JPS59110874A - Heating for driving body made of shape memory alloy - Google Patents

Abstract

PURPOSE:To improve heating characteristic by allowing magnetic fluxes to be generated in an annular iron core through the electric conduction to a coil wound onto a part of the annular iron core and allowing a driving body made of shape memory alloy to be heated by the Joule heat due to the induction current generated by the magnetic fluxes. CONSTITUTION:When a coil 2 is not conducting, a driving body 3 made of shape memory alloy is not given with heat and is maintained in extension state, and an operating body 5 is held at the position shown by the full line on the figure. When the coil 2 is held in conduction, magnetic fluxes flow in an iron core 1 which forms a closed circuit electromagnetically, and an electric current is induced in an O-ring 4 by the flowing magnetic fluxes, and Joule heat is generated. Therefore, the temperature of the driving body 3 rises, and the driving body 3 is contraction-deformed, and then the operating body 5 is shifted downward and positioned at the position shown by the broken line on the figure. By such a heating method, a large amount of heat can be obtained with a small electric power, and the operation characteristics of the driving body 3 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heating a driving body made of a shape memory alloy. Shape memory alloys utilize the phenomenon that occurs when the low-temperature phase generated by thermoelastic martensitic transformation is deformed and then reversely transformed into the high-temperature phase by heating.
The structure changes to austenite on the higher temperature side of the transformation point, and changes to the martensite structure on the lower temperature side. When this shape memory alloy is cooled from the high temperature side, it transforms from an austenite structure to a martensitic structure, and has superelasticity.On the other hand, when it is heated from a low temperature side, a martensitic structure transforms to an austenite structure and is formed. It returns to the shape memorized during the process. Nickel-titanium, copper-aluminum-nickel, copper-aluminum, etc. are known as alloys that exhibit such a shape memory effect. For example, it is used as a driver (coiled shape memory alloy) for opening and closing a valve, as described in publications.

However, the heating and cooling means necessary to operate these actuators are based on the control fluid flowing down the valve, and such methods make it impossible to change the temperature of the control fluid. It has the disadvantage that it is unsuitable for applications in which temperature changes cannot be obtained and is unsuitable for wide valve applications. Also, JP-A-57-1887
No. 15 and JP-A-57-25572 disclose a method of directly heating an expandable member made of a shape memory alloy and a valve driving element with a heater. Because of this, a large amount of power is required, and heaters that are generally small in diameter are used, but they require repeated heating and cooling, as well as expandable and contractable members.
This included the risk of heater breakage due to the reciprocating movement of the valve drive element. Furthermore, in the method of winding the heater directly around the expandable member or valve drive element, it is necessary to place an insulating film to insulate the heater from those parts and elements, which makes efficient heating difficult. It was.

The method of heating a driving body made of a shape memory alloy according to the present invention was developed in view of the above-mentioned drawbacks, and the driving body is heated directly and electrically without heating or cooling the driving body using an environmental temperature such as a control fluid. As a result, it can be widely used as a drive body for all kinds of products, and compared to a drive body that is directly heated with a heater, it can generate a large amount of heat with a small amount of electric power. The purpose of this invention is to heat the driving body more directly and to obtain a heating method with excellent heating characteristics.

Hereinafter, an embodiment of the heating method for a driving body made of a shape memory alloy according to the present invention will be described with reference to FIG.

Reference numeral 1 denotes an iron core made of a magnetic material and forming a magnetically closed circuit, a coil 2 is wound around one side IA of the iron core, and a driving body made of a shape memory alloy is wound around the ground side IB of the iron core l. A coil spring 3 is disposed, and a ring 4 made of a flexible material is disposed around the driving body 3. One end of the coil spring serving as the 0σ drive body 3 is fixed (in this embodiment, the ring 4
The other end is held in a free state, and the operating body 5 that transmits the displacement of the driving body 3 to the outside 8 is engaged with the protruding end. In the coil spring as the driving body 3 made of the shape memory alloy, when the temperature decreases at the martensitic transformation starting point (point M), the driving body 3 starts to undergo elongation deformation, and the martensitic transformation ending point (Mr point)
This deformation stops when the temperature rises, and at the reverse transformation starting point (point A), the shape starts to be restored and shrinkage deformation starts to tin, and the contraction ends at the reverse transformation starting point (point A1). It returns to the shape set.

Next, to describe its operation, when the coil 2 is de-energized, no heat is applied to the drive body 3 made of a shape memory alloy, so the drive body 3 reaches the reverse transformation temperature (A, point ), therefore, the driving body 3 is held in an extended state, and the operating body 5 is placed at a high position as shown by the solid line in the figure and held at the first position.

