JP2008089195A - Flame current detecting device and combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame current detecting device free from variation of detection values of electric current caused by dispersion of AC voltage applied to an electrode. <P>SOLUTION: In this flame current detecting device applying an earth electrode 1 as a burner, comprising a voltage application electrode 2 disposed on a flame forming position of the burner, and an AC power source 3 applying AC voltage to the voltage application electrode, and detecting flame current by converting the same into voltage data, a pseudo flame circuit A is disposed to constantly allowing pseudo flame current to flow to the burner and the voltage application electrode 2 in parallel with each other. A standard pseudo flame current value flowing in the pseudo flame circuit A in application of the standard voltage free from dispersion of voltage as AC voltage, is stored in a control means, and a correction coefficient is determined on the basis of the detected current value and the standard pseudo flame current value in non-combustion of the burner to correct the detected current value in combustion of the burner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flame current detection device and a combustion device, and more specifically, a flame current detection device provided with current detection means for detecting flame current generated by applying an alternating voltage between a burner and an electrode, The present invention relates to a combustion apparatus using the flame current detection apparatus.

  Recently, it has been strongly desired to suppress the emission amount of nitrogen oxide (NOx) generated during combustion even in a small combustion apparatus such as a water heater or a bath apparatus. Combustion devices that employ this method have been proposed (see Patent Document 1).

  As is well known, this type of two-stage combustion system ignites an air-fuel mixture in which primary air and fuel gas are mixed in an oxygen-deficient state to generate a primary flame (primary combustion). By supplying secondary air to the combustion gas and generating a secondary flame (secondary combustion), the unburned gas is completely burned and the generation of nitrogen oxides is suppressed.

  In a combustion apparatus that employs such a two-stage combustion method, it is necessary to keep the supply amounts of air (primary air and secondary air) and fuel gas supplied to the burner to an appropriate level. In other words, the combustion state of the burner can be maintained in a normal state only by maintaining these supply amounts appropriately, and as a result, the above-described complete combustion of the unburned gas and the suppression of the generation of nitrogen oxides can be achieved. .

  Therefore, in a combustion apparatus that employs such a two-stage combustion method, it is important to maintain the combustion state of the burner normally, and it is required to detect burner combustion abnormality early and accurately. .

  On the other hand, when the burner falls into a combustion abnormality, a change appears in the flame (flame) formed in the burner. For example, if the amount of air (particularly primary air) supplied to the burner decreases, unburned CO components increase during primary combustion and the primary flame expands (the height of the primary flame increases). Such a change in flame is accompanied by a change in the concentration of ions contained in the flame. Therefore, the applicant of the present application has come to consider detecting a combustion abnormality using a flame current detection device that detects whether or not the burner is ignited by using ions in the flame (rectifying action of the flame).

JP 2004-205119 A Japanese Utility Model Publication No. 2-41474 Japanese Examined Patent Publication No. 61-52367

  By the way, as a flame current detection device capable of detecting the current value of the flame current, devices as shown in Patent Documents 2 and 3 have been proposed. As a device, the flame current detection device shown in FIG. 7 was devised.

  FIG. 7 shows an example of a flame current detector configured to be able to read the current value of the flame current. In this flame current detection device, a grounded metal casing of a burner is used as a ground electrode 1, and a flame rod 2 is disposed at a flame forming position of the burner so as to face the flame and serve as a voltage application electrode. An AC power source 3 for applying an AC voltage is connected via capacitors 4 and 5 (hereinafter, this circuit is referred to as a frame circuit).

  Then, as a detection circuit for detecting a current (flame current) flowing through the frame circuit during burner combustion, capacitors 6 and 7 and a diode 8 having an anode grounded in parallel with the frame rod 2 and the ground electrode 1. And the cathode side of the diode 8 is connected to the non-inverting input terminal of the operational amplifier 9. The operational amplifier 9 includes a DC power source 10 and a resistor 11 for applying a DC voltage Vcc, as well as current detection means for detecting flame current flowing between the frame rod 2 and the ground electrode 1 by converting it into voltage data. In the configuration, the DC power source 10 is connected to a non-inverting terminal of an operational amplifier 9 through a resistor 11. The output terminal of the operational amplifier 9 is connected to the A / D input port of the microcomputer constituting the control means 17.

  In the figure, reference numerals 12 and 13 denote resistors, respectively, and a resistor 14 for applying negative feedback is connected between the output terminal and the inverting input terminal of the operational amplifier 9. Further, in the figure, the part surrounded by a chain line shows the equivalent circuit B of the flame, and the electric action (rectifying action) of the flame when the burner is in the combustion state (combustion state) and the flame is formed is resistance 15. And replaced with a diode 16. Therefore, when the burner is in a fire extinguishing state (during non-burning), the resistor 15 and the diode 16 are not present, and the frame rod 2 and the ground electrode 1 are electrically open.

