JPH0290293A - Differential type heat sensor - Google Patents

Abstract

PURPOSE:To attain highly accurate heat sensing by sending a decision signal to a switching circuit when abnormality is generated in either one of abnormality judgement for moderate temperature rise and abnormality judgement for a sudden temperature rise and generating an alarm signal. CONSTITUTION:An analog signal corresponding to a temperature detected by a heat sensitive element 1c is converted into a digital signal by an A/D converter 1d and a CPU 1e executes abnormality judgement for a moderate temperature rise or abnormality judgement for a sudden temperature rise. When either one of these judgement is judged as an abnormal judgement, the CPU 1e sends a discriminating signal to a switching circuit 1g, the circuit 1g shorts a power supply circuit 1a and generates an alarm signal and the data processed by the CPU 1e are stored in a memory 1f circuit. Consequently, a highly accurate differential type heat sensor can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to an improvement of a differential heat sensor that outputs an alarm signal when the degree of temperature rise exceeds a predetermined value.

[Prior Art] Conventional differential heat sensors are configured to issue an alarm signal only when the temperature rises rapidly to a certain extent.
FIG. 4 is a diagram showing the configuration of such a differential heat sensor 100. In the figure, when the differential heat sensor 100 receives a rapid temperature rise, the air in the heat sensitive chamber 101 expands, pressurizing the diaphragm 102 and closing the contact 104 to issue an alarm. The leak hole 103 maintains a balance with the external pressure and prevents false alarms from being issued.

Although the differential heat sensor described above is constructed mechanically, the circuit example shown in FIG. 5 is electrically constructed as a differential heat sensor. To explain its operation, the power supply voltage vCC is divided by resistor R1 and thermistor TH and applied to the base of transistor Q.
The emitter of is grounded through the parallel connection of resistor R2 and capacitor C. Furthermore, the base of the transistor Q is connected to the inverting input terminal of the comparator CMP, and the emitter is connected to the non-inverting input terminal of the comparator CMP.
When there is no temperature change, the charge on capacitor C is
2, the base of the transistor Q has a potential higher than the emitter by approximately 0.6 volts, and the output of the comparator CMP is at the rLJ level and the switching circuit 2
01 is not driven, so no alarm signal is output, but if the ambient temperature rises rapidly, the thermistor TH
The resistance value of capacitor C decreases rapidly depending on the temperature, while the charge of capacitor C is discharged through resistor R2 with time constant τ=C-R2 and its terminal voltage decreases, but the emitter potential of transistor Q decreases. The base potential decreases faster than the base potential, and when the difference between the base potential and the emitter potential becomes approximately 0.6 volts or less, the transistor Q turns off, and when the emitter potential becomes higher than the base potential, the output of the comparator CMP changes. The level reaches the rHJ level, the switching circuit 201 is driven, and an alarm signal is output.

However, in the differential heat sensor 100 having the mechanical configuration shown in FIG. It is very complicated and has the disadvantage that the degree of temperature rise at the time of alarm cannot be easily changed.

In addition, in the differential heat sensor configured as shown in Fig. 5 above, the time constant of the discharge circuit composed of capacitor C and resistor R2 becomes large, so the accuracy of the time constant is affected by the leakage current of capacitor C and variations in capacitance. As a result, the degree of temperature rise cannot be detected with high accuracy, and it is desired to develop a method that allows highly accurate heat sensing using a simple method.

[Problem B to be solved by the invention] The present invention proposed to solve the above problems converts an analog signal corresponding to the temperature detected by a heat-sensitive element into a digital signal and processes it in a CPU. It is an object of the present invention to provide a differential heat sensor that can perform highly accurate heat sensing by detecting abnormalities in both rapid and slow temperature increases. Furthermore, the present invention, proposed at the same time, aims to provide a heat sensor that achieves energy savings by using an intermittent drive circuit in the heat sensor having the above configuration.

