JPH0336258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects an abnormal temperature rise occurring in an electric circuit such as an electronic device, and immediately shuts off the contact path when the temperature of the device rises above a preset temperature. The present invention relates to a temperature protection switch suitable for application to a temperature compensation device for protecting equipment, etc.

In general, shape memory alloys are formed into a predetermined shape using a high-temperature matrix, then the temperature is lowered to the martensitic transformation temperature range, the shape is deformed, and when the temperature is brought back to the matrix temperature, the shape is changed to the original shape formed by the matrix. It has the unique property of returning to its original shape. Therefore, the temperature at which the shape memory alloy transitions from martensitic transformation to the parent phase can be used to open and close the contacts of the temperature protection switch. That is, by using a temperature-sensitive spring made of a shape memory alloy as a movable contact of the temperature switch, the switch opening/closing temperature can be made to match the transformation temperature of the shape memory alloy.

In addition, when shape memory alloys are in a high-temperature matrix state and in a low-temperature martensitic transformation state, the tensile strength for the same amount of strain is higher than that in the matrix state. When it is in the state, it has the property of being about three times smaller. Therefore, if these characteristics are applied to a temperature protection switch, a switch with reliable response and low cost can be constructed.

However, in reality, instantaneous contact opening cannot be expected based solely on the properties of the temperature-sensitive spring.

In view of these points, the present invention utilizes the property of a shape memory alloy to cause a deviation in shape due to a change in ambient temperature, and has a simple structure that allows instantaneous contact opening by using magnetic attraction force in combination. The main purpose is to propose a temperature protection switch that operates reliably.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIGS. 1A and 1B are a plan view showing an example of a temperature protection switch, and a sectional view taken along the line B-B in the figures;
Indicates holding state. Further, FIG. 2 shows the operating state of the example shown in FIG. 1, and shows the switch in an open state. 1 indicates a temperature-sensitive spring, which is made of a shape memory alloy. Shape memory alloys have the property of returning to the preformed shape in the matrix state when the temperature rises and returns to the matrix state. , as shown in FIG. 2, is formed into a bent shape. Therefore, when the structure of the shape memory alloy changes from martensitic transformation to the parent phase, the temperature sensitive spring 1 which was in close contact with the temperature sensitive body 20 returns to its original molded shape as shown in FIG. In FIGS. 1A and B, 2 indicates a magnetic material,
For example, it is made of a piece of iron. Reference numeral 3 denotes a permanent magnet, which is fixed to the temperature-sensitive spring 1 and maintains an attractive relationship with the iron piece 2 during martensitic transformation. Note that the relationship between the magnetic body 2 and the permanent magnet 3 is a relative one, and a permanent magnet may be fixed to the temperature-sensitive spring 1 to maintain an attractive relationship with the iron piece. When the temperature-sensitive spring 1 changes to a parent phase as the temperature rises due to martensitic transformation, the structure changes continuously with respect to temperature changes. Therefore, as the temperature rises, the temperature sensitive spring 1 is biased continuously, and the gap between the movable contact 4a and the fixed contact 4b on the temperature sensitive spring 1 side gradually opens. In general, when electrical contacts gradually open up while voltage is being applied during energization, there is a risk of arc discharge, which can significantly damage the electrodes and shorten the life of the contacts. Therefore, in this example, in order to immediately open the gap between the contacts when the contacts are opened, the magnetic body 2 and the permanent magnet 3 realize a snap action action. In shape memory alloys, there is a difference in tensile strength for the same amount of strain between the martensitic transformation and the matrix state, and the tensile strength in the matrix state is about three times that of the martensitic state. Therefore, in the martensitic state, the attractive force between the magnetic body 2 and the permanent magnet 3 should be set to be smaller than the force required to return to its original shape when the temperature of the temperature-sensitive spring 1 rises and becomes the matrix phase. This can produce a snap action action. Since the attraction force between the two is inversely proportional to the square of the distance, the attraction force is extremely strong when both magnetic bodies are in close contact with each other, but once they are separated, the attraction force decreases rapidly. Therefore, it is possible to rapidly separate the two from the suction state.

The movable contact 4a is connected to the permanent magnet 3 via the insulating plate 10.
Since it is fixed to , it comes into contact with and separates from the fixed contact 4b according to the deformation of the temperature-sensitive spring 1. The movable contact 4a is connected to one terminal 7a provided on the base 12 by a lead wire 9 for electrical connection. On the other hand, the fixed contact 4b is electrically connected to the other terminal 7b provided on the base 12. 8 indicates a conductor for connecting the fixed contact 4b and the terminal 7b.
The iron piece 2 is attached to the base 12 with screws 6, and in order to adjust the attraction force with the permanent magnet 3, the screw attachment hole of the iron piece 2 is formed as a long hole or a hole so that it can be slidably attached. . The suction force is greatest when the iron piece 2 is closest to the temperature-sensitive spring 1 (see FIG. 1B). The temperature protection switch having the above structure is screwed to the heat-generating portion of the temperature sensing element 20, for example, an electronic device, using the mounting screw hole 11. Incidentally, reference numeral 5 indicates a pusher for returning the temperature-sensitive spring 1 which has been bent and deformed in response to the temperature-sensitive spring 1 to its original state.

Next, the operation of the switch of the present invention will be explained.
The temperature-sensitive spring 1 made of a shape memory alloy is preformed into a shape as shown in FIG. 2 at the temperature of the matrix state, so that the shape in the matrix state is memorized. Even when the temperature-sensitive spring 1 reaches the state of martensitic transformation, which is lower than the temperature of the matrix in which it was molded, it retains its shape when molded in the matrix unless external force is applied. Since the force required to deform the spring 1 is about 1/3 of that in the parent phase, the temperature-sensitive spring 1 is easily deformed by pressing the pusher 5 and returns to the shape shown in FIG. 1B. The magnetic body 2 and the permanent magnet 3 are brought into close contact with the temperature sensing body 20 by the attraction force between them.

By connecting an electric circuit to the terminals 7a and 7b, the circuit can be opened by operating the temperature sensitive spring 1. That is, as shown in FIG. 1, when the contacts 4a and 4b are in the closed state, when the temperature of the temperature-sensitive spring 1 approaches the matrix transformation temperature due to abnormal temperature rise, the temperature-sensitive spring 1 is permanently connected to the magnetic body 2. It deforms rapidly against the attraction force with the magnet 3, and momentarily opens the contact points. Therefore, if the equipment becomes abnormally hot, the circuit can be cut off to protect the equipment. When the abnormal temperature is eliminated and the temperature of the temperature-sensitive spring 1 is also lowered to undergo martensitic transformation, the pusher 5 can be pressed again to maintain the attracted state between the magnetic body 2 and the permanent magnet 3.

3A and 3B are a front view and a side view of another example of the present invention in a holding state. In this example, the temperature sensor 20
This is a temperature protection switch used when is made of iron and isomagnetic material. Therefore, the permanent magnet 3 fixed to the temperature sensitive spring 1 is directly attracted to the temperature sensitive body 20 without using the magnetic body 2 in the example shown in FIG. 1, and the temperature sensitive spring 1 is in direct contact with the temperature sensitive body 20. Other configurations and operations are substantially the same as those in the example shown in FIG. 1, so detailed explanations will be omitted.

As described above, according to the present invention, there is a temperature-sensitive spring made of a shape memory alloy in contact with a temperature-sensitive element, and a magnet or a magnetic material is provided on the temperature-sensitive spring to serve as a movable contact side, so that when the temperature-sensitive spring undergoes martensitic transformation, The above magnet or magnetic body and the fixed magnetic body or magnet were configured to be attracted to each other, and the magnetic attraction force was set to be smaller than the displacement force during matrix transformation of the temperature-sensitive spring, so the temperature-sensitive spring was set to open. The contacts can be opened instantaneously when the temperature is reached. Therefore, by attaching it to the temperature sensor, the circuit can be cut off before the circuit inside the electronic device is damaged due to an abnormal temperature rise of the temperature sensor, thereby providing a temperature protection effect.
Moreover, since the temperature-sensitive spring can come into direct contact with the temperature-sensitive body,
The temperature-sensitive reaction speed is fast and it can also contribute to miniaturization of the temperature-sensitive spring.

[Brief explanation of the drawing]

1A and 1B are a plan view of an example of the present invention in a held state and a sectional view taken along the line B-B in the same figure, 2A and 2B are views for explaining the operation, and 3A and 3B are the main views of the present invention. FIG. 7 is a plan view and a side view showing another example of the invention. 1... Temperature-sensitive spring, 2... Magnetic material, 3... Permanent magnet, 4a, 4b... Contact.

Claims (1)

[Scope of Claims] 1 A magnetic body or a magnet and a fixed contact are provided on a base to form a fixed side, and a magnet or a magnetic substance and a movable contact are provided on a temperature-sensitive spring made of a shape memory alloy in contact with a temperature-sensitive body to form a movable contact. side, so that the magnet or magnetic body on the movable side and the magnetic body or magnet on the fixed side are attracted when the temperature-sensitive spring undergoes martensitic transformation, and the attraction force of the magnet is equal to the displacement force during the matrix transformation of the temperature-sensitive spring. A temperature protection switch characterized by a lower temperature setting.