JP6383310B2 - Combustion control device and combustion system - Google Patents

Description

  The present invention relates to a combustion control device and a combustion system, and more particularly to a combustion control device capable of performing safety control of combustion with high accuracy.

In general, in the operation control system of a combustion furnace, combustion is performed while monitoring the flame of the burner provided in the combustion furnace, the temperature in the furnace, the pressure of combustion air, the pressure of fuel supplied to the burner, etc. The safety of combustion is ensured by performing the control. Specifically, the combustion controller only reflects the state of gas pressure, air pressure, etc. related to the safe operation of the combustion furnace in the state of the abnormality detection element, and only when the state of the abnormality detection element indicates normal (See, for example, Patent Document 1).
Here, the abnormality detecting element has a structure that takes either a short circuit or an open state between two contacts according to the state of a monitoring target, and is generally called an interlock or a limit, for example. It is what. As the interlock, for example, an air pressure lower limit interlock for monitoring the presence / absence of supply of combustion air, a gas pressure upper limit interlock and a gas pressure lower limit interlock for monitoring the fuel supply state, and the like are known.

  A general interlock includes a switch provided between two contact points, and has a structure in which the switch is turned on and off by an output of a sensor. When such a interlock is normal, the two contacts are short-circuited when the switch is turned on, and when the monitored object is abnormal, the two contacts are turned off. It is controlled so that there is a gap between them.

  In a conventional combustion control device, for example, as disclosed in Non-Patent Document 1, a pulse signal is input to one contact of an interlock having the above structure, and the pulse signal is output from the other contact of the interlock. Whether or not the interlock is open and short-circuited is determined depending on whether or not it is performed.

JP 2010-286128 A

“Development of a controller using combustion safety control technology”, Yuichi Kumazawa, azbil Technical Review, January 2011 issue, Azbil Corporation.

  By the way, in the combustion system, when an abnormality occurs in the operation control system of the combustion furnace, it is necessary to quickly stop the combustion operation to ensure safety, while when the operation control system of the combustion furnace is normal It is necessary to realize a stable combustion operation. Therefore, rapidity and high accuracy are required for detecting an abnormality related to an interlock or the like for safety control. For example, an abnormality that directly leads to a serious accident such as an explosion in a combustion furnace, such as an abnormality in a monitoring target (such as gas pressure or air pressure) due to an interlock, is required to be detected quickly. For a circuit failure or the like, high detection accuracy is required to prevent the combustion operation from being stopped due to erroneous detection.

However, the conventional interlock determination method described above merely determines the input of an interlock based on the presence or absence of a pulse signal input to the combustion control device via the interlock. Since it is not possible to distinguish between the presence and absence of a circuit failure, it may be sufficient regarding the speed of determination of the monitoring target, but it is difficult to say that the accuracy of the determination is sufficient.
For example, in a combustion system equipped with a large combustion furnace such as a steel furnace in a plant or the like, the wiring connecting each interlock and the combustion control device may reach several hundred meters, and the parasitic impedance of the wiring Due to the increase in the components, it is easily affected by strong noise from a power source, an inverter, or the like close to the wiring. In addition, since a plurality of the wirings are often bundled and laid, if a pulse signal propagates to one wiring, the pulse signal may be guided to another wiring, which may become a noise component. When such noise propagates to the wiring, it is difficult to say that the conventional interlock determination method can provide sufficient determination accuracy.

  An object of the present invention is to improve the determination accuracy of an abnormality detection element such as an interlock in combustion control.

The combustion control device (1, 10) according to the present invention has two contacts at one of the contact points of the abnormality detection element (6-9) that take either a short circuit or an open state between the two contacts depending on the state of the monitoring target. The output circuit (102) for supplying the output signal (VOUT) of the value and the signal output from the other contact of the abnormality detecting element to which the output signal is supplied are input, and 2 according to the logic level of the input signal The input circuit (103_1 to 103_n) that generates the input signals (DIN_1 to DIN_n) of the value and the input signal are sampled and output in the first period (T1) in which the output signal is at the first logic level (H). The sampling unit (105) that samples the input signal within the second period (T2) in which the signal becomes the second logic level (L), and the sampling unit based on the sampling result of the first period by the sampling unit An abnormality detection element state determination unit (1061) that determines the state of the monitoring target by the normal detection element, and a circuit failure determination unit that determines whether there is a failure in the output circuit and the input circuit based on the sampling result of the second period by the sampling unit (1062), and the abnormality detection element state determination unit refers to the sampling value of the first period for N consecutive times (N is an integer of 2 or more), so that the signal (VIN_1 to VIN_1) input to the input circuit VIN_n), when it is detected that the logic level in the first period is the first logic level N times consecutively, it is determined that the monitoring target by the abnormality detecting element is normal, and the signal input to the input circuit It rukoto be determined logic level in the first period when it is detected that a second logic level N times in a row, is abnormal monitored by the abnormality detection device And features.

  In the above combustion control device, the circuit failure determination unit refers to the sampling value of the second period of M (M is an integer of 2 or more) consecutive times, thereby determining the logic of the signal input to the input circuit in the second period. If it is detected that the level is the second logic level continuously M times, it may be determined that at least one of the output circuit and the input circuit has failed.

  In the combustion control device, M ≧ N may be satisfied. Note that M and N are arbitrary.

  In the combustion control device, the sampling unit may perform sampling in the first period after the first time (Td1) has elapsed since the output signal has switched from the second logic level to the first logic level.

  In the combustion control apparatus, the sampling unit may perform sampling in the second period after the second time (Td2) has elapsed since the output signal has switched from the first logic level to the second logic level.

  In the combustion control apparatus, the first time may be equal to or shorter than the second time. Note that the first time and the second time are arbitrary.

