JPH0943265A - Impact sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impact sensor capable of being effectively operated without shortening an ON time even if a magnet collides with the inner wall of a switch case. SOLUTION: The impact sensor comprises a magnetic reed switch 13 disposed along the direction to detect an impact, and a moving member 14 having a magnet movably supported along the longitudinal direction of the switch and energized toward one side by a coiled spring 15. The spring is engaged with the small-diameter part 14a provided at the outer surface of the end side of the moving member, and brought into contact with the end face 14b of the small-diameter part to thereby energize the moving member, and the end face 14c of the moving member at the spring side is so formed as to protrude at one point. A small-diameter part 14d is also provided at the base end side of the moving member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact using a magnetic reed switch for detecting an impact applied to a vehicle body and activating an airbag or seat belt system in the case of an accident such as an automobile. It relates to a sensor.

[0002]

2. Description of the Related Art Conventionally, as such an impact sensor,
For example, an impact sensor using a magnetic reed switch is often used, and is configured as shown in FIG. 3, for example. That is, the impact sensor 1 is arranged so as to extend along the case 2 that can be attached to the vehicle body of an automobile, and the direction in which the impact should be detected (for example, the front-back direction of the automobile). A hollow cylindrical switch case 3, a magnetic reed switch 4 inserted in the switch case 3, an annular magnet 5 slidably inserted along the longitudinal direction of the switch case 3, It is composed of a coil spring 6 that biases the magnet 5 to the right in the drawing. The two connection terminals of the magnetic reed switch 4 are connected to a detection circuit having an appropriate configuration via lead wires (not shown).

According to the impact sensor 1 thus constructed, the impact sensor 1 can be used when the automobile or the like to which the impact sensor 1 is attached is stopped or is traveling normally. Does not have very high acceleration, so
The magnet 5 is brought into contact with a stopper 3 a provided at the right end of the switch case 3 by the tension of the coil spring 6. Therefore, the magnet 5 is relatively separated from the magnetic reed switch 4 inserted in the switch case 3. Therefore, the magnetic reed switch 4 is in the off state because its contact portion is not affected by the magnetic force of the magnet 5.

From this state, for example, while the automobile is running,
When a shock is applied, such as when the shock sensor 1 suddenly stops due to an accident or the like, the shock sensor 1 is suddenly stopped from the state of moving to the left as shown by an arrow A in the drawing. The magnet 5 receives a relatively large negative acceleration. Therefore, this magnet 5 receives an inertial force relatively leftward with respect to the switch case 3 based on its inertial mass.

Thus, the magnet 5 moves the switch case 3 to the left against the tension of the coil spring 6, and the magnetic force of the magnet 5 acting on the contact portion of the magnetic reed switch 4 becomes a predetermined value or more. When this magnetic reed switch 4
Is turned on by the magnetic force of the magnet 5.

After that, when the automobile or the like stops and the acceleration of the magnet 5 becomes equal to or less than a predetermined value, the magnet 5 causes the coil spring 6 to move.
The tension of the coil spring 6 cannot be resisted, and the coil spring 6 moves to the right of the switch case 3 and returns to the initial position again. At this time, when the magnetic force of the magnet 5 acting on the contact portion of the magnetic reed switch 4 becomes a predetermined value or less, the magnetic reed switch 4
Has its contact turned off.

In this way, the magnetic reed switch 4
Means that the ON state continues only during the above-mentioned ON-to-OFF switching, and this ON-state is detected by the connected detection circuit, and the airbag or seat belt system is activated to activate the automobile. The safety of passengers will be secured.

However, in the shock sensor 1 having such a structure, when the applied shock is excessively large, the magnet 5 moves to the left region of the switch case 3 at a high speed, and the switch of the magnet 5 is switched. Since the case 3 is also quickly returned to the right, the duration of the ON state of the magnetic reed switch 4 is extremely short. For this reason,
The detection signal from the detection circuit becomes very short, and in some cases, the control device of the airbag and seat belt system cannot recognize the detection signal.

When the coil spring 6 is further compressed in a completely compressed state, the coil spring 6 tends to be deformed in the radial direction, but the coil spring 6 includes the switch case 3 and the magnet 5.
Since the play on the side surface of the is relatively small and the radial deformation is suppressed, the radial deformation occurs only in the case of a considerably strong compression, and the on-time varies.

In order to solve such a problem, the inventors of the present invention have disclosed in Japanese Utility Model Laid-Open No. 6-56771 that the structure is simple and that the shock can be surely detected even when the shock is excessive, and the on-time is reduced. We have proposed an impact sensor that is as long as possible and that does not cause variations.

According to this, as shown in FIG. 4, the impact sensor 7 has a small diameter portion 5a by forming the outer peripheral surface of the right side portion in the drawing on the tip side of the magnet 5 to have a smaller diameter than the left portion, The coil spring 6 is fitted in the small diameter portion 5a, and one end of the coil spring 6 is brought into contact with the end surface 5b of the small diameter portion 5a.
Is biased to the left.

[0012]

However, in the shock sensor 7 having such a structure, when a strong acceleration is applied, the coil spring 6 is completely compressed against the inner wall of the switch case 3 and then the magnet. Since the coil spring is further deformed in the radial direction by the pressing force of 5, the compression height of the coil spring 6 becomes smaller than the winding number times the wire diameter of the coil spring 6, and the magnet 5 directly collides with the inner wall of the switch case 3. I may end up doing it.

At this time, the end surface of the magnet 5 facing the inner wall of the switch case 3 collides with the inner wall of the switch case 3 over its entire surface, and at the same time, the magnet 5 moves in a direction opposite to the traveling direction from the inner wall. There was a problem that it would be bounced back and the on-time would rather be shortened.

On the other hand, if the compression height of the coil spring 6 is set sufficiently large so that the end surface of the magnet 5 does not collide with the inner wall of the switch case 3, the on-time can be maintained for a long time. When the sensor 7 is downsized, increasing the compression height of the coil spring 6 shortens the moving distance of the magnet 5, which is the maximum factor that determines the on-time. Therefore, the on-time is rather shortened.

In view of the above points, it is an object of the present invention to provide an impact sensor capable of reliably operating without shortening the on-time even when the magnet collides with the inner wall of the switch case. There is.

[0016]

In order to achieve the above object, according to the present invention, a magnetic reed switch arranged along a direction in which an impact should be detected and a magnetic reed switch movable along the longitudinal direction of the magnetic reed switch. A moving member provided with a magnet that is supported by and is biased toward one side by a coil spring, wherein the coil spring is fitted to a small-diameter portion provided on an outer surface of the moving member distal end side, In the impact sensor that urges the moving member by contacting the end surface of the small diameter portion, the end surface of the moving member on the coil spring side is formed so as to project at one point by the convex portion or the inclined surface. ing. In addition to the above configuration, a small diameter portion may be formed on the outer surface of the moving member on the base end side.

According to this structure, when the impact sensor is mounted on the vehicle body of an automobile, for example, when the automobile suddenly stops, the moving member moves against the tension of the coil spring due to the inertial mass of the magnet. The moving direction is reversed at the position where the coil spring is completely compressed, and when the acceleration acting on the moving member becomes equal to or less than a predetermined value, the coil spring is returned to the original position based on the tension of the coil spring.

Here, when a strong acceleration is applied to the moving member, the moving member completely compresses the coil spring and then further presses it. In this case, the end surface of the moving member on the coil spring side is at one point. Since it contacts the inner surface of the case,
After that, the moving member turns around this contact point. Here, if the small diameter portion is formed on the base end side of the moving member, the base end does not come into contact with the inner surface of the case even if the contact of the base end side increases due to the turning of the moving member. Therefore, a sufficiently large turning angle of the moving member can be secured.

Therefore, due to the turning of the moving member, the moving member is not immediately rebounded by the reaction force in the opposite direction, and the ON time of the switch can be maintained for a long time. As a result, the detection signal can be reliably recognized by the control device of the airbag and seat belt system. Further, since the above-described structure is a simple structure in which the shape of the moving member is changed as compared with the conventional impact sensor, it is manufactured at a relatively low cost.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 shows an embodiment of a shock sensor according to the present invention. The impact sensor 10 includes a case 11 that can be attached to a vehicle body of an automobile, and a direction in which an impact should be detected (for example, a case 11).
A hollow cylindrical switch case 12 arranged so as to extend along the front-rear direction of the vehicle, and a magnetic reed switch 13 inserted in a right region of the switch case 12.
And an annular magnet 14 slidably fitted along the longitudinal direction of the switch case 12, and a coil spring 15 for biasing the magnet 14 to the left in the drawing. When mounting the impact sensor 10 on the vehicle body, as shown in FIG.
On the right side is the front of the vehicle.

Although the magnet 14 is configured so as to also serve as a moving member in the case of the drawing, it is a separate annular moving member which is slidably inserted along the longitudinal direction of the switch case 12. It may be attached to the member. The two connection terminals of the magnetic reed switch 13 are connected to a detection circuit having an appropriate configuration via lead wires (not shown).

