JPS60177228A - Detector circuit for incomplete combustion - Google Patents

Abstract

PURPOSE:To detect incomplete combustion securely by connecting load resistances including at least one variable resistance in series with respective plural photodetecting elements which photodetect light from combustion flames, and deciding on output of the photodetecting elements by comparison. CONSTITUTION:When an incomplete combustion state is entered, the photodetection wavelength of a color sensor becomes long, so an input voltage V2 to the 1st comparator 11 becomes higher than an input voltage V1 and the output of the 1st comparator 11 goes up to a level ''High'' to charge a capacitor C3 through resistances R3 and R4. Then, an input voltage V4 applied to the minus terminal of the 2nd comparator 12 increases on exponential function basis according to the time constant determined by resistances R3 and R4 and the capacitor C3 and then exceeds a reference voltage V3 applied to the plus input terminal a specific time later. Then, the output of the 2nd comparator 12 goes down to a level ''Low'' and a light emitting diode 13 turns on to warn the incomplete combustion state securely.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an incomplete combustion detection circuit that detects incomplete combustion in a combustion appliance such as a kerosene stove.

<Prior art> When a combustion appliance is burned in a highly airtight room, the oxygen concentration decreases over time, and if oxygen becomes insufficient, the combustor will undergo incomplete combustion and the oxygen will wander. During this process, non-flammable gases and carbon monoxide increase, creating a dangerous atmosphere that is physiologically harmful and can even lead to death.

For this reason, a device (Japanese Patent Application No. 73868/1983) has been proposed to prevent such accidents by using a color sensor as described below that detects the oxygen concentration in the air from the combustion flame.

FIG. 1(a) shows the structure and equivalent circuit of the color sensor.

It is shown in FIG. 1(b). A photodiode (light receiving element) PDI formed by a PN junction between two layers 1 and an N layer 2 has high short wavelength sensitivity, and a photodiode PD2 formed by a PN junction between two layers 3 and N layer 2 has a high sensitivity at long wavelengths. Note that 4 is an insulating film, 5 is an electrode provided on the second layer 1, 6 is an electrode provided on the N layer 2, and 7 is an electrode provided on the second layer 3. The short-circuit current ratio L/I of both photodiodes PCI and 'PD2 and the light reception wavelength λ have a 1:1 correspondence relationship as shown in FIG.

If the short circuit current ratio of PD2 is known, it should be possible to identify the received wavelength λ, that is, the color of the combustion flame.

Therefore, based on this short circuit current ratio, 1. As an incomplete combustion detection circuit that detects incomplete combustion by identifying the color of combustion flame,
There is something like the one shown in Figure 3. In this circuit, the short circuit current I II obtained from the two photodiodes PDI and PD2 that constitute the color sensor is
The voltage V is converted to 11V by the load resistors R, , R2 connected in series with I and PD2. This voltage V,,V2
are input to the 0 input terminal and ○ input terminal of the comparator 8, respectively.

The output signal of this comparator 8 becomes a "Low" level when the received light wavelength λ is a long wavelength, that is, when there is incomplete combustion, and the output signal is used to operate the light emitting diode 9 to issue an alarm or to activate the control section (not shown). This prevents oxygen deficiency accidents by starting the operation and stopping combustion.

By the way, in combustion appliances such as kerosene stoves and fan heaters, the outer flame tube temporarily turns black immediately after ignition or immediately after lowering the wick, and temporarily emits light with a long wavelength. That is, as shown in FIG. 4, the output ratio (■2/■1) of the color sensor becomes temporarily large immediately after ignition or immediately after the lamp wick is lowered.

However, in the conventional incomplete combustion detection circuit described above, incomplete combustion is simply detected from the relative value between the outputs of the light receiving elements PDI and PD2. , that is, the light receiving elements PDI, PD
When the wavelength of the light received by 2 temporarily becomes a long wavelength, the output of comparator 8 becomes "Low" level, causing light emitting diode 1'9 to operate even though it is not necessary to issue an alarm. , and has the drawback of operating the control unit.

