JPH11160164A - Differential heat sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensor capable of reducing the scale of a logical circuit, suppressing the manufacturing cost low, and preventing the fire sensing reliability from being deteriorated even if noise is mingled in temperature measurement. SOLUTION: Measured continuous (n) temperature values are synthesized in sequence via a prescribed calculating equation to generate one comparison object data, the difference quantity between this comparison object data and the past data on the comparison object data generated in the past is calculated, and a differential heat sensor senses a fire by comparing it with a threshold. The past data is substituted with the value of (a×P+b×t) as the comparison object data is generated, where (P×n) is the value of the past data stored in advance, (t) is the value of the generated comparison object data, (n) is proportional constant, and (a) and (b) are weighting constants having the same symbol and satisfying the condition a+b=n and |a|>|b|.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential heat sensor which has a temperature measuring means for measuring temperature intermittently and detects a fire from a change in the measured temperature value.

[0002]

2. Description of the Related Art A differential heat sensor which has a temperature measuring means for intermittently measuring a temperature value and detects a fire from a change in the measured temperature value is a known technique. Differential heat sensors use analog circuits such as comparators and delay circuits, for example, to determine whether a fire has occurred by comparing the current voltage value with the past voltage value indicating temperature, In some cases, the temperature is converted into digital data by a digital circuit such as a circuit or a microcomputer control and processed, and the present temperature is compared with the past temperature to determine a fire. Among the differential heat sensors using an analog circuit and the differential heat sensors using a digital circuit, the latter is considered to have higher performance because of the high reliability of fire judgment.

As a conventional differential heat sensor using a digital circuit, for example, there is a differential sensor disclosed in Japanese Patent Application Laid-Open No. 6-84075. Such a differential sensor includes measuring means for measuring the temperature at predetermined intervals, past data storing means for storing past temperature values, and calculating the difference between the past temperature value and the present temperature value. It is determined whether a fire has occurred by comparing these difference amounts with a predetermined threshold value.

FIG. 4 is a block diagram for explaining the outline of the processing of the differential heat sensor by the conventional digital circuit (particularly, processing in the process of storing past data). In the differential heat sensor, as past data storage means for storing past temperature values, for example, for a predetermined time (for example, 1
0) are stored in the storage area 30.
The ten temperature values Vn, V1 to V8, and Vp measured in the past are sequentially stored in the ten storage areas 30..., And the current temperature value data Vn and a predetermined time (nine before) are selected from among them. And the temperature value data Vp of
The difference amount is calculated.

When new temperature value data is measured, the oldest temperature value data Vp stored before is discarded, and the remaining nine temperature value data Vn, V1 to V8 are placed one by one. , And new temperature value data is input to the empty storage area 30. Then, the above processing is repeated to perform fire monitoring.

[0006]

In the above-described differential heat sensor using a conventional digital circuit, a large number of storage areas (for example, 10 storage areas) are used to store temperature data for a predetermined time in the past as described above. 30 ...)
There is a problem that the scale of the logic circuit becomes larger and the manufacturing cost becomes higher. Since a large number of sensors are used, for example, in a fire alarm system, an increase in the manufacturing cost of one unit greatly increases the manufacturing cost of the entire system.

Further, in the above-mentioned differential type heat sensor, for example, when noise is mixed in the temperature measurement and the temperature value data rises, this noise directly affects the calculation of the difference amount. There was a problem. That is, erroneous fire detection due to noise is relatively likely to occur, and noise countermeasures have been required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the size of the logic circuit is small, so that the manufacturing cost can be kept low. It is characterized by providing a differential heat sensor that does not reduce reliability.

[0009]

According to a first aspect of the present invention, there is provided a temperature measuring means for measuring a temperature value intermittently and a predetermined number of consecutive s temperature values measured in sequence. And a past data storage unit that stores past data relating to previously generated comparison target data by generating a single comparison target data every s times of measurement. And the difference amount (t × n−P × n), where t is the value of the generated comparison target data, (P × n) is the past data stored in the past data storage unit, and n is a predetermined proportionality constant. And a fire signal output means for outputting a fire signal based on the comparison result of the comparison operation unit. Previous data value stored in advance (P × n), the generated value of the comparison target data t, the n the proportionality constant, a, a b (a +
b = n, | a |> | b |), the past data in the past data storage unit is used as a weighting constant of the same code that satisfies the condition of (a × P + b × t) The differential type heat sensor is configured so that it can be replaced with the value of

