JPH02129825A - Acceleration response switch and manufacture thereof - Google Patents

Abstract

PURPOSE:To make the operation of the switch in the title accurate by comtroucting a switch which operates an air bag under an abnormal condition for protecting persons in a car, with a sealed case containing mercury which works as an inertia element and an electric contact member, also providing a surface, that is wetted with the mercury, at the lower part of the case so as to clearly distinguish a difference between normal and abnormal acceleration. CONSTITUTION:An acceleration response switch main body 2 tilted so that its center axis line L has an angle A with respect to a synthetic resin case 1, is mounted on mounting parts 1A and 1B of a car body by using an adhesive 1C. Where, the main body 2 consists of a cylindrical case 2A having a bottom and a flange part 2B located at an upper opening edge part of the main body 2, a bowl shaped wet member 2C is fixed to the inner surface of the bottom part and the conductive liquid body 3 like mercury is stored thereon, and two parallel electrodes 2F1 are positioned above the liquid at an interval and filler 2G is forced to penetrate the other edges 2F; and the filler 2G is sealed with a lid 2D. A mixed gas G consisting of He and H2 is filled in the inner space of the cylindrical case 2A. In this way, the switch can be instantly operated in response to the acceleration produced in lateral direction of a car at the time of collision.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used as a switch for activating an airbag for the protection of automobile occupants in abnormal situations, and can be used in a switch that activates an airbag to protect the occupants of an automobile. This invention relates to an acceleration-responsive switch that distinguishes between large accelerations (this expression will be used hereafter, including decelerations) and turns an electric circuit from a zero stroke state to an ON state.

[Conventional technology]

Various types of acceleration responsive switches have been proposed. Examples include a pendulum, a spherical inertia, or a combination of a pressure sensor and a semiconductor circuit. Vehicles that run at high speeds, such as automobiles, are constantly exposed to various vibrations with different periods and accelerations during normal driving, depending on the road surface conditions such as not only paved roads but also gravel roads. An acceleration responsive switch is desired.

[Problem that the invention seeks to solve]

However, those that use solid inertia have poor durability, such as wear caused by vibrations that occur constantly during running, and those that use semiconductor circuits may malfunction due to disturbance pulses of t%. However, these methods alone have the drawback of being extremely unsatisfactory in terms of safety.

Means for Solving Problem c] In order to solve the above problem, the present invention airtightly seals a conductive liquid such as mercury, which serves as both an inertia element and an electric contact member, in an airtight container, and furthermore, in a normal driving state. By providing a surface wetted by a conductive liquid such as mercury at the bottom of the sealed container, it is possible to clearly distinguish between Its manufacturing method is also very simple.

[For production]

With the above-described configuration, the present invention has an IG generated when driving at high speed on a gravel road, etc. (IG in units of gravity is 980
It is possible to obtain an acceleration-responsive switch that does not malfunction even under vertical accelerations exceeding dyne centimeter (dyne centimeter) v) and operates in a short period of time in response to large accelerations mainly in the lateral direction that occur during a collision.

〔Example〕

As shown in the first factor, the acceleration-responsive switch body 2 is mounted on a case 1 made of synthetic resin, and the mounting parts IA and IB of the case 71 are mounted on a horizontal surface of a vehicle such as an automobile. However, when it is attached to an inclined surface, the angle A may be changed as appropriate. Details of the acceleration responsive switch body 2 are shown in FIGS. 2 and 3. In these figures, the bottomed cylindrical container 2A has a flange portion 21 at its upper open end and is made of an iron plate.The bottom inner surface of the cylindrical container method has a bowl-shaped wet container as described below. The member 20 is fixed by spot welding, fitting, etc. Symbol 8
A conductive liquid such as mercury is shown in . One body 2D is an annular body having a flange portion 21 made of an iron-cobalt-nickel alloy called copal, and a pair of electrodes 211 such as tungsten are melted in the inner cavity of an electrically insulating material such as hard glass. It is airtightly fixed to the filler 2G using a well-known hermetic sealing method. And the flange 2E of the lid body and the cylindrical shape! The flanges 2A and 2B are hermetically fixed by a method such as Schilling projection welding according to the procedure described later, and a mixed gas G of, for example, helium gas and hydrogen gas is substituted with air and sealed in the inner space of the cylindrical container method. has been done. A wet chip 2J'l, which has been treated to be wetted with the conductive liquid 8, is fixed to the lower tip of the electric conductor 11M2F by a method such as spot welding. The upper ends of the pair of electric FM2Fs are connected to an electric circuit (not shown) by an appropriate method. The hermetic seal for the lid is called a mating type, which uses members with almost the same thermal and expansion coefficients, but there is also a compression type, which has a 2L flange. The annular body is made of iron, the glass is soda-based soft glass, and the electrode is made of a nickel-iron alloy.It can be made inexpensively by using one in the center and the other by using the cylindrical container 2A instead of the electrode. .

