thermal sensor

Abstract

To provide a heat sensor capable of preventing malfunction when a temperature around the heat sensor drops instantaneously.SOLUTION: A heat sensor 1 includes a temperature detection element 3 and a control unit 5 for determining fire based on an output of the temperature detection element 3. The control unit 5 normally operates in a first mode in which fire determination is performed based on an output of the temperature detection element 3. When non-fire variations of a temperature around the heat sensor 1 is detected based on the output of the temperature detection element 3, the control unit is adopted to determine fire by shifting to a second mode different from the first node.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heat detector. [Background technology]

[0002] Conventionally, there are heat detectors, such as those used in automatic fire alarm systems and heat detection fire alarms. Heat detectors are equipped with a temperature detection element such as a thermistor, and are designed to determine a fire when the output value of the temperature detection element exceeds a certain value.

[0003] Heat detectors are divided into differential heat detectors (hereinafter referred to as differential heat detectors) and constant temperature heat detectors (hereinafter referred to as constant temperature heat detectors) depending on the specifications for fire detection. Differential heat detectors are designed to detect a fire when they compare the current temperature around the heat detector with the temperature around the heat detector from a certain time ago, based on the output of the temperature detection element (see Patent Document 1). Constant temperature detectors are designed to detect a fire when they detect that the temperature around the heat detector has exceeded a threshold, based on the output of the temperature detection element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-168914 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, conventional differential heat detectors would determine a fire when they detected a certain temperature rise, regardless of the actual temperature around the detector. Therefore, if there was a change in the temperature around the detector that was not caused by a fire (hereinafter referred to as a non-fire change), the detector would determine whether a fire had occurred based on that temperature change.

[0006] For example, a non-fire-related change in temperature around a heat detector can occur in a heated room in winter when a window or door is opened for ventilation, allowing cold air from the outside to enter the room and causing an instantaneous drop in the temperature around the heat detector. In conventional differential heat detectors, if the temperature around the heat detector drops due to the cold air, a fire is determined when a predetermined temperature rise is detected based on the dropped temperature.

[0007] Therefore, conventional differential heat detectors could malfunction if the temperature around the detector simply dropped momentarily and then returned to its original temperature, because the temperature difference between the dropped temperature and the original temperature could lead to the detector determining that there is a fire.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a heat detector that can prevent false activation due to non-fire-related fluctuations in the temperature around the heat detector. [Means for solving the problem]

[0009] The present invention is a heat detector comprising a temperature detection element and a control unit that performs a fire detection based on the output of the temperature detection element, wherein the control unit normally operates in a first mode that performs a fire detection based on the output of the temperature detection element, and when a non-fire fluctuation in the temperature around the heat detector is detected based on the output of the temperature detection element, the control unit switches from the first mode to A fire is detected based on the output of the temperature detection element. Switch to the second mode and make the fire determination, wherein the second mode is different from the first mode; The first mode is a differential mode that determines whether a fire has occurred when a temperature rise above a set value is detected, and the second mode is a constant temperature mode that determines whether a fire has occurred when a temperature above a threshold value is detected.

[0011] The present invention can define the non-fire fluctuation as a temperature drop of a certain level or more around the heat detector. 。

[0012] Furthermore, in the present invention, the control unit may be configured to transition from the second mode to the first mode when it is determined that the non-fire fluctuation has been resolved. 。

[0013] In addition, although the terms "first" and "second" are used in the present invention, these are used only to distinguish between configurations, and the number and order thereof do not have any particular significance. [Effects of the Invention]

[0014] The present invention normally operates in a first mode in which a fire detection is made based on the output of the temperature detection element, and when a non-fire fluctuation in the temperature around the heat detector is detected based on the output of the temperature detection element, it transitions from the first mode to a second mode different from the first mode in which the fire detection is made, thereby making it possible to prevent the heat detector from malfunctioning due to the non-fire fluctuation.

[0015] In another aspect of the present invention, when a temperature drop of a certain level or more, which is an example of a non-fire fluctuation in the temperature around the heat detector, is detected based on the output of the temperature detection element, the temperature rise immediately thereafter is not judged to be a fire, thereby making it possible to prevent malfunction when the temperature around the heat detector drops suddenly. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a longitudinal sectional view of first to third embodiments of the present invention. FIG. [Figure 2] FIG. 1 is a block diagram of a first embodiment of the present invention. [Figure 3] FIG. 1 is a flow diagram of a first embodiment of the present invention. [Figure 4] FIG. 10 is a flow diagram of a second embodiment of the present invention. [Figure 5] FIG. 10 is a flow diagram of a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] A first embodiment of the present invention will be described with reference to Figures 1 to 3. First, the configuration of a heat detector of this embodiment will be described using a heat detector used in an automatic fire alarm system as an example. The heat detector 1 is attached to, for example, a ceiling C, and includes a housing 2, a thermistor 3, a circuit board 4, a control unit 5, and an internal temperature detection unit 6.

[0018] The housing 2 has a main body 2a and a protective part 2b. The main body 2a contains a circuit board 4 and other components. The protective part 2b is provided to protect the thermistor 3 from external forces, and in this embodiment, it is provided so as to protrude from the ceiling C toward the room R.

[0019] The thermistor 3 is an example of a temperature detection element, and is provided to measure the temperature around the heat detector 1. The thermistor 3 has a detection unit 3a at its tip for detecting the temperature around the heat detector 1. In this embodiment, the thermistor 3 is provided so that the detection unit 3a is located inside the protective unit 2b of the housing 2, and the detection unit 3a is exposed to the room R side.

[0020] The circuit board 4 is provided within the main body 2a of the housing 2, and is equipped with a thermistor 3 as well as various elements (not shown), such as a microcomputer that constitutes the control unit 5 that makes a fire detection determination based on the output of the thermistor 3, and a temperature sensor that constitutes the internal temperature detection unit 6 for detecting the temperature inside the housing 2.

[0021] The internal temperature detection unit 6 is provided to measure the temperature inside the housing 2, in this embodiment, inside the main body 2a. The position where the internal temperature detection unit 6 is provided can be selected appropriately as long as it does not interfere with the detection of the temperature inside the housing 2. As the internal temperature detection unit 6, various known temperature sensors such as a chip thermistor can be used as needed.

[0022] The control unit 5 has a recording unit 5a, a fire determination unit 5b, and a sampling unit 5c. The sampling unit 5c acquires the output of the thermistor 3 or the internal temperature detection unit 6 according to a mode described below, and records the temperature around the heat detector 1 based on the output of the thermistor 3 or the temperature inside the housing 2 based on the output of the internal temperature detection unit 6 (hereinafter, these two temperatures are collectively referred to as the detected temperature) in the recording unit 5a.

[0023] The recording unit 5a records the detected temperature for a certain period of time. The fire detection unit 5b compares the current detected temperature recorded in the recording unit 5a with the detected temperature from a certain period of time ago, and outputs a fire detection signal when it detects a predetermined temperature rise.

[0024] Next, we will explain the operation of the heat detector 1 of this embodiment regarding fire detection. The heat detector 1 operates in either a first mode in which it performs fire detection based on the output of the thermistor 3, or a second mode in which it performs fire detection based on the output of the internal temperature detection unit 6.

[0025] In the first mode, the thermistor 3 operates at predetermined intervals, its output is acquired by the sampling unit 5c, and the temperature around the heat detector 1 based on the output of the thermistor 3 is recorded in the recording unit 5a of the control unit 5. At approximately the same time, the fire determination unit 5b compares the current temperature around the heat detector 1 recorded in the recording unit 5a with the temperature around the heat detector 1 a certain time ago, and if it detects a predetermined temperature rise, the fire determination unit 5b determines that there is a fire and sends a fire signal to a fire receiver (not shown).

