JP3383356B2 - Method of manufacturing fire sensor, fire sensor and fire detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a fire sensor which selectively responds to a burning odor, and more particularly to a fire detector which can be used for detecting an initial fire in response to a burning odor. .

[0002]

2. Description of the Related Art Conventionally, as a method of detecting a fire, a method of monitoring heat and smoke in a monitoring area and discriminating a fire when a detected information value reaches a predetermined threshold value or a rising rate is generally used. . Also, when trying to detect a fire in a computer room or a room with semiconductor manufacturing equipment, a sampling pipe is stretched to collect the air in the room, and a particle counter or dust monitor is used to collect the air in the sampled air. Based on the light reflection of the particles in
I was detecting a fire. However, in the detection method based on the light reflection of air particles as described above, a false alarm due to dust often occurs.

[0003] In recent years, the burning gas and odor generated in the initial fire, especially the smoldering fire (a state in which smoke is not observed at a temperature of about 200 ° C and only a burning odor is generated) causes a fire before it becomes important. There is an interest in detection, and for example, a method of detecting a fire by changing the resistance value of a semiconductor element due to these released gases is being studied.

[0004]

For this purpose, various sensors have been proposed in the past. The general one uses an oxide semiconductor such as SnO ₂ .
However, the sensor element obtained by the EB vapor deposition method that has been conventionally used has a high resistance value (about 50 to 10).
00 KΩ), and the resistance value of the element fluctuates after being heated by a heater, and was unstable with time. Therefore, it was difficult to use it for a sensor that selectively detects only the odor during an initial fire. On the other hand, cellulose is always present in people's living spaces such as wood, cotton, paper, etc., and vinyl chloride polymer is always present in wiring, piping, packing materials, bags, covers, etc. A sensor capable of accurately detecting a specific substance emitted from cellulose or vinyl chloride-based polymer is effective for detecting an initial fire generated from a space, but such a sensor has not yet been found so far. The present invention solves the conventional problems as described above, and uses a method for manufacturing a fire sensor capable of sensitively detecting a burning odor caused by an initial fire, particularly a smoldering fire, and a fire sensor obtained by the method. It is intended to provide a fire detector.

[0005]

As a result of earnest studies, the inventors of the present invention have found that when the sensor element is formed on a substrate by the EB vapor deposition method, the respective conditions are optimally set so that the conventional method as described above is used. It was found that a fire sensor capable of solving the above problem can be manufactured, and the present invention has been completed.

That is, the present invention provides a method for manufacturing a fire sensor including a step of forming a SnO ₂ thin film on a substrate by an electron beam vapor deposition method, wherein the electron beam vapor deposition method is used at a substrate temperature of 400 to 500 ° C .; Pressure: 1 × 10 ⁻⁵ Torr or less; and vapor deposition rate: 0.1 to ⁵ Å / sec. Film thickness: 2000
~ 5000 Å thin film is formed, the obtained sensor element, 500 ~ 600 ℃ in the atmosphere, 1
The present invention provides a method for manufacturing a fire sensor, characterized by performing heat treatment for 2 hours. Further, according to the present invention, a film thickness formed by vapor deposition on a substrate: 2000 to 5000
Å SnO ₂ thin film is formed,
A fire sensor is provided, and the above manufacturing method can be used as a manufacturing method thereof.

The present invention further provides the above-mentioned fire sensor and
A detection unit including a heater for heating the fire sensor to 350 ° C. or higher , and an output of the detection unit as a fire discrimination level.
In comparison, there is provided a fire detector characterized by comprising a fire discrimination means for discriminating a fire and a signal transmission means for transmitting a fire signal according to the output of the fire discrimination means.
To do.

The present invention will be described in more detail below.
The respective conditions of the EB vapor deposition method used in the present invention are listed below. Substrate temperature: 400 to 500 ° C., preferably 450 to 5
It is 00 ° C. At substrate temperatures below 400 ° C or above 500 ° C, the resulting SnO ₂ thin film (sensor element)
Undesirably increases the initial resistance value of. Pressure during vapor deposition: 1 × 10 ⁻⁵ Torr or less. This the pressure is preferably as made becomes lower, it is suitably determined in the following 1 × 10 ^-5 Torr by a device or the like used. Deposition film thickness: 2000 to 5000Å, preferably 250
It is 0 to 3000Å. The thicker the vapor-deposited sensor element film, the lower the resistance value tends to be.However, considering uniform heating of this film and the time of the manufacturing process,
It becomes the above-mentioned film thickness range. The vapor deposition rate is, for example, 0.1.
~ 5Å / sec. Heat treatment: After the EB deposition is completed under the above conditions, heat treatment is performed in the atmosphere at 500 to 600 ° C. for 1 to 2 hours, preferably 1 hour. Due to the respective conditions of the EB vapor deposition method, it is possible to obtain an odor sensor having a low initial resistance value and being stable even after heating the heater, that is, stable over time. Note that in this specification, an electron beam evaporation method refers to a method in which a substance is evaporated on a substrate by heating a substance with an electron beam in a vacuum chamber to evaporate the substance and appropriately accelerating the evaporated substance. .

