JPS61122799A - Optical type smoke detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical smoke detection device that detects smoke using light emission and light reception.

[Conventional technology]

Conventionally, in this type of device, when a light emitting element emits light in a pulsed manner and a pulsed light synchronized with the emitted light is received, the presence or absence of smoke is determined based on the magnitude of the received light signal.
.

[Problem that the invention seeks to solve]

However, there is a problem in that the light reception signal changes greatly due to the influence of ambient light and the like, making it impossible to obtain an accurate signal corresponding to the amount of smoke in the smoke detection area.

The present invention has been made in view of the above-mentioned problems, and is capable of obtaining an accurate signal corresponding to the amount of smoke in a smoke detection area without being affected by ambient light or the like.

[Means for solving problems]

In order to achieve the above technical problem, the present invention, as shown in FIG. 1, includes a light emitting element that emits light to an area where smoke detection is performed;
a light-receiving element that receives light from the area; a light-emitting element driving means that pulse-drives the light-emitting element; an amplifier that amplifies the output of the light-receiving element; a first detection means for detecting a signal from the amplifier as a first detection signal, and a signal from the amplifier when driving the light emitting element in the four stages of light emitting element drivers as a second detection signal. Second to detect
a detection means, a third detection means for detecting a signal from the amplifier immediately after the light emitting element is driven by the light emitting element driving means as a third detection signal, and a first detection detected by the first detection means. a first calculation means for calculating the amount of noise existing in the region while driving the light emitting element from the signal and a third detection signal detected by the third detection means; From the detected second detection signal to the first
The present invention is characterized by comprising a second calculation means for removing the amount of noise calculated by the calculation means and obtaining a signal corresponding to the amount of smoke existing in the area.

[For production]

According to the above configuration, the amount of light in the smoke detection area immediately before and after the light emitting element emits light is detected, the amount of noise due to ambient light etc. while the light emitting element is emitting light is estimated, and the amount of noise caused by ambient light etc. while the light emitting element is emitting light is estimated. The amount of noise is removed from the detected value when the smoke is detected, and a signal corresponding to the amount of smoke present in the smoke detection area is obtained.

〔Effect of the invention〕

Therefore, by removing the amount of noise caused by ambient light and the like, there is an excellent effect that an accurate signal corresponding to the amount of smoke in the smoke detection area can be obtained.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 2 is a block diagram representing one embodiment of the present invention,
A indicates a scattered light type smoke detector (hereinafter simply referred to as a smoke detector), and B indicates an air purifier controlled by the smoke detector A.

In FIG. 2, 101 is a microcomputer that generates a light emission timing pulse for causing a light emitting diode (hereinafter referred to as LED) 103 to emit light, and
Sends an A/D conversion start signal to the D converter 106
It captures the converted light reception signal, determines the presence or absence of smoke based on that data, and controls the air purifier B.

102 is a light emitting element driving circuit that generates a light emitting pulse to actually cause the LED 103 to emit light based on the light emitting timing pulse given by the microcomputer 101. Reference numeral 103 denotes an LED element that emits light in response to a light emission pulse generated by the light emitting element drive circuit 102. 104
is a photodiode which is a light-receiving element and has the highest light-receiving sensitivity with respect to the peak emission wavelength of the LED 103, and is mounted at an angle to the LED 103 so that it does not receive direct light from the LED 103.

Reference numeral 105 designates an AC amplifier that amplifies the minute light-receiving signal generated by the light-receiving element 104 and outputs it to the A/D converter 106, and the frequency band of this amplifier is from several Hz to several KHz.
Therefore, for example, a signal that gradually changes with a period of IHz or less or a signal that changes suddenly with a period of 100 KHz or more is not amplified by the amplifier 105. 106 is an A/D converter which receives an A/D conversion start signal outputted from the microcomputer 101, converts the light reception signal amplified by the AC amplifier 05 into a digital signal, and outputs the digital signal to the microcomputer 101. .

The operation of smoke detector A will be explained using the waveform diagram in FIG.

