JP2011019556A - Washing liquid sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the soil of washing liquid regardless of an atmospheric temperature. <P>SOLUTION: The washing liquid sensor includes temperature detection means 50 for measuring a temperature near an insulating transformer 46 and control means 11 for controlling the operation of a washing machine. When an electrode A12 and an electrode B13 on the secondary side of the insulating transformer 46 are immersed in the washing liquid while the primary side is resonated in parallel by high frequency generation means, the change of a parallel resonance impedance by parallel resonance impedance change means 42 connected to parallel resonance impedance measurement means 41 is detected, and a resistance value in the washing liquid is determined. Further, the control means performs correction to the change portion of the parallel resonance impedance by the temperature detected in the temperature detection means 50 and determines the resistance value in the washing liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a washing liquid sensor for detecting dirt of washing liquid in a washing machine.

  Conventionally, it has been considered that this type of washing liquid sensor detects dirt by the resistance value of the washing liquid, and the structure thereof includes a pair of detection electrodes immersed in the washing liquid and two high-frequency insulation transformers. Connected to the secondary side, connected to the primary side of the high frequency isolation transformer with a high frequency generating circuit for applying a high frequency voltage of 1 to 30 kHz and a sensor reading circuit, and the impedance change read by the sensor reading circuit was taken into the microcomputer to The state is detected (see, for example, Patent Document 1).

JP-A-4-187183

  However, in the conventional configuration, when the ambient temperature of the washing liquid sensor control means changes from 0 ° C. to 40 ° C., the output voltage of the washing liquid sensor changes, and the stain of the washing liquid cannot be accurately detected. was there.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to accurately detect the stain of the washing liquid regardless of the ambient temperature.

  In order to solve the above-described conventional problems, a washing liquid sensor according to the present invention has a pair of detection electrodes immersed in the washing liquid connected to the secondary side of the insulation transformer, and a coil on the primary side of the insulation transformer. And a high-frequency generating means for parallel resonance at a high frequency exceeding 30 kHz with a capacitor connected in parallel with the coil on the primary side of the insulation transformer, and a high-frequency generating means connected to the output of the high-frequency generating means. Parallel resonance impedance measuring means for measuring impedance; parallel resonance impedance changing means connected to the parallel resonance impedance measuring means for detecting a change in parallel resonance impedance; and temperature detecting means for measuring the temperature in the vicinity of the insulation transformer. And a control means for controlling the operation of the washing machine, and the high frequency generating means causes the primary side to resonate in parallel. When the washing liquid is immersed in the secondary electrode of the insulating transformer, the parallel resonance impedance changing means connected to the parallel resonance impedance measuring means detects that the parallel resonance impedance changes, and the washing In addition to determining the resistance value in the liquid, the control means determines the resistance value in the washing liquid by correcting the change in parallel resonance impedance based on the temperature detected by the temperature detection means. is there.

  As a result, it is possible to accurately detect the contamination of the washing liquid of the washing machine regardless of the ambient temperature.

  The washing liquid sensor of the present invention can accurately detect the stain of the washing liquid of the washing machine regardless of the ambient temperature.

1 is a schematic configuration diagram of a washing machine according to Embodiment 1 of the present invention. Configuration diagram of washing liquid sensor of the washing machine Block diagram of the control means of the washing machine Circuit diagram of washing liquid sensor control means of the washing machine Relationship diagram between resistance R1 of washing liquid sensor control means and peak potential of capacitor C2 of the washing machine Relationship between resistance value of washing liquid and dirt in the washing machine Relationship diagram between primary side impedance and secondary side impedance of insulation transformer of the washing machine Waveform diagram of diode 38 of the washing liquid sensor control means of the washing machine Relationship between conductivity and dirt of washing liquid of the washing machine Relationship diagram between output voltage and conductivity of washing liquid sensor control means of the washing machine Relationship diagram between output voltage and temperature of washing liquid sensor control means of the washing machine Relationship diagram of output voltage and conductivity depending on presence / absence of electrode contamination of washing liquid sensor control means of the washing machine

