JPH0212457Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a combustion flame detection device that detects a combustion flame and sends out an output for warning and an output for stopping combustion when there is an abnormality in the flame.

[Technical background of the invention] Conventionally, this type of combustion flame detection device
The one shown in the figure is known. A flame rod 2 is provided in the flame passage section from the combustion section 1, and one end of an AC power source 3 is connected to the flame rod 2. Then, the flame generation port of the combustion section 1 is connected to a resistor 4,
5 in series, diode 6 in the forward direction,
Furthermore, the AC power supply 3 is connected via resistors 7 and 8 in series.
It is connected to the other end to form a flame current energizing circuit. A capacitor 9 is connected in parallel to the series circuit of the resistors 4 and 5 via the diode 6, and a capacitor 10 is further connected in parallel via the resistor 7.

In addition, a resistive voltage divider circuit 13 formed by connecting resistors 11 and 12 in series is connected to the +V _c DC power supply, and the connection point of the resistors 11 and 12 of the voltage divider circuit 13 is connected to the first
It is connected to one input terminal (-) of second and third open collector type comparators 14, 15, and 16, respectively. In addition, a series time constant circuit 19 consisting of a resistor 17 and a capacitor 18 is connected to the +V _c DC power supply, and a series time constant circuit 19 is connected to the capacitor 18 via a resistor 20.
NPN type transistors 21 are connected in parallel. A resistor 22 is connected between the base and emitter of the transistor 21, and an ignition signal S is input to the base of the transistor 21 from an input terminal I through a resistor 23. This ignition signal S is a signal that is at a high level before the ignition operation is started, and becomes a low level after the ignition operation is started.

The first comparator 14 constitutes a first flame current detection circuit, and its other input terminal (+) is connected to the connection point between the resistor 5 and the diode 6. The second comparator 15 constitutes a second flame current detection circuit, and its other input terminal (+) is connected to the connection point between the resistors 4 and 5. The end of the resistor 4 on the combustion part connection side is +
_Vc is connected to the positive terminal of the DC power supply.
The third comparator 16 has its other input terminal (+) connected to the connection point between the resistor 17 and the capacitor 18 of the time constant circuit 19, and its output terminal is connected through diodes 24 and 25 in opposite directions. is connected to the output terminals of the first and second comparators, and together with the time constant circuit 19, diodes 24 and 25, and the transistor 21, forms an output prohibition control circuit. The output terminal of the first comparator 14 is also connected to the +V _c terminal via a resistor 26 and to the output terminal O ₁ for delivering the combustion stop output. The output terminal of the second comparator 15 is also connected to the +V _c terminal via a resistor 27 and to an output terminal O ₂ for sending out an alarm output.

In this conventional device, the ignition signal S is at a high level before the start of the ignition operation, so the transistor 21 is turned on, and the output of the third comparator 16 is at a low level, and the first and second
The outputs of comparators 14 and 15 are forcibly set to low level. In this state, the ignition operation is started, and when the ignition signal S is inverted to low level, the transistor 21 is turned off and charging of the capacitor 18 via the resistor 17 is started. Then, after a certain period of time has passed, the charge level of the capacitor 18 changes to the resistance 1.
1 and 12, the output of the third comparator 16 is inverted and the forced low level state of the outputs of the first and second comparators 14 and 15 is released, and thereafter the output terminals O ₁ and O ₂ If there is an abnormality in the flame current, high-level combustion stop output and alarm output will be sent. In this case, the first
The flame current level when the second comparator 14 sends out the combustion stop output is set to be smaller than the flame current level when the second comparator 15 sends out the warning output.

[Problems with the background art] As described above, in the conventional device, after the ignition operation starts, the state of the flame current is detected, and if there is an abnormality, the output for stopping combustion and the output for alarm are sent out. Since the fixed time is the same for both, it is difficult to set the fixed time.For example, if you set it relatively short, combustion can be stopped immediately when an abnormality occurs in the flame current, which can prevent the generation of unburned gas from the burner. However, since the setting time is short, the flame is detected when the flame is still unstable, and the second comparator 15, which operates in reverse when the flame current level is relatively high, There was a problem that the alarm output was easily sent out.

