JPH0246793B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a crank rocking device using a shape memory alloy coil spring and a bias coil spring. The rotation angle is increased.

[Conventional technology]

Shape memory alloys have a shape memory effect that memorizes a certain shape at a temperature above the martensitic transformation point, deforms it at a temperature below the transformation point, and then recovers the memorized shape after the transformation point when heated. It exhibits unique characteristics called Ni-Ti, Cu-
Alloys such as Zn-Al and Au-Cd are known. The phenomenon called shape memory effect is usually irreversible; when an alloy is deformed at a low temperature and then heated, it returns to its memorized shape, but even if it is cooled again to a low temperature, it does not return to the shape it deformed at a low temperature. .

In order to utilize this industrially, it is necessary to perform a reversible operation that can be repeated, and various methods have been proposed. Among these methods, the method using bias force is widely used because it has the advantage of having a large degree of freedom in design and requiring only a small number of shape memory alloy materials.

In the bias force method, when the shape memory alloy is at low temperature,
In other words, it takes advantage of the characteristics that it is soft and has a low falling stress at temperatures below the temperature at which it recovers its shape by heating (called the Af point), and becomes hard and has a high falling stress at temperatures above the Af point. For example, as shown in Fig. 1, a shape memory alloy coil spring 1 (hereinafter abbreviated as F spring) and a bias coil spring 2 (hereinafter abbreviated as B spring) are appropriately stretched and deformed, and the rod 3 is pulled together. A device that does this is known. In this device, since the shape memory alloy is soft at temperatures below the Af point, the F spring 1 is stretched by the B spring 2, and the rod 3 is located on the B spring 2 side. F spring 1
When the F spring 1 is heated to a temperature above the Af point by heating with infrared rays or electricity, the F spring 1 recovers its shape and becomes hard and strong, so the rod 3 is pulled by the F spring 1 and moves toward the F spring 1 side. do. When the temperature of F spring 1 falls below the Af point again, F spring 1
becomes soft, and the rod 3 is pulled by the B spring 2 and moves toward the B spring 2 side. Therefore, the rod 3 is used in various actuators by reciprocating a certain amount by deforming the shape of the F spring 1 due to temperature changes.

However, in such a structure, when the F spring contracts due to shape recovery from the stretched state, the shape recovery force gradually decreases as the F spring contracts, while the spring force of the B spring decreases as it is stretched. Increase gradually. Therefore, the generated force, which is the difference in force between the two springs, rapidly decreases as the amount of operation (stroke) increases. In order to increase the amount of differential movement and generated force, it is necessary to reduce the shape recovery force of the F spring and the stroke dependence of the B spring force.To do this, both springs must be made longer and the size and cost of the device will be reduced. There was a problem with this point.

To solve this problem, a crank mechanism is used to
It is known that the spring has an apparently negative spring characteristic so that the spring force of the B spring does not increase but decreases when the F spring contracts due to shape recovery. As disclosed in Japanese Patent No. 49-7683, the moment produced by spring B is always made to have negative position dependence. Here, negative position dependence refers to the property that the moment decreases when the crank angle θ increases.

[Problem to be solved by the invention]

Moment is the product of distance and force, so when the change in distance has a large negative dependence compared to the change in force, the moment as a whole can have a negative position dependence, and shape memory It is possible to compensate for the positive position dependence of the shape recovery force of the alloy. However, as shown in FIG.
As shown by A in Figure 2, it was extremely narrow, making it impossible to take a large stroke. Positive position dependence means that the moment increases as the crank angle θ increases. For example, in the range indicated by A in Figure 2B, the angle θ is
As the moment increases slightly from 150 degrees, it decreases, so it has a negative position dependence. On the contrary
It is said that there is a positive position dependence between 90 and 120 degrees.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has been developed by improving the crank mechanism to reduce the position dependence of the moment provided by the B spring in a position range where the moment provided by the F spring has a positive dependence on position. By making the positional dependence of the moment of the B spring positive in the positional range where the moment of the F spring has a negative positional dependence, we have created a crank rocking device that can obtain a large generated force over a wide positional range. It was developed.