  According to a first aspect of the present invention, a pair of detection electrodes immersed in the washing liquid is connected to the secondary side of the insulation transformer, a capacitor is connected in parallel with the primary side coil of the insulation transformer, A high-frequency generating means for resonating in parallel at a high frequency exceeding 30 kHz with a capacitor connected in parallel with the coil on the primary side; a parallel resonant impedance measuring means connected to the output of the high-frequency generating means for measuring impedance at the time of parallel resonance; Parallel resonance impedance changing means connected to the parallel resonance impedance measuring means for detecting a change in parallel resonance impedance, temperature detecting means for measuring the temperature in the vicinity of the insulating transformer, and control means for controlling the operation of the washing machine. And when the primary side is resonating in parallel by the high-frequency generating means, When the washing liquid is immersed in the parallel resonance impedance, the parallel resonance impedance changing means connected to the parallel resonance impedance measuring means detects that the parallel resonance impedance changes, and determines the resistance value in the washing liquid, and the control means Since the resistance value in the washing liquid is determined by correcting the change in the parallel resonance impedance based on the temperature detected by the temperature detecting means, the washing is performed regardless of the ambient temperature (0 to 40 ° C.). Liquid contamination can be accurately detected by the resistance value (conductivity).

  In the second invention, in particular, the control means of the first invention determines the resistance value in the washing liquid by correcting the parallel resonance impedance by the same temperature characteristic as that of the insulation transformer. As a result, the resistance value of the washing liquid (conductivity) is applied regardless of the ambient temperature (0 to 40 ° C.) by applying the same temperature characteristic correction as that of the insulating transformer that is most susceptible to temperature among the components of the washing liquid sensor. ) Can be detected with high accuracy.

  In the third aspect of the invention, in particular, the control means of the first aspect of the invention predicts the degree of contamination of the electrode from the output voltage of the washing liquid sensor when tap water not containing detergent comes in contact with the electrode, and exceeds the reference voltage. In this case, it is determined that the electrode is soiled abnormally. Can be done.

  In a fourth aspect of the invention, in particular, in any one of the first to third aspects, a circulation path for circulating the washing liquid to the drum is provided, and a washing liquid sensor for detecting the state of the washing liquid is disposed in the circulation path. By installing and circulating tap water that does not contain detergent in the circulation path to remove dirt on the electrode, dirt adhering to the surface of the electrode can be removed by circulating tap water, with high accuracy. The conductivity of the washing liquid can be measured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a washing machine according to a first embodiment of the present invention, FIG. 2 is a configuration diagram of a washing liquid sensor of the washing machine, and FIG. 3 is a block configuration diagram of control means of the washing machine. FIG. 4 is a circuit diagram of the washing liquid sensor control means of the washing machine.

  1 to 4, an outer tub 2 is disposed inside the outer box 1 of the entire washing machine, and a drum 3 as a washing tub is further inclined inside the outer tub 2 from the horizontal direction to the front upward. It is arranged in a rotatable state. The drum 3 is rotated by the rotation of the motor 4 connected to the back side. The drum 3 is provided with a plurality of water passage holes (not shown) on the outer peripheral surface, and functions as a washing tub, a dewatering tub, and a drying tub.

  A water intake 5 is provided in the lowest part of the outer tub 2 and is connected to a drain pipe 7 via a drain valve 6. Between the intake port 5 and the drain valve 6, a circulation path 9 connected to the discharge port 8 for discharging the washing liquid taken in from the intake port 5 to the drum 3 is connected, and the washing liquid and the rinsing liquid in the outer tub 2 are communicated. Can be circulated. The circulation path 9 is provided with a washing liquid sensor 10 for detecting the state of the washing liquid.