The material of the wet member 20 and the wet tip 2F1 is nickel or iron. If iron is used, nickel plating is applied, and then gold plating is applied to a thickness of about 0.2 to 0.8 μm so that the nickel surface is oxidized in the air. This protects them from becoming inactive due to being damaged. With the wet member 20 fixed to two containers as shown in FIGS. 2 and 8, the container is placed in a chamber that can be evacuated, a predetermined amount of mercury is injected, and a predetermined amount of mercury is poured into the chamber lid. A lid body 2D is installed, the upper lid and lower part of the chamber are sealed with something like an O-ring, and the air inside the chamber is removed by a vacuum pump. After reaching a predetermined degree of vacuum, it is filled with an inert gas or the like.

Until this step, a slight gap is maintained between the flange portions of the cylindrical container 2A of the acceleration responsive switch and the lid 2D. Next, the chamber lid part has a double action structure that maintains airtightness and allows it to move up and down relative to each other, and even if atmospheric pressure is applied, this central part can withstand it with the repulsive force of a spring etc. However, if more force is applied, the flange 2E of the lid 2D will come into contact with the flange 2B of the cylindrical container 2A with a constant pressure while maintaining airtightness. , current is applied to both flanges to heat them and perform ring projection welding.

In other words, the chamber that applies contact pressure to both flanges is made of a material such as a chromium-copper alloy, and the electric charge stored in the capacitor is instantly released into this chamber, instantaneously concentrating Joule heat on the contact area of both flanges. A type of resistance welding is performed to create an airtight state.

On the other hand, when wet parts come into contact with mercury, the gold plated on the nickel surface to prevent it from oxidizing dissolves in the mercury, and then the pure nickel on the clean surface comes into contact with the mercury, forming a sheamalgam layer. Make sure the surface is completely moistened. Since the solubility of nickel in mercury is very low, this amalgam layer exists semi-permanently on the wet member. Therefore, the conductive liquid 8 containing a small amount of gold in mercury is wetted by the wet member fixed to the bottom of the cylindrical container, and its adsorption force increases depending on the length of the bottom surface and the direction rising from it. .

According to experiments, the inner diameter of two cylindrical containers is 6.6. When 1.6 grams of conductive liquid 3 is inserted when the height is - with Off, the angle formed by the acceleration response and the axis of the switch with respect to the plane of the mounting parts IA and IB of case 1 shown in Figure 1. If you make 60,! 1M
Wet chip 211'l provided at 21' and conductive liquid 8
The distance from the free surface of
, 5, when an acceleration of 20G is applied in the direction of the arrow shown in FIG. 1, the peak value of the barf sign waveform shown in FIG. It has the property of shorting out after 7 milliseconds, and we were able to obtain the result that malfunctions are unlikely to occur due to vibration acceleration caused by vibrations while driving on rough roads. Incidentally, Fig. 5 shows a region W in which malfunctions occur due to vibration acceleration that occurs while driving on a rough road, and a region S in which malfunctions do not occur. It is. When we examine the characteristics of the acceleration-responsive switches shown in Figures 1 to 8 by changing the vibration frequency in the vertical direction, we find that the curve A in Figure 5 shows that a simple piece of the same shape is used instead of the wet member. When we investigated the characteristics of a material made of an iron plate that does not get wet with mercury, we found that there was no change in response to the half sine wave shown in FIG. 4, but it was as shown by curve B in FIG. 5.

In addition, the wet tip 2II11 at the tip of the electrode 211' stabilizes the contact resistance and prevents chattering of the contact, and the OF when the half sine wave shown in FIG. 4 is applied.
This has the effect of lengthening the ON hold time when turned from F to ON.

