JPH03246698A - Heat sensor - Google Patents

Abstract

PURPOSE:To make it possible to inspect a heat sensor by remote control by providing the heat sensor with an inspection circuit for inputting a dummy sensing input to a decision part similarly to the detection of a fire by a heat sensing element at the time of inputting an inspection signal. CONSTITUTION:An inspection signal line T for sending an inspection signal from the side of a fire receiver is previously wired, and the inspection circuit 2 for boosting a voltage impressed to both terminals of a resistor R1 up to the level to be obtained at the time of generating a fire and forming a dummy fire state is arranged in the heat sensor. When a short-circuit is formed between the signal line T and a common line C at the time of an inspection, a transistor Q1 is turned on and the same state as the reduction of the resistance value of a thermistor Rth is formed. Consequently, the heat sensor can be inspected by remote operation for inputting the inspection signal from the signal line T, so that the heat sensor can be detected without going to its installation field.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat sensor that detects fire by sensing ambient temperature.

[Conventional technology] Figure 3 shows the circuit configuration of a constant temperature type heat sensor.

In this heat sensor, the driving voltage Vcc is set to the thermistor Rth.
and the resistor R1, and the voltage Vo across the resistor R1 is monitored by the determination unit 1 to detect a fire. Here,
The voltage across the resistor R1 (20) can be expressed as follows. That is, the resistance value of the thermistor Rth decreases as the ambient temperature rises, and the voltage 0 across the resistor R increases as shown in FIG.

Here, for example, if the determination unit 1 determines that there is a fire when the voltage Vo across the resistor R7 becomes v1 or more, the determination unit 1 will output a fire signal when the ambient temperature is 70°C. Ru. In this type of heat sensor, the load ML of the sensor line and the common line C are short-circuited to output a fire signal to a fire receiver or the like. Note that the thermistor R1h may be connected to the ground side.

In addition, there are differential types of this type of heat sensor.
In this differential type heat sensor, the determination unit 1 detects the rate of change of the ambient temperature with respect to time, and for example, the temperature change from the ambient temperature of 40°C to 70°C in Fig. 4 (as seen by the voltage Vo across the resistor R1). and 1JVo=V + -V z ) occur in one minute, it is determined that there is a fire.

Issue I11 that the L invention seeks to solve By the way, this type of heat sensor has a legal obligation to perform maintenance and inspection. Therefore, in the past, inspections were carried out using a heating tester at the site where the heat detector was installed. If this inspection is installed in a residential building such as a condominium, it is necessary to enter each residence and perform the above inspection, and if the above inspection cannot be carried out due to reasons such as the absence of the resident, etc. was there. In addition, there are cases where inspection work on the heat sensor is dangerous, such as in electrical rooms, for example, and inspection in such cases is virtually impossible.

The present invention has been made in view of the above points, and its purpose is to provide a heat sensor that does not require on-site inspection.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a heat-sensitive element that is provided with a terminal for connecting an inspection signal line through which an inspection signal is sent, and that senses the ambient temperature when the inspection signal is input. The test circuit is equipped with an inspection circuit that inputs a pseudo sensing input similar to that in the case where a fire is detected to a determination section that determines whether there is a fire.

In addition, in order to be able to perform appropriate operation tests within the operating ambient temperature range, the QN
The above-mentioned inspection circuit may be provided with temperature characteristics that correct errors caused by changes in the thermal element.

[Function] By having the above-described configuration, the present invention enables the heat sensor to be inspected by remote control that inputs an inspection signal from the inspection signal line.

[Example 1] FIG. 1 shows a case where the present invention is applied to a constant temperature type heat sensor. In the case of this embodiment, in addition to the sensor line that connects the fire reception m (which may be a repeater in a distributed processing type self-fire alarm system) and the heat detector, the inspection signal is sent to the fire receiver side. Wire the inspection signal line T sent from the inspection signal line in advance, and when the inspection signal is input from the inspection signal line, increase the voltage across resistor R8 to the voltage at the time of fire occurrence to create a pseudo fire condition. The inspection circuit 2 is provided in the heat sensor. The detection circuit 2 to this 7 has a transistor Q3 on both ends of the thermistor Rth.
, resistors R2, R, are connected, and the transistor Q1 is turned on by a check signal, and a thermistor Rt is connected in parallel to the resistor R2.