  As shown in FIG. 2, the washing liquid sensor 10 is installed such that the electrode A <b> 12 and the electrode B <b> 13 face each other across the circulation path 9, and the washing liquid sensor 10 is connected to the control means 11.

  As shown in FIG. 3, the control means 11 is connected to an AC power supply 20 and supplies power to the central control means 21. The central control means 21 is an operation display means 22 that receives an operation input of the washing machine, a display means 23 that indicates the state of the washing machine, a motor control means 24 that controls the motor 4, and a drain valve control that controls the drain valve 6. The means 25 and the washing liquid sensor control means 26 for controlling the washing liquid sensor 10 are connected.

  A detailed configuration of the washing liquid sensor control means 26 is shown in FIG. In FIG. 4, the washing liquid sensor 10 immersed in the washing liquid has an electrode A12 and an electrode B13, and the insulating transformer 46 is configured by winding a primary side coil 34 and a secondary side coil 33 around a circular ferrite core. Yes. The electrode A12 is connected to one end of the secondary coil 33 of the insulating transformer 46, and the electrode B13 that makes a pair with the electrode A12 is connected to the other end of the secondary coil 33 of the insulating transformer 46.

  One end of the primary side coil 34 of the insulating transformer 46 is connected to one end of a capacitor (C1) 35 connected in parallel with the primary side coil 34 and the input of the inverter 37 which is an amplifier circuit. Are connected at one end of a capacitor (C2) 36 connected in parallel with the primary side coil 34, the other end of the resistor 47 connected at one end to the output of the inverter 37, and the input of the parallel resonance impedance measuring means 41. It is connected to the anode of a certain diode 38.

  The other ends of the capacitor (C1) 35 and the capacitor (C2) 36 are connected to the ground, and the cathode of the diode 38 which is the output of the parallel resonance impedance measuring means 41 is connected to one end of the capacitor (C3) 39 and the resistor (R2) 40. One end is connected to the input of the parallel resonance impedance changing means 42, the other end of the capacitor (C3) 39 and the resistor (R2) 40 is connected to the ground, and the output of the parallel resonance impedance changing means 42 is connected to the central control means 21. The washing liquid sensor control means 26 is configured.

  In the above configuration, the oscillation operation will be described. When the potential of the capacitor (C1) 35 becomes higher than the reference potential of the inverter 37, the output of the inverter 37 becomes low, that is, the ground. Then, since the electric charge of the capacitor (C2) 36 flows to the ground via the resistor (R1) 47 attached outside the output of the inverter 37, the potential of the capacitor (C2) 36 changes.

  On the other hand, oscillation is maintained by exchanging energy of the inductance L determined by the primary coil 34 between the capacitor (C1) 35 and the capacitor (C2) 36. That is, the output of the inverter 37 continues the oscillation frequency determined by the inductance L, the capacitor (C1) 35, and the capacitor (C2) 36 by preventing the charge of the capacitor (C2) 36 from being absorbed as much as possible.

  If the sink current of the inverter 37 is large and the resistor (R1) 47 is too small, the capacitor (C2) can be obtained at a time earlier than the period of the oscillation frequency determined by the inductance L, the capacitor (C1) 35, and the capacitor (C2) 36. ) 36 is absorbed by the output of the inverter 37, and the energy of the inductance L cannot be exchanged between the capacitor (C1) 35 and the capacitor (C2) 36, and the inductance L, the capacitor (C1) 35, and the capacitor ( C2) The oscillation frequency determined by 36 is not continued.

  Therefore, by regulating the sink current of the output of the inverter 37 by the resistor (R1) 47, the energy of the inductance L can be exchanged between the capacitor (C1) 35 and the capacitor (C2) 36, and the capacitor (C1) 35 The oscillation frequency determined by the capacitor (C2) 36 can be continued.

  As for the discharge current of the inverter 37, the oscillation frequency determined by the inductance L, the capacitor (C1) 35, and the capacitor (C2) 36 is continued by restricting the discharge current by the resistor (R1) 47, similarly to the sink current. be able to.

