JPS61149847A - Smoke sensor - Google Patents

Abstract

PURPOSE:To make variation in accumulation time less than the output period of an oscillation circuit even if charging and discharging characteristics vary with temperature by increasing the output of a charging circuit almost linearly when smoke which exceeds specific thickness enters a smoke sensor area. CONSTITUTION:An oscillation circuit OF turns on an LED intermittently at a period T and a photodetecting element PD photodetects smoke particles X entering the smoke sense area and flows an pulse-like current with an amplitude proportional to the smoke thickness. An RS flip-flop FF is set at the rise (rise of output AAF of AND circuit AN) of the output VD of an amplifier AP and reset at the rise of the output of the oscillation circuit OS. Consequently, when the smoke thickness exceeds the specific value, the output Q of the RS flip-flop FF is held at a high level almost throughout a period to raise the charging voltage VC1 of the charging circuit almost linearly, so variation in accumulation time is made less than the period T even if the charging and discharging characteristics vary with temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a smoke detector that has a predetermined accumulation time from when it detects smoke to when it generates a smoke detection signal.

(Background Art 3) In the conventional scattering type rechargeable smoke detector, as shown in FIG. 5, a switching thyristor SCR is connected between the sensor terminal and the common terminal C. The voltage between the common terminals C is made constant by the power supply circuit, and power is supplied to each circuit.

Then, the oscillation circuit O3 generates a pulse-like output V^ with a period of T seconds (3 to 5 seconds) as shown in FIG. 6(A), causes the light emitting element LED to emit light intermittently, and It is designed to irradiate light.

The light receiving element PD receives the scattered light caused by the smoke particles X that have entered the smoke sensing area, and causes a pulsed current having an amplitude proportional to the smoke density to flow.

Increase 1! The circuit AP amplifies the current output of the light receiving element PD and outputs a voltage v! This amplifier circuit AP has a threshold value, and as shown in FIG. 6(B), when the smoke density is lower than a predetermined value, the output vB
When the current output of is smaller than a predetermined value, it is zero, and when the smoke density exceeds a predetermined value, the output VB is
This will occur in a pulsed manner with a slightly delayed timing.

The monostable multivibrator MM detects smoke by adding the AND output VAR (Fig. 6(C)) from the AND circuit AN of the output V^ of the oscillation circuit O3 and the output vB of the amplifier circuit AP as a trigger input. Only when the smoke density in the area exceeds a predetermined value, the output VM as shown in Figure 6 (D)
(a metastable period of seconds (t<<T)).

Therefore, in the charging circuit CG consisting of the transistors TR, rS and R1, R2° capacitor CI, the transistor TR is turned on only when the output vM of the monostable multivibrator MM is at a high level, and the R is turned on during the period when the output vM is at a high level.
It is charged with a time constant of 1·CI, and discharged with a time constant of R2·C1 while the output vM is at a low level. In this case, the discharging time constant (R2・C) is the charging time constant (R+
・C+), and the charging voltage VCI is set higher than the 6th
As shown in Figure (g), during the period when the smoke density exceeds a predetermined value, the smoke density gradually rises while repeating large rises and falls due to charging and discharging.

When the charging voltage VC+ becomes higher than the gate voltage Vc set by resistors R3 and R4, the voltage responsive switching element (programmable unijunction transistor) PUT becomes conductive and gives a trigger signal to the thyristor SCR, causing the thyristor SCR to This results in a short circuit between the sensor terminal and the common terminal C. In this case, the accumulation time from when smoke of a predetermined concentration or higher is detected in the smoke detection area until the smoke detection output is generated (thyristor SCR is turned on) is approximately 3
．． It becomes 2T seconds.

However, in such conventional photoelectric smoke detectors, the storage time varies greatly (±T seconds) due to variations in the charging and discharging characteristics of the capacitors C+ and R1+R2 due to temperature changes. This is because the charging voltage VCI rises while changing considerably in high and low levels due to charging and discharging.

[Purpose of the invention]

An object of the present invention is to provide a smoke detector that can reduce the range of variation in storage time.