In this embodiment, during inspection, the inspection signal line T and the common line C
When a short circuit is made between the two, the transistor Q is turned on and the resistance value of the thermistor Rth is reduced. Here, the voltage V across the resistor R at this time
o is set to be 1.25 times the nominal operating temperature of the heat sensor (the upper limit of the certification standard). The reason why the thermistor Rt is connected in parallel to the resistor R2 in the inspection circuit 2 is that the inspection circuit 2 also has temperature characteristics.
This is to correct an error caused by a change in the resistance value of the thermistor Rth depending on the ambient temperature at the time of inspection, and in this way, an appropriate operation test can be performed within the operating ambient temperature range. Here, if the voltage across resistor R1 is V when the temperature is 1.25 times higher than the nominal operating temperature, then """" 1(Rt//R+)+R,l//Rth+R
However, the saturation voltage Vsat of the transistor Q1 is ignored.

becomes. Note that since the transistor Q1 is normally off, it does not have any effect on the heat sensing operation of the heat sensor.

[Embodiment 2] Fig. 2 shows a case in which the present invention is applied to a differential heat sensor. In this embodiment, as shown in Fig. 2, the resistor R1 is a thermistor. The configuration of the inspection circuit 2 is exactly the same as that of the constant temperature type.

In the following description, the thermistor on the drive voltage fiVee side will be referred to as Rth, and the thermistor on the ground side will be referred to as Rth2.

In the case of this embodiment, the thermistor Rt and the resistors R2 and R.

The settings are different. Here, with a differential heat sensor, is there a change in ambient temperature? ! ! For example, t is 30℃ (certification standard)
Check whether the fire signal is output normally when Therefore, if the voltage across the thermistor Rth is JVo in the case of 4t, when the transistor Q is turned on, the voltage across the thermistor Rth2 is Vo+J
It is sufficient if it becomes Vo. Expressing this in the formula is Vo+V.

becomes.

[Effects of the Invention 1] As described above, the present invention is provided with a terminal for connecting an inspection signal line through which an inspection signal is sent, and has a terminal that connects the inspection signal line to which an inspection signal is sent. Since it is equipped with an inspection circuit that inputs a similar pseudo-sensing input to the judgment unit that determines whether there is a fire, the heat sensor can be inspected by remote control by inputting an inspection signal from the inspection signal line. Since it is possible to inspect heat detectors without going to the site, it is possible to inspect heat detectors quickly even if the occupants are not present or the heat detectors are set in dangerous areas, unlike conventional methods. There is interest and α.

In addition, if the α-detection circuit described above has a temperature characteristic that corrects errors caused by changes in the heat-sensitive element due to the ambient temperature during inspection, inspection can be performed without being affected by the ambient temperature.
Appropriate operational tests can be performed.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of one embodiment of the present invention, Figure 2 is a circuit diagram of another embodiment, Figure 3 is a circuit diagram of a conventional constant temperature heat sensor, and Figure 4 is the sensing input of the same. FIG. 1 is a determination unit, 2 is a check circuit, Rth, Rt, Rth. Rth2 is a thermistor.

Claims (2)

[Claims] (1) A terminal is provided to connect the inspection signal line through which the inspection signal is sent, and when the inspection signal is input, a pseudo detection input similar to when a heat-sensitive element that senses the ambient temperature detects a fire is sent. A heat sensor characterized by comprising an inspection circuit that inputs input to a determination section that determines. (2) The heat sensor according to claim 1, wherein the inspection circuit has temperature characteristics that correct errors caused by changes in the heat-sensitive element due to changes in ambient temperature during inspection.