JP2009099118A - Smoke sensor and electronic equipment provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a smoke sensor capable of avoiding incorrect detection caused by element deterioration or a disturbance such as temperature change, and applicable to a reflection type. <P>SOLUTION: In the smoke sensor, a signal processing circuit 16A outputs a smoke detection signal on the basis of a difference between a first output signal outputted by a first amplifier 5, and a second output signal output by a second amplifier 6. When a first photo detector 2 receives a disturbance such as temperature change or element deterioration, a second photo detector also receives the disturbance such as the temperature change or the element deterioration. Accordingly, by using the smoke detection signal based upon the difference between the first output signal by a first photoreception signal and the second output signal by a second photoreception signal, fluctuation factors due to a disturbance such as temperature change and element deterioration are counterbalanced, and incorrect detection can be avoided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a smoke sensor, and more specifically, to a smoke sensor that detects smoke concentration by projecting light onto smoke and receiving reflected light from the smoke, and an electronic apparatus including the smoke sensor.

  Conventionally, in a smoke sensor, light is emitted from a light-emitting element that is a light source to the smoke that flows in, and the light reflected by the smoke that has entered the light-receiving element causes the light-receiving element to output a minute light-receiving signal. To do. The smoke sensor amplifies a minute light reception signal output from the light receiving element by an amplification circuit, and smoke is emitted when an output signal output from the amplification circuit reaches a determination value corresponding to a predetermined smoke density range. A smoke detection signal indicating detection is output.

  However, even in the same smoke density range, the output signal obtained by amplifying the light reception signal fluctuates due to a change in the amount of light emission caused by deterioration of an LED (light emitting diode) constituting the light emitting element or a temperature change. Due to the fluctuation of the output signal, there is a case where a false detection of outputting the smoke detection signal may occur even if the smoke that has flowed in is outside the smoke density detection range set in advance.

  In view of this, various methods have been proposed in order to avoid erroneous detection by avoiding fluctuations in the output signal (light reception signal) due to disturbance factors other than smoke.

  That is, in the first example, by adding a thermistor resistor to the drive circuit that drives the light emitting element and correcting the temperature of the drive output of the drive circuit, the amount of light emitted from the light emitting element varies depending on the temperature change. It is preventing. As a result, the output signal (light reception signal) is prevented from fluctuating due to temperature changes, thereby preventing erroneous detection (see Japanese Patent Application Laid-Open No. 58-39552).

  In the second example, the gain of the amplifier circuit is temperature-corrected by adding a thermistor resistor to a resistor unit that determines the gain of an IC (integrated circuit) constituting the amplifier circuit. This prevents the output signal from fluctuating due to the temperature characteristics of the amplifier circuit.

  In addition, the third example includes a monitor light-receiving element that monitors fluctuation (decrease) in the amount of light emission due to deterioration of the light-emitting element (LED) separately from the detection light-receiving element on which the light reflected by the smoke enters. The light-receiving signal of the monitor light-receiving element is fed back to the drive circuit of the light-emitting element to correct the light emission amount of the light-emitting element (see Japanese Patent Application Laid-Open No. 59-5398).

  In the fourth example, a light receiving element for detection that receives light emitted from a light emitting diode (light source) through a smoke detection area, and a reference light that receives light emitted from the light emitting diode without passing through the smoke detection area. A differential amplifier amplifies the difference between the received light signal from the light receiving element for detection and the received light signal from the light receiving element for reference, and uses the amplified signal as an output signal (Patent Document) 3 (see JP-A-60-33035).

  By the way, in the first and second examples, the temperature correction by the thermistor resistance is possible, but it is impossible to cope with the fluctuation of the light emission amount due to the deterioration of the light emitting diode. In the first and second examples, if the thermistor resistance selected for temperature correction is not appropriate, temperature correction may not be performed sufficiently.

  In the third example, the light emission amount of the light emitting diode is monitored by the light receiving element for monitoring, so that the light emission amount reduction due to deterioration of the light emitting diode can be corrected. However, temperature correction cannot be performed, and the light receiving element for monitoring In addition, since the amplifier is required, the number of parts is increased and the configuration is complicated.

  In the fourth example, the light emitted from the light emitting diode is attenuated by passing through the smoke detection region, and the light emitted from the light emitting diode is received by the light receiving element for detection. is there. In this light reduction type smoke sensor, when no smoke is present in the smoke detection region, the light receiving element for detection directly receives the light emitted from the light emitting diode. On the other hand, the reference light receiving element directly receives the light emitted from the light emitting diode in the same manner whether smoke is present or not present in the smoke detection region. Therefore, in this fourth example, when smoke flows into the smoke detection area, the difference between the light receiving signal output from the light receiving element for detection and the light receiving element output from the light receiving element for reference is large and large. An output signal can be obtained.

  On the other hand, when the configuration of the light receiving element for detection and the light receiving element for reference as in the fourth example is adopted for the reflective smoke sensor, there is no reflected light due to the smoke when there is no smoke flowing in. The light receiving signal output from the light receiving element for detection is small. On the other hand, the reference light receiving element receives the light emitted from the light emitting diode without regard to the presence or absence of smoke. Therefore, when there is no inflowing smoke, the light reception signal by the reference light receiving element becomes too large compared to the light reception signal by the detection light receiving element, and the output signal of the differential amplifier is saturated, and the differential amplifier In some cases, it becomes impossible to detect the difference between the two received light signals with the output signal. On the other hand, when smoke flows in, the light reception signal output from the light receiving element for detection that receives the reflected light from the smoke increases, so the difference between the two light reception signals decreases. As the amount of smoke inflow increases, the difference between the two light reception signals approaches zero. Further, when the amount of smoke inflow increases, the light reception signal output by the light receiving element for detection further increases. The difference between the two received light signals starts increasing through zero. For this reason, a case where the output signal of the differential amplifier becomes the same when there is no smoke and when there is smoke occurs, and smoke detection cannot be performed correctly. In addition, if the light emission amount of the light emitting diode, the amplification factor of the amplifier, and the like are adjusted in accordance with the reference light receiving element, the smoke detection accuracy is reduced.

In general, a smoke sensor generally determines whether the output signal from the light receiving element and the amplifier exceeds or does not exceed the detection level with respect to the pulsed light emitted from the light emitting element at every sampling time. However, the determination by the smoke sensor is affected by noise due to thermal noise, power supply noise, and external noise of the amplifier itself, in addition to the environment such as ambient temperature and aging of the LED that constitutes the light emitting element. Therefore, there is a high possibility of erroneous detection in the determination based on only a single measurement result of a single output signal.
Japanese Utility Model Publication No. 58-39552 JP 59-5398 A JP-A-60-33035

  SUMMARY OF THE INVENTION An object of the present invention is to provide a smoke sensor that can avoid a false detection due to disturbance such as a temperature change or element degradation and can be applied to a reflection type.

  Another object of the present invention is to provide a smoke sensor capable of improving smoke detection accuracy and performing stable smoke detection without erroneous detection.

In order to solve the above problems, a smoke sensor of the present invention includes a smoke detection unit into which smoke is introduced,
A light emitting element that emits light toward the smoke detector;
A first light receiving element that receives scattered light emitted from the light emitting element and scattered by the smoke in the smoke detector;
A second light receiving element that receives light emitted from the light emitting element without passing through the smoke detector;
A first amplifier for amplifying a first light receiving signal output from the first light receiving element;
A second amplifier for amplifying a second light receiving signal output from the second light receiving element;
And a signal processing unit that outputs the smoke detection signal based on a difference between the first output signal output from the first amplifier and the second output signal output from the second amplifier. It is said.

  According to the smoke sensor of the present invention, the signal processing unit is based on the difference between the first output signal output from the first amplifier and the second output signal output from the second amplifier. Output smoke detection signal. Here, when a disturbance such as a temperature change or deterioration of the element occurs in the first light receiving element, a disturbance such as the temperature change or deterioration of the element also occurs in the second light receiving element. Therefore, according to the smoke detection signal based on the difference between the first output signal based on the first light reception signal and the second output signal based on the second light reception signal, fluctuation due to disturbance such as temperature change or deterioration of the element Factors are offset and false detection can be avoided.