Next, when the coil 2 is energized, a magnetic flux passes through the core 1 due to the magnetically closed circuit of the core 1, and a current is induced in the ring 4 by this passing magnetic flux. Joule heat is generated in the ring 4 by the induced current flowing in the ring 4, and the temperature of the inner body of the ring 4 is rapidly increased. According to this temperature rise of ring 4, ring 4
The driving body 3 placed close to the ring 4 also receives heat transfer from the ring 4 and sees a temperature increase, and as the temperature of the driving body 3 rises from the reverse transformation starting point (entry point), the driving body 3 increases. Shrinkage begins, temperature rises further, and reverse transformation ends (Ar
The contraction is completed when the driving body 3 reaches point).
Due to the contraction and deformation, the operating body 5 is also displaced downward in response to this, and is maintained at the second position as indicated by the dotted line in the figure. In this actual case, when the temperature drops at the martensitic transformation starting point (point M), the driving body 3 expands and deforms, and when the temperature rises, it shrinks and deforms at the reverse transformation starting point (entry point), but this deformation Conversely, when the temperature decreases at the martensitic transformation starting point (point M), the driving body 3 may be contracted and deformed.

According to the method of heating a driving body made of a shape memory alloy as described above, an induced current is generated in the ring 4 by the magnetic flux generated in the iron core l by energizing the coil 2, thereby causing the ring 4 to self-heat. The heat generated by 4 can be obtained by obtaining a large amount of heat with a small current, and since the power supply current is not directly connected to the ring 4, there is no insulation coating between the ring 4 and the drive body 3. There is no need to dispose the drive body 3, and in addition to the large amount of heat generated, it is possible to improve the heating characteristics for the drive body 3. Furthermore, compared to a heater made of wire, the heat generating part is ring-shaped, so the risk of wire breakage due to repeated heating and cooling and external vibrations can be eliminated, and it can be used stably for a long period of time.

Further, according to the structure in which the ring 4 is arranged around the ground side IB of the iron core 1 and the driver 3 is further arranged around the outer periphery as shown in FIG. 2, the circumferential length of the ring 4 can be shortened by being close to the iron core 1. Therefore, it is possible to obtain a large induced current, thereby increasing the amount of heat generated by the ring 4 and improving the heating characteristics.

Furthermore, by forming the iron core 1 by laminating and bending laminated silicon m plates, it is possible to improve the magnetic flux efficiency of the iron core 1. Accordingly, the induced current can be increased and the ring 4
It is possible to increase the heat generation and improve the heating characteristics.

Further, as shown in FIG. 3, one side 10A of the iron core 10 is branched into a plurality of iron cores 10B and 100, and these iron cores 1033.

When the ring 14 surrounding each of the iron cores 10B and 10Q is arranged, the iron cores 10B and
A turtle current is generated, and the heating characteristics for the ring 4 are further improved, and a large amount of heating can be applied to the driving body 3 with a small current.

Furthermore, as shown in Figure iiJ, when the terminals 3B of the driving body 3 are connected to form an electrically closed circuit, an induced current is generated in the ring 4 and the driving body 3 due to the magnetic flux passing through the iron core 1, and as described above, an induced current is generated in the ring 4 and the driving body 3. In accordance with the self-heating caused by the induced current in the ring 4, the driving body 3 also generates self-heating due to the induced current, which can significantly improve the heating characteristics of the driving body 3.Furthermore, due to the self-heating of the driving body 3, The driving body 3 can be heated uniformly and its dynamic characteristics can be improved as the temperature increases.As described above, according to the method of heating a driving body made of a shape memory alloy according to the present invention, A coil is wound around the iron core, and a driving body made of a shape memory alloy and a ring made of a conductive material are arranged around the iron core, and the magnetic flux generated in the iron core causes the ring to generate self-heating due to an induced current. By heating the driving body with the ring, a large amount of heat can be obtained with a small current, and there is no need to place an insulating film between the ring and the driving body, allowing heat to be transferred directly from the ring to the driving body. Therefore, the heating characteristics can be improved, and since the heating part is a ring rather than a wire heater, there is no danger of @@, and it can be used stably for a long period of time.

In addition, the magnetic flux efficiency of the iron core can be improved by making the iron core laminated and bent and laminated, and the heat generation amount of the ring can be increased with a small current. By arranging a ring around each of these magnetic flux paths, it is possible to increase the induced direct current generated within the ring, thereby increasing the heat generating portion of the ring. Furthermore, if the drive body is an electrically closed circuit, the drive body generates heat by itself, and in addition to the heat generated by the ring, it is desired to improve the heating characteristics. The body itself is heated evenly and its dynamic characteristics are further improved.

[Brief explanation of the drawing]

The figure is a system diagram including a sectional view of essential parts showing an embodiment of the heating method for a driving body made of a shape memory alloy according to the present invention. This is an example. l...Iron core 2φ...Coil 3...Driving body 4 made of shape memory alloy...Ring 5...Moving body (11)

Claims (1)

[Claims] l) A coil is wound around an iron core made of a magnetic material forming a magnetically closed circuit, and a driving body made of a shape memory alloy and a ring made of a conductive material are arranged around the iron core, A method of heating a driving body made of a shape memory alloy, in which the magnetic flux generated in the iron core by energizing the coil causes self-heating due to an induced current in the ring, thereby heating the driving body. 2) A method for heating a driving body made of a shape memory alloy according to claim 1, in which the iron core is laminated. 3) A method for heating a driving body made of a shape memory alloy according to claim 1, wherein a plurality of magnetic flux paths are formed by an iron core, and a ring is arranged around each of the magnetic flux paths. 4) A method for heating a driving body made of a shape memory alloy according to claim 1, wherein the driving body made of a shape memory alloy is formed into a magnetically closed circuit.