According to the first aspect of the present invention, the proportional value (t × n) of the comparison target data t generated every time the temperature value is measured s times and the past data (P × P) relating to the past comparison target data. × n) and the difference (t × n−P × n).
It is determined whether or not a fire has occurred based on this result. Since the past data (P × n) is a value obtained by combining the past comparison target data with a predetermined weight, the storage area is 1
It only needs one. That is, in the prior art, since the past data from which a difference is obtained is data generated a predetermined time ago, it is necessary to store data for a predetermined time. Since only one past data is needed,
The scale of the logic circuit can be reduced. Therefore, the manufacturing cost can be reduced.

The above-mentioned past data is changed from (n × P) to (a × P + b × t) with the generation of the comparison target data t.
, And reflects the past data to be compared, the difference amount (t × n−P × n) is certainly a value related to a change in temperature. Therefore, the function as a differential heat sensor for detecting a rise in temperature is certainly realized.

Further, when the number of times of temperature measurement (s times) at which the comparison target data is generated is plural, there is an effect that the influence of noise at the time of temperature measurement is reduced.
That is, since the comparison target data is generated by synthesizing s (plural) temperature values, even if one of them has noise, the remaining data is a normal value. The effect of noise on the noise is reduced.

Here, the temperature measuring means for measuring the temperature value is, for example, a detecting element (for example, a thermistor) for detecting the temperature by a predetermined electric quantity (for example, voltage value), and converts this electric quantity into first digital data. An A / D converter and correction means for correcting the first digital data to digital data of a primary conversion amount of a temperature value.

[0014] According to the second aspect of the present invention, the data to be compared is set to a value proportional to the average value of the measured continuous s temperature values, so that the influence of noise at the time of temperature measurement is obtained. Can be evenly distributed, and can be set to an appropriate value as comparison target data indicating the current temperature.

[0015] Further, as shown in the invention of claim 3,
When the proportionality constant n is a natural number larger than 1, arithmetic processing in a logic circuit can be simplified, and
By adopting a configuration in which the weighting constants a and b are such that a = n−1 and b = 1, a data value that appropriately reflects past comparison target data to be compared with past data can be obtained.

By setting n to a factorial value of 2, such as "8, 16, 32", an optimum value for a logic circuit can be obtained.

The data to be compared in the first aspect of the present invention is not limited to a value proportional to the average value of s consecutive temperature values, but may be, for example, a value obtained by adding s consecutive temperature values with different weights. Various changes can be made. Also,
The proportional constant n can be an arbitrary real number, and the weighting constants a and b can be appropriately changed from, for example, a time interval for performing temperature measurement, a time for comparing temperature changes, a threshold value, and the like.

According to a fourth aspect of the present invention, in the differential thermal sensor configuration according to any one of the first to third aspects, the past data compared by the comparison operation unit is replaced by the comparison target data. It is configured to be past data (a × P + b × t) newly replaced with the generation.

According to the fourth aspect of the present invention, when calculating the difference amount between the comparison target data and the past data, the comparison target data is a value already included in the past data at a predetermined ratio. Therefore, for example, even if the comparison target data suddenly changes suddenly due to abnormal noise or the like, the sudden change is included in the past data at a predetermined rate. Therefore, the influence of the sudden change due to the abnormal noise or the like is not directly appearing in the difference amount, but is reduced. That is, erroneous fire detection due to abnormal noise or the like can be relatively reduced.

In the invention according to any one of the first to third aspects, the past data used in the operation of the difference amount in the comparison operation unit is newly replaced with the generation of the comparison target data to be compared. The previous past data (n × P) may be used.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG.
3 is a block diagram showing a main part of a circuit configuration of the differential heat sensor 1 according to the embodiment of the present invention. FIG. 2 is a chart showing a conversion table for data conversion performed by the data correction unit 3, and FIG. Is a graph showing the contents of this data conversion table.

The differential heat sensor 1 of this embodiment is of a type that detects a fire by detecting a rise in heat in, for example, a fire alarm system or the like, and includes an A / D converter 2 and a data The logic circuit includes the correction unit 3, the distribution unit 4, the averaging operation unit 5, the storage unit 6, the fire operation unit 7, and the like, and the temperature detection unit 8 and the like. The logic circuits (A / D converter 2, data correction unit 3, distribution unit 4, averaging operation unit 5, storage unit 6, fire operation unit 7) synchronize with a clock signal from a clock circuit (not shown). Operation.

