JP2001324514A - Impact sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that a conventional impact sensor has a large number of part items movement mass such as a spring, a travel space is required in the direction of operation of mass, thereby causing the enlargement of the impact sensor and a structure of a conventional lead switch for approaching magnetism must be changed because the lead switch has high reaction sensitive impact force and reacts by a small impact force. SOLUTION: A permanent magnet 3 is brought close to the lead switch 2 used for approaching magnetism, magnetic bias is given to the lead switch 2, and a magnetic attraction force is overlapped on a travelling force of a movable lead 22 by an impact force to operate the impact sensor by a small impact force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact sensor used as a switch for detecting (sensing) an impact applied to a vehicle body in the event of an accident of an automobile or the like and activating an occupant protection device such as an airbag. Belong to.

[0002]

2. Description of the Related Art As a conventional impact sensor of this type, there is an impact sensor using a magnetic reed switch. As such an impact sensor, for example, Japanese Patent Application Laid-Open No. 08-129 is disclosed.
No. 027 is disclosed.

This shock sensor is configured as shown in FIG. 2. A shock sensor 1 is mounted on a body of an automobile or the like, and is hollow in a case 4 along a direction in which a shock is to be detected. Shaft 8, a magnetic reed switch 2 inserted in the shaft 8, and an annular permanent magnet 3 slidably disposed along the longitudinal direction of the shaft 8.
And a spring 9 for urging the permanent magnet 3 to return to a predetermined position on the shaft 8 at all times.
The two leads 28 and 29 of the magnetic reed switch 2 are connected via a lead wire to a detection circuit of another configuration.

When a vehicle or the like to which the shock sensor 1 is attached is stopped or running normally, the shock sensor 1 does not receive high acceleration (shock). The magnet 3 is held at a predetermined position on the shaft 8 by the compression force of the spring 9. Therefore, the magnetic reed switch 2 has its contacts 28a, 29a
Are not closed by the magnetic force of the permanent magnet 3, and the contact portion is turned off.

[0005] From this state, if a high impact or the like is applied to the vehicle body due to, for example, an accident when driving a car or a sudden stop,
The impact force acts on the impact sensor 1 in the direction indicated by the arrow in FIG.
Receives an operating force greater than the compression force of the spring 9 from the acceleration. Therefore, the annular permanent magnet 3 relatively moves from the position arranged on the shaft 8 based on its inertial mass.

Thus, the annular permanent magnet 3 moves in the opposite direction from the position where it is arranged against the compressive force of the spring 9, and the magnetic force of the annular permanent magnet 3 acting on the contact portion of the magnetic reed switch 2 becomes predetermined. When the size of the magnetic reed switch 2 becomes larger than the value, the contacts 28a and 29a of the magnetic reed switch 2 are turned on by the magnetic force of the annular permanent magnet 3.

[0007] Further, depending on the magnitude of the impact, if the impact is large, the annular permanent magnet 3 continues to move further, and this annular permanent magnet 3 stops when the spring 9 reaches the fully compressed position. The kinetic energy accumulated in the ring-shaped permanent magnet 3 until this time is
And the like, and then converted again into kinetic energy of the annular permanent magnet 3 whose direction is reversed.

Thereafter, when the automobile or the like is stopped, the acceleration of the annular permanent magnet 3 becomes lower than a predetermined value, so that it becomes impossible to resist the tension of the spring 9 and is returned to a predetermined position on the shaft 8 again. At this time, the magnetic force of the annular permanent magnet 3 acting on the contact portion of the magnetic reed switch 2 becomes a predetermined value or less, and the magnetic reed switch 2
a, 29a are again turned off.

The magnetic reed switch 2 is in the contact ON state during the above-described on-conversion to off-conversion.

By energizing the magnetic reed switch, an air bag or the like is deployed, and the safety of the occupant of the automobile or the like can be ensured.

[0011]

In the shock sensor 1 having such a configuration, the number of parts is large, the parts cost is high, and the assembly process is increased due to the complicated structure. Further, since a certain distance is required to move the permanent magnet 3, there is a problem that the size of the permanent magnet 3 is increased in the operation axis direction.

In response to the increase in the size of the impact sensor, development of a small impact sensor has been promoted. However, in a reed switch used for magnetic proximity, the rigidity of the movable piece is high, and the reed switch has a high rigidity. If this is used as it is, it will not operate unless a large shock is applied, resulting in a shock sensor with poor sensitivity. To solve this problem, an impact sensor disclosed in Japanese Patent Application Laid-Open No. H11-2642 was invented, but this impact sensor had a problem that the internal structure of a reed switch became complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a shock sensor having a small size, high sensitivity, and a simple structure that can use a magnetic proximity reed switch as it is in order to solve the above-mentioned problems.