  Next, the operation of the flame current detection device configured as described above will be described. In this current detection device, when a positive voltage is applied from the AC power source 3, currents (If, I +) flow as indicated by solid arrows in the figure, and the capacitors 6 and 7 are supplied with currents ( I +). On the other hand, when a negative voltage is applied by the AC power source 3, no current flows in the flame equivalent circuit, discharge from the capacitors 6 and 7 is started, and the flame current detection circuit has a one-dot chain line in the figure. Current (I−) flows in the direction indicated by the arrow. At this time, the capacitors 6 and 7 are discharged with a current obtained by averaging the difference between (I +) and (I−), that is, (If).

  On the other hand, in order to charge the capacitors 6 and 7 from the fixed resistor 11, a voltage balanced with the average value of (If) is input to the non-inverting input terminal of the operational amplifier 9.

  As a result, a voltage signal proportional to the current (If) flowing in the flame equivalent circuit is output from the operational amplifier 9, and the voltage signal is taken into the control means 17, whereby the control means 17 determines the current value of the flame current. Detection is possible. Specifically, the control means 17 includes a conversion program for converting a voltage signal input to the A / D input port into a current value, and the voltage signal input to the A / D input port according to this program. Is converted into a current value, and this current value is read as the current value of the flame current.

  However, in the configuration in which the flame current detection value is detected using such a flame current detection device, if the voltage of the AC power supply 3 varies, the flame current detection value also varies. Therefore, it is possible to accurately detect the flame state. There was a problem that I could not.

  In other words, the flame current detection device proposed in the present application aims to detect the state of the flame formed in the burner from the detection value of the flame current as described above. However, the AC power source 3 in this type of current detection device usually has a commercial power source (AC 100 V) once converted into a direct current (for example, DC 15 V), and then this DC power source is oscillated by a DC-DC converter to obtain a predetermined AC power source. For example, when a 64V transformer is attached to a DC-DC converter for the purpose of generating an 80V AC power supply, the AC power supply 3 has an expected voltage (AC80V). Is not obtained, and as a result, a deviation occurs in the current detection value.

  Specifically, the resistance value of the flame (the resistance value of the fixed resistor 15 shown in the equivalent circuit of the flame) is usually about several MΩ to several tens of MΩ depending on the state of the flame. When the voltage of the power supply 3 is 80 V, the current flowing through the flame (frame current) is as small as several μA to several tens μA. Since the flame current detection device is intended to detect such a small current value as described above, for example, when the voltage of the AC power supply 3 varies up and down by about 20 V, the voltage of the current value to be detected is detected. Since the variation is too large, it is impossible to accurately grasp the state of the flame based on the detected current value.

  The present invention has been made in view of such problems, and adopts a two-stage combustion method by providing a flame current detection device in which the current detection value does not vary due to variations in the AC voltage applied to the electrodes. It is an object of the present invention to make it possible to accurately detect a burner combustion abnormality.

  In order to achieve the above object, a flame current detection device according to claim 1 of the present invention comprises a burner, an electrode exposed to the flame of the burner, and an AC voltage applied between the burner and the electrode. In a flame current detection device comprising current detection means for detecting the flame current generated by converting the voltage data into voltage data, a pseudo flame circuit for constantly flowing a pseudo flame current is provided in parallel with the burner and the electrode, and Standard pseudo flame current storage means for storing in advance a standard pseudo flame current value that flows through the pseudo flame circuit when a standard voltage is applied as the AC voltage is provided. The actual flame current is calculated based on the detected current value of the current detection means at each time and the standard simulated flame current value stored in the standard simulated flame current storage means.

As a preferred embodiment of the flame current detection apparatus according to claim 1, the actual flame current is calculated by the control means according to the following approximate expression.
(Actual flame current) ≒ (standard simulated flame current value / current value detected during non-combustion) x (current value detected during combustion-current value detected during non-combustion)

  That is, in the flame current detection device according to claims 1 and 2, the burner is extinguished because a pseudo flame circuit that constantly flows a pseudo flame current in parallel to the burner (earth electrode) and the electrode (voltage application electrode) is provided. Even when the burner is in a state (non-combustion) and there is no flame in the burner, a current flows through the simulated flame circuit, and the current detection means can detect the current value in this state.

  On the premise of such a configuration, in the flame current detection device according to claim 1, when the burner is in a fire extinguishing state, the non-combustion detection current value actually detected by the current detection means, and the standard simulated flame current Based on the standard pseudo flame current value stored in the storage means (the current value that flows through the pseudo flame circuit when a standard voltage that does not vary as an AC voltage is applied), the control means determines whether the AC voltage varies (corrects). Coefficient). Then, the control means calculates an actual flame current value at the time of burner combustion based on this variation state and the detected current value of the current detection means at the time of burning and non-burning of the burner.

  Specifically, as shown in claim 2, a detected current value (non-detected) detected by the current detecting means when the burner is not burned from a detected current value (detected current value when burning) detected by the current detecting means during burner combustion. By subtracting the current value detected during combustion), the current value (current value of the flame current obtained by calculation) that has been removed from the simulated flame circuit is calculated, and the above correction obtained when the burner is not burned is calculated. The actual flame current is calculated by multiplying the coefficient.

