JPH04312725A - Acceleration detector - 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]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to acceleration detectors. Specifically, the present invention relates to the configuration of a novel acceleration detector that is robust and highly safe and can be mounted on a moving body to easily detect acceleration and impact force.

0002

[Background Art] In recent years, the safety of moving objects, especially automobiles, has become important, and for example, airbag systems or passive seat belts have been developed to protect drivers and passengers in the event of a collision. It is being said. Such a system requires an acceleration detector that can easily detect when a certain acceleration or impact force is applied.

[0003] Generally, the following are known as commonly used ones. FIG. 7 is a diagram (part 1) showing an example of a conventional acceleration detector, which is a so-called semiconductor type.

That is, this semiconductor acceleration detector 10
0, for example, a cantilever 101 that can be displaced when an external force is applied to a silicon substrate is formed, and a gauge part 102, for example, a strain gauge, and an IC circuit 103 such as an amplifier as shown on the same substrate are formed at the base of the cantilever 101. It is formed.

Now, when a certain external force is applied, the cantilever 1
01 is displaced and distortion occurs in the gauge portion 102, the resistance value changes, and the IC circuit 103 extracts this as an electric signal to detect external force acceleration.

FIG. 8 is a diagram showing an example of a conventional acceleration detector (
Part 2) is the so-called mercury type case. This example is a type of mercury relay 200, with an inclined glass tube 201
A pair of terminal electrodes 202 and mercury particles 203 are enclosed within the holder, and when the device is at rest, the mercury particles are at the position 203', so that the terminal electrodes 202 are in an open state. However, when an external force is applied, the mercury particles move up the slope of the glass tube 201 to the position 203, causing a short circuit between the terminal electrodes 202 (SH
ORT), so the configuration is such that the external force acceleration is extracted as an electrical signal and detected by a detection circuit (not shown).

[0007]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional acceleration detectors, for example, in the case of a semiconductor type, an accident occurs in which the base of the cantilever 101 is damaged during use, while in the case of a mercury type, Both have serious problems such as harmful mercury being scattered if the glass tube 201 were to break, and a solution to these problems is required.

[0008]

[Means for Solving the Problems] The above problem is solved by at least a reed switch 1, a magnet 2 for opening and closing the contacts 10 of the reed switch 1, a spring 3 for elastically displacing the magnet 2, and a case 4. This problem can be solved by an acceleration detector configured so that the magnet 2 is subjected to external acceleration and causes a positional displacement against the elastic force of the spring 3, thereby opening and closing the contact 10 of the reed switch 1.

Specifically, the magnet 2 and the spring 3 are each composed of a ring core magnet and a coil spring each having an air core, and the reed switch 1 is disposed within the air core. A plurality of the reed switches 1 are housed in the case 4 in parallel.

Further, a contact position adjustment mechanism 5 for moving the reed switch 1 along the center line of the air core portion may be provided to adjust the set value of the detected acceleration,
Furthermore, the magnetic body 6 is arranged so that the magnet 2 comes into contact with the initial position, giving a snap action characteristic to the operation of the magnet 2, and the magnetic body 6 is arranged so that the magnet 2 comes into contact with the initial position of the magnet 2. This problem can be effectively solved by providing a latch mechanism 7 on the opposite side and fixing the magnet 2 to the latch mechanism 7 after the contact 10 operates, thereby further enhancing the function.

[0011]

[Operation] According to the present invention, unlike conventional cantilevers, there is no part that is easily damaged, and no harmful substances such as mercury are used, so it is highly reliable and safe. A highly functional acceleration detector can be obtained with this structure.

0012

[Embodiment] Fig. 1 is a diagram showing a first embodiment of the present invention. Fig. 1 (A) is a perspective view (with the case partially removed), Fig. 1 (B) is a sectional view (when not in operation), and Fig. 1 (B) is a perspective view (with part of the case removed). (C) is also a cross-sectional view (during operation)
It is.

In the figure, reference numeral 1 denotes a reed switch, and two leads 11 are sealed in a glass tube to form a contact 10 as shown in the figure. For example, the contact 10 is closed when not in operation.
It is in state F.

Reference numeral 3 denotes a spring, for example a coil spring, one end of which is in contact with or fixed to the case 4. A magnet 2, for example a ring core magnet, is in contact with or fixed to the other end of the coil spring 3, and the opposite side of the magnet 2 to the spring 3 is in removable contact with a stepped portion of the case 4.

In this example, since the magnet 2 and the spring 3 each have a hollow core part, the reed switch 1 can be accommodated loosely in the hollow core part and can be constructed compactly. The case 4 integrates the entire device, and may be made of, for example, a resin molded product.

