JPH071250B2 - Combustion product detector - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to combustion product detection devices, and more particularly to means for testing the sensitivity of such detection devices.

(Prior Art) For example, there are two types of devices for detecting combustion products such as smoke, that is, an ionization type detection device and a photoelectric detection device. Although the present invention is described in the context of an ionization type detector, the principles of the present invention can be applied to any type of combustion product detector.

In the ionization type detection device, the sensor is generally an active ion chamber which is relatively open to the atmosphere. Generally, the reference impedance is given by a reference ionization chamber that is relatively isolated from the atmosphere, a reference chamber that is open to the atmosphere but is insensitive to combustion products, or a physical resistor. . Each chamber contains a pair of spaced electrodes. Or
The chamber has a common electrode in between. And, for example, a means for ionizing air molecules between the electrodes such as a radiant energy source is provided. Regarding the plurality of chambers or the chamber and the resistor arranged in series, and the voltage applied across the chambers, an electric field is generated between the electrodes to move ions between the chambers, or the plurality of chambers. A current is generated through the resistor. Therefore, the potential at the sensing electrode at the connection between the active chamber and the reference impedance follows the relative impedance of the two members.

Changes in atmospheric conditions, such as the presence of combustion products, affect the ionic current through the members in series and thus their impedance. The voltage at the sensing electrode is monitored by a detection circuit which, when a predetermined alarm level is exceeded, activates the appropriate alarm circuit. In this type of built-in or battery operated combustion product detection device, a battery monitor circuit is provided which is adapted to generate a low battery signal when the battery discharges to a level near which the desired operation of the alarm circuit is not achieved. It has been known.

It is known to provide means for testing the operation of combustion product detection devices. In particular, means are provided for testing the sensitivity of combustion product sensors by simulating the presence of combustion products. In ionization type detectors, this test means comprises an inter-operation switch that connects the impedance across the ionization chamber, thereby changing the voltage across it, so that if the combustion products are required to trigger an alarm. If there is more than this amount, the sensing electrode signal voltage will be equal to the value generated by the signal. Such a device is, for example,
It is disclosed in U.S. Pat. Nos. 4,097,850 and 4,246,572.
These test devices simply check to see if the sensitivity of the sensor exceeds a predetermined minimum sensitivity. However, it is important that its sensitivity is not too high so that false alarms are not frequently reported.

All such interworking test equipment relies on the user remembering to test the combustion product detection equipment at regular intervals. However, users often forget to do such tests. Furthermore, since the combustion product detection device is generally installed on the ceiling or in a place that is relatively inaccessible, it is extremely inconvenient to manually test the device, and the user cannot test such devices. Prevent you from doing.

Circuits for self-checking the sensitivity of combustion product detection devices are also known. Such a device is described in U.S. Pat.
No. 0 and U.S. Pat. No. 4,302,753, which show continuous monitoring of the clean air voltage from a sensor. However, these devices
Voltage comparators must be added for clean air voltage monitoring, they only check if the sensitivity is above a minimum sensitivity level. Moreover, the device of U.S. Pat. No. 4,302,753 is not necessarily suitable for checking minimum sensitivity levels. That is,
The sensing electrode voltage of this device changes with the smoke level,
Also, chamber saturation causes non-linearity, which results in large errors in the smoke levels tested.

Various types of fault detection devices are known which are adapted to automatically and periodically self-test the device to detect the presence of a fault. For example, such devices are disclosed in US Pat. No. 3,928,849 and US Pat. No. 4,199,755. However, these periodic self-test circuits are not designed to test the sensitivity of combustion product detectors. Previous typical combustion product detection devices, which test sensitivity by simulating combustion products, operate on the principle that a normal smoke alarm must operate under that test condition. ing. If the alarm is not activated due to improper sensitivity of the detection device, life safety is jeopardized. Therefore, there is a need for a combustion product detection device that automatically and positively displays when the sensitivity does not match the test value for performing proper operation.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a combustion product detection device with improved sensitivity detection means, which eliminates the disadvantages of previous combustion product detection devices and has the advantages of structure and operation.

An important object of the present invention is to provide a combustion product detection device with a test means for determining whether the sensitivity of the sensor has fallen below a predetermined maximum sensitivity.

