JP2734120B2 - Water level detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level detection device used for an electric washing machine or an electric dishwasher.

2. Description of the Related Art Conventionally, a water level detection method of this type of water level detection device will be described with reference to FIG. In other words, while the water level sensor input is input as a square wave pulse, the pulse of the water level sensor input during 100 ms is counted 10 times (12 times at 60 Hz) at 50 Hz with zero volt pulse (ZVP) based on AC input. The water level was detected by counting the number and processing it with a microcomputer or the like.

Problems to be Solved by the Invention However, in such a configuration, since the frequency of the AC input is used as a reference, the frequency is 50 Hz or
In an area where the cycle is stable at 60 Hz, the frequency of the AC input may be counted and each load such as a water level detection device may be controlled based on the frequency. However, in an area where the frequency cycle itself is unstable ( For example, in a foreign country), the frequency to be used as a reference includes an error, so that the error of the water level detection device increases. As a result, the washing machine does not detect that water is full even if the water is filled up, or does not detect that the water is completely drained even if all the water is drained, and the process stops. there were.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a water level detection device that can obtain stable accuracy even when the power supply frequency fluctuates and that does not require a large change in a conventional water level detection sequence (such as a microcomputer program).

Means for Solving the Problems In order to achieve the above object, the present invention provides a water level detecting means for detecting a water level in a tank and converting it into an electric signal, a system clock oscillating means, and an AC linked to an AC power supply frequency. Zero volt detection means, and control means for inputting respective output signals of the water level detection means, the system clock oscillation means and the AC zero volt detection means, wherein the control means is based on an output signal of the AC zero volt detection means. First, the output signal of the water level detection means is counted within the reference time, and the input is switched within the next reference time to count the output signal of the system clock oscillation means. The switching is repeated alternately, and the count number of the output signal from the system clock oscillating means within the reference time is stored at 50 Hz or Is
The frequency error of the AC power supply is detected by comparing with the reference count number within the reference time corresponding to the frequency of 60 Hz, and the water level value is corrected in accordance with the frequency error of the AC power supply.

Operation The water level detection device of the present invention adopts the configuration described above, and the control means stores in advance the count number of the output signal from the system clock oscillation means within the reference time of the actually measured AC zero volt signal within the reference time. 50Hz or
By constantly comparing with the reference count number within the reference time corresponding to the frequency of 60 Hz, it is possible to constantly monitor the frequency of the AC power supply, detect frequency errors, and reference the zero volt signal of the AC power supply This is to correct the value of the water level detecting device.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of a washing machine. In the drawing, reference numeral 11 denotes a water level detecting means, in which a resonance circuit is formed by a coil 101 and capacitors 102 and 103, and its output is amplified and shaped by inverters 104 and 105. When the diaphragm 106 is formed by a change in pressure, the core 107 moves to change the inductance of the coil 101, and the oscillation frequency changes. As a result, a change in the water level appears as a change in the oscillation frequency. Reference numeral 12 denotes a system clock oscillating means, which includes a vibrating element 201 such as crystal and capacitors 202 and 203. 13 is AC zero volt detection means, 14
Is a control means, which is composed of an input switching means 401, a counter 402, and a correction means 403, 15 is an operation display means comprising switches, displays, and the like, and 16 is a power supply means for supplying power to the control means 14. is there. 17 is a switching device for controlling each external load, 18 is a motor, 19 is a drain valve driving means, 20 is a water supply valve, and 21 is a power supply for supplying power to the whole.

FIG. 2 shows an example of use in an electric washing machine, in which water enters the tank 3 and the water level is transmitted to the water level detecting means 23 via a pressure hose 33. Reference numeral 6 denotes a motor, 7 denotes a drain valve driving means, 10 denotes a drain valve, and 24 denotes a control unit including control means and the like.

The basic operation is as follows. Power is always supplied to the control means 14 from the power supply 21 via the power supply means 16, and the operation is performed by operating the switch of the operation display means 15. To start the switching device 17 in accordance with the sequence stored in the control means 14.
To the motor 18, the drain valve driving means 19, and the water supply valve 2.
The load of 0 is operated, and the display of the operation display means 15 is further operated to advance the washing operation.