  The combustion control device includes a plurality of sets of functional blocks (110) each including a sampling unit, an abnormality detection element state determination unit, and a circuit determination unit, and each functional block includes a plurality of different program processing devices (101a, 101b). May be configured separately.

  The combustion control apparatus may further include a control unit (11) that controls the operation of the burner (43) based on the determination results of the abnormality detection element state determination unit and the circuit failure determination unit.

  A combustion system (500) according to the present invention includes the combustion control device (1) and the burner provided in the combustion chamber (40) and controlled by the combustion control device.

  In the above description, as an example, constituent elements on the drawing corresponding to the constituent elements of the invention are represented by reference numerals with parentheses.

  As described above, according to the present invention, it is possible to improve the determination accuracy of an abnormality detection element such as an interlock in combustion control.

FIG. 1 is a diagram illustrating a configuration of a combustion system including a combustion control device according to an embodiment. FIG. 2 is a diagram illustrating a configuration of the safety control device in the combustion control device according to the embodiment. FIG. 3 is a timing chart for explaining the determination processing related to the interlock by the combustion control apparatus according to the embodiment. FIG. 4 is a flowchart showing a flow of determination processing related to interlock by the combustion control device according to the embodiment. FIG. 5 is a flowchart showing a flow of interlock input determination processing by the combustion control device according to the embodiment. FIG. 6 is a flowchart showing the flow of circuit failure determination processing by the combustion control apparatus according to the embodiment. FIG. 7 is a diagram illustrating a configuration example when the safety control device in the combustion control device according to the embodiment is realized by a plurality of microcontrollers.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Combustion system configuration>
FIG. 1 is a diagram illustrating a configuration of a combustion system including a combustion control device according to the present embodiment.
A combustion system 500 shown in the figure is a system in which a combustion chamber is burned by a burner. Examples of the combustion system 500 include small industrial combustion furnaces such as deodorizing furnaces and heating furnaces, and large industrial combustion furnaces such as steel furnaces in plants and the like.
Specifically, the combustion system 500 includes a combustion device 4, a fuel flow path 2, an air flow path 3, a controller 5, an excessive temperature rise limit 6 and interlocks 7 to 9 as abnormality detection elements, and combustion control. The apparatus 1 is provided.

  The combustion device 4 includes temperature sensors 41 and 42, a main burner 43, a pilot burner 44, a flame detector 45, and an ignition device (igniter) 46. The main burner 43 is disposed in the combustion chamber 40 and heats the combustion chamber 40. The pilot burner 44 is a burner for igniting the main burner 43. The ignition device (IG) 46 is a device for igniting the burner. The ignition device (IG) 46 includes, for example, an ignition transformer and an electrode rod, and generates a high-voltage spark by the ignition transformer, thereby allowing the pilot burner 44 to pass through the electrode rod. Ignite. The flame detector 45 is a device that detects the presence or absence of a flame by the main burner 43. The temperature sensor 41 is a sensor that detects the temperature in the combustion chamber 40, and the temperature measurement value by the sensor is used for temperature control in the combustion chamber 40. The temperature sensor 42 is a sensor that detects the temperature in the combustion chamber 40, and the temperature measurement value by the sensor is used to detect an abnormally high temperature state in the combustion chamber 40.

  The fuel flow path 2 is a flow path for supplying fuel to the combustion device 4. The fuel flow path 2 includes a main flow path 2a to which fuel is supplied from the outside, and a first flow path 2b and a second flow path 2c branched from the main flow path 2a. The first flow path 2 b is connected to the main burner 43, and the second flow path 2 c is connected to the pilot burner 44. As a result, the fuel supplied to the main flow path 2 a is sent to the main burner 43 and the pilot burner 44. In addition, safety shut-off valves 21 and 22 are provided in the first flow path 2b, and safety shut-off valves 23 and 24 are provided in the second flow path 2c. The safety shut-off valves 21 to 24 are controlled to be opened and closed by the burner controller 11, for example.

  The air flow path 3 has one end connected to the blower 31 and the other end connected to the first flow path 2b. The air (air) discharged from the blower 31 is fuel (gas) via the first flow path 2b. At the same time, it is supplied to the main burner 43.

  The controller 5 is a temperature indicating controller (TIC) and generates a control signal for the combustion control device 1 based on the temperature measurement value of the temperature sensor 41 so that the temperature of the combustion chamber 40 becomes a target temperature. To do.

  The overheat limit 6 is an overheat preventer for detecting an abnormally high temperature in the combustion chamber 40. The excessive temperature rise limit 6 determines whether or not the temperature measurement value by the two contacts, the switch 60 disposed between the contacts, and the temperature sensor 42 exceeds a preset temperature set in advance. The switch driving unit 61 controls the on / off of the switch 60 accordingly. For example, the switch driving unit 61 turns on the switch 60 when the temperature measured value by the temperature sensor 42 exceeds the set temperature, and turns off the switch 60 when the temperature measured value by the temperature sensor 42 does not exceed the set temperature.

  An interlock (air pressure switch) 7 is provided in the air flow path 3 and detects whether or not the pressure of the air supplied to the air flow path 3 exceeds a set pressure value. It is. Specifically, the interlock 7 has two contacts, a switch 70 disposed between the contacts, and whether the air pressure in the air flow path 3 detected by the sensor exceeds a preset pressure value. And a switch driving unit 71 that controls whether the switch 70 is turned on or off according to the determination result. For example, the switch driving unit 71 turns on the switch 70 when the air pressure in the air flow path 3 exceeds the set pressure value, and switches 70 when the air pressure in the air flow path 3 does not exceed the set pressure value. Turn off.

