JP2795463B2 - Manufacturing method of two-way shape memory coil spring - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of manufacturing a two-way shape memory coil spring made of a shape memory alloy and having a large spontaneous shape change amount.

[Conventional technology and its problems]

Shape memory alloys are widely used in the industrial field, and there are many types of material shapes, but they are generally used as effective coil springs from the viewpoint of a shape capable of increasing the amount of change upon shape recovery.

As shown in FIG. 10, this coil spring uses a combination of a one-way shape memory coil spring (1) that stores only the shape of a parent phase, which is usually a high-temperature phase, and a bias spring (2). Since a bias spring is required, there are disadvantages in that the material cost is low, and the dimensions of the actuator and the like cannot be reduced.

Therefore, a coil spring using two-way shape memory that stores the shape of the martensite phase, which is a low-temperature phase, in addition to the high-temperature phase, has been developed, and attempts have been made to solve the above problems. The two-way shape memory coil spring repeatedly and reversibly deforms with respect to the rise and fall of the temperature. As shown in FIG. 11, the two-way shape memory coil spring expands at a low temperature of (a) and expands at a high temperature of (b). Shrinkage and elongation at the low temperature of (c),
The shape of (d) shrinking at high temperature is reversibly repeated. Conversely, there is a type that shrinks at a low temperature, elongates at a high temperature, shrinks at a low temperature, and expands at a high temperature reversibly.

It is known that these two-way shape memories appear when they are strongly deformed or heat-treated in a constrained state.

However, with such a method, it is difficult to accurately memorize the shapes on both the high-temperature side and the low-temperature side of the two-way shape memory coil spring, and it is difficult to control the generated force and the temperature hysteresis. It is difficult to perform the method, and the spontaneous shape change amount, which is the difference between the shape on the high-temperature side and the low-temperature side, is small. In particular, the spontaneous shape change amount of the two-way shape memory effect, which expands at a high temperature and shrinks at a low temperature, has been regarded as a problem.

[Problems to be solved by the invention]

As a result of examining the above problems, the present invention has developed a manufacturing method that can obtain a two-way shape memory coil spring having a large spontaneous shape change amount and excellent memory characteristics by a relatively simple method. is there.

[Means and actions for solving the problem]

The present invention forms a shape memory alloy wire into a coil spring, performs a shape memory heat treatment, rewinds the coil spring in a direction in which the coil spring is reversed in the axial direction, and then trains the coil spring to shrink at a high temperature. A method for producing a two-way shape memory coil spring characterized by imparting a two-way spring property extending at a low temperature, and further comprising forming a shape memory alloy wire into a coil spring, performing a shape memory heat treatment, and then forming the coil. After rewinding the spring in the direction of reversing in the axial direction, and then training the coil spring, rewind the coil spring in the direction of reversing in the axial direction. A method for manufacturing a two-way shape memory coil spring, which is characterized by imparting spring properties.

That is, according to the present invention, as shown in FIG. 1, the coil spring (1) made of a shape memory alloy wire such as a Ni—Ti alloy is first extended, for example, as shown in FIG. After performing a predetermined shape memory heat treatment, the coil spring is wound in a direction reverse to the axial direction as shown in FIG. The rewinding will be described in detail. As shown in FIG. 2, a coil spring (1) in an extended state is passed through a mandrel (3) as it is, one end of which is fixed by a fixing terminal (4), and the other end is mandrel. (3 ') is fixed to the fixed terminal (4'), the mandrel (3 ') is rotated in the direction of the arrow, and the coil spring (1) of the mandrel (3) is brought into close contact with the mandrel (3'). 1 '). At this time, if the first coil spring is a right-handed coil as shown in FIG.
As shown in FIG. 2B, the coils are wound to the left as shown in FIG. 2B, and the winding order of the coils is such that the coil located at the left end in FIG. 2A is located at the right end as shown in FIG. Reverse. By performing the rewinding to reverse the above-mentioned winding order, the amount of shear strain given to the coil spring becomes equal to the free length (ε ₀ ) of the coil spring (1) before the rewinding as shown in FIG. This means that a large amount of shear strain, which is obtained by adding the free length (ε ₁ ) of the replaced coil spring (1 ′), is added to the coil spring. As a result, it is attempted to return to the original memory shape at a high temperature, so that a close contact spring having a strong contact force can be obtained.

