JP2759478B2 - Photoelectric smoke detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a two-signal photoelectric smoke detector incorporating a signal processing unit having a novel configuration.

[Prior Art] As shown in FIG. 4, a smoke detector of this type includes a light emitting room A having a light emitting element provided in a smoke detecting room C having a maze structure.
And a light receiving chamber B provided with a light receiving element. The light emitting chamber A and the light receiving chamber B are arranged at positions where the light receiving element does not directly receive the light emitted from the light emitting element. Light is detected by a light receiving element, and a signal corresponding to smoke density is obtained.

By the way, such a photoelectric smoke detector is generally of a one-signal type in which the sensitivity setting is fixed, but operates by automatically switching the sensitivity between two stages of high sensitivity and low sensitivity. There are two-signal types.

FIG. 5 shows a basic circuit configuration of a two-signal type smoke detector.

The smoke detector has a high-sensitivity signal input terminal L, a low-sensitivity signal input terminal DL, and a common terminal C.
It has switching elements SCR1 and SCR2 for low sensitivity.

The output from the constant voltage circuits 1 and 2 is connected to a diode OR constituted by connecting two diodes D1 and D2 to a light emitting element driving circuit 10 which intermittently drives an LED and outputs a light emission pulse into a smoke sensing chamber. The level of the output voltage of the two constant voltage circuits 1 and 2 is set to a higher level on the high sensitivity side than on the low sensitivity side.

In such a smoke detector, when smoke flows into the smoke sensing room, the light emission pulse output into the room by intermittent driving of the LED is scattered by the smoke, and the scattered light at this time is PIN
The light is converted into an electric signal by a light receiving element PD such as a photodiode, amplified by an amplifier circuit 32 to a certain level, and then sent to a signal processing circuit 30 for storage.

The signal processing circuit 30 is provided with trigger generation circuit sections 31 and 32 provided for high sensitivity and low sensitivity, and a capacitor C connected to PUTs 1 and 2 constituting the trigger circuit sections 31 and 32.
1, C2 is charged as long as the PIN photodiode PD is outputting a signal.

By the accumulation operation by such charging, the capacitor
When the voltages of C1 and C2 reach a predetermined level, PUT1 and PUT2 are turned on, the signal processing circuit 30 outputs a trigger signal, and the switching elements SCR1 and SCR2 which have received the trigger signal are turned on, and the detector issues an alarm. I do.

Here, since the output level of the constant voltage circuit 1 is set higher than the output level of the constant voltage circuit 2, the terminal L-
When a voltage is simultaneously supplied between C and DL-C, a high voltage from the constant voltage circuit 1 is supplied to the light emitting element drive circuit 10 by the operation of the diode OR circuit to strongly drive the LED. After the high-sensitivity operation is completed in this manner, the switching element SCR1 is turned on to short-circuit between the LC and the light-emitting element driving circuit 10. Is supplied, the driving of the LED is weakened and the sensitivity of the sensor is automatically reduced. In the signal processing unit 30, when the PIN photodiode PD receives scattered light due to smoke, the transistor Tr is turned off, and the two capacitors C1 and C2 connected to the PUT1 and PUT2 are simultaneously charged. Since the time constant is set smaller than the charging time constant of the capacitor C2, PUT1 turns on earlier than PUT2, and
When there is no output from the PIN photodiode PD, the transistor Tr is turned on, the capacitors C1 and C2 are discharged, and return to the initial state.

In this way, in a state where the sensor has low sensitivity, the signal processing circuit 30 performs the accumulation operation again, and when the switching element SCR2 is turned on, the terminal DL-C is short-circuited,
The smoke detector emits again.

FIG. 6 shows an internal circuit of the one-signal type smoke detector. The input signal terminals are two terminals of LC, and the power supply voltage supplied to the light emitting element drive circuit 10 is also one. PU supplied via the constant voltage circuit 20 and constituting the signal processing circuit 30
When the capacitor C connected to T is charged by the output of the PIN photodiode PD and the PUT is turned on to output a trigger signal, the switching element SCR connected between L and C is turned on to issue an alarm. I have. Note that 33
Amplifies the photocurrent from the PIN photodiode PD, which has been scattered by smoke, to a certain level.

By the way, as can be understood from these examples, the signal processing circuits used in the conventional smoke detector are different in the number of trigger circuits and the number of signal output terminals between the one-signal type and the two-signal type. Therefore, it is necessary to configure different types of signal processing circuit units according to the type of smoke detector.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and has a common signal processing unit used for one-signal type and two-signal type smoke detectors. It is an object of the present invention to provide a smoke detector with reduced labor.