  An interlock (gas pressure switch) 8 is provided in the main flow path 2a, and detects whether or not the pressure of the fuel (gas) supplied to the main flow path 2a exceeds a preset lower limit pressure value. It is an interlock. Specifically, the interlock 8 determines whether or not the gas pressure in the main flow path 2a detected by the two contacts, the switch 80 disposed between the contacts, and the sensor exceeds a lower limit pressure value. The switch driving unit 81 controls the on / off of the switch 80 according to the determination result. For example, the switch drive unit 81 turns on the switch 80 when the gas pressure in the main flow path 2a exceeds the lower limit pressure value, and turns off the switch 80 when the gas pressure in the main flow path 2a does not exceed the lower limit pressure value. To do.

  An interlock (gas pressure switch) 9 is provided in the first flow path 2b and detects whether or not the pressure of the fuel (gas) supplied to the main burner 43 exceeds a preset upper limit pressure value. Gas pressure upper limit interlock. Specifically, the interlock 9 includes two contacts, a switch 90 disposed between the contacts, and whether or not the gas pressure in the first flow path 2b detected by the sensor exceeds the upper limit pressure value. And a switch drive unit 91 for controlling on / off of the switch 90 according to the determination result. For example, the switch drive unit 91 turns on the switch 90 when the gas pressure in the first flow path 2b does not exceed the upper limit pressure value, and the gas pressure in the first flow path 2b exceeds the upper limit pressure value. In this case, the switch 90 is turned off.

  In the following description, the interlocks 7 to 9 and the overheating limit 6 as the abnormality detection elements having a structure in which the short circuit and the open circuit between the two contacts are controlled according to the state of the monitoring target are collectively referred to as “ Sometimes referred to as “limit interlock”.

<Combustion control system configuration>
The combustion control device 1 is a device for safely controlling combustion by a burner in the combustion chamber 40. As shown in FIG. 1, the combustion control device 1 includes a burner controller 11 and a safety control device 10.

  The burner controller 11 is a device that controls the combustion in the combustion chamber 40 by controlling the operation of the burners (the main burner 43 and the pilot burner 44). Specifically, the burner controller 11 is based on an instruction (notification signal 14) from the safety control device 10 described later, a control signal from the controller 5, and a flame detection signal from the flame detector 45. The main burner 43 is ignited in accordance with the set ignition sequence by controlling the opening / closing of 24 and the activation of the ignition device 46.

  FIG. 1 illustrates the case where the combustion system 500 includes one main burner 44, but when the combustion system includes a plurality of main burners, the corresponding main burner is controlled. A plurality of burner controllers may be provided for each main burner, and these burner controllers may be controlled by a single safety control device 10.

  The safety control device 10 is a device that monitors the state of each limit / interlock and determines whether the operation of the burner is permitted or not in order to prevent safe operation of the combustion system 500, that is, explosion of the combustion system 500, and the like. is there. Specifically, the safety control device 10 generates a notification signal 14 indicating permission / non-permission of burner operation according to the contact state (open or short circuit) in the interlocks 7 to 9 and the overheat limit 6. Then, by giving to the burner controller 11, permission and non-permission of the operation of the burner (supply and stop of fuel to each burner, etc.) are instructed.

  The safety control device 10 corresponds to the limit / interlock module for monitoring the limit / interlock manufactured based on the general safety rules of industrial combustion furnaces (for example, JIS B 8415), and the safety general rule. A programmable logic controller (so-called safety PLC) in which dedicated software is set can be exemplified.

The safety control device 10 applies a pulse signal to one contact of each limit interlock and determines the logic level of the signal output from the other contact of each limit interlock, thereby determining each limit interlock. Determine the lock status.
Specifically, the safety control device 10 is an interlock input that determines the state of each limit / interlock based on the logic level of the input signal from each limit / interlock during a period in which the pulse signal is at the first logic level. Judgment processing is performed. In addition, the safety control device 10 is a circuit that determines a failure of the output circuit 102 and the input circuit 103, which will be described later, based on the logic level of the input signal from each limit interlock during the period in which the pulse signal is at the second logic level. Perform failure determination processing.
Hereinafter, the configuration and operation of the safety control device 10 will be described in detail.
In the present specification, as an example, the first logic level is described as “high (H) level” and the second logic level is described as “low (L) level”.

<Configuration of safety control device>
FIG. 2 is a diagram illustrating a configuration of the safety control device 10 in the combustion control device 1 according to the embodiment.
As shown in FIG. 2, the safety control device 10 includes a plurality of external terminals, a microcontroller (MCU) 101, an output circuit 102, and n (n is an integer of 1 or more) input circuits 103_1 to 103_n. It is composed of In FIG. 2, only the terminals COM and IN_1 to IN_n related to limit / interlock state monitoring are illustrated as the plurality of external terminals.

  The terminal COM is an external terminal for outputting an output signal VOUT, which will be described later, and is commonly connected to one end (one contact) of the switches constituting each limit / interlock. For example, as shown in FIG. 2, the terminal COM is connected to the one contact a of the switch 70 in the interlock 7, the one contact a of the switch 80 in the interlock 8, and the switch 90 in the interlock 9 by the wiring 12. Are connected to one of the contacts a. Although not shown, the terminal COM is also connected to one contact of the switch 60 in the overheating limit 6.

  Terminals IN_1 to IN_n are provided corresponding to each limit / interlock and are external terminals for inputting signals from the corresponding limit / interlock. For example, as shown in FIG. 2, the terminal IN_1 is connected to the other contact b of the switch 70 in the interlock 7 by the wiring 13_1, and the terminal IN_2 is connected to the other contact b of the switch 80 in the interlock 8 by the wiring 13_2. The terminal IN_n is connected to the other contact b of the switch 90 in the interlock 9 by the wiring 13_n. Although not shown, the other contact of the switch 60 in the overheating limit 6 is also connected to the corresponding input terminal.

  The output circuit 102 is a circuit that generates a binary output signal VOUT to be supplied to each limit interlock. Specifically, the output circuit 102 generates a binary output signal VOUT that is synchronized with a reference pulse signal PS generated by a pulse generation unit 104 to be described later, and outputs it to the terminal COM.

  Specifically, as shown in FIG. 2, for example, the output circuit 102 includes a buffer circuit BF, a photocoupler PC1, a resistor R1, and a PNP transistor Q1. The output circuit 102 electrically insulates between the external terminal COM and the MCU 101, and outputs, for example, a 0-3.3V (or 5.0V) pulse signal output from the MCU 101 to a binary value of, for example, 0V-24V. Is output to the terminal COM. For example, when the reference pulse signal PS output from the MCU 101 is H (for example, 3.3V), the transistor Q1 is turned on to output the + 24V output signal VOUT, and the reference pulse signal PS output from the MCU 101 is L When it is (for example, 0 V), the transistor Q1 is turned off. In this case, if the limit / interlock contact of the connection destination is short-circuited, the output signal VOUT becomes 0V by pull-down resistors R3 and R4 of the input circuit 103 described later. On the other hand, when the limit / interlock contact of the connection destination is open, the terminal COM becomes high impedance.

  The input circuits 103_1 to 103_n are provided corresponding to each limit / interlock. The input circuits 103_1 to 103_n (referred to as “input circuit 103” when generically named) correspond to the corresponding terminals IN_1 to IN_n (referred to as “terminal IN” when generically named) from the corresponding limit interlocks. 2) input signals DIN_1 to DIN_n corresponding to the logic level of the input signal VIN. The signals VIN_1 to VIN_n (collectively referred to as “signal VIN”) are input. (When collectively referred to as “input signal DIN”). For example, in FIG. 2, the signal VIN_1 output from the other contact b of the switch 70 in the interlock 7 is input via the terminal IN_1, and the other contact b of the switch 80 in the interlock 8. An input circuit 103_2 to which the output signal VIN_2 is input via the terminal IN_2; an input circuit 103_n to which the signal VIN_n output from the other contact b of the switch 90 in the interlock 9 is input via the terminal IN_n; Is shown. Although not shown, a signal output from the other contact of the switch 60 of the overheating limit 6 is also input to the corresponding input circuit.

  Specifically, the input circuit 103 includes resistors R2 to R4 and a photocoupler PC2 as shown in FIG. 2, for example. The input circuit 103 electrically insulates between the corresponding terminal IN and the MCU 101 and outputs a binary signal of, for example, 0V-24V input to the corresponding terminal IN, for example, 0-3.3V (or 5 .0V) and is input to the MCU 101. Here, the resistance values of the resistors R3 and R4 are the photodiodes on the primary side of the photocoupler PC2 when the output signal VOUT of H level (for example, 24V) is output in a state where the contacts of the limit interlocks are short-circuited. Has been adjusted to turn on.

  The MCU 101 includes, for example, a processor such as a CPU, various memories, and other peripheral circuits. The MCU 101 functions as a pulse generation unit 104, a sampling unit 105, a determination unit 106, and a notification unit 107 when the processor executes data processing according to a program stored in the memory.

  The pulse generation unit 104 is a functional unit that generates a reference pulse signal PS used for monitoring the states of the interlocks 7 to 9 and the excessive temperature rise limit 6. Specifically, the pulse generation unit 104 is a functional unit that generates a reference pulse signal PS having a predetermined period and duty ratio by dividing a reference clock signal generated by a clock generator such as a crystal oscillator. The reference pulse signal PS is, for example, a binary signal of 0V-3.3V (5.0V) generated based on the power supply voltage (for example, 3.3V or 5.0V) of the MCU 101.

  The sampling unit 105 is a functional unit that samples the input signals DIN_1 to DIN_n generated by the input circuits 103_1 to 103_n. The sampling unit 105 performs sampling processing in synchronization with the reference clock signal generated by the pulse generation unit 104. Specifically, the sampling unit 105 samples the input signal DIN during the period T1 in which the output signal VOUT (the reference pulse signal PS) is the first logic level (H level), and outputs the output signal VOUT (the reference pulse). The input signal DIN is sampled during a period T2 in which the signal PS) is at the second logic level (L level). Note that the sampling for the input signals DIN_1 to DIN_n may be performed by the sampling unit 105 in a time division manner, or a plurality of input signals may be sampled simultaneously.

  The determination unit 106 includes an interlock input determination unit 1061 as an abnormality detection element state determination unit that determines whether each limit / interlock is abnormal based on the sampling result of the period T1 by the sampling unit 105. Further, the determination unit 106 includes a circuit failure determination unit 1062 that determines whether or not the output circuit 102 and the input circuit 103 are defective based on the sampling result of the period T2 by the sampling unit 105.

The notification unit 107 generates a notification signal 14 indicating permission and non-permission of the burner operation described above based on the determination result by the determination unit 106.
For example, when the interlock input determination unit 1061 determines that the limit / interlock is “normal”, the notification signal 14 indicating “permitted” for the burner operation is generated. If the circuit failure determination unit 1062 determines “no circuit failure”, the notification signal 14 indicating “permitted” for burner operation is generated. On the other hand, when the interlock input determination unit 1061 determines that the limit / interlock is “abnormal”, the notification signal 14 indicating “non-permission” of the burner operation is generated. When the circuit failure determination unit 1062 determines that “circuit failure is present”, the notification signal 14 indicating “not permitted” for burner operation is generated.