[0014]

According to the first aspect of the present invention, there is provided a reed switch and a permanent magnet, wherein the reed switch is made of a magnetic material and has a fixed lead at one end, and a magnetic material. A movable lead having a movable contact at one end, the fixed contact and the movable contact facing each other at intervals along the shock detection direction so as to be able to freely contact and separate from each other, and the other end of the fixed lead and the movable lead. Has an insulating tube enclosing the fixed lead and the movable lead in a state where the movable lead is pulled out, and the permanent magnet moves toward the fixed lead when the movable lead receives an impact.
An impact sensor is provided, wherein the impact sensor is provided as a closing assist device for assisting closing between the fixed lead and the movable lead, in addition to the reed switch.

According to the second aspect of the present invention, there is provided the impact sensor according to the first aspect, wherein the permanent magnet is mounted on at least one of the fixed lead and the movable lead. .

According to the third aspect of the present invention, there is provided the impact sensor according to the first or second aspect, wherein the permanent magnet is provided along with the reed switch so that the position of the permanent magnet can be adjusted. .

According to the fourth aspect of the present invention, the permanent magnet is interchangeably provided with the reed switch, and the permanent magnet is interchangeably provided with the reed switch. Is obtained.

According to a fifth aspect of the present invention, in the impact sensor according to any one of the first to fourth aspects, the reed switch is covered by a magnetic material case. can get.

According to a sixth aspect of the present invention, in the impact sensor according to any one of the first to fifth aspects, the reed switch is housed in a resin mold. can get.

According to the present invention, the other ends of the fixed lead and the movable lead are terminals for surface mounting. The impact sensor described in the item is obtained.

[0021]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an impact sensor according to an embodiment of the present invention.
(B) is a sectional view of a main part.

Referring to FIG. 1, an impact sensor 1 according to the present embodiment includes a reed switch (impact detection element) 2, a permanent magnet 3, and a magnetic case 4.

The reed switch 2 further includes a fixed lead 21
, A movable lead 22, and a glass tube 23. The fixed lead 21 is made of a magnetic material, and has a fixed contact 21 at one end.
a. Similarly, the movable lead 22 is made of a magnetic material and has a movable contact 22a at one end. The glass tube 23 is an example of an insulating tube, and encloses the fixed lead 21 and the movable lead 22. The sealing of the fixed lead 21 and the movable lead 22 by the glass tube 23
a and the movable contact 22a oppose each other at intervals along the impact detection direction (the direction of the arrow in FIG. 1) so that the fixed lead 21 and the movable lead 22 are pulled out. Made up of

The permanent magnet 3 is connected to the contact 22 of the movable lead 22.
The reed switch 2 is provided along with the reed switch 2 as a closing assist device for assisting the closing between the fixed reed 21 and the movable reed 22 when a is moved toward the fixed contact 21a of the fixed reed 21 due to the impact. That is, the permanent magnet 3 always urges the movable lead 22 toward the fixed lead 21 by magnetic force in order to improve the sensitivity. In the present embodiment, the permanent magnet 3
Is mounted on the other end of the fixed lead 21 such that its arrangement position is adjustable and the permanent magnet 3 is exchangeable.

The magnetic case 4 is cylindrical and houses the reed switch 2 and the permanent magnet 3. Instead of the magnetic case 4, the reed switch 2 and the permanent magnet 3
May be stored in a resin mold.

The above-mentioned sealing portions 23a, 23 of the glass tube 23
The fixed lead 21 and the movable lead 22 protruding from “b” are connected as contact signal terminals. These leads 21 and 2
2 is drawn out in an arbitrary direction such as a longitudinal direction of the reed switch 2 or a direction perpendicular to the longitudinal direction, and is used for connection to a circuit board (not shown). And is electrically and mechanically connected to the circuit board at this terminal portion. The material and shape of the permanent magnet 3 can be selected according to the strength of the magnetic field applied to the reed switch 2. Further, the shape of the permanent magnet 3 can be arbitrarily selected, such as a square shape, a rectangular shape, or a ring shape.

