JPH06302255A - Impact sensor - Google Patents

Abstract

PURPOSE:To secure the staying time of a magnet moving member at the position of a contact in an operating condition so as to ensure the operation, and to realize a simple structure and a low cost, in an impact sensor. CONSTITUTION:A simple form of magnetic member 8 is provided to a position to bury a front stopper 7 to which a magnet 3 moving from the position A to the position B by the acceleration of an impact is not contacted directly. By the magnetic force operating to the magnetic member 8 and the magnet 3, a bouncing force by the collision of the magnet 3 is suppressed, so as to extend the staying time of the magnet 3 at the position B, and the contact of a reed switch 1 is operated.

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 contact is activated by a momentary large acceleration such as a collision between objects.

[0002]

2. Description of the Related Art Generally, such an impact sensor is used as a switch for activating a protector for an air bag of an automobile or a human body such as a seat belt. That is, a large acceleration force due to a collision or a sudden braking is detected, and the circuit for activating the protective equipment is activated by this detection.

Conventionally, this type of shock sensor uses a reed switch in which a contact made of a ferromagnetic material is built in a glass tube, and a tube of a non-magnetic material is provided so as to enclose the reed switch. In this structure, a moving member having a magnet that can be moved is inserted into a tube, a spring is inserted into one side of the moving member, and the spring is constantly pressed against the other side of a housing enclosing the moving member. Then, when a large acceleration force generated by a shock or the like is applied, a moving member having a large mass moves on the tube and the contact of the reed switch closes. Further, when the impact force is absorbed and the acceleration disappears, the moving member is pushed back to the other side by the repulsive force of the spring, and the contact is opened and turned off by the restoring force of the support part of the contact part.

However, in this shock sensor, the moving member itself often bounces when the moving member collides with one end of the housing, and the moving member is quickly pushed back to the other side due to the repulsive force of the spring, and the contact portion of the moving member. The dwell time at the closed position of may be shortened. Therefore, there is a problem that the circuit for operating the protective equipment is not energized. Various measures and improvements have been made as measures against this short dwell time. A typical example thereof is disclosed in Japanese Patent Application Laid-Open No. 311011031.

In this impact sensor, the above-mentioned moving member that moves on the tube enclosing the reed switch is used as a first moving member, and further, a non-magnetic material having a large mass that can slide on the first moving member. A second moving member is provided, and another large-diameter spring is inserted between the outer flange of the first moving member and the inner flange of the second moving member to move the two moving members. It has a structure with a heavy sliding mechanism. Then, due to the acceleration at the time of impact, the first moving member first moves against the spring and collides with the end surface of the housing, and then the second moving member, which moves continuously with the same acceleration, has a large inertial force and a large diameter. The spring is compressed, and the repulsive force suppresses the rebound caused by the collision of the first moving member and extends the dwell time of the first moving member. And, it was possible to obtain a long dwell time such as 30 msec instead of the dwell time which was obtained by the impact sensor for only 5 msec.

[0006]

However, although the impact sensor described above can prolong the dwell time,
The double sliding mechanism complicates the structure and increases the number of parts required. Therefore, the material and the manufacturing cost are increased, and since there is the double sliding mechanism portion, the probability of the catching phenomenon caused by one of the two moving members is increased and the reliability may be reduced. This is very dangerous when used in the operating circuit of protective equipment.

Therefore, an object of the present invention is to provide an impact sensor which secures the dwell time of the magnet moving member at the position of the contact portion during operation to ensure the operation and has a simple structure and is inexpensive. Is.