The substrate that can be used in the present invention is not particularly limited, but an alumina substrate is generally used. Examples of other substrates include a mullite substrate and a quartz substrate. A heater for heating the sensor element can be provided on the back surface of the substrate. As the heater, print ruthenium oxide or the like is usually used, but the heater is not limited to this.

The oxide semiconductor that can be used in the present invention is Sn.
O ₂ , ZnO, WO _{3 and the} like can be mentioned. Among these, S
nO ₂ is preferably used. For example, as shown in FIG. 7, in this fire sensor, a plurality of terminals 13 are provided at intervals on a circuit board 15 such as a glass board on which a main electric circuit is mounted, and the heads of the terminals 13 are provided. The lead wires 14 for the sensor electrode 12 and the heater electrode (not shown) were attached by welding (bonding), and supported the alumina substrate 8 having the sensor portion 5. The sensor portion 5 on the alumina substrate 8 is a sensor element 3 (for example, Sn
O ₂ ) and a heater (not shown) printed and fired on the opposite surface of the sensor element 11 through the substrate 8,
The heater material is heated to 350 ° C. or higher so that the sensor element 11 can detect the odor by sensing it. SnO ₂ as the oxide semiconductor is provided on the substrate by a method such as vacuum vapor deposition, for example, EB (electron beam) vapor deposition, and sputtering in argon gas.

Further, the fire detector of the present invention is provided with the above-mentioned fire.
Heat the sensor and the fire sensor to 350 ° C or higher.
Fire detection means, the output of the detection means, including the eyes of the heater
Comprising a fire discrimination means for discriminating a fire in comparison with the discrimination level, and a signal transmission means for transmitting a fire signal according to the output of the fire discrimination means. The fire discrimination means discriminates the fire based on the output, and when it is judged that the fire is detected, the detection output is transmitted to the signal transmission means, and the signal transmission means is responsive to the detection output to the reception unit such as the fire receiver through the signal line. It sends a fire signal.

FIG. 6 is a block circuit diagram of a fire detector using the odor sensor obtained according to the present invention, in which a power source / signal line for sending a fire signal is connected to a receiver such as a fire receiver (not shown). Terminals C and L, a depolarizing circuit 1 configured by using a diode bridge or the like, a switching circuit 2 using a transistor or the like, a constant voltage circuit 3 using a Zener diode or a transistor,
A comparison circuit 4 using a dividing resistor or a comparator, and S
The sensor unit 5 and the resistor 6 using the nO ₂ thin film are provided, and the voltage divided by the sensor unit 5 and the resistor 6 is input to the comparison circuit as a signal. Further, the heating control circuit 1 including a constant voltage circuit, a fluctuation detection circuit, and the like is provided so that the temperature of the heater 9 made of ruthenium oxide or the like provided on the back surface of the substrate 8 of the sensor unit 5 is constant.
0, terminals HC and HL to which the power line to the heater 9 is connected
And are provided.

Describing the operation as an example, the sensor unit 5 is supplied from the constant voltage circuit 3 when the resistance value thereof decreases in response to the burning odor generated when the material that causes a fire is heated. The voltage value divided by the sensor unit 5 and the resistor 6 is increased as a signal based on the predetermined voltage. The comparison circuit 4 has a threshold value determined by a division resistor (not shown), and compares the input voltage signal with the threshold value by a comparator. Then, when the voltage signal exceeds the threshold value as the fire determination level due to the resistance change of the sensor unit 5, the comparator is turned on to operate the switching circuit 2. The switching circuit 2 is
Composed of switching elements such as transistors,
It is turned on when the comparator of the comparison circuit 4 is turned on,
The terminals C and L are almost short-circuited. When a receiver (not shown) detects a short circuit between signal lines based on the terminal between the terminals C and L, the fire operation of the fire detector is detected and a fire alarm is issued.

