JPH06201582A - Smoke sensing apparatus - Google Patents

Abstract

PURPOSE:To detect smoke carefully by arranging a light emitting element, a light receiving element and a signal processing circuit for detecting the presence/absence of smoke, and providing the processing circuit with a memory part for storing the data of the voltage level of a detecting signal and a holding time of the voltage level and a control part for making a correction to a predetermined sensing level of smoke. CONSTITUTION:An output signal of a photodetecting diode 2 is input and amplified at an amplifier circuit 9, and then connected to a microcomputer 20. When no smoke is present at the starting time, the circuit 9 is corrected to a voltage of a low range, which is used as a level reference value. The correction is effected by the control by a CPU 23 of the microcomputer 20 in the course from a PWM generating circuit 22, a smoothing circuit 15 to the circuit 9. The correcting value is stored in a RAM 26. In the event that a detecting signal is raised to indicate for a long time that the smoke is present, it is so judged that this is not smoke, but caused by the other reason such as an outdoor light or the like. The output signal showing that the smoke is present is stopped and the detecting signal is corrected to be close to a preset sensing level of smoke. The time of the level of the detecting signal is stored in the RAM 26. The same correction is carried out also in the case where smoke is present at the starting time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric smoke detector used in an air cleaner or the like.

[0002]

2. Description of the Related Art Generally, in a photoelectric smoke sensing device, the detection signal changes even in the absence of smoke. This is due to deterioration of the light emitting element, deterioration of the light receiving element, fluctuation of the mechanical section, fluctuation of the optical section due to adhesion of dust and the like. Therefore, it is impossible to judge the presence or absence of smoke detection with an absolute value in the long term.

For this reason, it is general to detect the change in the detection signal and determine the presence or absence of detection. A conventional example of this method will be described with reference to FIG.

FIG. 3 is a block diagram of a conventional photoelectric smoke sensing device (hereinafter, simply referred to as a smoke sensing device).

As shown in FIG. 3, the smoke detecting section comprises a light emitting diode 1, a photodiode 2, a visible light cut filter 3, a holder 4, and a smoke sensor case 5 (part). 6 is a smoke detector, 6'is smoke particles, 7 is a light emitting diode drive circuit, and 8 is an oscillation circuit. The light emitting diode 1 and the photodiode 2 are arranged so that their optical axes are substantially orthogonal to each other, and have a structure for detecting scattered light of the smoke particles 6 '. The light-emitting diode 1 is A in the detection signal processing described later.
In order to facilitate detection processing such as C amplification, pulse emission is used (normally several ms to several tens ms). The detection signal received by the photodiode 2 is sent to the amplification circuit 9 and amplified.

After that, the amplified signal is input to the integrating circuit 10 having a small time constant and the integrating circuit 11 having a large time constant, and then input to the differential amplifier circuit 12, respectively.

Further, the integrating circuit 10 and the differential amplifier circuit 1
Each output of 2 is input to the comparison amplifier 13. Reference numeral 14 is a reference voltage generator.

In this circuit, the output of the integrating circuit 10 having a small time constant changes in a short time when smoke is generated in the absence of smoke. (For example, several msec to several sec). On the other hand, the output of the integrating circuit 11 having a large time constant does not change when the detection signal changes in a short time, and is output when the detection signal changes gradually (for example, several tens of seconds or more) or when the signal changes little. It For example, when dust adheres to the smoke sensor case 5 in the absence of smoke or when the ambient light is constant after increasing or decreasing, the outputs of the integrating circuits 10 and 11 having large and small time constants both change, and the difference The output of the dynamic amplifier circuit 12 does not change.

[0009]

By the way, in the above-mentioned conventional smoke sensing device, since the time constants of the integrating circuits 10 and 11 are determined by the capacitors and resistors (τ = C × R), an attempt is made to increase the time constant. Then, a large-capacity capacitor is needed and the shape becomes large, resulting in an increase in cost. In addition, it is difficult to set the value over a certain time constant (for example, over several tens of minutes) in reality. Further, since the time constant curve is fixed with respect to the change in the detection signal, it is not possible to perform fine signal processing.