[0008]

The features of the present invention are: a reed switch having a built-in contact, a tube enclosing the outer circumference of the reed switch, a front stopper and a back stopper fixed to both ends of the tube, An impact sensor having a magnet that is fitted into a tube and moves by an impact force to operate the contact, and a spring that is inserted between the front stopper and the magnet and presses the magnet against the back stopper by its repulsive force Is a shock sensor including a magnetic member attached to a portion of the front stopper that does not come into contact with the magnet that moves by.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an impact sensor showing an embodiment of the present invention. As shown in FIG. 1, this shock sensor includes a tube 2 that encloses the outer periphery of a reed switch 1 having a built-in contact, a front stopper 7 and a back stopper 5 fixed to both ends of the tube 2, and a tube 2 fitted into the tube 2. The magnet 3 that moves by the impact force to move the contact of the reed switch 1 and the spring 4 that is inserted between the front stopper 7 and the magnet 3 and presses the magnet 3 toward the back stopper 5 by its repulsive force.
And a magnetic member 8 embedded in the front stopper 7 that does not come into contact with the magnet 3 that moves due to impact.

That is, in this shock sensor, a plate-shaped magnetic member 8 made of a magnetic material such as pure iron is embedded in the front stopper 7, and the acceleration force at the time of impact resists the repulsive force of the spring 4. The magnet 3 moves from the point A to the point B and collides with the surface of the front stopper 7, and the rebounding force of the magnet 3 due to the collision is suppressed by the magnetic force of the magnetic member 8 and the magnet 3, so that the magnet 3 stays at the point B. Is to postpone.

In order to set the magnetic force of the magnetic member 8 and the magnet 3 to slightly exceed the repulsive force of the spring 4, the thickness of the non-magnetic material interposed between the magnetic member 8 and the magnet 3 is taken into consideration. Then, the position of the magnetic member 8 is determined. This means that although the material of the front stopper 7 is originally a plastic material having a small bounce coefficient, the gap between the magnet 3 and the magnetic member 8 is set so that an appropriate magnetic force can be obtained in order to make it smaller than the bounce coefficient. . That is, the magnetic member 8 and the magnet 3 are in direct contact with each other at the time of impact so as not to be attracted, and the repulsive force of the spring 4 exceeds the magnetic attraction force to push the magnet 3 back to its original position.

By the way, this impact sensor is attached to an impact tester, and a half sine wave (pulse width 30 ms) produces 25 G.
When the test was conducted at a moderate acceleration, the dwell time was about 20 milliseconds. This dwell time was long enough to energize the switches in the circuit that operated the protector.

FIG. 2 is a sectional view of an impact sensor showing another embodiment of the present invention. In this impact sensor, as shown in FIG. 2, a ring-shaped magnetic member 8a having a hole having a size through which the outer shape of the magnet 3 passes is inserted into the space of the case 6 and attached in close contact with the front stopper 7a. . Other than that is the same as the above-mentioned embodiment. In this embodiment, when the magnet 3 moves to the point B due to an impact, the outer periphery of the magnet 3 is covered with the magnetic member 8a. By changing the width of the magnetic member 8a, there is an advantage that the strength of the magnetic force can be appropriately adjusted.

[0015]

As described above, according to the present invention, the magnetic member is disposed at the position of the front stopper, which is the contact portion where the magnet moving due to the acceleration upon impact does not come into direct contact, and acts on the magnetic member and the magnet. The repulsive force due to the collision of the magnets is suppressed by the generated magnetic force, and the dwell time of the magnets can be extended. Further, since it is sufficient to simply attach a magnetic member having a simple shape without providing a complicated mechanism or a movable portion, there is an effect that material cost and manufacturing cost are reduced and reliability is further improved.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 Reed switch 2 Tube 3 Magnet 4 Spring 5 Back stopper 6 Case 7 Front stopper 8, 8a Magnetic member

Claims (1)

[Claims] 1. A reed switch having a built-in contact, a tube enclosing the outer periphery of the reed switch, a front stopper and a back stopper fixed to both ends of the tube, and a tube which is fitted into the tube and is moved by an impact force. In a shock sensor having a magnet that operates a contact and a spring that is inserted between the front stopper and the magnet and presses the magnet toward the back stopper by its repulsive force, the front that does not come into contact with the magnet that moves due to a shock An impact sensor comprising a magnetic member attached to a stopper portion.