JP4103251B2 - Washing machine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a washing machine in which a washing motor is driven by an inverter circuit.
[0002]
[Prior art]
2. Description of the Related Art In recent years, home washing machines have been proposed that improve the cleaning performance or dewatering performance by changing the motor frequency by an inverter device to significantly change the rotational speed of the motor.
[0003]
Conventionally, this type of washing machine is configured as shown in JP-A-9-10469. That is, the inverter circuit that drives the motor, the inverter control circuit, and the control circuit that detects the signal from the water level sensor, controls the water supply valve or the drain valve, and controls the washing operation.
[0004]
[Problems to be solved by the invention]
However, in such a conventional washing machine, the circuit board for the inverter circuit for driving the motor and the circuit board for the control circuit for controlling the washing operation are separated. Therefore, the microcomputer for controlling the inverter and the microcomputer for controlling laundry If two types of microcomputers are required, or if one microcomputer is used, wiring becomes complicated, reliability decreases, switching noise of the inverter circuit enters the laundry control circuit, and malfunctions due to noise, etc. There was a problem.
[0005]
In particular, in the case of a water level detection means that detects the water level from a change in the oscillation frequency of the resonance circuit, the switching frequency of the inverter circuit and the oscillation frequency of the water level detection means are very close, and the water level detection means malfunctions due to switching noise of the inverter circuit. There was a problem that the water level could not be detected.
[0006]
In addition, the dv / dt noise generated in the motor output wire of the three-phase full-bridge inverter circuit controlled by the motor is particularly large. When the wire connected to the motor and the lead wire of the water level detection means come close, the water level is detected by electrostatic coupling noise. There is a problem that the means are likely to malfunction.
[0007]
The present invention solves the above-mentioned conventional problems, prevents malfunction of the water level detection means due to switching noise and strong electric field of the inverter circuit, and enables the oscillation circuit of the water level detection means to be mounted on the inverter control board, and is inexpensive and reliable. The purpose is to realize a control device for a washing machine with high performance.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention converts DC power of a rectifier circuit connected to an AC power source into AC power by an inverter circuit, and drives a motor for driving a stirring blade or a washing tub by this inverter circuit. The control means comprising a computer is configured to control the inverter circuit and the switching means for controlling the opening and closing of the water supply valve and the drain valve. The water level detection means for detecting the water level in the washing tub comprises a single coil and a single capacitor. It consists of an LC resonance circuit consisting of an LC resonance circuit consisting of a positive feedback amplifier and an LC resonance circuit whose resonance frequency changes due to pressure change due to the water level, and a low-pass filter circuit connected between the LC resonance circuit and the positive feedback amplifier circuit. .
[0009]
As a result, malfunction of the water level detection means due to switching noise or strong electric field of the inverter circuit can be prevented, the oscillation circuit of the water level detection means can be mounted on the inverter control board, and the inverter connected to the motor Since the malfunction of the water level detection means due to dv / dt noise and induction noise of the output wire of the circuit can be prevented, the wiring of the signal wires of the motor connection wire and the water level detection means can be simplified, and the reliability is low and high in reliability. A control device for a washing machine can be realized.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 of the present invention is an AC power source, a rectifier circuit connected to the AC power source, an inverter circuit that converts DC power of the rectifier circuit into AC power, and driven by the inverter circuit. A motor for driving the wing or the washing tub, a water supply valve for supplying water to the washing tub, a drain valve for draining the washing liquid of the washing tub, switching means for controlling opening and closing of the water supply valve and the drain valve, And a control means comprising a microcomputer for controlling the inverter circuit and the switching means, and a water level detection means for detecting the water level of the washing tub, wherein the water level detection means comprises a single coil and a single capacitor. the resonance frequency at pressure changes constitute from LC oscillating circuit consisting of an LC resonance circuit and the positive feedback amplifier which varies according to the water level, and the LC resonance circuit, the positive retrace A low-pass filter circuit is connected between the amplifier circuits to prevent malfunction of the water level sensor due to switching noise and strong electric field of the inverter circuit, and the water level sensor oscillation circuit can be mounted on the inverter control board Furthermore, it is possible to prevent malfunction of the water level detection means due to dv / dt noise and induction noise of the output wires of the inverter circuit connected to the motor, so that the wiring of the signal wires of the motor connection wires and the water level detection means is simplified. It is possible to realize a control device for a washing machine that is inexpensive and highly reliable.
