JPH01308954A - Gas leak alarm - Google Patents

Abstract

PURPOSE:To enable the emitting of an accurate gas leak alarm simply by providing a gas detector and a temperature switch. CONSTITUTION:A gas detector 2 is connected to a DC power source 6 to be kept at a fixed temperature below a transformation point of a shape memory alloy used for a temperature switch 10. As the temperature of the element 2 is normally kept below the transformation point of the shape memory alloy, a gas contacts the perimeter of the element 2 while a switching contact 10c of the switch 10 is closed to the position of a contact 10b to be switched (b) and as the gas is burned, the temperature of the element 2 rises to heat the switching contact 10c of the switch 10 provided near the element 2. Then, when the temperature of the element exceeds the transformation point of the alloy, the contact 10c gets in contact with the position of a contact 10a to be switched (a). Thus, when the contact 10c is closed to the position of the contact 10a to be switched, an alarm is actuated to issue an alarm about an existing gas leak.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a catalytic combustion type gas leak alarm using a shape memory alloy.

[Conventional technology]

2. Description of the Related Art A conventional gas leak alarm for combustible gas is known that detects a change in resistance of a detection element that occurs when a gas to be detected comes into contact with a gas detection element and combusts. An example of such a gas leak alarm is shown in FIG. Here, the bridge circuit 1 includes a gas detection element 2. It is composed of a degree compensation element 3, two resistors 4 and 5, and a DC power supply 6 is connected between two opposing terminals on one side, and a level judgment circuit is connected between two opposing terminals on the other side via a voltage amplifying circuit 7. 8 are connected. The level determination circuit 8 includes an output switch 9, and the output switch 9 is connected to an alarm circuit (not shown).

Although the power supply voltage is always applied to the bridge circuit 1, the detection element 2. The resistance of the temperature compensation element 3 is the same as that of the other two resistances 4,
5, its output voltage is low. However, when gas comes into contact with the surroundings of the gas detection element 2 and this gas is combusted, the temperature of the gas detection element 2 increases and its resistance changes. Therefore, the balance of the bridge circuit 1 is broken, and a voltage is generated at its output terminal. This voltage is amplified by a voltage amplifier 7 and transmitted to a level determination circuit 8. Level determination circuit 8 closes output switch 9 when its input exceeds a predetermined value. Then, an alarm is issued from the alarm circuit.

[Problem to be solved by the invention]

By the way, in this gas leak alarm, even if the gas concentration rises to a detection level, the temperature increase given to the gas detection element is low, and the resistance change of the gas detection element is small. For this reason, a bridge circuit is formed to increase sensitivity and compensate for temperature.
Furthermore, a voltage amplification circuit must be provided for amplification, and a bridge circuit sensitivity adjustment device and a level determination circuit are also provided, making the entire circuit complicated.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate the above-mentioned drawbacks and to provide a simple and reliable gas leak alarm.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention is equipped with a gas detection element whose temperature increases due to the combustion of the gas it comes into contact with, and a temperature switch made of a shape memory alloy that is heated by the gas detection element. It is.

[Effect]

In the gas leak alarm according to the present invention, the shape memory alloy is soft and easily deformed in the martensitic phase, and after being plastically deformed by applying a deforming force, it transforms into the austenitic phase.When heated, it hardens and retains its original shape. Focusing on the fact that it has the property of returning,
A temperature switch is constructed from this shape memory alloy, and the temperature switch, which is always below the transformation point, is heated to above the transformation point by a gas detection element that detects a gas leak, and the temperature switch is opened or closed to operate an alarm device.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1, 2, and 3. In FIG. 1, a gas detection element 2 is connected to a DC power source 6 and maintained at a constant temperature below the transformation point of a shape memory alloy used in a temperature switch described below. A temperature switch 10 is provided near the gas detection element 2 so as to be heated by the element 2. This temperature switch 10 has a switching contact 10a, a switching contact 10b, and a switching contact 10c made of a shape memory alloy that is normally curved and in contact with the switching contact 11b.
An alarm device (not shown) is connected between the switched ai point 10a and the switching contact 10c.

Since the temperature of the detection element 2 is always maintained below the transformation point of the shape memory alloy, the switching contact 10c of the temperature switch 10 is closed to the switching contact 10b, but the gas around the detection element 2 does not come into contact with it. However, when this gas burns, the temperature of the element 2 rises, and the switching contact 10c of the temperature switch 10 provided near this element 2 is heated, and when this temperature exceeds the transformation point of this alloy, the switching contact 10c It returns to the conventional shape and contacts the switched a contact 10a side. When the switching contact 10c closes to the switched contact 10a side, an alarm is activated to warn that there is a gas leak.

Since the temperature of the gas detection element rises in accordance with the concentration of the combusted gas, the temperature switch can be operated at the required gas concentration by appropriately adjusting the constant temperature and the transformation point of the shape memory alloy.

Figures 2 and 3 are a wiring diagram and a perspective view of the sensor showing an embodiment of the gas leak alarm different from Figure 1, in which the gas detection element 2 is connected to the power source 6 and the shape of the constant temperature switch is The point maintained at a constant temperature below the transformation point is the first
It is similar to the figure. Also, the temperature switch 10 provided in the vicinity of the detection element 2 is composed of a switched A contact 10a, a switched contact 10b, and a switching contact 10c made of a shape memory alloy, as in FIG. However, this embodiment differs from FIG. 1 in that the switching contact 10c is pulled by a spring 11 toward the contact 10b to be switched.

Of course, an alarm (not shown) is connected between the switched A contact 10a and the switching contact 10c.

In this gas alarm, when the gas detection element 2 is always at a low temperature, the temperature of the temperature switch is below the transformation point, and the switching contact 10C is in the martensitic phase, the switching contact 11c is soft and is pulled by the spring 11 to the B contact 10b side. are in contact. When gas comes into contact with the area around the detection element 2 and this gas burns, the detection element 2
temperature rises, and the switching contact 10c is heated. When this temperature exceeds the transformation temperature of this alloy, the switching contact 10c transforms into an austenite phase and hardens, and returns to its original state against the spring 11 to become the A contact 10a. Touch it to activate the alarm. Also, when the gas dissipates and the temperature of the detection element 2 decreases, the switching contact 1
Since 0c also returns to the martensitic phase and becomes soft, the switching contact 10c is pulled by the spring 11, moves away from the a contact 10a, and comes into contact with the b contact 10b. The alarm is therefore released. Thus, in this embodiment, the gas leak alarm is of the automatic reset type. In addition, at 8 in FIG. 3, 21 is an electrode for a power source, 22 is a switch electric wire, etc., and 23 is a sensor base.

〔Effect of the invention〕

As described above, according to the present invention, the temperature change of the gas detection element can be transmitted to a temperature switch made of a shape memory alloy, and the temperature switch can be output as an open or close output to operate an alarm. , it is possible to provide a gas leak alarm having a simple configuration with a small number of parts.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram showing an embodiment of the gas leak alarm according to the present invention, Fig. 2 is a wiring diagram showing a different embodiment of the invention, Fig. 3 is a perspective view of the sensor section, and Fig. 4 is a conventional It is a block diagram showing an example of a gas leak alarm. 2: Gas detection element, 10: Temperature switch.

Claims (1)

[Claims] 1) A gas leak alarm comprising a gas detection element whose temperature rises due to combustion of the gas it comes into contact with, and a temperature switch made of a shape memory alloy that is heated by the gas detection element.