JPH0448529Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a humidity detection device that controls the energization of a heating wire in order to evaporate and scatter adhesive substances adhering to the surface of a humidity detection element. .

Conventional configurations and their problems Recently, elements whose electrical resistance and capacitance change depending on relative humidity have been increasingly used to measure and control humidity. If large amounts of sticky substances such as oil or tar adhere to the surface of such elements,
Air permeability to the element may be lost, making it impossible to detect humidity. Therefore, a heating wire is installed around the element, and electricity is applied for a short time at an appropriate time to vaporize the sticky substance attached to the element (hereinafter referred to as "cleaning"), thereby regenerating the element. There are many examples of this being implemented.

FIG. 1 is a perspective view of a conventional humidity detector, in which a heating wire 2 is connected around a humidity detection element 1.
and cover each lead wire 1a, 1b, 2a,
2b is configured to pass through the insulating holder 3 and be electrically connected to the measurement control circuit.

The uses of such humidity detectors have increased as their performance has improved, and they are increasingly being used as humidity detectors in electronically controlled air conditioning control systems. In such applications, it is desirable that power consumption be low in order to downsize the measurement control section. Humidity detection elements themselves often have high impedance, so their power consumption is small, but heating wires generally consume several to tens of times as much power as the element, albeit for a short period of time. be.

FIG. 2 is a circuit diagram of a conventional example of a humidity signal output circuit using the above-mentioned humidity detector. When commercial AC power is applied to terminals 4a and 4b, it is transformed by a transformer 5 and then converted to DC by a rectifier 6. A three-terminal voltage regulator 7 stabilizes the DC voltage and supplies power to subsequent circuits. The resistor 9 is connected in series with the humidity detection element 1, inputs the potential at the midpoint between the two to the amplifier 10, and outputs the humidity signal to the output terminal 10.
It is configured to be taken out from a.

The timer circuit 11 de-energizes the relay coil 12a at regular time intervals and energizes the heating wire 2 connected in series with the relay contact 12b. Since power is supplied to the heating wire 2 through the three-terminal voltage regulator 7, rectifier 6, and transformer 5, the ratings of these circuit components must have a capacity commensurate with the power consumption of the heating wire.

For this reason, compared to the original purpose of outputting a humidity signal, a large-capacity circuit component is required for the auxiliary means of cleaning the element, which is disadvantageous in terms of size, weight, and power loss.

Purpose of the invention The purpose of the invention is to reduce the capacity of circuit components in the circuit that supplies power to the heating wire that cleans the humidity detection element, thereby reducing the size, weight, and cost of the device. be.

Structure of the invention In this invention, in parallel with the humidity signal output circuit, the common terminal of the relay driven by the power supply circuit is used as a capacitor, the normally open side terminal is used as a resistor, and the normally closed side terminal is used for cleaning the humidity detection element. A humidity detection device is constructed by having circuits connected to the respective heating wires. When the relay is not energized, the capacitor is discharged to generate heat in the heating wire, thereby simplifying the power supply circuit required for cleaning.

DESCRIPTION OF EMBODIMENTS FIG. 3 is a circuit diagram showing an embodiment of the present invention. When commercial AC power is applied to the terminals 4a and 4b, it is transformed by a transformer 50 and then converted to DC by a rectifier 60. A three-terminal voltage regulator 70 stabilizes the DC voltage and supplies power to subsequent circuits. The resistor 9 is connected in series with the humidity detection element 1, and a timer circuit 11 that inputs the midpoint potential between the two to the amplifier 10 and takes out the humidity signal output from the output terminal 10a turns off the relay coil 12a at regular time intervals. Excite. A capacitor 13 is connected to the common terminal c of the relay contact 12b, a heating wire 2 is connected to the normally closed contact terminal d, and a resistor 14 is connected to the normally open contact terminal e.

In the above embodiment, when the relay contact 12b is closed to the normally open side, the series circuit of the capacitor 13 and the resistor 14 is connected to the three-terminal voltage regulator 7.
Upon receiving a DC voltage from 0, a charging current flows, and an amount of electricity is stored in the capacitor 13 according to its capacitance. Then, when the relay contact 12b is closed to the normally closed side by the timer circuit 11, the capacitor 13 and the heating wire 2 form a circular circuit, and the amount of electricity stored in the capacitor 13 is discharged through the heating wire 2. The humidity detecting element 1 is cleaned by the Joule heat generated at this time.

Note that if the commercial power supply is to be cut off once a day (in the evening, etc.), the timer circuit 11 may be omitted.In other words, if the relay coil 12a is connected to the DC voltage circuit, the power supply will be cut off once a day (in the evening, etc.). When the common terminal c of the relay is connected to the normally closed terminal e, the capacitor 13
The electric charge is discharged to the heating wire 2, and the heating wire 2 is automatically cleaned.

Effects of the Invention As described above, the present invention includes a humidity detection element having a heating wire for cleaning, a relay, and a circuit for supplying electrodes to the relay and the humidity detection element, and a common terminal of the relay is connected to the humidity detection element. Connect the capacitor, the normally open terminal to the resistor, and the normally closed terminal to the heating wire, charge the capacitor with a small current during the long period of humidity measurement, and then charge the capacitor with a small current during the relay's non-energized time. By discharging the capacitor with a large current to perform cleaning, the capacity of the power supply circuit components can be made smaller than in the past, and the size, weight, and cost of the device can be reduced. Note that the capacitor also functions to smooth the DC voltage during humidity measurement.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional humidity detector.
FIG. 2 is a circuit configuration diagram of a conventional example, and FIG. 3 is a circuit configuration diagram of an embodiment according to the present invention. 1... Humidity detection element, 2... Heating wire, 11...
Timer circuit, 12a... Relay coil, 12b...
...Relay contact, 13...Capacitor, 14...Resistor.

Claims (1)

[Scope of utility model registration request] It has a humidity detection element having a heating wire for cleaning, a relay, and a circuit for supplying power to the relay and the humidity detection element, the common terminal of the relay is a capacitor, the normally open side terminal is a resistor, A humidity detection device in which the normally closed side terminals are each connected to a heating wire, and the common terminal is connected to the normally closed side terminal to discharge the capacitor when the relay is de-energized.