As shown in Figure (B), when not in operation, the magnet 2 is pressed against the stepped portion of the case 4 by the spring 3 with a force set in a certain initial state, and is separated from the contact 10 of the reed switch 1. position, the contact 10 is OFF.

However, when an external force, for example a leftward external force acceleration, is applied to this, the magnet 2 is displaced to the left while compressing the spring 3, as shown in FIG. The amount of displacement x is expressed by the following formula.

[0018] x=m・a/k−x0 ──────
──────────(1) F=m
・a──────────────────────── (2
) Here, m is the mass of the magnet, a is the acceleration, k is the spring constant, x0 is the length shortened from the free length of the spring 3 to the initial state, and F is the compression of the spring 3 when the magnet 2 receives the acceleration a. This is the spring compression force.

That is, the displacement x of the magnet 2 is proportional to the applied external force acceleration a. Therefore, when the applied acceleration increases and the magnet 2 is displaced to a certain position, for example, a position where the contact 10 operates, the magnetic field generated from the magnet 2 acts on the contact 10 as shown by the dotted line in FIG. When the contact 10 is turned on, for example, if it is extracted as an electric signal by a detection circuit (not shown), an external force acceleration a proportional to the displacement amount x is detected.

In this embodiment, the magnet 2 and the spring 3 are a ring core magnet and a coil spring each having an air core, but the present invention is not limited to these, and magnets and springs of other shapes may also be used. Needless to say.

FIG. 2 is a diagram showing the operating characteristics of the embodiment of the present invention, and is a typical example of the characteristics of the first embodiment. Note that the vertical axis represents the spring compression force F, and the horizontal axis represents the magnet displacement amount x (corresponding to the spring compression amount).

The straight line in the figure illustrates the above equation (1), and the horizontal axis intercept x0 when F=0 is the amount of contraction of the spring 3 in the initial state. xmax is the maximum amount of displacement of the magnet 2, that is, the maximum amount of contraction of the spring 3, and may be set equal to or larger than the position where the contact 10 operates, that is, xON, which will be described later.

Now, when the acceleration a increases, that is, the spring compression force F increases, the displacement x of the magnet 2, that is, the spring compression increases along the straight line in the figure, and a certain displacement xO
N, the contact 10 of the reed switch 1 closes, and the spring compression force FON at that time, that is, the acceleration aON can be detected. Based on this relationship, if the displacement of the magnet 2 is designed to be fixed to a certain xON, it can be operated as a detector for an arbitrary external force acceleration aON.

FIG. 3 is a diagram showing a second embodiment of the present invention. In this example, two reed switches 1a and 1b are arranged in one case 4 to similarly configure an acceleration detector. Therefore, even if one of the reed switches fails, the other reed switch will operate, so the entire system will function normally, and there is an advantage that a highly reliable acceleration detector can be constructed.

FIG. 4 shows a third embodiment of the present invention, in which (a) is a sectional view when the device is not in operation, and (b) is an operating characteristic diagram. In the above embodiments, the operating acceleration value is set to a certain constant value in advance, but in this embodiment, the position of the reed switch 1 can be adjusted along the moving direction of the magnet 2.

For example, as shown in FIG. 4A, contact position adjustment mechanisms 5 are provided at both ends of the case 4 so that the position of the reed switch 1 can be moved left and right and fixed. As such a contact position adjustment mechanism 5, a screw feeding mechanism with the case 4 or the like can be used.

As a result, by adjusting the position of the reed switch 1, that is, the contact point 10 by moving it left and right, the spring compression force FON1, that is, the acceleration aON1, for a certain displacement xON1 as shown in FIG. Also, for a certain displacement xON2, the spring compression force FON2, that is, the acceleration aON2
It operates as a detector for a certain amount of displacement xON3.
For the spring compression force FON3, that is, the acceleration a
A variable setting acceleration detector that operates as an ON3 detector is constructed.

FIG. 5 shows a fourth embodiment of the present invention, in which (a) is a sectional view when the device is not in operation, and (b) is an operating characteristic diagram. In the figure, 6 is a magnetic material, for example, a piece of soft iron, and magnet 2
is fixed to the stepped portion of the case 4 so that it abuts at the initial position.

Note that the same reference numerals are given to the same parts as those explained in the above-mentioned drawings, and the explanation of the same parts will be omitted. In this case, the operating characteristics are slightly different from those of the above embodiments. In other words, as shown in the same figure (b), the broken line (■) is the characteristic when only the spring 3 is used, but a force is required to overcome the attractive force acting between the magnetic body 6 and the magnet 2, and the The force is indicated by the dotted line. Therefore, the spring compression force F required from the outside to compress the spring 3 is as shown by the solid line ``■'' which is the combination of ``■'' and ``■''.

