JP3457827B2 - Water tank heating device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for an aquarium, and particularly to an aquarium for breeding aquarium fish and small aquatic animals or a water tank for growing aquatic plants. The present invention relates to a heating device for a water tank used. 2. Description of the Related Art FIG. 4 shows a heater used in a conventional water tank heating device. In FIG. 4, reference numeral 21 denotes a cylindrical hollow tube having a bottom made of crystallized glass such as quartz or β-spodumene (β-LiAlSi 2 O 6); 22, a heating element made of nichrome or the like provided in the tube 21; Reference numeral 23 denotes a sealing stopper for sealing the opening of the tube 21. A power supply wiring 24 is connected to a heating element 22 made of nichrome or the like provided in a tube 21, and is drawn outside through a sealing plug 23. The power supply wiring 24 led out is connected to a commercial power supply or the like. In addition, the hollow portion in the pipe 21 may be filled with asbestos or the like. [0003] The heater 20 used in such a water tank heating device is used, for example, installed at an appropriate location in the water tank, and water heated by the heater 20 is supplied to the water tank by a circulation device (not shown). By circulating water, the entire water in the aquarium is heated, and by maintaining the water temperature in the aquarium at a constant temperature, it is possible to raise tropical fish and grow aquatic plants. [0004] Further, a water tank heater provided with a temperature detecting element (not shown) such as a thermistor or a thermostat for stopping power supply to the heating element 22 when the water temperature in the water tank reaches a predetermined temperature. Proposed. Such a temperature detecting element is provided on the power supply wiring 24 in the pipe 21 of the water tank heater 20, or provided at a position completely different from the water tank heater 20. [0005] However, in the conventional heating device for a water tank, when the water temperature in the water tank reaches a predetermined temperature or higher, a temperature detecting element for stopping the power supply to the heating element 22 is provided. Although provided, even if the water tank heater 20 is suddenly pulled out of the water tank or the water tank rolls over due to an earthquake or the like, the energization state to the heating element 22 is maintained unless the temperature detecting element detects that the temperature is equal to or higher than a predetermined temperature. The heating element 22 continues to generate heat. As a result, there has been a serious problem of causing a personal injury or a fire accident.
The present invention has been made in view of such a problem of the conventional apparatus, and when the heater is pulled out of the water tank while being connected to the power supply, the heater does not continue to generate heat. An object of the present invention is to provide a heating device for use. [0006] In order to achieve the above object, a heating device for a water tank according to the present invention comprises a heater for heating water in the water tank, and a temperature detecting element for detecting the temperature of the water in the water tank. When the water temperature in the water tank detected by the temperature detecting element is equal to or lower than a predetermined temperature, electricity is supplied from the commercial power supply to the heater, and when the water temperature detected by the temperature detecting element is equal to or higher than the predetermined temperature, the heater is turned on. In the water tank heating device for stopping the power supply to the heater, the heater is constituted by a ceramic heater, and a current flowing in a state where the ceramic heater is energized is detected. The current supply to the heater is stopped, and the current is detected a predetermined time after the power supply to the heater is started. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a view showing one embodiment of a water tank heating apparatus according to the present invention, wherein 1 is a commercial power supply, 2 is a heater,
A power supply control circuit 3 controls power supply to the heater 2 as a whole. The heater 2 is constituted by a ceramic heater in which a heating element is embedded in a rod-shaped or plate-shaped ceramic body. Ceramic heaters have good thermal efficiency, low power consumption, and are compact and robust heating devices for aquariums. They also have high chemical resistance and can be used for long periods in freshwater or seawater. [0010] Such a ceramic heater is constituted by embedding a heating element made of tungsten (W), molybdenum (Mo), molybdenum manganese (MoMn) or the like in alumina ceramic, or a tungsten heater in silicon nitride ceramic. (W), molybdenum (Mo), molybdenum manganese (MoMn), and the like. FIG. 2 shows the relationship between the temperature and the resistance ratio of such an alumina heater and a silicon nitride heater. In FIG. 2, A is a heater in which a heating element made of molybdenum manganese is embedded in alumina ceramics, B is a heater in which a heating element made of tungsten is embedded in silicon nitride ceramics, and C is a conventional heater made of Ni-Cr. Show. Ni of C
The resistance ratio (Rt / Rt ₂₃ ) based on the specific resistance at 23 ° C. of the Cr heater does not change at all even if the temperature rises, whereas the ceramic heaters A and B are proportional to the temperature change. The specific resistance changes. Therefore, in the ceramic heaters A and B, when the temperature of the heater itself increases, the specific resistance increases, and the flowing current decreases. So,
When a ceramic heater is used as the heater, if the current flowing through the heater is detected, it can be detected that the temperature of the heater has become high. When such a ceramic heater is in water, the surface temperature of the heater is about 1 in fresh water.
Although it does not rise to over 105 ° C in the case of 00 ° C and seawater,
The temperature rises to several hundred degrees Celsius in the air.
15-20 ° C. higher than the surface temperature). Therefore, if the value of the current flowing through the heater 2 is detected, it is possible to determine whether the heater 2 is in the water or in the air.
It can prevent empty burning. As shown in FIG. 1, the power supply control circuit 3 includes a triac 4, a temperature detecting element 5 including a thermistor, a gate trigger IC 6 of the triac 4, a heater current detecting circuit 7, a heater current setting circuit 8, a current comparing circuit It mainly comprises a circuit 9, a latch circuit 10, a latch reset timer 11, and a current detection delay circuit 12. The gate trigger IC 6 of the triac 4 gives a trigger signal to the gate of the triac 4. The power supply is operated by a (-) power supply, and a zener diode for generating a voltage is provided inside (between the seventh and fifth pins). (-) The power supply is necessary for using the trigger system of the triac 4 in the mode III and the mode IV. The input of the gate trigger IC 6 is a comparator input. When the voltage of (−) IN (3rd pin) is higher than that of (+) IN (4th pin), the triac 4 is triggered and the heater is activated. 2 is energized. That is, the water temperature in the water tank detected by the thermistor 5 is changed to the variable resistance V
Triggers only triac 4 is lower than a predetermined temperature set by R ₂ distributed to the heater 2. The output of the comparator is output to Cout (Pin 2) and the resistance R
_A positive period is set to (+) IN (4th pin) via ₈ , and a hysteresis is provided for the temperature supplied to the heater 2. The current detection delay circuit 12 includes a transistor Q
₁ , Q ₂ , Q ₃ , a Zener diode ZD ₂ , a capacitor C ₆ , and a diode D ₄ . The current detection delay circuit 12 outputs a current after a predetermined time from when the triac 4 is turned on and current starts flowing through the heater 2, for example, 0.5
This is a timer circuit for detecting the heater current after a few seconds. As described above, when the heater current starts to be detected after a predetermined time after the triac 4 is turned on, it is not detected that the current value is equal to or less than the predetermined value immediately after turning on the current, and the current value is equal to or less than the predetermined value. Can be reliably detected. [0014] When the triac 4 is turned off, the transistor Q ₁ is turned on and the transistor Q ₃ is turned on,
The stop output becomes the (+) potential. At this time, the capacitor C ₆ is discharging through the resistor R ₁₄ . Meanwhile, when the triac 4 is changed from OFF to ON, the cut-off of the transistor Q _3, the transistor Q ₁ is cut off. However, since the voltage of the capacitor C ₆ is still low, the transistor Q ₂ is on,
The stop output has a (+) potential. Predetermined time, the higher the charging voltage of the capacitor C ₆ after a lapse of example 0.5 seconds, the transistor Q ₂ is also cut off, the anode voltage of the diode (-) becomes the potential, the diode D ₄ is also cut off to stop output Turns off. The heater current detecting circuit 7 mainly includes a current shunt resistor R ₁ , an operational amplifier IC ₂ , a minus cut diode D ₅ , a smoothing capacitor C ₉ , and a discharge resistor R ₂₁ . When the triac 4 is turned on is triggered, a current starts to flow to the heater 2, the AC current flows through the current shunt resistor R _1, AC voltage proportional to the AC current appears across the current shunt resistor R _1. The voltage obtained by amplifying it is output to the pin 8 of operational amplifier IC _2, the AC voltage (-) cuts the voltage of the diode D _5, and smoothed by capacitor C ₉ only (+) voltage of,
(+) Set to DC voltage. This voltage is proportional to the current flowing through the heater 2. The heater current setting circuit 8 includes a shunt resistor R
₆ and VR _1, (-) Cut diode D _6, a smoothing capacitor C _10, mainly composed of the discharge resistor R _22. Resistor R ₆ and the variable resistor VR ₁ acts as a shunt resistor, the heater 2 is to set the current proportional voltage value at the time of determining that enters the air. The current comparison circuit 9 mainly comprises a comparator IC ₂ and voltage dividing resistors R ₂₆ and R ₂₇ . During energization of the triac 4, if the heater 2 is in the water, greater than the reference voltage towards the heater current proportional voltage that is input to the 12 pin of the comparator IC ₂ is input to the 13 pin of the comparator IC _2, a comparator 14th output of IC ₂ is a (+) output, towards the current proportional voltage input when the heater 2 is drawn from the water to the 12 pin of the comparator IC ₂ becomes low, 14 of the comparator IC ₂
The output number is 0. Incidentally, when the triac 4 is turned off, the current detection stop voltage becomes (+) output, pin 14 output of the comparator IC ₂ is (-) at the output, it becomes divided voltage dividing resistor R _26, R _27, as a result In addition, the abnormal current output becomes the (+) voltage, does not become the (-) voltage, and it is not determined that the current is in the air. That is, when the triac 4 is stopped and the power supply to the heater 2 is stopped, the current comparison circuit 9 itself is also stopped. The latch circuit 10 includes a comparator IC ₂ ,
It is mainly composed of diodes D ₃ and D ₇ . It becomes a voltage (heater 2 in air), since pin 6 input of the comparator IC ₂ is usually 0V, 7 pin output - the output of the current comparator circuit 9 () - the output (). In this state,
Even though the output of the 14th pin of the current comparison circuit 9 returns to the normal (+) voltage, the input of the 5th pin maintains the (-) voltage.
