JPH05258650A - Impact sensor - Google Patents

Abstract

PURPOSE:To extend the ON time of a reed switch in an impact sensor in which the reed switch, a magnet and a compression spring are sealed in a housing. CONSTITUTION:In a sensor formed of a reed switch 10 extending through the cavity 9 of a housing 5; a magnet 20 fitted onto the reed switch 10 in such a manner as to be capable of sliding; and a compression spring 3 for energizing the magnet 20 in the direction of one end part of the reed switch 10, wherein the magnet 20 is moved forward against the elasticity of the compression coil spring 3 by the addition of an impact to turn on the reed switch 10, a liquid L is charged in a cavity 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact sensor in which a reed switch penetrating a cavity of a housing, a magnet externally fitted to the reed switch, and a compression coil spring for urging the magnet in a predetermined direction are enclosed in a housing. Regarding

The impact sensor as described above is widely used to detect the fall of a device to be carried, to detect G greater than a predetermined value due to a collision of an automobile, and the like.

[0003]

2. Description of the Related Art FIG. 6 is a sectional view of a conventional example, and FIG. 7 is a diagram for explaining the operation of an impact sensor. In FIG. 6, reference numeral 10 denotes a pair of lead pieces 11-1, 11-2 which are inserted and sealed from both ends of an elongated sealing tube (for example, a glass tube) 13 so that both lead pieces 11-1, 11- The tip of 2 is almost the center of the sealing tube 13,
It is a reed switch incorporated so that it overlaps with a gap.

In the illustrated example, the reed switch 10 is inserted into a protective cylinder 14 made of synthetic resin or the like to prevent damage to the sealing tube 13. Reference numeral 2 is a ring-shaped magnet that is slidably fitted onto the reed switch 10.

Reference numeral 5 is a substantially rectangular parallelepiped housing made of synthetic resin or the like, in which a cylindrical cavity 9 is formed in the axial center by fitting a lid 5A on the opening side. After fitting the magnet 2 and the compression coil spring 3 into the reed switch 10, the magnet 2 is placed on the selected cavity end face 6 side, and the reed switch 10 is housed and fixed in the housing 5 so as to penetrate the axis of the cavity 9. ing.

Since the reed switch 10, the magnet 2 and the compression coil spring 3 are assembled as described above, one end of the compression coil spring 3 is seated on the forward end face 2A of the magnet 2 and the other end thereof is seated. Is seated on the cavity end face opposite to the cavity end face 6.

Therefore, the magnet 2 is biased by the compression coil spring 3, and its retracted end face 2B is always in contact with the cavity end face 6. A stopper 7 is provided at a predetermined position on the inner wall of the cavity 9 to prevent the magnet 2 from moving forward excessively.

Further, the tips of the pair of terminals 12-1, 12-2 provided so as to penetrate the bottom plate of the housing 5 are connected to the ends of the corresponding lead pieces 11-1, 11-2, and a cavity is further formed. A lid 5A is fitted in the opening of the plate 9.

The shock sensor assembled and constructed as described above is used by being mounted on a shocked object. When the object to be impacted is a moving body, the axial center of the reed switch 10 and the moving direction of the moving body are aligned with each other, and the compression coil spring 3 is in the moving direction of the moving body with respect to the magnet 2. ,
The impact sensor shall be mounted on the moving body.

Now, the impacted object from the direction shown by the arrow
When an impact force P larger than a predetermined value is received, the magnet 2 moves forward (leftward in the figure) against the elastic force of the compression coil spring 3,
The forward end face 2A of the magnet 2 contacts the stopper 7 and the forward movement of the magnet 2 is stopped.

The forward stop position is a position where the magnet 2 does not pass through the joint portion between the two lead pieces. When the magnet 2 moves forward to some extent, the magnetic force of the magnet 2 causes the lead pieces 11-1,1 to move.
The lead switches 10 are turned on because the tip portions of both lead pieces come into close contact with each other by acting on 1-2. Then, this ON operation continues even after the magnet 2 reaches the position of the stopper 7.

