JP4037802B2 - Flame detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flame detection apparatus that detects light generated at the time of a fire by detecting light having a wavelength specific to the flame.
[0002]
[Prior art]
As a conventional flame detection apparatus, the present applicant has disclosed a flame detection apparatus that samples a detection signal of a light detection element that detects light having a wavelength peculiar to a flame at a sampling frequency exceeding 120 Hz. This prevents the noise signal of the commercial power supply frequency (50 Hz, 60 Hz), which is a noise source, from being superimposed on a predetermined frequency component including the vicinity of the flame fluctuation frequency used for flame judgment as a folded noise, and detects the flame with high accuracy. It became possible to do. (For example, refer to Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application No. 2002-13306
[Problems to be solved by the invention]
This flame detection device extracts a predetermined frequency component including a fluctuation frequency component of a flame from an output signal sampled at a sampling frequency exceeding 120 Hz by a digital filter, and performs a flame determination using the output signal of the digital filter. Yes. In particular, it is difficult to design an analog filter with a steep cut-off characteristic at a low frequency such as the fluctuation frequency of a flame. On the other hand, a digital filter can easily create an ideal filter characteristic. A noise signal in a frequency band other than the frequency band can be sufficiently attenuated to detect a flame with high accuracy. However, since sampling is performed at a sampling frequency exceeding 120 Hz, high processing capability is required. As a result, the amount of processing per unit time has increased, causing problems such as increased power consumption and cost.
[0005]
The present invention has been made in order to solve the above-described problems, and suppresses the processing amount per unit time without requiring high processing capacity, suppresses increase in power consumption and cost, and detects flames with high accuracy. For the purpose.
[0006]
[Means for Solving the Problems]
The present invention relates to a flame detection device that detects light generated at the time of a fire by detecting light having a wavelength specific to the flame, a light detection element that detects light having a wavelength specific to the flame and outputs an electrical signal; An amplifying unit that amplifies the output signal of the light detection element, an AD converting unit that converts the output signal of the amplifying unit into a digital signal at a predetermined sampling frequency, and a specific frequency component is extracted from the output signal of the AD converting unit A digital signal processing unit; and a determination unit that determines a flame using an output signal of the digital signal processing unit, wherein the predetermined sampling frequency is lower than a known frequency band of a noise source and the noise The frequency band of the source is set so as to be turned back to other than the specific frequency band, and further includes a setting unit capable of setting the predetermined sampling frequency and the specific frequency .
[0007]
The known noise source is commercial power supply frequency noise of 50 Hz or 60 Hz .
[0008]
【Example】
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic block diagram showing a configuration of a flame detection device that detects light generated at the time of a fire by detecting light having a wavelength peculiar to flames. FIG. 2 is a flowchart showing the operation of the MPU 7 of FIG.
[0009]
In FIG. 1, reference numeral 1 denotes a light detection element that detects light having a wavelength peculiar to a flame and outputs an electric signal, for example, a pyroelectric element that detects light having an infrared wavelength peculiar to a flame and outputs an electric signal. is there. Reference numeral 2 denotes an amplification unit that amplifies the output signal of the light detection element 1. Reference numeral 3 denotes an AD converter that converts the output signal of the amplifier 2 into a digital signal at a predetermined sampling frequency. Reference numeral 4 denotes a digital signal processing unit that extracts a specific frequency component from the output signal of the AD conversion unit 3, and is constituted by a digital filter, for example. The digital filter is difficult to design an analog filter with a steep cut-off characteristic at a low frequency such as a flame fluctuation frequency, but an ideal filter characteristic can be easily created. There is an advantage that noise signals in frequency bands other than the transmission frequency band can be sufficiently attenuated.
[0010]
Reference numeral 5 denotes a determination unit that determines the flame using the output signal of the digital signal processing unit 4. Reference numeral 6 denotes a timer unit that sends a capture signal to the MPU 7 (described later) when the sampling interval (sampling frequency) stored in the RAM 9 (described later) is reached. Based on this captured signal, the MPU 7 3 is made to perform sampling at a predetermined sampling frequency. Reference numeral 7 denotes a microcomputer (hereinafter referred to as MPU) that controls the entire flame detection apparatus, and includes an AD conversion unit 3, a digital signal processing unit 4, a determination unit 5, and a timer unit 6. The digital signal processing unit 4, the determination unit 5, and the timer unit 6 may be appropriately provided outside the MPU 7. Reference numeral 8 denotes a ROM that stores a program such as the flowchart shown in FIG. Reference numeral 9 denotes a RAM for storing the output signal of the digital signal processing unit 4 and the like.