In the above example, the case where the comparison circuit 4 is used as the fire discriminating means and the switching circuit 2 is used as the signal detecting means is explained. For example, an arithmetic circuit utilizing a microprocessor is used as the fire discriminating means, and
Taking in the signal of the sensor unit 5 via the / D converter, etc.,
An ON signal may be sent to the switching circuit 2 by comparing with the fire determination level stored in the storage circuit. In addition, a signal transmission / reception circuit is used instead of the switching circuit 2,
The fire signal may be sent out by transmission as a digital signal. Furthermore, the detection value of the sensor unit 5 by a digital signal may be directly transmitted to a reception unit (not shown) using an arithmetic circuit, and the fire determination may be performed by the reception unit. Also,
A self-holding circuit is provided between the switching circuit and the depolarizing circuit 1 by combining a plurality of transistors.
Hold the short-circuited state of the switching circuit 2 that once operated,
The operation may be maintained until the fire condition is restored from the receiving unit (not shown), and L is lit when the fire detector is operating.
It goes without saying that an operation display circuit using an ED or the like may be provided. Further, in the above-described embodiment, the terminals C and L of the power supply / signal line and the terminals HC and HL of the power supply line for the heater are separately provided, and four wires from the receiver (not shown) are required. It is also possible to use both wirings by sharing both terminals, and if the constant voltage circuit for generating the required voltage value for the sensor unit 5 and the heater 9 is separately configured, the circuit configuration can be simplified. It is possible.

[0015]

In general, when a cellulose or vinyl chloride polymer is decomposed, it decomposes mainly into carbon dioxide and water at a high temperature of 1000 ° C. or higher, but the decomposition temperature is 200 to 5
Decomposition products are by-produced at around 00 ° C due to dehydration reaction, oxidation reaction and the like. Many of the decomposed products have a molecular weight of 50 or more, and at this time, a characteristic smoldering odor is emitted.

As a decomposition product of cellulose, riboglucosan (molecular weight 162), riboglucosenone (molecular weight 126), 3,6-dianhydro-α-glucopyranose (molecular weight 144) produced by a dehydration reaction are analyzed by using a mass spectrometer or the like. , Pyruvaldehyde (molecular weight 7
2), diacetyl (molecular weight 86), furan (molecular weight 6)
8), acetone alcohol (molecular weight 74), 2-furfural (molecular weight 96), 5-methyl-2-furfural (molecular weight 110) were observed, and when the temperature further increased, not only carbon dioxide and water but also Furfuryl alcohol, phenol, cresol, benzofuran, butoxyphenol, dibenzofuran, indene, naphthalene, dimethylbenzene, ethylbenzene, methylnaphthalene, ethylnaphthalene, methylbenzene and the like are observed as decomposition products. Further, as a decomposition product of the vinyl chloride-based polymer, benzene (molecular weight 78), toluene (molecular weight 92), naphthalene (molecular weight 128), indene (molecular weight 11) produced by the dehydration reaction are analyzed in the same manner.
6), methylnaphthalene (molecular weight 142) and styrene (molecular weight 104) are observed, and when the temperature further rises, not only carbon dioxide and water but also ethylbenzene, xylene and the like are observed as decomposition products.

The present inventors first of all, among these decomposition products, riboglucosan, pyruvaldehyde, diacetyl,
It was found that furan and riboglucosenone are unique odor substances common to low-temperature smoldering of cellulose, and subsequently, they are particularly sensitive to the main component of these odor substances, riboglucosan, and have a low initial resistance value. As a result of earnest studies for obtaining an element, each condition of the above-mentioned EB vapor deposition was able to be found.

[0018]

EXAMPLES The present invention will be described below with reference to examples. Manufacture of a fire sensor SnO ₂ was used as an oxide semiconductor, and the substrate temperature was 400
After forming a SnO ₂ thin film on an alumina substrate by EB vapor deposition under the conditions of ℃, pressure 1 × 10 ^-5 Torr, film thickness 2500 Å, vapor deposition rate 1.5 Å / sec, heat treatment is performed at 600 ° C. for 1 hour in the atmosphere. Then, the fire sensor of the present invention was produced. As a result, the initial resistance value of the sensor element was as low as about 7 KΩ, and the initial resistance value did not change with time even after being heated by the heater.

Example 1 The fire sensor obtained as described above was placed in a constant humidity chamber, and the ceramic heater provided in this chamber was the same with various materials and temperature rise rates shown in Table 1 below. It was burnt by weight and the resistance value of the sensor element was continuously measured by the circuit shown in FIG. In addition, in order to make the initial environment the same, after filling the inside of the tank with dry air, an experiment was conducted while stirring with a fan.

[0020]

[Table 1]

The obtained results are shown in FIGS. From Fig. 1, when the cellulose powder is smoldered, the resistance value of the fire sensor begins to decrease from about 600 seconds (about 220 ° C) after the start of heating, and further sharply decreases from about 1100 seconds (about 300 ° C). It is saturated. It is considered that this fire sensor responds to the odorous substances, mainly riboglucosan, generated by the smoldering from around 220 ° C and around 300 ° C.