Here, the magnet 14 is the switch case 12
It is loosely fitted so as to have a gap G with respect to the outer side surface thereof, and is provided with a small diameter portion 14a provided on the tip side thereof, that is, on the outer peripheral surface of the right side portion in FIG. The coil spring 15 is fitted in the small diameter portion 14a on the tip side, and one end of the coil spring 15 has a small diameter portion 14a.
It is in contact with the end surface 14b of a. This allows the magnet 14 to be biased to the left.

Further, an end face 12a projecting outward in a flange shape from the right end of the switch case 12 with which the other end of the coil spring 15 abuts is provided with a convex portion 12b which is bent leftward on the outer side in the radial direction. Is formed. As a result, the other end of the coil spring 15 is surrounded by the protrusion 12b from the outside in the radial direction.

The above-described structure is similar to the shock sensor 1 of FIG. 4, but the shock sensor 10 according to the embodiment of the present invention is used.
Is the end surface 14c of the magnet 14 on the coil spring side.
Is obliquely formed so that the upper edge thereof projects to the rightmost in the drawing.

The impact sensor 10 according to the present invention is constructed as described above, and when an automobile or the like equipped with the impact sensor 10 is stationary or is traveling normally (in FIG. 1, the automobile is an automobile). Will drive to the right.)
Since a very high acceleration does not act on the impact sensor 10, the magnet 14 is in contact with the stopper 12c provided at the left end of the switch case 12 due to the tension of the coil spring 15. Therefore, the magnet 14 is relatively distant from the magnetic reed switch 13 inserted in the right region of the switch case 12. Therefore, the magnetic reed switch 13 is in the off state because its contact portion is not affected by the magnetic force.

From this state, for example, while the automobile is running,
When an impact is applied, such as when the vehicle suddenly stops due to an accident or the like, the impact sensor 10 moves from the state in which it is moving to the right as shown by an arrow A in the drawing. Because it can be stopped suddenly, this magnet 1
4 receives a relatively large negative acceleration. Therefore, the magnet 14 receives an inertial force relatively to the right with respect to the switch case 12 based on the inertial mass of the magnet 14.

In this way, the magnet 14 has a coil spring 15
Move the switch case 12 to the right against the tension of
When the magnetic reed switch 13 approaches the contact portion of the magnetic reed switch 13 and the magnetic force of the magnet 14 acting on the contact portion reaches a predetermined value or more, the magnetic reed switch 13 is turned on by the magnetic force of the magnet 14. It can be changed.

After that, when the automobile or the like stops,
When the acceleration of the magnet 14 becomes less than a predetermined value, the tension of the coil spring 15 cannot be resisted, and the tension of the coil spring 15 causes the switch case 12 to move to the left side, and then again. Returned to the position.
At this time, when the magnetic force of the magnet 14 acting on the contact portion of the magnetic reed switch 13 becomes equal to or smaller than a predetermined value, the contact portion of the magnetic reed switch 13 is turned off.

Thus, the magnetic reed switch 13 continues to be in the on state only during the above-mentioned on-switching and off-switching, and this on-state is detected by the connected detection circuit, and the air bag and The seat belt system can be activated to ensure the safety of the vehicle occupants.

At this time, a small diameter portion 14a is formed on the magnet 14 as a moving member, and the coil spring 1 is formed on the small diameter portion 14a.
5 is fitted, the end face 12 of the switch case 12
By combining with the convex portion 12b of a, the moving stroke can be lengthened without reducing the moving distance of the magnet 14, and the ON time can be held relatively long.

Here, when the impact applied to the impact sensor 10 is strong, the magnet 14 further presses the coil spring 15 after completely compressing it. In this case,
Since the end surface 14c of the magnet 14 on the coil spring side is inclined and the upper edge is projected, the end surface 14c of the switch case 12 is first contacted with the protruding upper edge at only one point. Become. And further magnet 14
Is swung around this contact point, and then the magnet 14 also makes contact with the retracted lower edge of the end surface 14c on the coil spring side. In this state, the entire moving member descends to the left in FIG. It will be inclined at the angle.

In this case, the magnet 14 is presumed to behave as follows. That is, the magnet 14 turns by the amount of the gap G between the inner surface of the magnet 14 and the outer surface of the switch case 12, and thus the inner surface (that is, the magnet 14 in FIG. 1).
The inner surface of the base end portion on the left side of) contacts the outer surface of the switch case 12. At this time, the magnet 14 is turned in the opposite direction by the reaction force from the outer surface of the switch case 12. Then, by the turning in the opposite direction, the inner surface of the magnet 14 again contacts the outer surface of the switch case 12, and the magnet 14 is swung in the same direction as the first turning by the reaction force from the outer surface of the switch case 12. It Then, the magnet 14 repeats such turning while being in contact with the end surface 12a of the switch case 12. Thus, the magnet 14
Due to the turning, the end face 12a of the switch case 12 does not immediately bounce back in the opposite direction due to the reaction force, so that the on time of the reed switch 13 can be held for a long time.