  In addition, the first light receiving signal by the first light receiving element for detecting the smoke of the smoke detecting unit and the second light receiving signal by the second light receiving element that is not affected by the smoke of the smoke detecting unit are different from each other. 1 and input to the second amplifier. Therefore, when there is no smoke in the smoke detector, the amplification factors of the first and second amplifiers are independently set according to the first and second light receiving signals output from the first and second light receiving elements. Can be set. Therefore, the present invention can also be applied to a reflection type smoke sensor.

  In one embodiment, the first output signal from the first amplifier and the second output signal from the second amplifier are selectively input and the first and second smoke sensors are selectively input. An amplifying unit for amplifying the output signal and outputting it to the signal processing unit.

  In the smoke sensor of this embodiment, since the first output signal and the second output signal are provided with a common amplifier, the first and second output signals are each provided with a different amplifier. Thus, variations in signals due to the amplification unit can be suppressed. For example, fluctuations in the amplification factor of the amplification unit due to a temperature change affect the first and second output signals in the same manner, and signal variations caused by the amplification unit can be suppressed.

  Moreover, the smoke sensor of one Embodiment is provided with the switch part which inputs either one of the said 1st output signal or the said 2nd output signal into the said amplifier part.

  In the smoke sensor of this embodiment, the switching unit inputs either the first output signal or the second output signal to the amplification unit. Therefore, the first timing at which the first output signal obtained by amplifying the first light reception signal by the first light receiving element is input to the amplification unit and the second light reception signal by the second light receiving element are amplified. The second output signal can be set to be different from the second timing at which the output signal is input to the amplifying unit. Therefore, for example, by performing control to reduce the light emission amount of the light emitting element at the second timing as compared with the light emission amount of the light emitting element at the first timing, the above-described operation is performed at the second timing. It is possible to avoid saturation of the second output signal corresponding to the second light receiving element to which light from the light emitting element is directly incident. Therefore, the amplification unit can amplify the first and second output signals appropriately amplified by the first and second amplifiers and output the amplified signal to the signal processing unit. Therefore, erroneous detection due to the saturation of the second output signal can be avoided.

  In one embodiment, the first and second amplifiers each have a fixed amplification factor, and the amplification unit has a variable amplification factor.

  According to this embodiment, the amplification factors of the first and second output signals corresponding to the first and second light reception signals can be changed by changing the amplification factors of the amplification unit.

  In one embodiment, the smoke sensor corresponds to a first driving state in which the light emitting element is driven by a first driving current corresponding to the first light receiving element, and the light emitting element corresponds to the second light receiving element. A drive unit capable of switching between the second drive state driven by the second drive current.

  According to this embodiment, the first and second driving currents in the first and second driving states switched by the driving unit change the light emission amount of the light emitting element to the first and second light receiving elements. Corresponding values can be set appropriately and current consumption can be reduced.

  In the smoke sensor of one embodiment, the driving unit causes the light emitting element to emit light in pulses by the first and second driving currents.

  According to this embodiment, since the light emitting element emits pulses, the light emission amount of the light emitting element with respect to the first and second light receiving elements can be clearly distinguished, and the light emitting element emits light in the second driving state. Has no effect on the first light receiving element, and the current consumption can be reduced.

  Further, in the smoke sensor of one embodiment, the light emitting element is arranged so that the emitted light from the front surface of the light emission enters the smoke detecting unit and the emitted light from the side surface enters the second light receiving element. ing.

  According to this embodiment, it becomes easy to arrange the first and second light receiving elements appropriately. For example, it is possible to improve the smoke detection sensitivity by causing outgoing light having a relatively large light amount from the front side of the light emission to be incident on the smoke detecting unit and emitting light having a relatively small light amount from the side surface to the second light receiving element. As a result, current consumption can be reduced.

In one embodiment, the smoke sensor includes an integrated circuit including the first and second amplifiers,
A first wiring connecting the first light receiving element to the integrated circuit;
A second wiring connecting the second light receiving element to the integrated circuit,
The first light receiving element and the second light receiving element are connected to the integrated circuit so that the line length is the shortest under the condition that the first line and the second line have the same line length. Arranged.

  According to this embodiment, the amount of noise on the first and second wirings connecting the first and second light receiving elements and the integrated circuit can be reduced, and the amount of noise on the first wiring and the second amount can be reduced. The amount of noise on the wiring can be made equal. Therefore, it is possible to suppress the difference between the first output signal and the second output signal from fluctuating due to noise.

Further, in the smoke sensor of one embodiment, a switching unit that inputs either the first output signal or the second output signal to the amplification unit;
A first driving state in which the light emitting element is driven by a first driving current corresponding to the first light receiving element, and a first driving state in which the light emitting element is driven by a second driving current corresponding to the second light receiving element. A drive unit capable of switching between two drive states;
A microcomputer that controls the switching unit and the driving unit and includes the signal processing unit;
The microcomputer is
When the driving unit is in the first driving state, the switching unit controls the switching unit to input the first output signal to the amplifying unit, while the driving unit is set to the second driving state. When in the driving state, the switching unit controls the switching unit to input the second output signal to the amplification unit.

  According to this embodiment, since the microcomputer controls the switching unit and the driving unit and includes the signal processing unit, an increase in parts can be suppressed.

In the smoke sensor of one embodiment, the signal processing unit is
The ratio of the output value of the first amplifier when the smoke density in the smoke detector is zero with respect to the output value of the second amplifier when the smoke density in the smoke detector is zero is stored as a correction value. The smoke detection signal is output based on the difference between the second output signal multiplied by the correction value and the first output signal.

  According to this embodiment, the smoke detection signal fluctuates due to the element variation between the first light receiving element and the second light receiving element and the influence of the optical system variation between the first light receiving element and the second light receiving element. Can be suppressed.

Further, in the smoke sensor of one embodiment, a smoke detection unit into which smoke is introduced,
A light emitting element that emits light toward the smoke detector;
A first light receiving element that receives scattered light emitted from the light emitting element and scattered by the smoke in the smoke detector;
A second light receiving element that receives light emitted from the light emitting element without passing through the smoke detector;
A first amplifier for amplifying a first light receiving signal output from the first light receiving element;
A second amplifier for amplifying a second light receiving signal output from the second light receiving element;
The value of the output signal from the first amplifier when the smoke density in the smoke detector is zero is stored as a first initial value, and the second when the smoke density in the smoke detector is zero. A storage unit storing a value of an output signal from the amplifier of the second amplifier as a second initial value;
The value of the output signal from the first amplifier is V1 (k), the value of the output signal from the second amplifier is V2 (k), and the first initial value is V1 (0). When the second initial value is V2 (0), the determination value is calculated by the following equation (1):
Determination value = {V1 (k) × V2 (0) / V2 (k) −V1 (0)} (1)
A signal processing unit that outputs a smoke detection signal when the determination value calculated by the above equation (1) exceeds a predetermined detection threshold value or more.

  According to the smoke sensor of this embodiment, the initial values of the output signals from the first and second amplifiers are stored in the storage unit as the first and second initial values. For example, the initial value is stored in the storage unit at the time of factory shipment.

  In this embodiment, the output value V1 (k) of the output signal from the first amplifier measured at a certain time after installation and the second amplifier V2 (0) measured at the above time are the second initial value V2 (0). By multiplying the value V2 (0) / V2 (k) obtained by dividing the value V2 (k) of the output signal from the output signal, the fluctuation due to the ambient temperature at the time of measurement and the secular change of the light emitting element is changed to the value V1 ( The effect on k) is corrected and reduced. The signal processing unit detects the determination value obtained by subtracting the first initial value V1 (0) from the corrected output signal value V1 (k) × V2 (0) / V2 (k). When the value is exceeded, a smoke detection signal is output.