Means for Solving the Problems According to the photoelectric smoke detector of the present invention according to claim 1 proposed to achieve the above object, a light emitting pulse generated by intermittently driving a light emitting element emits smoke. The light is output to the sensing chamber, and the light scattered by the smoke of the light emission pulse is received by the light receiving element and converted into an electric signal. The electric signal is accumulated, and when the electric signal reaches a predetermined level, the first switching for high sensitivity is performed. A first power input terminal for inputting a driving power supply for a light emitting element, and a driving circuit for an internal circuit in a photoelectric smoke detector which emits an element and then issues a second switching element for low sensitivity. A drive amplifier circuit section having a second power input terminal for inputting power, a first output terminal, outputting a pulse signal of a constant cycle for intermittently driving the light emitting element, and a signal input terminal for connecting the light receiving element. Input from the light receiving element Converting the photocurrent into a voltage signal, integrating the signal, integrating and comparing with a reference level, and outputting a trigger signal. The signal processing unit has a built-in storage circuit unit having a second output terminal. The first and second power supply input terminals are connected to a high-sensitivity signal input terminal and a low-sensitivity signal input terminal, respectively.
Connected via an OR circuit, the first output terminal is connected to the light emitting element, and the second output terminal is connected to a trigger circuit of the first and second switching elements. The trigger switching circuit is connected to a switching circuit, and controls switching of the second output terminal to a trigger circuit of the first and second switching elements according to a magnitude of an output voltage of the diode OR circuit. And

According to a second aspect of the present invention, in the photoelectric smoke detector according to the first aspect, the diode OR circuit is further connected to a constant voltage circuit, and the constant voltage circuit is connected to the signal processing via a different resistor. A current switching circuit connected to the first and second power supply input terminals of the unit and for switching a current flowing to the constant voltage circuit light emitting element, wherein the current switching circuit comprises the first and second constant voltage circuits; The current flowing through the light-emitting element is switched and controlled by the output voltage of the photoelectric smoke sensor according to the present invention.
The output voltage of the OR circuit is directly supplied to switch the current flowing to the light emitting element. The photoelectric smoke detector according to the present invention described in claim 4 is configured as described in claims 1 to 3, The voltage compensating circuit is configured by connecting the diode OR circuit to the first power supply input terminal of the signal processing unit via a resistor, and connecting a Zener diode to the resistor in parallel. In the photoelectric smoke detector of the present invention described in (1), the signal processing unit is configured as a one-chip IC circuit.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the configuration of an internal circuit when a one-signal type smoke detector is configured.
A constant current circuit 1 is provided.
Is output from the constant voltage circuit 2 and the first
L which is input to the power supply input terminal Vcc
The ED has its cathode connected to the collector of a transistor TR as a driving element connected to the first output terminal of the signal processing unit 4 and its anode connected to the signal processing unit 4.
Are connected in parallel via a resistor R to the first power supply input terminal of

Here, the signal processing unit 4 has a second power supply input terminal VDD serving as a power supply to an internal circuit of the unit 4,
The terminal VDD is supplied with a constant level voltage from the constant voltage circuit 2 described above.

The signal input terminal IN of the signal processing unit 4 is connected to a PIN photodiode PD serving as a light emitting element, and the second output terminal OUT2 of the signal processing unit 4 is connected to the signal input terminal L
It is connected to the gate terminal of the switching element SCR provided between -C.

FIG. 1a shows a configuration of an internal circuit of the signal processing unit.

Inside the signal processing unit 4, there are provided a reference pulse generating circuit 46 for generating a reference pulse for intermittently driving the light emitting element at a constant period, and a driving circuit 47 for driving the light emitting element according to the pulse output from this circuit. The power amplifier for driving the light emitting element is input through the first power input terminal VCC, and the light emitting element is driven by a driving pulse from the driving circuit 47. I have.

In addition, the signal processing unit 4 has a storage circuit unit. In this storage circuit unit, the signal input from the signal input terminal IN is obtained by converting the photocurrent into a voltage signal by the IV converter 41. Thereafter, the signal is amplified to a certain level by the amplifier 42 and enters the integrator 43, where it is integrated. The signal thus integrated is further input to the comparator 44 in the determination circuit 45, where the level of the reference signal is determined. Is done.

In such a configuration, the signal processing unit 4
In order to intermittently drive the LED, a pulse signal is output at a constant cycle from the first output terminal OUT1, and from the signal input terminal IN,
After receiving and integrating the photocurrent transmitted from the PIN photodiode PD, the level is compared with a reference signal. When the integrated output reaches the reference level, a trigger signal is output.

VCC and VDD are the first and second power supply input terminals, VSS
Is a common terminal.

Such a signal processing unit may have a one-block configuration combining known circuits, or may be configured as a one-chip IC circuit.

FIG. 2 shows a configuration of an internal circuit when a two-signal type smoke detector is configured.