  The flame current detection device according to claim 3 of the present invention is the flame current detection device according to claim 1 or 2, further comprising switch means capable of turning on / off the application state of the AC voltage, and the burner. Failure determining means for determining whether or not a circuit component has failed in the flame current detection device based on a change state of an output signal of the current detection means when the application state of the AC voltage is switched by the switch means during non-combustion It is provided with.

  That is, the flame current detection device according to claim 3 is characterized in that in the flame current detection device according to claim 1 or 2, a current can flow through the simulated flame circuit even when the burner is in a fire extinguishing state. Utilizing this, the failure determination means determines the presence or absence of a failure in the circuit component when the burner is not burning. Specifically, for example, when the AC voltage is switched from OFF to ON, the rise time of the voltage signal, the peak value of the voltage level, etc. are monitored to determine whether those values are normal. Identifies the circuit component that is causing the abnormal value.

  According to a fourth aspect of the present invention, there is provided the flame current detection device according to any one of the first to third aspects, wherein the burner is in a non-burning state and a pre-stored non-burning time in the non-burning state. Insulation deterioration determination means for determining an insulation deterioration state between the burner and the electrode based on a comparison result with a reference current value in the case where the insulation deterioration determination means determines that the insulation deterioration has occurred. It is characterized in that at least one of notification by the notification means or change of the voltage data threshold value of the flame detection current in the control means is executed.

  That is, the flame current detection device according to claim 4 is similar to the flame current detection device according to claim 3 described above, in the flame current detection device according to claims 1 to 3, the burner is in a fire extinguishing state. Even when there is a certain time, it uses the current flowing through the pseudo flame circuit. Specifically, the insulation deterioration is based on the comparison result between the detected current value at the time of non-burning of the burner and the pre-stored reference current value at the time of non-burning (current value when there is no insulation deterioration between the burner and the electrode). A determination means determines an insulation deterioration state between the burner and the electrode.

  A combustion apparatus according to claim 5 is a combustion apparatus in which the flame current detection apparatus according to any one of claims 1 to 4 is mounted, and is in an oxygen-deficient state formed by mixing primary air and fuel gas. In the combustion apparatus in which the air-fuel mixture undergoes primary combustion and further receives secondary air supply to perform secondary combustion, a first ion current detection member is provided in the flame of the primary combustion, and the base of the flame of the primary combustion A secondary air supply port for supplying secondary air is provided, a second ion current detection member is provided in the vicinity of the secondary air supply port, and the first ion current detection member is the electrode of the first flame current detection device. The second ion current detection member is configured as the electrode of the second flame current detection device, and is supplied based on the flame current value calculated in each of the first and second flame current detection devices. Used air and fuel gas And controlling at least one.

  That is, the combustion apparatus according to claim 5 is a combustion apparatus that employs a two-stage combustion system, wherein a first ion current detection member (a voltage application electrode of the first flame current detection apparatus) is provided in a flame of primary combustion. In addition, a second ion current detection member (voltage application electrode of the second flame current detection device) is provided in the vicinity of the secondary air supply port, and the flame current is detected by each flame current detection device and supplied to the burner. Since at least one of the air and the fuel gas is controlled, the combustion state of the burner can be maintained in a normal state.

  According to the flame current detection device of claim 1, the control means performs actual flame current based on the detected current value of the current detection means and the standard simulated flame current value when the burner is burning and when not burning. Therefore, it is possible to provide a flame current detection device in which the detection value of the flame current does not change even if the AC voltage applied between the burner and the electrode varies.

  Moreover, such a flame current detection device has a hardware-like pseudo flame circuit (specifically, a resistance), compared to a flame current detection device provided with current detection means for detecting flame current by converting it into voltage data. Therefore, it is possible to provide a flame current detection device that is not affected by variations in AC voltage at a low cost.

  Also, in terms of software, the calculation for calculating the actual flame current is a simple mathematical formula as described in claim 2, so that the burden placed on the storage area of the control means is small, which also increases the cost. Can be suppressed.

  According to the flame current detection device of claim 3, when the burner is not burned, the failure determination means determines whether or not the circuit component has failed based on the change state of the output signal of the current detection means. And defects can be detected early.

  According to the flame current detection device of the fourth aspect, when the insulation deterioration determining means determines the insulation deterioration state between the burner and the electrode at the time of non-burning of the burner, and if it is determined as insulation deterioration, that is the effect. Is notified by a predetermined notification means, or at least one of the process of changing the voltage data threshold value of the flame detection current in the control means is executed, so that early detection of insulation deterioration or ignition detection error due to insulation deterioration is performed. Can be reduced.

  According to the combustion apparatus of claim 5, in the combustion apparatus of the two-stage combustion system, since the combustion state of the burner is maintained in a normal state, complete combustion of unburned gas can be achieved, and nitrogen oxides It is possible to provide a combustion apparatus that generates less.

Embodiment 1
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit diagram showing a schematic configuration of a flame current detection apparatus according to the present invention. In order to cancel the variation in the AC voltage applied to the electrode and prevent the variation in the detected value of the flame current, this flame current detection device has a hardware This is an improvement from both sides of the software. Therefore, parts having the same circuit configuration are denoted by the same reference numerals and description thereof is omitted.

  Specifically, as an improvement in hardware, in the flame current detection device of the present invention, the ground electrode (burner metal casing) 1 and the frame rod (electrode) 2 are arranged in parallel as shown in FIG. A simulated flame circuit A is provided.

  The simulated flame circuit A is a circuit provided to allow a current (bias current) to flow through the frame circuit even when the burner is in a fire extinguishing state (non-combustion). Thus, it is configured by a circuit configuration similar to the flame equivalent circuit, that is, a series circuit of a resistor 18 and a diode 19, and is configured by connecting this series circuit in parallel to the ground electrode 1 and the frame rod 2. As the resistor 18, a resistor having a resistance value (for example, about 36 MΩ) comparable to that of the flame resistance component (the resistor 15) is used.

  On the other hand, as a software improvement, first, in detecting the flame current based on the voltage signal output from the operational amplifier 9, the control means 17 cancels the voltage variation of the AC power supply 3. Executed. The procedure will be described below.

  First, the current value (standard pseudo flame) that flows in the pseudo flame circuit A when a standard voltage is applied as an AC voltage to the frame circuit in a predetermined storage area (standard pseudo flame current storage means) of the microcomputer constituting the control means 17. Current value) is stored in advance. Here, this standard voltage means the output voltage of the AC power supply 3 without variation. In the present embodiment, a power source that outputs AC 80V is used as the AC power source 3, and therefore the standard voltage is AC 80V.

  For this standard simulated flame current value, data acquired in advance through experiments or the like is used. Specifically, an AC power supply 3 having no variation is prepared, and an AC voltage is applied to the frame circuit when the burner is in a fire extinguishing state (non-combustion), and the current value flowing through the pseudo flame circuit A at that time ( More specifically, the current value converted by the control means 17 based on the voltage signal output from the operational amplifier 9 in this state is acquired, and the data is stored in advance in the standard simulated flame current storage means. .

  In other words, common data is used for the standard pseudo flame current value for the flame current detectors of the same standard. Therefore, the standard pseudo flame current value is stored in advance in a non-volatile memory such as a ROM.

  On the other hand, in each flame current detection device, when the burner is in a fire extinguishing state (non-combustion), the control means 17 determines the current value of the current flowing through the simulated flame circuit A (non-combustion detection current value) as described above. The current value is converted based on the output signal of the operational amplifier 9, and the value is stored in a predetermined storage area in the microcomputer. That is, this non-combustion detected current value is based on the premise that the AC power supply 3 varies (in other words, regardless of whether the AC power supply 3 varies). Calculated and stored. Therefore, as a storage area for storing the non-combustion detection current value, a storage area in which data can be written for each flame current detection device is preferably used.

  The calculation and storage of the non-combustion detected current value can be performed for each apparatus in advance before shipment from the factory, but in the flame current detection apparatus shown in the present embodiment, the control means 17 is applied after the apparatus is installed. It is programmed to be performed at a predetermined timing such as when power is turned on.

  When the burner is in the combustion state with the standard simulated flame current value and the non-combustion detected current value being stored in the control means 17 as described above, the control means 17 The flame current (the detected current value at the time of combustion) is calculated based on the signal. At this time, the actual flame current is calculated by canceling the variation of the AC power supply 3 by the following approximate expression.

(Actual flame current) ≒ (standard simulated flame current value / current value detected during non-combustion) x (current value detected during combustion-current value detected during non-combustion)

  That is, in the flame current detection device of the present invention, since the pseudo flame circuit A that constantly feeds the pseudo flame current is provided in parallel to the ground electrode 1 and the frame rod 2, the voltage signal output from the operational amplifier 9 is provided. Since the detected current value at the time of combustion calculated on the basis of the above includes the current flowing through the flame equivalent circuit B and the simulated flame current (bias current) flowing through the simulated flame circuit A, the non-burning is detected from the detected current value during combustion. The detection current value is subtracted.

  However, if the AC power supply 3 varies as it is, the current value (read current value) calculated by the control means 17 also varies depending on the voltage, so that an accurate current value cannot be detected. Specifically, as shown in FIG. 2, when the AC voltage is higher than the standard voltage (AC80V) (showing the case of AC96V in FIG. 2), the read current value of the control means 17 is higher than that of the standard voltage. On the other hand, when the AC voltage is lower than the standard voltage (showing the case of AC64V in FIG. 2), the read current value of the control means 17 is also lowered.

  Therefore, in the flame current detection device of the present invention, in order to correct such variations in the AC power supply 3, the control means 17 obtains a correction coefficient by dividing the standard simulated flame current value by the non-burning detection current value, The correction coefficient is multiplied by a value obtained by subtracting the non-combustion detection current value from the combustion detection current value to calculate a current value obtained by canceling the variation of the AC power supply 3, that is, an actual flame current value.

  As described above, in the flame current detection device of the present invention, the pseudo flame circuit A is provided in parallel to the ground electrode 1 and the frame rod 2 so that the pseudo flame current flows through the pseudo flame circuit A when the burner is not burned. Therefore, the standard simulated flame current value is stored in the standard simulated flame current storage means of the control means 17, and the standard simulated flame current value is detected by the control means 17 when the burner is burned and when not burned. The actual flame current can be calculated based on the current values (the detected current value during combustion and the detected current value during non-combustion).

Embodiment 2
Next, another embodiment of the flame current detection device of the present invention will be described with reference to FIG. In the flame current detection device shown in the second embodiment, the control means 17 determines whether or not a circuit component has failed in the flame current detection device, and determines the insulation deterioration state between the ground electrode 1 and the frame rod 2. The switch means 20 that can turn on / off the application state of the AC voltage to the frame circuit of the flame current detection device shown in the first embodiment is added to the software of the control means 17. A program for making these determinations has been added. Since other configurations are the same as those in the above-described embodiment, common portions are denoted by the same reference numerals and description thereof is omitted.

  As described above, the switch means 20 is a means for turning on / off the application state of the AC voltage to the frame circuit, and is arranged between the AC power supply 3 and the capacitor 4 of the frame circuit as shown in FIG. Established. As the switch means 20, an element (for example, an element having a switching function such as a transistor) whose ON / OFF switching can be controlled by the control means 17 is used.

  On the other hand, the control means 17 stores a program (failure determination means) for determining whether or not a circuit component of the flame current detection device is faulty, and a program (insulation deterioration determination means) for determining an insulation deterioration state. Is done.

  First, the failure determination means will be described. This failure determination means switches the application state of the AC voltage to the frame circuit by the switch means 20 when the burner is not burning, and the flame is determined based on the change state of the output signal (voltage signal) of the operational amplifier 9 at that time. It is determined whether or not a circuit component has failed in the current detection device.

  That is, in the flame current detection device of the present invention, the circuit for detecting the current flowing through the frame circuit includes resistors 12, 13 and capacitors 6, 7, etc., and these resistance values and capacities are determined in advance. Since it is known, the time constants of these detection circuits are specified in advance. Similarly, since the voltage value of the DC power supply 10 and the resistance values of the resistors 11 and 18 are known in advance, the pseudo flame current value (output voltage from the operational amplifier 9) when the burner is not burned is also specified in advance. .

  Therefore, based on these elements that can be grasped in advance, the failure determination means determines the output voltage of the voltage signal output from the operational amplifier 9 when an AC voltage is applied to the frame circuit when the burner is in the non-burning state. The rise time, its peak value, etc. are specified in advance by experiment or calculation, and those values and data for specifying a failure site predicted when these values are abnormal are specified by the control means 17. Are stored in a storage area (for example, a non-volatile storage area such as a ROM).

  On the premise of the existence of these data, the control means 17 turns off the switch means 20 and temporarily stops the application of the AC voltage to the frame circuit when the burner is not burning, and then for a predetermined time. After the elapse of time, the switch means 20 is turned on again to start application of an AC voltage to the frame circuit. At this time, the change state of the voltage signal output from the operational amplifier 9 (specifically, the rise time or peak of the output voltage) Value).

  Then, the detected value is compared with the data corresponding to these stored in advance to determine whether or not the detected value is abnormal. If there is an abnormality, the abnormality is present. A failure part predicted corresponding to the detected value is specified, and the failure part, the failure state, and the like are displayed through predetermined notifying means (not shown) (for example, display means of a combustion apparatus to which the present apparatus is attached).

  For example, when the switch means 20 is turned on and an AC voltage is applied, if the rise of the voltage signal from the operational amplifier 9 is earlier than the stored data, a short circuit of the resistors 12 and 13 is expected. Therefore, these are displayed as failure parts, and if the voltage signal from the operational amplifier 9 remains at 0 V, it is predicted that the resistor 11 has been removed, so that it can be displayed. .

  As described above, in the flame current detection apparatus shown in the present embodiment, the switch means 20 is provided in the frame circuit, and the failure determination means can be operated only by storing the program and data constituting the failure determination means in the control means 17. Since the presence / absence of the failure of the circuit component is automatically determined, the failure or failure of the circuit component can be detected at an early stage. Moreover, it can be realized at low cost simply by adding the switch means 20 in terms of hardware to the flame current detection device of the first embodiment described above.

  Note that the timing for performing the above-described failure determination can be arbitrarily set on the program of the control means 17, but for example, it is set so as to be executed at a predetermined fixed time aiming at the non-burning time of the burner. Or can be set to run every time the burner flame is extinguished.

  Next, the insulation deterioration determining means will be described. In this insulation deterioration determining means, the control means 17 compares the detected current value when the burner is not burned with a pre-stored reference current value when the burner is not burned, and the ground electrode 1 and the frame based on the comparison result. The state of insulation deterioration with the rod 2 is determined.

