JPH042795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in actuators using shape memory alloys.

(Prior art and its problems) Various actuators using shape memory effects such as Ni-Ti alloys are known. In many of these, shape memory alloys having unidirectional properties are used because if the shape memory alloy itself has two-way properties, it is not possible to accurately set the shapes on the high and low temperature sides. Methods for obtaining bidirectional characteristics using a unidirectional shape memory alloy include a bias method and a differential bidirectional element. These methods utilize the properties of being soft at low temperatures and hard at high temperatures, such as the bias method shown in FIG. 3.

That is, the shape memory alloy coil 5 and the coil spring 6
are arranged in parallel to the central axis 8 via the stopper 7.When the temperature is low, the shape memory coil is in a contracted shape due to the bias force of the coil spring, but when the shape memory coil is heated to a high temperature. Then, the shape memory coil expands by overcoming the bias force of the coil spring, pushing the stopper to the right in the drawing, and the central axis moves to the right. When the heating is stopped and the temperature becomes low, the bias force of the coil spring becomes stronger, pushing the shape memory coil back to the stopper and moving the central axis to the left. By repeating such operations, driving forces in two directions are applied to the central shaft. In addition, in the differential type, a shape memory coil is used instead of the coil spring 6 shown in Fig. 3, and the two left and right shape memory coils are alternately heated to obtain driving force in two directions in the same way as above. .

However, both the bias type and the differential type use the property of returning to the memorized shape when heated, so they return to the original position when the temperature becomes low. When maintaining the moved position, it is necessary to maintain that temperature for the period necessary to maintain shape memory. That is, in the bias type shown in FIG. 3, if the stopper is moved to the right and the temperature is to be maintained for a certain period of time, it is necessary to maintain the shape memory coil at a certain temperature for a certain period of time. Normally, methods for heating shape memory coils include heating the coil by directly applying electricity to the coil, heating with hot air, etc. However, current control devices, adjustment devices such as timers, and hot air heating devices are required. However, the cost is high, and there are also restrictions on the installation location, which pose major obstacles to the use of this type of drive device.

The inventor studied the above problems, made this improvement, and released it as an "actuator" in January 1986.
A patent application was filed on the 31st. As shown in Fig. 2, this invention allows a rectangular plate of shape memory alloy to memorize the shape of a rectangular shape as shown in Fig. 2 a, and then inverts this into a shape symmetrical to the memorized shape as shown in Fig. 2 b. The shape memory alloy plates are inserted into the shaft 4 through the stopper 3 in parallel with the shape memory alloy plate 2, and the upper and lower ends of the shape memory alloy plates are fixed. can be heated alternately. When the shape memory alloy plate 1 is heated to a predetermined temperature when it is stable at low temperatures in this state, the shape memory alloy plate 1 returns to its original memorized shape as shown in FIG. 2c. At this time, the shape memory alloy plate 2 also jumps from the memory shape of b to buckle and reverse as shown in c, and even if the shaft 4 is driven to the right and stops heating and is cooled, it remains stable in this state. Next, when the shape memory alloy plate 2 is heated in this state, Fig. 1b
As shown in the figure, the shape memory alloy plate 2 returns to its original memorized shape, the shape memory alloy plate 1 also jumps, buckles, and turns over, and the shaft 4 is driven to the left and remains stably stationary in this state. By repeating the above operations, it becomes possible to provide intermittent or continuous drive in two directions to the shaft.

That is, since at least one of the shape memory alloy plates is inverted from its memorized shape and combined, it jumps and inverts during operation and becomes a buckled state, so that a stable stationary state can be maintained even during cooling.

(Problems to be Solved by the Invention) Although the above invention has achieved the intended purpose, when returning from the inverted state of 1 in Figure 2b to the memorized shape of 1 in Figure 2c, the shape When the memory alloy plate passes through the neutral plane shown by the two-dot chain line, it needs to pass through with some displacement due to the circumferential length. This displacement is difficult to predict due to variations in plate thickness, etc., and may be accompanied by large local strains, which may shorten the repeated life of the shape memory alloy. The present invention was developed as a result of considering the above problems.
We have developed a long-life actuator made of shape memory alloy that does not cause distortion during operation.

(Means and effects for solving the problem) A plurality of shape memory alloy plates are memorized into a shape having an arcuate or conical shape and a bottom portion thereof has a plurality of curved parts, and one or more of the shape memory alloy plates is The alloy plates are symmetrically inverted into a memorized shape and combined in parallel with the shaft, and the inverted shape memory alloy plate is returned to the memorized shape by heating, and the other shape memory alloy plate is inverted to move the shaft in two directions. This actuator is characterized by being driven by.

