JP3843425B2 - Flame detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flame detection device having a function of preventing an unintended temperature rise of a solenoid coil that drives a shutter to open and close.
[0002]
[Related background]
An ultraviolet ray detection discharge tube (UV tube), which is a kind of ultraviolet sensor, is formed by enclosing a pair of discharge electrodes in a cylindrical glass tube that generate discharge upon receiving ultraviolet rays. For example, a flame for monitoring the combustion state of a gas burner Used as a detector. A flame detection apparatus using this type of UV tube generally includes a shutter 2 that is selectively positioned on the front surface of the light receiving portion of the UV tube 1 to block the input of ultraviolet rays, as shown in FIG. Then, the UV level detection circuit 4 detects the discharge current of the UV tube 1 driven by applying a high voltage by the UV tube driving circuit 3, and the UV output voltage (UV level) corresponding to the intensity of ultraviolet rays received by the UV tube 1. ). Typically, Japanese Patent Publication No. 44-1039 discloses the construction of a discharge tube (UV tube) for ultraviolet detection, and Japanese Patent Publication No. 47-7878 discloses its detection circuit.
[0003]
Incidentally, in the flame detection device, the UV level is generally set by the detection level setting circuit 6 using the level determination circuit 5 in order to prevent the self-discharge of the UV tube 1 and the on-failure that continues false output. When the UV level exceeds the determination threshold value, the shutter drive circuit 8 is driven under the control of the shutter cycle setting circuit 7 to input ultraviolet rays to the UV tube 1 over a predetermined time. To block. In the figure, reference numeral 2a denotes a solenoid coil that is energized by the shutter drive circuit 8 and opens the shutter 2.
[0004]
Specifically, as shown in FIG. 5, the operation waveform is integrated to obtain the UV voltage corresponding to the UV intensity by integrating the discharge current of the UV tube 1 when the shutter 2 is open, and this UV voltage is determined in a predetermined manner. When the threshold value Vth is reached, the shutter 2 is closed for a predetermined time Toff. When the detection of the UV voltage and the closing operation of the shutter 2 are repeated periodically, the frame relay circuit 9 is turned on to output a frame relay signal indicating flame detection.
[0005]
[Problems to be solved by the invention]
By the way, when the frame relay signal is off, the shutter 2 is generally kept open and the occurrence of flame is monitored by the UV tube 1. After the flame is detected, the existence / extinction of the flame is monitored while the shutter 2 is periodically closed as described above. Accordingly, since the frame relay signal is off and it is necessary to keep the shutter 2 open during a period of waiting for the occurrence of a flame (standby state), the solenoid coil 2a for driving the shutter 2 is energized for a long period of time. It is necessary to keep it as it is.
[0006]
Then, it cannot be denied that the solenoid coil 2a generates heat due to energization over a long period of time and the temperature rises. Moreover, since this type of shutter 2 (solenoid coil 2a) is used together with the UV tube 1 in a high temperature environment, the above-described temperature rise of the solenoid coil 2a not only damages the solenoid coil 2a itself but also the shutter. It can also cause malfunction.
[0007]
The present invention has been made in view of such circumstances, and its purpose is to effectively prevent an unintended temperature rise of a solenoid coil that opens and closes the shutter without impairing the original function of the shutter. An object of the present invention is to provide a flame detection device having a function capable of performing the above.
[0008]
[Means for Solving the Problems]
In order to achieve the above-described object, a flame detection apparatus according to the present invention is selectively positioned on the front surface of a light receiving unit of an ultraviolet sensor (for example, a UV tube) that receives a UV ray emitted from a flame and generates a discharge. A shutter mechanism comprising a shutter that blocks the input of ultraviolet light, a solenoid coil that displaces the shutter to allow the input of ultraviolet light to the ultraviolet sensor, and a frame relay that receives a discharge output of the ultraviolet sensor and outputs a flame detection signal A circuit, and a shutter drive circuit that controls energization of the solenoid coil in accordance with the output of the ultraviolet sensor and the output of the frame relay circuit,
Especially in the shutter drive circuit ,
When a flame detection signal is not output from the frame relay circuit, a shutter driving voltage that causes the solenoid coil to generate a force for displacing the shutter from the closed position to the open position and the shutter that has been displaced to the open position are held. Force is alternately generated with the shutter holding voltage generated in the solenoid coil to keep the shutter open.