On the other hand, if you set it relatively long, the flame will be detected after the flame has stabilized, and the alarm output will not be sent out easily, but if an abnormality occurs in the flame current, it will be detected and the flame will burn. It took a long time to shut down the burner, and the amount of unburned gas generated from the burner increased, creating a risk of explosion and ignition when the burner was relit.

[Purpose of the invention] This invention was devised to solve this problem, and when detecting an abnormality in the combustion flame and stopping the combustion, it is possible to stop the combustion within a relatively short period of time after the ignition operation starts. This allows the generation of unburned gas to be minimized, and the detection of combustion flame to determine whether to issue an alarm can be done only after the combustion flame has stabilized, thus preventing alarm outputs from being sent out inadvertently. The purpose of this invention is to provide a combustion flame detection device that can detect combustion flames.

[Summary of the invention] This invention detects the combustion flame in the combustion part,
The flame current flowing through the flame current energizing circuit, which flows a flame current whose current amount changes depending on the state of the combustion flame, is detected, and when the flame current level falls below a preset first specified level, a combustion stop output is output. At the same time, an alarm output is generated when the temperature drops below a second specified level which is higher than a preset first specified level, and an alarm output is generated for a preset period T in response to the ignition operation of the combustion section _1. The generation of the combustion stop output is prohibited, and the generation of the alarm output is prohibited for a certain period of time T ₂ that is longer than a preset period of time T ₁ .

[Embodiments of the invention] Hereinafter, embodiments of this invention will be described with reference to the drawings.

As shown in FIG. 1, a flame rod 52 is provided in the flame passage section from the combustion section 51, and one end of an AC power source 53 is connected to the flame rod 52.
Then, the flame generation port of the combustion section 51 is connected to a resistor 54,
55 in series, a diode 56 in the forward direction, and resistors 57 and 58 in series to form a flame current energizing circuit. Note that a capacitor 5 is connected to the series circuit of the resistors 54 and 55 via the diode 56.
9 are connected in parallel, and the resistor 5 is further connected in parallel.
A capacitor 60 is connected in parallel via 7.

In addition, a resistive voltage divider circuit 63 formed by connecting resistors 61 and 62 in series is connected to the +V _c DC power supply, and the connection point between the resistors 61 and 62 of the voltage divider circuit 63 is connected to the first and second open collector type. It is connected to one input terminal (-) of the second, third, and fourth comparators 64, 65, 66, and 67, respectively. In addition, a first series time constant circuit 69 consisting of a resistor 67 and a capacitor 68 is connected to the +V _c DC power supply, and a resistor 70
and a second series time constant circuit 72 with a capacitor 71
An NPN transistor 74 is connected in parallel to the capacitor 68 through a resistor 73, and an NPN transistor 76 is connected in parallel to the capacitor 71 through a resistor 75. A resistor 77 is connected between the base and emitter of the transistor 74, and an ignition signal S is input to the base of the transistor 74 from an input terminal I through a resistor 78. The transistor 76
A resistor 79 is connected between the base and emitter of
An ignition signal S is input to the base from an input terminal I through a resistor 80. The ignition signal S is a signal that is at a high level before the ignition operation is started, and becomes a low level after the ignition operation is started.

The first comparator 64 constitutes a first flame current detection circuit, and its other input terminal (+) is connected to the connection point between the resistor 55 and the diode 56. the second comparator 65
constitutes a second flame current detection circuit, and the other input terminal (+) is connected to the connection point between the resistors 54 and 55. The combustion section connection side end of the resistor 54 is connected to the positive terminal of a +V _c DC power source. The output terminal of the first comparator 64 is connected to the +V _c terminal via the resistor 81, and an output terminal O ₁ is used to send out the combustion stop output.
is connected to. An output terminal for connecting the output terminal of the second comparator 65 to the +V _c terminal via the resistor 82 and for sending an alarm output.
Connected to _O2 .

