JPH0449750Y2 - - Google Patents

Description

[Detailed explanation of the idea] 〔Technical field〕 The present invention relates to a differential heat sensor.

[Background technology]

Conventionally, a differential heat sensor has been used as shown in Figure 1.
An air chamber 4 is formed by a heat-sensitive plate 1, a diaphragm 2 made of a thin metal plate of beryllium or phosphor bronze, and a diaphragm support plate 3. 5 is the diaphragm support plate 3
It is a hole drilled in the center of. Reference numeral 6 denotes a leak hole, and air that expands due to a slow temperature rise flows out of the air chamber through this leak hole, and air that expands in the air chamber 4 due to a sudden temperature rise due to a fire flows out through this leak hole 6. In this case, the pressure balance cannot be obtained, so the diaphragm 2 is displaced upward, and the contact spring 7
The contact 8 of the contact spring 9 is brought into contact with the contact 10 of the contact spring 9 to bring the terminals 11 and 12 into contact. 13 is the base. The leak hole 6 is formed by a glass cylinder 14 or a leak block such as a hole 16 of a cylindrical body 15 filled with a wire 17.

Such conventional differential heat sensor has the following drawbacks.

It is difficult to make the joint between the glass tube or leak block and the diaphragm support plate 3 airtight.
It takes time and effort.

There is a large variation in the leak characteristics of the leak holes.

There were other drawbacks.

In order to solve this problem, an example is known in which a minute leak hole is provided directly in the diaphragm. For example, Japanese Utility Model Application No. 60-34857 ``Fire Detector'' shows an example in which a minute leak hole is made in a diaphragm by direct laser beam. Also, UK patent no.
No. 735760 shows an example in which a small air leak hole is provided in the flat part of the center of the diaphragm.

However, when drilling tiny leak holes with a laser beam, the diameter and shape of the leak hole are not stable depending on the position of the hole in the diaphragm and the material of the diaphragm, so it is not suitable for mass production. There was a drawback.

[Purpose of invention]

The present invention aims to solve the above-mentioned problems, and aims to provide a differential heat sensor that is easy to assemble and has less variation in leak characteristics.

[Disclosure of invention]

Hereinafter, the present invention will be explained in detail according to examples.

In the figure, 20 is a heat sensitive plate. 21 is a diaphragm, which is a very thin metal plate made of stainless steel plate (for example, plate thickness t = 0.025 mm),
A central part 21a and a peripheral part 21b have a flat part,
A corrugated portion 21c is provided between the central portion 21a and the peripheral portion 21b.

21d is a leak hole drilled by laser processing, and has a diameter of 20 to 40 μ. 22 is a diaphragm support plate. 22a is a hole made in the center.

Then, the peripheral flat portion 21 of the diaphragm 21
b is hermetically fixed by welding or soldering to the diaphragm support plate 22, and an air chamber 23 is formed by the heat-sensitive plate 20, the diaphragm 21, and the diaphragm support plate 22.

Here, since the leak hole 21d is an extremely small hole, it is made by laser machining.
Laser machining involves focusing light and irradiating it onto the workpiece to make a hole, so when making a hole in the inclined part 21f of the wave part 21c of the diaphragm 21 as shown in Figure 6A, the laser light will be reflected to the surroundings. Therefore, the energy efficiency is poor, and the diameter of the through hole 21g is far from a perfect circle as shown in FIG. 6B. As stated by the applicant in JP-A-60-198881 "Laser Processing Method", the factors that cause variations in hole diameter include laser output energy, laser output light reflectance of the material to be processed, thermal conductivity, specific heat, and density. , boiling point, etc.

The flow rate of air is generally expressed by the following equation.

Here, Q: flow rate (mm ³ /sec) and D: pore diameter (mm).

According to the formula for flow rate, the flow rate is proportional to the square of the diameter, so if the pore diameter changes by 10%, the flow rate will vary by 36%. The need to reduce the variation in pore diameter will be understood below.

However, as shown in FIG. 7A, when the flat portion 21a is machined, a hole that is close to a perfect circle like the through hole 21h is formed.