The temperature detector 8 comprises a thermistor R _TH and a resistor R _TH
Are connected in series, and a predetermined voltage V ₊ is applied to them, so that a voltage value representing the temperature is output from the contact s1. The thermistor R _TH is, for example, exposed to a monitoring space where temperature is to be detected. The temperature detector 8 is configured to apply the predetermined voltage V ₊ to the temperature detector 8 at predetermined time intervals under the control of the clock circuit (not shown). With this configuration, a voltage value representing a temperature is output from the contact s1 at predetermined time intervals.

The A / D converter 2 converts the output voltage value from the temperature detector 8 into a digital value and outputs the digital value to the data corrector 3. The data correction unit 3 internally includes a conversion table as shown in FIG. 2, converts output data from the A / D converter 2 into correction data, and outputs the correction data to the distribution unit 4. As shown in FIG. 3, the value of the correction data is a value indicated by a linear function using the temperature value as a variable, and the amount of change in temperature is proportional to the amount of change in the correction data value.

That is, the temperature detecting section 8, the A / D converter 2, and the data correcting section 3 constitute a measuring means for intermittently measuring the temperature.

The distribution unit 4 distributes the output data from the data correction unit 3 into odd-numbered data and even-numbered data, and outputs each of the data to the averaging unit 5 from two output terminals. .

The averaging operation unit 5 calculates an average value t of the odd-numbered data and the even-numbered data as comparison data, and then calculates the average value data (comparison data).
While outputting t to the storage unit 6 from the first output terminal, the average value data (comparison target data) t is multiplied by a proportional constant n and output to the fire calculation unit 7 from the second output terminal. This calculation of the average value is performed once for every two voltage outputs from the temperature detection unit 8. As the proportionality constant n, a factorial value of 2 (for example, “3
2)).

That is, the distribution unit 4 and the averaging operation unit 5
Constitutes a target data generation operation unit that generates the comparison target data by sequentially combining s temperature values by a predetermined calculation formula every s temperature measurements.

In this embodiment, the number s of the temperature value data for generating the data to be compared has been described as two as an example, but it is needless to say that other numbers can be used. Also, the average has been described as an example of the synthesis of s data values.
In addition, various changes can be made, such as simple addition, addition with a predetermined weighting constant added, and various types of integration.

The storage section 6 is for storing past data T (T = n × P) relating to past comparison data. The number of data stored in the storage unit 6 is one, and the data value is converted from a data value originally stored to a new data value according to input of comparison target data. .

This data conversion is based on the following equation, where T _old is the originally stored data value, T _{new is the new} data value, and t is the value of the input comparison data. T _new = T _old × (n-1) / n + t n = 32

The above conversion equation can be expressed by the following equation if the past data T is replaced by n × P. n × P _new = (n−1) × P _old + 1 × t That is, in the past data T, the data value P indicating the past data and the current comparison target data value t are determined by a predetermined weighting constant a (= n− 1) and b (= 1) are added and added. The data value P can be interpreted as data obtained by normalizing the past data T obtained by combining the past comparison target data into one comparison target data. Note that the weighting constants a and b can be appropriately changed by setting a time interval for performing temperature measurement and a threshold value described later. However, (a +
b = n, | a |> | b |).

The storage unit 6 stores the newly converted past data T (T _new ) in response to the input of the comparison target data t.
Is output to the fire calculation unit 7. When the power is turned on, the data obtained by simply adding the output data from the averaging operation unit 5 from the time when nothing is stored in the storage unit 6 to the time when the output from the averaging operation unit 5 is performed n times. The value may be stored in the storage unit 6, or a value obtained by multiplying the output from the first averaging operation unit 5 by n may be stored.

The fire calculation unit 7 calculates the difference between the data (n × t) output from the averaging calculation unit 5 and the data T (T _new ) output from the storage unit 6, and then calculates the difference Is compared with a threshold value (K × n). This comparison processing is based on the following equation. K × n <t × n−T _{new, that} is, K × n <t × n− ｛T _old × (n−1) /
n + t｝

When the difference amount exceeds the threshold value twice or more consecutively, a fire signal is output to, for example, a receiver (not shown) of fire alarm equipment. That is, the fire calculation unit 7 also has a function as fire signal output means. The threshold value K is determined by an experiment or the like.
0 ".