Another object of the present invention is to provide a combustion product detection device that automatically and periodically tests the sensitivity of the sensor.

It is a further object of the present invention to provide a combustion product detection device that includes means for testing whether the sensitivity of the sensor is within a predetermined range between a minimum and maximum value.

Another object of the present invention is to provide a combustion product detection device provided with a sensitivity test means for simulating combustion products and positively indicating when the sensitivity does not match the test value.

These and other objects of the present invention include a sensor that produces an output signal in response to the presence of an amount of combustion products in excess of a threshold threshold level, the threshold level being inversely proportional to the sensitivity of the sensor. And desired sensitivity is achieved by providing a combustion product detection device adapted to fall within a predetermined range between a minimum and maximum value. The combustion product detection device of the present invention comprises a test means for simulating the presence of an amount of combustion products slightly lower than the amount corresponding to the maximum sensitivity, and an amount slightly higher than the amount corresponding to the minimum sensitivity. Test means for simulating the presence of combustion products of the product, control means for energizing the test means, and alarm means connected to the sensor for giving an alarm instruction in response to an output signal from the sensor. When the sensitivity of the sensor exceeds the maximum sensitivity, or when the sensitivity of the sensor becomes smaller than the minimum sensitivity, the alarm instruction is generated in response to the energization of the test means. Characterize.

Although the present invention comprises novel features, the combination of these features will be more fully described in the accompanying drawings. In particular, although the constituent members are clearly shown in the claims, it is needless to say that the details can be modified without impairing the effects of the present invention.

In disclosing the present invention, an embodiment thereof will be described with reference to the drawings. If this is examined closely, the structure, operation, and effect of the present invention will be extremely clear.

Embodiment FIG. 2 will be described first. There is shown an explosive product detector generally designated at 10 embodying features of the present invention and constructed in accordance with the present invention. The detector 10 comprises a circuit connected to an ionization type sensor 12. This sensor
12 includes a reference ionization chamber 13 in which a battery power source B
It has an electrode 14 and an electrode 15 connected to +, and these electrodes are kept at a certain distance by a spacer (not shown). Then, the electrodes 14 and 15 and the spacer form a relatively non-porous enclosure. The sensor 12 also includes an active ionization chamber 16, which has an electrode 17, which cooperates with the electrode 15 to form a relatively porous, electrically conductive enclosure defining the active ionization chamber. However, the electrode 15 is the common electrode of both chambers 13 and 16.

It is equipped with something like a radioactive source (not shown) for ionizing air molecules in both chambers, whereby an electric field is generated in each chamber by a voltage applied between electrodes 14 and 17, Similarly, the movement of ions between the electrodes produces a current. The reference and activation chambers 13, 16 form a voltage divider, which is connected in series with a resistor 18 between the B + power supply and ground. The voltage at electrode 15 is therefore a function of the relative impedance of chambers 13 and 16. The impedance of resistor 18 is significantly lower than the impedance of the ionization chamber and therefore does not normally affect the sensing electrode voltage. A series connection of a resistor 19 and a normally open manual test switch 20 is connected in parallel to the sensor 12, and it is known whether or not the sensitivity of the sensor 12 is equal to or higher than a predetermined minimum sensitivity, which is well known in the art. It is described in detail in Japanese Patent No. 4097850.

Explosion product detector 10 further includes a potentiometer connected between the B + power supply and a wiper connected to the reference terminal of smoke comparator 22, the other terminal of smoke comparator 22 being the sensing electrode 15
Connected to. The output of comparator 22 is connected to one of the three inputs of OR gate 23, the output of OR gate 23 is connected to the input of horn driver horn driver 24, and the output of this horn driver is appropriate. Connected to an output terminal connected to another horn (not shown).
The horn driver 24 may be a single driver or a number of drivers operating one associated electromechanical horn or piezo electric horn. Mochi theory Other types of alarms can also be used.