  Thereby, according to this embodiment, the accuracy of smoke detection can be improved and stable smoke detection can be performed without erroneous detection.

Further, in the smoke sensor of one embodiment, the signal processing unit is
When the determination value falls below a non-detection threshold value that is smaller than the detection threshold value, the output of the smoke detection signal is stopped.

  In this embodiment, the signal processing unit is configured such that the determination value becomes the non-detection threshold even when the smoke density of the smoke detection unit decreases and the determination value becomes smaller than the detection threshold. Until this time, the output of the smoke detection signal can be maintained. As a result, it is possible to avoid a hunting phenomenon in which the smoke detection signal is repeatedly output and stopped due to minute fluctuations in the determination value caused by disturbance such as vibration.

  Moreover, the smoke sensor of one Embodiment has memorize | stored the said non-detection threshold value in the said memory | storage part.

  Moreover, the smoke sensor of one Embodiment makes the said non-detection threshold value the value obtained by carrying out four arithmetic operations of the constant defined beforehand with respect to the said detection threshold value.

  In the smoke sensor of one embodiment, the amplification factor of the second amplifier is 1/50 or less of the amplification factor of the first amplifier.

  In this embodiment, the current-voltage conversion resistance value of the second amplifier can be set to 1/50 or less of the current-voltage conversion resistance value of the first amplifier, and the thermal noise caused by the second amplifier itself is reduced to about 7 It can be reduced to less than 1 / minute. In this case, the amount of light received by the second light receiving element from the light emitting element may be set to 50 times or more of the amount of light received by the first light receiving element from the light emitting element.

  Further, in the smoke sensor according to an embodiment, the signal processing unit calculates an average value of values obtained by continuously measuring the value of the output signal from the second amplifier after the power is turned on one time after the power is turned on. The value V2 (k) of the output signal from the second amplifier for calculating the determination value in the second determination is used.

  In this embodiment, the reliability of the value V2 (k) of the output signal from the second amplifier at the time of the first determination can be improved.

In the smoke sensor of one embodiment, the signal processing unit is
In the second and subsequent determinations after the power is turned on, the value of the second output signal is measured only once,
In the second determination after power-on, the average value of the value of the second output signal used for the first determination after power-on and the value of the second output signal measured in the second determination Is the value V2 (k) of the second output signal used for the second determination,
In the third and subsequent Nth determinations (N is 3 or more) after power-on, the value of the second output signal used for the first determination after power-on and the value measured in the Nth determination are used. The second value used for the Nth determination is an average value of the output signal value of 2 and the measured value of the second output signal value equal to or less than the predetermined upper limit number used in the latest determination. The value of the output signal is V2 (k).

  In this embodiment, the reliability of the value V2 (k) of the output signal from the second amplifier at the second and subsequent determinations can be improved. Further, since the output signal from the second amplifier is measured only once every determination period after the second time, the current consumption can be reduced, which is suitable for battery driving.

Further, in the smoke sensor of one embodiment, the signal processing unit is
When the determination value exceeds the detection threshold in the i-th determination (i is a natural number equal to or greater than 1), the value of the output signal from the first amplifier is continuously determined in the (i + 1) -th determination. An average value of the values measured a plurality of times is set as a value V1 (k) of an output signal from the first amplifier for calculating the determination value.

  In this embodiment, in the (i + 1) th determination next to the i-th determination in which smoke is detected, smoke is detected by increasing the reliability of the value V1 (k) of the output signal from the first amplifier. The determination accuracy of the (i + 1) th determination with high possibility can be improved.

In the smoke sensor of one embodiment, the signal processing unit is
The smoke detection signal is output until the determination value exceeds the detection threshold and then reaches the non-detection threshold.

  In this embodiment, the signal processing unit is configured such that the determination value becomes the non-detection threshold even when the smoke density of the smoke detection unit decreases and the determination value becomes smaller than the detection threshold. Until this time, the output of the smoke detection signal can be maintained. As a result, it is possible to avoid a hunting phenomenon in which the smoke detection signal is repeatedly output and stopped due to minute fluctuations in the determination value caused by disturbance such as vibration.

  In the smoke sensor of one embodiment, the signal processing unit outputs the output from the first amplifier in the (i + 2) -th and (i + 3) -th two determinations after the (i + 1) -th determination. An average value of values obtained by continuously measuring the signal value a plurality of times is set as the value V1 (k) of the output signal from the first amplifier for calculating the determination value. When the determination value falls below the non-detection threshold value, in the next (i + 4) th determination, one measurement value of the output signal from the first amplifier is used to calculate the determination value. The value V1 (k) of the output signal from the first amplifier is assumed.

  In this embodiment, when smoke is not detected in two consecutive determinations, the determination value is calculated by measuring the output signal from the first amplifier only once in the next determination. Can be reduced and the lifetime of the light emitting element (LED, etc.) can be improved.

  In addition, since the electronic device according to the embodiment includes the smoke sensor, it is possible to avoid erroneous detection of smoke due to disturbance such as a temperature change or element deterioration.

  According to the smoke sensor of the present invention, it is possible to prevent erroneous detection by preventing fluctuations in the output signal due to disturbance such as temperature change and element deterioration. Further, according to the present invention, jitter (fluctuation) in the output signal of the amplifier can be reduced, the influence of jitter can be reduced, and smoke can be detected with high accuracy.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a circuit diagram showing a configuration of a first embodiment of a smoke sensor of the present invention. FIG. 2 is an arrangement diagram schematically showing the arrangement of the smoke detector 18, the light emitting element 1, the first light receiving element 2, the second light receiving element 3, and the amplifier circuit 4 included in the smoke sensor of this embodiment. is there. The light emitting element 1 is a light emitting diode, and the light receiving elements 2 and 3 are photodiodes.

  As shown in FIG. 2, the smoke sensor of this embodiment includes a smoke detection unit 18 into which smoke 14 is introduced, a light emitting element 1 that emits light toward the smoke detection unit 18, and an emission from the light emitting element 1. The first light receiving element 2 that receives the scattered light scattered by the smoke 14 in the smoke detecting unit 18 and the first light receiving element 2 that receives the emitted light from the light emitting element 1 without passing through the smoke detecting unit 18. 2 light receiving elements 3. In addition, the smoke sensor of this embodiment includes an amplifier circuit 4 to which a first light receiving signal output from the first light receiving element 2 and a second light receiving signal output from the second light receiving element 3 are input. As shown in FIG. 2, the smoke sensor has a light guide path 19 that guides light emitted from the light emitting element 1 to the second light receiving element 3. A wall 12 is formed between the light guide 19 and the smoke detector 18. The wall 12 prevents the light guide 19 from being affected by the smoke introduced into the smoke detector 18.

  Moreover, the smoke sensor of this embodiment has the drive circuit 11 which drives the light emitting element 1, as shown in FIG. The amplifying circuit 4 includes only a first amplifier 5 that amplifies only the first light receiving signal output from the first light receiving element 2 and a second light receiving signal output from the second light receiving element 3. Has a second amplifier 6. The amplifier circuit 4 includes a changeover switch 7 as a changeover unit, a rear-stage amplifier unit 9 as an amplification unit, and a control circuit 8 that controls the changeover switch 7. The control circuit 8 is controlled by a control signal input from the microcomputer 16 connected to the external input terminal 21 and controls the changeover switch 7. The change-over switch 7 sends either the first output signal output from the first amplifier 5 or the second output signal output from the second amplifier 6 to the rear-stage amplifier unit 9. input.

  The post-stage amplifier unit 9 includes three amplifiers 9A, 9B, and 9C connected in series, and the output of the amplifier 9C is connected to the output terminal 10 of the amplifier circuit 4. The amplification factor of the amplifier 9B is variable by changing the resistance value of the variable resistor 17 connected to the external input terminal 22.