Each time a flame detection signal is output from the frame relay circuit, energization of the solenoid coil is stopped for a predetermined time and the shutter is closed, and then the solenoid coil is energized and the shutter is opened.
It is characterized in that the the like.
[0009]
That is, when the output of the frame relay circuit is off and in a flame detection standby state (standby state), the solenoid coil is intermittently driven to prevent its temperature rise, and the frame relay circuit During the period when the output is turned on and the flame detection signal is output, the intermittent driving of the solenoid coil described above is stopped, and the solenoid coil is turned on for a predetermined time each time a flame is detected by the ultraviolet sensor. A normal control for opening and closing the shutter by performing an off operation is performed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a main part of a flame detection apparatus according to this embodiment. The same parts as those of the flame detection apparatus shown in FIG. This device is characterized in that a drive voltage control section 11 for changing the shutter drive voltage is provided in the shutter drive circuit 8 for applying a shutter drive voltage to the solenoid coil 2a, and the operation of the drive voltage control section 11 An intermittent drive circuit 12 for setting a cycle is provided, and the drive voltage control unit 11 and the intermittent drive circuit 12 are selectively driven according to the on / off state of the frame relay circuit 9. Yes.
[0012]
Specifically, the shutter drive circuit 8 is configured to generate a shutter drive voltage Von that causes the solenoid coil 2a to generate a force that displaces the shutter 2 from its closed position to an open position indicated by a broken line. And receiving an output from the shutter period setting circuit 7 as described above is turned off control has become a thing to stop the generation of the shutter drive voltage Von. For such a shutter drive circuit 8, the drive voltage controller 11 changes the operating condition of the shutter drive circuit 8 so that the shutter is displaced to the open position by the solenoid coil 2a instead of the shutter drive voltage Von. 2 is configured to generate a shutter holding voltage Vhold (<Von) that causes the solenoid coil 2a to generate a force that can hold the motor 2 in its open position.
[0013]
The drive voltage control unit 11 includes, for example, a switch circuit that changes a circuit constant of a voltage generation circuit (not shown) provided in the shutter drive circuit 8 to change and set the generated voltage. The intermittent drive circuit 12 includes an oscillation circuit that turns on the drive voltage control unit 11 at a predetermined cycle. In particular, the intermittent drive circuit 12 outputs a signal for turning on the drive voltage control unit 11 only when the frame relay circuit 9 is in an off state, that is, in a flame detection standby state (standby state). Configured to do.
[0014]
Thus, according to the flame detection apparatus configured as described above, when the flame detection apparatus is operated to detect the flame, first, the shutter drive circuit 8 is operated to drive the solenoid coil 2a, thereby opening the shutter 2. . Then, flame detection by the UV tube 1 is started. At this time, if no flame is generated, the flame is not detected by the UV tube 1 as a matter of course, and the shutter cycle setting circuit 7 described above does not output a shutter closing signal. Therefore, the shutter drive circuit 8 continues energization of the solenoid coil 2a and keeps the shutter 2 open. This state is a flame detection standby state (standby state). In this case, the frame relay circuit 9 also does not receive the shutter closing signal, so it is kept off and does not output a flame detection signal.
[0015]
Then, since the frame relay circuit 9 is in an OFF state, the drive voltage control circuit 11 is driven at a predetermined cycle under the control of the intermittent drive circuit 12 described above. As a result, the voltage generated by the shutter driving circuit 8 is alternately changed to the shutter driving voltage Von and the shutter holding voltage Vhold described above, and this periodically changing voltage is applied to the solenoid coil 2a as shown in FIG. The That is, the solenoid coil 2a is intermittently driven by the shutter driving voltage Von and the shutter holding voltage Vhold. The shutter 2 is pulled to the solenoid coil 2a side by the force generated in the solenoid coil 2a by the shutter drive voltage Von and is surely displaced to the open position, and is held at the open position by the subsequent shutter holding voltage Vhold. . In this holding state, even if thermal vibration is applied to the solenoid coil 2a and the holding of the shutter 2 at the open position becomes unstable, the shutter 2 is quickly returned to the open position again by the shutter drive voltage Von applied thereafter. Therefore, the shutter 2 is held stably in the open position for a long period of time.
[0016]
When a flame is generated in such a standby state and the flame is detected by the UV sensor 1, the shutter cycle setting circuit 7 outputs a shutter close signal for a predetermined time. Then, in response to the closing signal, the shutter driving circuit 8 stops the energization driving of the solenoid coil 2a as shown in FIG. 2, so that the shutter 2 is released from being held in the open position by the solenoid coil 2a and is closed. Return to. As a result, the input of ultraviolet rays from the flame to the UV tube 1 is blocked. At this time, when the closing signal is output from the shutter cycle setting circuit 7, the frame relay circuit 9 is turned on and outputs a flame detection signal.
[0017]
Then, in response to the output of the frame relay circuit 9, the intermittent drive circuit 12 stops its operation, and the operation of the drive voltage control unit 11 is prohibited. As a result, the shutter drive circuit 8 generates the above-described shutter drive voltage Von every time the shutter close signal from the shutter cycle setting circuit 7 disappears. Then, the solenoid coil 2a is driven by the shutter drive voltage Von to open the shutter, and the flame detection by the UV tube 1 is resumed. Whenever a predetermined level of flame (ultraviolet light) is detected, the energization drive of the solenoid coil 2a is stopped for a predetermined time as described above, so that the opening and closing of the shutter 2 and the intermittent flame detection by the UV tube 1 are repeated. Will be executed. The frame relay circuit 9 continues to output a frame relay signal (flame detection signal) over a period in which the shutter 2 is repeatedly opened and closed.
[0018]
Therefore, in the flame detection device that operates as described above, the solenoid coil 2a is intermittently driven alternately by the shutter drive voltage Von and the shutter hold voltage Vhold during standby for flame detection, so that the solenoid coil 2a is continuously driven by the shutter drive voltage Von. As compared with the case of driving the motor, the heat generation of the solenoid coil 2a can be suppressed, and the temperature rise can be effectively prevented. In addition, the power consumption can be reduced by the amount that the drive voltage of the solenoid coil 2a is intermittently lowered to the shutter holding voltage Vhold described above. Further, even if the drive voltage of the solenoid coil 2a is intermittently changed in this way, the shutter 2 can be kept stable at the open position as described above, so that the function of quickly detecting the occurrence of flame at the time of standby is possible. The effect that it does not spoil, etc. is exhibited.
[0019]
In order to prevent the temperature of the solenoid coil 2a from rising during standby, for example, as shown in FIG. 3A, after the shutter drive voltage Von is applied to the solenoid coil 2a to open the shutter 2, the solenoid coil 2a It is conceivable to change the voltage to be applied to the shutter holding voltage Vhold described above. However, in the case of such control, the shutter holding voltage Vhold generates only a weak force that can hold the shutter 2 in the open position in the solenoid coil 2a. Therefore, if thermal vibration is applied for some reason, As a result, the shutter 2 may be closed. When the shutter 2 is closed, even if a flame is generated, the ultraviolet rays emitted from the flame are blocked by the shutter 2, so that the flame cannot be detected by the UV tube 1.
[0020]
On the other hand, when the shutter drive circuit 8 itself is configured to alternately generate the shutter drive voltage Von and the shutter hold voltage Vhold, the flame is detected and the frame relay circuit 9 is activated as shown in FIG. Even when a flame (ultraviolet ray) is intermittently detected by the UV tube 1 while the shutter 2 is opened and closed, the shutter 2 may be closed due to thermal vibration. That is, when the shutter 2 is opened and UV detection is performed by the UV tube 1, if the driving voltage applied to the solenoid coil 2a is changed to the shutter holding voltage Vhold, the shutter 2 is caused by the thermal vibration applied at this time. May close, and there is a risk that detection of flame (ultraviolet rays) by the UV tube 1 may be interrupted. Then, the detection output by the UV tube 1 does not increase to a predetermined level, and the shutter cycle setting circuit 7 described above does not output a shutter close signal. Accordingly, since the frame relay circuit 9 is turned off, there is a problem that it is erroneously determined that the flame has disappeared despite the presence of the flame.