That is, in this case, in order to remove the magnet 2 from its initial position, an initial external force of Fi, which is the initial compression force required when only the spring 3 is used, plus the force FSA to peel the magnet 2 from the magnetic body 6, is required. When the magnet 2 is first operated, a so-called snap action effect, which is the characteristic shown in the drawing, is imparted and stable operation characteristics can be obtained.

FIG. 6 shows a fifth embodiment of the present invention, in which (a) is a sectional view when the device is not in operation, and (b) is an operating characteristic diagram. In the figure, a latch mechanism 7 is made of, for example, a permanent magnet or a soft magnetic material, and is provided on the opposite side of the initial position with the contact 10 of the magnet 2 interposed therebetween.

The operating characteristics in this case are as shown in the same figure (b), the broken line (■) is the characteristic when only the spring 3 is used, but the magnet 2 is displaced due to acceleration and the contact 10 is 0N. From the front and back, the magnet 2 receives an attractive force as indicated by the dotted line 2 by the latch mechanism 7, for example, a permanent magnet. Therefore, the external spring compression force F required to compress the spring 3 is ■ and ■
It looks like the solid line in ■, which is the combination of .

That is, after the contact 10 is turned ON,
Even when the compressive force from the outside is no longer applied, the magnet 2 does not return to its original state, and at the magnet displacement position xL, the contact 10 becomes 0.
The magnet 2 is fixed in the N state, and a so-called latch type acceleration detector can be constructed.

Such a latch-type acceleration detector has the advantage of being able to reduce the load on peripheral circuits depending on how it is used. In addition, when releasing the latch, a magnetic force that cancels the attractive force of, for example, a permanent magnet of the latch mechanism 7 may be applied by, for example, an electromagnetic coil.

In addition to the configuration of this embodiment, it is of course possible to arrange a magnetic body 6 at the initial position of the magnet 2 to give a snap action to the initial movement of the magnet 2 to further improve the functionality. It is.

The above-described embodiments are merely examples, and it goes without saying that other materials, detailed structures, or combinations thereof may be selected and used as long as they do not go against the spirit of the present invention.

[0037]

[Effects of the Invention] As explained above, according to the present invention, unlike the conventional cantilever, there is no easily damaged part.
Furthermore, since no harmful substances such as mercury are used, and the device can be constructed with a simple and safe structure, it greatly contributes to improving the reliability, ease of handling, and functionality of acceleration detectors.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing the operating characteristics of the embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a fifth embodiment of the present invention.

FIG. 7 is a diagram (part 1) showing an example of a conventional acceleration detector.

FIG. 8 is a diagram (part 2) showing an example of a conventional acceleration detector.

[Explanation of symbols]

1 (1a, 1b) is a reed switch, 2 is a magnet, 3 is a spring, 4 is the case, 5 is a contact position adjustment mechanism; 6 is a magnetic material, 7 is a latch mechanism; 10 is a contact point,

Claims (6)

[Claims] Claim 1: A reed switch (1), a magnet (2) for opening and closing a contact (10) of the reed switch (1), a spring (3) for elastically displacing the magnet (2), and a case (4). ), the magnet (2) receives external force acceleration and causes a positional displacement against the elastic force of the spring (3), thereby opening and closing the contact (10) of the reed switch (1). An acceleration detector featuring 2. The magnet (2) and the spring (3) each include a ring core magnet and a coil spring each having an air core portion, and the reed switch (1) is disposed within the air core portion. The acceleration detector according to claim 1, characterized in that: 3. The acceleration detector according to claim 1, wherein a plurality of said reed switches (1) are housed in the case (4) in parallel. 4. A contact position adjustment mechanism (5) for moving the reed switch (1) along the center line of the air core portion.
4. The acceleration detector according to claim 2, further comprising: an acceleration detector. 5. The magnet (6) according to claim 1, wherein the magnetic body (6) is arranged so that the magnet (2) comes into contact with the magnet (2) at an initial position, thereby imparting a snap action characteristic to the operation of the magnet (2). Acceleration detector. [Claim 6] The contact (1) of the reed switch (1)
A latch mechanism (7) is provided on the opposite side of the initial position of the magnet (2) across the magnet (2), and after the contact (10) is operated, the magnet (2) is fixed to the latch mechanism (7). The acceleration detector according to claim 1 or 5, characterized in that: