JPS625550Y2 - - Google Patents

Description

[Detailed description of the invention] When using a spark plug to ignite a burner, it is necessary to automatically turn off the spark plug when the burner starts to burn, so conventionally a photoelectric conversion element receives the light from the burner flame. However, there are devices that use this to detect whether or not the burner is ignited.

However, in this case, the photoelectric conversion element may malfunction due to external light, and the ignition plug may be turned off even though the burner has not yet completely burned, resulting in failure to ignite the burner.

The present invention aims to eliminate this drawback.

To explain the embodiment of the present invention shown in the drawings, R is a photoconductive element such as Cds, one end of which is connected to a constant voltage source, the other end of which is connected to the negative input side of differential amplifier A1, and resistor r1. Ground through.

A delay circuit consisting of a capacitor C and a resistor r2 is connected in parallel to the resistor r1 via a forward diode D, and the plus side of the capacitor C is connected to the plus input side of the differential amplifier A1. Here resistance r
1 and r2 are equal.

Next, the output side of differential amplifier A1 is connected to differential amplifier A2.
A resistor R3 connected to a constant voltage source is connected to the positive input side of the resistor R3.

B is a control unit that operates the power switch of the spark plug, and is connected to the output side of the amplifier A2.

Then, a power switch for a spark plug (not shown) is turned on, and the plug is discharged to perform ignition work.

When the spark from the plug ignites the burner and the burner begins to burn, the photoconductive element R receives the light from the flame and its conductivity increases. As a result, the terminal voltage Er of the resistor r1 increases, and the capacitor C is charged via the diode D.

The terminal voltage Ec of the capacitor C reaches a steady value after, for example, 2 to 3 seconds according to the time constant of the delay circuit.

When the burner ignites normally and the luminous intensity of the flame gradually increases, the voltage Er also increases in proportion to this, so
Voltage Er becomes larger than voltage Ec, and amplifier A1
outputs a voltage proportional to the difference between voltages Er and Ec.

When the output voltage of the amplifier A1 exceeds the terminal voltage of the resistor r3, that is, a certain voltage level, the amplifier A2 outputs an output and the control section B turns off the power switch of the spark plug.

By the way, when external light such as lighting or sunlight irradiates the photoconductive element R, the luminous intensity of the external light does not change over time, so as long as the burner does not burn, the conductivity of the photoconductive element R is constant and the voltage Er is also constant. Does not change over time. Therefore, since the voltages Er and Ec are equal, the amplifier A1 does not output any output and the spark plug is not turned off.

A photodiode or a phototransistor may be used instead of the photoconductive element R in the embodiment.

In short, in the present invention, the output of a photoelectric conversion element such as the photoconductive element R and the output of a delay circuit connected thereto are compared by a comparator such as a differential amplifier, and the photoelectric conversion element receives light. Since the ignition of the burner is detected by knowing the temporal change in the luminous intensity of the light generated, the luminous intensity remains constant even when the photoelectric conversion element is irradiated with external light, which affects the output difference between the photoelectric conversion element and the delay circuit. Therefore, the ignition of the burner can be accurately detected regardless of the intrusion of external light, uneven quality of the photoelectric conversion elements, dirt, etc.

[Brief explanation of the drawing]

The drawing is a circuit diagram of an embodiment of the present invention, where R is a photoconductive element, D is a diode, C is a capacitor, r1,
r2 and r3 are resistors, A1 and A2 are differential amplifiers, B
indicates the control unit, respectively.

Claims (1)

[Scope of utility model registration request] A photoelectric conversion element that receives light from a burner flame and a delay circuit connected thereto are each connected to a comparator, and a temporal change in the light intensity received by the photoelectric conversion element is detected based on the output value of the comparator. Burner ignition detection device.