JPS63280905A - Screw difficult to be loosened - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a screw that is difficult to loosen.

[Conventional technology]

Conventionally, as a method to prevent screws from loosening, it was used for eyeglass frames [Example 1]
A notch is created in the longitudinal direction of a part of the threaded part of the screw, a piece of resin (without threads) is press-fitted into that part, and the friction between the resin and the threaded part of the screw hole is used when screwed in: [Example] 2] Apply resin powder to the threaded part of the screw and use the friction between the resin and the screw when screwing in: [Example 3] After screwing, apply adhesive to the mating part and tighten the screw and screw hole. The following methods were used: gluing the

[Problem that the invention seeks to solve]

The problems with the conventional technology as described above are that in the case of Example 1, the processing is complicated and the cost is high, and the strength of the threaded part decreases due to the notch in the threaded part. Screws have drawbacks that make them inapplicable.

In the case of Example 2, once the screw is screwed in, the resin powder is crushed, so when the screw is unscrewed and screwed in again, the loosening prevention effect is significantly reduced.

In the case of Example 3, adhesives that are so strong that screws cannot be pulled out are inconvenient when parts need to be replaced, so adhesives with weak adhesive strength are used, so the loosening prevention effect is low, or It protrudes around the area and looks dirty.

etc.

[Means for solving problems]

SUMMARY OF THE INVENTION Therefore, the present invention provides a screw that is made of a shape-memory alloy and has a shape memorized before use, which is different from that at the time of use.

[Effect]

Shape memory alloys can have shape memory as is known. Therefore, in the present invention, a shape different from the shape when used is stored in the screw in advance.

Therefore, when using the screw of the present invention, that is, when it is fitted into the screw hole (
If you carry out the process of recalling the memory while the screw is still in place (screwed), the contact with the screw hole will become more tense, making it more difficult to loosen.

For example, a shape memory alloy is made to memorize the shape of a wire in a high-temperature state, and then a thread is formed by plastic deformation, such as rolling, at a low temperature to obtain a screw. In other words, a wire rod whose shape (e.g. external dimensions) is memorized shrinks in cross section due to rolling.
It is also stretched in the axial direction to create the shape of a screw.

After this rolled screw is fitted into a screw hole, when heated to the A phase (austenite phase) region, the screw attempts to recover its original linear shape, expands in cross section, and contracts in the axial direction. Therefore, (A) there is no gap between the screw and the screw hole in the fitted state, which is inevitable with normal screws, and a perfect fit is obtained.

(B) In the direction of the screw, the screw tends to expand in the radial direction, so the screw receives a radial resistance from the screw hole.

(C) Since the screw tends to contract in the axial direction in the direction of the screw, the screw receives a resistance force in the axial direction from the screw hole.

Due to the increase in the contact area between the screw and the screw hole due to (A) above and the drag force in (B) and (C), the frictional force between the screw and the screw hole increases, and as a result, the screw is difficult to loosen. Become.

Table 1 shows the relationship between the effects (A), (B), and (C) after rolling and the wire diameter d before rolling.

Table 1 Table 1 (continued) d: Radius of memorized wire ○: Large effect dl: Thread diameter Δ: Small effect d2: Thread root diameter
×: No effect (see Figure 3) Therefore, d, ≧d! In other words, if the wire diameter before rolling is equal to or larger than the screw root diameter, it can be said that there is an effect of preventing screw loosening, but d
, ≧d, that is, when the wire diameter before rolling is larger than the thread diameter, the effect is large and desirable.

There is hysteresis in the phase transformation temperature during heating and cooling of shape memory alloys, and when heated from the M phase, which is stable in a low temperature range, the temperature at which the transformation to the A phase starts is the As point, and the temperature at which the transformation to the A phase is completed. The temperature at which the A phase begins to transform to the M phase when it is cooled from the A phase, which is stable in a high temperature range, is called the As point, and the temperature at which the transformation to the M phase is completed is called the 1 point.These temperature characteristics are It varies depending on the composition of the shape memory alloy, heat treatment conditions, processing history, etc.

In the present invention, since it is necessary to drive the screw in the M phase state, the As point is preferably above room temperature, that is, above 30°C.Also, when the screw is stored, transformation to the A phase occurs. In order to prevent this, it is preferable that ^S is 30°C or higher.

On the other hand, screws can be removed when replacing parts, etc.
If the screw is removed in the A-phase state, which is preferably reusable, it will deform as it tries to return to its pre-rolling shape, making it impossible to reuse it.

Therefore, for the purpose of completely transforming the human phase screw into the M phase using an easy-to-handle cooling device, it is necessary that Mf be at least -10°C.

〔Example〕 Next, the hinge screw shown in FIG. 6 and 7 will be described as an example.

From an ingot of 50.5at%Nr-49.5at%T, it was heated to φ6mm by hot rolling and hot swaging processing.
After obtaining a round bar, cold wire drawing and intermediate annealing are repeated,
A straight round wire (wire rod) with a diameter of 1.5 l1m was obtained.

This round wire was heat treated at 400° C. for 1 hr to memorize its shape and dimensions. When the temperature characteristics of resistivity of this sample were measured, a curve as shown in FIG. 4 was obtained. From this curve, the transformation start temperature Ms point of the M phase of this alloy is 20℃,
It was found that the end temperature Mf point was 10°C, the A phase transformation start temperature As point was 30°C, and the transformation end temperature Mf point was 40°C.

Next, this round wire is cooled to 0°C to completely transform into the M phase, and then threaded by rolling at 20°C.
A hinge screw with a screw diameter of 1.4 m, a pitch of 0.3 mm, and a length of 4.9 mm as shown in Fig. 2 was obtained.

After assembling the eyeglass frame by fastening the nickel silver hinge pieces shown in Fig. 6 and 8 using these screws, the frame metal body is
m1n, and the hinge screw was transformed into an A-phase state.

This 8! A hinge screw loosening test was conducted on the mirror frame to measure the degree of loosening. The outline of the hinge screw loosening test is to fix the front part shown in FIG. 6, apply loads alternately in the vertical direction to the temple shown in FIG. 6 and 12, and simultaneously open and close the temple.

The tightening torque of the screw is 600g- (up to), and the vertical load on the temple is ±20g per load speed for 5 cycles/
Sec, the opening/closing angle of the temple is 90', and the opening/closing speed is 0.
Changes in screw loosening torque were measured at 5 cycles/sec and a test time of 5 minutes. The test temperature was 25° C., where the screw was in complete A phase.

As a result, as shown in Table 2, no screw loosening was observed with the screws of the present invention, but with the conventional stainless steel screws, a significant decrease in loosening torque was observed after the test.

Table 1 (Screw loosening torque before and after screw loosening test: unit g-
cm) Next, in order to understand the effect of the screw of the present invention in a low temperature range, after tightening the screw, the eyeglass frame was cooled to 0°C, the screw was completely transformed into the M phase, and then the screw was completely transformed into the M phase at 25°C. When the above hinge screw loosening test was performed in phase state, the screw tightening torque was 600 g-c.
In the case of a+, the screw loosening torque is 600 g- before the test.
After the test, the weight was 600 g, and it was found to be sufficiently effective.

In addition, if the screw is cooled to below -HO℃ and changed to the M phase state, then the screw is removed, the change in the shape of the screw is small, and it can be screwed in again after replacing parts. It was found that if the material is transformed into phase A by heating after screwing, the effect of preventing the screw from loosening does not deteriorate at all. However, if the screw is pulled out at room temperature without cooling, that is, in the A-phase state, the screw will immediately try to return to its original round wire shape, causing deformation such as an increase in the screw diameter. It was also found that it could not be reused.

Further, the screw head machined in the M-phase state attempts to return to the φ1.5 mm round wire memorized in the A-phase state by heating to a high temperature range. In shape memory alloys, 8 in the M phase is generally
% deformation will be recovered by transforming into A phase, but deformation beyond that will remain as plastic deformation without recovery, so M
For screw heads that have a machining rate of 30% or more in the A phase region, even if the deformation recovers in the A phase region, the screw head shape is such that it does not significantly impair the removal and removal functions, making it difficult to replace parts. I also found out that there is no such thing.