  Further, by changing the value of the output resistor (R1) 47 of the inverter 37, the charge of the capacitor (C2) 36 can be adjusted, so that the potential of the capacitor (C2) 36, that is, the output amplitude of Colpitts oscillation can be changed. .

  FIG. 5 shows the relationship between the resistance (R1) 47 of the washing liquid sensor control means 26 and the peak potential of the capacitor C2) 36. The horizontal axis represents the value of the resistance (R1) 47, and the vertical axis represents the capacitor (C2). ) Shows a peak potential of 36. Even if the peak potential of the capacitor (C2) 36, that is, the output amplitude of Colpitts oscillation, changes due to the inductance L determined by the primary coil 34 and the component constant variation of the capacitor (C1) 35 and the capacitor (C2) 36, the resistance ( By changing the value of (R1) 47, the output amplitude can be adjusted to be constant.

  Next, an operation for detecting the resistance value of the washing liquid in the washing machine of the present embodiment will be described. An instruction for washing and rinsing is given to the central control means 21 from the operation display means 22 of FIG. Then, when water is supplied and the motor 4 is driven by the motor control means 24 and the drum 3 rotates, the washing liquid in the drum 3 and the outer tub 2 enters the circulation path 9 from the water intake 5 and enters the circulation path 9. It circulates to the drum 3 through the provided washing liquid sensor 10.

  Thereby, the water in the circulation path 9 is always in the same state as the washing liquid in the drum 3 and the outer tub 2. The washing liquid gradually becomes cloudy due to the dissolution of dirt from the laundry by the detergent and the stirring by the rotation of the drum 3. On the other hand, the amount of the sweat component of the washing liquid can be captured as a change in the resistance value of the washing liquid.

FIG. 6 shows the relationship between the amount of the sweat component of the washing liquid and the resistance value of the washing liquid. When the resistance value of the washing liquid is measured, it is possible to determine the amount of dirt mainly composed of sweat (main component is sodium chloride) dissolved from the laundry, and the washing liquid sensor 10 and the washing liquid sensor control means 26 use the resistance of the washing liquid. You can see the change in value status.

  A method of checking the change in the resistance value of the washing liquid with the washing liquid sensor 10 and the washing liquid sensor control means 26 will be specifically described with reference to FIG. The detection electrodes A12 and B13 are connected to the secondary coil 33 of the insulation transformer 46. The parallel resonance impedance on the primary side when the resistance value of the secondary coil 33 is infinite when the washing liquid is lost between the electrodes A12 and B13 for detection immersed in the washing liquid and the air contacts is Z1. And

  Assuming that the resistance value when the washing liquid is in contact between the electrode A12 and the electrode B13 is Z2, the AC waveform oscillating by resonating at the frequency fr on the primary side is also the voltage of the same AC frequency fr on the secondary side. Will occur.

  At that time, the parallel resonance impedance on the primary side is Z12, which is smaller than Z1. That is, when the resistance value of the washing liquid of the secondary coil 33 decreases, the parallel resonance impedance Z1 on the primary side also decreases.

  As a result, the sine wave amplitude of the capacitor (C2) 36, which is the output of the sine wave of the Colpitts oscillation circuit, is also reduced, and as shown in FIG. 8, the diode 37, which is the input of the parallel resonance impedance measuring means 41, is connected to the anode 38 of the inverter 37. A sine wave is applied around the reference potential. The capacitor (C3) 39 of the parallel resonance impedance measuring means 41 of FIG. 4 connected to the anode 38 of the diode is set small so as not to affect the resonance capacitors (C1) 35 and (C2) 36, and the capacitor ( C3) If the resistance (R2) 40 connected in parallel to 39 is increased to increase the discharge time constant, the waveform of the diode cathode 38, which is the output of the parallel resonance impedance measuring means 41, is as shown in FIG. The peak voltage of the sine wave is maintained. This voltage becomes the input voltage of the resonance impedance changing means 42.