The differential thermal sensor 1 of this embodiment is configured as described above, and operates according to the operation of each part of the logic circuit.
Fire detection is performed as follows. Hereinafter, the operations in the normal case where the temperature is almost constant, in the case of detecting a fire in which the temperature rises sharply, and in the case of inputting transient noise input to the temperature detecting unit 8 will be described.

First, the normal operation will be described. When the monitoring space for monitoring the temperature is constant at, for example, 27 degrees, first, analog data (voltage) corresponding to 27 degrees is output from the temperature detection unit 8 and converted into digital data by the A / D converter 2. Is done. Next, the digitized data is subjected to correction processing in accordance with the conversion table in the data correction unit 3 for calculation processing performed thereafter. When the monitoring space is at 27 degrees, the corrected data value is approximately “42”.

Since the monitoring space is always 27 degrees, the data value output from the data correction unit 3 is continuously "42".
Thus, the odd-numbered and even-numbered data values distributed by the distribution unit 4 are both "42". Therefore, the comparison target data t, which is the average value thereof, is also “42”. Also,
Since it is always 27 degrees, the value T stored in the storage unit 6 is “42 × 32 = 1344”. Then, the following calculation and comparison judgment are performed in the fire calculation unit 7. 32K <32 × 42− (1344 × 31/32 + 4
2) That is, 32K <0, and K is 10, so that no fire signal is output. Here, the description has been made assuming that the temperature of the monitoring space is constant at 27 degrees.
The temperature does not exceed the threshold value in the morning, evening or seasonal temperature change.

Next, the operation when a fire is detected will be described. It is assumed that the temperature of the monitored space has risen from 27 degrees to 50 degrees due to a fire. During this temperature rise, the temperature detection unit 8 performs sampling at predetermined time intervals, and outputs analog data representing the temperature. Therefore, assuming that the temperature increases by 5 degrees every sampling, the data values output from the data correction unit 3 are "42", "45", "50", "53", and "5".
5 ”and“ 58 ”, and accordingly, the average value data (comparison target data) t calculated by the averaging calculation unit 5
Also rise to "43.5", "51.5", and "56.5".

As the average value data increases, the storage unit 6
Is also 1344- (1344/32) + 43.5 = 1345.
5, 1345.5- (1345.5 / 32) + 51.5 = 1
355.5, 1355-(1345.5 / 32) + 51.5 = 136
It changes with 9.

In accordance with this change, the fire calculation unit 7 performs the following calculations (1) to (3) and makes a comparison judgment. (1) 32K <32 × 43.5- (1344 × 31 /
32 + 43.5), that is, 32K <46.5 → K <
1.45 (below threshold) (2) 32K <32 × 51.5− (1345.5 × 3
1/32 + 51.5), that is, 32K <293.1 →
K <9.1 (below threshold) (3) 32K <32 × 56.5− (1355 × 31 /
32 + 56.5), that is, 32K <439 → K <
13.7 (above the threshold) From the above-described conversion formula of the past data T, the rate of increase of the past data T is lower than the rate of increase of the comparison target data t.
After that, the fire calculation unit 7 continues the judgment of the threshold value or more. Therefore, a fire signal is output based on two or more determinations of the threshold value or more.

Next, a description will be given of the case of inputting noise. In a normal monitoring space (27 degrees), it is assumed that the correction data from the data correction unit 3 once becomes "66" corresponding to 60 degrees due to, for example, electric noise. The data of “66” is distributed as odd-numbered (or even-numbered) data in the distribution unit 4. Then, the averaging operation unit 5 averages the normal-time (27 degrees) correction data “42” distributed as the odd-numbered (or even-numbered) data, and the comparison target data t becomes “54”. .

When the comparison target data t affected by the noise is input to the fire calculation section 7, the fire calculation section 7 performs the following calculation and comparison judgment. 32K <32 × 54− (1344 × 31/32 + 54) That is, 32K <372 → K <11.62 (above the threshold value) The fire calculation unit 7 outputs a fire signal when the threshold value is exceeded twice or more consecutively. Therefore, no fire signal is output at this stage.

Since the above-mentioned noise is transient, "4" which corresponds to the normal 27 degrees in the next temperature sampling.
The correction data of “2” is output, and the value of the comparison target data averaged by the averaging calculation unit 5 is also “42”.