In view of the above, the object of the present invention is to eliminate the integration circuit and reduce the size, and to observe the change of the detection signal without being restricted by the time constant curve for a long period of time, and to make a fine-tuned response to the presence or absence of smoke. To provide a device.

[0011]

In order to achieve the above object, the present invention receives a light emitting element arranged substantially at right angles to a smoke detecting section and the reflected light of the light emitting element from the smoke detecting section. It has a light receiving element and a signal processing circuit that determines the presence or absence of smoke based on a change in the detection signal of the light receiving element, and the signal processing circuit stores the voltage level of the detection signal and the data of the voltage level holding time. It is characterized by comprising a storage unit and a control unit for outputting a signal for correcting the detection signal to a predetermined smoke detection level according to the stored data.

[0012]

As described above, since the smoke sensing device of the present invention has the storage unit for storing the data of the voltage level of the photodetection signal and the voltage level holding time, the conventional capacitor which takes place is used. This eliminates the need for the integrated circuit and reduces the size.

Further, a long-term change can be detected regardless of the time constant curve of the detection signal.

Further, since the detection signal is corrected according to the stored data, the difference between external light and smoke can be clarified. For example, when it is detected that there is smoke for a long time, it is determined that this is not due to smoke but due to other factors such as external light, and the detection signal is corrected to approach a predetermined smoke detection level.

As a result, when this smoke sensing device is used in, for example, an air purifier, it is possible to stop a wasteful operation such as the fan continuing to rotate even though there is no smoke, and to achieve efficient operation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram of a smoke sensing device according to the present embodiment, and FIGS. 2A and 2B are views for correcting the smoke sensing level of the smoke sensing device according to the present embodiment to the actual output level (described later). It is a figure demonstrated with reference to P point).

In FIG. 1, the same functional parts as those in FIG. 3 are designated by the same symbols. Here, only the points different from FIG. 3 will be described.

As shown in FIG. 1, the output signal of the light receiving diode 2 is input to the amplifier circuit 9, amplified, and then connected to the A / D converter 21 of the microcomputer 20.

The microcomputer 20 has the above-mentioned A / D converter 21.
Besides, the PWM generation circuit 22 and the CPU 2 as the control unit
3, oscillation circuit 24, ROM 25, RAM as a storage unit
26 and an output circuit 27.

Of these, the PWM generation circuit 22 is the smoothing circuit 1.
It is connected to the amplifier circuit 9 via 5. As will be described later, the PWM generation circuit 22 and the smoothing circuit 15 have an amplifier circuit 9
The signal is adjusted by the CPU 23 so that the output signal level of 1 approaches a predetermined value.

The light emitting diode drive circuit 7 is connected to the CPU 23 of the microcomputer 20 and controlled by the CPU 23.

The smoke detection level correction of the smoke detection device having the above-mentioned structure will be described below with reference to FIGS. 2 (a) and 2 (b).

FIGS. 2A and 2B are diagrams showing the detection signal at point P in the block diagram of FIG. First, FIG.
As shown in (a), the case of no smoke at the time of starting will be described. The smoke detection level at the start is corrected in the differential amplifier circuit 9 to a voltage having a low dynamic range of the amplifier (for example, the start level 2.4V → 1V) (A
Part). This 1V is the level reference value when there is no smoke.

Here, this correction is performed by the CPU of the microcomputer 20.
By the control of 23, the PWM generating circuit 22 → the smoothing circuit 15
→ This is performed on the path of the differential amplifier circuit 9. The corrected value (1V) is stored in the RAM 26 of the microcomputer 20.

Then, consider the case where the voltage value of the detection signal rises to about 2 V due to the influence of external light or dust (B
Part).

