JPH03229150A - Device for detecting flame - Google Patents

Abstract

PURPOSE:To securely detect a flame by detecting the variation of a sound caused by the variation of the flame. CONSTITUTION:The output signal of a sound wave signal generator 2 which is driven by an inspection signal generator 1 is inputted to a reception signal amplifier 5 through vibrating elements 3 and 4. When the flame is present thereon, amplitude modulation is imposed on the output of the element 4 and the amplitude is varied according to the variation of the flame. The reception signal of the amplifier 5 becomes a DC analog signal through a detector 6 and passes through a capacitor 7 and its variation is amplified by an amplifier 8. Then the signal passes through a capacitor 10, a diode 11, and a window comparator 9 and signals are outputted from fail-safe on-delay circuits 13 and 14. Here, Q is generated when no flame is present thereon and no fault is generated even in the amplifier 8. Further, the output signal Q of the circuit 14 is generated only when the flame is present thereon. Consequently, the flame can securely be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention includes, for example, a flame in a burner. The present invention relates only to devices for detecting flames for the purpose of emitting gas, and in particular to improvements in flame detection devices for detecting the presence of a flame by emitting sound waves toward the flame and receiving sound waves propagating through the flame.

(Prior Art) A device for detecting the presence of a flame by irradiating the flame with sound has, for example, the configuration shown in FIG.

In Fig. 5, 21 is a wave transmitter, 22 is a vibrator of the wave transmitter, 23 is a waveguide for transmitting waves, 24 is a flame, 25 is a waveguide for receiving waves, and 26 is a vibrator of the wave receiver. , 27 is a receiver. In FIG. 5, a sound wave generated using a wave transmitter 21 and a vibrator 22 passes through a waveguide 23 and is irradiated onto a flame. When the flame 24 exists, the waveguide 25 whose central axis is at a predetermined angle θ with respect to the central axis of the waveguide 23 receives a sound wave refracted by the flame, and this sound wave is transmitted to the receiving transducer 26.
is detected by the receiver 27.

(Problem to be Solved by the Invention) However, when the size of the flame changes, the amplitude of the refracted sound changes, and in some cases there is a reception level that is close to the level of the sound received when there is no flame. In some cases, it was difficult to reliably detect flames. Furthermore, when there is no flame, ignition needs to be initiated by detecting whether the sensor is operating normally.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the flame detection device according to the present invention does not detect changes in sound due to the presence of flames, but detects changes in sound due to the presence of flames. It is configured to detect fluctuations in sound caused by changes.

Second, in order to ensure fail-safe detection, a test signal for testing equipment failure is superimposed on the sound transmitter, and the time when only this test signal is received is defined as a flame-free state; By configuring the system to determine that there is a flame when a fluctuating component of the sound caused by the flame is received in addition to the test signal, the sensor is normal and ignition can be started even when there is no flame. It is used as a signal.

(Function) According to the flame detection device of the present invention, it is possible to detect small changes in the propagated sound caused by the flame, and it is also possible to detect the flame with a fail-safe configuration. It becomes possible to obtain a signal that the sensor is normal.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the flame detection device according to the present invention, where l is an inspection signal generator, and 2 is a sound wave (ultrasonic wave).
Signal generator, 3 is a transducer for wave transmission, 4 is a transducer for delivery, 5
is a receiving signal amplifier, 6 is a detector, 7 is a capacitor for extracting flame changes, that is, sound fluctuations, 8 is an amplifier (7 and 8 constitute a low frequency AC amplifier), and 9 and 14 are fail-safe window comparator, E is window comparator
iI sources 10 and 11 of comparator 9 are capacitors and diodes, P
is the output signal of the window comparator, 13 is the fail-safe on-delay circuit, and °C is the on-delay circuit 1
The output signals No. 3 and Q are the output signals of the window comparator 14. Further, FIG. 2 is a time chart for explaining the operation of FIG. 1, and the items 1, 3.5, 6.
8.9.12.13.14 means the output signals of the blocks with the same numbers shown in FIGS. 1 and 4.

Next, the operation shown in FIG. 1 will be explained with reference to the time chart shown in FIG.

At No. 1511, the negative test signal P1. P2...P
The output signal of the sound wave signal generator 2, which is driven by the positive signal of the test signal generator that generates the signal 7, becomes the output signal of the received signal amplifier 5 via the transducer 3.4. There is a flame, and this flame modulates the sound). That is, the test signal P1. A sound wave is received which is interrupted intermittently by P2..., and as shown in FIG. . The received signal modulated by the flame and the test signal is converted into a DC analog signal by the detector 6 as shown in FIG. The output signal is saturated at the saturation level shown by the dotted line in FIG. 2, and becomes the signal shown in FIG. 28. The change in the output signal of the amplifier 8 is further input to a fail-safe window comparator (described later) via a capacitor lO and a diode 11, and a low level signal is generated outside the high and low thresholds T□TL of the window comparator. This becomes the output signal (FIG. 2, 9). The output signals of the window comparators are the test signals PI, P2, .
- A fail-safe on-delay circuit 13 that is reset at , and generates an output signal only when the output signal of the window comparator is present for a predetermined period of time 13 or more after the end of the test signal.
becomes the input signal. The output signal of this on-delay circuit 13 always reaches the high and low thresholds Tll TL of the window comparator after the test, when there is no flame and when there is no failure from the test signal generator l to the amplifier 8.
This always occurs because the sound reception signal is received within the range of .