As described above, the stopper 7 prevents the magnet 2 from excessively moving forward, so that the magnet 2 is stopped within the range where the magnetic force acts on the joint portion of the lead pieces. Therefore, the ON state of the reed switch 10 is maintained until the magnet 2 retracts to a predetermined position.

Therefore, by recording the output of the reed switch 10 or the like, it can be detected that an impact force P greater than a predetermined value is applied to the impacted object. On the other hand, when the advancement of the magnet 2 is blocked by the stopper 7, the magnet 2 immediately begins to retreat due to the repulsive force of the compression coil spring 3, and retracts until the retracted end face 2B of the magnet 2 comes into contact with the cavity end face 6.

The relationship between the on-time T of the reed switch 10, that is, the sensor output S and the impact force P is shown in FIG. FIG. 7 shows that the reed switch 10 is turned on slightly after the moment when the impact is applied, remains in the on state even after the impact ends, and turns off when the magnet retracts to a certain position. ing.

[0015]

By the way, the explosive expansion of the air bag of an automobile is activated when a plurality of impact sensors are combined with an AND circuit and G of a predetermined value or more is applied and both sensors are turned on. Is configured.

Therefore, the impact sensor used in this way is required to have a long reed switch on-time. However, in the above-mentioned impact sensor, as soon as the magnet advances and the stopper prevents the advance, the magnet retracts due to the repulsive force of the compression coil spring. Therefore, there is a problem that the on time of the reed switch, that is, the output time of the sensor is short.

The present invention has been made in view of the above points, and an object thereof is to provide an impact sensor having a long reed switch ON time.

[0018]

To achieve the above object, the present invention is directed to a reed switch 10 penetrating a cavity 9 of a housing 5, a magnet 20 slidably fitted on the reed switch 10, and a reed switch. 10 magnets towards one end
In the sensor which is composed of the compression coil spring 3 for urging the coil 20, the magnet 20 moves forward against the elastic force of the compression coil spring 3 when an impact is applied, and the reed switch 10 is turned on. As shown in FIG. 3, the cavity 9 is filled with the liquid L.

Further, as illustrated in FIG. 3, a bypass 40 which connects both ends of the cavity 9 is provided. The check valve 41 is attached to the opening of the bypass 40 on the end side of the cavity 9 opposite to the compression coil spring 3.

Alternatively, as illustrated in FIG. 4, a hole 30 is provided in the magnet 20 so as to be parallel to the axis. A check valve 31 is attached to the opening of the hole 30 on the side opposite to the compression coil spring 3.

Further, as illustrated in FIG. 5, the magnet 200 is not a ring-shaped magnet but a truncated cone-shaped magnet 200 having a small diameter on the compression coil spring 3 side.

[0022]

The outer diameter of the magnet according to the first aspect of the invention is desirably smaller than the inner diameter of the cavity.

With such a configuration, when the shock sensor receives a shock and the magnet advances, the liquid filled on the compression coil spring side of the cavity passes through the outside of the magnet, and the liquid on the back side (retraction side) of the magnet. ) Flow into.

Therefore, when the magnet retreats, the liquid filling the back side slows down the retreating speed of the magnet. Due to this, the time during which the magnetic force of the magnet acts on the reed pieces becomes long, and the on-time of the reed switch becomes long accordingly.

According to the second aspect of the invention, when the impacted object receives an impact and the magnet advances, the liquid filled on the compression coil spring side of the cavity passes through the bypass to the back side (retraction side) of the magnet. Pour in.

When the magnet starts to move backward by the compression coil spring, the liquid flowing into the back side of the magnet flows backward through the bypass and flows toward the compression coil spring side of the cavity. At this time, however, the check valve closes and backflow is blocked, so the compression coil spring side of the cavity (that is, the cavity in the forward direction)
Becomes negative pressure. Therefore, the liquid retreats at a slower speed of the magnet, the time during which the magnetic force acts on the reed pieces becomes longer, and the on time of the reed switch becomes longer.