  The parallel resonant impedance changing means 42 looks at the change in the output voltage of the parallel resonant impedance measuring means 41, thereby measuring the impedance Z1 on the primary side of the insulating transformer 46 shown in FIG. From the relationship of the impedance on the secondary side (resistance value of the washing liquid immersed in the washing liquid) Z2, the resistance value Z2 of the washing liquid contacting between the electrode A12 for detection immersed in the washing liquid and the electrode B13 is obtained. Judgment can be made.

  In the present embodiment, a Colpitts oscillation circuit is used as the high-frequency generating means 43 of the washing liquid sensor control means 26, which is an inductance L of the primary coil 34 of the insulating transformer 46, a capacitor (C 1) 35, and a capacitor (C 2) 36. Since the self-excited oscillation automatically oscillates at the parallel resonance frequency is determined, even if the parallel resonance frequency changes due to the temperature change of the insulation transformer 46 and the capacitor, the change in the parallel resonance parallel resonance impedance is small. . Further, since the oscillation is continued with the maximum value of the parallel resonance impedance because of self-excited oscillation, it is suitable for a washing liquid sensor for accurately checking the resistance value of the washing liquid.

  In addition, according to the present embodiment, the parallel resonance impedance on the primary side when the washing liquid disappears between the detection electrode A12 and the electrode B13 and the air contacts is infinite when the resistance value is infinite. The large resistance value of the washing liquid cannot be detected. Since the resistance value of the washing liquid varies depending on the resistance value depending on the concentration of sodium chloride contained in the washing liquid, the distance between the electrode A12 and the electrode B13, and the electrode shape, the parallel resonance impedance on the primary side increases as Z1 increases. Since the large resistance value of the washing liquid, which is the resistance value Z2 on the next side, can be detected, the detection range is expanded and the accuracy is improved.

  Accordingly, in order to increase the primary side parallel resonance impedance Z1, it is necessary to increase the inductance L of the primary side coil 33 and increase the Q value. The Q value is expressed by Equation 1.

  That is, if the resonance frequency fr and the inductance L are increased and the resistance r connected in series with the inductance L is decreased, the Q value is increased.

  In the conventional technique, the frequency is 1 to 30 kHz, but a sufficiently large Q value cannot be obtained. Therefore, in the present invention, the resonance impedance Zr is increased by increasing the Q value at a resonance frequency exceeding 30 kHz. About 4 kΩ, which is the resistance value of the tap water shown, can be detected.

  In addition, as a method of increasing the Q value, a method of reducing the resistance r connected in series with the inductance L, a method of increasing the diameter of the primary side coil 34, or a single coil based on many thin lead wires. There are methods such as. As a method of increasing the inductance L, there are a method of increasing the number of turns and a method of increasing the permeability of the core of the transformer. If the Q value is increased, the parallel resonance impedance on the primary side can be increased, so that the range of impedance change due to the change in the resistance value (secondary resistance value) of the washing liquid can be expanded.

  Thus, the control means 11 controls the washing liquid sensor control means 26 to measure the resistance value of the washing liquid, for example, every minute, judge the state of the washing liquid, and use it for controlling the washing process and the rinsing process. Can do. For example, if the resistance value is higher than a predetermined value, the control means 11 determines that the resistance value is equivalent to tap water, determines that the rinsing is complete, and can be used for control such as ending the rinsing.

  FIG. 6 shows the relationship between the amount of the sweat component (degree of dirt) and the resistance value of the secondary coil 33. The degree of dirt of the washing liquid is measured by electrical conductivity. There is a correlation between the resistance value and the electrical conductivity, and measuring the resistance value and measuring the electrical conductivity are the same from the viewpoint of measuring the soiling of the washing liquid.