Combustion product detector 10 also has a low power comparator 26,
The low power supply comparator 26 has a reference input terminal to which an internal reference voltage is supplied. This internal reference voltage is supplied by a current source 27 connected to the B + power supply and regulated by a Zener diode 28. The anode of the Zener diode 28 is connected to the negative terminal of the battery 29, and the positive terminal of the battery 29 is the B + power supply and is connected to the other input of the low power supply comparator 26. The output of the low power supply comparator 26 is connected to one of the two inputs of the AND gate 31. The output of AND gate 31 is connected to one of the inputs of OR gate 23. The other input of the AND gate 31 is connected to the output line of the clock 32. The output of the clock 23 is also connected to the reset terminals of the two D flip-flops 33 and 34. The set terminals of these two flip-flops 33 and 34 are grounded. The data inputs of the flip-flops 33 and 34 are connected to the output of the smoke comparator 22, and the clock inputs of the flip-flops 33 and 34 are connected to the output lines 3 and 4 of the clock 32, respectively.

The clock 32 also has an output line 2, which is connected to the inhibit terminal of the horn driver 24 and also to the gate of a metal oxide semiconductor field effect transistor (MOSFET) switch 36 via an amplifier 35. There is. The drain of this field effect transistor switch 36 is connected to the electrode 17 of the sensor 12. Two resistors 37 and 38 are connected between the MOSFET 36 and the B + power supply. This resistor 37 is connected to the MOSFET 39
It is connected across the power supply and the drain.
The gate of MOSFET 39 is connected to the output of inverter amplifier 40. The input of the inverter amplifier 40 is connected to the output line 4 of the clock 32. It should be understood that other types of electronic switching devices may be used in place of the MOSFETs 36, 39 and associated amplifiers 35, 40. clock
32 also has an output line 5, which is connected to one input of the AND gate 41. Besides the AND gate 41, the input is connected to the output of the OR gate 42. The OR gate 42 has two input terminals, which are respectively the Q output of the flip-flop 33 and the flip-flop.
It is connected to the inverted Q output of 34. The output terminal of the AND gate 41 is connected to the input terminal of the OR gate 23.

The combustion product detector will be described below with reference to the waveform diagram of FIG.
The operation of 10 will be described. In normal operation, the impedance of the active ionization chamber 16 increases in the presence of combustion products. When the voltage of the electrode 15 reaches the preset level of the reference voltage set by the potentiometer 21, an output is output from the smoke comparator 21, which is transmitted to the horn driver 24 via the OR gate 23.
A horn (not shown) associated with this horn driver 24
Will remain active as long as the amount of combustion products is sufficient to maintain the voltage on electrode 15 above the reference voltage value.

If you want to manually test the operation of the combustion product detector 10, close the external test switch 20, which causes the resistor 19,
A voltage divider consisting of 18 is connected in parallel with the sensor 12.
This serves to raise the voltage on electrode 15 as if there were a sufficient amount of combustion products to activate the alarm. Therefore, the test switch 20 simulates the presence of combustion products, causing the voltage on the electrode 15 to rise above the external reference voltage value and produce an output from the smoke comparator 22.

A low battery comparator that also monitors the supply voltage B + and generates a fault signal when the battery voltage drops below a level required for the combustion product detector 10 to function properly.
26 are provided. Therefore, when the supply voltage B + drops below the internal reference level determined by the reference source 27, a continuous output is produced from the low battery comparator 26. This output signal is applied to one terminal of the AND gate 31 and the other input is added from the output line 1 of the clock 32. This clock signal has its various waveforms designated by line numbers corresponding to the output lines of the clock 32, as shown in FIG. Line 1 waveform is typically a short pulse lasting approximately 10 ms
43, which is typically repeated at relatively irregular time intervals of about 1 minute. When the output signal from the low battery comparator 26 is present, each clock pulse 43 on line 1 produces an output from the AND gate 31 and an OR
The horn driver 24 is excited via the gate 23. Therefore, for low battery low battery voltage, combustion product detector
10 produces a short 10ms beep about once per minute. This intermittent signal can be easily distinguished from the continuous alarm signal generated when combustion products are present and can clearly indicate a low battery condition.

All of the above are well known operating characteristics of combustion product detectors. The novel features of the self-test circuit 30 of the present invention will be described below with reference to the waveforms of lines 2-5 of FIG. The clock signal on line 1 indicating a low battery is supplied to the reset terminals of the flip-flops 33 and 34,
Added to reset them. Thus 1
About once per minute, each of these flip-flops 33, 34 is reset and occurs when this reset signal is shown at t ₁ in FIG.

The important features of the present invention are as follows. That is,
A failure indication is generated in response to the self-test when combustion product detector 10 is not operating properly, that is, when it fails the self-test. Thus, at time t ₁ , about 15 ms after the end of each pulse 43 on line 1, clock 32 produces an output pulse 44 on line 2, which is applied to the inhibit terminal of horn driver 24. This suppresses the operation of the horn driver 24 during the inhibit pulse 44 (about 2 seconds) so that no alarm indication can be generated while the self-test is in progress. This ban is lifted at the end of pulse 44, and after the self-test is complete,
An alarm signal is generated. The pulse 44 on line 2 is also input to the gate of MOSFET 36 via amplifier 35, opening it and connecting it to the voltage divider consisting of resistors 37, 38 and 18 in parallel with sensor 12. As a result, electrode 15
Changes in voltage occur generally in the same manner as described for the operation of the manual external test switch manual external test switch 20.

There are different combustion regimes, and therefore different types of combustion products, which will excite the sensor 12.
Because of this, it is not possible to set the sensitivity of this sensor 12 to a level that will respond equally to all types of combustion products. As a result, for example, even if the concentration of a combination of specific products among a plurality of combustion products generated from a certain combustion form is a value sufficient to make the sensor voltage higher than an external reference level, For the combined concentration of different products of that form of combustion, in order for the sensor voltage to rise above the reference level, it would have to be a slightly higher concentration value than above. Therefore, in general, the level of sensitivity of the sensor 12 is
It is set to a value sufficient to be able to respond to all forms of combustion. In the preferred embodiment of the present invention, the minimum value of the sensitivity thus set is as follows. That is, the value at which the sensor responds by issuing a smoke alarm command when the amount of combustion products reaches an obscuration of 1.5% per foot. (The higher the sensitivity of this sensor, the lesser the amount of combustion products needed to excite the sensor to generate an alarm.) However, if the sensor is too sensitive, combustion The product detector 10 often gives false, useless alarms (e.g., if you smoke or cook near this detector of combustion products,
Useless alarm is issued. ). Therefore, in the preferred embodiment, the maximum value of the sensitivity of the sensor 12 is preferably the following value. That is, the amount of combustion products is 1
At opacity less than 0.5% per foot, a value that does not cause the sensor to excite and trigger an alarm is preferred. In summary, the preferable range of sensitivity of the sensor 12 is, in terms of the amount of combustion products, per foot,
A range of opacity of 0.5 and 1.5% is preferred.

The values of resistors 37 and 38 are
The voltage value at electrode 15 is selected to change to a value slightly below the minimum voltage value required to produce the output from smoke comparator 22. That is, by sandwiching the sensor 12 and connecting the resistors 37 and 38, the amount of smoke corresponding to a value slightly lower than 0.5% per foot, which is the maximum sensitivity of the sensor 12, is simulated. As a result, when the sensitivity of the sensor 12 is within the preferable range, the smoke comparator 22 does not generate an output in response to the combustion product simulation. However, if the sensitivity of the sensor 12 is too high, that is, if the detection voltage of the electrode 15 obtained for clean air is higher than the normal value, the voltage of the electrode 15 is closed when the transistor switch 36 is closed. Rises above the external reference value, resulting in the output signal from the smoke comparator 22. Further, this signal is supplied to the horn driver 24 via the OR gate 23. However, the horn driver 24 is not driven because it is controlled by the pulse 44 on the clock line 2.

However, the output from the smoke comparator 22 also
The flip-flop 33 which was just reset at time t _o and
Supplied to each of the 34 data terminals. The flip-flop 33 has its set and reset terminals grounded or at a logic low level. In this state, the Q terminal is low, the data terminal is a logic H and the clock terminal is a positive-going transitio.
can only go high if n). Time t
_{At 1} , clock 32 also produces a negative-going pulse 45 on line 3 for a period of about 1 second. When the data input of flip-flop 33 is high, the Q output of flip-flop 33 will be due to the positive transition transition 46 at the end of clock pulse 45 at time t ₂ as a result of the output signal from smoke comparator 22. Line 1 after going high for about 1 minute
Remains high until reset at the next clock pulse 43 of. This output signal is supplied to one input of the AND gate 41 via the OR gate 42. However,
The other input to AND gate 41, which is connected to clock line 5, is low at time t ₂ (see FIG. 1), so that there is no output from AND gate 41 at this time. On the other hand, if the maximum sensitivity of the sensor is normal, the output from smoke comparator 22 will not be available during pulse 45 and the Q output of flip-flop 33 will remain low at transition 46, and No signal is supplied to the gate 41.

