JP6036650B2 - Flame monitoring device - Google Patents

Description

  The present invention relates to a flame monitoring device having a flame detector for detecting a flame of a burner with ultraviolet rays.

  As a conventional combustion control device, for example, there is a technique described in Patent Document 1. This technique includes a flame detector that detects a flame by detecting ultraviolet rays emitted from the flame, and a shutter that is provided to detect a self-discharge abnormality of the flame detector. Here, a self-discharge abnormality is detected by monitoring the presence or absence of discharge of the flame detector when ultraviolet rays from the flame are blocked by the shutter.

Further, as a combustion apparatus for preventing a flame detection failure caused by an oxide film adhering to a flame detection frame rod, for example, there is a technique described in Patent Document 2. In this technique, a flame detection electrode and a burner ignition electrode are used together, and the ignition electrode circuit is switched to a flame detection circuit after a predetermined time has elapsed after ignition.
Further, as a flame detection device, there is a technique described in Patent Document 3, for example. This technique includes a shutter drive circuit that operates a shutter that blocks ultraviolet rays emitted from a flame for a predetermined time after the flame is detected by a flame detector.

  Moreover, as another flame detection apparatus, there exists a technique of patent document 4, for example. This technique is designed to ensure the reliability of the optical sensor by stopping the combustion when the optical sensor reaches a high temperature.

Japanese Patent Laid-Open No. 2-97823 JP-A-6-147475 JP 2004-36907 A JP 2009-121713 A

By the way, when the burner is ignited, an electric spark is generated at a position where a flame is formed. The ultraviolet rays emitted by the electric spark are much stronger than the ultraviolet rays emitted by the flame. However, none of the techniques described in the above-mentioned patent documents considers the strong ultraviolet rays generated by the sparks at the time of ignition of the burner. For this reason, the flame detector sensor cannot be protected from the strong ultraviolet rays during burner ignition.
Then, this invention makes it the subject to provide the flame monitoring apparatus which can protect the sensor of a flame detector.

In order to solve the above-described problem, an aspect of the flame monitoring apparatus according to the present invention includes: an ultraviolet sensor that detects the flame by receiving ultraviolet light emitted from a flame of a burner; a position where the flame is formed; and the ultraviolet sensor. And a burner that generates an electric spark in the vicinity of the formation position of the flame and ignites the burner by the electric spark. An abnormality that monitors an abnormality of the ultraviolet sensor, comprising: an ignition unit; and a cutoff control unit that drives and controls the ultraviolet ray blocking unit to block the incidence of ultraviolet rays to the ultraviolet sensor during the operation of the burner ignition unit A monitoring unit; and after the operation of the burner ignition unit is stopped, the abnormality monitoring unit drives and controls the ultraviolet blocking unit to permit the incidence of the ultraviolet rays. It is characterized by starting the abnormality monitoring of the UV sensor when detecting the flame.

Thus, since the incidence of ultraviolet rays to the ultraviolet sensor is interrupted when the burner is ignited, the ultraviolet sensor can be protected from the strong ultraviolet rays generated by the electric sparks when the burner is ignited. Therefore, the lifetime of the ultraviolet sensor for flame detection can be extended.
Further, in the above, a power supply circuit for supplying a drive voltage to the burner ignition unit is provided, and the shutoff control unit determines that the burner ignition unit is in operation when the power supply circuit is in operation. Is preferred.

Thus, it is not necessary to determine whether or not the burner ignition unit is operating by determining whether or not the burner ignition unit is operating on the power source side. Therefore, it is possible to drive and control the ultraviolet blocking unit easily and appropriately .

Further, the prior SL abnormality monitoring unit, after stopping operation of the burner ignition unit, when the ultraviolet blocking portion drives and controls allow incident of the ultraviolet, the ultraviolet sensor of the UV sensor when detecting the flame start the abnormality monitoring.
In this way, the abnormality monitoring function of the ultraviolet sensor can be activated after confirming that the burner is burning. Therefore, it is possible to confirm the presence or absence of a flame by the ultraviolet sensor and the presence or absence of occurrence of an abnormality in the ultraviolet sensor.

