JPS59108918A - Liquid level detecting device - Google Patents

Abstract

PURPOSE:To avoid erroneous operation due to the count up state at the time of starting and the like, by resetting a counting circuit, which outputs a liquid level signal, based on an operation stopping command of a device. CONSTITUTION:When a liquid level element 6 emerges from liquid to air and detects the liquid level, resistance is rapidly decreased, and the potential at a point (a) is rapidly decreased. The potential at a point (b) shows a slow action. In a comparator 13, the potentials at the points (a) and (b) are compared. A pulse signal is outputted from a pulse circuit 16, and counted by a counter circuit 18. The result is outputted to an output circuit 20 as the detected liquid level. A reset part 18a of the counting circuit 18 is connected to the grounding side by a reverse contact point 21 for the operation linking signal of an equipment to be controlled. A reset part 18b becomes an opened state by the operation starting command of the equipment to be controlled. A high state is kept and a counting operation state is achieved. The counting circuit 18 is cleared by the operation stopping command. Therefore the count up state is not yielded at the time of starting, and the erroneous operation is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an FC liquid level detection device in which the state of the liquid level in an apparatus requiring liquid level management is detected by a liquid level detection element such as a positive resistance characteristic temperature element or a negative resistance characteristic temperature element. This is related to the improvement of.

FIG. 1 shows what has been conventionally considered as this type of liquid level detection device. In the figure, t1+ +''tt transformer 2) is a rectifier circuit, (3) is a smoothing capacitor, and (4)
is a stabilized power supply section, (5) is a current control resistor for preventing excessive current from flowing into the detection thermistor element, (6) is a liquid level detection element composed of a thermistor, and (7) is an FKT input with high human power impedance. The input operational amplifier 8) is a capacitor for holding the output voltage of the operational amplifier (7), and is used as an analog memory that holds a voltage value for a certain period of time. In the 12IVi voltage divider circuit, resistors [+01, (Ill
The output voltage of the eight-point peak detection circuit (9) is divided into predetermined values. Q31H This is a comparator that compares the output voltage of the peak detection circuit (9) divided by the voltage dividing circuit 021 (potential at point b) with the direct detection signal voltage from the detection element (potential at point a). 03) also capacitor (8)
It is constructed using a high input impedance FET input type operational amplifier to maintain the voltage value for as long as possible. (151 is an inverter circuit that inverts the output signal,
The signal is pulsed by the oe+Vi differentiator circuit, and the counting circuit (1
8) into the input section (lfla) and count a predetermined number of times. 071 is a timer circuit that clears the count of the counting circuit αya at fixed time intervals, cA is an output circuit, and the counting circuit (1
Due to the change in the output of 8), the relay *aan becomes a transistor (4).
It was turned on/off and output to the outside.

In the circuit configured in this way, the liquid level detection element (
When 6) comes out from the liquid into the air and detects the liquid level, since the liquid level detection element (6) is composed of a thermistor, it rapidly self-heats, the resistance decreases drastically, and the potential at point a rapidly decreases. . However, the potential at point b maintains the potential at the time when the detection element (6) was in the liquid for several seconds to several tens of seconds, so it operates slowly, and the comparator 03) detects the potential at points a and b. Compare and output, inverter circuit (+51, pulse circuit QB+
A pulse signal is outputted, counted by the counting circuit (18), and if a predetermined number of times is counted within a predetermined time determined by the timer circuit (+71), it is determined as liquid level detection and output to the output circuit -, which is output to the timer circuit (171). When the timer is up, that is, a predetermined time has elapsed before the count is completed, the output section (1”a)
Therefore, the pulse signal is sent to the reset section (1 (1) of the counting circuit (1 (8)).
8a), the counting circuit 08) cancels counting, determines that the liquid level exists, and simultaneously initializes the timer circuit.
Start measuring the predetermined time. In other words, the timer circuit Q7I completely ignores the conditions on the liquid level detection side, and when the predetermined time elapses,
Since the counting of the counting circuit is always canceled, it is canceled just before the liquid level is detected, and even if the liquid level detection signal is output with one more count, the counting is canceled, and counting starts again, making it impossible to accurately measure the liquid level. It was difficult to detect without delay. In addition, the timer circuit a7111- may be set for a relatively long time (30 to 45 seconds), and the timer circuit 071 is expensive due to its configuration using an IC with a built-in count.

tyc, the determination of the predetermined time of this timer circuit αη has the above-mentioned problem, so it is difficult to determine the predetermined time of the timer circuit αη. , the optimum time setting is difficult because it is determined based on various factors determined by load conditions, compressor capacity, piping conditions, and applied temperature conditions, and there are risks such as malfunction due to early detection and equipment damage due to delayed detection. It had some problems.