That is, in the rocking device of the present invention, the rocking side of a crank whose one end is pivotably pivoted to a base material is connected to the base material by attaching a shape memory alloy coil spring (F spring) to one side of the rocking direction. , in a device in which a bias coil spring (B spring) is attached to the other side of the swing direction and connected to the base material, and the crank is caused to swing by deforming the shape of the F spring due to temperature changes, the crank pivot point and the F spring are Both connection points are provided at positions where the angle on the side opposite to the crank formed by the straight line connecting the connection points and the straight line connecting the crank pivot point and the connection point of the B spring is 115 to 160 degrees. It is.

This will be explained in detail using the drawings.

FIG. 3 is a principle diagram showing an example of the device of the present invention. In the figure, 1 is an F spring, 2 is a B spring, 4 is a crank, 5a, 5b, and 5c are base materials,
has one end 4a pivotably attached to the base material 5a,
An F spring 1 is attached to one side of the swinging side tip 4b in the swinging direction.
is attached and connected to the base material 5b, the B spring 2 is attached to the other side in the swing direction and connected to the base material 5c, and the swing side tip 4d of the crank 4 is pulled together by the F spring 1 and the B spring 2. to hold. In such a state, when the temperature of F spring 1 is below the Af point,
Since the force of the F spring 1 is weak, it is defeated by the force of the B spring 2, and the tip 4b of the swinging side of the crank 4 is positioned at B, which is closer to the B spring 2 side, as shown in the figure. When the temperature of the F spring 1 becomes higher than the heated point Af, the F spring 1 becomes stronger, pulls the B spring 2, and moves the swinging end 4b of the crank 4 to the position C shown in the figure. F spring 1
The tip 4b of the swinging side of the crank 4 whose temperature drops below point A returns to position B again. Although heating of the F spring 1 is not shown, it may be heated by a known means such as energization or infrared irradiation.

In such a device, the pivot point D of the crank 4
The position where the angle φ formed on the opposite side of the crank 4 between the straight line DE connecting the connecting point E of the F spring 1 and the straight line DF connecting the pivot point D and the connecting point F of the B spring 2 is 115 to 160 degrees. At the pivot point D and the connection point E between both springs 1 and 2,
F is set.

[Effect]

By setting the pivot point D and both connection points E and F at such positions, when the F spring 1 is heated above the Af point and recovers its shape, the moment generated will be equal to the swing angle of the crank 4. When increasing with respect to changes in , that is, in the range where there is a positive dependence,
Conversely, the moment due to B spring 2 has a negative dependence on the swing angle, and as the swing angle becomes large [F spring 1 contracts], the moment of F spring 1 becomes negative with respect to the swing angle. In the range where the change occurs, the moment caused by the B spring 2 has a positive dependence. In other words, when the balance between two springs determines the position, if the increase in tensile force due to contraction of one spring and expansion of the other spring is small, the spring will settle at a position with a larger displacement.

By having the above-described configuration, the device of the present invention has a range A in which the moment of the conventional spring B shown in FIG. 2 has a negative dependence on the rocking angle of the crank.
In addition, it is possible to have an effective operating range even in a range having positive dependence, and the swing stroke of the crank and/or the rotation angle of the crankshaft are increased to more than twice that of the conventional one. In other words, the connection points of the present application are provided at positions where the angle on the opposite side of the crank formed by the straight line connecting the crank pivot point and the connection point of the shape memory alloy coil spring is 115 to 160 degrees, as shown in FIG. This was done based on the curve shown in (b). The curve is almost symmetrical with its peak at an angle of 135 degrees. This limitation is the variable angle θ
This is the point at which the decrease becomes significant. Although there is no clear sudden critical change, it is clearly changing. When a natural phenomenon is used, there is not necessarily a sudden change, so in such a case, it is determined at an appropriately effective value depending on industrial usefulness.

