JPS6070167A - Running in trial method of shape memory alloy - Google Patents

Abstract

PURPOSE:To maintain the characteristic of a shape memory alloy for repetitive operation in a stable state by heating periodically the shape memory alloy to which specified load is acted via a spring. CONSTITUTION:Such current as indicated by (A) half-wave rectified from the 50Hz output current of an AC phase control device 8 is conducted to a shape memory alloy 3 in which a prescribed shape is memorized. The alloy 3 is therefore heated at 50Hz period by Joule heat and on the other hand the alloy is subjected to air cooling by a fan 7. The alloy 3 is thus subjected repeatedly to heating-cooling at 50Hz period like (b). Nearly specified tensile load is applied to the alloy 3 via a lower chuck 4 and a spring 5 by a weight 6 and therefore the alloy is deformed by elongation when cooled and shrinks by trying to restore the memorized shape when heated. The alloy 3 repeats consequently the deformation by elongation-the restoration of the shape at 50Hz period by the repetition of heating-cooling by which the stable operating performance is obtd.

Description

[Detailed Description of the Invention] [Technical Field] The present invention is directed to a method of deformation and shape recovery until the characteristics such as recovery stress and recovery strain reach a stable state with respect to repeated deformation-shape recovery operations.
The present invention relates to a break-in method for a shape memory alloy, in which the shape memory alloy is repeatedly subjected to deformation and shape recovery operations.

[Background of the invention]

When a shape memory alloy is used as an actuator, mechanical stability such as recovery stress and recovery strain of the shape memory alloy against repeated deformation-shape recovery operations is a particularly important issue. That is, a shape memory alloy cannot achieve stable operating performance 1q unless the deformation-shape recovery operation is repeated many times after shape memory heat treatment.

For example, Figure 1 shows the number of repeated operations and the shape memory alloy when a tensile force is applied to the shape memory alloy and the alloy is repeatedly subjected to elongation deformation due to the tensile force and shape recovery operation from the elongation deformation. shows a relationship with elongation, and a considerable increase in elongation is seen until a certain number of repetitions is reached. In addition, due to this increase in elongation, in the past, devices using shape memory alloys as actuators were unable to operate continuously, and the shape memory alloys had to be retightened frequently. .

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
It is possible to cause a shape memory alloy to repeat deformation and shape recovery operations at high speed without causing breakage, and to stabilize the properties of the shape memory alloy against repeated operations in a relatively short time. The purpose of the present invention is to provide a method for breaking-in a shape memory alloy.

[Structure of the invention]

The breaking-in method for a shape memory alloy according to the present invention includes connecting one end of a spring to the shape memory alloy to be broken in and applying a substantially constant load to the other end of the spring. The shape memory alloy is periodically heated while the load is applied to the shape memory alloy via the spring.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

FIG. 2 shows an example of a running-in method when a shape memory alloy is used in tension. An upper chuck 2 is attached to the upper part of the break-in device main body 1. The upper end of a linear shape memory alloy 3 to be run-in is removably attached to the upper chuck 2, while the lower chuck 4 is detachably attached to the lower end of the shape memory alloy 3. has been done.

A peg 6 is suspended from the lower chuck 4 via a coil spring 5.

In this example, the shape memory alloy 3 memorizes a straight shape, but the shape memory alloy 3 may memorize a curved shape.

7 is a blower, which cools the shape memory alloy 3 with air. 8 is an AC phase control device that controls the phase of the commercial power supply; one output terminal of this AC phase control device 8 is connected to the upper end of the shape memory alloy 3 via the diode 9 and the upper chuck 2; The output terminal is connected to the lower end of the shape memory alloy 3 via the lower chuck 4.

In this example, as shown in FIG. 3(a),
A current obtained by half-wave rectifying the output current of 50H2 of the AC phase control device 8 is applied to the shape memory alloy 3. Therefore, the shape memory alloy 3 is heated by Joule heat at a frequency of 50 Hz. On the other hand, the shape memory alloy 3 is air-cooled by a blower. For this reason, the shape memory alloy 3 is repeatedly heated and cooled at a frequency of 50 Hz as shown in FIG. 3(b).

And the shape memory alloy 3 is the lower chuck i'l 63
Since the spring 5 receives an almost constant tensile load from the weight 6, it stretches and deforms during cooling, but when heated, it attempts to return to its memorized shape due to the shape memory effect (i.e., it attempts to return to its memorized shape length). ) to contract.

Therefore, the shape memory alloy 3 repeats the elongation deformation and shape recovery operations at a cycle of 50H2 by repeating the heating and cooling.

Here, as shown in FIG. 1, the curve showing the relationship between the number of repeated operations and elongation of the shape memory alloy differs depending on the magnitude of the load applied to the shape memory alloy. Therefore, for example, when actually using a shape memory alloy as an actuator, even though the load value B in FIG. 1 is applied, under the load value D (B>D),
If the alloy is repeatedly operated until it reaches a stable state, 4- When the alloy is actually used as an actuator, the alloy will increase its elongation each time the deformation-recovery operation is repeated. Stable operating performance cannot be obtained.