  The output terminal 10 is connected to the microcomputer 16. The microcomputer 16 controls the drive circuit 11 to control the output of the light emitting element 1. The microcomputer 16 includes a signal processing circuit 16A as a signal processing unit. The signal processing circuit 16A includes a first output signal output from the first amplifier 5 and amplified by the rear-stage amplifier unit 9, and output from the second amplifier 6 and output from the second-stage amplifier unit 9. The amplified second output signal is input. The signal processing circuit 16A outputs a smoke detection signal based on the difference between the amplified first output signal and the amplified second output signal.

  As shown in the timing chart of FIG. 3, the amplifying circuit 4 is intermittently driven by the driving pulse output from the microcomputer 16 to reduce current consumption. Here, the microcomputer 16 inputs a control signal to the control circuit 8, and the control circuit 8 that receives the control signal controls the changeover switch 7, and the changeover switch 7 connects the second amplifier 6 to the subsequent amplifier unit 9. Try to connect. When the amplifier circuit 4 is in an operation stable state, the microcomputer 16 controls the drive circuit 11 and outputs the drive pulse P2 shown in FIG. Thereby, the light emitting element 1 emits pulsed light corresponding to the drive pulse P2. This pulsed light is incident on the first light receiving element 2 via the smoke detector 18 and is incident on the second light receiving element 3 via the light guide 19. Here, since only the second amplifier 6 of the first amplifier 5 and the second amplifier 6 is connected to the subsequent amplifier unit 9, the second light receiving output from the second light receiving element 3 is provided. Only the second output signal output from the second amplifier 6 that has amplified the signal is input to the post-amplifier unit 9. Then, the post-stage amplifier unit 9 outputs an output voltage V2 obtained by amplifying the second output signal from the output terminal 10 to the microcomputer 16.

  Next, the microcomputer 16 outputs a control signal to the external input terminal 21 to control the control circuit 8. The control circuit 8 switches the changeover switch 7 to connect the first amplifier 5 to the subsequent amplifier unit 9. To do. The microcomputer 16 controls the drive circuit 11 and outputs a drive pulse P1 larger than the drive pulse P2 from the drive circuit 11 to the light emitting element 1. Thereby, the light emitting element 1 emits pulsed light corresponding to the drive pulse P1. This pulsed light is incident on the first light receiving element 2 via the smoke detector 18 and is incident on the second light receiving element 3 via the light guide 19. Here, since only the first amplifier 5 out of the first amplifier 5 and the second amplifier 6 is connected to the rear-stage amplifier unit 9, the first light receiving output from the first light receiving element 2 is provided. Only the first output signal output from the first amplifier 5 that amplifies the signal is input to the post-amplifier unit 9. The post-stage amplifier unit 9 outputs an output voltage V1 obtained by amplifying the first output signal from the output terminal 10 to the microcomputer 16.

  As shown in FIG. 4, the signal processing circuit 16A included in the microcomputer 16 outputs the output voltage V1 obtained by amplifying the first output signal output from the first amplifier 5 and the output from the second amplifier 6. The smoke detection signal is output based on a voltage difference ΔV from the output voltage V2 obtained by amplifying the second output signal.

  As shown in FIG. 4, when smoke flows into the smoke detector 18 and the smoke density increases, the first light receiving signal output from the first light receiving element 2 increases and the first output signal increases. Thus, the output voltage V1 increases. On the other hand, even if the smoke concentration of the smoke detector 18 increases or decreases, the second light receiving element 3 that receives light from the light emitting element 1 through the light guide 19 without passing through the smoke detector 18 is affected by the smoke. Therefore, the second output signal does not change and the output voltage V2 does not change. Therefore, when smoke flows into the smoke detector 18, the voltage difference ΔV between the output voltages V1 and V2 increases, so that with the smoke detection signal output by the signal processing circuit 16A based on this voltage difference ΔV, Smoke (smoke density) flowing into the smoke detector 18 can be detected.

  Here, the first and second light receiving elements 2 and 3 always receive light emitted from the same light emitting element 1. Therefore, when the light emission amount of the light emitting element 1 fluctuates due to temperature change or deterioration, the first light receiving signal from the first light receiving element 2 and the second light receiving signal from the second light receiving element 3 are emitted. The variation similarly occurs due to the variation of the light emission amount of the element 1. Therefore, the output voltages V1 and V2 before the temperature change or deterioration change in the same manner due to the temperature change or deterioration, and change to output voltages V1a and V2a indicated by a one-dot chain line as an example in FIG. Therefore, according to the smoke detection signal based on the difference between the output voltage V1 based on the first light reception signal and the second output voltage V2 based on the second light reception signal, an error caused by a variation in the light emission amount of the light emitting element 1 can be obtained. Detection can be prevented. In FIG. 4, the voltage difference between the first output voltage V1 and the second output voltage V2 when the smoke density is d is indicated by ΔV (d), and the first output voltage when the smoke density is 0. A voltage difference between V1 and the second output voltage V2 is indicated by ΔV (0). The voltage difference between the first output voltage V1a and the second output voltage V2a when the temperature change or deterioration occurs is indicated by ΔVa (0) when the smoke density is 0, and the smoke density is d. Sometimes indicated by ΔVa (d).

  Further, when a temperature change or element deterioration occurs in the first light receiving element 2, the temperature change or element deterioration occurs in the second light receiving element 3. Therefore, the output voltages V1 and V2 change in the same manner even if the temperature change or element deterioration occurs. Therefore, according to the smoke detection signal based on the voltage difference ΔV between the first output voltage V1 based on the first light reception signal and the second output voltage V2 based on the second light reception signal, the temperature change, element deterioration, etc. Disturbances are canceled out and erroneous detection due to the disturbances can be avoided.

  In this embodiment, the post-amplifier unit 9 is common to the first amplifier 5 and the second amplifier 6, and therefore a separate amplifier unit is provided for each of the first and second amplifiers 5 and 6. Compared with the case of having, it can suppress the dispersion | variation in the signal resulting from an amplifier. For example, fluctuations in the amplification factor of the rear-stage amplifier unit 9 due to temperature changes affect the first and second output signals in the same manner, and the first and second output voltages V1 and V2 caused by the rear-stage amplifier unit 9 are the same. The variation of can be suppressed.

  Further, in this embodiment, as illustrated in FIG. 3, the microcomputer 16 controls the drive circuit 11, so that the drive pulse P <b> 1 when the first amplifier 5 is connected to the subsequent amplifier unit 9, The drive pulse P2 when the second amplifier 6 is connected to the post-stage amplifier unit 9 is controlled to be large or small. Further, the first amplifier 5 and the second amplifier 6 can be set in a state where the amplification factors are different from each other. Therefore, as illustrated in FIG. 4, in the normal state where the smoke density is zero, the first output voltage V1 and the second output voltage V2 can be set to be equal (or close to each other). Then, the signal processing circuit 16A outputs a smoke detection signal in a normal state based on the voltage difference ΔV in this case.

  By the way, even if the amplification factor of the post-stage amplifier unit 9 is adjusted so that the first output voltage V1 from the first light receiving element 2 has a desired voltage characteristic, the first light receiving element 2 and the second light receiving element 2 The second output voltage V2 by the second light receiving element 3 due to variations in the optical system such as element variations with respect to the light receiving element 3 and molding variations in the case where the first and second light receiving elements 2 and 3 are installed. The characteristics vary. This variation in the characteristics of the second output voltage V2 causes variations in the voltage differences ΔV and ΔVa. Therefore, as a countermeasure against this variation, the microcomputer 16 uses the microcomputer 16 to set the ratio V1 (0) / V1 (0) / V2 (0) between the initial values V1 (0) and V2 (0) when the smoke concentrations of the first and second output voltages V1 and V2 are zero. V2 (0) is calculated and stored as the correction value A. The voltage difference (V1−A × V2) between the values A × V2, A × V2a obtained by multiplying the second output voltages V2, V2a in use by the correction value A and the first output voltages V1, V1a, By adopting (V1a−A × V2a) as the corrected voltage difference ΔV, it is possible to correct the element variation and the optical system variation.