Also, in the above, the abnormality monitoring unit drives and controls the ultraviolet blocking portion, when the permission and the blocking of incident UV of the UV sensor was repeated at a predetermined period, the flame detector of the ultraviolet sensor It is preferable to determine whether or not an abnormality has occurred in the ultraviolet sensor by monitoring the presence or absence.

  Thereby, when the ultraviolet ray sensor detects a flame in a state where the ultraviolet ray shielding part is closed and the incidence of ultraviolet rays is blocked, it can be determined that a self-discharge abnormality has occurred in the ultraviolet ray sensor. Further, since the abnormality of the ultraviolet sensor can be monitored by using the ultraviolet shielding part for protecting the ultraviolet sensor, an increase in cost due to the separate installation of the ultraviolet shielding part can be suppressed.

  According to the present invention, the ultraviolet ray sensor can be protected from the strong ultraviolet rays at the time of burner ignition by the ultraviolet ray blocking unit. Therefore, the life of the flame detector including the ultraviolet sensor can be extended.

It is principal part sectional drawing of the burner in this embodiment. It is a block diagram of a flame monitoring apparatus and peripheral devices. It is a time chart which shows operation | movement of this embodiment. It is a figure explaining the voltage and spark current which arise in an ignition plug. It is a time chart which shows the conventional operation | movement.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a main part of a burner to which the flame monitoring apparatus of the present embodiment is applied.
In the figure, reference numeral 1 denotes a burner body of a pilot burner. The burner body 1 has an air supply port 2 to which air is supplied from an air supply device (not shown) and a gas to which gas is supplied from a gas supply device (not shown). A supply port 3 is provided.

  The air and gas supplied to the burner body 1 pass through the double pipes of the burner body 1 and are discharged and mixed from a hole opened in the flame port 5 in the flame holding cylinder 4 to become a combustible gas. Here, the air supply port 2 and the gas supply port 3 are provided outside the furnace, and the flame holding cylinder 4 is provided on the inner surface of the furnace. Therefore, the double pipe of the burner body 1 has a length of about 700 mm depending on the thickness of the furnace. The flame-holding cylinder 4 has an inner diameter of about 20 mm according to the amount of combustion.

An ignition plug 6 is provided in the vicinity of the flame port 5, and a high voltage is supplied to the ignition plug 6 from an ignition transformer (not shown) via a high voltage cord. The high voltage cord is connected to the high voltage cord connection port 7. The spark plug 6 protrudes from the outer surface of the flame-holding cylinder 4 to the inside so as to generate an ignition spark (electric spark) in the combustible gas.
The burner body 1 is provided with a flame detector 10. The flame detector 10 includes an ultraviolet sensor 11 including a light receiving element that detects ultraviolet rays, and a blocking device (ultraviolet blocking unit) 12 that can block input of ultraviolet rays to the ultraviolet sensor 11. Further, the flame detector 10 further includes an amplifier circuit (amplification substrate) 13 and a shut-off device drive coil 14. The amplifier circuit (amplification substrate) 13 supplies a pulse voltage to the ultraviolet sensor 11 and receives an ultraviolet signal output from the ultraviolet sensor 11. The shut-off device drive coil 14 is for driving the shut-off device 12 and controls the operation / non-actuation of the shut-off device 12 in response to a command from a flame monitoring device described later.

The flame detector 10 is provided at the other end of the flame holding cylinder 4 of the burner body 1 in order to detect ultraviolet rays from the flame generated in the air-fuel mixture through the flame port 5. The flame detector 10 receives the ultraviolet rays of both the flame and the ignition spark from this position.
Next, the configuration of the flame monitoring device will be described.
FIG. 2 is a block diagram of the flame monitoring device and peripheral devices.