The third comparator 66 connects the other input terminal (+) to the resistor 6 of the first time constant circuit 69.
7 and the capacitor 68, and its output terminal is connected to the output terminal of the first comparator 64 via a diode 83 in the opposite direction. The third comparator 66, the first
A circuit including the time constant circuit 69, the diode 83, the transistor 74, etc. forms a first output prohibition control circuit. The fourth comparator 67 connects the other input terminal (+) to the second
It is connected to the connection point between the resistor 70 and the capacitor 71 of the time constant circuit 72, and its output terminal is connected to the output terminal of the second comparator 65 via a diode 84 in the opposite direction. Said fourth
A circuit including the comparator 67, the second time constant circuit 72, the diode 84, the transistor 76, etc. forms a second output prohibition control circuit. The charging time constant for the capacitor 68 in the first time constant circuit 69 is set smaller than the charging time constant for the capacitor 71 in the second time constant circuit 72.

In the apparatus according to the present invention having such a configuration, the ignition signal S is at a high level before starting the ignition operation. Therefore, transistors 74, 76
Both are on, and charging of the capacitors 68 and 71 of each time constant circuit 69 and 72 is prohibited. In this state, the third and fourth comparators 6
The outputs of the comparators 6 and 67 are both at a low level, and the outputs of the first and second comparators 64 and 65 are forcibly set to a low level. That is,
The first comparator 64 is prohibited from sending out a high-level combustion stop output, and the second comparator 65 is prohibited from sending a high-level warning output.

In this state, the ignition operation is started, and when the low level ignition signal S is input, the transistors 74 and 76
turns off. Therefore, the first and second time constant circuits 69 and 72 start operating, and the capacitors 68 and 7
Charging to 1 is started. On the other hand, in the combustion section 51, ignition is performed by an ignition operation. Then, ignition takes place and the combustion flame reaches the flame rod 52.
When the flame rod 52 and the flame generating port of the combustion section 51 come into contact through the combustion flame, the AC power source 53→flame rod 52→
A flame current begins to flow in the closed loop of the flame outlet of the combustion section 51 → the resistors 54 and 55 → the diodes 56 → the resistors 57 and 58 → the AC power source 53.

Then, after a predetermined period of time _T1 has elapsed, the charging voltage of the capacitor 68 of the first time constant circuit 69 reaches the voltage divided by the resistors 61 and 62, and the output of the third comparator 66 is inverted to high level. I come to do it. As a result, the state in which the output of the first comparator 64 is forcibly set to a low level is released. Thereafter, when the input level to its input terminal (+) reaches the input level to its input terminal (-), the first comparator 64 inverts its output to a high level and outputs the signal through the output terminal _O1. Sends output for combustion stop. Furthermore, after a predetermined time period _T2 longer than the certain time period _T1 has elapsed, when the charging voltage of the capacitor 71 of the second time constant circuit 72 reaches the voltage divided by the resistors 61 and 62, the fourth comparator The output of 67 is inverted to high level. As a result, the state in which the output of the second comparator 65 is forcibly set to a low level is released. Thereafter, when the input level to its input terminal (+) reaches the input level to its input terminal (-), the second comparator 65 inverts its output to a high level and outputs the signal through the output terminal _O2. Sends alarm output.
Here, the conditions for the first comparator 64 to send out the combustion stop output are as follows: the resistance value of the resistor 61 is R ₁ , the resistance value of the resistor 62 is R ₂ , the resistance value of the resistor 54 is R ₃ ,
Assuming that the resistance value of the resistor 55 is R ₄ and the flame current is I ₀ , R ₁ · V _c / R ₁ + R ₂ > I ₀ (R ₃ + R ₄ )... In other words, R ₁ · V _c / (R ₁ + R ₂ ) (R ₃ + R ₄ ) > I ₀ ......