Since the detection signal rises from 1V to 2V,
Once it is determined that there is smoke, an output signal indicating that there is smoke is output. In accordance with this output signal, for example, in the case of an air purifier, a fan rotation operation or the like is performed.

However, if the detection signal does not change much from 2 V (± 0.1 V) for a long time (for example, about 5 minutes), it is considered that this voltage rise is not due to smoke (usually Smoke cleaning does not last for 5 minutes), it is judged that it is due to external light or dust, the output signal with smoke is stopped, and the level of the detection signal is 2V → 1.
It is lowered to 5V (part C). Here, the time of the level of the detection signal is stored in the RAM 26 of the microcomputer 20. After that, when the detection signal level change of 1.5V similarly changes for about 5 minutes and only about ± 0.1V, it is further decreased to 1.5V → 1V (reference value without smoke) (D
Part). Then, similarly to the operation after the start, the presence or absence of smoke is detected based on this 1V.

As described above, in this embodiment, when it is detected that smoke is present for a long time, it is determined that this is not smoke but other factors such as external light, and the detection signal is predetermined. Correct so that it approaches the smoke detection level. This allows
When this smoke sensing device is used in, for example, an air purifier, it is possible to stop useless operations such as the fan continuing to rotate even if there is no smoke, and to achieve efficient operation.

Next, the case where there is smoke at the time of starting will be described.

As in the case of FIG. 2A, the smoke detection level at the time of starting is corrected to about 1V in the differential amplifier circuit 9 (for example, 3V → 1V, section E). After that, when the smoke becomes thin due to diffusion or the like, the voltage value of the detection signal decreases (for example, 1
If the 0.7V state continues for a long time (for example, 5 minutes), the smoke detection level is corrected to 1V again (V section 0.7V, F section) (G section). After that, the presence or absence of smoke is detected based on this 1V.

As described above, in the present embodiment, the detection voltage in the normal smokeless state does not exceed a certain level,
In addition, in consideration of the fact that the smoke stays for some reason or reaches the saturation level of the amplifier, the detection voltage is not corrected beyond a certain level.

Further, the correction is slow when the smokeless detection level changes due to the influence of outside light or dust (when the detection level becomes high), and the smokeless detection is performed when there is smoke at the start (the detection level becomes low). The correction speed is set to be faster.

As described above, in the present embodiment, the smoke-free level, the detection signal for a certain period, and the like are sent to the microcomputer 2.
Since it is stored in the memory of 0 and the RAM 26, the detection level can be corrected after a long time detection and the smokeless level can be updated unlike the conventional case, and fine processing can be performed, which is effective against malfunctions due to changes in the smokeless level. is there. Further, because of digital processing, parts such as capacitors that hinder the miniaturization can be omitted and miniaturization becomes possible.

[0035]

As described above, according to the present invention, the integrating circuit can be eliminated and the size can be reduced, the change which is not restricted by the time constant curve of the detection signal can be observed for a long time, and the smoke detection level can be corrected. It is possible to provide a smoke detection device that can perform a fine detection operation.

[Brief description of drawings]

FIG. 1 is a block diagram of a smoke detection device according to an exemplary embodiment of the present invention.

2A and 2B are diagrams illustrating detection level correction of a smoke detection device according to an exemplary embodiment of the present invention.

FIG. 3 is a block diagram of a conventional smoke detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 6 Smoke detecting section 6'Smoke particle 20 Microcomputer (signal processing circuit) 23 CPU (control section) 26 RAM (storage section)

Claims (1)

[Claims] 1. A light emitting element arranged substantially perpendicular to a smoke detecting section, a light receiving element for receiving reflected light of the light emitting element from the smoke detecting section, and a smoke signal generated by a change in a detection signal of the light receiving element. A signal processing circuit for determining the presence / absence of the detection signal, wherein the signal processing circuit stores a voltage level of the detection signal and data of the voltage level holding time, and the detection signal in advance according to the storage data. A smoke detecting device, comprising: a control unit that outputs a signal for correcting the smoke detection level to a predetermined level.