The flame monitoring device 20 supplies a power supply voltage to the amplification circuit 13 of the flame detector 10. At this time, the amplifier circuit 13 supplies a pulse voltage to the ultraviolet sensor 11, and the ultraviolet sensor 11 outputs an ultraviolet signal indicating whether or not ultraviolet light is received to the amplifier circuit 13 in synchronization with the pulse voltage. To do.
The ultraviolet sensor 11 has a structure in which a cathode and an anode are provided in a glass tube filled with a specific gas, and a pulse voltage supplied from the amplifier circuit 13 is applied between both electrodes. When ultraviolet light is irradiated with this pulse voltage applied, a discharge is generated between both electrodes. The ultraviolet sensor 11 outputs the discharge current generated at this time as an ultraviolet signal.

That is, the ultraviolet sensor 11 outputs an ultraviolet signal synchronized with the pulse voltage to the amplifier circuit 13 when receiving ultraviolet light, and does not give the ultraviolet signal to the amplifier circuit when not receiving ultraviolet light. It has become.
The amplifier circuit 13 converts the ultraviolet signal, which is a pulsed current input from the ultraviolet sensor 11, into a continuous voltage signal, and gives this to the flame monitoring device 20 as a flame signal. Thereby, the flame monitoring apparatus 20 can determine whether the flame detector 10 has detected a flame (whether the burner is burning).

  Further, the flame monitoring device 20 supplies a driving voltage to the interruption device driving coil 14 of the flame detector 10. At this time, the shut-off device 12 is opened and closed by torque power (shaft power) generated by the shut-off device drive coil 14. The state in which the blocking device 12 is deactivated and allows the incidence of ultraviolet rays to the ultraviolet sensor 11 is referred to as an open state, and the state in which the blocking device 12 is activated to block the incidence of ultraviolet rays to the ultraviolet sensor 11 is referred to as a closed state. .

  The flame monitoring device 20 has an abnormality monitoring function for detecting an abnormality in detection of ultraviolet rays by the ultraviolet sensor 11 and a self-discharge phenomenon that discharges even without ultraviolet rays (flame) as an abnormality of the flame detector 10. This abnormality monitoring function is realized by opening and closing the shut-off device 12 at a predetermined cycle during burner combustion. That is, the flame monitoring device 20 does not receive a flame signal from the flame detector 10 when the shut-off device 12 is open during burner combustion, or closes the shut-off device 12 during burner combustion. Sometimes, when a flame signal is received from the flame detector 10, it is determined that an abnormality has occurred in the flame detector 10.

Note that signal exchange between the flame detector 10 and the flame monitoring device 20 is performed via the connector 15.
Further, the flame monitoring device 20 includes a power supply circuit that supplies drive voltages to the air supply device 31 and the gas supply device 32, respectively, and a power supply circuit that supplies alternating drive voltage to the ignition transformer 33. The air supply device 31 and the gas supply device 32 are supplied with driving voltage from the flame monitoring device 20, thereby supplying air and gas to the burner body 1, respectively.

When the drive voltage is supplied from the flame monitoring device 20, the ignition transformer 33 generates a high voltage synchronized with the AC frequency. The high voltage generated by the ignition transformer 33 is supplied to the spark plug 6. At this time, a spark is generated from the tip of the spark plug 6 by the high voltage supplied from the ignition transformer 33 and ignites the combustible mixture generated through the flame port 5.
In the present embodiment, when the ignition transformer 33 is in operation, the flame monitoring device 20 closes the shut-off device 12 (shut-off control unit), and operates the abnormality monitoring function after the ignition transformer 33 stops operating. It shall be in a state (abnormality monitoring unit).

Here, the flame monitoring device 20 determines that the ignition transformer 33 is in operation when the power supply circuit that supplies the drive voltage to the ignition transformer 33 is operating, and while the power supply circuit is operating. The blocking device 12 may be controlled to be closed.
In addition, the flame monitoring device 20 activates the abnormality monitoring function when the flame detector 10 detects a flame when the shut-off device 12 is opened after the ignition transformer 33 is deactivated. The ignition transformer 33 can be configured to be stopped by a timer after a certain time from the start of operation, and the abnormality monitoring function can be set to the operating state by the same timer.

In this way, the shutoff device 12 is kept closed when the burner is ignited, and is driven to open and close at a predetermined cycle during the combustion of the burner.
Hereinafter, the operation of the present embodiment will be specifically described with reference to the time chart of FIG.
First, prior to ignition of the burner, air is supplied into the burner so that the accumulated fuel is not ignited, and the burner and its vicinity are replaced with air. That is, the flame monitoring device 20 supplies a drive voltage to the air supply device 31 at time t1 to open the electromagnetic valve and supply air to the burner body 1.

  Thereafter, in order to burn the burner, the flame monitoring device 20 supplies power to the ignition device (ignition transformer 33), but before that, supplies a drive voltage to the cutoff device drive coil 14 at time t2, 12 is closed. At time t <b> 3, the flame monitoring device 20 supplies power to the ignition device (ignition transformer 33) to generate a spark from the spark plug 6. During the operation of the ignition device, the shut-off device 12 is kept closed.

Next, the flame monitoring device 20 supplies a driving voltage to the gas supply device 32 at time t <b> 4 to open the electromagnetic valve and supply combustion gas to the burner body 1. Thereby, the burner is ignited at time t5 and combustion is started.
Then, the flame monitoring device 20 stops the power supply of the ignition transformer 33 at time t7. Here, it is assumed that the power supply of the ignition transformer 33 is stopped using a timer for a predetermined time. The set time of the timer is determined based on the time required for ignition. For example, if the time required for ignition is about 2 seconds after supplying the combustion gas, a longer timer, for example, 4 seconds is provided to stop the power supply to the ignition transformer 33.

When the power supply to the ignition transformer 33 is stopped and the ignition device is deactivated, the flame monitoring device 20 switches the cutoff device 12 to the open state at time t8.
At this time t8, since the burner is in combustion, when the flame detector 10 is operating normally, the flame detector 10 outputs a flame signal to the flame monitoring device 20. When this flame signal is received at time t8, the flame monitoring device 20 determines that the abnormality monitoring of the flame detector 10 is started (the abnormality monitoring function is activated).

Therefore, the flame monitoring apparatus 20 supplies a drive voltage to the interruption | blocking apparatus drive coil 13 with a predetermined period after the time t9, and opens and closes the interruption | blocking apparatus 12 with a predetermined period. As a result, the flame monitoring device 20 alternately checks the presence / absence of a flame and the presence / absence of an abnormality in the ultraviolet sensor 11.
As described above, in the present embodiment, during the operation of the ignition device, the shut-off device 12 is activated (closed) to prevent the ultraviolet light from entering the ultraviolet sensor 11 of the flame detector 10. Therefore, it is possible to protect the ultraviolet sensor 11 from ultraviolet rays generated by sparks generated at the time of ignition of the burner.

In general, as an ultraviolet sensor for detecting a flame, UV-C band ultraviolet rays near a wavelength of 200 nm that are absorbed by ozone in the upper atmosphere and do not reach the ground surface are detected so as not to malfunction due to sunlight, and longer wavelengths than that. Those that do not detect ultraviolet rays are used.
In addition, since the UV-C band has a high energy level, it is not light emission but mainly light emission at the time of transition from the electronically excited state of the following equation accompanying combustion of hydrocarbons or hydrogen to the ground state.