[Means for Solving the Problems] The present invention proposed to achieve the above object uses a differential heat sensing system that issues an alarm signal when the degree of rise in room temperature exceeds a predetermined degree. The device includes a heat-sensitive element that detects temperature and outputs an analog signal corresponding to the temperature, an A/D conversion circuit that converts the analog signal from the heat-sensitive element into a digital signal at a predetermined cycle, and a digital signal that converts the digital signal. a CPU that determines whether or not the degree of temperature increase exceeds a predetermined degree;
a memory circuit that stores data processed by the CPU; a switching circuit that receives a determination signal from the CPU as a result of the CPU's determination processing and outputs an alarm signal; and a power source that drives the internal circuit including the CPU. The determination of the temperature rise made by the CPU includes a determination of abnormality in response to a slow temperature increase and a determination as abnormality in response to a rapid temperature increase, and if any of these determinations is abnormal, When there is a problem, the CPU is configured to send a determination signal to the switching circuit and issue an alarm signal.

Further, in the present invention proposed at the same time, the power supply from the power supply circuit to the internal circuit including the CPU is intermittently supplied by an intermittent drive circuit.

[Function] In the differential heat sensor of the present invention, the analog signal corresponding to the temperature detected by the heat-sensitive element is converted into a digital signal by the A/D conversion circuit, and based on the data of this digital signal, the CPU Determination of abnormality due to slow temperature rise,
An abnormality judgment is made regarding the rapid temperature rise, and if any of these judgments is judged to be abnormal, the CPU
sends a discrimination signal to the switching circuit, the switching circuit short-circuits the power supply circuit and issues an alarm signal,
Data processed by the CPU is stored in a memory circuit.

Furthermore, in the present invention proposed at the same time, power consumption is reduced because power is intermittently supplied to each circuit section of the differential heat sensor using an intermittent drive circuit.

[Example] The present invention will be described in detail below with reference to the drawings.

Fig. 1 shows a block diagram of the configuration of the differential heat sensor of the present invention, where la is a power supply circuit that supplies DC power to the internal circuit, and 1b is a power supply circuit that supplies power from the power supply circuit to each circuit section. An intermittent drive circuit for intermittent supply; 1c is a thermosensitive element that detects temperature and obtains an analog electrical signal corresponding to the temperature; 1d is A that converts the analog electrical signal from the thermosensitive element into a digital signal at a predetermined period. /D conversion circuit, 1e
CPtJ is for processing digital signals, if is for storing data from the CPU, and 1g is a switching circuit that outputs an alarm signal upon receiving the determination signal from the CPU 1e to short-circuit the power supply circuit la.

In the differential heat sensor 1 having such a configuration, an analog signal corresponding to the temperature of the heat sensing element 1c is converted into a digital signal by the A/D conversion circuit 1d at a constant period determined by the intermittent drive circuit 1b, and the analog signal is converted into a digital signal by the A/D conversion circuit 1d. The degree of each temperature rise is calculated by comparing with the previous data of a plurality of predetermined time intervals, and one of these degrees of temperature rise is determined to be the specified value. @ If the CPU 1e outputs a determination signal to the switching circuit 1g,
It operates to short-circuit the human power of the power supply circuit 1a and issue an alarm signal. Furthermore, data processed by the CPU 1e is stored in the memory circuit 1f.

Next, Figure 2 shows this operation graphically.
In the figure, the horizontal axis is the elapsed time and the vertical axis is the temperature. When the data of the temperature TI at time t1 is input to the CPU 1e, the temperature data TI at this time tl and the time t
The CPU 1e calculates the temperature increase rate αa=(TI-To>/(tl-tO) from the temperature TO at time to before l.
is calculated and compared with the predetermined temperature rise TA for the time interval (tl-to), and the temperature rise is
If the temperature rise exceeds TA, it is considered a fire and an alarm is issued, and if the temperature rise does not exceed TA, it is not determined to be a fire.
That is, in this way, it is determined that there is an abnormality in response to a rapid temperature rise.

Furthermore, if it is not determined that there is a fire based on the above temperature increase rate, the temperature increase rate αa= ( TI-TO)/ (t
1-tO'), and if this rate of temperature rise αa' exceeds the specified value TB, it is assumed that a fire has occurred and an alarm is issued. In this case, it is determined that there is an abnormality in response to a slow temperature rise.