As another embodiment of the wet member inside the cylindrical container, nickel plating and gold plating may be applied only to predetermined portions of the lower surface of the inner surface of the cylindrical container itself. In addition, as shown in FIG.
As a result of experimenting with a wet member made of iron having a portion A and plated with nickel and gold, it was found that it had the same effect as the bowl-shaped member shown in FIGS. 2 and 8. Furthermore, it has been found that the same effect can be obtained by using the above-mentioned surface-treated wet member on a thin pipe-shaped iron member as shown in FIG. It will be readily understood from the following description that this pipe-shaped member may of course be made of a nickel plate without needing to state it again.

A method of omitting gold plating on wet parts is to thoroughly clean the nickel surface of the wet parts by acid washing, etc., so that it comes into contact with mercury for a short time when a passive film is not formed due to atmospheric oxygen, etc. If this is possible, the nickel surface can be activated and the amalgam can be moistened by heating the wet part using an electric body that contains hydrogen gas inside the hermetically sealed interior. . In the case of pure mercury as a conductive liquid, the temperature is 1388"C.
It solidifies below, but if it is necessary to lower this temperature further, it can be made into an amalgam with 8.5% thallium dissolved in it, and it can remain liquid up to about -50°C.

Another method is to provide a resistance heating element or the like around the switch in the case of an acceleration-responsive switch according to the spirit of the present invention that uses pure mercury or a conductive liquid with a higher melting point (such as gallium or its alloy). If the temperature is always the atmospheric temperature υ
Since it can be increased, it is also possible to ensure that there are no inconveniences in the switch operation.

Although the cross-sectional shape of the acceleration-responsive switch in the embodiment is described as being circular, the shape of this cross-sectional area is not limited at all, and of course may be any circular shape or any polygonal shape as required. be.

〔Effect of the invention〕

As detailed above, by creating a wet state with the conductive liquid on the inner surface of the lower part of the cylindrical sealed container, which is always in contact with the conductive liquid, the adhesive force is applied to the gravitational force acting on the conductive liquid, which is an inertia. can be applied, restrain the conductive liquid at a predetermined position in the container against vertical vibration acceleration exceeding IG,
It prevents malfunctions during normal driving, and when abnormal acceleration is applied, the conductive liquid itself ruptures to produce a shifting motion, resulting in accurate operation.There is no mechanical wear, the structure is simple, inexpensive, and has excellent durability. It is possible to obtain an acceleration responsive device having the following characteristics.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view of the main part thereof, and FIG. 8 is a cross-sectional view of FIG. 2 as seen from the side. FIG. 4 shows the waveform of the applied acceleration, and FIG. 5 shows the vertical vibration that causes noise, and is for explaining the characteristics of the acceleration responsive switch of the present invention. FIGS. 6 and 7 show partial views of other embodiments, respectively. 2A: cylindrical container, 211': electrode, 8: conductive liquid. 2D...Lid body, 20...Wet member,

Claims (3)

[Claims] (1) A sealed cylindrical container filled with a conductive liquid, an electrode, and a gas for preventing contamination of the conductive liquid, and a surface that is wetted with the conductive liquid and is present in the height direction from the bottom of the container. Acceleration responsive switch. (2) After fixing a nickel plate or a wet member made of nickel plating on the surface of an iron plate and gold plating on the bottom surface of the iron cylindrical container by a method such as spot welding, a predetermined amount of conductive liquid is applied to the cylindrical container. After injecting the conductive liquid into a container and placing a lid having an electrode on the opening of the cylindrical container with a gap between them, placing them in a sealed chamber and removing air from the chamber, the conductive liquid is prevented from being contaminated. A method for manufacturing an acceleration-responsive switch, characterized in that the cylindrical container opening and the lid are hermetically fixed by a method such as ring projection welding in the atmosphere filled with an inert gas or the like. (3) After applying nickel plating to the lower inner surface of the iron cylindrical container, a predetermined amount of conductive liquid is injected, the lid body with the electrode is placed on the opening of the cylindrical container, and these are placed in a sealed chamber. After the air in the chamber is removed, the chamber is filled with an inert gas, hydrogen gas, etc. that prevents contamination of the conductive liquid, and the opening of the cylindrical container and the lid are hermetically fixed in that atmosphere. A method for manufacturing an acceleration-responsive switch, characterized in that a nickel-plated portion applied to the lower inner surface of a container is treated so as to be wetted with a conductive liquid.