JPH09312122A - Temperature sensor and temperature switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature sensor and a temperature switch with high precision in which force generated by a spring made of shape memory alloy at a temperature rise time is utilized without reduction. SOLUTION: Working force in a reverse direction from the force of a shape memory alloy spring 4 for the setting of a temperature is generated by an attraction generation means composed of a permanent magnet 5 and an iron plate 7 being magnetic material. Since the attraction lessens rapidly when the permanent magnet 5 and the iron plate 7 are parted, the force of the shape memory alloy spring 4 is not reduced, and is effectively utilized as the operation force of a switch and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor and a temperature switch that detect an abnormal ambient temperature by using a shape memory alloy and output a signal to the outside.

[0002]

2. Description of the Related Art Shape memory alloys have the property of returning to their original shape at a certain temperature or higher, and are used as elements of temperature sensors. The temperature and spring force of the coil spring made of the shape memory alloy are shown in the thick two-dot chain line in FIG. 6 [in the figure, the characteristic of the shape memory alloy spring (fixed at the left end), the low temperature side overlaps with the thick solid line]. It has such characteristics. On the low temperature side, it has a smaller constant value, starts to increase from a certain temperature, gradually increases, and when it exceeds a certain temperature, it becomes a larger constant value again.

FIG. 5 shows a structure of a conventional temperature switch using such a shape memory alloy spring, and FIG. 6 shows a temperature characteristic diagram for explaining the characteristic thereof. The shaft 3 is movably held by the case 1 and the bearing 101 attached to the case 1. On the shaft 3, a case 1 is sandwiched, a bias spring 100 is arranged on the left side while being biased by a predetermined spring force, and a coil spring made of a shape memory alloy is formed on the right side. The alloy spring 4 is biased by a pressing plate 11 and a screw 10 to a predetermined spring force different from the above. The operating temperature is set by the spring force of the bias spring 100. On the inner shaft 3 of the bearing 101,
A push plate 102 for pushing an actuator (hereinafter abbreviated as an actuator) 81 of the switch is attached. When the temperature is low, the force of the alloy spring 4 is small, so the shaft 3 is closer to the left side. However, when the temperature rises, the force of the alloy spring 4 increases, so that the shaft 3 moves accordingly. It moves to the right, and the push plate 102 also moves to the right. When the temperature exceeds a predetermined temperature, the actuator 81 is pushed by the push plate 102 and the switch 8 operates.

This situation will be described in more detail with reference to the temperature characteristic diagram of FIG. The horizontal axis represents temperature and the vertical axis represents the force acting on the shaft 3. The characteristics of the alloy spring 4 are, as described above, as shown by the thick double-dotted chain line when fixed at the left end position.
The characteristics in the operating state are as shown by the thick line. This alloy spring 4
Is a force that attempts to move the shaft 3 to the right. On the other hand, the characteristic of the bias spring 100 is as shown by the thin double-dotted line when it is fixed at the left end position, and the characteristic in the operating state is as shown by the thin line. The force of this spring 100 is
This is the force that moves the shaft 3 to the left.

In the low temperature region, since the force of the alloy spring 4 is smaller, the push plate 102 is in a state of being pressed against the bearing 101. In this state, if the temperature rises and exceeds the point where the thick two-dot chain line and the thin two-dot chain line overlap (the maximum temperature at the left end stop position in the figure), the force of the alloy spring 4 becomes larger, so The thick line is traced so that the shaft 3 moves to the right so that the force of the spring 4 and the force of the bias spring 100 are balanced (in this state, the thick line and the thin line overlap). When the push plate 102 hits the actuator 81 and starts pushing it (in the figure, the temperature at which Sw starts pushing Ac), the pushing force is required, so the movement of the shaft 3 becomes smaller by that amount, and the alloy spring 4 and There is a difference in the force of the bias spring 100. This difference is the force pushing the actuator 81.
When the actuator 81 is pushed in by a predetermined stroke, the switch 8 operates and a signal is issued (in the figure,
Switch operating temperature). At a point where the actuator 81 is pushed in further and becomes immovable (minimum temperature at the right end stop position in the figure), the force of the bias spring 100 becomes a constant value, and the alloy spring 4 increases by its original increase amount, and a certain temperature is increased. When it exceeds, it becomes a constant value.

Therefore, although this temperature sensor shows a continuous movement of the shaft 3 with respect to temperature, the difference in force between the alloy spring 4 and the bias spring 100, that is, the operating force to the switch is indicated by another thick line in the figure. As shown, since the force of the alloy spring 4 is reduced by the amount of the force of the bias spring 100, the force is reduced and the applicable switches are limited. Further, if the stroke or force of the actuator 81 required to operate the switch 8 varies, if the temperature gradually rises, the operating temperature of the temperature switch also varies, and the detected temperature error increases.

[0007]

As described above, in the prior art, the force generated by the alloy spring due to the temperature change is greatly reduced and used, and the force for operating the switch is reduced. Further, the temperature switch has a problem that the operating temperature tends to vary.

An object of the present invention is to solve the above-mentioned problems and to use alloy springs effectively without reducing the force generated by temperature change, and to provide a highly accurate temperature sensor with a small variation in the operating temperature of the switch. It is to provide a temperature switch.

[0009]

In order to solve the above problems, in the present invention, a force for generating a force in the direction opposite to that of the alloy spring for temperature setting is generated by a permanent magnet and a magnetic material. It is generated by providing. In this way, when the magnetic material separates from the permanent magnet, its attractive force sharply decreases, so that the force of the alloy spring can be effectively utilized as it is as the operating force of the switch or the like.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is provided with a spring made of a shape memory alloy and means for generating an attractive force by a permanent magnet and a magnetic material. Is biased in the opposite direction, and is configured to operate at a temperature at which the spring force of the shape memory alloy exceeds the attractive force of the permanent magnet.

Embodiments will be described below with reference to the drawings. (Embodiment) FIG. 1 is a conceptual diagram showing a normal state of an embodiment of a temperature switch according to the present invention, FIG. 2 is a conceptual diagram showing a high temperature state above a set temperature, and FIG. 3 is a perspective view showing the appearance. FIG. 4 is a temperature characteristic diagram for explaining the operation.

In the figure, parts having the same functions as those of the prior art are designated by the same reference numerals. A coil spring (alloy spring) 4 made of a shape memory alloy is arranged at the tip of the shaft 3 that penetrates the inside of the side surface of the case 1 from the outside to the outside of the case. Further, a magnet mounting plate 6 for holding the permanent magnets 5 is arranged in a portion on the side opposite to the side surface inside the case, and the shaft 3 is movable through a hole opened in the magnet mounting plate 6. Held in. An iron plate 7 attracted to the permanent magnet 5 is fixed near the magnet mounting plate 6 of the shaft 3. This iron plate 7
Also serves as the push plate 102 in the prior art for pushing the actuator 81 of the switch 8.

The state of FIG. 1 shows a state at a normal ambient temperature, in which the force of the alloy spring 4 is small and the permanent magnet 5
The alloy spring 4 is in a contracted state because its attraction force is larger. However, when the ambient temperature rises, the alloy spring 4 is also warmed, trying to return to its original shape, and a force corresponding to that temperature is generated, and when the attraction force generated by the permanent magnet 5 and the iron plate 7 is exceeded, As shown in FIG. 2, the iron plate 7 is separated from the permanent magnet 5, and the shaft 3 moves to the right.

When the iron plate 7 pushes the actuator 81 of the switch 8 by the movement of the shaft 3, the switch 8 operates and outputs a signal to the outside. That is, it becomes a temperature switch. The above operation will be described in more detail with reference to the temperature characteristics of FIG. In the figure, the horizontal axis is the temperature, and the vertical axis is the force acting on the shaft 3. When the temperature is low, the attractive force generated by the permanent magnet 5 and the iron plate 7 (thin line in FIG. 4, the attractive force characteristic of the permanent magnet at the position in FIG. 1) is the thin line, and the thick line indicates the alloy. The force generated by the spring 4 (in the figure,
1) is maintained, so that the state of FIG. 1 is maintained.

When the temperature rises in this state, the suction force does not change, but the force of the alloy spring 4 increases,
When the switch operating temperature is reached, the two forces become the same. When this temperature is exceeded, the permanent magnet 5 and the iron plate 7 separate, and this attractive force decreases to a value close to zero, and the force of the alloy spring 4 causes the shaft 3 to move. Moves to the right side in FIG. 1 and becomes the state of FIG. The iron plate 7 also moves to the right together with the shaft 3, and the actuator 81 of the switch 8 is pushed to operate the switch 8. With this movement, the alloy spring 4 expands by that amount, so in FIG. 4, the characteristic of the shape memory alloy spring is reduced by a force corresponding to the amount of expansion at the switch temperature. When the temperature further rises, the temperature increases by a corresponding amount, and finally shows a saturation characteristic. In this case, the characteristic of the shape memory alloy spring in the temperature range exceeding the switch temperature becomes the operating force for the switch as it is.

[0016]

As is apparent from the above description, according to the present invention, the operating force applied to the switch does not become small as described in the prior art, and the set temperature of the sensor, that is, the switch operating temperature is not increased. The force of the alloy spring can be effectively used as it is, a sufficiently large operating force can be generated, and highly accurate switch characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a normal state of an embodiment of a temperature switch according to the present invention.

FIG. 2 is a conceptual diagram showing a high temperature state of an embodiment of a temperature switch according to the present invention.

FIG. 3 is a perspective view showing the appearance of an embodiment of a temperature switch according to the present invention.

FIG. 4 is a temperature characteristic diagram showing the operation of the temperature switch according to the present invention.

FIG. 5 is a conceptual diagram showing a normal state of a temperature switch according to a conventional technique.

FIG. 6 is a temperature characteristic diagram showing the operation of a conventional temperature switch.

[Explanation of symbols]

 1 Case 2 Cover 3 Shaft 4 Shape Memory Alloy Spring 5 Permanent Magnet 6 Magnet Mounting Plate 7 Iron Plate 8 Switch 81 Switch Actuator 9 Switch Mounting Plate 10 Screw 11 Holding Plate 100 Bias Spring 101 Bearing 102 Push Plate

Claims (3)

[Claims] 1. A spring made of a shape memory alloy and an attraction force generating means made of a permanent magnet and a magnetic material are provided, and the spring made of the shape memory alloy is urged in a direction opposite to the direction of the attraction force of the permanent magnet. The temperature sensor is characterized in that it operates at a temperature at which the force of the spring made of a shape memory alloy exceeds the attractive force of the permanent magnet. 2. The attraction force generating means uses a magnetic material attached to a shaft movable in the length direction and a permanent magnet fixed to a case of a temperature sensor to generate the attraction force in the length direction of the shaft. The spring made of a shape memory alloy is arranged so as to urge the shaft in a direction opposite to the direction of the force of the suction force generating means. Temperature sensor. 3. A temperature switch comprising a switch for outputting an external signal, which is driven by the operation of the temperature sensor according to claim 1.