[Disclosure of the Invention] The smoke detector of the present invention includes an oscillation circuit that periodically generates pulses, a light emitting element that intermittently irradiates a smoke detection area with the output of this oscillation circuit, and a light emitting element that intermittently irradiates a smoke detection area with light. a light receiving element that receives light irradiated from the element to the smoke sensing area;
an amplifier circuit that generates an output synchronized with the output of the oscillation circuit when the output of the light-receiving element is added to the smoke that has entered the smoke sensing area exceeds a predetermined concentration; A flip-flop that is reset by the output of the oscillation circuit, a charging circuit that switches between charging and discharging depending on the output of the flip-flop, and an output that generates a smoke detection output when the output level of the charging circuit exceeds a threshold value. The present invention is characterized by having a configuration including a circuit.

In this way, the flip-flop is powered by the output of the amplifier circuit and reset by the output of the oscillation circuit, and the output of this flip-flop switches charging and discharging of the charging circuit, so that the output voltage of the charging circuit exceeds the threshold. Since the output circuit generates a smoke detection output when smoke exceeds a predetermined concentration in the smoke detection area, the output of the charging circuit increases almost linearly, and charging/discharging is interrupted due to temperature fluctuations. Even if the characteristics vary, the variation in storage time can be made smaller than the output cycle of the oscillation circuit.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 2. As shown in Fig. 1, this scattering type photoelectric smoke detector has a switching SCR connected between the sensor terminal and the common terminal C, and a SCR for switching between the sensor terminal and the common terminal C. The voltage is made constant by the power supply circuit and is supplied to each circuit.

Then, the oscillation circuit O8 generates a pulse-like output vA with a period of T seconds (3 to 5 seconds) as shown in FIG. It is designed to emit light.

The light-receiving element PD receives the scattered light caused by the smoke particles X that have entered the smoke sensing area, and causes a pulse-like current having a width of 11 proportional to the smoke density to flow.

The amplifier circuit AP amplifies the current output of the light receiving element PD and generates the voltage output VB, but this amplifier circuit AP has a threshold value, and as shown in FIG. 2(B), the output v11 is When the smoke density is smaller than a predetermined value, that is, when the current output of the light receiving element PD is smaller than the predetermined value, it is zero, and when the smoke density reaches the predetermined value, the output vI] of the oscillation circuit O3 is zero.
This occurs in a pulse-like manner at a timing slightly later than A.

The set-priority type RS flip-flop FF is configured such that the AND output VAB (Fig. 2 (C)) from the AND circuit AN of the output V^ of the oscillation circuit O8 and the output vB of the amplifier circuit AP is added as the set manual power S. , by adding the output V^ of the oscillation circuit O5 as the reset human power R,
The second T is activated only when the smoke density in the smoke detection area exceeds a predetermined value.
I! As shown in J(D), the output VA of the AND circuit AN
The output remains at the same high level for T' seconds (T'#T) from the rising edge of B to the rising edge of the output V^ of the oscillation circuit OS, and remains at a low level for a very short period from the rising edge of the output V^ to the rising edge of the output VAB. Q will be generated. Note that the cent priority type RS flip-flop FF is used because the output vA
When the rising edge of FF and the rising edge of output VB appear almost at the timing when the FF is opened, the RS flip flop is reliably
This is to raise the output Q of the sensor to a high level so that smoke is detected.

Therefore, transistors TR, Ill, anti-R1, R2
゜In the charging circuit CG consisting of the capacitor CI, the transistor TR is turned on only when the output Q of the RS flip-flop FF is at a high level, and when the output Q is at a high level, the transistor TR is turned on.
is charged with a time constant of C, and during the period when the output Q is at a low level, R
It will be discharged with a time constant of 2.CI. in this case,
The discharge time constant (R2・CI) is the charging time constant (Mutsu1・C−
The charging voltage VCI is set larger than that shown in Fig. 2 (E).
As shown in , the smoke concentration increases almost linearly during the period in which it exceeds a predetermined value. This is because the charging period occupies most of the time, there is almost no discharging period, and there is almost no voltage drop due to discharging. In addition,
When the smoke density decreases, the amplifier circuit AP outputs a pulse-like signal W.
e is no longer generated, the RS flip-flop FF is not sent, the output Q remains at a low level, and the voltage VC
I will decrease with a time constant of R2.0 kan.

When the charging voltage VCI becomes higher than the gate voltage vG set by resistors R3 and R4, the voltage responsive switching element (programmable unijunction silane transistor) PUT becomes conductive and gives a trigger signal to the thyristor SCR, making the thyristor SCR conductive. Then short-circuit between the sensor terminal and the common terminal C. In this case, the accumulation time from when smoke of a predetermined concentration or higher is detected in the smoke detection area until the smoke detection output is generated (thyristor SCR is turned on) is approximately 3
．． It will be 5T seconds.

In this way, this embodiment uses the RS flip-flop FF instead of the conventional monostable multi-bibreak MM, and the RS flip-flop FF is activated at the rise of the output VB of the amplifier circuit AP (the rise of the output VAB of the AND circuit AN). Since the RSS flip-flop 1F is reset at the rise of the output of the oscillation circuit O3, when the smoke density exceeds a predetermined value, the output Q of the RS clip-flop FF is
is kept at a high level for most of the period, and the charging voltage VCI of the charging circuit CG is increased almost linearly. Therefore, even if there are fluctuations in the charging/discharging characteristics due to temperature fluctuations, the fluctuations in the storage time can be compared with the period T. It can be made smaller.

Another embodiment of the invention will be described based on FIGS. 3 and 4. In this scattering type photoelectric smoke detector, as shown in Fig. 3, the AND circuit AN in Fig. 1 is omitted, and the output vB of the amplifier circuit AP is directly applied as cent human power S to the RSS flip-flop F. The rest of the structure is the same as that shown in FIG. In this case, the timing of the rise of the output V of the amplifier circuit AP and the AND circuit AN
Since the timing of the rise of the output ■^B is the same if the operation delay time of the AND circuit AN is ignored, the RS flip-flop FF is set and reset in the same way as in Fig. 1, and the timing shown in Fig. 4 ( C), the charging circuit C
The output VCI of G, as shown in FIG. 4(D), is exactly the same as that in FIG. 2(E). In addition, Fig. 4 (A), (
B) shows the outputs v^ and vB, respectively, and the second WJ (A)
, correspond to the waveforms in (B), respectively.

The effects of this embodiment are similar to those of the previous embodiment.

In the above embodiment, a scattering type photoelectric smoke detector has been described, but the present invention can be applied to a dimming type as well.

〔Effect of the invention〕

In the smoke detector of the present invention, the flip-flop is powered by the output of the amplifier circuit and reset by the output of the oscillation circuit, and the output of the flip-flop switches charging and discharging of the charging circuit, so that the output voltage of the charging circuit is Since the output circuit generates a smoke detection output when the threshold value is exceeded, when smoke exceeding a predetermined concentration enters the smoke detection area, the output of the charging circuit increases almost linearly, and the temperature Even if the charging/discharging characteristics change due to fluctuations, the fluctuations in the storage time can be made smaller than the output cycle of the oscillation circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a photoelectric smoke detector according to one embodiment of the present invention, FIG. 2 is a timing diagram of each part of FIG. 1, and FIG. 3 is a photoelectric smoke detector according to another embodiment of the present invention. 4 is a timing diagram of each part of FIG. 3, FIG. 5 is a circuit diagram of a conventional rechargeable smoke detector, and FIG. 6 is a timing diagram of each part of FIG. 5. O8...Oscillation circuit, LED...Light emitting element, PD...
・Photodetector, AP...Amplification circuit, FF...Set priority RS flip-flop, CG...Charging circuit, P
UT...Voltage responsive switching element (output circuit), S
CR...Thyristor (output circuit) -V Procedural amendment (Originally dated March 8, 1985)

Claims (1)

[Claims] an oscillator circuit that periodically generates pulses; a light emitting element that intermittently irradiates light onto the smoke sensing area by applying the output of the oscillator circuit; and a light emitting element that receives the light irradiated onto the smoke sensing area from the light emitting element. a light receiving element; an amplifier circuit that generates an output synchronized with the output of the oscillation circuit when the output of the light receiving element is added to the smoke that has entered the smoke sensing area exceeds a predetermined concentration; and the output of the amplifier circuit; A flip-flop that is set and reset by the output of the oscillation circuit, a charging circuit that switches charge/discharge depending on the output of this flip-flop, and a smoke detection output when the output level of this charging circuit exceeds a threshold value. A smoke detector equipped with an output circuit that generates