JPH08232054A - Shape memory alloy coil spring and its production - Google Patents

Abstract

PURPOSE: To provide a shape memory alloy coil spring capable of acting differently at different temps. CONSTITUTION: This shape memory alloy coil spring is formed using a shape memory alloy wire partially having mutually different two or more kinds of transformation temps. on a shape memory alloy wire having the same compsn. and free from a joint. The shape memory alloy wire is made of an alloy consisting essentially of Ti and >=50.3at.% Ni. When this shape memory alloy coil spring is produced, plural positions of a coil spring 5 of a shape memory alloy having the same compsn. are heat-treated under plural kinds of treatment conditions different from each other in temp. or treatment time and the objective shape memory alloy coil spring having mutually different transformation temps. at plural positions of the coil spring 5 is obtd.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a shape memory alloy coil spring and a method for manufacturing the same.

[0002]

2. Description of the Related Art Several alloys containing a TiNi alloy as a main component show a remarkable shape memory effect in association with the reverse transformation of thermoelastic martensitic transformation, and at the same time exhibit superelastic characteristics.

It is known that a TiNi alloy having a Ni concentration of more than 50.3 atomic percent (hereinafter abbreviated as at%) reversibly exhibits a spontaneous shape change with respect to a temperature change.
This is disclosed in Japanese Patent No. 51445. Also,
It is also known that the transformation temperature of the TiNi alloy in the Ni concentration range can be arbitrarily changed depending on the heat treatment conditions. When using shape memory alloy as a spring, both coil spring and wire can be processed by uniform heat treatment.
It was used that exhibits a single function with some transformation points.

[0004]

For example, when a shape memory coil spring is used as a temperature-sensitive driving element, it has not been used for the purpose of snap action or stepwise work because it has a single function. That is, conventionally, the shape memory coil spring cannot be operated differently at a plurality of different temperatures.

An object of the present invention is to provide a shape memory alloy coil spring which can be operated differently at a plurality of different temperatures.

Another object of the present invention is to provide a method of manufacturing a shape memory alloy coil spring which can be operated differently at a plurality of different temperatures.

[0007]

According to the present invention, a shape memory alloy wire having two or more transformation temperatures partially different from each other is formed on one seamless shape memory alloy wire having the same composition. A shape memory alloy coil spring is obtained which is formed by using the shape memory alloy coil spring.

Further, according to the present invention, the shape memory alloy wire has a Ni and Ti concentration of 50.3 atomic percent or more.
A shape memory alloy coil spring is obtained which is made of an alloy containing i as a main component.

Further, according to the present invention, a plurality of portions of the coil spring of the shape memory alloy having the same composition are heat-treated under a plurality of kinds of processing conditions having different temperatures or different processing times, so that the plurality of portions of the coil spring are heated. A method for manufacturing a shape memory alloy coil spring, comprising obtaining a memory alloy coil spring having transformation temperatures different from each other.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

According to the present invention, in a coil spring of a shape memory alloy having the same composition containing TiNi as a main component having a Ni concentration of 50.3 at% or more, a plurality of kinds of treatments in which a plurality of locations are partially different in temperature or treatment time are treated. A shape memory alloy coil spring having a plurality of transformation points that is heat-treated in a furnace under the conditions, and a method for manufacturing the same.

By partially changing the temperature and time of the heat treatment for the same wire in this way, a memory alloy having different transformation points can be obtained for each portion, so that the change in shape with different transformation points can be achieved. By applying it, it becomes possible to automatically change the amount of opening and closing, such as opening and closing the ventilation port, according to changes in temperature.

In the embodiment of the shape memory alloy coil spring and the manufacturing method thereof according to the present invention, as shown in FIG. 1, one seamless coil-shaped spring material 5 made of a memory alloy material is used. In order to obtain different parts, they are partially covered with heat insulating materials 6 such as asbestos and bricks having different dimensions, and placed in a furnace at the same temperature and heat treated under constant conditions. As a result, a shape memory alloy coil spring having a plurality of transformation temperatures partially different depending on the difference in dimensions such as the thickness of the heat insulating material 6 can be obtained.

In another embodiment, a seamless coil spring made of a memory alloy material is partially inserted into the furnace through a hole formed in a part of the furnace wall and heat-treated under certain conditions. A shape memory alloy coil spring having different transformation temperatures is obtained by inserting the other part of the spring into the furnace and heat-treating it under different conditions different from the above conditions.

In still another embodiment, a coil spring made of a memory alloy material is transferred from one side to the other side in a furnace heated under a constant temperature condition, and the transfer speed is partially changed to partially Shape memory alloy coil springs having different transformation temperatures are obtained.

Specific examples of the shape memory alloy coil springs having two or more transformation temperatures obtained by these examples will be described.

As a first specific example, a drawn wire sample made of a TiNi alloy with Ni containing 51.0 at% of Ti and having a diameter of 1.0 mm is processed into a coil spring having a center diameter of 6 mm.
The heat treatment was performed at 400 ° C. for 30 minutes, and the heat treatment was further performed at 500 ° C. for 30 minutes while cooling half of the coil spring with water of 5 mm. The relationship between temperature and load was measured under the constant deflection of the spring thus obtained. The result is shown in FIG. Also, Ti-51 at% N
i alloy wire is cold worked at 30-40%, then 30 at 400 ℃
At the heat treatment temperature of 1 minute, the transformation temperature (here, reverse transformation start temperature) is 10 ° C, and at the heat treatment of 500 ° C for 30 minutes, the transformation temperature is 2
Indicates 5 ° C. As for the result of the temperature-load curve of the coil spring of this example, similar results are obtained as shown in FIG.

Further, from this figure, a clear jump in load change is recognized at 10 ° C. and 25 ° C.

The use of this type of spring is, for example, 20 ° C.
The ventilation port that needs to be operated at 30 ° C and 30 ° C, that is, at 20 ° C, the ventilation port is half opened and relatively gentle ventilation is performed.
It is possible to design an actuator having a two-step function that fully opens at ℃.

[0020]

As described above, according to the present invention, one seamless shape memory alloy coil spring material is provided with a plurality of transformation points by partially changing the heat treatment conditions. It is possible to obtain a shape memory alloy coil spring, and to perform different operations at a plurality of different temperatures.

The alloy according to the present invention is most preferably a TiNi alloy, particularly a TiNi alloy containing 50.5 to 51.0 at% Ni. Similar effects can be obtained with other shape memory alloys whose temperature can be adjusted.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining an embodiment of a method for manufacturing a shape memory alloy coil spring of the present invention.

FIG. 2 is a curve diagram showing the relationship between temperature and load at a shear strain of 1% or less in a specific example of the present invention.

[Explanation of symbols]

 5 Spring material 6 Insulation material

Claims (3)

[Claims] 1. A shape formed by using shape memory alloy wires having two or more kinds of transformation temperatures partially different from each other on one seamless shape memory alloy wire having the same composition. Memory alloy coil spring. 2. The shape memory alloy wire has a Ni concentration of 5
The shape memory alloy coil spring according to claim 1, wherein the shape memory alloy coil spring is made of an alloy containing Ti and Ni as main components in an amount of 0.3 atomic percent or more. 3. A plurality of portions of a coil spring of a shape memory alloy having the same composition are heat-treated under a plurality of kinds of processing conditions having different temperatures or different processing times, so that the plurality of portions of the coil spring have different transformations. A method of manufacturing a shape memory alloy coil spring, comprising obtaining a shape memory alloy coil spring having a temperature.