Therefore, in the graph shown by a in Fig. 2, an alarm is issued due to a temperature rise in TI that exceeds the specified value TA in a short period of time from time 10 to tl due to a sudden rise in temperature due to a fire, but in the graph shown by b in Fig. In the case of a temporary temperature rise that is not caused by a fire, as in the case of a temporary temperature rise that is not caused by a fire, the temperature rise during the period from time to to tl does not exceed TA, so no W alarm signal is output. Also, C in the diagram
In the graph shown in , the time to '
Since the temperature gradually rises over a long period of time from to time tl and exceeds the specified value TB, it is determined that there is a fire and an alarm signal is output. However, in the graph shown by d in the figure, since the temperature rise during the period from time tO' to time t1 does not exceed the specified value [TB], it is determined that there is a fire and no alarm signal is output. In addition, in FIG. 2, for convenience of explanation, the temperature change curve a
-d's temperature at time tO' is aligned with TO, but
In reality, they are rarely the same, and for curves a and b, an alarm is issued if the temperature rise between time tl and 10 is greater than TA, and for curves c and d, it is issued between time t1 and 10.
If the temperature rise between ' is equal to or greater than TB, an alarm will be issued.

Furthermore, FIG. 3 shows this operation in a flowchart. In step 1000, power is supplied to each circuit section by the intermittent drive circuit lb, the temperature is read by the thermosensitive element IC, and the read analog signal is is step 100
1, it is converted into a digital signal by the A/D conversion circuit 1d, and in step 1002, the temperature difference between the temperature T1 at time tl and the temperature TO at time 10 is determined as a specified value T.
If it exceeds A, the process proceeds to step 1005 where an alarm signal is output, and then, in step 1004, the data processed by the CPU Ie is stored in the memory circuit if. That is, in step 1002, the rapid temperature rise is deemed to be abnormal.

Further, if the temperature difference is less than or equal to TA in step 1002,
In step 1003, temperature TI at time t1 and time t
If the temperature difference from the temperature TO at o+ exceeds the specified value TB, the process proceeds to step 1005 and outputs an alarm signal, and if the temperature difference does not exceed the specified value ([TB), step 10
The data is saved in step 04, and the temperature is read again in step 1000.

In addition, although the above embodiment shows an example in which the time interval for calculating the degree of temperature rise is set for two types, a slow temperature rise and a rapid temperature rise, the time interval is not limited to this example. It is also possible to have more than one type of time interval.

In addition, in the above embodiment, the intermittent drive circuit 1b supplies power to each circuit section intermittently to achieve energy saving. It is also possible to capture temperature data at intervals.

[Effects of the Invention] The differential heat sensor of the present invention outputs an alarm signal early in the event of a sudden temperature rise, and even if the temperature rises gradually, the time interval can be adjusted to detect an abnormality. It is possible to provide a highly accurate differential heat sensor that is not affected by leakage current or capacitance error because it does not use a capacitor.

Furthermore, in the present invention proposed at the same time, an energy-saving differential heat sensor can be provided by applying an intermittent drive circuit to the differential heat sensor described above.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a graph showing its operation, Fig. 3 is a flowchart showing its operation, and Fig. 4 is a conventional mechanical differential heat sensing sensor. FIG. 6 is a diagram showing the structure of the device, and is a circuit diagram of a main part when a differential heat sensor is constructed using an electronic circuit. [Explanation of symbols] 1a...Power supply circuit lb...Intermittent drive circuit lc...Thermal element 1d...A/D conversion circuit le...CPU If.1 Memory 1g...Switching circuit

Claims (2)

[Claims] (1) In a differential heat sensor that issues an alarm signal when the degree of rise in room temperature exceeds a predetermined level, a heat-sensitive element that detects temperature and outputs an analog signal corresponding to the temperature. an A/D conversion circuit that converts the analog signal from the heat-sensitive element into a digital signal at a predetermined period; and an A/D conversion circuit that takes in the digital signal and determines whether the degree of temperature rise exceeds a predetermined level a memory circuit that stores data processed by the CPU; a switching circuit that receives a determination signal from the CPU as a result of the CPU's determination process and outputs an alarm signal; and an internal circuit that includes the CPU. and a power supply circuit for driving the circuit, and the temperature rise determination made by the CPU includes an abnormality determination for a slow temperature rise and an abnormality determination for a rapid temperature rise, and any of these A differential heat sensor characterized in that, when there is an abnormality in the determination, the CPU sends a determination signal to a switching circuit to issue an alarm signal. (2) The differential heat sensor according to claim 1, wherein the power supplied from the power supply circuit to the internal circuit including the CPU is intermittently supplied by an intermittent drive circuit.