By the way, the coil spring which has been wound into the close contact state as described above is subjected to a training process in which heating and cooling are repeatedly performed while being stretched and fixed in a fixed shape as shown in FIG. 1 (c). is there. This situation will be described in detail. As shown in FIG. 5, a coil spring (1) is wound around a mandrel (3), one end is fixed by a fixed terminal (4), and another end of the coil spring is pulled in the direction of the arrow to be constant. The training that repeats heating and cooling is applied to the coil spring fixed in the shape of. The training conditions are heating at a temperature below the Mf point (martensite transformation end temperature) of the shape memory alloy at a low temperature and above the Af point (martensite reverse transformation end temperature) at a high temperature, as is clear from the examples described later. It is desirable that the repetition of cooling be performed in the range of 5 to 100 cycles,
Below this temperature and cycle, no improvement in the spontaneous shape change strain can be expected, and beyond this temperature and cycle, the spontaneous shape change strain is saturated. By the way, Ni50.3at%, Ti49.7
The at% Af point is 51 ° C and the Mf point is 24.5 ° C.

As shown in FIGS. 1 (d) and 1 (e), the coil spring manufactured through the above steps shrinks at a high temperature and expands at a low temperature in two directions. The spontaneous shape change strain is about 1%. Can be repeated in an extremely large range.

In addition, it has been confirmed that the above-described coil spring correctly stores the low-temperature and high-temperature shapes even in a low-temperature and high-temperature repeated cycle.

A coil spring in which the spontaneous shape change distortion amount is set to various values can be obtained by appropriately applying the above training.

Next, FIG. 1 (f) formed to shrink at the above high temperature
By rewinding such a coil spring as shown in (g) so as to make close contact as shown in (g), a coil spring which expands at a high temperature and contracts at a low temperature as shown in (h) and (i) is obtained.
That is, as shown in FIG. 6, the extended coil spring (1) is passed through the mandrel (3), one end is fixed by the fixed terminal (4), and the other end is fixed to the fixed terminal (4) of the mandrel (3 '). ′)
And rotate the mandrel (3 ') in the direction of the arrow to make the mandrel (3)
The coil spring (1) is re-wound to a coil spring (1 ') in close contact with the mandrel (3'). In this case, a coil spring in which the winding order is reversed as shown in FIG. 3 is obtained.

The thus obtained two-way spring that expands at a high temperature and contracts at a low temperature can also memorize accurate shapes at high and low temperatures, respectively.

Thus, the shape memory alloy wire used in the present invention, Ni-Ti and Ni-Ti alloy, or Cu-Zn-Al, Cu
Cu-based alloys such as -Zn-Au, Cu-Al-Ni, and other known shape memory alloys can be applied. From the viewpoint of corrosion resistance etc.
Ni-Ti and Ni-Ti alloy based wires are particularly preferred.

Further, the present invention can be applied to various springs having the same shape and function as the coil spring, and various wire shapes such as a round wire, a square wire, and a deformed wire can be applied.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described.

Example 1 A Ni—Ti alloy wire having a composition of 50.3 at% Ni and 49.7 at% Ti
Assuming that D / d = 9, pitch interval is 1 mm, and n = 8, FIG.
Then, the shape was held at 450 ° C. for 1 hour to carry out shape memory heat treatment. This is shown in FIG.
As shown in FIG. 2, the coil spring (1 ') is fixed to the mandrel (3), and the mandrel (1') is wound around the mandrel (3 ') having the same diameter rotated in the direction of the arrow. As shown in FIG. 3, a close contact coil spring in which the winding order was reversed was manufactured. Next, as shown in FIG. 1 (c) and more specifically, FIG. 5, the coil spring is stretched while maintaining the spring diameter of the close contact spring, and training is performed while fixing the coil spring in this shape, and FIG. 1 (d). And (e) a coil spring which contracts at a high temperature and expands at a low temperature. Next, 95 ° C, 20 ° C with 4.7% shear strain applied to the coil spring
FIG. 7 shows the relationship between the number of repetition cycles and the amount of spontaneous shape change strain when the heat cycle training was performed. From this figure, the spontaneous shape change distortion increased from around cycle 5, and increased by 40%.
It turns out that it is saturated from the vicinity. Therefore, if the cycle is in the range of 5 to 100, it is clear that a large spontaneous shape change strain can be obtained.