Next, the operation of the shock sensor 1 of the present embodiment will be described. For example, when an automobile or the like is suddenly stopped from moving in the direction indicated by the arrow in FIG. 1 and an impact acts on the impact sensor 1, the movable lead 22 relatively moves in the direction indicated by the arrow. Subject to large negative acceleration. Therefore, the movable contact 22 at the tip of the movable lead 22
a contacts the fixed contact 21 a at the tip of the fixed lead 21. Thereby, the fixed lead 21 and the movable lead 22
The interval is closed and turned on. In this ON state, when the automobile or the like is completely stopped thereafter, the negative acceleration in the movable lead 22 is released, the state is returned to the initial state, and the contacts 21a and 22a are opened.

By changing the relative positions of the permanent magnet 3 and the reed switch 2, different magnetic fields can be applied to the reed switch 2. The magnetic attraction is generated between the movable lead 22 and the fixed lead 21 according to the strength of the magnetic field generated by the permanent magnet 3. In the same manner as the operation sensitivity adjustment of the polarized type relay using the permanent magnet used in the communication circuit, the operation point of the permanent magnet is adjusted by adjusting the magnetic force applied to the magnetic body of the switching element. When the magnetic force applied to the reed switch from the permanent magnet is increased, a magnetic force is generated in both the fixed lead and the movable lead, and a force is generated in a direction in which the leads are attracted to each other. Further, when the magnetic force is increased, both leads come into contact and the contacts close. The adjustment of the magnetic force can be arbitrarily obtained by selecting the strength of the magnetic force of the permanent magnet or the relative positional relationship between the permanent magnet and the reed switch.

When an impact is applied to the impact sensor 1, a force is generated so that the movable lead 22 moves in the direction of the fixed lead 21. If the combined force of the magnetic attraction force due to the magnetic field and the force generated by the impact becomes larger than the rigidity of the movable lead 22, the movable contact 22a provided at the tip of the movable lead 22 Abuts on the fixed contact 21a provided at the first position. That is, by changing the magnetic force applied to the reed switch 2 by the permanent magnet 3, the magnitude of the impact to be detected can be changed. On the other hand, when the force generated by the impact disappears, the movable contact 22a provided at the tip of the movable lead 22 due to the rigidity of the movable lead 22 becomes:
The fixed lead 21 is dissociated from the fixed contact 21a.

[0030]

According to the present invention, a magnetic proximity reed switch can be used as it is, and a compact, high-sensitivity, and simple shock sensor can be provided.

When the shock sensor of the present invention is mounted on a safety device of an automobile or the like, for example, when the shock sensor of the present invention is suddenly stopped, the movable contact of the movable lead is replaced with the fixed contact of the fixed lead 21. This function makes it possible to reliably operate a system such as a safety control device mounted on an automobile or the like.

The conventional impact sensor is generally mounted on a safety device or the like of an automobile or the like, and the present invention does not impair its conventional functions and has features such as a miniaturized shape. By detecting impact when transporting precision equipment, etc., it has become possible to also have an impact diagnosis function.

[Brief description of the drawings]

FIG. 1 shows an impact sensor according to an embodiment of the present invention,
(A) is an overall cross-sectional view, and (b) is a cross-sectional view of a main part.

FIG. 2 is a schematic sectional view showing an example of a conventional impact sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impact sensor 2 Reed switch 21 Fixed lead 21a Fixed contact 22 Movable lead 22a Movable contact 23 Glass tube (insulating tube) 23a Sealing part 23b Sealing part 3 Permanent magnet 4 Magnetic case

Claims (7)

[Claims] A reed switch and a permanent magnet;
The reed switch includes a fixed lead made of a magnetic material and having a fixed contact at one end, a movable lead made of a magnetic material and having a movable contact at one end, and an interval between the fixed contact and the movable contact along an impact detection direction. The permanent magnet has an insulating tube that is open and opposed to be able to freely contact and separate, and encloses the fixed lead and the movable lead in a state where the other ends of the fixed lead and the movable lead are pulled out. When the movable lead is moved toward the fixed lead by receiving an impact, the movable lead is provided along with the reed switch as a closing assist device that assists closing of the fixed lead and the movable lead. Shock sensor. 2. The shock sensor according to claim 1, wherein the permanent magnet is mounted on at least one of the fixed lead and the movable lead. 3. The impact sensor according to claim 1, wherein the permanent magnet is provided along with the reed switch so that the position of the permanent magnet can be adjusted. 4. The impact sensor according to claim 1, wherein the permanent magnet is interchangeably provided with the reed switch. 5. The impact sensor according to claim 1, wherein the reed switch is covered by a magnetic case. 6. The impact sensor according to claim 1, wherein the reed switch is housed in a resin mold. 7. The shock sensor according to claim 1, wherein the other ends of the fixed lead and the movable lead are terminals for surface mounting.