JPS5816072Y2 - differential fire detector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a differential fire detector using a thermistor.

Differential fire detectors use a thermistor with a small thermal time constant (
A thermistor with a large thermal time constant (hereinafter referred to as a reverse element thermistor) is connected in series, and the potential change at the connection point of the forward-reverse thermistor occurs when the forward element thermistor is rapidly heated due to a fire. It was designed to detect a temperature rise rate above a predetermined value and notify a fire.

In order to make the thermal time constants of the thermistors different, as shown in FIG. It is attached to the case 2 with an air layer on the back side, so that when there is a sudden temperature rise such as in a fire, the forward element thermistor 1 follows through the heat sensitive plate 3 and is heated, and the reverse element thermistor 4 is connected to the case 2 through the air layer. It was made to heat slowly through the medium.

However, even in the above sensor, the heat-sensitive plate 3 is connected to the cover 2.
Since it is directly attached to the heat sensitive plate 3, the cover 2
There was a lot of heat escaping to the front element, and the forward element thermistor 1 was heated up with a delay, making it impossible to obtain a high-output sensor.

In addition, since the reverse element thermistor 4 is attached to the cover 2 which has a large heat capacity, when it receives heat with a slow temperature rise, the temperature increase rate of the forward element thermistor 1 and the reverse element thermistor 4 will be the same. , there was also the risk of false alarms occurring.

In consideration of the above points, this invention was designed to achieve high output with less false alarms, where forward element thermistors tend to follow the ambient temperature and heat up rapidly, and when the temperature rises slowly, forward and reverse thermistors tend to have the same temperature rise rate. This provides a mobile fire detector.

An embodiment of the differential fire detector of this invention will be described below with reference to the drawings.

The forward element thermistor 1 is attached to the center of the back of the heat sensitive plate 3, and the forward element thermistor 1 is covered with a cylindrical holder 5 in which the reverse element thermistor 4 is embedded in the inner bottom surface.
This holder 5 is attached to a sensor main body 7 in which a switching circuit and the like are housed via a plurality of or ring-shaped legs 6 provided on the outer bottom surface of the holder 5.

The thermistors 1 and 4 are connected before the heat-sensitive plate 3 is watertightly attached to the holder 5, and the shield wire 8 is connected to the lead-out hole 9.
It is drawn out more.

The heat sensitive plate 3 of this sensor is a small holder 5 with a small heat capacity.
, and this holder 5 is attached via legs 6 to the sensor main body 7 having a large heat capacity.
The heat received by the heat sensitive plate 3 rapidly heats up the thermistor 1 without escaping to the holder 5 and main body 7.

On the other hand, the heat received by the holder 5 is small, but the air inside acts as a thermal insulator, so the apparent heat capacity increases, and the reverse element thermistor 4 is gradually heated, and the reverse element thermistor 4 is gradually heated. The potential at the connection point between the thermistors 1 and 4 changes rapidly and greatly.

In addition, in the case of a slow temperature rise, the holder 5 and the sensor body 7
Since an air layer that acts as a thermal insulator is formed between the legs 6 and the holder 5, less heat escapes from the holder 5 to the main body 7, and the forward element thermistor 1 and the reverse element thermistor 4 are the same at an early point in time. The rate of temperature rise becomes the forward/reverse thermistor 1, 4.
No potential change occurs.

Since this invention is constructed and operates as described above, it is effective in providing a differential fire detector with high output and few false alarms.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional differential fire detector, and FIG. 2 is a cross-sectional view of one embodiment of the differential fire detector of this invention. 1...Forward element thermistor, 3...Heat-sensitive plate, 4...Reverse element thermistor, 5...
Holder, 6...legs, 7...sensor body.

Claims (1)

[Scope of utility model registration request] 1. A forward element thermistor 1 is attached to the central part of the back surface of the heat sensitive plate 3, and this forward element thermistor 1 is covered with a holder 5 having an inverse element thermistor 4 on its inner bottom surface, and this holder 5 is provided on its outer bottom surface. A differential fire detector that is attached to a detector body 7 via legs 6. 2. The holder 5 is formed in a cylindrical shape and has a plurality of legs 6. The differential type according to claim 1 of the patent registration claim 3. The holder 5 is formed in a cylindrical shape and has ring-shaped legs 6. A differential fire detector according to claim 1 of the utility model registration claim, comprising: