JPH0456929B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a hot water level detection circuit used in a hot water supply device for a die casting machine, and in particular, to electrically detect the state in which a ladle has reached the molten metal in a metal melting furnace. This invention relates to a hot water level detection circuit.

[Prior art and its problems]

Conventionally, as shown in FIG. 2, this type of molten metal level detection circuit has been constructed by attaching two electrode rods 10 and 12 to a part of the ladle that pumps up the molten metal, and attaching one pair to each electrode rod. A known configuration is such that these conductors are connected to a power source 18 via a hot water level detection relay 14 and a disconnection detection relay 16, respectively. However, the hot water level detection circuit configured in this way requires two conductors for each electrode rod, and since the circuit is configured using the coil resistance of each relay, a special coil resistance is required. relay is required. Therefore, not only does the manufacturing cost of the circuit increase, but also disconnection accidents are likely to occur, and since the circuit is a contact point, there are problems such as contact failure.

Furthermore, as an improvement of this type of hot water level detection circuit, one constructed as shown in FIG. 3 is also known.
That is, in the case shown in FIG. 3, a resistor 26 is connected between the sensing electrodes 22 and 24 attached to the ladle part 20, and other resistors 28, 30, 32 and the power source 3 are connected.
4 constitute a bridge circuit, and a sensing electrode 22,
A first diode 36 and a first photocoupler 38 are connected in series, and a second diode 40 and a second photocoupler 42 are connected in series. The relay 4 is connected in parallel with the wires connected to the
4 and a relay 4 operated by the second photocoupler 42
6, it is determined which photocoupler the current is flowing through. However, in the hot water level detection circuit having the above configuration, it is necessary to adjust the bridge circuit consisting of the resistors 26, 28, 30, and 32 so that it is always in a balanced state, and since a photocoupler is used, this type of There are many restrictions on installation conditions, such as the need for the atmosphere in which the circuit is used to be always clean, and if these conditions are not met, there are problems such as malfunctions.

[Purpose of the invention]

The object of the present invention is to overcome all the problems of the conventional hot water level detection circuit described above, to provide a water heater that has a simple configuration, has almost no restrictions on usage conditions, is easy to maintain, and is easy to handle without malfunctions. To provide a hot water level detection circuit.

[Key points of the invention]

The hot water level detection circuit of the hot water supply device according to the present invention connects a short circuit resistor between a pair of electrode rods for detecting the hot water level, connects a power source to these electrode rods, and A comparator is provided for inputting a signal detected from a part of the conductive wire connected to the power source together with a predetermined reference signal for comparison and outputting a hot water level detection signal and a cross section detection signal, and the one electrode rod and the power source are connected to each other. A series resistor is connected to the conductor to be connected, a conductor is led out from the connection point of the series resistor with the electrode rod, and the conductor is passed through a low-pass filter to output a hot water level detection signal and a disconnection detection signal, respectively. Detected voltage when the electrode rods are connected to one input terminal of each of the first comparator and the second comparator, and the pair of electrode rods are short-circuited to the other input terminal of the first comparator by a short-circuit resistor. connected to a first level setting device for inputting a first comparison reference signal that is smaller and set higher than the detection voltage when a short circuit is formed by the molten metal resistance of the pair of electrode rods; The other input terminal of the second comparator has a detection voltage that is higher than the detection voltage when the pair of electrode rods are short-circuited by the short-circuit resistor and when the gap between the pair of electrode rods is open, that is, there is an infinite resistance. It is characterized in that it is connected to a second level setter for inputting a second comparison reference signal set to be lower than the detection voltage.

In the hot water level detection circuit described above, the hot water level detection signal output from the first comparator is output under the condition that the output voltage of the low-pass filter is smaller than the first comparison reference voltage whose level is set by the first level setter. The disconnection detection signal output from the second comparator is set so that it is output under the condition that the output voltage of the low-pass filter is higher than the second comparison reference voltage whose level is set by the second level setter. be able to.

[Embodiments of the invention]

Next, an embodiment of a hot water level detection circuit for a water heater according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block circuit diagram showing an embodiment of the hot water level detection circuit of the present invention. That is, in FIG. 1, reference numerals 50 and 52 indicate a pair of electrode rods each attached to a part of the ladle for detecting the level of the molten metal in the melting furnace. However, these electrode rods 50 and 52 are connected to a constant voltage power source 58 via conductive wires 54 and 56, respectively, and one conductive wire 54
A first resistor 60 is connected to the electrode rods 50 and 52, and a second resistor 62 is connected between the connecting conductors 54 and 56 of the electrode rods 50 and 52.

Therefore, in the present invention, a low-pass filter 64 is provided, and the input signal of the low-pass filter 64 is transmitted between the first resistor 60 of the conductive wire 54 and the electrode rod 50.
A first comparator 66 outputs a hot water level detection signal Sp and a second comparator 68 outputs a disconnection detection signal S _c , respectively, and outputs the output signal of the low-pass filter 64 from a point A between the two.
The circuit is configured so that the input terminals are input to one input terminal of each of the two input terminals. The first comparator 66 is configured to input a comparison reference voltage whose level has been set by a first level setter 70 to the other input terminal of the first comparator 66.
Further, the comparison reference voltage whose level has been set by the second level setter 72 is also input to the other input terminal of the second comparator 68 . In the case of the first comparator 66, the input terminal of the comparator is connected such that the hot water level detection signal S _p is output under the condition that the output voltage of the low-pass filter 64 < the comparison reference voltage whose level is set by the first level setter 70;
The disconnection detection signal S _c is configured to be output under the condition that the power voltage of the low-pass filter 64 > the comparison reference voltage whose level is set by the second level setter 72 .