  In this embodiment, as shown in FIG. 2, the light emitting element 1 is configured such that the light emitted from the light emitting front surface 1A is incident on the smoke detector 18 and the light emitted from the side surface 1B is the second light receiving light. It is arranged so as to be incident on the element 3. As a result, outgoing light having a relatively large amount of light from the light emitting front surface 1A can be made incident on the smoke detector 18, and outgoing light having a relatively small amount of light from the side surface 1B can be made incident directly on the second light receiving element 3. Therefore, smoke detection sensitivity can be improved and current consumption can be reduced. In this embodiment, as shown in FIG. 2, the amplifier circuit 4, which is an integrated circuit (IC), is connected to the first light receiving element 2 by the first wiring 31, and the second wiring 32 is used for the second wiring. The light receiving element 3 was connected to the amplifier circuit 4. The first wiring 31 and the second wiring 32 have substantially the same line length and the first and second light receiving elements 2 and 3 with respect to the amplifier circuit 4 so that the line length is the shortest. Arranged. Thereby, the amount of noise riding on the first and second wirings 31 and 32 can be reduced, and the amount of noise riding on the first wiring 31 and the amount of noise riding on the second wiring 32 can be made equal. Therefore, it is possible to suppress the difference between the first output signal and the second output signal from fluctuating due to noise.

  In the above embodiment, the post-amplifier unit 9 is provided as an amplifying unit, but the post-amplifier unit 9 may not be provided. Moreover, according to the electronic device provided with the smoke sensor of the said embodiment, the erroneous detection of smoke resulting from disturbance, such as a temperature change, and element deterioration can be avoided.

(Second embodiment)
Next, a second embodiment of the smoke sensor of the present invention will be described. The second embodiment is different from the first embodiment described above in that the microcomputer 16 shown in FIG. 1 includes a register 16B as a storage unit, and the control of the signal processing circuit 16A and the content of signal processing. Therefore, in the second embodiment, differences from the first embodiment will be mainly described.

  In the smoke sensor of the second embodiment, the first initial value V1 (0) and the second initial value V2 (0) are stored in the register 16B of the microcomputer 16. The first initial value V1 (0) is output from the first amplifier 5 and amplified by the post-stage amplifier unit 9 when the smoke density in the smoke detector 18 is zero. The value of the signal. The second initial value V2 (0) is output from the second amplifier 6 when the smoke density in the smoke detection unit 18 is zero, and is amplified by the subsequent amplifier unit 9. Is the value of the output signal. The first and second initial values V1 (0) and V2 (0) are the same as the control contents described in the first embodiment with reference to the timing chart of FIG. Similar control can be obtained by controlling the drive circuit 11 and the control circuit 8. The first and second initial values V1 (0) and V2 (0) are measured in advance as an initial state, for example, at the time of factory shipment.

Next, in the second embodiment, in actual use, the first output signal output from the first amplifier 5 and amplified by the post-amplifier unit 9 is sent to the signal processing circuit 16A of the microcomputer 16. And the second output signal output from the second amplifier 6 and amplified by the rear-stage amplifier unit 9 is input. The signal processing circuit 16A includes the first output signal value V1 (k), the second output signal value V2 (k), and the first and second initial values V1 (0), V2. From (0), the determination value is calculated by the following equation (1).
Determination value = {V1 (k) × V2 (0) / V2 (k) −V1 (0)} (1)

  Then, the signal processing circuit 16A outputs a smoke detection signal when the determination value exceeds a predetermined detection threshold value Vth1. The detection threshold value Vth1 is stored in advance in the register 16B as the storage unit.

  FIG. 5 shows the first and second initial values V1 (0) and V2 (0), the values V1 (k) and V2 (k) of the first and second output signals, and the detection threshold. The value Vth1 is illustrated. In FIG. 5, the vertical axis represents the smoke density k (%), and the horizontal axis represents the value of the output signal. The first term on the left side of the determination formula (1) is measured at the first output signal value V1 (k) measured at a certain time, the second output signal initial value V2 (0), and the above time. It is a value obtained by multiplying the ratio with the value V2 (k) of the second output signal. The first term (V1 (k) × V2 (0) / V2 (k)) indicates that the first output signal V1 (k) measured at a certain time (arbitrary time) is in an initial state (for example, 25 ° C. Means that the light emitting element (LED) 1 is not deteriorated at the ambient temperature.

  In order to make this conversion effective, the first and second light receiving elements 2 and 3 have the same structure, and the first and second amplifiers 5 and 6 are formed of the same chip, so that the temperature characteristics. Therefore, it is required that the aging characteristics are substantially consistent. On the other hand, the light emitting element (LED) 1 and the driving circuit 11 of the light emitting element 1 are single, and the first output signal V1 (k) and the second output signal V2 ( There is no difference in characteristics from k).

  Here, with reference to FIG. 6, an example of the above conversion when the output of the light emitting element 1 is lowered due to secular change will be described. In FIG. 6, V10 (k) represents a first output signal when there is no aging, and V20 (k) represents a second output signal when there is no aging. V1d (k) represents a first output signal after aging, and V2d (k) represents a second output signal after aging. For example, when the output of the light-emitting element 1 decreases by 20% due to aging and becomes 0.8 times the initial value, V2 (0) / V2 (k) in the first term of the above-described determination formula is 1/0 Since 0.8 = 1.25, the first term of the determination formula is V1 (k) × 1.25, and is corrected to the measured value in the initial state before deterioration. Note that the change in the ambient temperature can be similarly corrected to the measured value in the initial state (for example, 25 ° C.).

  Therefore, the first term of the determination formula (1) is a value obtained by correcting the value (voltage) V1 (k) of the first output signal to the initial state. Therefore, the difference between this first term and the value (voltage) V1 (0) of the first output signal in the initial state (no smoke) represents the amount of change in the first output signal V1 converted to the initial state. It will be. Therefore, when the amount of change, that is, the value of the determination formula (1) exceeds the detection threshold value Vth1, the signal processing circuit 16A outputs a smoke detection signal indicating that smoke has been detected.

  Thereby, according to this 2nd Embodiment, the accuracy of smoke detection can be improved and stable smoke detection can be performed without erroneous detection.

(First modification)
Next, a first modification of the second embodiment will be described.

  First, the stability of the smoke sensor with respect to a change in the state of smoke at the smoke detection unit of the smoke sensor will be described. The smoke sensor detects smoke when the smoke concentration around the sensor exceeds a certain level, and the smoke reflected by the smoke that has entered the smoke detector enters the first light receiving element 2 more than a certain amount. When the smoke density around the sensor is below a certain level, even if the reflected light from the smoke entering the smoke detector enters the first light receiving element 2, it must be in a non-detected state.

  On the other hand, in general, many smoke sensors generate a warning sound by a buzzer or a speaker as a smoke detection signal when smoke is detected. In particular, in a smoke sensor with a speaker, the volume of the smoke sensor is increased in order to transmit the alarm more reliably, and the frequency used for imitation sounds and voice sounds tends to increase. In such a smoke sensor, the vibration of the housing to which the buzzer and the speaker are attached also increases, and the vibration also affects the smoke state of the smoke detector. Even if the ambient smoke concentration is constant, there are two states in which the scattered light (reflected light) by the smoke of the smoke detector is different between the state before the alarm is sounded and the state where the alarm is sounding. For example, as shown in FIG. 7, the first output signal V1 (k) when the alarm is not sounding is different from the first output signal V1v (k) when the alarm is sounding. .

  For this reason, if only the detection threshold value Vth1 as a detection level for smoke detection is used, there is a possibility that erroneous detection will occur if the smoke state of the smoke detector 18 changes due to the vibration described above. For example, once smoke is detected and an alarm is sounded, the state of smoke changes due to the vibration of the alarm, the value V1 (k) of the first output signal decreases and the determination value falls below the detection threshold value Vth1. And become undetected. When it is not detected, the alarm stops sounding, the vibration disappears, the level of the first output signal V1 (k) increases (returns to the original value), and the detection is again performed when the determination value exceeds the detection threshold value Vth1. In this way, it becomes a hunting state that repeats detection and non-detection, but at this time, there is no change in the surrounding smoke state, it is in a state that should continue to sound an alarm while detecting smoke, stable as a smoke sensor It is a state that must continue to sound the alarm.