Shape memory alloys applicable to the screw of the present invention include T1Ni.
(May contain trace amounts of additional elements such as Crs Fe)
Not only CuA e Ni or CuZnX
(X = Six Sl1% ^1 etc.) or FeNiTiC.

There are iron-based products such as

In addition, for the memory treatment before thread processing, after forming the work-hardened material by cold working as in the example,
In addition to medium-temperature treatment in which the product is maintained at a temperature of around 1hr, it is subjected to normalization annealing at a high temperature of 800℃ or higher, and after forming in an annealed state, low-temperature treatment is performed in which it is memorized at 200 to 300℃.
Alternatively, there is an aging treatment in which aging is performed at a temperature of around 400° C. for several hours after solution treatment, and these may be appropriately selected depending on the material, taking into consideration thread workability or thread strength.

In addition, the round wire diameter before thread processing is determined by thread workability, thread strength, A
It may be selected appropriately in consideration of the degree of shape deformation after the change B to the phase.

〔Effect of the invention〕

As described above, after the screw according to the present invention is screwed into a screw hole, when the memory shape is recalled, the loosening of the screw is eliminated. Other points: (1) When used for the hinge screw shown in Fig. 6, 10, the opening/closing torque of the temples will not decrease even when the glasses frame is worn for a long period of time, and the glasses frame will not flap. The hook can be removed smoothly.

(2) When used for the rim opening shown in Fig. 7 and 8, the holding power of the lens does not decrease even when wearing the eyeglass frame for a long period of time.
It is possible to prevent the lens from falling off due to the rim screw coming off, which often occurs with ordinary screws.

(3) When used for the pad screw shown in FIG. 7 or the eyebrow screw shown in FIG. 7 and FIG. 9, parts are prevented from falling off due to the screw coming off.

Furthermore, by cooling to a low temperature, the screws can be pulled out relatively easily, and the screw loosening prevention effect can be maintained even if the screws are reused.

Furthermore, since no notches are made in the screws, there is no reduction in the strength of the screws, and the present invention can be applied to small-diameter screws (for example, 1.2 mm band screws).

Furthermore, there is no problem of appearance deterioration due to adhesive application.

[Brief explanation of drawings]

FIG. 1 is a front view of a screw according to an embodiment of the present invention. 2 is a top view of the screw of FIG. 1; FIG. FIG. 3 is an explanatory diagram illustrating a partial cross section of the screw and its radius. FIG. 4 is a graph showing changes in electrical resistance due to phase transformation of a shape memory alloy. FIG. 5 is a schematic cross-sectional view illustrating the relationship between a screw (male screw) and a female screw. FIG. 6 and FIG. 7 are exploded explanatory diagrams explaining a general eyeglass frame [Explanation of symbols of main parts] 51--1--Screw 52-------
・Female screw L-・-・Band 1a-・・・・
-Insert butterfly 2...-111...Pad core 2a--
--- Pad foot 3 --- Pad box 4 ---
−−−−・−Pad foot 5・・・Blow Ji 6・
−−−1−−・−・−Eyebrow metal fittings 7−・・・・・・Band screw 8・−・・・・・・−・Rim screw 9・−・−・
Eyebrow screw 10-...Hinge screw 11...
・−・−Hinge 12・・−・−・Temple 13
・・・・・・−・Previous cell 14−・−・−Cover 1
5・・・・・・Eroi Chi 16---Um17
・・－－－－Mayu

Claims (1)

[Claims] 1. A screw that is made of a shape memory alloy and is difficult to loosen, and is characterized in that it memorizes a different shape from the time of use before use. 2. The screw according to claim 1, wherein the screw is an eyeglass frame screw. 3. The shape memory alloy has a transformation temperature (Af) to an austenite phase of 30°C or higher and a transformation temperature (Mf) to a martensitic phase of -10°C or higher. Screws described in item 1.