In the invention of claim 3 also, the check valve is claim 2.
Since the operation is almost the same as that of the invention, the on time of the reed switch becomes long. The magnet of the invention of claim 4 is a truncated cone shape having an outer diameter dimension smaller than the inner diameter dimension of the cavity and a sufficiently small compression coil spring side (advancing side end surface side).

Therefore, when the impacted object receives an impact and the magnet advances, the liquid filled on the compression coil spring side of the cavity flows in the outer peripheral direction along the inclined surface of the magnet, and passes through the outside of the magnet to pass through the magnet. Flows into the back side of.

At this time, since the magnet has a truncated cone shape, the flow of the liquid is hardly obstructed. Therefore, the advancing speed of the magnet is hardly reduced, and the start time when the reed switch is turned on is not delayed.

On the other hand, when the magnet is retracted by the compression coil spring, the liquid filling the back side of the magnet slows down the retreat speed of the magnet as in the first aspect. That is, the magnetic force of the magnet acts on the reed pieces for a long time, and the on time of the reed switch becomes long.

[0031]

The present invention will be described in detail with reference to the drawings. The same reference numerals denote the same objects throughout the drawings.

FIG. 1 is a diagram of an embodiment of the invention of claim 1,
(A) is a sectional view before impact, (B) is a sectional view after impact, FIG. 2 is a characteristic diagram of the invention of claim 1, FIG. 3 is a sectional view of an embodiment of the invention of claim 2, and FIG. In the figure of the embodiment of the invention of claim 3, (A)
Is a sectional view immediately after impact, (B) is a front view of the magnet, and FIG. 5 is a sectional view of an embodiment of the invention of claim 4.

In FIG. 1, 10 is a pair of lead pieces 11-.
1, 11-2 are inserted and sealed from both ends of an elongated sealing tube 13 (for example, a glass tube) 13, and both lead pieces 11-1, 1
This is a reed switch in which the tip ends of 1-2 are almost in the center of the sealing tube 13 and overlap each other with a gap.

In an impact sensor used for an automobile airbag or the like, a current of about 10 amps flows through the reed switch 10. Therefore, it is desirable to use a cobalt-iron alloy, which has good heat dissipation and a high Curie point, as the material of the lead piece.

Although not shown, the reed switch 10 is inserted into a protective cylinder made of synthetic resin or the like, or the sealing tube 13 is used.
The resin is attached to the outer periphery of the sealing tube 13 to prevent damage to the sealing tube 13.

Reference numeral 5 denotes a substantially rectangular parallelepiped housing made of synthetic resin or the like, in which a cylindrical cavity 9 is formed in the axial center portion by fitting a lid on the opening side. Reference numeral 20 shown in FIG. 1 is a ring-shaped magnet whose outer diameter dimension is desirably smaller than the inner diameter dimension of the cavity 9.

The magnet 20 is slidably fitted on the reed switch 10, the compression coil spring 3 is further fitted on the reed switch 10, and the magnet 20 is placed on the selected cavity end face 6 side, and the axis of the cavity 9 is penetrated. Reed switch 10 to housing 5
It is housed and fixed in.

Since the reed switch 10, the magnet 20 and the compression coil spring 3 are assembled as described above, one end of the compression coil spring 3 is seated on the forward end face 21 of the magnet 20 and the other end thereof is seated. Is seated on the cavity end face opposite to the cavity end face 6.

Therefore, the magnet 20 is biased by the compression coil spring 3, and its retracted end face 22 is always in contact with the cavity end face 6. A stopper 7 is provided at a predetermined position on the inner wall of the cavity 9 to prevent the magnet 20 from moving forward excessively when the impact sensor is activated.

Further, after filling the cavity 9 with a viscous liquid L (for example, oil), a lid is fitted on the opening of the cavity 9. The impact sensor configured as described above is shown in FIG.
When an impact force P larger than a predetermined value is applied from the direction shown by the arrow in FIG. 5, the magnet 20 moves forward against the elastic force of the compression coil spring 3 (to the right in the figure), and the forward end surface of the magnet 20.
21 contacts the stopper 7 and stops.