That is, as shown in FIG.
A rectangular plate of shape memory alloy made of
As shown in the figure, a shape having a large arcuate radius and small r ₁ and r ₂ at the bottom is memorized. One of these sheets is inverted to be symmetrical to the memorized shape at room temperature as shown in 1 in Figure b, and the shape memory alloy sheet 2 with the same memorized shape is placed in parallel and inserted into the shaft 4 via the stopper 3. The upper and lower ends of the shape memory alloy plates 1 and 2 are fixed, each can be heated separately, and is electrically and thermally insulated to serve as an actuator. To explain this operation, when the shape memory alloy plates 1 and 2 are stable at low temperatures in the state shown in Fig. 1b, when the shape memory alloy plate 1 is heated to a predetermined temperature, the shape memory alloy plates 1 and 2 change as shown in Fig. 1c. 1 returns to the memorized original shape. At this time, the shape memory alloy plate 2 jumps from the memorized shape of b to the shape of c, buckles and reverses, and even if the shaft 4 is driven to the right, stops heating, and is cooled, it remains stable in this state.
Next, in this state, when the shape memory alloy plate 2 is heated with electricity, the shape memory alloy plate 2 returns to its original memorized shape as shown in Fig. 1b, and the shape memory alloy plate 1 jumps, buckles, and reverses itself. , the shaft 4 is driven to the left and remains stable in this state. By repeating the above operations, it becomes possible to provide intermittent or continuous drive in two directions to the shaft.

However, the present invention provides at least one shape memory alloy plate.
Since the pieces are reversed from the memory shape and combined,
Since this jumps and reverses during operation and becomes buckled, a stable stationary state can be maintained during cooling.

In addition, in the present invention, the shape memory alloy plate is made into a bow shape or a cone shape, and is memorized in a shape having a plurality of curved parts at the bottom of the plate, so that when jumping in the opposite direction and reversing, the curved parts will cause Constraints in the direction or circumferential direction are relaxed, displacement becomes easy, and large distortions due to operation do not occur.

The number of shape memory alloy plates used in the present invention can be two or more, and it is preferable in terms of force balance during operation that half of these plates are inverted from the memory shape and combined. Instead of a rectangular shape, a disc shaped like a cone may be used. In addition to Ni-Ti alloys, shape memory alloys include Fe,
Ni-Ti alloys to which a third element such as Co is added, Cu-based alloys such as Cu-Al-Ni and Cu-Au-Zu, and commonly used shape memory alloys can be used. Further, as a heating method for the shape memory alloy, in addition to current heating, ordinary heating methods such as hot air and gas flame can be used.

(Example) An embodiment of the present invention will be described below.

As shown in Figure 1a, a strip-shaped plate made of Ni-Ti alloy is given a shape memory treatment with a large arcuate radius and curved parts r ₁ and r ₂ attached to its bottom. did. Next, this plate was turned over at room temperature, and as shown in FIG. 1B, the shaft 4 was passed through the alloy plate 2 and the stopper 3 together with the alloy plate 2 in the memorized shape to form an actuator.

Note that the shape memory alloy plates 1 and 2 can be heated separately by electricity, gas flame heating, or the like. The above actuator is in the first position at room temperature.
The shape memory alloy plate 1 remains stable and stationary in the state shown in Figure b, but when the shape memory alloy plate 1 is heated, the alloy plate returns to its memorized shape. At this time, the shape memory alloy plate 2 also jumps from the memory shape of b to the shape of c, reverses, and buckles.
Even when the shaft 4 is driven to the right, heating is stopped, and the shaft 4 is cooled, it remains stable in this state. Next, in this state, when the shape memory alloy plate 2 is heated,
The shape memory alloy plate 2 returns to its original memorized shape, and the shape memory alloy plate 1 also jumps and reverses buckling, and the shaft 4 is driven to the left and remains stable in this state. By repeating the above operations, it is possible to drive the shaft intermittently or continuously.

In the above, an example was explained in which the shape memory alloy plate 1 is inverted from the memorized shape and combined, but the alloy plate to be inverted may be either 1 or 2, and the initial heating may be applied to the inverted alloy. ,
Since that alloy returns to its original shape, the other alloy is reversed by that force and becomes buckled, and then by alternately heating it, drive in two directions can be obtained.

(Effects) As explained above, according to the present invention, by alternately heating a plurality of shape memory alloy plates, the shape can be reversed and the shaft can be moved, giving reciprocating motion in two directions, and the heating can be stopped and maintain its position even in low temperatures. In addition, since it is possible to select and maintain two required positions, and no large distortion occurs during operation, it has extremely significant effects such as a long cycle life.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the operating state of the actuator of the present invention, Fig. 2 is a schematic diagram showing the operating state of the actuator of the prior art, and Fig. 3 is a schematic diagram showing the operating state of the conventional actuator. It is a schematic diagram. 1... Shape memory alloy plate combined inverted, 2... Shape memory alloy plate, 3... Stopper, 4... Shaft,
5...Shape memory coil, 6...Coil spring, 7...Stopper, 8...Center shaft.

Claims (1)

[Claims] 1 A plurality of shape memory alloy plates are memorized into a shape having an arcuate or conical shape with a plurality of curved portions at the bottom thereof, and one or more of the shape memory alloy plates is inverted to be symmetrical with the memorized shape. An actuator characterized in that the shape memory alloy plate is assembled in parallel with the shaft, and the shape memory alloy plate reversed by heating returns to the memorized shape, and the other shape memory alloy plate is reversed to drive the shaft in two directions. .