  FIG. 9 shows the relationship between the amount of sweat components (contamination level) and electrical conductivity. The greater the conductivity value, the greater the contamination. As described above, the resistance value of the secondary coil 33 changes the parallel impedance, and the change in the parallel resonance impedance appears as the output voltage of the washing liquid sensor control means 26.

  FIG. 10 shows the relationship between the output voltage of the washing liquid sensor control means 26 and the electrical conductivity when the ambient temperature is 20 ° C., which is the highest when the washing machine is used. In FIG. 10, the output voltage when the electrode A12 and the electrode B13 are completely insulated is Va, the output voltage when tap water (conductivity of about 0.18 ms / cm) is Vw, The relationship between conductivity and output voltage when there is no electrode contamination is shown.

  In FIG. 11, in the state where tap water (conductivity of about 0.18 ms / cm) is in contact between the electrode A12 and the electrode B13, the horizontal axis represents the ambient temperature of the washing liquid sensor control means 26 at 0 ° C., 20 ° C., The relationship of the output voltage of the washing liquid sensor control means 26 is shown on the vertical axis at 40 ° C. and 60 ° C.

This is the minimum output voltage at 0 ° C., the maximum output voltage at 40 ° C., and the output voltage decreases again at 60 ° C. This can be approximated by an approximate expression of an upward convex quadratic curve. Theoretically, the temperature characteristics of ferrite, which is the material of the core of the insulating transformer 46, affects the output voltage. The central control means 21 stores the relationship between the output voltage of the washing liquid sensor control means 26 and the electrical conductivity when the ambient temperature is 20 ° C., takes in the output voltage of the washing liquid sensor control means 26, and compares it with the stored data. Then, the conductivity of the washing liquid is calculated.

  In the output voltage, the influence of temperature and the influence of conductivity are mixed, so correction for temperature is necessary. Therefore, a temperature detection means 50 for measuring the temperature in the vicinity of the insulating transformer 46 of the washing liquid sensor control means 26 of the control means 11 is provided, and the central control means 21 determines the parallel resonance impedance based on the temperature measured by the temperature detection means 50. The voltage of the temperature measured by the approximate expression of the upward convex quadratic curve obtained by the experiment obtained in FIG. As shown in FIG. 10, if the relationship between the output voltage and the conductivity when the ambient temperature of the washing liquid sensor control means 26 is 20 ° C. is stored as data as shown in FIG. If you know, you will know the conductivity.

  In addition, although temperature correction was applied by an approximate expression of an upward convex quadratic curve in FIG. 11, theoretically, the temperature characteristics of ferrite, which is the material of the core of the insulating transformer 46, have been obtained. The same temperature characteristic correction as that of 46 may be applied. By applying the same temperature characteristic correction as the insulation transformer that is most susceptible to temperature among the components of the washing liquid sensor, the resistance value (conductivity) of the washing liquid can be accurately adjusted regardless of the ambient temperature (0 to 40 ° C). Can be detected.

  Next, FIG. 12 shows a state in which the insulating dirt such as sand or plastic adheres to the surface of the electrode as △, a state in which the electrode surface is not dirty as an asterisk, and the horizontal axis as conductivity. The vertical axis represents the output voltage.

  When the electrode is severely contaminated, the central control means 21 sees only the output voltage of the washing liquid sensor control means 26, and therefore cannot identify whether the washing liquid conductivity changes or the electrode dirt changes. Since the influence of electrode contamination and the influence of conductivity are mixed in the output voltage, it is necessary to correct the electrode contamination.

  Therefore, a method for correcting electrode contamination will be described in detail. When the conductivity is zero, the electrode A12 and the electrode B13 are insulated from each other, and the output voltage is Va. When tap water not containing a detergent (conductivity of about 0.18 ms / cm) is brought into contact between the electrode A12 and the electrode B13 in the rinsing step, the output voltage shown in FIG. 13 indicates Vw. Now, the output voltage when there is electrode contamination indicates Vm.

  When the electrode becomes dirty, the resistance value between the electrode A12 and the electrode B13 increases, and the output voltage approaches Va. The change in voltage can predict the degree of electrode contamination. Further, when Vm exceeds the reference voltage Vref set smaller than Va and larger than Vw shown in FIG. 13, it is regarded as an electrode contamination abnormality. The reference voltage is set to be smaller than the output voltage in a state where the electrode A12 and the electrode B13 are insulated, and larger than the output voltage when tap water not containing detergent comes into contact.

  If the electrode is heavily soiled, there is a problem that the laundry is erroneously determined as being soiled and the laundry is terminated, even though the laundry is soiled. Therefore, the degree of contamination of the electrode is determined with tap water used in the rinsing process, and predetermined washing can be performed in another set sequence.

  That is, the central control unit 21 can determine that the electrode contamination is abnormal when Vout exceeds Vre by measuring the output voltage Vout of the washing liquid sensor control unit 26, and can perform normal washing.

  The present invention electrically detects an abnormal soiling of the electrode. In addition to removing dirt on the electrode surface by circulating water containing no detergent in the circulation path 9 by detecting the soiling, The surface of the electrode is mechanically rubbed to remove the dirt. For example, the dirt of the electrode can be mechanically removed to prevent abnormalities due to the dirt of the electrode.

  The washing liquid sensor of the present invention is useful as a washing liquid sensor for detecting the stain of the washing liquid of the washing machine because the washing liquid of the washing machine can be accurately detected regardless of the ambient temperature.

2 Outer tub 3 Drum 4 Motor 9 Circulation path 10 Washing liquid sensor 11 Control means 12 Electrode A
13 Electrode B
26 Washing liquid sensor control means 33 Secondary coil of insulation transformer 34 Primary coil of insulation transformer 41 Parallel resonance impedance measurement means 42 Parallel resonance impedance change means 46 Insulation transformer 50 Temperature detection means

Claims (4)

A pair of detection electrodes immersed in the washing liquid is connected to the secondary side of the insulating transformer, a capacitor is connected in parallel to the primary side coil of the insulating transformer, and parallel to the primary side coil of the insulating transformer. A high frequency generating means for performing parallel resonance at a high frequency exceeding 30 kHz with a capacitor connected to the parallel resonance impedance measuring means connected to the output of the high frequency generating means for measuring impedance at the time of parallel resonance; and the parallel resonant impedance measuring means. The high frequency generating means comprising: parallel resonant impedance changing means connected to detect a change in parallel resonant impedance; temperature detecting means for measuring a temperature in the vicinity of the insulating transformer; and control means for controlling the operation of the washing machine. When the primary side resonates in parallel, the washing liquid is immersed in the secondary side electrode of the insulation transformer. Then, the parallel resonance impedance changing means connected to the parallel resonance impedance measuring means detects that the parallel resonance impedance is changed, and determines a resistance value in the washing liquid, and the control means is configured to detect the temperature. A washing liquid sensor that determines the resistance value in the washing liquid by correcting the change in the parallel resonance impedance based on the temperature detected by the means. 2. The washing liquid sensor according to claim 1, wherein the control means determines the resistance value in the washing liquid by correcting the change in the parallel resonance impedance by the same temperature characteristic as the temperature characteristic of the insulating transformer. The control means predicts the degree of contamination of the electrode from the output voltage of the washing liquid sensor when tap water not containing detergent comes into contact with the electrode, and determines that the electrode contamination is abnormal when the reference voltage is exceeded. The washing liquid sensor according to 1. A circulation path for circulating the washing liquid to the drum is provided, and a washing liquid sensor for detecting the state of the washing liquid is disposed in the circulation path, and tap water not containing detergent is circulated in the circulation path to clean the electrodes. The washing liquid sensor according to any one of claims 1 to 3, wherein the washing liquid sensor is removed.