JPS5864725A - Temperature protecting switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 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 for the 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 a shape memory alloy is in a high-temperature matrix state and in a low-temperature martensitic transformation state, the tensile strength value for the same amount of strain is the matrix state I/c.
It has properties that are about three times greater when it is in a state of martensitic transformation than when it is in a state of martensitic transformation. Therefore, by applying these characteristics to a temperature protection switch, a switch with reliable response and low cost can be constructed.

In view of this, the main object of the present invention is to propose a temperature protection switch that has a simple structure and operates reliably by utilizing the characteristic of shape memory alloys that cause deviation in shape due to changes in ambient temperature.

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 line t3-B in the same figure, showing a held state. Moreover, FIG. 2 shows the operating state of the example in FIG. 1,
◎1, which indicates the open state of the switch, indicates a temperature-sensitive spring, which is made of a shape memory alloy. Shape memory alloys have the property of returning to the pre-formed shape in the matrix state when the temperature rises and returns to the matrix structure. At this time, it is formed into a bent shape as shown in FIG. Therefore, when the structure of the shape memory alloy changes from martensitic transformation to the matrix phase, the temperature sensor 2
The temperature-sensitive spring 1, which had been in close contact with the temperature-sensitive spring 1, returns to its original molded shape as shown in FIG. In Figure 1 A and B,
Reference numeral 2 indicates a magnetic material, which is made of, for example, an iron piece. 3 indicates a permanent magnet, which is fixed to the temperature-sensitive spring 1 and is attached to the iron piece 2.
An attractive relationship is maintained between the two 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 continuously biased, so that the gap between the movable contact 4a and the fixed contact 4b on the temperature sensitive spring 1 side gradually opens. In general, if electrical contacts gradually open up while voltage is being applied during energization, there is a risk of arc discharge and significant damage to the electrodes.
This will damage 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 material 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 reaches the parent phase. This can produce a snap action effect.

The attractive force between the two is inversely proportional to the square of the distance, so the attractive force is extremely strong when both magnetic bodies are in close contact with each other, but once they are separated, the attractive force decreases rapidly. Therefore, it is possible to rapidly separate the two from the suction state.

Since the movable contact 4a is fixed to the permanent magnet 3 via the insulating plate 10, the fixed contact 4b changes depending on the deformation of the temperature-sensitive spring 1.
Contact and separation. The movable contact 4a is electrically connected to one terminal 7a provided on the base 12 with a lead wire 9.
connected by.

On the other hand, the fixed contact 4b is connected to the other terminal 7b provided on the base 12.
electrically connected to. Reference numeral 8 indicates a conductor for connecting the fixed contact 4b and the terminal 7b. The iron piece 2 is attached to the base 12 by screws 6, and in order to adjust the attraction force with the permanent magnet 3, the screw mounting hole of the iron piece 2 is made into a long hole or a blank hole so that it can be slid freely. It is formed. 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 configured as described above is screwed to the heat-generating portion of the temperature sensor 20, for example, an electronic device, using the mounting screw hole 11. In addition, 5
For example, a pusher is shown for returning the temperature-sensitive wire 1 which has been bent and deformed in response to the pressure.

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, and the shape is memorized in the matrix state. Even if the temperature-sensitive spring 1 reaches the state of martensitic transformation, which is lower than the temperature of the molded matrix, 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 vC of that in the parent phase, when the temperature is sensed, H1 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 It suddenly deforms against the attraction force of the contact and momentarily opens the contact.

Therefore, when the equipment reaches an abnormal temperature state, the circuit can be cut off to protect the equipment. When the different power supply is eliminated and the temperature of the temperature-sensitive spring 1 drops 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. This example is a temperature protection switch used when the temperature sensor 20 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, a temperature-sensitive switch is constituted by a temperature-sensitive spring made of a shape memory alloy and a magnetic material to which the temperature-sensitive spring is attracted and released, and the bias caused by the temperature of the temperature-sensitive spring is used. By attaching it to a temperature sensor, it is possible to cut off the circuit before the abnormal temperature rise of the temperature sensor damages the circuit inside the electronic device, providing temperature protection. There is an effect. Moreover, since the temperature-sensitive spring can be in direct contact with the temperature-sensitive body, the temperature-sensing reaction speed is fast and the temperature-sensitive spring can be miniaturized.

[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 BB in the same figure, 2 is a diagram for explaining the operation, and 3A and 3B are views of the main body FIG. 7 is a plan view and a side view showing another example of the invention. DESCRIPTION OF SYMBOLS 1... Temperature-sensitive spring, 2... Permanent magnetic pentad, 3... Permanent magnet, 4a, 4b... Contact. Agent Akiyama Senior disciple 1@A Figure 2 Figure 3 A Figure 3 β

Claims (1)

[Claims] A temperature-sensitive switch is constituted by a temperature-sensitive spring made of a shape memory alloy and a magnetic material to which the temperature-sensitive spring is attracted and released, and the contacts are opened and closed using the bias caused by the temperature of the temperature-sensitive spring. Features a temperature protection switch.