When the microcomputer 101 gives a light emission timing pulse with a pulse width TW% period TO to the light emitting element drive circuit 102 as shown in FIG. is arranged so as not to receive direct light from the LED 103, so when there is no smoke in the sensing area, its output will be at a constant linear level as shown in period ■ in Figure 3 (bl), When smoke enters, the light emitted by the LED 103 is scattered by the smoke, and the light receiving element 104 receives this scattered light.
The light reception signal is as seen in period ■ of l. Since such a light reception signal obtained by the light receiving element 104 is actually very small, by amplifying it with the AC amplifier 105, a light reception signal as shown in FIG. 3(b) can be obtained. The microcomputer 101 converts only a necessary portion of this light reception signal into a digital signal using an A/D converter 106, takes in the data, and determines the presence or absence of smoke based on the size of the data.

What we must be careful about here is the problem of noise. Particularly when smoke detector A is used in a car, in addition to electrical noise caused by fluctuations in battery voltage, there are also noises such as entering and exiting tunnels or garages while the car is running, reflections of sunlight from objects or oncoming cars, etc. There is optical noise (disturbing light) that causes the surrounding brightness to change rapidly. Also, the headlights and outside lights (fluorescent lights) of other cars while driving at night are also types of light noise. The level and cycle of these noises vary depending on the driving condition of the car, but IH
Optical noise that changes slowly below ZZ and noise that changes rapidly above several tens of KHz do not constitute noise in the main smoke sensor A. This is because the frequency band of the AC amplifier 105 is from several Hz to several KHz, so these noises are not amplified.

In the case where optical noise of several Hz to several KHz enters, which is a particular problem, the output of the AC amplifier 105 becomes a signal as shown in FIG. 3 (C1).

In the figure, the areas where the background level (called BG level) increases as shown by
Among these signals, the microcomputer 101 captures only the light reception signal that is synchronized with the light emission pulse of the LED 103, and determines the presence or absence of smoke based on the magnitude of the signal. According to the conventional technology, when noise enters in synchronization with the emitted light pulse as shown in ■ in the figure, it is impossible to distinguish between the noise and the received light signal due to smoke, so it is assumed that smoke is present even though there is no smoke. Misjudgment may occur.

In order to reduce such erroneous judgments, the present invention incorporates not only the light reception signal synchronized with the light emission pulse but also the BG level immediately before and after the light emission pulse as data, and extracts the true smoke signal from which the influence of optical noise has been removed from these data. The presence or absence of smoke is determined based on the received light signal.

The arithmetic processing of the microcomputer 101 will be explained below according to the flowchart shown in FIG.

When the microcomputer 101 is supplied with power, it executes an initial setting step 401 and initializes internal counters and timers for subsequent processing. Next step 4
02 is executed and the internal software timer TM sets the time TO.
It is determined whether the time T0 has elapsed or not, and if it has elapsed, the process proceeds to the next step 403, and if it is determined that the time has not elapsed, the process returns to the beginning of step 402 again, and the timer TM checks whether or not the time T0 has elapsed. to judge. In other words, step 402 is repeated until time T0 has elapsed since the timer TM was initially set. Here, 70 hours is LE
This is the light emission period for causing D 103 to emit light. If the timer TM determines in step 402 that the time T0 has elapsed, then step 4.3 is executed and the timer TM is set.

Next, step 404 is executed and the LE
Input the BG level V immediately before making D103 emit light and store it in the memory 0 Next, execute step 405 and wait until T1 time has elapsed after executing step 404 6
Next, step 406 is executed, and a light emission signal for causing the LED to emit light is output to the light emitting element drive circuit 102 to cause the LED to emit light.Next, step 407 is executed, and 72 hours have elapsed since step 406 was executed. wait until
During these 72 hours, there is a delay from when the LED 103 emits light until the light receiving element 104 receives the light, the light receiving signal is amplified, and the microcomputer 101 is ready for input, so wait for at least that delay time before inputting the light receiving signal. This is the time set aside for this purpose.

Next, step 408 is executed, and while the LED L03 is emitting light, the light reception signal v2 is input and stored in the memory. Next, step 409 is executed to turn off the light emission signal to turn off the LED 103.

Next, step 410 is executed, and the process waits until T3 time has elapsed since step 409 was executed.

This 73 hours is the time from when the LED is turned off until the next BG level v3 can be read. Next, execute step 411 and input the BG level v3 after turning off LED I03. Step 412 is executed to calculate the average value vo of the BG level vI immediately before the LED light emission stored in the memory and the BG level v3 immediately after the Q light ends. The calculation formula at this time is V o
= (V r +V 3) / 2-(tl.