In the hot water level detection circuit having the above configuration, the following three types of signal voltage at point A of the conducting wire 54 input to the low-pass filter 64 can be considered.

Voltage V _A1 when _the molten metal level is detected by _the electrode rods ₅₀ and ₅₂ ( _short circuit due to the resistance _{of the} molten _{metal R} V _S ...(1) However, R ₁ : Resistance value of the first resistor 60 R ₂ : Resistance value of the second resistor 62 R _X : Specific resistance value of the molten metal V _S : Voltage value of the constant voltage power supply 58 Hot water Voltage when the surface is not detected V _A2 V _A2 = R ₂ / R ₁ + R ₂ · V _s ... (2) External voltage at the conductors 54 and 56 connecting the electrode rods 50 and 52 and the constant voltage electrode 58 The voltage when the wiring part (external connection terminals K ₁ , K ₂ to electrode rods 50, 52 and resistor 62) is disconnected is V _A3 V _A3 ≒ V _S ... (3) The relationship between the above signal voltages is V _A1 <V _A2 <V _A3 .

Therefore, the first level setter 70 is set so that the comparison reference voltage V _C1 of the first comparator 66 satisfies the following equation.

V _{A1 ＜} V _{C1 ＜} V _{A2 ∴R 2}・R _X ／ _{R 1 (} R _{2 ＋ R
2.Vs} (4) Furthermore, the second level setter 72 is set so that the reference voltage V _C2 for comparison of the second comparator 68 satisfies the following equation.

V _A2 <V _C2 <V _A3 ∴R ₂ /R ₁ +R ₂・Vs<V _C2 <V _S ...(5) According to the hot water level detection circuit of the present invention configured in this way, point A of the conductor 54 By inputting the signal voltage at to the first comparator 66 and the second comparator 68 through the low-pass filter 64, if the electrode rods 50 and 52 are in a state of detecting the hot water level, based on the above formula (1), According to the above equation (4), the first comparator 66 outputs the hot water level detection signal S _p under the condition of V _A <V _C1 . In addition, electrode rods 50, 52
If is not detecting the hot water level, the above equation (2)
Based on the above formula (4), the first comparator 66
In this case, the hot water level detection signal is not output under the condition of V _A > V _C1 .

On the other hand, if a break occurs in the external wiring,
Based on the above equation (3) and the above equation (5), the second comparator 68 outputs the disconnection detection signal Sc under the condition of V _A >V _c2 .

〔Effect of the invention〕

As is clear from the embodiments described above, according to the present invention, a single conductive wire is led out from each of the electrode rods for detecting the hot water level and connected to a power source, a resistor is connected between the electrode rods, and a resistor is connected between the electrode rods. A simple circuit configuration can be achieved by connecting a comparison resistor to one of the conductors, extracting the required signal from a part of the conductor, and introducing it to a comparator that outputs a hot water level detection signal and a disconnection detection signal, respectively. Furthermore, appropriate hot water level detection and disconnection detection can be achieved with high precision. In the present invention, the comparison reference voltage input to the comparator can be easily adjusted at low cost using a voltage regulator consisting of a simple variable resistor. Therefore, according to the hot water level detection circuit of the present invention, it can be manufactured at low cost with a simple circuit configuration without using a complicated bridge circuit as in the past, and it can be manufactured with high precision without the need for complicated adjustment work. It is possible to detect hot water level and disconnection.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an example of a hot water level detection circuit of a water heater according to the present invention, FIG. 2 is a schematic wiring diagram showing an example of a configuration of a hot water level detection circuit of a conventional water heater, The figure is an electrical circuit diagram of a conventional improved hot water level detection circuit. 50, 52... Electrode rod, 54, 56... Conductor wire,
58... constant voltage power supply, 60... first resistor, 62
...Second resistor, 64...Low pass filter, 6
6...First comparator, 68...Second comparator, 70...First level setter, 72...Second
Level setter.

Claims (1)

[Claims] 1. A short-circuit resistor is connected between a pair of electrode rods for detecting the hot water level, a power source is connected to these electrode rods, and a conductor wire is connected to the power source of one of the electrode rods. A comparator is provided for inputting the signal detected from a part of the electrode together with a predetermined reference signal for comparison and outputting a hot water level detection signal and a disconnection detection signal, and a series resistor is connected to the conductor connecting the one electrode rod and the power source. A first comparator and a second comparator are connected to a first comparator and a second comparator, each of which outputs a hot water level detection signal and a disconnection detection signal. is connected to one input terminal of each of the first comparators, and the other input terminal of the first comparator has a detection voltage smaller than the detection voltage when the pair of electrode rods are short-circuited by a short-circuit resistor. The electrode rod is connected to a first level setting device for inputting a first comparison reference signal set to be higher than the detection voltage when a short circuit is formed by the molten metal resistance, and the other of the second comparator The input terminal of the electrode is set to be higher than the detection voltage when the pair of electrode rods are short-circuited by a short-circuit resistor, and lower than the detection voltage when the pair of electrode rods is open, that is, there is an infinite resistance. A hot water level detection circuit for a water heater, characterized in that it is connected to a second level setter for inputting a second reference signal for comparison. 2. In the hot water level detection circuit for the water heater according to claim 1, the hot water level detection signal output from the first comparator is the same as the output voltage of the low-pass filter whose level is set by the first level setting device. Output under conditions lower than the comparison reference voltage of 1,
The disconnection detection signal output from the second comparator is set so that it is output under the condition that the output voltage of the low-pass filter is higher than the second comparison reference voltage whose level is set by the second level setter. Hot water level detection circuit for water heater.