JPH0356331B2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to a coil spring formed of a shape memory alloy, and more specifically, for example, in a dryer, refrigerator, etc., using temperature sensing to control the operation of parts. This invention relates to improvements in tension coil springs formed from shape memory alloys.

<<Prior art and its problems>> Normally, a tension coil spring 1 is made by winding a linear spring material as a coil body 2 having a constant diameter as shown in FIG. It integrally has a hook portion 3 formed into a hook shape by standing up from the top.

However, since the hook portion 3 rises abruptly, the curvature of the bent portion 4 is small, and therefore the combined internal stress of bending stress and torsional stress concentrates on the bent portion 4.
As shown in FIG. 7, as the coil body 2 repeatedly separates due to operation, internal strain occurs around the bent portion 4, and the process of progressing internal strain leading to breakage was often observed.

Similarly, when a tension coil spring made of a shape memory alloy is formed and operated as shown in Figure 6, the rigidity is extremely low below the martensitic transformation temperature of the alloy itself, as shown in Figure 8. Therefore, the amount of deflection increases and the deformation of the bent portion 4a also increases proportionally.

The bent portion 4a naturally fluctuates due to deflection during operation.
At the same time as the breakage rate increased in the periphery, breakage itself became more likely to occur earlier.

<Means for Solving the Problems> The present invention has been devised to effectively solve the problems in the use of the conventional tension coil springs made of shape memory alloys. , a wound portion made of a shape memory alloy, such as a Ni-Ti alloy;
After forming a coil spring body consisting of a terminal part extending from the terminal winding part and subjecting it to memory capacity treatment, cold working means is applied from the terminal winding part to the terminal part of the coil spring body. By applying this, a work-hardened layer is formed on the surface of the coil spring body.

<<Operation>> Accordingly, in the present invention, the area from the end winding part to the terminal part of the coil spring body formed of a shape memory alloy becomes an internal stress concentration area during operation, but the periphery of the concentration area is cooled. Since a work-hardened layer is formed by the processing means, the surface layer formed by the processing means is uniformly hardened, so that the elastic modulus of the hardened layer is several times higher than that of other spring parts, and the memory The characteristic is that memory deterioration occurs only in the work-hardened layer portion, and therefore that portion does not deform.

<<Example>> Hereinafter, the present invention will be described in detail based on an example illustrating the present invention. FIG. 1 shows a coil spring body 1 used in the present invention.
This is an explanatory diagram showing the case of a tension coil spring when a cold work hardened layer is formed on the coil spring body 10. As shown in the figure, the coil spring body 10 is made of a shape memory alloy such as Ni-
It is formed by processing a Ti alloy into a wire rod and using the wire rod.It is formed by winding a predetermined number of turns of a winding part 11 having the same coil diameter using a spring winding machine, and then the winding part In the illustrated example, the end portion serving as the hook portion 12 is formed to extend by making both end winding portions of the hook portion 11 stand up at right angles.

Due to the shape memory alloy, the coil spring body 10 requires further imparting memory ability as another process,
In this step, both the winding part 11 and the hook part 12 are fixed and held using a predetermined jig, and then heat-treated at about 500 DEG C. for about 1 hour to add memory capacity.

Unidirectional shape memory is added by the memory capacity processing step.

Next, in order to cold-work the parts where internal stress is concentrated during operation, the wound part 11 and the outer peripheral surface 13 are
A ring attachment body 16 made of a material such as rubber or flexible resin is inserted into contact with the ring member 16 .

The fitting includes a hook part 12 which is a terminal part, a terminal winding part 14 connected to the hook part 12, and in some cases a next winding part 15 connected adjacent to the terminal winding part 14.
The inserted state is such that even a part of it is exposed and opened.

Next, from this state, as shown in the figure, metal granules 18 or glass granules 18 having a predetermined particle size are injected from the injection tube 17 at high speed, and the granules are uniformly applied to the necessary locations, so that the surface to be sprayed is cold-worked. Due to the cold working, the concentration of internal strain causes hardening of the surface layer.

FIG. 2 shows a state diagram in which the tension coil spring body 10 subjected to cold working according to the above embodiment is deformed by applying a load in the directions of arrows P and _P1 shown in the figure. The portion where a surface hardening layer has been formed due to processing is indicated by a diagonal line H. The diagonally shaded portion H causes almost no deformation under load and maintains the current state before the load state, but the other wound portions 11 are under load pressure. Follow and distract.

Therefore, even if the part on which the work-hardened layer is formed is subjected to repeated operations of temperature sensing and load pressure, it will not deform under load and will remain in its current state, resulting in a phenomenon of concentration of internal stress. This means that you will hardly receive any.

FIG. 3 shows a coil spring body 20 in the case of a torsion spring, which is another embodiment, and its wound portion 11
The arm portion 22 extending linearly from the terminal winding portion serves as the terminal portion, and by applying the same cold working means to the periphery of the arm portion 22, the same effect as described above can be achieved. can be obtained.

Figure 4 shows the temperature load characteristic diagram of a coil spring that has not undergone cold working treatment after shape memory treatment. Below the Mf point, that is, the end temperature of martensite, deformation begins with a load of P _{1 and} temperature sensing occurs. The amount of displacement of the coil spring due to temperature, that is, the deformation stroke, also has a value of Δ1.

However, if cold working is performed after shape memory treatment, deformation will begin from a load of P ₂ below the Mf point, that is, the martensite finish temperature, as shown in FIG.

Therefore, the amount of displacement, that is, the deformation stroke also takes a value of Δ2, and the amount of deformation becomes smaller by the difference between the loads _P1 and _P2 .

≪Effects of the Invention≫ As described above, the present invention uses a shape memory alloy to be wound around a coil spring body having end portions such as a hook portion and an arm portion, and when the coil spring body is operated. Since the coil spring body is characterized in that a work hardening layer is formed on the surface of the coil spring body by applying cold working means to the portion where the load of internal stress is concentrated, only shape memory treatment is required for the coil spring body. The stress concentration area is work hardened and the amount of deformation is extremely small compared to the case where the stress concentration area is work hardened.

This reduces stress concentration even after long-term use, eliminating breakage accidents and extending the life of the coil spring.

Further, since the hook portion and arm portion of the coil spring are not extended unnecessarily, the installation space can be reduced and the bias spring can be made smaller.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional front view of a tension coil spring formed from a shape memory alloy according to the present invention, in which a ring attachment body is fitted and subjected to cold working;
The figure shows a coiled spring body made of a shape memory alloy obtained according to Fig. 1, and is an explanatory front view with the cold-worked portion shown in diagonal lines, and Fig. 3 shows a coiled spring body made of a torsion spring. A plan view showing an example of
Figure 4 is a diagram showing the relationship between temperature and load before applying the cold working means, Figure 5 is a diagram showing the relationship between temperature and load after adding the cold working means, and Figures 6 to 8 show conventional examples. , Fig. 6 is a partial front view of a tension coil spring, Fig. 7 is a front explanatory view showing deformation when a load is applied to it, and Fig. 8 is a spring formed from a shape memory alloy when a load is applied to it. It is a front explanatory view showing a deformed state. DESCRIPTION OF SYMBOLS 10, 20... Coil spring body, 11... Winding part, 12... Hook part as a terminal part, 14...
End winding part, 22...Arm part as a terminal part.

Claims (1)

[Claims] 1. After forming a coiled spring body consisting of a wound portion and a terminal portion extending from the terminal wound portion by winding a shape memory alloy, and applying a memory ability treatment to this,
A shape memory alloy having a locally hardened layer, characterized in that a work hardening layer is formed on the surface of the coil spring body by subjecting the coil spring body to cold working from the terminal winding part to the end part. Spring.