Next, natural length changes at 95 ° C. and 20 ° C. of the coil spring after the above-mentioned 50 cycles of training were measured. The result is shown in FIG. From this figure, it can be seen that the spring according to the present invention has a very large change in the spring length at high and low temperatures, that is, a spontaneous shape change strain, and that the shape is accurately stored even in a repeated cycle at high and low temperatures. Can be Note that the conventional one has a small amount of change in the spring length.

Example 2 The coil spring shown in FIG. 1 (f) produced in Example 1 was reversely wound again to produce a close contact spring as shown in FIG. 1 (g). The coil springs expand at a high temperature and contract at a low temperature as shown in (h) and (i). That is, as shown in FIG. 6, the extended coil spring (1) is fixed at one end by a fixed terminal (4) through a mandrel (3), and another end is fixed to a fixed terminal (4 ') of the mandrel (3'). ), And the mandrel (3 ') was rotated in the direction of the arrow to produce a coil spring (1') in which the coil spring (1) of the mandrel (3) was brought into close contact with the mandrel (3 '). 95 ℃ and 20 ℃ of this coil spring
FIG. 9 shows the results of measuring the change in natural length of. As is clear from the figure, the coil spring according to the present invention has a significantly larger change in the spring length than the conventional one. In addition, it was confirmed that the shape was correctly memorized even in a repeated cycle of high and low temperatures.

〔effect〕

As described above, according to the present invention, it is possible to obtain a two-way shape memory coil spring having a large amount of natural shape change strain and accurately storing a shape in a high-temperature and low-temperature repetition cycle by a relatively simple method. It has a remarkable industrial effect.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a manufacturing process of a two-way shape memory coil spring according to one embodiment of the present invention, FIG. 2 is a side view showing a coil spring rewinding process in the manufacturing process of the present invention, and FIG. FIG. 4 is a schematic diagram showing the order of winding the coil springs in the rewinding step of FIG. 2, FIG. 4 is an explanatory view showing the amount of shear strain caused by rewinding the coil springs, and FIG. FIG. 6 is a side view showing a spring tensioning method, FIG. 6 is a side view showing a coil spring rewinding method during the manufacturing process of the present invention, and FIG. 7 is a diagram showing the number of heating and cooling cycles of the coil spring by the manufacturing method of the present invention. 8 and 9 are diagrams showing the relationship between the temperature cycle of the coil spring and the spring length according to the manufacturing method of the present invention, and FIG. 10 is a diagram showing a conventional bias spring. FIG. 11 shows an example of using a one-way shape memory coil spring using The figure illustrates the operation of the two-way shape memory coil spring. 1,1 '... Coil spring, 2 ... Bias spring, 3,3' ...
Mandrel, 4,4 '…… Fixed terminal.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification symbol FI C22F 1/00 631 C22F 1/00 631A 685 685Z 686 686Z (56) References JP-A-59-162262 (JP, A) Shoji Ishikawa "Illustrations of Shape Memory Alloys Applied in Illustrations and Patents" (1987-12-1) Industrial Research Council PP. 21-22 E. Hornbogen, ed., "Martensitic Transform Sci Technology" (1989) INFORMATION SELLSCHAFT PP. 39-52 Akira Yazawa “Tohoku University Mineral Processing and Smelting Laboratory” (Showa 60-9-30) 41 [1] P.P. 35-44 (58) Field surveyed (Int.Cl. ⁶ , DB name) C22F 1/08 C22F 1/10 C22F 1/18 F16F 1/02 B21F 35/00

Claims (3)

(57) [Claims] 1. A shape memory alloy wire is formed into a coil spring, and after performing shape memory heat treatment, the coil spring is wound in a direction in which the coil spring is reversed in the axial direction. A method for producing a two-way shape memory coil spring, which comprises providing a two-way spring property that contracts and expands at a low temperature. 2. Forming a shape memory alloy wire into a coil spring, performing shape memory heat treatment, rewinding the coil spring in a direction in which the coil spring is reversed in the axial direction, and then training the coil spring. A method of manufacturing a two-way shape memory coil spring, comprising: rewinding the coil spring in a direction in which the coil spring is reversed in the axial direction to impart a two-way spring property of expanding at a high temperature and contracting at a low temperature. The training is performed at a temperature lower than the Mf point (martensite transformation end temperature) at a low temperature and at a temperature higher than the Af point (martensite reverse transformation end temperature) at a high temperature.
2. The method according to claim 1, wherein the operation is performed within a range of 100 cycles.
Or a method for manufacturing a two-way shape memory coil spring according to item 2.