JPH05250968A - Impact sensor - Google Patents

Abstract

PURPOSE:To reduce a bounce amount of a magnet against a front stopper so as to obtain a stable contact ON time of a reed switch by independently providing a spring capable of absorbing an excessive impact exerted on the magnet during operation in an impact sensor used for a seat belt or an air back for an automobile. CONSTITUTION:An impact sensor provided with a reed switch 1 and a magnet 3 movably supported by a spring 4 is such constituted that another spring in addition to the spring 4 is not brought into contact with the magnet 3 in a normal condition and is interposed in at least one end thereof between a front stopper 7 and the magnet 3. The spring may be a spring capable of absorbing an impact of the magnet 3, such as a coil spring 8 inserted at the other end thereof into a recess of the front stopper 7 and a plate spring 9 supported at the other end thereof by the inside of a case of the sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock sensor, and more particularly to a shock sensor for detecting and operating a shock applied to a seat belt or an airbag of an automobile.

[0002]

2. Description of the Related Art A conventional sensor of this type using a reed switch is shown in a sectional view of FIG.
In this conventional example, a tube 2 for magnet sliding is provided around a reed switch 1 as shown in FIG. 4, and a ring-shaped magnet 3 is supported by a spring 4 with the tube 2 penetrating the hole. Then, the back stopper 5 regulates the normal position of the magnet 3 to a position where the reed switch 1 is turned off.

The operation is such that when an impact in the reed direction of the reed switch 1 (direction of arrow 6 in the figure) is applied with a certain strength or more, the magnet 3 moves toward the front stopper 7 and the reed switch. When 1 is turned on and the impact disappears, the elasticity of the spring 4 causes the magnet 3 to return to its home position.

[0004]

In this conventional impact sensor, when a strong impact force of a certain value or more is applied, the magnet 3 collides with the front stopper 7, and the repulsive force thereof causes the magnet 3 to move toward the back stopper 5. Since the reed switch 1 moves to the off region and the contact of the reed switch 1 is turned off, when the on time of the contact is shortened or the impact force is continued, the contact of the reed switch 1 is turned on again. Turn on to generate chatter. Such a short on-time and the occurrence of chatter have the drawback of hindering the role of the shock sensor.

An object of the present invention is to solve the above-mentioned drawbacks and to provide an impact sensor in which the on-time is shortened even when a strong impact is applied and chatter is not generated.

[0006]

In order to achieve the above object, the impact sensor of the present invention comprises a reed switch 1, a tube 2 for housing the reed switch 1 in its hollow portion, and a tube 2 supported by a spring 4 on the tube 2. In a shock sensor having a magnet 3 that can move along, a back stopper 5 that restricts an initial position of the magnet 3 that moves when an impact is received, and a front stopper 7 that restricts a moving range of the magnet 3, a spring 4 as a first spring, and in addition to the first spring, a second spring which is not in contact with the magnet 3 in a normal state and is arranged so that at least one end thereof is between the front stopper 7 and the magnet 3. The structure will be provided.

The second spring has a structure in which the other end is a coil spring 8 inserted into the recess of the front stopper, or the other end is a plate-like spring 9 supported inside the case of the impact sensor.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment (first embodiment) of the present invention. FIG. 2 is a sectional view showing another embodiment (second embodiment) of the present invention. FIG. 3 is a sectional view taken along the line AA in the embodiment of FIG. In the first embodiment, as shown in FIG. 1, a tube 2 for magnet sliding, a magnet 3 for penetrating the tube 2, a spring 4 for urging the magnet 3 toward the back stopper 5, and a magnet around the reed switch 1. In addition to the back stopper 5 that determines the stationary position of the magnet 3 at all times and the front stopper 7 that determines the moving range of the magnet 3, a coil spring 8 that is a feature of the present invention is arranged. The coil spring 8 has one end protruding from the front stopper 7, but does not normally contact the magnet 3. The other end is supported by being inserted into the recess of the front stopper 7.

When an excessive shock is applied to the sensor, in the case of the conventional product, the magnet 3 collides with the front stopper 7 at a high speed and bounces back to the area where the contact of the reed switch 1 is turned off, and the on time is increased. Although shortened, in this embodiment, the magnet 3 contacts the coil spring 8 before colliding with the front stopper 7 and reaches the front stopper 7 while slowing down the speed, so that the repulsion amount is larger than that of the conventional product. A small number of them do not bounce up to the contact-off region of the reed switch 1, and the long on-time continues. Of course, there is no chatter.

In the second embodiment, as shown in FIGS. 2 and 3, a leaf spring 9 is used instead of the coil spring 8 of the embodiment of FIG. 1 to reduce the amount of repulsion by the front stopper 7. The leaf spring 9 has one end fixed to an appropriate position between the magnet 3 and the front stopper 7, and the other end fixed to the inside of the sensor case. When an excessive impact is applied to this sensor, the magnet 3 comes into contact with the leaf spring 9 before colliding with the front stopper 7 and slows down the speed. It will not bounce back to the contact-off area of. Therefore, a long ON time is continued and chatter does not occur.

The spring for absorbing the impact of the magnet 3 hitting the front stopper 7 is a coil spring 8 or a leaf spring 9 shown in FIGS.
Other than the above, the type, shape and supporting method are not limited.

[0012]

As described above, according to the present invention, in a sensor using a reed switch, by adding a spring arranged at a position to absorb the impact before the magnet reaches the front stopper, Since the amount that the magnet hits the front stopper and bounces can be reduced, it is possible to continue the long on-time of the reed switch even in the event of an excessive impact,
There is an effect that chatter does not occur. Therefore, by using the present embodiment, it is possible to guarantee a stable impact detection characteristic.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing another embodiment of the present invention.

3 is a sectional view taken along line AA of the embodiment of FIG.

FIG. 4 is a sectional view showing an example of a conventional impact sensor.

[Explanation of symbols]

 1 Reed switch 2 Tube 3 Magnet 4 Spring 5 Back stopper 7 Front stopper 8 Coil spring 9 Leaf spring

Claims (3)

[Claims] 1. A reed switch, a tube for accommodating the reed switch in its hollow portion, a magnet supported by a spring and movable along the tube, and an initial stage of the magnet that moves when an impact is applied. In a shock sensor having a back stopper that regulates a position and a front stopper that regulates a moving range of the magnet, the spring is a first spring, and in addition to the first spring, do not normally contact the magnet. And a second spring having at least one end arranged between the front stopper and the magnet. 2. The shock sensor according to claim 1, wherein the second spring is a coil spring having the other end inserted in the recess of the front stopper. 3. The impact sensor according to claim 1, wherein the second spring is a plate-like spring whose other end is supported inside the case of the impact sensor.