H + O → OH ^* → OH + hν (1)
Therefore, a burner that uses a fuel that does not contain a hydrogen composition, such as carbon monoxide, requires a highly sensitive material that emits light at the wavelength and detects an ultraviolet sensor at about 100 nW / m ² or more.
However, the energy required to ignite the burner with electric sparks is almost constant regardless of the type of gaseous fuel. To obtain this energy, the distance between the electrodes is widened and the ignition transformer is set at the initial stage of discharge. It is necessary to generate a strong spark due to the capacitive component from

FIG. 4 is a diagram for explaining the voltage and spark current generated in the spark plug 6.
In the figure, the uppermost stage is an electric circuit of the ignition coil, V is a voltage waveform, and i is a current waveform. The subscripts 1 and 2 of the voltage V and the current i represent a primary circuit and a secondary circuit.
As shown in FIG. 4, immediately after a high voltage is generated from the secondary side of the ignition transformer, a capacitive spark is generated for about 5 μs. Since the avalanche causes ionization in the space, a low-voltage induced spark continues for about 2 ms thereafter. Since this induction spark continuously supplies energy to the fire core, a synthetic spark having both has a high ignition rate.

As described above, since the capacitive spark has a high voltage, the electron velocity is high, and various chemical species are excited. Therefore, when returning to the ground state, wide band emission from far ultraviolet to visible light is accompanied. Among them, far ultraviolet rays are absorbed by the quartz glass provided at the connection port of the flame detector and do not reach the ultraviolet sensor. Further, ultraviolet rays having a wavelength of UV-B or more do not cause photoelectrons on the cathode metal plate of the ultraviolet sensor, and therefore are not harmful to the lifetime of the ultraviolet sensor. On the other hand, the UV-C band ultraviolet rays reaching the ultraviolet sensor of the flame detector are much stronger than the ultraviolet rays from the above-mentioned flame and exceed the sensor allowable intensity of about 10 mW / m ² .

Also, the location where electric sparks are generated for burner ignition needs to be a location where fuel and air are mixed appropriately and a flame is formed, and that location is also suitable for detecting flames. Therefore, it is difficult to avoid the electric spark for ignition from the optical axis for detecting the flame, particularly in a pilot burner having a small aperture.
In recent years, a method of confirming whether or not the ultraviolet sensor of the flame detector has caused a self-discharge failure by blocking the ultraviolet light from the burning flame on the optical axis of the ultraviolet sensor has been used. The use of a shut-off device that shuts off ultraviolet rays is limited to the combustion of the burner and has not been used at the time of ignition.

In this embodiment, by operating the shut-off device 12 even while the ignition device is in operation, it is possible to prevent the sensor allowable strength from being exceeded and to extend the life of the ultraviolet sensor 11. The blocking device 12 needs to be made of a metal plate that blocks at least UV-C band ultraviolet rays for the reasons described above.
By the way, when the sensor protection for closing the shutoff device 12 is not performed during the operation of the ignition device, the operation is as follows.

FIG. 5 is a time chart when the solenoid valve of the air supply device is opened at time t11, power is supplied to the ignition device (ignition transformer) at time t13, and at the same time, the opening / closing drive of the shut-off device is started.
In this case, a spark is generated from the spark plug 6 after power is supplied to the ignition device at time t13 until the ignition device is deactivated at time t17. Therefore, the ultraviolet sensor of the flame detector receives ultraviolet rays at times t14 to t15 and t16 to t17 when the shut-off device is open, and the flame detector outputs a flame signal. However, the ultraviolet rays generated at these times are extremely strong ultraviolet rays as described above, and can cause great damage to a highly sensitive ultraviolet sensor for detecting flames.

On the other hand, in this embodiment, when the ignition device is in operation, the blocking device 12 is operated to block the incidence of ultraviolet rays on the ultraviolet sensor 11 of the flame detector 10. Therefore, it is possible to protect the ultraviolet sensor 11 from the strong ultraviolet rays at the time of ignition of the burner and extend the life of the flame detector 10.
Further, since the protection function of the ultraviolet sensor 11 is realized by using a shut-off device installed to monitor the abnormality of the flame detector 10, it is not necessary to provide a new shut-off device for protection. The cost can be reduced. Further, when the protection function is added to the existing flame monitoring device, a simple modification of the drive device is sufficient.