At this time, when the magnet 20 moves forward to some extent, the magnetic force of the magnet 20 acts on the reed pieces, and the tip portions of both reed pieces come into close contact with each other, so that the reed switch 10 is turned on. This ON state continues until the magnet 20 reaches the position of the stopper 7 and starts to retreat by the repulsive force of the compression coil spring 3 and retreats to a predetermined position.

On the other hand, when the magnet 20 starts to move forward, the cavity 9
L (oil) filled in the compression coil spring 3 side of
Flows through the outside of the magnet and flows into the back side (retraction side) of the magnet. When the magnet 20 contacts the stopper 7 and the forward movement is blocked, the repulsive force of the compression coil spring 3 immediately starts the backward movement, but the liquid L filled on the back side of the magnet 20 slows the backward movement speed of the magnet. ..

As a result, the time during which the magnetic force of the magnet 20 acts on the reed piece becomes longer, and the on time of the reed switch 10 becomes longer. Then, the retreat of the magnet 20 is stopped at the position where the magnet 20 is sufficiently retracted and the retracted side end face 22 is in contact with the cavity end face 6.

FIG. 2 shows the relationship between the viscosity of the liquid L and the on time of the reed switch. In FIG. 2, the vertical axis represents the moving length of the magnet, the horizontal axis represents the time after the impact, and the solid curve shows the correlation between the moving length of the magnet and the viscosity ζ of the liquid.

It should be noted that ζ = 0 represents that the cavity is filled with air, and that the viscosity of the liquid is large as ζ becomes 0.4, 0.7, and 1.0. When the impact force P is applied to the impact sensor as shown by the dotted curve in FIG. 2, the magnet starts the forward movement as shown by the solid line with a slight delay, and when the point reaches point Q, the reed switch is turned on. ..

The ON state is maintained, and the magnet advances (when the stopper is not provided) to a position where the repulsive force of the compression coil spring and the kinetic energy of the magnet are equal. Next, the magnet starts retreating and when the point reaches Q, the reed switch is turned off.

It is clear from FIG. 2 that the on time of the reed switch becomes longer as the viscosity of the liquid increases. Therefore, it is preferable to use oil having a particularly high viscosity, instead of water, in the cavity.

Reference numeral 20 shown in FIG. 3 is a ring-shaped magnet whose outer diameter is slightly smaller than the inner diameter of the cavity 9. 40
Is both ends of the cavity 9 provided in the housing 5, that is, the end on the cavity end face 6 side of the cavity 9 on the side opposite to the compression coil spring 3 (the end portion in the receding direction of the magnet) and the compression coil spring 3. It is a bypass that communicates with the seated end (the end in the forward direction of the magnet).

A check valve 41 is attached to the opening of the bypass 40 on the cavity end face 6 side. With the configuration as described above, when the impact sensor receives an impact and the magnet 20 advances, the liquid L filled in the compression coil spring 3 side of the cavity 9 reaches the check valve 41 via the bypass 40. The check valve 41 is opened by the pressure and flows into the back side of the magnet 20.

Next, when the magnet 20 starts to retract due to the repulsive force of the compression coil spring 3, the liquid L on the back side of the magnet 20 is moved.
Tries to flow backward through the bypass 40 and flow to the compression coil spring 3 side of the cavity 9, that is, the cavity 9 portion on the forward direction side of the magnet 20.

At this time, however, the check valve 41 is closed, so that backflow is prevented. Therefore, the cavity 9 portion on the forward direction side has a negative pressure. Therefore, the retreat speed of the magnet 20 becomes slow, and the on time of the reed switch 10 becomes long.

Reference numeral 20 shown in FIG. 4 is a ring-shaped magnet whose outer diameter is slightly smaller than the inner diameter of the cavity 9. magnet
20 has a plurality of holes (4 in the figure) parallel to the axis.
30 is provided. A check valve 31 is attached to each opening of the holes 30 on the side opposite to the compression coil spring 3.

With the above-described structure, when the shock sensor receives a shock and the magnet 2 advances, the liquid L filled in the compression coil spring 3 side of the cavity 9 passes through the hole 30 and the check valve. 31, the pressure causes the check valve 31 to open and the magnet 20
Flows into the back side of.