Furthermore, the condition for the second comparator 65 to send out the alarm output is R ₁ ·V _c /R ₁ +R ₂ >I ₀ ·R ₃ ... In other words, R ₁ ·V _c /(R ₁ +R ₂ ) · R ₃ > I ₀ .... Now, R ₁ · V _c / (R ₁ + R ₂ ) (R ₃ + R ₄ ) =
Assuming that I ₁ , R ₁ · V _c / (R ₁ + R ₂ ) · R ₃ = I ₂ , if the flame current I ₀ is flowing not only I ₁ but also I ₂ or more, the first and second comparators 64 , 65 are both input terminals (-)
Since the input level to the input terminal (+) is higher than the input level to the input terminal (+), both outputs are at a low level. In other words, it is determined that the flame current is flowing normally. However, when the flame current _I0 is _I2 > _I0 > _I1 , the input level to the input terminal (+) of the second comparator 65 is higher than the input level to its input terminal (-). The output of the comparator 65 becomes high level and an alarm output is sent out via the output terminal _O2 . Therefore, at this time, the alarm informs the user that the flame current is decreasing. Furthermore, when the flame current I ₀ is I ₀ <I ₁ , the input level to the input terminal (+) of the first comparator 64 is also higher than the input level to its input terminal (-). The output becomes high level, and the combustion stop output is sent out through the output terminal _O1 . Therefore, at this time, it is determined that there is an abnormality in the combustion section, and the combustion operation is stopped.
In other words, the fire is extinguished.

In this way, when an abnormal condition occurs where almost no flame current flows, after the ignition operation starts,
The output for stopping combustion is sent out in a relatively short period of time _T1 , and the fire is extinguished before much unburned gas accumulates in the combustion section 51, so there is no risk of explosive ignition in the event of re-ignition. . Furthermore, regarding the sending of alarm outputs that occur when the flame current becomes slightly unstable, a decision is not made until a relatively long time _T2 has elapsed after the start of the ignition operation, so the flame current remains normal during that time. If so, it will be stable enough. Therefore, there is no possibility that an inconvenience such as the alarm output being easily sent out at the time of ignition occurs, and it is possible to reliably send out the alarm output only when the flame current is in an abnormal state.

[Effects of the invention] As detailed above, according to this invention, when an abnormality in the combustion flame is detected and the combustion is stopped, it can be done in a relatively short period of time after the ignition operation has started. A combustion flame detection device that can reduce the generation of combustion gas as much as possible, and that can detect combustion flames only after the combustion flames have stabilized to determine whether to issue an alarm, and prevents the issuance of alarm outputs. It is something that can be provided.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an embodiment of this invention, Figure 2 is a circuit diagram showing an embodiment of this invention.
The figure is a circuit diagram showing a conventional example. 51... Combustion part, 52... Flame rod, 5
3... AC power supply, 54, 55, 57, 58... Resistor, 63... Resistance voltage divider circuit, 64... First comparator, 65... Second comparator, 66...
...Third comparator, 67...Fourth comparator, 69...First time constant circuit, 72...Second
time constant circuit, 74, 76... NPN type transistor, 83, 84... diode.

Claims (1)

[Scope of utility model registration request] There is a flame current energization circuit that detects the combustion flame in the combustion section and sends a flame current whose amount changes depending on the state of the combustion flame, and a flame current that flows through this flame current energization circuit and detects the flame current level. a first flame current detection circuit that generates an output for combustion termination when the voltage drops below a preset first specified level; a second flame current detection circuit that generates an alarm output when the current falls below a second specified level that is higher than the first specified level; and a preset period of time in response to the ignition operation of the combustion section.
T ₁ , a first output prohibition control circuit that prohibits the generation of the combustion stop output from the first flame current detection circuit; and the certain period of time T ₁ that is preset in response to the ignition operation of the combustion section. a constant time T ₂ longer than
A combustion flame detection device comprising: a second output prohibition control circuit that prohibits generation of an alarm output from the second flame current detection circuit.