However, when there is a flame, the window comparator cannot obtain the delay time t due to the fluctuation of the received level due to this change, so the output signal of the on-delay circuit is reset by the test signal and the signal is generated. do not.

On the other hand, the window comparator 14 is the 21st m14 (Q
), the upper threshold T. This produces an output, and this output signal only occurs when there is a flame.

A fail-safe window comparator is known, for example, from Japanese Utility Model Application No. 7-4764. Figure 3 shows an example of the configuration of a window bow impparator.
V), it oscillates within the range shown by the following equation, and has a characteristic of not being able to oscillate in the event of a failure (that is, a fail-safe characteristic).

where (Ra +R1+Rs)E/Rs is the lower threshold and (R4+R3)E/Rs is the higher threshold, and this interval is called the window of the window comparator. In FIG. 3, D is a rectifier circuit that superimposes the oscillation output on the power supply E and outputs it.

In addition, the fail-safe on-delay circuit uses the window comparator and PUT oscillator circuit shown in Figure 3 to create the fourth
It is configured as shown in the figure and is publicly known (for example, IEEJ Transactions Vol. 107-C, No., 10.1987).
．． P2S5). In Figure 4, Window Humper 1
When the output P (rectified output) of 2 is input, the PUT oscillator has a time constant (t+ #
After Rt C+), an output pulse a (FIG. 2, 12) is produced, and this output pulse becomes the input signal on the resistor R1 side of the window comparator in FIG. Since the output P of the window comparator is directly input to the resistor R4 side,
When the output pulse a is input, the window comparator 9 oscillates to produce an output signal Q to the rectifier circuit (D), and this output signal is fed back by the diode D, so that the input pulse a is output from the window comparator. It is self-held while the signal P is applied. Then, when the output signal P of the window comparator disappears, it is reset (assuming that the input signal P is within the range of the threshold value T and ITL by adjusting the resistors R+R4). That is, in FIG. 1, when there is no flame, the inspection signal P
+Ps+... is detected by the amplifier 8 and the window comparator 9, and the output signal Q of the on-delay 13
If there is a flame and it fluctuates, the output pulse signal of the on-delay circuit (will not occur).

Next, reference will be made to the fail-safe nature of the configuration shown in FIG. In FIG. 1, even if there is no test signal generator and the sound is generated continuously, the signal modulated by the flame is received, but the output signal from the capacitor 7 and the amplifier 8 is If no sound is received due to a failure in item 5, it will not occur even if there is a flame.

On the other hand, the output signal of the window comparator 14 is generated only when the sound wave signal generator 2 to the window comparator 14 is in a normal operating state and there is a flame, and is a fail-safe output signal.

According to the configuration shown in FIG. 1, even if such a failure occurs, the test signal cannot be obtained as the output signal of the amplifier 8.
Since the input signal of the window comparator is not available and therefore the output signal of the on-delay circuit is not generated, the configuration is fail-safe.

(Effects of the Invention) As described above, in a flame detection device that detects the presence of a flame by emitting sound waves toward a flame and receiving sound waves propagating through the flame, The structure was designed to detect changes in the amplitude of the sound, making it possible to detect small changes in sound caused by flames. In addition, a test signal is intermittently input when the sound is generated, and only when the sound generation time is longer than a predetermined time, it is determined that there is no flame, and an output signal is generated when there is no flame and the sensor is normal. Therefore, it was possible to create a fail-safe flame detection device.

It is obvious that if sensor operation monitoring is not required, the test signal generating circuit 1, the window converter 9, and the on-delay circuit 13 may be omitted and the signal modulated by the flame of the output signal of the sonic signal generator 2 may be received. be.

[Brief explanation of drawings]

FIG. 1 is an embodiment showing the configuration of the present invention, FIG. 2 is a time chart for explaining the operation of the embodiment in FIG. 1, and FIG. 3 is an example of the configuration of the window comparator according to the embodiment in FIG. FIG. 4 shows an example of the configuration of the on-delay circuit according to the embodiment shown in FIG. 1, and FIG. 5 shows a conventional example. l...Test signal generator, 7.10.Capacitor, 8..Amplifier, 9..
Window comparator, 13 on delay circuit-1
σ Figure 3 Figure 5

Claims (1)

[Scope of Claims] 2. Scope of Claims 1) A flame detection device that detects the presence of a flame by emitting sound waves toward a flame and receiving the sound waves propagating through the flame. A flame detection device comprising a transmitter for irradiating the flame, a receiver for receiving the sound wave propagating through the flame, and a detection device for detecting a change in the amplitude of the sound accompanying a change in the size of the flame. 2) The flame detection device includes a transmitter that intermittently irradiates sound waves toward the flame, a receiver that receives the intermittent sound waves propagating through the flame, an intermittent sound wave detection circuit, a flame detection circuit comprising: a detection circuit for a sound wave modulated by a flame detection circuit; 3) The flame detection device includes a transmitter that intermittently irradiates sound waves toward the flame, a receiver that receives the intermittent sound waves propagating through the flame, and the intermittent sound waves continue for a predetermined period of time. The flame detection circuit consists of an on-delay circuit and an on-delay circuit that detects this.