Next, when the magnet 20 starts to retract due to the repulsive force of the compression coil spring 3, the liquid L on the back side of the magnet 20 is moved.
Tends to flow backwards through the hole 30 and flow toward the compression coil spring 3 side of the cavity 9, that is, to the cavity 9 portion on the forward side of the magnet 20.

At this time, however, the check valve 31 is closed, so that backflow is prevented. Therefore, a negative pressure is applied to the cavity 9 portion on the forward direction side, and the retreating speed of the magnet 20 becomes slow. That is, the on-time of the reed switch 10 becomes long.

Reference numeral 200 shown in FIG. 5 is a frusto-conical magnet whose outer diameter is smaller than the inner diameter of the cavity 9 and which is sufficiently small on the compression coil spring 3 side. Therefore, when the impact sensor receives an impact and the magnet 200 moves forward, the liquid L filled in the compression coil spring 3 side of the cavity 9 flows in the outer peripheral direction along the inclined surface of the magnet 200 and passes outside the magnet 200. Flows into the back side of the magnet 200.

At this time, since the magnet 200 has a truncated cone shape, the flow of the liquid L is hardly obstructed. That is, since the advancing speed of the magnet 200 is hardly reduced, the start time when the reed switch 10 is turned on is not delayed.

On the other hand, when the magnet 200 retreats due to the repulsive force of the compression coil spring 3, the liquid L filling the back side of the magnet 200 slows the retreat speed of the magnet 200. Therefore,
The on time of the reed switch 10 becomes longer.

[0059]

As described above, according to the present invention, the cavity of the housing that houses the reed switch, the magnet, and the compression coil spring is filled with a viscous liquid such as oil, and the impact sensor is activated by the impact. After that, the impact sensor is configured so that the retreating speed of the magnet is decelerated, and has a practically excellent effect that the on time of the reed switch, that is, the operation time of the impact sensor is long.

Further, there is an effect that the structure is simple and the cost is low.

[Brief description of drawings]

FIG. 1 is a diagram of an embodiment of the invention of claim 1, (A) is a sectional view before impact, and (B) is a sectional view after impact.

FIG. 2 is a characteristic diagram of the invention of claim 1.

FIG. 3 is a sectional view of an embodiment of the invention of claim 2;

FIG. 4 is a diagram of an embodiment of the invention of claim 3, (A) is a sectional view immediately after impact, and (B) is a front view of a magnet.

FIG. 5 is a sectional view of an embodiment of the invention of claim 4;

FIG. 6 is a sectional view of a conventional example.

FIG. 7 is a diagram for explaining the operation of the impact sensor.

[Explanation of symbols]

 2,20,200 Magnet 3 Compression coil spring 5 Housing 6 Cavity end face 7 Stopper 9 Cavity 10 Reed switch 11-1,11-2 Reed piece 13 Sealing tube 30 Hole 40 Bypass 31,41 Check valve

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shutaro Tajima 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (4)

[Claims] 1. A reed switch (10) penetrating a cavity (9) of a housing (5), a magnet (20) slidably fitted to the reed switch (10), and a reed switch (10). Compression coil spring (3) for urging the magnet (20) toward one end
In the sensor in which the magnet (20) moves forward against the elastic force of the compression coil spring (3) when an impact is applied and the reed switch (10) is turned on, the cavity ( 9) An impact sensor characterized by being filled with liquid (L). 2. A bypass (4) connecting both ends of the cavity (9).
0) and a check valve (41) mounted in the opening of the bypass (40) on the end side of the cavity (9) opposite to the compression coil spring (3).
The impact sensor according to claim 1, further comprising: 3. A hole (30) provided in the magnet (20) so as to be parallel to the axis, and a check fitted to the opening of the hole (30) opposite to the compression coil spring (3). The impact sensor according to claim 1, further comprising a valve (31). 4. The shock sensor according to claim 1, wherein the magnet (200) has a truncated cone shape having a small diameter on the compression coil spring (3) side.