[0026] The control unit 5 transitions to the second mode when it detects, based on the output of the thermistor 3, a temperature drop of a certain amount or more in the temperature around the heat detector 1, which is an example of a non-fire fluctuation in the temperature around the heat detector, compared with the temperature around the heat detector 1 a certain time ago. In the second mode, the sampling unit 5c acquires the output of the internal temperature detection unit 6 and records the temperature inside the housing 2 based on the output of the internal temperature detection unit 6 in the recording unit 5a. At approximately the same time, the fire detection unit 5b compares the current temperature inside the housing 2 recorded in the recording unit 5a with the temperature inside the housing 2 a certain time ago, and if it detects a predetermined temperature increase, the fire detection unit 5b determines that there is a fire and transmits a fire signal to a fire receiver (not shown).

[0027] In this embodiment, even after transitioning to the second mode, the thermistor 3 continues to operate at predetermined intervals, and when the control unit 5 determines that the temperature around the heat detector 1 based on the output of the thermistor 3 is approximately the same temperature as the temperature inside the housing 2 based on the output of the internal temperature detection unit 6 or is below a set temperature difference, the heat detector 1 transitions from the second mode to the first mode again.

[0028] The temperature change inside the housing 2 is relatively slow compared to the temperature around the heat detector 1, and is unlikely to change unless the temperature around the heat detector 1 changes continuously to a certain extent. Therefore, the impact of a momentary drop in the temperature around the heat detector 1 when cold air blows in, etc., is unlikely to be significant enough to affect the fire detection.

[0029] Therefore, in this embodiment, when a temperature drop of a certain level or more in the temperature around the heat detector 1 is detected, the device switches to the second mode, thereby preventing malfunctions due to a momentary drop in the temperature around the heat detector 1. When a fire occurs, the heat will cause the temperature around the heat detector 1 to rise, but because this temperature change is continuous, the temperature inside the housing 2 will also change in response to the temperature change around the heat detector 1, making it possible to make a fire judgment without any particular problems.

[0030] A second embodiment of the present invention will be described with reference to Fig. 4. The difference between this embodiment and the first embodiment is that the second mode is a constant temperature mode. The basic configuration of the heat detector 1 is the same as that of the first embodiment, so a description thereof will be omitted.

[0031] In this embodiment, the threshold value is recorded in the recording unit 5b of the control unit 5. Furthermore, in this embodiment, whether or not the heat detector 1 is provided with an internal temperature detection unit 6 is optional.

[0032] Regarding the operation of the heat detector 1 of this embodiment for fire detection, the heat detector 1 normally operates in differential mode. This differential mode is the same as the first mode of the first embodiment. When the control unit 5 detects a temperature drop of a certain level or more based on the output of the thermistor 3, it transitions from the differential mode to constant temperature mode.

[0033] In the constant temperature mode, the fire detection unit 5b of the control unit 5 compares the current temperature around the heat detector 1 recorded in the recording unit 5a with the threshold value recorded in the recording unit 5a, and when it detects that the temperature is above the threshold value, it determines that there is a fire and issues a fire notification.

[0034] Furthermore, for example, it is also possible to transition from the constant temperature mode to the differential mode again after a certain period of time has elapsed since the constant temperature mode, or when the control unit 5 determines that the temperature around the heat detector 1 has stabilized.

[0035] By doing this, while the heat detector 1 is operating in the constant temperature mode, even if there is a momentary drop in the temperature around the heat detector 1, such as when cold air is blown in, a fire will not be detected unless the temperature reaches or exceeds the threshold value.Therefore, in this embodiment, malfunctions due to momentary drops in the temperature around the heat detector 1 are prevented.

[0036] A third embodiment of the present invention will be described with reference to Fig. 5. The difference between this embodiment and the first embodiment is that the second mode is not provided in the operation related to fire detection by the heat detector 1. The basic configuration of the heat detector 1 is the same as that of the first embodiment, so a description thereof will be omitted. In this embodiment, it is optional whether or not to provide the heat detector 1 with an internal temperature detection unit 6.

[0037] The operation of the heat detector 1 of this embodiment for determining a fire will be explained. Normally, the heat detector 1 operates in the same manner as in the first mode of the first embodiment. When the control unit 5 detects a temperature drop of a certain level or more around the heat detector 1 based on the output of the thermistor 3, the control unit 5 records the temperature. a The system does not record any information or ignores any information recorded, so that the temperature rise around the heat detector 1 immediately after the incident is not judged to be a fire.

[0038] In this way, in this embodiment, a momentary drop in the temperature around the heat detector 1 is ignored and not used as a criterion for determining whether a fire has occurred, thereby preventing malfunctions due to a momentary drop in the temperature around the heat detector 1. Furthermore, if a fire occurs, it is understood that the rise in the temperature around the heat detector 1 will continue, so it is possible to perform a fire determination without any problems even if the temperature rise immediately after the temperature drop around the heat detector 1 is ignored.

[0039] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the invention. For example, although the present invention is configured to transition from one mode to the other, it is also possible to operate the first mode and the second mode simultaneously under normal circumstances to determine whether a fire has occurred.

[0040] (1) In the above embodiment, a heat detector used in an automatic fire alarm system has been described as an example, but the present invention can also be applied to a heat detection type fire alarm. In this case, the heat detector 1 is provided with an acoustic device (not shown), and the control unit 5 issues a fire alarm using the acoustic device when it determines that a fire has occurred.

[0041] (2) The present invention is applicable to various existing heat detectors. In this case, the internal temperature detection unit 6 may be an existing temperature sensor or the like in the heat detector that can detect the temperature inside the housing 2, or a separate temperature sensor or the like may be attached.

[0042] (3) In the above embodiment, the internal temperature detection unit 6 detects the temperature inside the housing 2. However, it is also possible to provide multiple thermistors 3 with different sensitivities and use the less sensitive of the thermistors 3 as the internal temperature detection unit 6.

[0043] (4) In the above embodiment, the transition from the first mode to the second mode is made based on the detection of a temperature drop of a certain level or more around the heat detector 1 based on the output of the temperature detection element. However, if necessary, the transition from the first mode to the second mode can also be made based on the detection of a non-fire fluctuation in the temperature around the heat detector 1 other than a temperature drop, such as a temperature increase not caused by a fire. In this case, when the control unit 5 determines that the non-fire fluctuation in the temperature around the heat detector 1 has been resolved, the transition from the second mode to the first mode again can also be made. [Explanation of symbols]

[0044] 1 heat detector 2 housing 2a main body 2b Protection part 3 Thermistor 3a Detection part 4 Circuit board 5 Control unit 5a Recording unit 5b Fire detection unit 5c Sampling unit 6 Internal temperature detection unit C Ceiling R Indoor

Claims

1. A heat detector comprising a temperature detection element and a control unit that determines whether a fire has occurred based on the output of the temperature detection element, The control unit normally operates in a first mode in which a fire is judged based on the output of the temperature detection element, and when a non-fire variation in the temperature around the heat detector is detected based on the output of the temperature detection element, the control unit shifts from the first mode to a second mode in which a fire is judged based on the output of the temperature detection element, and judges the fire, and here, the second mode is different from the first mode in that: The first mode operates as a differential mode in which a fire is determined when a temperature rise exceeding a set value is detected, The heat detector is characterized in that the second mode operates as a constant temperature mode in which a fire is determined when a temperature equal to or higher than a threshold value is detected.

2. 2. The heat detector according to claim 1, wherein the non-fire fluctuation is a temperature drop of a certain level or more around the heat detector.

3. 3. The heat detector according to claim 1, wherein the control unit transitions from the second mode to the first mode when it determines that the non-fire fluctuation has been resolved.

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