In other words, in the conventional incomplete combustion detection circuit described above, a state such as immediately after ignition when the received light wavelength is long, which is apparently the same as an oxygen-deficient state, is mistakenly recognized as a true oxygen-deficient state, causing a malfunction. There is a drawback.

<Purpose of the Invention> Therefore, the purpose of the present invention is to prevent the above-mentioned malfunction, in which the apparent oxygen-deficient state immediately after ignition or immediately after lowering the wick is mistaken as an actual oxygen-deficient state. The aim is to accurately detect incomplete combustion without causing any damage.

<Structure of the Invention> In order to achieve the above object, the incomplete combustion detection circuit of the present invention is based on the inventor's discovery, that is, in an actual oxygen-deficient state, the color sensor receives light with a long wavelength. On the other hand, based on the fact that the state in which the color sensor receives long-wavelength light does not last for more than a certain period of time in the apparent oxygen-deficient state, multiple light-receiving elements of the color sensor A load resistor is connected in series to each of the load resistors, at least one of these load resistors is a variable resistor, a comparator is provided for comparing the outputs of the light receiving elements, and the output terminal of the comparator and the discriminating means are connected. The present invention is characterized in that a delay circuit is connected between the terminals to accurately detect incomplete combustion based on the output of the discriminating means 6.Embodiments The present invention will be described in detail below with reference to illustrated embodiments. do.

In FIG. 5, PDI is a photodiode that receives light from the combustion flame and has high short wavelength sensitivity, and PD2 is a photodiode that receives light from the combustion flame and has high long wavelength sensitivity. PDI and PD2 constitute a color sensor that identifies the color of combustion flame.

Further, R1 is a fixed resistor, R2 is a variable resistor, C3°C2 is a smoothing capacitor, 11 is a first comparator, and the short circuit current I of the photodiodes PDI and PD2 is
I2 is converted into voltages v, , v2 by resistors R, , R2, and these voltages v, , v2 are input to the e input terminal and the - input terminal of the first comparator 11, respectively. When the combustion appliance is in an incomplete combustion state, the resistance value of the variable resistor R2 is determined by the voltage V,
, V2 so that the voltage ratio (V2/V,) becomes 1. That is, for example, as shown in Fig. 6, when the oxygen concentration in the room housing the combustion appliance reaches approximately 18%,
The voltage ratio (V2/V,) is set to 1. The variable resistor R2 can also be used to correct variations in the characteristics of the color sensor.

Further, 12 is a second comparator as a discrimination means, C3 is a capacitor, R3 is a fixed resistor, and R4 is a fixed resistor whose resistance value is smaller than that of the fixed resistor R1. A delay circuit is configured to be connected between the output terminal of the first comparator 11 and the Q input terminal of the second comparator 12.

In addition, R,,R,: is a voltage dividing resistor for inputting the reference voltage V to the input terminal of the second comparator 12, 13 is a light emitting diode connected to the output terminal of the second comparator 12, and R8 is a It is a fixed resistance. Note that Vcc is a constant voltage source.

In the incomplete combustion detection circuit having the above configuration, it is assumed that the color sensor is currently in a normal combustion state where the wavelength of light received is short, and the input voltage V1 of the first comparator 11 is greater than the input voltage V2. Then, the output of the first comparator 11 becomes “Low”.
” level, and the output of the second comparator 12 is “High”.
level, and the light emitting diode 12 remains off.

Next, incomplete combustion! ! (oxygen deficient state), the wavelength of light received by the color sensor becomes long, so the input voltage (2) of the first comparator 11 becomes larger than the input voltage (1), and the first comparator 11 The output becomes “High” level,
The capacitor C1 is charged through the resistors R,,R,. Then, the input voltage v4 applied to the ○input terminal of the second comparator 12 is
It increases exponentially with a time constant determined by 2, and exceeds the reference voltage V3 applied to the input terminal after a certain leap (for example, several minutes). Then, the output of the second yG comparator 12 becomes "Low" level, and the light emitting diode 1
3 lights up to reliably warn that incomplete combustion is occurring. Further, although not shown, a warning is issued by a buzzer or the like, and the control section is activated to stop combustion, thereby preventing an oxygen deficiency accident.