<Operation of safety control device>
Next, determination processing (interlock input determination processing and circuit failure determination processing) related to interlock by the combustion control device 1 will be specifically described.
In the combustion control device 1 according to the present embodiment, the same determination process is performed for each limit / interlock. Therefore, in the following description, the determination process related to the interlock 7 will be representatively described. A description of other determination processes related to limit / interlock will be omitted.

  FIG. 3 is a timing chart for explaining the determination processing related to the interlock by the combustion control apparatus according to the embodiment. 3 shows the voltage at the terminal COM (output signal VOUT), and the second stage from the top shows the contact state (short circuit or open) in the interlock 7. The third stage shows the voltage of the terminal IN_1 (the signal VIN_1 inputted to the input circuit 103_1), and the lowermost stage in the figure shows the input signal DIN generated by the input circuit 103_1.

  The waveform in the second stage from the top in the figure indicates that the switch 70 is turned on and the contacts a and b of the interlock 7 are short-circuited when the level is high. Indicates that the switch 70 is turned off and the contacts a and b of the interlock 7 are open.

As shown in FIG. 3, when the pulse generator 104 generates a reference pulse signal PS having a constant period TC, an output signal VOUT synchronized with the reference pulse signal PS is output from the terminal COM. Here, it is assumed that the logical levels of the reference pulse signal PS and the output signal VOUT are the same.
When the output signal VOUT is output from the terminal COM, if the switch 70 of the interlock 7 is ON (contact is short-circuited), the output signal VOUT is input to the input circuit 103_1 via the switch 70. In this case, for example, as shown in a period from time t0 to t1 in FIG. 3, a signal VIN_1 synchronized with the output signal VOUT is input to the terminal IN_1, and an input signal having a logic opposite to the output signal VOUT is input by the input circuit 103_1. DIN_1 is generated.

  On the other hand, when the output signal VOUT is output from the terminal COM, if the contact of the interlock 7 is open (the switch 70 is off), the output signal VOUT is not input to the input circuit 103_1. At this time, since the terminal IN_1 is pulled down to the ground voltage (0V) by the resistors R3 and R4, the voltage of the terminal IN_1 (signal VIN_1) becomes “0V” and the input signal DIN_1 becomes “H” level. For example, as shown in the period from time t1 to time t2 in FIG. 3, when the contact of the interlock 7 is open, the input signal DIN_1 is at the “H” level regardless of the logic level of the output signal VOUT. It becomes.

  Further, when the contact of the interlock 7 is short-circuited, for example, when the transistor Q1 of the output circuit 102 has a power fault or when the secondary side phototransistor of the photocoupler PC2 of the input circuit 103_1 has a ground fault. The input signal DIN_1 is fixed to “L level”. For example, FIG. 3 shows a case where the secondary side phototransistor of the photocoupler PC2 of the input circuit 103_1 at the time t3 has a ground fault, and the input signal DIN_1 after the time t3 is fixed at the L level. .

Next, sampling processing by the sampling unit 105 will be described.
The sampling unit 105 samples the input signal DIN_1 during the period T1 in which the output voltage VOUT (reference clock signal) is “H level”. For example, as shown in FIG. 3, the input signal DIN_1 is sampled at the sampling timing SI1 in the first period T1 (sampling value: L), and the input signal DIN_1 is sampled at the sampling timing SI2 in the second period T1 (sampling). Value: L),..., And so on, input signal DIN_1 in each period T1 is sampled.

  The sampling unit 105 samples the input signal DIN_1 during the period T2 when the output voltage VOUT (reference clock signal) is “L level”. For example, as shown in FIG. 3, the input signal DIN_1 is sampled at the sampling timing SC1 in the first period T2 (sampling value: H), and the input signal DIN_1 is sampled at the sampling timing SC2 in the second period T2 (sampling). Value: H),..., And sampling the input signal DIN_1 in each period T2.

  The sampling by the sampling unit 105 described above is preferably performed after a predetermined time has elapsed since the logic level of the output voltage VOUT (reference clock signal) is switched. For example, as shown in FIG. 3, the sampling in the period T1 is performed in the period Ts1 after a predetermined time td1 has elapsed since the output voltage VOUT (reference clock signal) was switched from “L level” to “H level”. It is desirable. The sampling in the period T2 is desirably performed in the period Ts2 after a predetermined time td2 has elapsed since the output voltage VOUT (reference clock signal) is switched from the “H level” to the “L level”. For example, a delay circuit (such as a CR circuit or a multistage logic circuit) that sends and outputs the output voltage VOUT or a reference clock signal is provided, and the sampling unit 105 performs sampling processing using the signal output from the delay circuit as a start signal Just start. Alternatively, a timer that outputs a signal when the logic of the output voltage VOUT or the reference clock signal is switched as a trigger and outputs the signal when the time is counted up to a predetermined time is provided, and the sampling unit 105 uses the signal output from the timer as an activation signal. The sampling process may be started.

  According to this, as described above, the voltage of the input signal DIN is stable even when the wirings 12 and 13 connecting the safety control device 1 and each limit / interlock are long and the parasitic impedance component is large. Since sampling can be performed after this, a decrease in accuracy in determination relating to the interlock can be suppressed.

  The waiting times Td1 and Td2 from when the logic level of the output signal VOUT is switched to when sampling is started are appropriately determined in consideration of the transition time until the signal due to the parasitic impedance component of the wirings 12 and 13 is stabilized. You only have to set it. For example, by setting Td1 <Td2, the presence or absence of an abnormality to be monitored due to interlock is detected quickly, and a circuit failure that is a permanent failure is sampled after the signal propagating through the wiring becomes more stable. Thus, determination with higher accuracy becomes possible.

  Note that sampling for one input signal DIN in the periods T1 and T2 may be performed only once in the periods T1 and T2, or may be performed a plurality of times in the periods T1 and T2.

Next, an interlock input determination process by the interlock input determination unit 1061 will be described.
When the sampling value of the input signal DIN by the sampling unit 105 in the period T1 matches N (N is an integer of 2 or more) times continuously, the interlock input determination unit 1061 performs a limit according to the matched logic level. -Determine whether the interlock monitoring target is "normal" or "abnormal".

  More specifically, the interlock input determination unit 1061 counts the number of times that the sampling values of the input signals DIN continuously match each other during the period T1, and when the counted number of matches reaches N times, The matched sampling value is set as a definite value of the logic level of the input signal DIN. For example, in FIG. 3, when the sampling values of the input signal DIN_1 at N consecutive sampling timings SI1 to SIN coincide with each other at “L level”, the logic level of the input signal DIN_1 is determined to be “L”. When the sampling values of the input signal DIN_1 at N consecutive sampling timings SI1 to SIN coincide with each other at “H level”, the logic level of the input signal DIN_1 is determined to be “H”. When the determined value is “H level”, the interlock input determination unit 1061 “opens” both the limit and interlock contacts corresponding to the input signal DIN, that is, corresponds to the input signal DIN. The limit / interlock to be monitored is determined to be “abnormal”. On the other hand, when the determined value is “L level”, the interlock input determination unit 1061 corresponds to the input signal DIN, that is, both the limit / interlock contacts corresponding to the input signal DIN are “short-circuited”. The limit / interlock to be monitored is determined to be “normal”.

Next, circuit failure determination processing by the circuit failure determination unit 1062 will be described.
The circuit failure determination unit 1062 receives at least one of the input circuit 103 and the output circuit 102 when the sampling value of the input signal DIN in the period T2 continuously becomes “L level” M (M is an integer of 2 or more) times. Is determined to be “failed”. More specifically, the circuit failure determination unit 1062 counts the number of times that the sampling value of the input signal DIN continuously becomes “L level” in the period T2, and when the number of times becomes “M”, the input circuit 103 It is determined that at least one of the output circuits 102 is “failed”.

  For example, as shown in FIG. 3, when a ground fault on the secondary side of the photocoupler PC2 of the input circuit 103_1 occurs at time t3, the subsequent input signal DIN_1 is fixed to “L level” regardless of the signal VIN_1. Is done. In this case, the circuit failure determination unit 1062 receives the input circuit 103 when the number of times that the sampling value of the input signal DIN continuously becomes “L level” in the period T2 after time t3 becomes “M”. It is determined that at least one of the output circuits 102 is “failed”.

  The number N of sampling value matches used for the interlock input determination process and the number M match of the sampling values used for the circuit failure determination process are the type of combustion system to which the combustion control device 1 is applied, the required safety level, etc. It is possible to adjust according to. For example, by setting N <M, it is possible to quickly detect the presence or absence of an abnormality to be monitored by interlock, and for a circuit failure that is a permanent failure, the combustion operation does not stop frequently due to false detection due to noise or the like. It becomes possible to.

Next, the flow of determination processing related to interlock by the combustion control device will be described.
FIG. 4 is a flowchart showing a flow of determination processing related to interlock by the combustion control device according to the embodiment.
As described above, the determination process related to the interlock by the combustion control device 1 includes the determination process based on the sampling value in the period T1 (interlock input determination process) and the determination process based on the sampling value in the period T2 (circuit failure determination process). ) And
As shown in FIG. 4, when the interlock control determination process by the combustion control device 1 is started, first, the pulse generator 104 generates the reference pulse signal PS, and the output circuit 102 synchronizes with the reference pulse signal PS. The output signal VOUT thus generated is generated (S1). Here, the timing at which the determination process regarding the interlock is executed is set for each limit / interlock. For example, some limit / interlock determination processes are always performed after the combustion system 500 is started, and other limit / interlock determination processes are performed at a preset timing after the combustion system 500 is started. Done.

  Next, the sampling unit 105 starts sampling the input signals DIN_1 to DIN_n (S2). When sampling by the sampling unit 105 is started, the interlock input determination unit 1061 starts determination processing based on the sampling value of the period T1, that is, interlock input determination processing (S3). Further, the circuit failure determination unit 1062 starts determination processing based on the sampling value in the period T2, that is, circuit failure determination processing (S4). When each determination process of steps S3 and S4 is executed, a notification signal 14 indicating whether the burner is permitted or not is output to the burner controller 11.

  Note that the determination process based on the sampling value in the period T2 in step S4 may be executed after the determination process based on the sampling value in the period T1 in step S3 as shown in FIG. The determination process based on the sampling value in the period T1 in step S3 may be executed in parallel.

Hereinafter, each flow of the interlock input determination process in step S3 and the circuit failure determination process in step S4 will be described in detail.
First, the flow of the interlock input determination process in step S3 will be described.
FIG. 5 is a flowchart showing a flow of interlock input determination processing by the combustion control device according to the embodiment.

  As shown in FIG. 5, when sampling is started in step S2, the interlock input determination unit 1061 counts the number of times that the sampling values in the period T1 continuously match (S31). After the start of the count, the interlock input determination unit 1061 determines whether or not the sampling values by the sampling unit 105 in the period T1 are matched N times consecutively (S32). Here, when there is no coincidence N times consecutively, the interlock input determination unit 1061 continues to count the number of coincidence of sampling values in the period T1 by the sampling unit 105. If N consecutive matches do not occur due to noise or the like, the fixed value may be controlled to be “H (open)” after a predetermined time has elapsed.

  On the other hand, in step S32, when the sampling values by the sampling unit 105 in the period T1 match N times consecutively, the interlock input determination unit 1061 determines whether or not the sampling value is “L”. (S33).