At the same time as the positive transition transition 46 of pulse 45 at time t ₂ ,
32 creates a negative going pulse 47 on line 4, which
It has a period of about 1 second, which is fed to the clock input terminals of the inverter amplifier 40 and the flip-flop 34. Inverter amplifier 40 produces a high output, which is applied to the base of transistor switch 39, causing transistor switch 39 to switch on due to the short circuit of resistor 38. Therefore, resistor 37 is the only sensor
Voltage divider (voltag with resistor 18 connected to 12
e divider). The value of resistor 37 is selected to cause a voltage change at electrode 15 that is slightly greater than the voltage change caused by the amount of smoke corresponding to an opacity of 1.5% per foot. In other words, a resistor 18 between the sensors 12
By connecting only resistor 37 with, a quantity of smoke is simulated which is slightly higher than the quantity of smoke corresponding to the minimum permissible sensitivity of sensor 12. Therefore, if the sensitivity of the sensor 12 is within the desired range, the voltage at the electrode 15 is raised above the external reference and the smoke comparator 22 produces an output signal. It does not activate the horn driver 24. Because it is still stopped by pulse 44. The output of smoke comparator 22 is also provided to the data terminal of flip-flop 34. Positive transition of pulse 47
48 causes the inverted Q output terminal of flip-flop 34 to change state to a logic low level at time t ₃ (when the set and reset terminals are at ground level, the inverted Q output is normally a logic low level). It is at a high level, and the inversion of the Q output has been described above), and does not affect the output of the OR gate 42. The inverted Q output remains at a logic low level until reset at the next clock pulse 43 after about 1 minute.

On the other hand, if the sensitivity of the sensor 12 is too low, then no output from the smoke comparator 22 will occur and, as a result, the data terminal of the flip-flop 34 will remain low.
In this case, when the positive transition transition 48 of pulse 47 is applied to the clock terminal of flip-flop 34 at time t ₃ , the inverted Q output remains high and the output of OR gate 42 goes high. It is supplied to the gate 41. However, as explained above, the other input to AND gate 41 is low, so no output comes from it.

Both pulses 44 and 47 end at time t ₃ . Therefore, at this time, both transistor switches 36 and 39 open, leaving resistors 37 and 38 unconnected, and at the same time the inhibit is removed from horn driver 24. Approximately 15 ms later, ie, at time t ₄ , on line 5 of clock 32 with a time interval of 10 ms between 2
Two short (preferably about 10 ms) pulses 49 are formed and this pulse 49 is applied to the AND gate 41. Therefore, at this time, the other input of the AND gate 41 becomes OR.
AND, if high as the output from gate 42,
Gate 41 forms two short "high" outputs, which are fed through OR gate 23 to horn driver 24.
And provides a special fault indication, therefore, at the time of this clock pulse, when the output from the Q terminal of flip-flop 33 is high (which indicates that sensor 12 is too sensitive). means),
Alternatively, when the output from the inverting Q terminal of flip-flop 34 is high (which means that the sensor is too insensitive), two consecutive 10ms “bee” beeps indicate this condition. Emitted to show. The successive pulses on lines 1-5 shown in FIG.
It will be recognized that it repeats every minute.
Therefore, the sensor should be tested for the highest or lowest sensitivity.
If 12 is found to be defective, then about every minute, two consecutive short “bee” beeps indicate this fault condition. If these two tests are successfully passed, when both the Q terminal of the flip-flop 33 and the inverted Q terminal of the flip-flop 34 are at the logic low level, there is no output indication and the pulse at the other input of the AND gate. During 49, one input of AND gate 41 is at a logic low level.