Here, since the value of the past data T stored in the storage unit 6 is 1344− (1344/32) + 54 = 1360, the calculation and the comparison judgment in the fire calculation unit 7 are 32K <32 × 42− (1360 × 31/32 + 42) That is, 32K <−15.5 (threshold or less), and the fire signal is not output because the threshold is not continuously exceeded.

As described above, according to the differential heat sensor 1 of this embodiment, the past data T for obtaining the difference amount in the fire calculation unit 7 is obtained by weighting the past comparison target data by the above-mentioned weighting. Since it is a value obtained by adding, only one storage area is required. Therefore, the scale of the logic circuit can be reduced, and the manufacturing cost can be reduced.

The above-mentioned past data T is changed from “T” to “T × (n−
1) / n + t ”, which is a value reflecting the data to be compared in the past, so that the difference amount in the fire calculation unit 7 is certainly a value related to a change in temperature, and the differential heat sensing is performed. Realize the function of the container.

The comparison data obtained by the fire calculation unit is obtained by averaging two output data from the temperature detection unit 8. Therefore, even if noise is added to the output from the temperature detection unit 8, the data is compared. The impact is halved for the comparison data. Therefore, the false detection of fire due to noise is reduced,
Improve the reliability of fire detection.

When calculating the difference between the comparison target data and the past data, since the comparison target data t is a value already included at a predetermined ratio in the past data T, for example, an abnormal noise Even if the data to be compared suddenly changes accidentally due to, for example, the sudden change, the past data T
Will also be included. Therefore, the influence of the sudden change due to the abnormal noise or the like is not directly appearing in the difference amount, and the difference amount is reduced.

It should be noted that the present invention is not limited to the differential heat sensor 1 of this embodiment. For example, the values of the proportional constant n and the weighting constants a and b can be changed.
The configuration of the logic circuit and the heat detection unit 8 specifically shown can be appropriately changed without departing from the spirit of the invention.

[0051]

As described above, according to the present invention, in a differential heat sensor for detecting a fire based on the rate of temperature rise,
It is possible to use only one storage area for storing data relating to the past temperature, and as a result, it is possible to reduce the scale of the entire logic circuit and reduce the manufacturing cost. In addition, since the comparison target data indicating the current temperature is obtained by s times of temperature measurement, even if noise is added at the time of temperature measurement, the influence can be reduced. Therefore, false detection due to noise can be reduced, and the reliability of fire detection can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a circuit configuration of a differential heat sensor according to an embodiment of the present invention.

FIG. 2 is a chart showing a conversion table for data conversion performed by a data correction unit.

FIG. 3 is a graph showing contents of a data conversion table of FIG. 2;

FIG. 4 is a block diagram illustrating a configuration of a storage unit that stores a past temperature value in a differential heat sensor using a conventional logic circuit.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 differential heat sensor 2 A / D converter 3 data correction unit 4 data distribution unit 5 averaging calculation unit 6 storage unit 7 fire calculation unit R _TH thermistor R resistance

Claims (4)

[Claims] A temperature measuring means for intermittently measuring a temperature value, and a sequence of measured s temperature values which are successively combined by a predetermined calculation formula, thereby obtaining one A target data generation operation unit for generating comparison target data; a past data storage unit for storing past data relating to comparison target data generated in the past; t representing the value of the generated comparison target data; A comparison operation for calculating the difference amount (t × n−P × n) using the stored past data as (P × n) and n as a predetermined proportional constant, and comparing the difference amount with a preset threshold. And a fire signal output means for outputting a fire signal based on the comparison result of the comparison operation unit, wherein the value of the past data stored in the past data storage unit in advance (P × n) is generated. The values of the data to be compared are represented by t and n Constant, a, a b (a + b = n, | a |
> | B |) that the past data in the past data storage unit is replaced with the value of (a × P + b × t) with the generation of the comparison target data, Features a differential heat sensor. 2. The differential heat sensor according to claim 1, wherein the comparison target data is a value proportional to an average value of the measured s consecutive temperature values. 3. The difference according to claim 1, wherein the proportionality constant n is a natural number larger than 1, and the weighting constants a and b are a = n−1, b = 1. Dynamic heat detector. 4. The past data compared by the comparison operation unit is past data (a × P + b × t) newly replaced with generation of comparison target data to be compared. Item 4. A differential heat sensor according to any one of Items 1 to 3.