In addition, in the case of a diaphragm as shown in FIG. 5, there is a region 21e around the center 21j where processing distortion remains strongly, and if laser processing is performed within this 21e, hardness, airtightness, strength, etc. Because of this variation, the size and shape of the machined hole will vary greatly.

32 is a base, contact springs 24, 25 are fixed to this base 32 and connected to terminals 29, 29', and contacts 26, 27 provided on the contact springs 24, 25 are arranged facing each other. . 30 is a contact interval adjustment screw. A fixing member 31 fixes the heat-sensitive block to the base 32.

In this way, when the air in the air chamber expands due to a slow temperature rise, it leaks through the leak hole 21d provided in the diaphragm 21 to the rear surface 34 of the air chamber 23.
leakage and prevent the diaphragm 21 from being displaced.

When a fire occurs, the heat generated by the fire is rapid and high, so the air in the air chamber 23 expands rapidly, and the pressure balance cannot be achieved just by leaking from the leak hole 21d, causing the diaphragm 21d to displace upward. , the contact 27 is placed above through the insulating material 28 and brought into contact with the contact 26, and the terminals 29, 29'
Short-circuit between the terminals and output a fire detection signal.

[Effect of idea]

As described above, according to the present invention, there is a bowl-shaped heat-sensitive plate 20 whose central portion bulges downward and whose upper end is open;
A hole 22a is made in the center and the peripheral part is attached to the heat sensitive plate 20.
A diaphragm support plate 22 is connected to the diaphragm support plate 22 to cover the upper end opening, and a flat peripheral part 21b of the diaphragm 21 has a flat part in the center part 21a and a peripheral part 21b and a wave part 21c in the middle part. A diaphragm 21 connected to a diaphragm support plate 22 so as to cover a hole 22a in the center of the diaphragm 21
The air chamber 23 is formed by the air chamber 23, and the air that expands due to a slow temperature rise is leaked from the leak hole 21d, and the diaphragm 21 is displaced by the air in the air chamber 23 that expands due to the temperature rise due to the fire, so that a fire can be detected. In the differential heat sensor, the leak hole 21d has a hole diameter of about 20 to 40 microns,
Since it is provided in the flat part 21a of the diaphragm 21 and in a position that avoids the center part 21e where there is processing distortion, it is easy to assemble, and there is little variation in the diameter of the extremely small hole, and the shape of the hole is also similar to the conventional one. Since the holes are made to be more perfectly circular than the holes of
A differential heat sensor with excellent quality can be obtained.

[Brief explanation of the drawing]

The drawings are drawings illustrating the invention of the present application, and are
3 and 6A to 6B show a conventional example, FIG. 1 is a sectional view, and FIGS. 2 and 3 are sectional views of a leak hole. 4 to 7 are drawings for explaining an embodiment of the present invention, in which FIG. 4 is a partial sectional view, FIG. 5 is a plan view of the diaphragm 21, and FIGS. 6A and 7B are diaphragms. 21, FIG. 6B, and FIG. 7B are partial plan views thereof. 20... Heat sensitive plate, 21... Diaphragm, 21
a, 21b... flat part of the diaphragm, 21d...
...Leak hole, 21e...Center of flat part with processing distortion, 22...Diaphragm support plate, 3...Air chamber.

Claims (1)

[Scope of utility model registration request] A bowl-shaped heat-sensitive plate with a center part bulging downward and an open top end, a diaphragm support plate with a hole in the center part and a peripheral part connected so as to cover the upper end opening of the heat-sensitive plate, and a diaphragm support plate with a hole in the center part and the peripheral part covered with the upper end opening of the heat-sensitive plate; A diaphragm is connected to the diaphragm support plate so as to cover the hole in the center of the diaphragm support plate, and the flat part of the periphery of the diaphragm has a flat part and a corrugated part in the middle of the diaphragm.The diaphragm forms an air chamber, and the temperature rises slowly. In a differential heat sensor, the air expanding at A differential heat sensor having a hole diameter on the order of microns and provided in a flat central part of a diaphragm and in a position avoiding the central part where processing distortion occurs.