[0011]
According to a second aspect of the present invention, in the first aspect of the present invention, the water level detection means configured by the LC oscillation circuit includes a low-pass filter circuit and a diode clamp circuit between the LC resonance circuit and the positive feedback amplifier circuit. is obtained by connecting, by adding a diode clamp circuit, destruction due to noise of a semiconductor integrated circuit constituting the feedback amplifier, it is possible to prevent a malfunction, prevent the destruction of the malfunction and the feedback amplifier circuit of the water level detecting means kill at.
[0012]
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the low-pass filter circuit is an RC filter circuit, and the time constant of the RC filter circuit is from 0.1 microsecond to 1 microsecond. It is set, and the malfunction of the water level detecting means due to the switching noise of the inverter circuit can be prevented without impairing the oscillation stability of the LC oscillation circuit.
[0013]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0014]
(Example 1)
As shown in FIG. 1, an AC power source 1 applies AC power to a rectifier circuit 3 via a line filter 2 and converts it into DC power. The rectifier circuit 3 constitutes a voltage doubler rectifier circuit. When the AC power supply 1 is a positive voltage, the capacitor 31a is charged by the diode 30a, and when the AC power supply 1 is a negative voltage, the capacitor 31b is charged by the diode 30b and connected in series. A double voltage DC voltage is generated at both ends of the capacitors 31a and 31b, and the double voltage DC voltage is applied to the inverter circuit 4.
[0015]
The inverter circuit 4 is composed of a three-phase full-bridge inverter circuit composed of six power transistors and antiparallel diodes, and is usually an intelligent power module (hereinafter referred to as a power transistor, antiparallel diode, drive circuit and protection circuit). , Called IPM). A motor 5 is connected to the output terminal of the inverter circuit 4.
[0016]
FIG. 2 is a sectional view showing an embodiment of the washing machine, in which the stirring blade 6 or the washing tub 7 is driven by the motor 5. Here, the motor 5 is constituted by a brushless DC motor 5. The position detection means 50 detects the relative position of the permanent magnet 52 and the stator 53 attached to the rotor 51 of the motor 5 and switches energization of the three-phase windings wound around the stator 53, so-called rotation. It detects a flow detection signal (hereinafter referred to as a CS signal), and is usually composed of a Hall IC.
[0017]
The water supply valve 8 controls the supply of tap water to the washing tub 7, and the drain valve 9 controls the drainage of the washing liquid in the washing tub 7. Electric control of the water supply valve 8 and the drain valve 9 can be performed by turning on and off the AC voltage by the switching means 10, and the switching means 10 is constituted by a bidirectional thyristor or a solid state relay.
[0018]
The control means 11 is mainly composed of a microcomputer and its peripheral circuits, and drives the motor 5 by controlling the inverter circuit 4 by the CS signal from the position detection means 50. Further, the switching means 10 is controlled to control the water supply valve 8 and the drain valve 9.
[0019]
The water level detection means 12 detects the water level of the washing tub 7, and is provided with an air trap at the lower part of the water receiving tank 13 and connected to the pressure detection part of the water level detecting means 12 provided at the upper part of the water receiving tank 13 by an air pipe. To do.
[0020]
The rotational torque from the output shaft 54 of the motor 5 is transmitted to the stirring blade 6 or the drive output shaft 16 of the washing tub 7 through the speed reduction mechanism 15. When the stirring blade 6 is driven, the number of rotations is reduced by the reduction ratio of the reduction mechanism 15. When the washing tub 7 is rotationally driven, the rotation of the motor 5 is directly transmitted by a clutch mechanism (not shown).
[0021]
As shown in FIG. 3, the water level detection means 12 forms a circuit unit, and the coil 120 a and the capacitor 120 b form the resonance circuit 120, and the low-pass filter circuit 122 is provided between the feedback amplification circuit 121 and the resonance circuit 120. Connected.