The high-sensitivity and low-sensitivity input signal terminals L and DL are provided with a first constant voltage circuit 1a and a second constant voltage circuit 1b whose output voltage is set to a level lower than that of the first constant voltage circuit 1a. Further, at the output terminals of these two constant voltage circuits 1a and 1b, there are provided diode OR circuits in which two diodes D1 and D2 are combined by commonly connecting cathodes.

Also, the first power supply input terminal VCC of the signal processing unit 4
A constant voltage circuit 2 connected to the output side of the diode OR circuit is connected via resistors R1 and R2 to the second power input terminal VDD and a second power input terminal VDD to supply a power voltage.
The first output terminal OUT1 is connected to a transistor TR to which an LED as a light emitting element is connected as a driving element.

Further, a PI photodiode PD as a light receiving element is connected to the signal input terminal IN of the signal processing unit 4, and the first and second constant voltage circuits 1a, 2a are connected to the second output terminal OUT2 of the signal processing unit 4. 1b. The trigger signal output from the second output terminal OUT2 is provided to the high-sensitivity input signal terminal L side and the low-sensitivity input terminal DL side. It is connected to a trigger switching circuit 3B having switching contacts SW3 and SW4 for switching and supplying to the trigger circuits of the first and second switching elements SCRL and SCRDL provided.

Here, the voltage determination unit 3A determines the supply voltage of the low-voltage circuits 1a and 1b, and when the voltage is supplied from both of the low-voltage circuits 1a and 1b, closes the contact SW3 of the trigger switching circuit 3B, SW4 is opened, and when voltage is supplied from one of the constant voltage circuits 1a, 1b, the corresponding contact SW3, S
Close any of W4. For example, if there is only an output from the constant voltage circuit 1a, the contact SW3 is closed and the constant voltage circuit 1B
If there is only an output from the switch, the contact SW4 is closed.

The LED as one light emitting element is connected to a current switching circuit having switching contacts SW1 and SW2 for switching resistance values RL and RDL, and is connected to a first power input terminal VCC of the signal processing unit 4. , Is supplied with power from the constant voltage circuit 2,
The contacts SW1 and SW2 of the current switching circuit are switched by the above-described voltage determining unit 3A, and the contacts SW3 and SW1, SW4 and SW2 are closed in conjunction with each other, and the resistor RL having a value smaller than the resistor RDL is selected. ing.

 Next, the operation of the two-signal smoke detector will be described.

When power is simultaneously supplied to the high-sensitivity signal input terminal L and the low-sensitivity signal input terminal DL, the output voltage of the constant voltage circuit 1a is set to a higher level than the output voltage of the constant voltage circuit 1b. As a result, the output of the constant voltage circuit 1a is supplied to the constant voltage / constant current circuit 2, and the first and second power supply input terminals VCC and VDD of the signal processing unit 4 are connected to a resistor R.
1, the output of the constant voltage / constant current circuit 2 is supplied via R2.

When the voltage determination unit 3A determines that there is an output from both the constant voltage circuits 1a and 1b, the trigger switching circuit 3B closes the contact SW3 and closes the contact SW1 of the current switching circuit 3C.

As a result, the current flowing to the LED when the transistor TR is turned on increases, and at the same time, only the first switching element SCRL on the high sensitivity side can be turned on, so that the trigger signal is output from the second output terminal OUT2 of the signal processing unit 4. When output, the resistor R3 is connected to the gate of the first switching element SCRL.
, The SCRL is turned on to short-circuit the terminals L and C (high sensitivity operation).

When a short circuit occurs between LC and LC in this way, the voltage discriminating unit 3A
Is supplied with the voltage only from the constant voltage circuit 1b, the trigger switching circuit 3B closes the contact SW4 and the current switching circuit 3C closes the contact SW2.

As a result, the current flowing through the LED when the transistor TR is turned on decreases, and at the same time, the low-sensitivity switching element SCRDL
Only one can be turned on.

When the trigger signal is output from the second output terminal OUT2 of the signal processing unit 4, the trigger signal is sent to the gate of the second switching element SCRDL on the low sensitivity side via the resistor R4. Turn on the terminal DL-C
Short circuit between them (the above is the low sensitivity operation).

The above operation is shown in a) to g) of FIG.
Indicates a voltage between terminals L and C and a voltage between DL and C.

FIG. 3 shows the configuration of an internal circuit of another example of the two-signal smoke detector, and FIG. 3a is a time chart showing the operation of this example.

The feature of such a two-signal smoke detector is that the signal processing unit 4 described above is built in and is common to that of FIG. 2, but in the trigger switching circuit 5 having the changeover switch SW, The voltage level from the constant voltage / constant current circuits 4a and 4b input through a diode OR circuit configured by connecting two diodes D1 and D2 (the voltage level of the two constant voltage / constant current circuits 4a and 4b). The output voltage 4a is higher than the output voltage 4b), and the contacts a and b are switched.

