055]

As described above, according to the present invention, one electrode is formed by a part of the conductive pattern on the printed wiring board on which the control circuit is mounted, and the other electrode facing the one electrode. Is displaced in the direction of changing the relative distance to one of the electrodes in response to the change in water pressure due to the change in water level in the water tank, and the water level in the water tank is detected based on the changing capacitance between both electrodes. Therefore, the configuration of the water pressure detection unit can be integrated with the control circuit. Since the lead wire for connecting the conventional water pressure detection unit and the control circuit is not required, it is possible to realize a large cost reduction, improvement of external noise resistance, simplification of adjustment and improvement of water pressure detection accuracy.

According to the third aspect, the movable body for moving the other electrode is constituted by a rubber diaphragm which changes its shape in response to a change in water pressure due to a change in water level in the water tank, and the amount of change in shape of the diaphragm. In which the other electrode is converted into the displacement amount of the other electrode, the other electrode is constituted by the conductive layer formed on the surface of the diaphragm facing the one electrode, and therefore the electrode attaching step is omitted. You can

According to the fourth aspect, since the other electrode is formed in a shape such that a part thereof can be directly electrically connected to the conductive pattern of the printed wiring board, the other electrode and the printed wiring board are formed. The connecting member for connecting to the conductive pattern and its mounting process are unnecessary, and the assembly cost,
Both parts cost can be reduced.

According to the present invention, a spring for biasing the other electrode in the direction away from the printed wiring board is interposed between the other electrode and the printed wiring board, and
Since the end portion of the spring on the printed wiring board side is positionally adjustable in the direction in which the spring pressure of the spring is changed, the adjusting means for adjusting the distance between the electrodes is provided. By displacing
The amount of pressure applied to the other electrode of the spring can be adjusted to an appropriate value.

Further, in the case of claim 6 to claim 9,
Variable capacitor for capacitance adjustment, electrically rewritable nonvolatile memory for storing water level detection data, CR oscillation circuit for frequency converting the capacitance of the capacitance body formed between both electrodes, Can easily and accurately adjust the sensitivity electrically by using the charging / discharging time of the capacitance body.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a control device in a general washing machine.

FIG. 2 is a schematic cross-sectional view showing a water pressure detector in the embodiment of the invention.

FIG. 3 is a cross-sectional view schematically showing the arrangement configuration in the washing machine.

FIG. 4 is a schematic cross-sectional view showing a modified example of the water pressure detection unit.

FIG. 5 is a schematic cross-sectional view showing another modification of the water pressure detector.

FIG. 6 is a schematic cross-sectional view showing a water pressure detection unit having a sensitivity adjusting structure.

FIG. 7 is a characteristic diagram showing the content of adjustment of the water pressure detection unit.

FIG. 8 is a diagram showing a sensitivity adjustment circuit.

FIG. 9 is a flowchart showing an example of the adjustment.

FIG. 10 is a characteristic diagram showing an adjustment example thereof.

FIG. 11 is a time chart showing the operation of the frequency conversion circuit.

FIG. 12 is a block diagram showing a water level detection circuit.

FIG. 13 is a time chart showing charging / discharging time of a capacitance body.

FIG. 14 is a schematic cross-sectional view showing a water pressure detection unit in a conventional water level detection device.

FIG. 15 is a cross-sectional view schematically showing an example of the arrangement configuration in the washing machine.

FIG. 16 is a block diagram showing the control circuit thereof.

[Explanation of symbols]

 1 Control Circuit 7 Microcomputer 14 Printed Wiring Board 16 Copper Foil Pattern 17 One Electrode 19 Diaphragm 20 Other Electrode 20a Bend End of Other Electrode 26 Spring Pressure Adjusting Screw 28 Spring 29 Capacitance Body 30 First Variable Capacitor 31 Second variable capacitor 32 Frequency conversion circuit 33 EEPROM B Water tank C Air trap R6 Fixed resistor

Claims (9)

[Claims] 1. A printed wiring board on which a control circuit for controlling a load based on an input signal is mounted, wherein one electrode is constituted by a part of a conductive pattern formed on the printed wiring board, The other electrode facing the electrode of No. 1 and the movable body displacing the other electrode in the direction of changing the relative distance to the one electrode in response to the change in water pressure accompanying the change in water level in the water tank. Further, the control circuit is configured to detect the water level in the aquarium based on the change in the capacitance between the electrodes in accordance with the change in the distance between the electrodes. apparatus. 2. The movable body is composed of a rubber diaphragm that changes its shape in response to a change in water pressure due to a change in water level in the water tank, and the amount of change in shape of the diaphragm is converted into the amount of displacement of the other electrode. The water level detecting device for a washing machine according to claim 1, wherein 3. The water level detection device for a washing machine according to claim 2, wherein the other electrode is formed of a conductive layer formed on a surface of the diaphragm facing the one electrode. 4. The water level detecting device for a washing machine according to claim 1, wherein a part of the other electrode is formed in a shape capable of being directly electrically connected to the conductive pattern of the printed wiring board. 5. A spring for urging the other electrode in a direction away from the printed wiring board is interposed between the other electrode and the printed wiring board, and an end portion of the spring on the printed wiring board side is provided. 5. The water level detecting device for a washing machine according to claim 1, further comprising adjusting means for adjusting a distance between both electrodes, the adjusting means being configured to adjust a position in a direction in which a spring pressure of the spring is changed. 6. The water level of the washing machine according to claim 1, wherein a variable capacitor for adjusting capacitance is connected in parallel or in series with the capacitance body formed by both electrodes. Detection device. 7. An electrically rewritable nonvolatile memory for storing water level detection data of a control circuit when a reference pressure corresponding to water pressure in a water tank is applied to a movable body. Water level detection device for any of the washing machines. 8. A CR oscillation circuit for frequency-converting the capacitance of a capacitance body formed by both electrodes is provided, and the control circuit determines the water level of the water tank based on the output data of the CR oscillation circuit. The water level detection device for a washing machine according to claim 1, which is configured. 9. A fixed resistor for charging / discharging the electrostatic capacitance body is interposed between the electrostatic capacitance body formed by both electrodes and the control circuit, and the control circuit is provided with a fixed resistor. The water level detection device for a washing machine according to any one of claims 1 to 7, which is configured to determine a capacitance value of the capacitance body by measuring a charge or discharge time.