[0011]
10 is determined by a sampling interval for determining a predetermined sampling frequency in the AD conversion unit 3 and a specific frequency component of the output signal extracted by the digital signal processing unit 4 (that is, an upper limit of the specific frequency and a lower limit of the specific frequency) The setting unit can set various setting information such as a filter coefficient and the number of taps for determining a frequency range to be set. The setting unit 10 is configured to be able to input various setting information such as a sampling interval, a filter coefficient, and the number of taps from the outside.
[0012]
Reference numeral 11 denotes a storage unit that stores various setting information such as a sampling interval, a filter coefficient, and the number of taps set by the setting unit 10, and is, for example, a rewritable nonvolatile EEPROM. The storage unit 11 stores in advance default data that is a reference value of various setting information such as a sampling interval, a filter coefficient, and the number of taps. For example, in order to determine the sampling frequency as 45 Hz, the sampling interval is set to 22 mS. In addition, the filter coefficient and the number of taps necessary for determining the specific frequency component in the digital signal processing unit 4 as 7 to 12 Hz (that is, the upper limit of the specific frequency is 7 Hz and the lower limit of the specific frequency is 12 Hz) are appropriate. Stored as an arbitrary value. Reference numeral 12 denotes an output unit that outputs a fire signal when the determination unit 5 determines the flame.
[0013]
Here, prior to the flowchart of FIG. 2, a relationship between a predetermined sampling frequency in the AD conversion unit 3 and a specific frequency component of the output signal extracted in the digital signal processing unit 4 will be described.
[0014]
First, the flame detection apparatus of the present invention amplifies the output signal of the light detection element 1 by the amplification unit 2, converts the output signal of the amplification unit 2 into a digital signal by the AD conversion unit 3 at a predetermined sampling frequency, and performs AD conversion. A specific frequency component is extracted from the output signal of the unit 3 by the digital signal processing unit 4, and the flame determination unit 5 determines the flame using the output signal of the digital signal processing unit 4.
[0015]
Here, the default data stored in advance in the storage unit 11 is set to an arbitrary value such that the sampling frequency is 45 Hz, the upper limit of the specific frequency is 7 Hz, and the lower limit of the specific frequency is 12 Hz. Assuming the case where it is used for the operation of the detection device, the sampling theorem indicates that, among the frequency components included in the original signal (in this case, the output signal of the amplification unit 2), a frequency component higher than ½ of the sampling frequency. If it is included, the component is folded into a frequency component within 1/2 of the sampling frequency in the sampling result (in this case, the output signal of the AD conversion unit 3). In this case, since the sampling frequency of the AD conversion unit 3 is set to 45 Hz, the commercial power supply frequency 50 Hz as an example of a known noise source is 5 Hz (= 50−45 / 2 × 2), and the commercial power supply frequency 60 Hz is 15 Hz. It is folded back to (= 60−45 / 2 × 2).
[0016]
And as a specific frequency component of the output signal extracted by the digital signal processing unit 4 from the output signal of the AD conversion unit 3, in this case, the specific frequency component is set as 7 to 12 Hz. A predetermined low frequency component (7 to 12 Hz) including a typical flame fluctuation frequency component is extracted. The extracted output signal of the digital signal processing unit 4 is a commercial power source as an example of a known noise source. It does not include frequency components of 5 Hz and 15 Hz that are folded at frequencies of 50 Hz and 60 Hz. That is, the noise signal of the noise source is turned back to other than the specific frequency band of 7 to 12 Hz.
[0017]
Thus, the flame detection apparatus of the present invention has a sampling frequency of the AD conversion unit 3 lower than a known frequency band of a noise source, and the frequency band of the noise source is a specific frequency necessary for flame determination. Since various setting information is set so that conditions other than the band are folded, the noise signal of the noise source is not included in the output signal required for flame judgment. As with equipment, high-accuracy output signals are obtained by separating the noise components of the noise source, and the processing frequency per unit time is reduced without the need for high processing capacity due to the reduced sampling frequency, resulting in power consumption and cost. Therefore, it is possible to detect the flame with high accuracy.