  Specifically, first, a pseudo flame is detected in a predetermined storage area of the control means 17 (for example, a non-volatile storage area such as a ROM) without insulation deterioration between the ground electrode 1 and the frame rod 2. The current value is stored as a reference current value. That is, this reference current value is determined at an appropriate time when the accumulated operation time after factory shipment or after installation of the apparatus is short, in other words, before the insulation deterioration occurs between the ground electrode 1 and the frame rod 2. At the time of combustion, the switch means 20 is turned on, and the value of the current flowing through the pseudo flame circuit A is calculated and stored from the output voltage of the operational amplifier 9 at that time.

  On the assumption that the reference current data exists, the control means 17 turns on the switch means 20 and applies an AC voltage to the frame circuit when the burner is not in combustion, Further, a pseudo flame current value is calculated based on the voltage signal output from the operational amplifier 9, and this value is compared with a reference current value to determine the presence or absence of insulation deterioration.

  That is, when dust or moisture between the ground electrode 1 and the frame rod 2 adheres and the insulation state between the two deteriorates, the electrical resistance is connected in parallel between them when viewed electrically. Since it becomes the same situation, in such a case, the pseudo flame current value read by the control means 17 will fall. The insulation deterioration determining means determines the presence or absence of insulation deterioration using such characteristics. Specifically, the pseudo flame current value is determined in advance by comparing the pseudo flame current value with the reference current value. If the reference current value falls below a predetermined amount that has been set, it is determined that insulation deterioration has occurred between the ground electrode 1 and the frame rod 2.

  When the control means 17 determines that the insulation deterioration has occurred between the ground electrode 1 and the frame rod 2 as described above, a predetermined notification means (for example, a combustion apparatus to which the present apparatus is attached) At least one of the notification or the change of the voltage data threshold value of the flame detection current in the control means 17 is executed.

  Here, the “voltage data threshold value of the flame detection current in the control means 17” is used to determine “there is a flame” when detecting the presence or absence of flame using the flame current detection device of the present invention. It means a threshold value for the output voltage of the operational amplifier 9 to be set. That is, as described above, the flame current detection device of the present invention can be read into the control means 17 up to a specific current value of the flame current based on the output voltage of the operational amplifier 9 so that the combustion state of the flame can be confirmed. However, since the presence of flame is naturally detected as in the conventional product, if there is insulation degradation, the threshold for the output voltage from the operational amplifier 9 is changed to a certain level (more specifically, insulation In the case of deterioration, the amount of current flowing through the resistor 11 (see FIG. 3) decreases and the voltage drop in the resistor 11 decreases, so that the voltage input to the operational amplifier 9 and the control means 17 increases. Compared with before insulation deterioration, even if an actual flame current flows, the input voltage value to the control means 17 is increased.In order to cope with this, the voltage threshold value for flame presence / absence determination is raised to a certain level.) Is in a burning state To prevent erroneous non-ignition determination in located in.

  As described above, in the flame current detection apparatus shown in the present embodiment, the insulation deterioration between the ground electrode 1 and the frame rod 2 can be performed only by storing the program and data constituting the insulation deterioration determination means in the control means 17. Since the voltage data threshold value for determining “with flame” is changed when it is determined that there is insulation deterioration, it is possible to reduce the occurrence of ignition detection errors due to insulation deterioration. .

  Note that the timing for determining the insulation deterioration can be arbitrarily set on the program of the control means 17 as in the case of the above-described failure determination timing. Therefore, for example, it can be set so as to be executed aiming at a non-burning time of the burner every predetermined time, or to be executed every time the flame of the burner is extinguished. In addition, since the determination of the insulation deterioration does not require interlocking with the switch means 20, it can be performed in the control means 17 of the flame current detection device described in the first embodiment.

Embodiment 3
Next, a third embodiment of the present invention will be described with reference to FIGS. The third embodiment shows a case where the flame current detection device of the present invention is used for combustion control of a combustion device adopting a two-stage combustion method.

  FIG. 4 is a block diagram showing a schematic configuration of the combustion apparatus. In the figure, reference numeral 100 denotes a controller of the combustion apparatus, and this controller 100 is provided with a microcomputer in which a program for controlling each part of the combustion apparatus is mounted and a memory (storage area) that stores predetermined data. The controller 100 is connected to first and second flame current detection devices 101a and 101b as will be described later. In this embodiment, the microcomputer of the controller 100 is used as the control means 17 of the flame current detection devices 101a and 101b.

  In addition, the controller 100 includes an igniter 102 that constitutes ignition means for the burner, a blower 103 that sends combustion air to the burner, a fuel gas supply valve 104 that switches between supply / cutoff of fuel gas to the burner, and a burner. A fuel gas proportional valve 105 for adjusting the supply amount of the fuel gas to be supplied is provided, but since these configurations are well known, description thereof will be omitted.

FIG. 5 is an explanatory cross-sectional view showing a schematic configuration of a burner in a two-stage combustion type combustion apparatus.
In this type of two-stage combustion type burner (hereinafter simply referred to as a burner) 21, as described above, an oxygen-deficient mixture obtained by mixing primary air and fuel gas is subjected to primary combustion, and further to secondary combustion. Secondary combustion is performed by supplying air.