As the operation of the water level detection device, a reference time based on the output signal of the AC zero volt detection means 13 is set in the control means 14, and the pulses of the output signal of the water level detection means 11 are counted within that time, Counter 40 after time has passed
The input to 2 is switched to the input from the system clock oscillating means 12 by the input switching means 401, and the pulses of the output signal of the system clock oscillating means 12 are counted. The number of pulses of the system clock is compared with a value stored in advance by the control means 14 (a value when the frequency error of the power supply 21 is zero).
If the frequency is low and smaller than the reference value, it is determined that the frequency is high, the number of pulses of the water level detecting means 11 measured before is corrected by the correcting means 403, and the frequency error of the power supply frequency 21 is zero. After performing the post-processing.
By doing so, even if the frequency of the power supply 21 is misaligned, it can be converted to a regular value, so that the processing in the subsequent process can be handled exactly as in the regular case.

In the case of the above method, the system clock oscillation means 12
Therefore, the frequency of the system clock oscillating means 12 is important, and it is desirable to use a vibrator 201 having higher stability.

Further, according to the above embodiment, the AC zero volt detecting means 13
Since the measurement reference time is determined based on the output signal of
It becomes very easy to perform control that matches the timing with the power supply 21. For example, a triac is often used inside the switching device 17, but when controlling the load with this triac, it is important to output an output signal in synchronization with AC zero volts. Therefore, in the case of the control means 14, which often uses a microcomputer, the timing is
All programs are often programmed in accordance with the timing of the output signal of the AC zero volt detecting means 13. In such a case, it is extremely difficult to perform only the processing of the output signal of the water level detecting means 11 at another timing in a program.Therefore, by using the method of the present invention, the timing is adjusted to zero AC volts. In addition, there is a great effect that the frequency fluctuation can be corrected.

FIG. 3 shows the contents of the above embodiment using waveforms.
A zero volt pulse (ZVP) is generated, and the times of 10 times the time (in the case of 50 Hz, and the same at 60 Hz if 12 times) are set as the reference times A and B. In the first period A, the pulses of the water level detection means 11 (water level sensor) are counted and this is set to fs. In the next B period, the number of pulses of the system clock oscillation means 13 (microcomputer clock input) is counted. And this is fm. Then, from the pulse count number fr when the AC power supply frequency is normal stored in the control means 14, the corrected pulse number fn is determined by the conversion of fn = fr-K (fa-fm). By this method
A constant value fm is obtained even if the AC power supply frequency fluctuates.

Effects of the Invention As is apparent from the above description, according to the present invention, AC
With the power supply pulse as a reference, the water level detection means pulse and the system clock pulse are counted alternately and compared sequentially, so that the water level detection means responds to frequency fluctuations of the AC power supply in a form synchronized with the AC power supply. Since the number of read pulses can be corrected, stable accuracy can be obtained even in a region where the frequency variation is large, and the reliability of the device can be improved.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an electric washing machine using a water level detecting device according to an embodiment of the present invention, FIG. 2 is a sectional view of the electric washing machine, FIG. 3 is a waveform diagram of each part, and FIG. It is a waveform diagram of each part of a conventional example. 11 ... water level detecting means, 12 ... system clock oscillating means, 13 ... AC zero volt detecting means, 14 ... control means.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-222222 (JP, A) JP-A-53-106076 (JP, A) JP-A-62-287180 (JP, A)

Claims (1)

(57) [Claims] 1. A water level detection means for detecting a water level in a tank and converting the water level into an electric signal, a system clock oscillation means,
AC zero volt detection means linked to the power supply frequency, the water level detection means, the system clock oscillation means and the AC
Control means for inputting respective output signals of the zero volt detection means, the control means providing a predetermined reference time based on the output signal of the AC zero volt detection means, and first, the water level detection means within the reference time After the output signal of the system clock is counted, the input is switched within the next reference time to count the output signal of the system clock oscillating means, and this switching is repeated alternately. The control unit detects the frequency error of the AC power supply by comparing the count number with the reference count number within the reference time corresponding to the frequency of 50 Hz or 60 Hz, which is stored in advance by the control unit, and responds to the frequency error of the AC power supply. Water level detector that corrects the water level.