Furthermore, since the abnormality monitoring function of the flame detector 10 is activated after the ignition device is deactivated, the abnormality of the ultraviolet sensor 11 can be monitored during burner combustion. Therefore, the reliability of the flame detector 10 can be improved.
Further, when the shut-off device 12 is closed after the ignition device is deactivated, the abnormality monitoring function is activated when the ultraviolet sensor 11 detects a flame, so that the ultraviolet light is confirmed after confirming that the burner is burning. The abnormality monitoring function of the sensor 11 can be activated. Further, when the abnormality of the flame detector 10 is monitored, the shut-off device 12 is driven to open and close at a predetermined cycle. ) And can be confirmed alternately.

  Further, if it is determined whether or not the ignition device is operating based on the determination on the power source side and the shutoff device 12 is controlled to be closed, it is necessary to detect the operation on the high voltage ignition device side. Disappear. Furthermore, a desired operation can be obtained only by synchronizing the drive device that supplies the drive voltage to the interrupter drive coil 14 and the drive device that supplies the drive voltage to the ignition device (ignition transformer 33).

Further, if the ignition transformer 33 is configured to be stopped by a timer after a certain time from the start of operation, and the abnormality monitoring function is activated by the same timer, a flame that controls the ignition of the burner. The abnormality monitoring function can be operated from the monitoring device 20. Therefore, it is not necessary to use a dedicated frame relay.
As described above, a flame monitoring device including the abnormality monitoring function of the flame detector 10 and the protection function of the flame detector 10 can be provided.

  DESCRIPTION OF SYMBOLS 1 ... Burner body, 2 ... Air supply port, 3 ... Gas supply port, 4 ... Flame holding cylinder, 5 ... Flame port, 6 ... Spark plug, 7 ... High pressure cord connection port, 10 ... Flame detector, 11 ... Ultraviolet sensor , 12 ... Shutter (ultraviolet shield), 13 ... Amplifying substrate, 14 ... Shutter drive coil, 15 ... Connector, 20 ... Flame monitoring device, 33 ... Ignition transformer (burner igniter)

Claims (3)

An ultraviolet sensor that detects the flame by receiving ultraviolet light emitted by a burner flame;
An ultraviolet blocking unit that is disposed between the formation position of the flame and the installation position of the ultraviolet sensor and capable of blocking incidence of ultraviolet rays to the ultraviolet sensor;
An electric spark is generated near the formation position of the flame, and a burner ignition unit that ignites the burner by the electric spark;
A shut-off control unit that drives and controls the UV shut-off unit during operation of the burner ignition unit and shuts off the incidence of UV rays on the UV sensor ; and
An abnormality monitoring unit for monitoring abnormality of the ultraviolet sensor,
The abnormality monitoring unit monitors the abnormality of the ultraviolet sensor when the ultraviolet sensor detects a flame when driving the ultraviolet blocking unit and permitting the incidence of the ultraviolet ray after the operation of the burner ignition unit is stopped. A flame monitoring device characterized by starting . A power supply circuit for supplying a drive voltage to the burner ignition unit;
The flame monitoring device according to claim 1, wherein the shutoff control unit determines that the burner ignition unit is in operation when the power supply circuit is in operation. The abnormality monitoring unit drives and controls the ultraviolet blocking unit, and monitors the presence or absence of flame detection of the ultraviolet sensor when repeating blocking and permitting the incidence of ultraviolet rays to the ultraviolet sensor at a predetermined cycle. in the flame monitoring apparatus according to claim 1 or 2, characterized in that determining whether an abnormality in the ultraviolet sensor has occurred.

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