[0021]
In this regard, as described above, the solenoid coil 2a is intermittently driven by using the shutter driving voltage Von and the shutter holding voltage Vhold as described above only when the frame relay circuit 9 is in the OFF state and in the standby state for flame detection. According to the present apparatus, the above-described problems do not occur. The temperature rise of the solenoid coil 2a during standby is effectively suppressed, and the solenoid coil 2a is used only with the shutter drive voltage Von during the period when the flame relay circuit 9 is turned on and the flame detection is performed intermittently. The shutter 2 can be driven to open and close. Therefore, there is a great practical effect such that the temperature rise of the solenoid coil 2a can be suppressed and its operation can be stabilized without impairing the flame detection function.
[0022]
The present invention is not limited to the embodiment described above. For example, the intermittent drive cycle of the solenoid coil 2a using the shutter drive voltage Von and the shutter hold voltage Vhold may be determined according to the return force of the shutter 2 and the specification (magnetic force) of the solenoid coil 2a. Further, during standby, the solenoid coil 2a can be controlled to be turned off for a short period of time at a predetermined cycle. However, in this case, since the shutter 2 is closed when the solenoid coil 2a is turned off, if a flame is generated during this period, the flame detection timing is slightly delayed until the shutter 2 is opened. Therefore, as described above, it is preferable to intermittently drive the solenoid coil 2a so that the shutter 2 is kept open.
[0023]
Although the UV tube has been described as an example here, the present invention can be similarly applied to the case where a semiconductor ultraviolet sensor is used. In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.
[0024]
【The invention's effect】
As described above, according to the present invention, the temperature increase of the solenoid coil during standby for flame detection can be effectively suppressed, and the function of the normal flame detection operation is not hindered. In particular, there are significant practical effects such as stabilization of the operation of the flame detection device.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a main part of a flame detection apparatus according to an embodiment of the present invention.
FIG. 2 is a timing chart showing the operation of the flame detection apparatus shown in FIG. 1 and showing the relationship between the control mode of the shutter drive signal applied to the solenoid coil and the output of the frame relay circuit.
FIG. 3 is a diagram for explaining another form of control of the voltage applied to the solenoid coil and its problems.
FIG. 4 is a schematic configuration diagram of a main part of a conventional flame detection device.
FIG. 5 is a waveform diagram showing the basic operation of the flame detection apparatus.
[Explanation of symbols]
1 UV tube (ultraviolet sensor)
2 Shutter 2a Solenoid coil 7 Shutter cycle setting circuit 8 Shutter drive circuit 9 Frame relay circuit 11 Drive voltage controller 12 Intermittent drive circuit

Claims (1)

A UV sensor that generates a discharge in response to the UV light emitted by the flame ;
A shutter that is selectively positioned on the front surface of the light receiving portion of the ultraviolet sensor and blocks the input of ultraviolet rays to the ultraviolet sensor ;
A solenoid coil that displaces the shutter to allow input of ultraviolet rays to the ultraviolet sensor;
A frame relay circuit for receiving a discharge output of the ultraviolet sensor and outputting a flame detection signal;
A shutter drive circuit for controlling energization of the solenoid coil in accordance with the output of the ultraviolet sensor and the output of the frame relay circuit ;
The shutter driving circuit includes:
When a flame detection signal is not output from the frame relay circuit, a shutter driving voltage that causes the solenoid coil to generate a force for displacing the shutter from the closed position to the open position and the shutter that has been displaced to the open position are held. Force is alternately generated with the shutter holding voltage generated in the solenoid coil to keep the shutter open.
Each time a flame detection signal is output from the frame relay circuit, energization of the solenoid coil is stopped for a predetermined time to close the shutter, and then the solenoid coil is energized to open the shutter. A flame detection device.

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