However, in FIG. 2, if the lower end of the spring 5 is attached to the main body 1, and the load is applied to the shape memory alloy 3 only by the force of the spring 5, then the shape memory alloy 3 will be shaped by repeated operations. As the elongation of the memory alloy 3 increases, the spring 5 contracts and the force of the spring 5 becomes weak (
Therefore, the load acting on the shape memory alloy 3 decreases. Therefore, for the above-mentioned reason, stable operational performance cannot be obtained even if the deformation-shape recovery operation is repeated many times.

However, in this method, the spring 5 is attached to the shape memory alloy 3.
Since the weight of the weight 6 acts through the shape memory alloy 3, the load acting on the alloy 3 does not change even if the elongation of the shape memory alloy 3 becomes large, and the load on the shape memory alloy 3 is always almost constant. Therefore, there is no risk of the above-mentioned inconvenience occurring.

Moreover, if the spring 5 is not provided and the weight of @6 acts directly on the shape memory alloy 3, when the shape memory alloy is heated and cooled at a fast cycle as in this example, (I) ) Due to the inertia of the weight 6, both ends of the shape memory alloy 3 are substantially fixed, and the shape memory alloy 3 cannot recover its shape sufficiently. For this reason, even if heating and cooling are repeated many times, the deformation and shape recovery operations are not sufficient, and therefore stable operating characteristics against repeated operations cannot be obtained.

(b) Every time the shape memory alloy tries to recover its shape, a large load is suddenly applied to the alloy 3, which may cause the shape memory alloy 3 to break.

Such inconveniences may occur.

However, in this method, even when the shape memory alloy 3 is heated and cooled in a fast cycle, the shape memory alloy 3 can sufficiently recover its shape due to the extension of the spring 5, and the shape memory alloy 3 can sufficiently recover its shape. Since a large load is not suddenly applied to the shape memory alloy 3 due to the inertia of the &I 6 at the time of starting, the above-mentioned inconvenience does not occur.

Therefore, according to this method, the heating-cooling cycle can be made faster, and the time required for the break-in operation can be made relatively short.

FIG. 4 shows another embodiment of the invention. Horizontal main body 11
A first chuck 12 is attached to one end, and one end of a linear memory alloy 3 to be run-in is attached to the first chuck 12. Note that this shape memory alloy 3 remembers a straight shape (also in this case, there is no problem even if the shape memory alloy 3 memorizes a curved shape).

A second chuck 13 is provided at the other end of the shape memory alloy 3.
is attached removably. The upper end of the wire 14 is attached to the second chuck 13,
The upper end of a spring 16 is attached to the lower end of this wire 14 via a third chuck 15. and,
&117 is suspended from the lower end of this spring 16. Further, the intermediate portion of the wire 14 is wound around a pulley 18 rotatably supported by the main body 11, so that the shape memory alloy 3 is set in a horizontal direction.

Reference numerals 8 and 9 designate an AC phase control device and a diode, respectively, similar to those in the previous embodiment.

In this embodiment as well, the same operation as in the previous embodiment is performed. In addition, in the above embodiment, the shape memory alloy 3 is set in the vertical direction, so if the elongation of the alloy 3 becomes large, the height of the device must be made very high.
In the case of this embodiment, since the shape memory alloy 3 is set laterally, the height of the device can be reduced.

Although a weight is used in each of the embodiments described above, in the present invention, a substantially constant load may be applied to one end of the spring by other means such as magnetic force, oil pressure, or air pressure.

Further, in each of the above embodiments, a tensile load is applied to the shape memory alloy, but the present invention can also be applied to cases where a bending load, a torsional load, and a compressive load are applied to the shape memory alloy.

8- [Effects of the Invention] As described above, the breaking-in method for a shape memory alloy according to the present invention allows the shape memory alloy to repeat the deformation-shape recovery operation at high speed without causing any breakage. This provides an excellent effect of stabilizing the properties of the shape memory alloy against repeated deformation and shape recovery operations in a relatively short period of time.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the number of repeated operations and elongation of a shape memory alloy, FIG. 2 is a side view showing an example of the breaking-in method for a shape memory alloy according to the present invention, and FIG. FIG. 4 is a graph showing the waveform of the current applied to the shape memory alloy and the temperature change of the shape memory alloy in the example, and FIG. 4 is a side view showing another example of the present invention. 3... Shape memory alloy, 5... Spring, 6... Weight, 1
6... Spring, 17... Weight. Figure 1 Number of repetitions Figure 2 Figure 3 Procedural correction type February 6, 1980 Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, Display of the incident 1982 Patent Application No. 176515, Name of the invention Shape memory How to run-in alloys, and its relationship to the amendment person case Patent applicant Address: 1-6-1 Nishi-Waseda, Shinjuku-ku, Tokyo Name (
Name) Educational Corporation Bi66', Agent, Number of inventions increased by amendment None, Brief description of drawings in the specification subject to amendment, Contents of amendment 1) ``No. Figure 2” to “Figure 3”
and correct it. 2) Change the “graph” on page 10, line 15 of the specification to “waveform diagram”
and correct it.

Claims (1)

[Claims] By connecting one end of a spring to the shape memory alloy to be run-in and applying a substantially constant load to the other end of the spring, the force is applied to the shape memory alloy through the spring. A method for breaking-in a shape memory alloy, comprising periodically heating the shape memory alloy while the shape memory alloy is being acted on.