JP2655505B2 - Impact sensor - Google Patents

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 for an automobile seat belt, an airbag, and the like, and more particularly to an impact sensor capable of detecting a sudden and large impact and operating.

[0002]

2. Description of the Related Art Conventionally, as such an impact sensor, a sensor using a reed switch and a magnet is known.
For example, there is a type in which a slide tube is arranged around a reed switch, and a ring-shaped magnet is supported by a spring outside the tube. In addition, this sensor has a back stopper that supports the magnet at the position where the reed switch is turned off, so that the magnet can move when a force exceeding a predetermined impact is applied from a direction parallel to the reed switch. ing.

FIG. 5 is a cross-sectional view of such a conventional shock sensor. As shown in FIG. 5, in this shock sensor, a case 9 having a sliding tube 2 is arranged around a reed switch 1 for leading a terminal 7 to the outside, and a ring-shaped magnet 3 is provided outside the tube 2. Spring 4
To the back stopper 6. In this state, the reed switch 1 is off. Also,
The front stopper 5 is fixed at a position opposite to the back stopper 6 in the case 9.

[0004] In the shock sensor having such a structure, when a predetermined or more shock is applied from the axial direction of the reed switch 1, the magnet 3 moves toward the front stopper 5, and the reed switch 1 is turned on. . Next, when the impact disappears, the magnet 3 returns to the fixed position on the back stopper 6 side due to the elasticity of the spring 4.

In such an impact sensor, a non-magnetic metal, polyamide, P
A relatively hard resin material such as BT having a Rockwell hardness of about M90 is used. Therefore, when an impact force exceeding a predetermined level is applied, the magnet 3 is moved to the front stopper 5.
, And moves to the area where the reed switch 1 is turned off in the direction of the back stopper 6 by the repulsive force.
Therefore, the contact of the reed switch 1 is turned off,
Such a resin material shortens the ON time of the contact,
It gets longer. At this time, if the impact force is continued, the contact of the reed switch 1 is turned on again, and chattering occurs. Further, when the magnet 3 collides with the front stopper 5, the contact of the reed switch 1 may generate chattering due to the vibration component of the collision.

[0006] As an impact sensor for preventing the occurrence of chattering, for example, a sensor as disclosed in Japanese Patent Application Laid-Open No. 3-110731 is known.

FIG. 6 is a sectional view of an impact sensor showing such a conventional improvement. As shown in FIG. 6, this impact sensor uses two inertial moving bodies 12, 13 and two springs 4, 14 instead of the front stopper and the back stopper. That is, at the time of a small impact, the inertial moving bodies 12 and 13 fixed to both ends of the magnet 3 move to operate the reed switch 1. In addition, at the time of a large impact, the inertial moving body 12 reaches the bottom surface 15 and tries to repel. However, since the repulsion is suppressed by being pressed against the inertial moving body 13, the ON time of the contact of the reed switch 1 is lengthened.

[0008]

In the above-described conventional impact sensor, if it is to be realized with a simple structure, there is a problem that the chattering of the contact occurs and the ON time of the contact varies. In order to prevent the variation in the ON time of the contacts, it is indispensable to absorb the vibration component of the collision when the magnet returns to Teiichi, and there is a disadvantage that the structure becomes complicated and the number of parts increases.

Further, when the structure of the conventional shock sensor is complicated, there is a disadvantage that the probability of occurrence of troubles such as the snagging of the inertial moving body increases due to a difference in the expansion rate of each piece due to a change in ambient temperature.

An object of the present invention is to prevent reed switch chattering due to such a difference in impact force,
An object of the present invention is to provide an impact sensor which has a simplified structure, realizes a long ON time, and does not cause any trouble such as catching.

[0011]

The impact sensor according to the present invention comprises:
A reed switch, a tube formed in the center of the sensor case and provided around the reed switch,
A magnet that drives the reed switch by moving along the outer circumference of the tube, a spring that supports the magnet, a back stopper that sets an initial position of the magnet that moves by impact, and the back stopper of the magnet In a shock sensor having a front stopper that determines a moving range from the magnet, a relaxation spring is fixed to both sides of the magnet on the back stopper side and the front stopper side.

Further, in the shock sensor of the present invention, the relaxation spring is formed by cutting and raising each of the springs from a plurality of locations.
One or a plurality of finger portions are formed.

Further, in the shock sensor according to the present invention, the relaxation spring is made of a magnetic material.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an impact sensor showing one embodiment of the present invention. As shown in FIG. 1, in this embodiment, a reed switch 1 is housed in a tube 2 formed at the center of a sensor case 9, and a ring-shaped magnet 3 for driving the reed switch 1 is provided along the outer periphery of the tube 2. It is a structure to arrange. The magnet 3 is supported by a coil spring 4 disposed outside the tube 2, and is pressed against a back stopper 6 fixed to a case 8. The back stopper 6 sets the initial position of the magnet 3 that moves in the axial direction of the reed switch 1 due to an impact. A front stopper 5 made of a resin material is fixed to an end of the case 9 opposite to the back stopper 6, and the front stopper 5 is provided to determine a moving range of the magnet 3 from the back stopper 6. Can be In addition, the magnet 3 is provided on both sides thereof, that is, on the side of the back stopper 6 and the side of the front stopper 5, with a relaxation spring 8 for absorbing collision energy.
a and 8b are provided. The relaxation springs 8a and 8b are made of, for example, Fe—Ni alloy or Fe—Cr
A magnet 3 made of a magnetic material such as
Is attracted by the magnetic force. Further, the relaxing springs 8 a and 8 b may be fixed to the magnet 3.