  In FIG. 5, 22 indicates a primary flame generated by primary combustion, 23 indicates a secondary flame generated by secondary combustion, and 24 indicates a gas supply to which an air-fuel mixture formed by mixing primary air and fuel gas is sent. Reference numeral 25 denotes a mixture supply port for supplying the mixture in the gas supply chamber 24 to the position where the primary flame 22 is formed, and reference numeral 26 denotes a secondary air supply port.

  And in this embodiment, in order to detect the combustion state in such a burner 21, the two flame current detection apparatuses 101a and 101b are used. That is, the flame rod (first ion current detection member) 2a of the first flame current detector 101a is disposed in the center of the primary flame 22 as shown in FIG. The frame rod (second ion current detection member) 2b of the second flame current detection device 101b is disposed in the vicinity of the secondary air supply port 26.

Here, the flame rod 2a of the first flame current detection device 101a is arranged in the primary flame 22, but since the unburned mixture is contained in the primary flame 24, the flame rod 2a is arranged. The temperature of this part is low, and the frame rod 2a does not become so hot as a whole, so that it is prevented from being deteriorated by heat. On the other hand, the frame rod 2b of the second flame current detection device 101b is also exposed to the secondary flame 23 because it is disposed at a position where the secondary air supplied (injected) from the secondary air supply port 26 hits. Therefore, the temperature rise of the frame rod 2b is suppressed and deterioration due to heat is prevented.

FIG. 6 is an explanatory diagram showing the relationship between the read current value of the control means 17 in the first flame current detection device 101a, the read current value of the control means 17 in the second flame current detection device 101b, and the amount of carbon monoxide CO. It is.

In FIG. 6, the regulation value for the emission amount of carbon monoxide CO is set in advance so as to conform to environmental standards. That is, the regulation value (threshold value) of the exhausted CO amount corresponds to the difference (μA) between the read current value of the second flame current detection device 101b and the read current value of the first flame current detection device 101a.

  As shown in FIG. 6, when the burner 21 is normally combusting (when the amount of exhausted CO is small), the primary flame 22 contains a large amount of carbon monoxide CO ions generated by the combustion. The read current value (ion current detection value) of the flame current detection device 101a of 1 becomes high. On the other hand, most of the flame rod 2b of the second flame current detection device 101b is encased in secondary air, so that the amount of ions generated in the surroundings is extremely small, and combustion of carbon monoxide CO and hydrogen H is mainly performed. Even when the secondary flame 23 exists, the read current value of the second flame current detector 101b is considerably lower than the read current value of the first flame current detector 101a.

  Here, if only the amount of air supplied by the blower 103 decreases for some reason, the amount of unburned CO component increases, and the first flame current installed in the primary flame 22 due to the extension of the primary flame 22. Not only the portion of the detection device 101a that is surrounded by the unburned mixture of the flame rod 2a increases, but also the combustion temperature decreases and the ion concentration of the primary flame 22 decreases, so that the read current of the first flame current detection device 101a The value goes down.

  On the other hand, the read current value of the second flame current detection device 101b is obtained because the one hydrocarbon CO component generated due to air shortage in the primary flame 22 reaches the frame rod 2b of the second flame current detection device 101b. The read current value of the second flame current detection device 101b increases. That is, the difference between the read current value of the first flame current detection device 101a and the read current value of the second flame current detection device 101b increases as the amount of air (air volume) supplied by the blower 103 decreases.

  Therefore, a calculation value of the difference D between the two read current values corresponding to the regulation value X (see FIG. 6) of the emission concentration of carbon monoxide CO is obtained in advance by experiment, and this is used as a threshold value to control the controller 100 of the combustion device. It is stored in the memory prepared for.

  Then, the controller 100 calculates the difference between the read current value of the second flame current detection device 101b and the read current value of the first flame current detection device 101a, and further calculates the calculated value and the threshold value stored in the memory. Compare.

If the calculated value is smaller than the threshold value as a result of the comparison, the controller 100 determines that the combustion state of the burner 21 is normal. On the other hand, if the calculated value reaches the threshold value or the calculated value exceeds the threshold value, the burner 21 is determined to be abnormal combustion.

If it is determined that the combustion is abnormal, the combustion is performed by increasing the amount of air blown from the blower 103 or by reducing the amount of fuel gas supplied to the burner 21 by reducing the valve opening of the fuel gas proportional valve 104. Normalize the condition. At that time, the threshold value may have a width d, and it may be determined that the combustion is abnormal when the calculated value enters the threshold value region (FIG. 6). That is, a predetermined width d may be set on the side where the carbon monoxide CO concentration is smaller than the regulation value X, and it may be determined that the combustion is abnormal before the calculated value reaches the regulation value X.

  Further, after determining that the combustion is abnormal and performing the above processing, when the combustion is normalized, the controller 100 controls the blower 103 and the fuel gas proportional valve 105 so that the calculated value does not reach the threshold value. Adjust the opening. Then, when the controller 100 determines that the combustion is abnormal so that appropriate maintenance can be performed, a warning is displayed on a predetermined notification means (for example, a display means of the combustion device), so that the user Call attention to.

As described above, in the combustion apparatus shown in the present embodiment, in the combustion apparatus adopting the two-stage combustion method, the first ion current detection member is provided in the flame of the primary combustion, and the second in the vicinity of the secondary air supply port. By providing an ion current detection member, each flame current detection device detects the flame current and controls at least one of air and fuel gas supplied to the burner, so that the combustion state of the burner is maintained in a normal state. Therefore, it is possible to provide a combustion apparatus that can achieve complete combustion of unburned gas and generate less nitrogen oxides.

  Note that the above-described embodiments merely show preferred embodiments of the present invention, and the present invention is not limited to these, and various design changes can be made within the scope thereof.

  For example, in the above-described embodiment, the case where the flame current detection device of the present invention is applied to a two-stage combustion type combustion device is shown, but the present invention can also be applied to a normal combustion type combustion device.

It is a circuit diagram which shows schematic structure of the flame current detection apparatus which concerns on this invention. It is explanatory drawing which shows the relationship between the dispersion | variation in the alternating voltage in the flame current detection apparatus, and the read current of a control means. It is a circuit diagram which shows 2nd Embodiment of the same flame current detection apparatus. It is a block diagram which shows schematic structure of the combustion apparatus to which the flame current detection apparatus which concerns on this invention is applied. It is explanatory sectional drawing which shows schematic structure of the burner in the combustion apparatus. It is explanatory drawing which shows the relationship between the read current value of the control means in a 1st flame current detection apparatus, the read current value of the control means in a 2nd flame current detection apparatus, and the quantity of carbon monoxide. It is a circuit diagram which shows schematic structure of the flame current detection apparatus modified so that the electric current value of flame current could be read.

Explanation of symbols

1 Ground electrode (burner)
2 Frame rod (electrode)
3 AC power supply 4-7 capacitor 8 diode 9 operational amplifier 10 DC power supply 11-14 resistor 15 resistance (equivalent circuit of flame)
16 Diode (equivalent circuit of flame)
17 Control means 18 Resistor (pseudo flame circuit)
19 Diode (pseudo flame circuit)
20 Switch means 21 Two-stage combustion burner 22 Primary flame 23 Secondary flame 24 Gas supply chamber 25 Mixture supply port 26 Secondary air supply port 100 Controller 101a First flame current detection device 101b Second flame current detection device A Pseudo flame circuit B Equivalent circuit of flame

Claims (5)

Flame current provided with a burner, an electrode to be exposed to the flame of the burner, and current detection means for detecting flame current generated by applying an AC voltage between the burner and the electrode by converting the current into voltage data In the detection device,
In parallel with the burner and the electrode, there is provided a pseudo flame circuit that constantly flows a pseudo flame current, and a standard pseudo flame current value that flows through the pseudo flame circuit when a standard voltage is applied as the AC voltage is stored in advance. A standard simulated flame current storage means
The control means calculates the actual flame current based on the detected current value of the current detecting means when the burner is burned and when not burned, and the standard simulated flame current value stored in the standard simulated flame current storage means. A flame current detection device characterized by calculating. 2. The flame current detection apparatus according to claim 1, wherein the actual flame current is calculated by the control means according to the following approximate expression.
(Actual flame current) ≒ (standard simulated flame current value / current value detected during non-combustion) x (current value detected during combustion-current value detected during non-combustion) Switch means capable of turning on / off the application state of the AC voltage;
A failure that determines whether or not a circuit component has failed in the flame current detection device based on a change state of an output signal of the current detection means when the application state of the AC voltage is switched by the switch means when the burner is not burned. The flame current detection device according to claim 1, further comprising a determination unit. Insulation deterioration determination means for determining an insulation deterioration state between the burner and the electrode based on a comparison result between a detected current value of the burner during non-burning and a reference current value stored in advance during non-burning. Prepared,
When it is determined that the insulation deterioration is caused by the insulation deterioration determining means, at least one of notifying the fact in the predetermined notifying means or changing the voltage data threshold value of the flame detection current in the control means is executed. The flame current detection device according to any one of claims 1 to 3, wherein A combustion apparatus in which the flame current detection device according to any one of claims 1 to 4 is mounted,
In a combustion apparatus in which a mixture of primary air and fuel gas in an oxygen-deficient state undergoes primary combustion, and further receives secondary air supply to perform secondary combustion.
A first ion current detection member is provided in the primary combustion flame, a secondary air supply port for supplying secondary air to the base of the primary combustion flame is provided, and a second ion is provided in the vicinity of the secondary air supply port. Provide a current detection member,
The first ion current detection member is configured as the electrode of the first flame current detection device, and the second ion current detection member is configured as the electrode of the second flame current detection device,
A combustion apparatus that controls at least one of supplied air and fuel gas based on a flame current value calculated in each of the first and second flame current detectors.

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