JP2004325292A - Bidirectional impact acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bidirectional impact acceleration sensor reduced in width and height. <P>SOLUTION: This sensor is provided with a casing 3 having a longitudinal direction substantially parallel to a detection direction of an impact or acceleration, two reed switches 51, 52 arranged in series along the center straight line substantially parallel to the longitudinal direction, an annular magnet 6 arranged slidably along the straight center line, and a spring 7 for energizing the annular magnet 6 along the center straight line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a two-way detection type impact acceleration sensor that detects a two-way impact or acceleration to open and close a switch, and more particularly to an airbag system or a seatbelt pretension mounted on a vehicle such as an automobile. The present invention relates to a two-direction detection type impact acceleration sensor suitable as a switch for activating the human body protection device and as an impact acceleration sensor for industrial use and home appliances.
[0002]
[Prior art]
This type of impact acceleration sensor is used as a switch for activating a personal protective equipment such as an airbag system or a seatbelt pretension, which is an occupant protection device mounted on a vehicle such as an automobile. Also, it is widely used as a sensor for detecting impact / acceleration for industrial use and home appliances.
[0003]
As a conventional impact acceleration sensor, a type using a reed switch 5 as shown in FIG. 4 is widely used. Hereinafter, since the impact acceleration sensor in the conventional example has the same function with respect to impact and acceleration, the impact acceleration sensor will be described as a typical impact sensor.
[0004]
The impact sensor 1 includes a cylindrical shaft 4 disposed on an exterior housing 3 along a direction in which an impact is to be detected, a reed switch 5 inserted in the shaft 4, and a longitudinal direction of the shaft 4. An annular magnet 6 slidably arranged along the axis, a spring 7 for urging the annular magnet 6 against the inner wall end face of the housing 3, and two external connection terminals 2 connected to the reed switch 5. Have been.
[0005]
When an automobile or the like to which the above-described impact sensor 1 is attached is stopped or running normally, a large acceleration (impact) does not act on the impact sensor 1. The shaft 7 is held at a predetermined position by the urging force of the spring 7. At this time, the contacts 5a and 5b of the reed switch 5 are off because they are not closed by the magnetic force of the annular magnet 6.
[0006]
When this state changes and, for example, a strong impact force applied to the vehicle body due to, for example, an accident during driving of a car, or acceleration due to a sudden stop or the like acts in the direction shown by the arrow, the housing is actuated by the urging force of the spring 7 at this point. The annular magnet 6 in contact with the inner wall end face of the body 3 receives a negative acceleration that overcomes the urging force of the spring 7, and the annular magnet 6 relatively receives a force based on its inertial mass and is disposed on the shaft 4. When the magnetic force from the annular magnet 6 reaches a predetermined value or more near the contact of the reed switch, the contacts 5a and 5b of the reed switch 5 are closed and turned on.
[0007]
Next, the annular magnet 6 stops when the spring 7 reaches the position where the spring 7 is completely compressed by the impact force, and the kinetic energy accumulated in the annular magnetic right 6 up to this point is once the spring 7 and the casing 3 It is converted into deformation or vibration energy, and then converted again into kinetic energy of the annular magnet 6 whose direction is reversed.
[0008]
Thereafter, when the acceleration of the annular magnet 6 becomes equal to or less than a predetermined value due to the stop of the vehicle or the like, the urging force of the spring 7 cannot be overcome, and the spring 7 is returned to the original position again. At this time, the magnetic force of the annular magnet 6 acting on the contacts 5a and 5b of the reed switch 5 becomes equal to or less than a predetermined value, and the contacts 5a and 5b of the reed switch 5 are turned off again.
[0009]
The reed switch 5 keeps the contact ON state from the above-described on-conversion to the off-conversion. Incidentally, when used as a switch for activating the protective equipment in an occupant protection device such as an automobile, the driving circuit is configured to drive an electric circuit for operating the protective equipment, and the driving current is supplied to the reed switch 5 in the impact sensor 1. By energizing, the safety control system that detects the energized state is activated, and the airbag or the seat belt pretension is deployed, so that the safety of the occupant of the automobile or the like is secured.
[0010]
Conventionally, in order to detect an impact force from both longitudinal directions, a plurality of impact sensors 1 are provided, or a reed switch 5 is provided inside a large-diameter annular magnet as disclosed in Patent Document 1. The impact force from both longitudinal directions was detected by disposing the two contacts with the positions of the contacts shifted in the parallel direction.
[0011]
[Patent Document 1]
JP 2002-48814 A
[Problems to be solved by the invention]
In the impact sensor 1 having the above-described structure, when detecting acceleration due to an impact force from both longitudinal directions, a plurality of impact sensors are provided, or two reed switches are arranged in a parallel direction. Although the acceleration accompanying the impact force from the longitudinal direction is detected, there is a problem that the size increase is inevitable due to the necessity of an annular magnet having a large inner diameter as described above.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to provide a compact, two-way detection type impact acceleration sensor that is reduced in width and height to solve such a problem.
[0014]
[Means for Solving the Problems]
A two-direction detection type impact acceleration sensor according to the present invention includes a housing having a longitudinal direction substantially parallel to a direction of detecting an impact or acceleration, and two leads arranged in series along a straight line substantially parallel to the longitudinal direction. A switch, an annular magnet slidably disposed along the straight line, and a spring for urging the annular magnet in the straight line direction.