[0018]
In addition, as default data of various setting information stored in advance in the storage unit 11, an arbitrary value may be set as appropriate so as to meet the above-described conditions. For example, the sampling interval is set to 36.36 mS so that the sampling frequency is 27.5 Hz, and the filter coefficient, the number of taps, etc. are set so that the upper limit of the specific frequency is 7 Hz and the lower limit of the specific frequency is 12 Hz. Even if an arbitrary arbitrary value is set, the commercial power supply frequency 50 Hz which is an example of the noise source at this time is 5 Hz (= 13.75− (50−27.5 / 2 × 3)), and the commercial power supply frequency 60 Hz is 5 Hz. It will be folded back to (= 60-27.5 / 2 × 4), and it can be folded back to other than a specific frequency band.
[0019]
Next, the operation of the flame detection apparatus will be described based on a flowchart showing the operation of the MPU 7 in FIG.
[0020]
First, various setting information such as a sampling interval, a filter coefficient, and the number of taps is set by the setting unit 10 (step S1). Although not described in detail as the setting operation, for example, an external device such as a personal computer is connected to the setting unit 10 with a cable, and external data of the external device in which arbitrary values of various setting information desired to be set in advance are stored. 10 to input. In addition, about various setting information to set, arbitrary values shall be suitably set so that the said conditions may be met. Further, when the default data in the storage unit 11 is used, no input is made to the setting unit 10.
[0021]
Next, for example, after a predetermined input waiting time has elapsed, when the MPU 7 receives various setting information input to the setting unit 10 (step S2), the MPU 7 stores the input various setting information in the storage unit 11 (step S3). ). And various setting information of the memory | storage part 11 is stored in RAM9 (step S4). When various setting information is not input to the setting unit 10 (step S2), various setting information of default data stored in advance in the storage unit 11 is stored in the RAM 9 (step S4). Then, in cooperation with the timer unit 6, the MPU 7 samples the output signal of the light detection element 1 at a predetermined sampling frequency set by the sampling interval stored in the RAM 9 (step S5). That is, the output signal of the light detection element 1 is amplified by the amplification unit 2, and the AD conversion unit 3 converts the output signal of the amplification unit 2 into a digital signal at a predetermined sampling frequency. Then, the output signal of the AD conversion unit 3 is stored in the RAM 9.
[0022]
Next, the MPU 7 outputs the output signal in a specific frequency range (that is, a frequency range determined by the upper limit of the specific frequency and the lower limit of the specific frequency) set by the filter coefficient, the number of taps, and the like stored in the RAM 9. A specific frequency component is extracted (step S6). That is, the digital signal processing unit 4 extracts a specific frequency component from the output signal of the AD conversion unit 3 stored in the RAM 9. Then, the output signal of the digital signal processing unit 4 is stored in the RAM 9.
[0023]
And MPU7 judges a flame using the output signal of the digital signal processing part 4 stored in RAM9 (step S7). For example, when a predetermined number of effective values of the output signal of the digital signal processing unit 4 stored in the RAM 9 are calculated and this calculated value is less than the flame judgment value stored in the EEPROM 11 (step S7), the normal value of step S5 is used. Returning to the monitoring state, and when the calculated value is equal to or greater than the flame judgment value stored in the EEPROM 11 (step S7), the output unit 12 outputs a fire signal (step S8).
[0024]
If it is desired to set various setting information in step S1 again, a step for monitoring the setting unit 10 is provided between step S5 and step S7, and when there is an input, the process returns to step S1. Good.
[0025]
Moreover, only default data is used as various setting information, and when it is not necessary to change suitably according to the environmental change of an installation site, the setting part 10 may be abbreviate | omitted, In that case, step S1- Step S3 may be omitted.
[0026]
In this flame detection apparatus, the sampling frequency is set lower than the known frequency band of the noise source, and the frequency band of the noise source is set to be turned back to other than the specific frequency band. Therefore, the amount of processing per unit time can be suppressed, the increase in power consumption and cost can be suppressed, and the flame can be detected with high accuracy.