In addition, in such automatically controlled equipment, there is an inevitable time delay in the oil pump, etc. used immediately after restarting, and the oil pressure or oil level is not immediately secured and the detection element (6)
The system sometimes detected the oil level, and it could malfunction immediately after stopping and just before counting up.

This invention detects the peak value of a voltage signal according to a device for managing the liquid level using a liquid level detecting element, and compares the divided voltage with the voltage signal from the liquid level detecting element, and calculates the comparison value. By counting the output signal of a comparator that generates an output signal according to the count value, and resetting a counting circuit that outputs a liquid level signal when the counted value reaches a predetermined number based on the operation stop command vc of the device, It is an object of the present invention to provide a liquid level detection device that does not malfunction due to a count-up state at the time of startup.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. The reset section of the counting circuit (18) (
18a) is the reverse contact (21) of the operation interlock signal of the controlled equipment.
) to the ground side (when the reset part of the circuit C used in the counting circuit (18) is not reset by the LOW level)
has been done. (I9) is a pull-up resistor for signal stabilization.The reverse contact (21) of this operation interlock signal is normally the b contact of an electromagnetic switch, that is, when the electromagnetic switch is energized, it becomes disconnected and deenergized. It uses contacts that become conductive when

With this configuration, the counting circuit (181) changes the operating state according to the operation start command of the controlled device, that is, the reset section (1s
b) is in the open state, and is held in the H, TGH state by the pull-up resistor (191), and the counting operation state pVC is in place.In addition, the operation is prohibited by the operation stop command of the controlled equipment, that is, the reset part (IBb) is in the closed state. Then, LO
It is held in the W state and the counting circuit (18) is prohibited from counting.

Therefore, counting is enabled only when the controlled device is in operation, and liquid level detection becomes possible only in operating conditions that require liquid level management. This can also be applied to prevent malfunctions in devices where the controlled device is driven by a pump or the like, where the liquid level is high when the bong is in operation, and the liquid level is low when the pump is stopped.

In addition, normally, controlled equipment is often stopped due to certain conditions, and in refrigeration equipment, etc., automatic operation is prevented by temperature switches and pressure switches (not shown) K, but the above-mentioned As mentioned above, after the first restart, the liquid level or oil level is insufficient and the liquid level is often detected. However, in the present invention, the counting circuit is not cleared from the stop +lK, and the count-up state occurs at the time of starting at 7ζ. This will prevent malfunctions.

In the above embodiment, the counting circuit is cleared by the stop signal of the controlled device, but depending on the frequency of operation/stopping of the controlled device, when the frequency tL exceeds a certain value, clearing the counting circuit is prohibited. , and the number of counts is increased, it is possible to detect abnormally frequent repetition of operation/stopping, and it is also possible to detect abnormal changes in the liquid level in this state.

As described above, according to the present invention, the peak value of the liquid level detection element disposed at the liquid level detection position of the device is detected and divided into nine parts,
This partial pressure signal is compared with the signal from the liquid level detection element (forced by the liquid level detection element), and the count is cleared in the counting circuit that counts the output signal of the comparator that generates the output 4M according to the comparison value. Since this is done by the following, there are no malfunctions during startup, and reliability is improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional liquid level detection device, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. In the figure, (6) is a liquid level detection element, (9) is a 17t beam detection circuit, (13) is a comparison circuit, (16) is a differential circuit, (1
81 is a counting circuit, (2D is a clearing contact, and (4) is an output circuit. In the figure, the same reference numerals indicate the same or equivalent parts. Agent Shin Kuzuno - '+1 - Director General's Palace 1 .Display of the matter Patent application No. 57-219970 2,
Name of the invention Liquid level detection device; 3. To Hitoshi Katayama, representative of the person making the amendment: Detailed description of the invention in the specification and drawings. 6. Contents of the amendment (1) In the second line of page 6 of the specification, the 1st part (18a) J is corrected to 1st part (18b) yo. (2) Figure 2 of the drawing is corrected as shown in the attached sheet. that's all

Claims (1)

[Claims] A liquid level detection element that is placed at the liquid level detection position of a device that requires liquid level management and generates a voltage signal according to the liquid level, and a peak value of the voltage signal output of this liquid level detection element. A peak detection circuit that detects and holds it for a predetermined time, a voltage dividing circuit that divides the voltage signal detected by this peak detection circuit, and a signal voltage value from the divided voltage and the liquid level detection element. A comparator that compares and generates an output signal according to the comparison value, a counting circuit that counts the output signal of this comparator and generates an output signal when a predetermined number of counts is reached, and a signal that stops the operation of the above device. A liquid level detection device comprising: means for setting the above-mentioned counting circuit kIJ.