  In order to prevent erroneous detection due to vibration of the speaker or the like at the time of the alarm described above, in the modification of the second embodiment, the signal processing circuit 16A falls below the non-detection threshold Vth2 that is smaller than the detection threshold Vth1. Output of the smoke detection signal is stopped. This non-detection threshold value Vth2 is stored in the register 16B, for example. That is, in this modification, in addition to the detection threshold value Vth1, which is a determination level for determining the detection state from the non-detection state, the non-detection threshold is used as a determination level for determining the transition from the detection state to the non-detection state. A value Vth2 is provided.

  In this modification, as shown in the states (1), (2), (3), and (4) in FIG. 8, when the determination value exceeds the detection threshold value Vth1, a detection state is set and an alarm (smoke detection) is detected. Next, as shown in the state (5) of FIG. 8, even if the determination value becomes smaller than the detection threshold value Vth1, a warning is continued in the region where the non-detection threshold value Vth2 is exceeded, As shown in the state (6) in FIG. 8, when the determination value further decreases and falls below the non-detection threshold value Vth2, the alarm is stopped. As a result, it is possible to avoid a hunting phenomenon in which the smoke detection signal is repeatedly output and stopped due to minute fluctuations in the determination value caused by disturbance such as vibration.

  The non-detection threshold value Vth2 may be, for example, a value obtained by multiplying the detection threshold value Vth1 by 0.5, and 50 mV is subtracted from a value obtained by multiplying the detection threshold value Vth1 by 0.5. It may be set to a value or a value obtained by performing constant four arithmetic operations (addition / subtraction / division / division) on the detection threshold value Vth1. Such an operation can be executed by a simple program using the accumulator and register of the microcomputer 16 shown in FIG.

(Second modification)
Next, a second modification of the second embodiment will be described.

First, the judgment formula (1) used in the second embodiment is compared with the judgment formula (2) in the conventional example.
Determination value = {V1 (k) × V2 (0) / V2 (k) −V1 (0)} (1)
Determination value = V1 (k) −V1 (0) (2)

  As described above, the judgment formula (1) in the second embodiment is V2 (0) / V2 (k) with respect to V1 (k) in the first term as compared with the judgment formula (2) of the conventional example. ) Is different. In the determination formula (1), correction is mainly applied to deterioration of the light emitting element (LED) and change in ambient temperature. Therefore, in order to ensure the accuracy of determination according to the determination formula (1), the accuracy of the first output signal values V1 (k) and V1 (0) is increased and at the same time the second output signal value. The accuracy of V2 (0) and V2 (k) needs to be further increased.

  By the way, in a configuration in which a current signal obtained by converting light into current by a light receiving element is converted into a voltage signal by an amplifier that performs current-voltage conversion, the output signal is mainly due to a resistor used in an amplifier that performs current-voltage conversion in the first stage Thermal noise is superimposed on the noise component amplified by this amplifier and appears as jitter (fluctuation) in the output signal.

  Therefore, the value (voltage) V1 (k) of the first output signal and the value (voltage) V2 (k) of the second output signal actually have signal jitter (fluctuation) to some extent. is there. Further, this jitter (fluctuation) has a great influence on the smoke detection accuracy. Conversely, smoke detection accuracy can be increased by reducing the jitter (fluctuation) itself or by reducing the influence of the jitter (fluctuation).

  In addition, for the first output signal value (voltage) V1 (k), the amount of incident light is increased due to the transfer function of the optical system of the smoke detector 18, the limitation on the current consumption, the product cost, etc. There is also a limit. On the other hand, the value (voltage) V2 (k) of the second output signal corrects the influence of the ambient temperature and the aging of the LED on the value (voltage) V1 (k) of the first output signal. Is the purpose. Therefore, the noise of the second output signal itself can be reduced by increasing the amount of light incident on the second light receiving element 3 and decreasing the resistance value of current-voltage conversion and the amplification factor of the amplifier 6. .

  Specifically, as shown in FIG. 2, it is desirable to arrange the second light receiving element 3 adjacent to the light emitting element 1 made of LED. Then, the light guide 19 may be secured so that sufficiently large light can be secured from the light emitting element 1 to the second light receiving element 3.

  The post-stage amplifier unit 9 which is the post-stage amplifier shown in FIG. 1 is configured to be used in common by the first amplifier 5 and the second amplifier 6. In this configuration, the amplification factor of the post-stage amplifier unit 9 is adjusted so as to optimize the first output signal V1 (k). Therefore, the second output signal V2 (k) can be adjusted by selecting a resistance value for current-voltage conversion. That is, by setting the resistance value of the second current-voltage conversion in the second amplifier 6 to a sufficiently small resistance value with respect to the first current-voltage conversion resistance value of the first amplifier 5, It becomes possible to reduce the noise (swing) of the output signal V2 (k).

  In the second modification, the first and second amplifiers 55 and 56 shown in FIGS. 9A and 9B are employed. The first amplifier 55 is a current-voltage conversion amplifier having the first light receiving element 2 as an input and connecting a resistor R1 and a capacitor C1 between the input and output of the amplifier 55A. The second amplifier 56 is a current-voltage conversion amplifier in which the second light receiving element 3 is input and a resistor R2 and a capacitor C2 are connected between the input and output of the amplifier 56A.

In the second modification, at least the amplification factor of the second amplifier 56 is set to 1/50 or less with respect to the amplification factor of the first amplifier 55. For example, when the amount of light received by the second light receiving element 3 is set to 100 times the amount of light received by the first light receiving element 2, the resistance value R2 of the second current-voltage conversion is the resistance value R1 of the first current-voltage conversion. Can be set to 1/100. In this case, since the thermal noise is proportional to the ^half power of the resistance value (R ^1/2 ), the thermal noise of the second amplifier 56 is reduced to about 1/10 of the thermal noise of the first amplifier 55. The S / N can be improved 10 times. Further, the amount of light received by the second light receiving element 3 is set to 50 times the amount of light received by the first light receiving element 2, and the resistance value R2 of the second current-voltage conversion is the resistance value of the first current-voltage conversion. If it is set to 1/50 of R1, the thermal noise can be reduced to about 1/7, and the S / N is improved 7 times.

  Further, although the circuit scale is slightly increased, if the amplification factor of the post-stage amplifier unit 9 can be set independently of the first and second amplifiers 55 and 56, the current-voltage conversion of the first-stage second amplifier 56 is performed. Of the second amplifier 56 can be set to 1/100 of the second amplifier 56, and the thermal noise is reduced to 1/100. be able to. In this case, the S / N can be improved 100 times. From the viewpoint of improving the S / N, it is effective to set the amplification factor at the first stage as large as possible.

Furthermore, in order to improve the S / N, it is effective to limit the bandwidth of the amplifier. This is because thermal noise is proportional to the ^half power of the frequency band Δf (Δf ^1/2 ). On the other hand, when the amplifier band is narrowed, the frequency response of the amplifier becomes slow. In addition, the amplification factor decreases as the bandwidth of the amplifier is made extremely narrow. For this reason, an amplifier having a band-pass filter that secures a Q value may be employed within a range where circuit scale and response characteristics are allowed.

(Third modification)
Next, a third modification of the second embodiment will be described. In this third modification, first, in the test process before the product is shipped from the factory, the microcomputer 16 uses the second amplifier unit 9 to amplify the output signal of the second amplifier 6 after the power is turned on. The value of the second output signal for calculating the determination value in the first determination after the power is turned on, with the average value of the output signal values of the output signal continuously measured a plurality of times, for example, 10 times It is assumed that V2 (0). Further, the value V (0) of the first output signal is also the same as the value of the first output signal obtained by amplifying the output signal of the first amplifier 5 by the post-stage amplifier unit 9 after the power is turned on, for example, a plurality of times. The average value of the values measured ten times is set as the value V2 (0) of the second output signal for calculating the determination value in the first determination after the power is turned on.

  In actual measurement, the microcomputer 16 calculates the average value obtained by continuously measuring the value of the second output signal a plurality of times (for example, 10 times) after turning on the power. The value V2 (k) of the second output signal for calculating the determination value in the second determination is used. Further, the average value obtained by continuously measuring the value of the first output signal a plurality of times (for example, 10 times) after the power is turned on is calculated in the first determination for the first determination after the power is turned on. The output signal value V1 (k) is 1.

  Thus, as an example, the average value of a plurality of measurement values of 10 times is set to the values V1 (0), V2 (0), V1 (k), V2 (k) of the first and second output signals. Thus, an effect equivalent to that of limiting the band of the amplifier described above can be obtained. The value V1 (S0) of the first output signal illustrated in FIG. 10 is obtained by plotting the value based on one measurement value, and the value V1 (S1) of the first output signal is the value of the first output signal. It is a plot of average values of 10 measurements (by high speed sampling). The fluctuation of the value V1 (S1) of the first output signal is reduced to about one third compared to the value V1 (S0) of the first output signal.

  By the way, in obtaining the average value, the accuracy can be improved as the number of times of measurement is increased. However, if the number of times of measurement is increased, the test process causes an increase in cost due to an increase in test time. As the number of times of light emission 1 increases, there are disadvantages such as an increase in current consumption and an increase in secular change of the light emitting element.

  Therefore, for example, for the value (voltage) V1 (k) of the first output signal, the signal processing unit 16A determines that the determination value is the detection threshold value at the i-th determination (i is a natural number of 1 or more). When Vth1 is exceeded, in the next (i + 1) th determination, the average value of the values obtained by continuously measuring the value of the first output signal from the first amplifier 5 a plurality of times (for example, 10 times) is described above. The value V1 (k) of the first output signal for calculating the determination value is used. On the other hand, when the determination value does not exceed the detection threshold Vth1 in the i-th determination (i is a natural number equal to or greater than 1), in the next (i + 1) -th determination, the first output signal A value obtained by measuring the value only once is defined as a value V1 (k) of the first output signal for calculating the determination value.

  Thereby, in the (i + 1) th determination subsequent to the i-th determination in which smoke is detected, there is a high possibility of detecting smoke by increasing the reliability of the value V1 (k) of the first output signal ( i + 1) The determination accuracy of the first determination can be improved. On the other hand, in the (i + 1) -th determination after the i-th determination in which no smoke is detected, since the measurement is stopped once, an increase in power consumption and an increase in secular change of the light-emitting element 1 can be suppressed.

  In addition, as a frequency | count of the measurement for calculating | requiring the said average value, about 10 to 20 times is practical. For example, when the determination cycle is 10 seconds, if the continuous measurement for obtaining the average value is repeatedly measured at a cycle of, for example, 100 ms or less, the measurement can be performed in 1 second or less even if measured 10 times. There is no problem in determining the second period.

  In the third modification, the microcomputer 16 continuously determines the value of the first output signal from the first amplifier 5 a plurality of times (for example, 10 times) in the (i + 1) th determination. When the average value of the measured values is the value V1 (k) of the first output signal for calculating the determination value, the (i + 2) th and (i + 3) times after the (i + 1) th determination. In the second determination, the value of the first output signal for calculating the determination value is an average value of values obtained by continuously measuring the value of the first output signal a plurality of times (for example, 10 times). Let V1 (k). If the determination value falls below the non-detection threshold Vth2 in both the (i + 2) th and (i + 3) th determinations, the first (i + 4) th determination One measurement value of the output signal is set as the value V1 (k) of the first output signal for calculating the determination value. On the other hand, when the determination value is equal to or greater than the non-detection threshold Vth2 in at least one of the (i + 2) -th and (i + 3) -th two determinations, the next (i + 4) -th determination An average value of values obtained by continuously measuring the value of the first output signal a plurality of times (for example, 10 times) is defined as a value V1 (k) of the first output signal for calculating the determination value.

  As a result, when the possibility that the determination value is greater than or equal to the non-detection threshold value Vth2 is relatively high, the first output signal value V1 (k ) Can be used to ensure smoke detection accuracy.

  In the third modification, as described above, the second output signal value V2 (k) from the second amplifier 6 is continuously used as the second output signal value V2 (k) after the power is turned on. Since the average value measured a plurality of times (for example, 10 times) is employed, the measurement accuracy of the value V2 (k) of the second output signal can be maintained. Further, only when the power is turned on, the LED lighting time is increased a plurality of times (n times), and there is no practical problem with respect to current consumption.

  By the way, when the smoke sensor is battery-driven, it is necessary to reduce current consumption. In this case, the microcomputer 16 measures the value of the second output signal only once in the second and subsequent determinations after the power is turned on. Then, in the second determination after power-on, the value of the second output signal used for the first determination after power-on and the value of the second output signal measured in the second determination The average value is set as the value V2 (k) of the second output signal used for the second determination. Then, in the third and subsequent Nth determinations (N is 3 or more) after power-on, the value of the second output signal used for the first determination after power-on and the Nth determination are measured. The average value of the second output signal value and the measured value of the second output signal value equal to or less than the predetermined upper limit number used in the latest determination is used for the Nth determination. The output signal value V2 (k) is 2.

  That is, paying attention to the fact that the second output signal V2 (k) is a monitor measurement value for correction not related to smoke or the like, if it is necessary to reduce the current consumption by battery driving or the like, the second output signal V2 (k) The signal is measured once per determination period, and the value V2 (k) of the second output signal is stabilized without increasing the number of times of lighting of the light emitting element (LED) 1. In addition, the number of the measured values taking the average may be about 10 to 20. That is, for example, in the 30th determination, from the value of the second output signal used for the first determination after turning on the power and the measurement value in the 9th determination from the last 22nd to 30th The average value of the ten measured values is the second output signal value V2 (k) used in the 30th determination.

  The value V2 (S2) of the second output signal illustrated in FIG. 10 is an average value of 10 measurement values including the first measurement value after the power-on and the most recent 9 measurement values of the second output signal. is there. As shown in FIG. 10, the second output signal value V2 (S2) is more stable than the first output signal value V1 (S1), and varies almost with respect to V1 (S1). It can be said that they have not. This is because the amount of light incident on the second light receiving element 3 is sufficiently larger than the amount of light incident on the first light receiving element 2, and the amplification factor (the value of the current-voltage conversion resistance) of the second amplifier 6 is sufficient. This can be realized by the synergistic effect of the reduction in size and the above average value method.

  In the above embodiment, the post-amplifier unit 9 is provided as an amplifying unit, but the post-amplifier unit 9 may not be provided. Moreover, according to the electronic device provided with the smoke sensor of the said embodiment, the erroneous detection of smoke resulting from disturbance, such as a temperature change, and element deterioration can be avoided.

It is a circuit diagram which shows the structure of the signal processing system of 1st Embodiment of the smoke sensor of this invention. FIG. 3 is a layout diagram schematically showing the arrangement of light emitting elements, light receiving elements and the like included in the smoke sensor of the embodiment. It is a waveform diagram of a drive pulse and an output voltage showing the operating state of the embodiment. It is a characteristic view which shows an example of the relationship between the smoke density and output voltage by the said embodiment. It is a graph for demonstrating the determination formula in 2nd Embodiment of the smoke sensor of this invention. It is a graph for demonstrating the correction content by the determination formula in the said 2nd Embodiment. It is a graph for demonstrating the determination operation | movement of the 1st modification of the said 2nd Embodiment. It is a figure which shows the relationship between the determination value in the 1st modification of the said 2nd Embodiment, and the state transition of a detection state and a non-detection state. It is a figure which shows the 1st amplifier which the 2nd modification of the said 2nd Embodiment has. It is a figure which shows the 2nd amplifier which the 2nd modification of the said 2nd Embodiment has. It is a graph which shows an example of the value of the 1st, 2nd output signal in the 3rd modification of the said 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting element 1A Light emission front 1B Side 2 1st light receiving element 3 2nd light receiving element 4 Amplifying circuit 5, 55 1st amplifier 6, 56 2nd amplifier 7 Changeover switch 8 Control circuit 9 Subsequent amplifier part 9A, 9B , 9C Amplifier 10 Output terminal 11 Drive circuit 12 Wall 14 Smoke 16 Microcomputer 16A Signal processing circuit 17 Variable resistor 18 Smoke detector 19 Light guide path 21, 22 External input terminal 31 First wiring 32 Second wiring

Claims (21)

A smoke detector that introduces smoke;
A light emitting element that emits light toward the smoke detector;
A first light receiving element that receives scattered light emitted from the light emitting element and scattered by the smoke in the smoke detector;
A second light receiving element that receives light emitted from the light emitting element without passing through the smoke detector;
A first amplifier for amplifying a first light receiving signal output from the first light receiving element;
A second amplifier for amplifying a second light receiving signal output from the second light receiving element;
And a signal processing unit that outputs a smoke detection signal based on a difference between the first output signal output from the first amplifier and the second output signal output from the second amplifier. Smoke sensor. The smoke sensor according to claim 1,
The signal processing is performed by selectively inputting the first output signal from the first amplifier and the second output signal from the second amplifier and amplifying the first and second output signals. A smoke sensor comprising an amplifying unit that outputs to the unit. The smoke sensor according to claim 2,
A smoke sensor comprising a switching unit that inputs either the first output signal or the second output signal to the amplification unit. The smoke sensor according to claim 2 or 3,
The first and second amplifiers each have a fixed amplification factor,
The smoke sensor, wherein the amplification unit has a variable amplification factor. The smoke sensor according to any one of claims 1 to 4,
A first driving state in which the light emitting element is driven by a first driving current corresponding to the first light receiving element, and a first driving state in which the light emitting element is driven by a second driving current corresponding to the second light receiving element. A smoke sensor comprising a drive unit capable of switching between two drive states. The smoke sensor according to claim 5, wherein
The smoke sensor, wherein the driving unit causes the light emitting element to emit light in pulses by the first and second driving currents. The smoke sensor according to any one of claims 1 to 6,
The light emitting element is
A smoke sensor, wherein light emitted from a front surface of light emission is incident on the smoke detector, and light emitted from a side surface is incident on the second light receiving element. The smoke sensor according to any one of claims 1 to 7,
An integrated circuit including the first and second amplifiers;
A first wiring connecting the first light receiving element to the integrated circuit;
A second wiring connecting the second light receiving element to the integrated circuit,
The first light receiving element and the second light receiving element are connected to the integrated circuit so that the line length is the shortest under the condition that the first wiring and the second wiring have the same line length. Smoke sensor characterized by being arranged. The smoke sensor according to claim 2,
A switching unit that inputs either the first output signal or the second output signal to the amplification unit;
A first driving state in which the light emitting element is driven by a first driving current corresponding to the first light receiving element, and a first driving state in which the light emitting element is driven by a second driving current corresponding to the second light receiving element. A drive unit capable of switching between two drive states;
A microcomputer that controls the switching unit and the driving unit and includes the signal processing unit;
The microcomputer is
When the driving unit is in the first driving state, the switching unit controls the switching unit to input the first output signal to the amplifying unit, while the driving unit is set to the second driving state. A smoke sensor that controls the switching unit so that the switching unit inputs the second output signal to the amplifying unit when in a driving state. The smoke sensor according to any one of claims 1 to 9,
The signal processor is
The ratio of the output value of the first amplifier when the smoke density in the smoke detector is zero with respect to the output value of the second amplifier when the smoke density in the smoke detector is zero is stored as a correction value. And the smoke detection signal is output based on a difference between the second output signal multiplied by the correction value and the first output signal. A smoke detector that introduces smoke;
A light emitting element that emits light toward the smoke detector;
A first light receiving element that receives scattered light emitted from the light emitting element and scattered by the smoke in the smoke detector;
A second light receiving element that receives light emitted from the light emitting element without passing through the smoke detector;
A first amplifier for amplifying a first light receiving signal output from the first light receiving element;
A second amplifier for amplifying a second light receiving signal output from the second light receiving element;
The value of the output signal from the first amplifier when the smoke density in the smoke detector is zero is stored as a first initial value, and the second when the smoke density in the smoke detector is zero. A storage unit storing a value of an output signal from the amplifier of the second amplifier as a second initial value;
The value of the first output signal from the first amplifier is V1 (k), the value of the second output signal from the second amplifier is V2 (k), and the first initial value is Is V1 (0) and the second initial value is V2 (0), the determination value is calculated by the following equation (1):
Determination value = {V1 (k) × V2 (0) / V2 (k) −V1 (0)} (1)
A smoke sensor comprising: a signal processing unit that outputs a smoke detection signal when the determination value calculated by the above formula (1) exceeds a predetermined detection threshold value. The smoke sensor of claim 11,
The signal processor is
A smoke sensor, wherein the output of the smoke detection signal is stopped when the determination value falls below a non-detection threshold value smaller than the detection threshold value. The smoke sensor according to claim 12,
A smoke sensor, wherein the non-detection threshold value is stored in the storage unit. The smoke sensor according to claim 12,
The smoke sensor, wherein the non-detection threshold value is a value obtained by performing four arithmetic operations on a predetermined constant with respect to the detection threshold value. The smoke sensor according to any one of claims 11 to 14,
A smoke sensor, wherein the amplification factor of the second amplifier is 1/50 or less of the amplification factor of the first amplifier. The smoke sensor according to any one of claims 11 to 15,
The signal processor is
An average value obtained by continuously measuring the value of the output signal from the second amplifier after the power is turned on a plurality of times is obtained from the second amplifier for calculating the judgment value in the first judgment after the power is turned on. A smoke sensor characterized in that the value V2 (k) of the output signal of The smoke sensor according to any one of claims 11 to 16,
The signal processor is
In the second and subsequent determinations after the power is turned on, the value of the second output signal is measured only once,
In the second determination after power-on, the average value of the value of the second output signal used for the first determination after power-on and the value of the second output signal measured in the second determination Is the value V2 (k) of the second output signal used for the second determination,
In the third and subsequent Nth determinations (N is 3 or more) after power-on, the value of the second output signal used for the first determination after power-on and the value measured in the Nth determination are used. The second value used for the Nth determination is an average value of the output signal value of 2 and the measured value of the second output signal value equal to or less than the predetermined upper limit number used in the latest determination. A smoke sensor characterized by having an output signal value V2 (k). The smoke sensor according to any one of claims 11 to 17,
The signal processor is
When the determination value exceeds the detection threshold in the i-th determination (i is a natural number of 1 or more), the value of the output signal from the first amplifier is continuously determined in the (i + 1) -th determination. A smoke sensor characterized in that an average value of values measured a plurality of times is set to a value V1 (k) of an output signal from the first amplifier for calculating the determination value. The smoke sensor according to any one of claims 12 to 18,
The signal processor is
A smoke sensor characterized in that the smoke detection signal is output until the determination value exceeds the detection threshold and then reaches the non-detection threshold. The smoke sensor according to claim 18,
The signal processor is
In the two determinations (i + 2) and (i + 3) after the (i + 1) th determination, an average value of values obtained by continuously measuring the value of the output signal from the first amplifier a plurality of times is obtained. The value V1 (k) of the output signal from the first amplifier for calculating the determination value is used, and the determination value is the value in both the (i + 2) th and (i + 3) th determinations. When the value falls below the non-detection threshold, in the next (i + 4) th determination, one measurement value of the output signal from the first amplifier is obtained from the first amplifier for calculating the determination value. A smoke sensor characterized in that the value V1 (k) of the output signal of   The electronic device provided with the smoke sensor of any one of Claim 1 to 10.

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