[0027]
In addition, since a setting unit that can set a predetermined sampling frequency or a specific frequency is provided, even if the environment such as the installation site changes, the predetermined sampling frequency or the specific frequency can be changed appropriately according to the installation site This makes it possible to detect a flame with high accuracy. For example, according to the fluctuation frequency of the flame that changes in response to environmental changes such as the air volume and wind direction at each installation site, the specific frequency band used for flame judgment is optimally set, and the commercial power supply noise is specified accordingly. If the sampling frequency is set so that it does not overlap as a folding noise near the frequency band, or if there is a specific noise source frequency band at the installation site, first, the specific noise will appear as a folding noise near the flame fluctuation frequency. Set the sampling frequency to avoid overlapping as much as possible, and optimize the specific frequency band used for flame judgment so as to obtain the output signal as much as possible, that is, to contain the fluctuation frequency of the flame as much as possible It becomes possible to set.
[0028]
In the above-described embodiment, the light receiving element 1 is a pyroelectric element that detects light having an infrared wavelength peculiar to flames. However, a thermopile that detects light having an infrared wavelength peculiar to flames, and light having a visible light wavelength peculiar to flames. It may be any one of a photodiode that detects light of an ultraviolet wavelength peculiar to a flame, for example, a thin-film diamond photodiode, and detects light of various wavelengths peculiar to a flame and is highly accurate. Fire detection is possible. Each light receiving element preferably detects light through a filter that selectively transmits light having a wavelength specific to the flame to be detected.
[0029]
Moreover, in the said Example, although the amplifier 2 amplified the output signal of the photon detection element 1, it is good also as a structure which abbreviate | omitted the amplifier 2. In this case, the output signal of the light detection element 1 is directly converted into a digital signal by the AD conversion unit 3 at a predetermined sampling frequency.
[0030]
Furthermore, in the said Example, although the digital signal processing part 4 was comprised by the digital filter, it may be other than that, for example, a fast Fourier transformation method (FFT: fast Fourier transformation) or a maximum entropy method (MEM: maximum entropy method).
[0031]
In the above-described embodiment, the setting unit 10 has a configuration in which various setting information can be input from the outside by an external device such as a personal computer. The setting unit 10 includes various buttons that allow the setting unit itself to input various setting information. You may comprise. For example, various setting information selection buttons such as a sampling interval setting button for selecting a sampling interval setting, a filter coefficient setting button for selecting a filter coefficient setting, a pitch number setting button for selecting a pitch number setting, and various setting information Various buttons are configured with a numeric keypad for entering the numerical value to be set, an execution button for confirming the setting of various setting information, a setting completion button for completing the setting work step of various setting information, etc. For example, when setting the sampling interval, press the sampling interval setting button, enter the numerical value you want to set with the numeric keypad, and then press the execute button for each setting information you want to set, and finally, After completing the setting of various setting information, press the setting complete button It may be carried out the operation that to complete the configuration tasks step.
[0032]
【The invention's effect】
Since the flame detection device of the present invention is configured as described above, the following effects can be obtained. According to the first aspect of the present invention, since the sampling frequency is set to be lower than the known frequency band of the noise source and the frequency band of the noise source is turned back to other than the specific frequency band, high processing is performed. It is possible to detect the flame with high accuracy by suppressing the processing amount per unit time without requiring capability, suppressing an increase in power consumption and cost.
[0033]
Moreover, since with a setting unit capable of setting a sampling frequency and a specific frequency of Jo Tokoro, even if the environment, such as the installation site is changed, according to the installation site, appropriately setting the predetermined sampling frequency and a specific frequency The flame can be detected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a configuration of a flame detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the MPU 7 of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photodetection element 2 Amplification part 3 AD conversion part 4 Digital signal processing part 5 Judgment part

Claims (2)

In the flame detection device that detects the light generated at the time of fire by detecting light with a wavelength specific to the flame,
A light detecting element that detects light having a wavelength peculiar to the flame and outputs an electric signal, an amplifying unit that amplifies the output signal of the light detecting element, and an output signal of the amplifying unit into a digital signal at a predetermined sampling frequency An AD conversion unit that converts, a digital signal processing unit that extracts a specific frequency component from the output signal of the AD conversion unit, and a determination unit that determines a flame using the output signal of the digital signal processing unit,
The predetermined sampling frequency is set to be lower than the known frequency band of the noise source and to fold the frequency band of the noise source to other than the specific frequency band ;
The flame detection apparatus further comprises a setting unit capable of setting the predetermined sampling frequency and the specific frequency . The flame detection apparatus according to claim 1, wherein the known noise source is commercial power supply frequency noise of 50 Hz or 60 Hz .

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