In addition, the LED that is a light emitting element uses the operation of the diode OR circuit to supply the output voltage of the constant voltage / constant current circuits 4a and 4b via the resistors R1 and R2, and the current that flows when the LED is driven is also supplied. At the same time, the sensitivity is switched by increasing or decreasing.

Reference numeral 6 denotes a constant voltage circuit, and a voltage compensating circuit formed by connecting a Zener diode ZD in parallel via a resistor R5 is provided at a first power input terminal VCC of the signal processing unit 4. This prevents the power supply voltage from fluctuating at the first power input terminal when the LED is driven.

[Effects of the Invention] According to the present invention, one common signal processing unit is used.
Since a signal-type smoke detector and a two-signal smoke detector can be configured, the manufacturing cost of a small-quantity two-signal smoke detector can be reduced and the assembly can be facilitated.

Further, when the signal processing unit is configured by an IC circuit, the space can be reduced, and the sensor itself can be reduced in size and weight.

[Brief description of the drawings]

FIG. 1 is an embodiment of the present invention, showing the configuration of an internal circuit of a one-signal type smoke detector, FIG. 1a is a schematic configuration of a signal processing unit, and FIG. 2a is a time chart showing the operation of the smoke detector, FIG. 3 is a structural diagram of an internal circuit of another example of a two-signal type smoke detector, and FIG. 3a is its operation. FIG. 4 is an explanatory view of the structure of a smoke detecting chamber of a smoke detector, FIG. 5 is a circuit configuration diagram of a conventional two-signal smoke detector, and FIG. 6 is a conventional one-signal smoke detector. FIG. 3 is a circuit configuration diagram of the container. [Explanation of Signs] LED ... Light emitting element VCC ... First power input terminal VDD ... Second power input terminal OUT1 ... First output terminal OUT2 ... Second output terminal IN ... Signal input terminal VSS: Common terminal 4: Signal processing unit 2, 4a, 4b: Constant voltage / constant current circuit 1a, 1b, 6: Constant voltage circuit SCRL: First switching element SCRDL: Second switching element L: High-sensitivity signal input terminal DL: Low-sensitivity signal input terminal D1, D2: Diode OR circuit 3A: Voltage discriminator 3B, 5: Trigger switching circuit 3C: Current switching circuit

Claims (5)

(57) [Claims] A light emitting pulse generated by emitting light by intermittently driving a light emitting element is output to a smoke sensing chamber, and light scattered by the smoke of the light emitting pulse is received by a light receiving element and converted into an electric signal. The photoelectric smoke detector, which accumulates and emits a first switching element for high sensitivity when a predetermined level is reached, and then issues a second switching element for low sensitivity, emits light. A first power input terminal for inputting driving power for the element, a second power input terminal for inputting driving power for the internal circuit, and a first output terminal, and a pulse having a constant period for intermittently driving the light emitting element It has a drive amplifier circuit section that outputs a signal, and a signal input terminal that connects the light-receiving element. After converting the photocurrent input from the light-receiving element into a voltage signal, integrating the voltage signal, comparing it with a reference level, and determining the trigger signal, The second output that outputs And a signal processing unit having a built-in storage circuit unit having a power terminal. The first and second power input terminals are connected to a high-sensitivity signal input terminal and a low-sensitivity signal input terminal, respectively, and have different levels. The first and second constant voltage circuits for outputting a voltage are connected via a diode OR circuit, the first output terminal is connected to the light emitting element, and the second output terminal is connected to the first and second constant voltage circuits. 1, a trigger switching circuit for switching connection to a trigger circuit of a second switching element. The trigger switching circuit connects the second output terminal to the second output terminal depending on the output voltage of the diode OR circuit. 1. A photoelectric smoke detector configured to control switching to a trigger circuit of a second switching element. 2. The diode OR circuit according to claim 1, further comprising a constant voltage circuit connected to the diode OR circuit.
The constant voltage circuit further includes a current switching circuit connected to the first and second power supply input terminals of the signal processing unit via different resistors and switching a current flowing to the constant voltage circuit light emitting element. The photoelectric smoke sensor is configured such that the switching circuit switches and controls the current flowing to the light emitting element according to the output voltage from the first and second constant voltage circuits. 3. The photoelectric smoke detector according to claim 1, wherein the current switching circuit is configured to control the switching of the current flowing to the light emitting element by directly supplying the output voltage of the diode OR circuit. 4. The signal processing unit according to claim 1, wherein the first power input terminal of the signal processing unit is connected to the diode OR circuit via a resistor, and a zener diode is connected to the resistor in parallel. Photoelectric smoke detector that constitutes a voltage compensation circuit. 5. The photoelectric smoke detector according to claim 1, wherein the signal processing unit is configured as a one-chip IC circuit.