The 7th pin output remains a (-) output (latch circuit). When pin 7 output is (-) output, diode D ₃
, The power supply to the heater 2 is turned off. When the output of the seventh pin becomes the (-) voltage, the latch reset timer 11 is started. When the latch reset timer 11 times out, the 6th pin input becomes a (-) output, and if the abnormal current input is normal (+), the abnormal latch is released and the 7th pin output returns to the (+) voltage, diode D ₃ is cut off (abnormal return operation in air). The latch reset timer 11 includes a transistor Q ₄ , a comparator IC ₂ , capacitors C ₁₃ and C ₁₅ ,
It is mainly composed of diodes D ₈ and D ₉ . Latch input (base potential of the transistor Q ₄₎ is (-) becomes the output, transistor Q ₄ is set OFF, the capacitor C ₁₃ which has been discharged through resistor R ₃₂ to start charging. When a predetermined time elapses greater than its charge voltage (pin 2 input voltage) resistor R ₃₇ and the divided voltage of the resistor R ₃₈ (3 pin voltage), the first pin output (-) as an output, as a result, the comparator reset output which is input to pin 6 of IC ₂ becomes - output (). When the latch circuit 10 is released by the reset output, the transistor Q ₄
Latch input which is the base potential becomes (+) potential, the capacitor C ₁₃ transistor Q ₄ is turned on will be discharged rapidly, the voltage Pin 2 input from pin 3 input of the comparator IC ₂ is lowered 1 The output of the pin number returns to the (+) potential. Then, the diode D ₉ is returned to the cutoff state. As shown in FIG. 3, the power supply circuit
Assuming that the phase is 0 V, +8.2 V and -8.2 are based on the phase.
V is being created. When the voltage of the R-phase is higher than the S phase, to charge the (+) electric potential to the capacitor C ₁ of the power supply control circuit 3 shown in FIG. 1, when the voltage of the R-phase is lower than S phase, the capacitor C ₂ (-) By charging the potential, a voltage based on the positive and negative S phases is created. As described above, according to the water tank heating apparatus of the present invention, the heater is constituted by the ceramic heater, and the current flowing when the ceramic heater is energized is detected. When the current falls below a predetermined value, the current supply to the heater is stopped, and the current is detected after a predetermined time after the current supply to the heater is started. Therefore, the electric conductivity of a liquid such as fresh water or seawater is detected. Power can be reliably shut off at the surface temperature of the heater without being affected by the temperature. In addition, when detecting water, a detection code other than the power cord is always required regardless of the method used. However, the water tank heating device according to the present invention can detect water only with the power cord of the heater.
Further, since the temperature of the heater is directly detected to prevent empty heating, the power supply can be reliably shut off, and a fire or the like can be prevented. Still further, when the heater current is started to be detected after a predetermined time after the heater is energized, the current value is equal to or less than the predetermined value without detecting that the current value is equal to or less than the predetermined value immediately after the current is supplied. Can be reliably detected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagram showing one embodiment of a water tank heating device according to the present invention. FIG. 2 is a diagram showing the relationship between the temperature and the resistance ratio of a ceramic heater. FIG. 3 is a diagram showing a power supply waveform in the water tank heating device according to the present invention. FIG. 4 is a view showing a conventional water tank heating device. [Description of Signs] 1 ... commercial power supply, 2 ... heater, 3 ... power supply control circuit, 4 ... triac, 5 ... temperature detection element,
6: gate trigger IC, 7: heater current detection circuit, 8: heater current setting circuit, 9: current comparison circuit, 10: latch circuit, 11: latch reset timer, 12 ... Current detection delay circuit

Claims (1)

(57) [Claims] [Claim 1] A heater for heating water in a water tank and a temperature detecting element for detecting a temperature of the water in the water tank are provided, and the water temperature in the water tank detected by the temperature detecting element is provided. In a water tank heating device for supplying power to the heater from a commercial power supply when the temperature is equal to or lower than a predetermined temperature, and stopping the power supply to the heater when the water temperature detected by the temperature detecting element is equal to or higher than the predetermined temperature. A ceramic heater is provided, and a current flowing when the ceramic heater is energized is detected. When the current becomes a predetermined value or less, energization of the heater is stopped , and energization of the heater is started. After a predetermined time
A heating device for an aquarium , wherein the current is detected .