Next, if it looks like it's just after the ignition or just after lowering the wick, it's a sign of oxygen deficiency 1! (See Figure 4).

Then, the input voltage V2 of the first comparator 11 to the human power terminal
is temporarily higher than the input voltage v1 of the e input terminal, the output of the first comparator 11 becomes "High" level, the capacitor C2 is charged through the resistor R3°R7, and the second comparator 12 is charged accordingly. The input voltage (4) of the e input terminal increases. However, in the apparent oxygen-deficient state, the state in which the color sensor receives light with a long wavelength, that is, the state in which the input voltage v2 of the first comparator 11 is greater than the input voltage ■1, remains for a short time (for example, Since the voltage does not last for more than a few minutes, the output of the first comparator 11 reaches the "Lou+" level before the input voltage V of the second comparator 12 exceeds the reference voltage V3.Therefore, the capacitor C7 is charged. The charge is discharged through the resistor R4 and the input voltage V of the second comparator 12
4 decreases. Therefore, in such an apparent oxygen-deficient state, the output of the second comparator 12 will not go to the "Low" level, the light emitting diode 13 will not light up, and the detection of incomplete combustion will not be possible. Malfunctions can be prevented.

Note that the time constant when discharging capacitor C3 is, since the resistance value of resistor R1 is much smaller than that of resistor R1,
This is very small compared to the time constant during charging. Note that these time constants are appropriately set depending on the conditions of the combustion appliance and the like.

In the above embodiment, the second comparator was used as the discrimination means, but
Instead of this, various types such as a constant voltage diode can be used.

<Effects of the Invention> As is clear from the above explanation, the incomplete combustion detection circuit of the present invention is configured as described above, so that the apparent oxygen deficiency state is mistakenly recognized as an actual oxygen deficiency state. Incomplete firing can be reliably detected without any problems.

Further, since the incomplete combustion detection circuit of the present invention is constituted by a color sensor, a comparator, a delay circuit, and a determining means, it can be driven by a battery, and therefore can detect incomplete combustion in a vortaple kerosene stove or the like.

[Brief explanation of drawings]

Figure 1 (,) is a structural diagram of the color sensor, Figure 1 (b) is an equivalent circuit of the above structural diagram, Figure 2 is a characteristic diagram showing the wavelength-/short-circuit current ratio of the color sensor, and Figure 3 is the conventional Figure 4 is a circuit diagram of the incomplete combustion detection circuit of the present invention, and Figure 4 shows the time-output ratio characteristics when the ignition is raised and the wick is lowered. - Circuit diagram of the embodiment, FIG. 6 is a characteristic diagram showing the output ratio characteristics of the color sensor with respect to oxygen concentration. PDI, PD2...photodiode, 11...first
Comparator, 12...Second comparator, C,, C2, C0...
・Capacitor, 13... Light emitting diode. Patent applicant Sharp Co., Ltd. Representative Patent attorney Aohaku Aohaha 2 people Figure 1 (0)
Figure 1 (b) Figure 2 (mml)

Claims (1)

[Claims] (1) In a circuit that detects incomplete combustion from the relative value between the outputs of each light receiving element of a color sensor consisting of a plurality of light receiving elements having different wavelength sensitivities that receive light from a combustion flame, A load resistor is connected in series to each of the light receiving elements, at least one of these load resistors is a variable resistor, a comparator is provided for comparing the output of the light receiving element, and the output terminal is distinguished from the output terminal of the comparator. An incomplete combustion detection circuit characterized in that a delay circuit is connected to the determining means to detect incomplete combustion based on the output of the determining means.