From FIG. 2 and FIG. 3, when the cotton and the filter paper are burnt, it takes about 600 seconds (220 seconds) after the start of heating.
It can be seen that the resistance value of the fire sensor starts to decrease from around (° C.) and thereafter decreases to an S-shape like the case of the cellulose powder. Again, 220 ° C and 30
It is considered that the fire sensor responds to the odorous substances, mainly riboglucosan, generated by smoldering from around 0 ° C.

From FIG. 4, when the beech material is smoldered, the resistance value of the element starts to decrease from about 450 seconds (about 180 ° C.) after the start of heating, and gradually starts from about 850 seconds (about 240 ° C.). It is decreasing and becoming saturated. Again, 1
It is considered that the fire sensor responds to the odorants, mainly riboglucosan, generated by smoldering from around 80 ° C and 240 ° C. Further, when CO gas was made to sniff directly to this fire sensor, there was almost no response, and from this result it is considered that only a burning odor is responding. When butane gas, isopropyl alcohol (IPA), or the like was smelled as other reducing gas, it showed a slight response to IPA, but almost no response to others.

Example 2 Comparison of Fire Sensor of the Present Invention with Conventional High Sensitivity Smoke Detector The fire sensor obtained as described above and the scattered light type high sensitivity smoke sensor conventionally used in a clean room or the like. Center and 140c of a space with a bottom of 10m x 10m and a height of 3m.
The sample (1 g of cellulose powder) is placed directly underneath it at a height of m (330 g at 10 ° C / min).
Output temperature in the case of the fire sensor of the present invention, and the extinction rate (% / m) in the case of the high-sensitivity smoke sensor were measured with time. The output voltage was measured using the circuit shown in FIG. The obtained results are shown in FIG. In FIG. 8, curve 1 is the fire sensor of the present invention, and curve 2 is the conventional high-sensitivity smoke detector. As a result, the high-sensitivity smoke detector is about 1
While the output rises in 600 seconds, the fire sensor of the present invention rises earlier in about 800 seconds. Therefore, it can be seen that the fire sensor of the present invention is more sensitive to cellulose smoldering than the conventional high-sensitivity smoke detector, and can be used for early detection of fire.

[0025]

EFFECTS OF THE INVENTION It is possible to provide a method of manufacturing a fire sensor capable of sensitively detecting a burning odor caused by an initial fire, particularly a smoldering fire, and a fire detector using the fire sensor obtained by the method. .

[Brief description of drawings]

FIG. 1 is a diagram showing a change in resistance value of a sensor element when cellulose powder is burnt.

FIG. 2 is a diagram showing a change in resistance value of a sensor element when cotton is smoked.

FIG. 3 is a diagram showing a change in resistance value of a sensor element when a filter paper is burnt.

FIG. 4 is a diagram showing a change in resistance value of a sensor element when a beech material is burnt.

FIG. 5 is a diagram showing a circuit for measuring a resistance value of a sensor element.

FIG. 6 is a block circuit diagram of an embodiment of the fire detector of the present invention.

FIG. 7 is a perspective view of a sensor element.

FIG. 8 is a diagram showing a comparison of sensitivities of the fire sensor of the present invention and a conventional high-sensitivity smoke detector to odorants generated during smoldering.

[Explanation of symbols]

1 Depolarization circuit 2 switching circuits 3 constant voltage circuit 4 Comparison circuit 5 Sensor section 6 resistance 8 substrates 9 heater 10 Heating control circuit 11 Sensor element 12 sensor electrodes 13 terminals 14 lead wire

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-250748 (JP, A) JP-A-2-88957 (JP, A) JP-A-3-233350 (JP, A) JP-A-2- 128149 (JP, A) JP-A-5-10904 (JP, A) JP-A-1-206249 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 27/12

Claims (3)

(57) [Claims] 1. Sn on a substrate by electron beam evaporation method
The method of manufacturing a fire sensor including a step of forming a thin film of O _2, the electron beam vapor deposition method, a substrate temperature: 400 to 500 ° C., the pressure during vapor deposition: 1 × ¹⁰ -5 Torr or less; and deposition rate: 0 Film thickness: 2000 under conditions of .1 to 5Å / sec
~ 5000 Å thin film is formed, the obtained sensor element, 500 ~ 600 ℃ in the atmosphere, 1
A method for manufacturing a fire sensor, characterized by performing heat treatment for 2 hours. 2. A product manufactured by the manufacturing method according to claim 1.
Fire sensor. 3. The fire sensor according to claim 2, and the fire.
A detection unit including a heater for heating the disaster sensor to 350 ° C. or higher, a fire determination unit that compares the output of the detection unit with a fire determination level to determine a fire, and a fire signal according to the output of the fire determination unit. A fire detector, comprising: a signal transmitting means for transmitting the.