[0022]
In the feedback amplifier circuit 121, CMOS inverters 121a and 121b are connected in series to form a positive feedback amplifier, a self-bias resistor is connected between the input and output of the preceding CMOS inverter 121a, and the output terminal of the CMOS inverter 121b and the preceding CMOS are connected. A series circuit of a feedback resistor 121d and a capacitor 121e is connected between the input terminals of the inverter 121a.
[0023]
The positive feedback amplifier circuit 121 composed of the inverter logic operates as an RC oscillation circuit without the resonance circuit 120, and the oscillation frequency of the RC oscillation circuit is set to about 1/10 of the oscillation frequency of the LC resonance circuit. At the time of oscillation start-up, it starts as an RC oscillation circuit and is pulled to the resonance frequency of the resonance circuit 120 during the oscillation, the capacitor 121e becomes a mere input capacitor, and the feedback resistor 121d operates as a positive feedback resistor.
[0024]
The low-pass filter circuit 122 is a low-pass L-type filter composed of a resistor 122a and a capacitor 122b.
[0025]
Since the coil 120a and the capacitor 120b are disposed in the pressure detection unit, and the feedback amplifier circuit 121 is mounted on the control unit 11 formed of a microcomputer, the switching noise of the inverter circuit 4 becomes longer in distance and the water level detection unit 12 It becomes easy to get on the lead wire. Further, when the inverter circuit 4 and the control means 11 are mounted on the same substrate, noise further enters the feedback amplifier circuit 121 and is likely to malfunction. By connecting the low-pass filter circuit 122 to the input side of the feedback amplifier circuit 121 and reducing the switching noise added to the signal from the resonance circuit 120, malfunction of the LC resonance circuit can be eliminated.
[0026]
The pressure detection unit of the water level detection means 12 is configured as shown in FIG. 4, and when the ferrite core 124 on the diaphragm 123 moves up and down due to pressure, the inductance of the coil 120a changes, and the resonance frequency of the resonance circuit 120 changes. It is configured to change.
[0027]
In FIG. 4, part A is on the air hose side, and when the pressure in the lower part (P part) of the diaphragm 123 rises, the ferrite core 124 on the diaphragm 123 moves in the center direction of the coil 120a in proportion to the pressure because of the spring 125. As a result, the inductance of the coil 120a increases and the parallel resonance frequency f0 decreases. Usually, the resonance frequency f0 is set to an ultrasonic frequency of 20 to 40 kHz.
[0028]
As described above, according to the present embodiment, in the water level detection means 12 composed of the LC oscillation circuit, the low-pass filter circuit 122 is connected between the resonance circuit 120 and the feedback amplifier circuit 121, and the inverter enters the feedback amplifier circuit 121. Since the switching noise is reduced, the malfunction of the water level detecting means 12 due to the inverter switching noise can be eliminated, the oscillation of the LC oscillation circuit can be stabilized, and the inverter circuit 4 and the water supply valve can be provided on one control board. 8, the switching means 10 of the drain valve 9, the oscillation circuit of the water level detection means 12, the control means 11 of the inverter circuit 4 and the switching means 10 can be mounted, and further connected to the pressure detection part of the water level detection means 12 Even if the lead wire to be used is made long and close to the motor output wire, malfunctions and false detections can be eliminated.
[0029]
In the present embodiment, the low-pass filter circuit 122 is a low-pass RC filter, but the effect is the same even if the resistance is changed to an inductor. However, since the oscillation frequency of the oscillation circuit fluctuates and oscillation becomes unstable, there is a drawback that the inductance of the inductor cannot be increased.
[0030]
Although there is no particular problem even if the CMOS inverter is changed to a TTL inverter, it has been confirmed by experiments that an oscillation circuit using a logic circuit is less susceptible to noise malfunction than a feedback oscillation circuit using a high-impedance amplifier. Has been.
[0031]
(Example 2)
As shown in FIG. 5, a low-pass filter circuit 122 is connected between the resonance circuit 120 and the feedback amplifier circuit 121 constituting the water level detection means 12, and a diode clamp circuit 127 is further connected. The diode clamp circuit 127 includes a diode 127a that clamps on the positive side of the DC power supply voltage of the CMOS inverters 121a and 121b constituting the feedback amplifier circuit 121 and a diode 127b that clamps on the negative side.
[0032]
The diode clamp circuit 127 serves to protect the output of the CMOS inverter 121b. Further, if the diode clamp circuit 128 is connected to protect the input side of the CMOS inverter 121a, the effect is further increased. The positive-side clamp diodes 127a and 128a are turned on when the input signal voltage becomes higher than the diode cathode voltage, that is, the DC power supply voltage, and prevents the input voltage from becoming higher than the DC power supply voltage Va. It plays a role to escape to the side.
[0033]
The negative clamp diodes 127b and 128b prevent the feedback amplifier circuit 121 from malfunctioning and surge voltage destruction when the input signal is lower than the negative side of the DC power supply so as not to become below the negative voltage.
[0034]
The resonance circuit 120 is mounted on the pressure detection unit of the water level detection unit 12 and is disposed at the position of the water level detection unit 12 in FIG. 2, that is, above the washing tub 7. The feedback amplification circuit 121 is the same as the control unit 11. Since it is mounted on the substrate, noise due to inductive coupling or electrostatic coupling is induced when the signal line is lengthened. However, the low-pass filter circuit 122 and the diode clamp circuits 127 and 128 can prevent malfunction and surge destruction.
[0035]
As described above, according to the present embodiment, since the low-pass filter circuit 122 and the diode clamp circuits 127 and 128 are connected between the resonance circuit 120 and the feedback amplifier circuit 121, noise having a high frequency component is low-pass filter circuit 122. Since the diode clamp circuits 127 and 128 can absorb those having a low frequency component and a large noise energy, it is possible to realize a highly reliable water level detection means without malfunction or destruction.
[0036]
The pressure detection unit needs to be disposed on the upper part of the washing tub in order to improve safety. However, since the feedback amplification circuit 121 can be mounted on the same substrate as the control unit 11, the mounting board of the control unit 11 is mounted on the washing tub. Since it does not malfunction even if the lead wire is made long by placing it at the bottom of 7, the freedom of design is increased, and there is no malfunction even if the resonance circuit signal lead wire and the motor connection wire are brought close, simplifying the wiring it can.
[0037]
(Example 3)
The low-pass filter circuit 122 in FIG. 3 or FIG. 5 includes an RC filter in which a resistor 122a is connected in series with a signal, and a capacitor 122b is connected between the resistor 122a and the ground (−potential). This configuration has a high noise removal effect.
[0038]
Since many IPMs used in the inverter circuit 4 use an IGBT (Insulated Gate Bipolar Transistor) as a main switching semiconductor element, the switching time is from 0.1 microsecond to 0.5 microsecond.
[0039]
For this reason, if the RC time constant of the RC filter is set to be equivalent to or longer than the switching time of the main switching semiconductor of the inverter circuit 4, a sufficient effect can be obtained. If the time constant is set to a value larger than this, the Q of the resonance circuit 120 becomes low, the oscillation of the LC oscillation circuit becomes unstable, and conversely, malfunction is likely to occur.
[0040]
If the resistor 122a is set to 560Ω and the capacitor 122b is set to 470 pF, the time constant is about 0.26 microseconds. The fundamental frequency of switching noise with an IGBT switching time of 0.2 microseconds is 5 MHz, and the impedance of the capacitor 122b at that time is about 66Ω, so that a 1/10 attenuation effect can be obtained even in the fundamental wave of the noise component. I understand.
[0041]
Since the noise component has a higher distribution, the higher the frequency, the higher the attenuation factor and the greater the effect. When the capacitance of the capacitor 122b is increased, the impedance at the oscillation frequency of the water level detection means 12 is lowered and affects the oscillation frequency. Therefore, in order to increase the impedance in the vicinity of 40 kHz, the capacitor capacitance needs to be set to several hundred pF. There is.
[0042]
As described above, it not only attenuates the switching noise of the main switching semiconductor, but also has a great effect of attenuating the induced voltage due to the strong electric field in the short wave band or higher, and prevents malfunction caused by the strong electric field caused by in-vehicle radio or amateur radio. Can do.
[0043]
【The invention's effect】
As described above, according to the first aspect of the present invention, an AC power source, a rectifier circuit connected to the AC power source, an inverter circuit that converts DC power of the rectifier circuit into AC power, and the inverter A motor driven by a circuit to drive a stirring blade or a washing tub, a water supply valve for supplying water to the washing tub, a drain valve for draining the washing liquid of the washing tub, and controlling opening and closing of the water supply valve and the drain valve Switching means, a control means comprising a microcomputer for controlling the inverter circuit and the switching means, and a water level detection means for detecting the water level of the washing tub, wherein the water level detection means comprises a single coil and a single coil. constitute from LC oscillating circuit consisting of an LC resonance circuit and the positive feedback amplifier which varies the resonance frequency by the pressure change due is constituted by one capacitor level, the LC co A circuit, since connecting a low pass filter circuit between the positive feedback amplifier circuit, it is possible to prevent malfunction of the water level sensor due to switching noise and high electric field of the inverter circuit, mounting the water level sensor oscillator circuit inverter control board In addition, it is possible to prevent malfunction of the water level detection means due to noise in the output wires of the inverter circuit connected to the motor, so the wiring of the signal wires of the motor connection wires and the water level detection means can be simplified. Therefore, it is possible to realize a control device for a washing machine that is inexpensive and highly reliable.
[0044]
According to the invention described in claim 2, since the water level detection means constituted by the LC oscillation circuit has the low-pass filter circuit and the diode clamp circuit connected between the LC resonance circuit and the positive feedback amplifier circuit, the diode by adding a clamping circuit, destruction due to noise of a semiconductor integrated circuit constituting the feedback amplifier, it is possible to prevent a malfunction, wear destruction of malfunction feedback amplifier circuit of the water level sensing means in prevention.
[0045]
According to the third aspect of the present invention, the low-pass filter circuit is an RC filter circuit, and the time constant of the RC filter circuit is set from 0.1 microsecond to 1 microsecond. Highly reliable washing machine controller that does not malfunction not only with inverter noise but also with strong electric field of radio frequency, because it attenuates noise or higher frequency noise and does not affect the oscillation frequency signal of water level detection means Can be realized.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a control device for a washing machine according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a washing machine provided with the control device for the washing machine. FIG. 4 is a cross-sectional view of the main part of the pressure detection unit of the water level detection means used in the control device of the washing machine. FIG. 5 shows the washing machine according to the second embodiment of the present invention. Circuit diagram of water level detection means used for control equipment [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power source 3 Rectifier circuit 4 Inverter circuit 5 Motor 6 Stirring blade 7 Washing tub 8 Water supply valve 9 Drain valve 10 Switching means 11 Control means 12 Water level detection means 120 Resonance circuit 121 Feedback amplification circuit 122 Low-pass filter circuit

Claims (3)

AC power source, a rectifier circuit connected to the AC power source, an inverter circuit that converts DC power of the rectifier circuit into AC power, a motor that is driven by the inverter circuit and drives a stirring blade or a washing tub, A water supply valve for supplying water to the washing tub, a drain valve for draining the washing liquid of the washing tub, a switching means for controlling opening and closing of the water supply valve and the drain valve, a microcomputer for controlling the inverter circuit and the switching means And a water level detecting means for detecting the water level of the washing tub, wherein the water level detecting means is composed of a single coil and a single capacitor, and an LC whose resonance frequency changes due to a pressure change due to the water level. constitute from LC oscillating circuit consisting of the resonant circuit and the positive feedback amplifier, and the LC resonant circuit, low-pass filter between the positive feedback amplifier circuit Washing machine controller connected to road. 2. The washing machine control device according to claim 1, wherein the water level detection means configured by the LC oscillation circuit includes a low-pass filter circuit and a diode clamp circuit connected between the LC resonance circuit and the positive feedback amplifier circuit. The washing machine control device according to claim 1 or 2, wherein the low-pass filter circuit comprises an RC filter circuit, and a time constant of the RC filter circuit is set from 0.1 microsecond to 1 microsecond.

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