However, in the conventional example described above, when an excessive impact is applied, the magnet 3
Or the inertial moving body collides with the bottom of the case, and then the contact of the reed switch 1 is turned off.
Since the area is bounced back, the time during which the switch is ON is shortened. In addition, chattering occurs at the contact of the reed switch 1 due to a vibration component at the time of collision with the front stopper 5. Furthermore, when the impact disappears after the magnet 3 collides with the front stopper 5 and the contact is turned ON, the magnet 3 returns to the home position due to the elasticity of the spring 4. As a result, the device itself incorporating the impact sensor may malfunction.

On the other hand, in this embodiment, the magnet 3
Since the relaxation springs 8a and 8b are provided on both sides of the magnet 3, when the magnet 3 collides with the front stopper 5,
Since the relaxation spring 8b absorbs the collision energy,
The repulsion amount of the magnet 3 becomes extremely small, and the magnet 3 does not rebound to the contact OFF region of the reed switch 1. Similarly, the relaxation spring 8a also absorbs collision energy when the magnet 3 rebounds to the back stopper 5. Due to the reduction of the vibration component of the collision, chattering of the contact of the reed switch 1 does not occur, so that a long ON time can be continued.

FIGS. 2A and 2B are a plan view and a perspective view, respectively, of the relaxation spring shown in FIG. FIG.
As shown in (a) and (b), the relaxation spring 8a in the above-described impact sensor is provided on the magnet 3 on the back stopper 6 side, and is cut and raised from three places in the same direction (clockwise). One finger portion 10 is formed. Note that the finger portion 10 may have two finger portions formed in the opposite direction from the same point (relaxation spring 8b), and various shapes may be adopted.

FIG. 3 is a distribution characteristic diagram of the ON time of the switch in FIG. As shown in FIG. 3, the ON time of the switch in this embodiment is about 9 m in the case of a large impact.
s, about 11 ms for small impact,
The variation of the ON time due to the difference in the impact force is reduced, and the average ON time is about 10 ms. This is O
When represented by the normal distribution probability for N hours, the characteristic A shown by the solid line
become that way. The characteristic B indicated by the dotted line is the ON value of the conventional example.
The time distribution characteristic is about 2 ms for a large impact and about 8 ms for a small impact, and the average ON time is about 3 to 4 ms. Thus, in this embodiment, the ON
While the time is kept at least three times longer than that of the conventional product, the fluctuation of the ON time due to the difference in impact force is reduced.

FIG. 4 is a sectional view of an impact sensor showing another embodiment of the present invention. As shown in FIG. 4, the present embodiment is different from the above-described embodiment in that concave portions 11 for accommodating the relaxing springs 8a and 8b are formed on both sides of the magnet 3, and they are fixed with an adhesive. Others are the same. In the present embodiment, the portions other than the finger portions of the relaxation springs 8a and 8b can be located in the magnet 3, so that
There is an advantage that the size can be reduced as compared with the embodiment described above.

The shape of the relaxation spring described above is not limited to the finger shape, but can be appropriately selected, such as a coil and wire work.

[0021]

As described above, the impact sensor according to the present invention has three times the ON time of the contact of the reed switch by providing relaxation springs for absorbing the collision energy on both sides of the magnet driving the reed switch. Thus, there is an effect that a long ON time can be continued for a large impact.

Further, according to the present invention, the vibration component of the collision can be reduced by the relaxation spring, and the occurrence of noise to the outside can be suppressed. Therefore, there is an effect that malfunction of the built-in device can be prevented.

Further, according to the present invention, by simplifying the structure, it is possible to reduce the number of parts and to reduce the occurrence of problems such as catching of a magnet.

[Brief description of the drawings]

FIG. 1 is a sectional view of an impact sensor showing one embodiment of the present invention.

FIG. 2 is a plan view and a perspective view of a relaxation spring shown in FIG.

FIG. 3 is a distribution characteristic diagram of the ON time of the switch in FIG. 1;

FIG. 4 is a sectional view of an impact sensor showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an impact sensor showing an example of the related art.

FIG. 6 is a sectional view of an impact sensor showing another example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reed switch 2 Tube 3 Magnet 4 Spring 5 Front stopper 6 Back stopper 7 Terminal 8a, 8b Relaxing spring 9 Case 10 Finger part 11 Concave part

Claims (3)

(57) [Claims] A reed switch, a tube formed in the center of the sensor case and provided around the reed switch, a magnet for driving the reed switch by moving along the outer periphery of the tube,
In an impact sensor, a spring that supports the magnet, a back stopper that sets an initial position of the magnet that moves by an impact, and a front stopper that determines a moving range of the magnet from the back stopper are arranged. An impact sensor, wherein a relaxation spring is fixed to both sides of the back stopper side and the front stopper side. 2. The impact sensor according to claim 1, wherein the relaxation spring forms one or a plurality of finger portions respectively cut and raised from a plurality of locations. 3. The shock sensor according to claim 1, wherein the relaxation spring is made of a magnetic material.