[0015]
Further, a connection point for electrically connecting the two reed switches in series may be connected to a common external terminal.
[0016]
Each terminal of the two reed switches may be independently electrically connected to an external terminal.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an impact acceleration sensor according to the present invention will be described with reference to the drawings. The impact acceleration sensor according to the present invention has the same function for impact and acceleration, and may be referred to as an impact sensor as a representative.
[0018]
FIG. 1 is a partial cross-sectional view showing a two-direction detection type impact acceleration sensor according to an embodiment of the present invention in a state in which no impact is received. FIG. ) Is a view from the front. As shown in FIG. 1, an annular magnet provided at the center along the longitudinal direction of the hollow shaft 41 to detect an impact from both longitudinal directions of the housing 3 extending substantially parallel to the direction for detecting the impact. 6 and springs 7 for biasing the annular magnet 6 are provided on both sides of the annular magnet 6, and two reed switches 51 and 52 are provided in series on both sides with respect to the longitudinal center of the hollow shaft 41. , To reduce width and height.
[0019]
The lead terminals of the reed switches 51 and 52 arranged in series are electrically connected to each other at a contacting portion, and are taken out of the housing as a common external terminal 55. The other terminal of the reed switch 51 is connected to the external terminal 56, and the other terminal of the reed switch 52 is connected to the external terminal 57, forming a two-system switch circuit. This connection is shown in FIG.
[0020]
Further, as shown in FIG. 3B, the four lead terminals of the reed switches 51 and 52 may be independently connected to external terminals. In the following FIG. 2, illustration of the connecting portion and the drawn out common external terminal is omitted.
[0021]
FIG. 2 is a partial cross-sectional view showing a state in which the above-described impact sensor 10 has received an acceleration accompanying an impact force as viewed from above, and FIG. FIG. 2B shows a state in which a shock in the B direction is received. The annular magnet 6 slidably disposed on both sides along the longitudinal direction of the hollow shaft 41 is normally urged by a spring 7 at the center in the longitudinal direction of the hollow shaft 41. For example, when an acceleration due to an impact force is received in the direction A, the contacts 51a and 51b of the reed switch 51 provided in the impact sensor 10 are closed by the magnetic force of the annular magnet 6.
[0022]
When the impact sensor 10 receives an acceleration due to an impact force in a direction B opposite to the direction A, for example, the reed switch 52 provided in the above-described impact sensor 10 causes the contacts 52a and 52b to be turned on by the magnetic force of the annular magnet 6. It becomes a closed state.
[0023]
That is, by supplying a drive current to the reed switches 51 and 52 provided in the shock sensor 10, the contact between the one terminal of the reed switch 51 and the common terminal or the contacts 52a and 52b is established via the contacts 51a and 51b. Through this, a current flows between one terminal of the reed switch 52 and the common terminal, and the direction of the acceleration accompanying the impact can be specified.
[0024]
The impact sensor 10 is configured so that the acceleration accompanying the front impact force applied to the vehicle body due to, for example, an accident at the time of driving of the vehicle is in the direction of arrow A, and the acceleration accompanying the rear impact force due to a rear collision or the like is indicated by an arrow. It can be configured to be in the B direction, and by detecting and controlling the impact / acceleration (front collision, rear collision, sudden stop) in the front-rear direction of an automobile or the like, an airbag, a seatbelt pretensioner, or Active headrests and the like can respond to impacts in two directions, and ensure the safety of occupants such as automobiles.
[0025]
【The invention's effect】
As described above, according to the present invention, by arranging two reed switches in series, compared with a conventional product in which two reed switches are arranged in parallel, a ring magnet having a smaller diameter is used. It is possible to provide a two-direction detection type impact acceleration sensor that can reduce the width and height, and has a high degree of freedom in product design.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a state in which a shock is not applied to a two-direction detection type impact acceleration sensor according to an embodiment of the present invention. FIG. 1A is a view from the top, and FIG. 1B is a view from the front.
FIG. 2 is a partial cross-sectional view showing a state in which a shock is applied to the two-direction detection type impact acceleration sensor according to the embodiment of the present invention; FIG. 2A shows a state in which a shock in the direction A is received, and FIG. 2B shows a state in which a shock in the direction B is received.
FIG. 3 is a diagram showing two switch circuits.
FIG. 4 is a sectional view of a conventional impact sensor.
[Explanation of symbols]
1, 10 Impact sensor 2 External connection terminal 3 Housing 4 Shaft 5, 51, 52 Reed switch 5a, 5b, 51a, 51b, 52a, 52b Contact 6 Annular magnet 7 Spring 41 Hollow shaft 55 Common external terminal 56, 57 External terminal

Claims (3)

A housing having a longitudinal direction substantially parallel to the direction of impact or acceleration detection, two reed switches arranged in series along a straight line substantially parallel to the longitudinal direction, and slidable along the straight line A two-direction detection type impact acceleration sensor, comprising: an annular magnet provided; and a spring for urging the annular magnet in the linear direction. The two-way detection type impact acceleration sensor according to claim 1, wherein a connection point for electrically connecting the two reed switches in series is connected to a common external terminal. The two-direction detection type impact acceleration sensor according to claim 1, wherein each terminal of the two reed switches is electrically connected independently to an external terminal.

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