〔Example〕

Made of shape memory alloy made by forming a Ni-Ti shape memory alloy wire with a diameter of 0.75 mm into a tightly wound coil spring with a center diameter of 5.0 mm and an effective number of turns of 20, which is then fixed and heat treated at a temperature of 450°C for 30 minutes. Coil spring (F spring) and
Using a stainless steel bias coil spring (B spring) with a spring constant of 0.003 kgf/mm and a crank with a length of 15 mm, one end of the crank 4 is attached to the base material 5a so that it can swing freely as shown in Fig. 4A. Pivotally connected, crank 4
A crank rocking device was constructed in which an F spring 1 was attached to one side of the rocking direction and continued to the base material 5b, and a B spring 2 was attached to the other side of the rocking direction and continued to the base material 5c. . Regarding this, crank pivot points D and F
By changing the angle φ formed on the opposite side of the crank 4 between the straight line DE that connects the connection point E of spring 1 and the straight line DF that connects the pivot point D and the connection point F of B spring 1, the pivot point D and both connections are made. Points E and F were set, the F spring 1 was energized and heated, and the variable angle θ between B and C of the reversibly operable crank based on the shape memory effect was measured. The results are shown in Figure 4B.

As can be seen from Figure 4B, when the angle φ between the pivot point and both connecting points is 105 to 170 degrees, a variable angle θ that is more than twice that of the conventional method is obtained, and particularly good results are obtained within the range of 115 to 160 degrees. is obtained. That is, by keeping φ between 115 and 160 degrees, even if the length of the crank and the distance between the pivot point of the crank and the connecting point of both springs are changed, the initial tension of spring B can be kept within the practical limit (zero). to 10 times the spring constant), the above characteristics do not change much, and good operating characteristics can be obtained. In addition, since the angle φ in the present invention is geometrically determined by dimensions and positional relationships, the characteristics of the shape memory alloy other than the heat treatment method of the shape memory alloy,
For example, the transformation temperature and the like are omitted because they are essentially unrelated to the data shown in FIG. 4B.

〔Effect of the invention〕

In this way, according to the present invention, there is no need for any special parts, and by simply setting the positions of the pivot point of the crank and the connection point of both springs in a specific relationship, the angle θ can be adjusted.
In other words, it can dramatically increase the swing stroke of the crank and/or the rotation angle of the crankshaft, and can be applied to various actuators, temperature sensors, sensor/actuator elements such as safety devices, etc.
This has a remarkable effect.

[Brief explanation of drawings]

Figure 1 is a principle diagram showing an example of a conventional rod rocking device, and Figures 2 (a) and (b) show the angular dependence of the moment generated by spring B of a conventional crank rocking device. Schematic diagram, B is an explanatory diagram showing the angular dependence of moment, FIG. 3 is a principle diagram showing an example of the device of the present invention, and FIG. 4 A and B are diagrams showing the characteristics of the device of the present invention. FIG. 1 is a schematic diagram of the device; FIG. 1...F spring, 2...B spring, 3...rod,
4... Crank, 5a, 5b, 5b... Base material.

Claims (1)

[Claims] 1 The swinging side of the crank, whose one end is pivotably pivoted to the base material, is connected to the base material by attaching a shape memory alloy coil spring to one end in the swinging direction, and a bias coil is attached to the other end in the swinging direction. In a device in which a spring is attached and connected to a base material, and the crank is oscillated by deforming the shape due to temperature changes of the shape memory alloy coil spring, a straight line connecting the crank pivot point and the connection point of the shape memory alloy coil spring; A crank rocking device characterized in that both connection points are provided at positions where the angle on the opposite side of the crank formed by the straight line connecting the crank pivot point and the connection point of the bias coil spring is 115 to 160 degrees.