  In step S33, when the sampling value in the period T1 that coincides N times consecutively is “H”, the interlock input determination unit 1061 determines that the limit / interlock contact corresponding to the sampled input signal DIN is present. It is determined that it is “open”, and it is determined that the monitoring target of the limit / interlock is “abnormal” (S36). Thereby, the notification part 107 outputs the notification signal 14 which shows "non-permission" of a burner operation to the burner controller 11 based on the determination result of the interlock input determination part 1061 (S37).

  On the other hand, in step S33, when the sampling value in the period T1 that coincided N times consecutively is “L”, the interlock input determination unit 1061 determines the limit / interlock corresponding to the sampled input signal DIN. It is determined that the contact is “short-circuited”, and it is determined that the limit / interlock monitoring target is “normal” (S34). Thereby, the notification part 107 outputs the notification signal 14 which shows "permission" of a burner operation to the burner controller 11 based on the determination result of the interlock input determination part 1061 (S35).

Next, the flow of the circuit failure determination process in step S4 will be described in detail.
FIG. 6 is a flowchart showing the flow of circuit failure determination processing by the combustion control apparatus according to the embodiment.
When sampling by the sampling unit 105 is started in step S2, the circuit failure determination unit 1062 counts the number of times that the sampling value in the period T2 is continuously “L” (S41). At this time, when the sampling value in the period T2 becomes “H”, the circuit failure determination unit 1062 resets the count value and restarts the count operation.

  After the start of the count, the circuit failure determination unit 1062 determines whether or not the number of times that the sampling value in the period T2 continuously becomes “L” exceeds M times (S42).

  In step S42, when the number of times that the sampling value in the period T2 continuously becomes “L” exceeds M times, the circuit failure determination unit 1062 determines that “circuit failure is present” (S43). As a result, the notification unit 107 outputs a notification signal 14 indicating “non-permission” of the burner operation to the burner controller 11 based on the determination result of the circuit failure determination unit 1062 (S44).

  On the other hand, when the number of times that the sampling value continuously becomes “L” in the period T2 does not exceed M times in step S42, the circuit failure determination unit 1062 determines that “no circuit failure” (S45). . In this case, the process returns to step S41 again, and the count operation is repeated as many times as the sampling value in the sampling period T2 becomes “L”.

<Effects of combustion control device>
As described above, according to the combustion control apparatus of the present invention, the interlock input determination is performed during the high level period of the output signal VOUT (pulse) supplied to each limit interlock, and the circuit failure determination is performed during the low level period of the output signal VOUT. Therefore, it is possible to distinguish between the abnormality of the monitoring target due to the interlock and the abnormality of the peripheral circuit of the interlock, and to improve the determination accuracy regarding the interlock.

  Further, according to the combustion control apparatus according to the present embodiment, when the sampling value of the input signal DIN in the high level period or the low level period of the output signal VOUT input to each limit interlock coincides continuously a plurality of times. In addition, the sampling value is set as the definite value of the input signal DIN, and the interlock input determination and the circuit failure determination are performed based on the definite value. Thereby, for example, even when noise is superimposed on signals propagating through the wirings 12 and 13, erroneous determination due to noise is less likely to occur, and a decrease in determination accuracy regarding the interlock can be suppressed.

  Further, since sampling by the sampling unit 105 is performed after a predetermined time Td1 (Td2) has elapsed since the logic level of the output voltage VOUT (reference clock signal) has been switched, as described above, the safety control device 1 and each limit Even when the parasitic impedance component of the wirings 12 and 13 connecting the interlock is large and it takes time until the signals propagating through the wirings 12 and 13 are stabilized, the voltage of the input signal DIN is stabilized. Since sampling can be performed, it is possible to suppress a decrease in determination accuracy related to the interlock.

  Further, according to the combustion control apparatus according to the present embodiment, as described above, the sampling value coincidence number M that is a criterion for circuit failure determination is determined from the sampling number coincidence number N that is a reference for interlock input determination. Is set to a larger value, and the detection sensitivity for circuit failure judgment is lower than the detection sensitivity for interlock input judgment. It is possible to control a general circuit failure so that the combustion operation does not stop frequently due to erroneous detection due to the influence of noise. That is, it is possible to improve the accuracy of circuit failure detection related to a permanent abnormality while ensuring the speed of abnormality detection by interlocking, and to improve the safety of combustion control and the stable operation.

  Further, by setting Td1 <Td2 as the standby time until sampling is started, it is possible to ensure the speed of abnormality detection by interlock and further increase the accuracy of circuit failure detection, as described above.

  From the above, the combustion control device according to the present embodiment has a large wiring 12 and 13 that connect the safety control device 1 and each limit / interlock, so that the parasitic impedance component of the wiring becomes large. It is particularly effective when applied to a combustion furnace.

  Although the invention made by the present inventors has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof. Yes.

For example, in the above embodiment, the case where the combustion control device 1 is realized by a single microcontroller has been exemplified, but it can also be realized by a plurality of microcontrollers.
FIG. 7 is a diagram illustrating a configuration example when the safety control device in the combustion control device according to the embodiment is realized by a plurality of microcontrollers.
As shown in the figure, a main microcontroller (MCU_M) 101a and a sub microcontroller (MCU_S) 101b are provided, and a sampling unit 105, a determination unit 106, and a notification unit 107 are provided in each of the microcontrollers 101a and 101b. By providing the functional blocks for limit / interlock input determination and circuit failure determination, a redundant configuration is provided.

  According to this, even if a failure occurs in one of the microcontrollers, the interlock input determination process and the circuit failure determination process can be executed by the other microcontroller. And the stability of the combustion operation can be further improved.

  In this case, the pulse generation unit 104 may be provided only in one of the microcontroller 101a and the microcontroller 101b. For example, FIG. 7 shows a case where the pulse generation unit 104 is provided in the main microcontroller 101a. In this case, the reference pulse signal PS is supplied from the main microcontroller 101a to the sub microcontroller 101b, and the sub microcontroller 101b performs sampling based on the timing of the reference pulse signal PS.

  FIG. 7 illustrates the case where two microcontrollers are provided. However, the present invention is not limited to this. Three or more microcontrollers are provided, and limit / interlock input determination and circuit failure are provided for each microcontroller. You may make it provide the functional block which performs determination.

  Moreover, in the said embodiment, as an example of the abnormality detection element (limit interlock) connected with the combustion control apparatus 1, an air pressure lower limit interlock, a gas pressure upper limit / lower limit interlock, and an excessive temperature rise limit are illustrated. However, it goes without saying that the noise determination processing by the combustion control device 1 according to the present invention can be similarly applied to the abnormality detection elements other than these.

  2 illustrates the case where the output circuit 102 and the input circuit 103 have a circuit configuration using a photocoupler, the circuit configurations of the output circuit 102 and the input circuit 103 are not limited to this. For example, when there is no need to electrically insulate between the external terminals COM, IN_1 to IN_n and the MCU 101, the output circuit 102 is connected to the transistor Q1 based on the output signal of the buffer circuit BF without passing through the photocoupler PC1. It is also possible to use a circuit configuration for driving the. Further, in the input circuit 103, a transistor is provided between the ground node and one end of the resistor R2 instead of the photocoupler PC2, and a connection node of the resistor R3 and the resistor R4 is connected to a control electrode (base electrode) of the transistor. It is good also as a structure.

  DESCRIPTION OF SYMBOLS 1 ... Combustion control apparatus, 2 ... Fuel flow path, 3 ... Air flow path, 4 ... Combustion apparatus, 5 ... Controller, 6 ... Over temperature rise limit, 7, 8, 9 ... Interlock, 10 ... Safety control apparatus, 11 DESCRIPTION OF SYMBOLS ... Burner controller, 14 ... Notification signal, 40 ... Combustion chamber, 41, 42 ... Temperature sensor, 43 ... Main burner, 44 ... Pilot burner, 45 ... Flame detector, 46 ... Ignition device (igniter), 60, 70, 80 , 90, switch, 61, 71, 81, 91 ... switch drive unit, 31 ... blower, 2a ... main channel, 2b ... first channel, 2c ... second channel, 21, 22, 23, 24 ... Safety shut-off valve, COM, IN_1, IN_n ... terminal, 12, 13, 13_1, 13_n ... wiring, 101, 101a, 101b ... microcontroller, 102 ... output circuit, 103, 103_1, 103_n ... input times , 104 ... Pulse generator, 105 ... Sampling part, 106 ... Determination part, 1061 ... Interlock input determination part, 1062 ... Circuit failure determination part, 107 ... Notification part, 110 ... Function block, PS ... Reference pulse signal, 500 ... Combustion system.

Claims (9)

An output circuit for supplying a binary output signal to one of the contacts of the abnormality detecting element that takes either a short circuit or an open state between the two contacts according to the state of the monitoring target;
An input circuit that receives a signal output from the other contact point of the abnormality detection element to which the output signal is supplied, and generates a binary input signal according to the logic level of the input signal;
A sampling unit that samples the input signal within a first period in which the output signal is at a first logic level, and that samples the input signal within a second period in which the output signal is at a second logic level;
An abnormality detection element state determination unit that determines a state of a monitoring target by the abnormality detection element based on a sampling result of the first period by the sampling unit;
A circuit failure determination unit that determines whether or not the output circuit and the input circuit have failed based on a sampling result of the second period by the sampling unit;
I have a,
The abnormality detection element state determination unit
By referring to the sampling values of the first period for N consecutive (N is an integer of 2 or more) times, the logic level in the first period of the signal input to the input circuit is continuously N times. When it is detected that the level is one logic level, it is determined that the monitoring target by the abnormality detection element is normal, and the logic level in the first period of the signal input to the input circuit is continuously N times. When the second logic level is detected, it is determined that the monitoring target by the abnormality detection element is abnormal
Combustion control device characterized by the above. The combustion control device according to claim 1,
The circuit failure determination unit is
By referring to the sampling values of the second period for M consecutive M (M is an integer of 2 or more) times, the logic level in the second period of the signal input to the input circuit is continuously M times. A combustion control apparatus characterized by determining that at least one of the output circuit and the input circuit is out of order when it is detected that the logic level is two . The combustion control device according to claim 2, wherein
A combustion control device , wherein M ≧ N. The combustion control device according to any one of claims 1 to 3 ,
The combustion control device according to claim 1, wherein the sampling unit performs sampling in the first period after a first time has elapsed since the output signal is switched from the second logic level to the first logic level . The combustion control device according to claim 4 ,
The combustion control device, wherein the sampling unit performs sampling in the second period after a second time has elapsed since the output signal is switched from the first logic level to the second logic level. The combustion control apparatus according to claim 5, wherein
The combustion control apparatus according to claim 1, wherein the first time is equal to or shorter than the second time . The combustion control device according to any one of claims 1 to 6 ,
Having a plurality of functional blocks consisting of the sampling unit, the abnormality detection element state determination unit, and the circuit determination unit,
Each said functional block is comprised separately by several different program processing apparatuses, The combustion control apparatus characterized by the above-mentioned . The combustion control device according to any one of claims 1 to 6 ,
A combustion control device further comprising a control unit that controls the operation of a burner based on the determination results of the abnormality detection element state determination unit and the circuit failure determination unit . A combustion control device according to claim 8 ,
The burner provided in a combustion chamber and controlled by the combustion control device;
A combustion system.

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