Further, in the embodiment shown in FIG. 1, the small diameter portion 14d is formed by cutting out the outer peripheral surface of the base end side of the moving member (magnet) 14, that is, the left side portion in FIG. Due to the small-diameter portion 14d, even if the movement of the moving member 14 increases the contact on the base end side, the outer periphery on the base end side does not contact the inner surface of the case 11, and therefore the turning angle of the moving member 14 is increased. Can be secured large enough.

In the above embodiment, the impact sensor 10
Is formed such that the end surface 14c of the magnet 14 on the coil spring 15 side is obliquely inclined, but the invention is not limited to this.
4, the end surface of the coil spring side is the switch case 12
When contacting the end face 12a of the contact point 12a at only one point, as shown in FIG. 2, for example, a protruding portion 14e having a spherical outer surface in the radial direction, preferably the tip is formed spherically, is formed.
Obviously, it may be provided. Even in this embodiment, the small diameter portion 1 is provided on the base end side of the magnet 14 shown in FIG.
It is of course possible to provide 4d, and in this case as well, the same excellent effects as those of the embodiment of FIG. 1 can be exhibited.

[0035]

As described above, when the impact sensor according to the present invention is mounted on an automobile, when the automobile suddenly stops and a strong acceleration is applied to the moving member, the moving member completely compresses the coil spring. After that, further pressing is performed, but in this case, the end surface of the moving member on the coil spring side comes into contact with the inner surface of the case at one point, and thereafter, the moving member turns around this contact point.

Therefore, due to the turning of the moving member, the moving member is not immediately rebounded in the opposite direction by the reaction force, and the on-time of the switch can be maintained for a long time. As a result, the detection signal is surely recognized by the control device of the airbag and seat belt system. Further, the above-mentioned configuration is
Since it has a simple configuration in which the shape of the moving member is changed, it can be manufactured at a relatively low cost.

Thus, according to the present invention, there is provided an extremely excellent impact sensor capable of reliably operating without the ON time being shortened even when the moving member collides with the inner wall of the switch case. .

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of an impact sensor according to the present invention.

FIG. 2 is a partial cross-sectional view showing a modified example of a magnet in the impact sensor of FIG.

FIG. 3 is a schematic cross-sectional view showing an example of a conventional impact sensor.

FIG. 4 is a schematic cross-sectional view showing another example of a conventional impact sensor.

[Explanation of symbols]

 10 Impact Sensor 11 Case 12 Switch Case 12a End Surface 12b Convex Part 12c Stopper 13 Magnetic Reed Switch 14 Moving Member (Magnet) 14a Small Diameter Part on Tip Side of Moving Member 14b Small Diameter End Face 14c Moving Member End Face 14d Moving Member Base End Side small diameter part 14e convex part 15 coil spring

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yuji Tsuda 1-25-252 Komaoka, Tsurumi-ku, Yokohama-shi, Kanagawa Japan Aleph Co., Ltd. (72) Inventor Hirohiro Iwaki 1-28, Komaoka, Tsurumi-ku, Yokohama-shi, Kanagawa No. 52 within Nippon Aleph Co., Ltd.

Claims (5)

[Claims] 1. A magnetic reed switch disposed along a direction in which an impact should be detected, and a magnetic reed switch movably supported along the longitudinal direction of the magnetic reed switch and biased toward one side by a coil spring. A moving member having a magnet, the coil spring is fitted to a small diameter portion provided on an outer surface of the moving member, and urges the moving member by contacting an end surface of the small diameter portion. In the impact sensor configured as described above, the end surface on the coil spring side of the moving member is formed so as to project at one point. 2. An end surface of the moving member on the coil spring side is
The impact sensor according to claim 1, wherein the impact sensor is formed to be inclined. 3. An end surface of the moving member on the coil spring side is
The impact sensor according to claim 1, further comprising a convex portion on one side. 4. The impact sensor according to claim 1, wherein a small diameter portion is formed by cutting out an outer surface on the base end side of the moving member. 5. The shock sensor according to claim 1, wherein the moving member is loosely fitted to the outer surface of the switch case so as to have a gap.