The specific timings shown in FIG. 1 are for illustration only and are not limiting. It should be appreciated that other timing sequences can be utilized to achieve substantially the same results as above. If desired, the circuit enclosed by dashed line 50 can be an integrated circuit. In that case, if desired, the test registers 37 and 38 can be selectively connected externally to an integrated circuit for better precision control.
It should also be appreciated that the self-test circuit 30 can be used to test the sensitivity of other types of combustion product detectors. In photoelectric detectors, for example, the sensitivity of the output of the light emitter or the input of the light sensor, or the internal reflective surface is likewise electronically controlled to simulate smoke,
And achieve similar results. While described in the preferred embodiment above as using a battery power source, the present invention can be used with combustion product detectors using other power sources such as AC, remote power supplies, and the like. It can be used in any type of combustion product detector, such as residential or commercial, as disclosed in the publication. In this detector, the alarm and defect outputs are electronic signals that are sent to a monitor system other than audio analog or the like.

The foregoing provides an improved apparatus for automatically self-testing the sensitivity of combustion product detectors at both ends of the desired sensitivity range, the test method of which accurately simulates smoke and sensitivity testing. It will be appreciated that a special defect output is formed only if a defect occurs in the.

[Brief description of drawings]

FIG. 1 is a diagram showing various clock signals generated by the test circuit of the present invention, and FIG. 2 is a circuit diagram showing a combustion product detector of the present invention. 10 …… Combustion product detector, 12 …… Sensor, 14, 15, 17 …… Electrode, 22 …… Smoke comparator, 26 …… Low battery comparator, 2
7 …… Current source, 33,34 …… Flip-flop, 35 …… Amplifier, 36,39 …… MOSFET, 40 …… Inverting amplifier.

Claims (7)

[Claims] 1. A sensor having an output signal in response to the presence of an amount of combustion products in excess of a threshold amount, the threshold amount varying inversely with the sensitivity of the sensor, and the desired sensitivity being the maximum sensitivity. And a combustion product detector within a predetermined range between the minimum sensitivity and a test means having a first operating state and a second operating state, the first operating state and the second operating state A control means for operating a certain test means, and an alarm means connected to the sensor and the control means for generating a signal indicating a failure, wherein the test means is maximum in the first operating state. A second amount of combustion products that simulates the presence of a first amount of combustion products that is slightly less than the amount that corresponds to sensitivity and that is slightly greater than the amount that corresponds to minimum sensitivity in the second operating condition. Simulating the presence of, the control means includes means for generating a signal indicating failure to the alarm means in response to an output signal from the sensor when the test means is in the first operating state,
And a means for generating a signal instructing the alarm means to fail in response to the absence of an output signal from the sensor when the test means is in the second operating state, whereby the sensitivity of the sensor is predetermined. A combustion product detector responsive to the operation of the test test means to generate a signal indicative of a failure when the temperature is out of the range. 2. The combustion product detector according to claim 1, wherein the sensor is an ionization type sensor. 3. A combustion product detector according to claim 1 wherein said test means includes electronic switching means. 4. The control means comprises a first operating state and a second operating state.
2. The combustion product detector according to claim 1, further comprising means for automatically and periodically operating the test means in the operating state of. 5. The combustion product detector of claim 4 further comprising manual means for testing the sensitivity of the sensor. 6. The control means comprises a first operating state and a second operating state.
Means for operating the test means for a predetermined time interval during which the test means continuously operates in the above operating state, and delaying the generation of a signal indicating a failure by the alarm means until after the end of the predetermined time interval. A combustion product detector according to claim 1 including means. 7. The test means comprises first electronic switch means and second electronic switch means, and the control means continuously operates the test means in a first operating state and a second operating state. Timing means for periodically operating the test means for a predetermined time interval, the first means being responsive to the presence of an output signal from the sensor when the test means is operating in a first operating state. A first register means for generating a failure signal and a second failure signal in response to the absence of an output signal from the sensor when the test means operates in a second operating state. Second register means, means for inhibiting operation of the alarm means for the predetermined time interval, and the alarm means in response to either the first failure signal or the second failure signal. In the above Combustion products detector Claims paragraph 1, further comprising a means for generating a signal indicating the end after a failure time interval.