Vo obtained here is the average value of the BG level immediately before the light emission and immediately after the end of the light emission, but it can be considered as an estimated value of the BG level at the time of light emission. Next, execute step 413 and
D103 light reception level when emitting light ■2 and previous step 412
Calculate the difference (3) from the average value VO obtained in . In other words, it calculates Vs=V2-V□ (2). Now, if we consider the components of ■2 signals, let VSM be the true light reception signal due to the presence of smoke, and VB be the BG level at the time of light emission, then V2""VSM+VB. Therefore, equation (2) is Vs=VsM+VB V□"・(3). As mentioned earlier, Vo is considered to be the estimated value of the BG level at the time of light emission, so it is BB11+1VO. Therefore, equation (3) becomes VsζvsM for reasons greater than 0. V is considered to be a true light reception signal due to the presence of smoke from which noise due to the influence of ambient light has been removed.

Next, step 414 is executed, and it is determined whether or not V calculated in the previous step 413 is larger than the reference value VON for turning on the air purifier.

Here, when V is larger than VON, it means that there is smoke of a certain reference concentration or higher, and therefore, in this case, the process advances to the next step 415 and air purifier B is turned on. The process then returns to step 402 and performs the previously described operations again. On the other hand, if it is determined in step 414 that Vs is smaller than VON, this means that the smoke concentration is below a certain level, and in this case the process proceeds to the next step 416. Step 416
So, vs is the reference value VOFF that turns off air purifier B.
If it is determined that Vs is smaller than VOFF, it means that the air has been sufficiently purified and there is almost no smoke, and in this case, the next step 417 is performed. Go to step and turn off air purifier B. The process then returns to step 402 and performs the previously described operations again. Furthermore, if it is determined in step 416 that Vs is greater than VOFF, this means that the air has not been sufficiently purified and some smoke remains (smoke density equal to or higher than VOFF), and in this case, no new operation is required. Otherwise, the process returns to step 402 and the operation described above is performed.

In the above embodiments, a scattered light type smoke detector has been described, but the present invention can also be applied to a transmitted light type smoke detector. FIG. 6 shows the configuration of a transmitted-light type smoke detector. A light receiving element 104 is arranged to face a light emitting element 103 so that their optical axes coincide with each other, and directly receives the light emitted by the light emitting element 103. It is supposed to be done. In such a configuration, if smoke exists between the light emitting element 103 and the light receiving element 104, the amount of light received by the light receiving element 104 will decrease.
As shown in the figure (bl), the light reception signal also decreases.The microcomputer 101 checks this decrease in the light reception signal to know the presence of smoke.However, as described in the above embodiment, when the surrounding brightness suddenly decreases, the microcomputer 101 detects the presence of smoke. When the light intensity changes, the received light signal changes as shown in FIG. 7(C).

As a countermeasure against such noise, processing can basically be performed based on the flowchart in FIG. 4, but the judgment in step 414 is changed to VS<V'ON, and
16 must be changed to VS>VOFF. This can reduce malfunctions of the transmitted-light type smoke detector due to ambient light.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a block diagram showing an embodiment of the invention, Fig. 3 is a waveform diagram showing signal waveforms of each part in Fig. 2, and Fig. 4 is a block diagram showing the configuration of the present invention. FIG. 5 is a flowchart showing the arithmetic processing of the microcomputer in FIG. 1, FIG. 5 is an explanatory diagram for explaining the operation, FIG. 6 is a block diagram showing another embodiment, and FIG. FIG. 3 is a waveform diagram showing signal waveforms. 101... Microcomputer, 102... Light emitting element drive circuit, 103... Light emitting element,' 104...
- Light receiving element, 105...AC amplifier.

Claims (1)

[Claims] a light emitting element that emits light to an area where smoke detection is performed;
a light-receiving element that receives light from the area; a light-emitting element driving means that pulse-drives the light-emitting element; an amplifier that amplifies the output of the light-receiving element; a first detection means for detecting a signal from the amplifier as a first detection signal; and a first detection means for detecting a signal from the amplifier as a second detection signal when the light emitting element is being driven by the light emitting element driving means. a second detection means; a third detection means for detecting a signal from the amplifier immediately after the light emitting element is driven by the light emitting element driving means as a third detection signal; a first calculation means for calculating the amount of noise existing in the region while driving the light emitting element from the first detection signal and the third detection signal detected by the third detection means; and the second detection means. and a second calculation means for removing the noise amount calculated by the first calculation means from the second detection signal detected by the second calculation means to obtain a signal corresponding to the amount of smoke existing in the area. Device.