JPH0921826A - Acceleration detector - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To improve DW without increasing the size in the detection direction.
An acceleration detector with a large T (Dwell Time) is provided. SOLUTION: A cylindrical non-magnetic body 10 smaller than the inner diameter of the magnet 2 is provided on the end face A'side of the magnet 2 far from the stopper 5, and a coil spring 3 is attached at this position. In this way, the coil spring storage portion L _SPR and the magnet's longitudinal dimension L _MAG overlap, and this overlapped dimension is used as an increase in the magnet's longitudinal dimension L _MAG and magnet moving distance L _TR. To be

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system which is mounted on a moving body such as an automobile and is required to detect acceleration of an occupant protection device or the like at the time of a collision.

[0002]

2. Description of the Related Art FIG. 3 is a vertical sectional view of a conventional acceleration detector. The reed switch 11 is held at a predetermined position in the case 14 by a reed switch protection resin 19. The magnet 12 is biased by the coil spring 13 toward the lid 16 in the cylindrical body of the case 14. A signal terminal 17 and a reinforcing terminal 18 project from the case 14 as terminals.

In this structure, the coil spring 13 is
It is regulated by the end face A of the magnet 12, and the contact of the reed switch 11 is turned on at a predetermined position in the movement section of the magnet 12 up to the stopper 15 due to the addition of acceleration.
Turn it off.

In this acceleration detector, the main component of the dimension in the detection direction is the longitudinal dimension L _{MAG of} the magnet 12,
The moving distance L _TR of the magnet 12, the size L _SPR of the housing portion of the coil spring 13, the signal terminal lead-out part / others L _ETC , and in the case of the conventional acceleration detector, these size components are arranged in series and overlap. Not not.

[0005]

In this acceleration detector, as a characteristic with respect to the added acceleration, as shown in FIG. 4, there is shown a TTC (TimeTO Contact) characteristic which is the time from the addition of the acceleration to the turning on of the reed switch, and the reed switch. There is a DWT (Dwell Time) characteristic that is an ON duration. Generally, the acceleration detector is required to have a short TTC characteristic and a long DWT characteristic.

Of these, in order to lengthen the DWT characteristics, it is effective in designing the magnetic circuit of the reed switch and the magnet to widen the ON area of the reed switch and lengthen the section where the magnet exists in this ON area. It becomes a means. The expansion of the ON region is realized by increasing the longitudinal dimension L _{MAG of the} magnet. At this time, the detection direction of the acceleration detector is the longitudinal dimension L _{MAG of the} magnet.
Becomes longer by the increment of.

Further, the section in which the magnet exists in this ON region is reflected in the moving distance L _TR of the magnet from the initial position of the magnet to the stopper position. Therefore,
In order to lengthen the DWT characteristic, it is necessary to lengthen the moving distance L _TR of this magnet.

Due to these matters, in order to lengthen the DWT characteristic, the longitudinal dimension L _{MAG of} the magnet and the moving distance L _{TR of the} magnet become large, and this increase is the same as the dimension increase in the detection direction of the acceleration detector. Had the following problems.

Therefore, the technical problem of the present invention is to increase the moving distance of the magnet and lengthen the DWT characteristic without increasing the size of the acceleration detector in the detection direction.

[0010]

According to the present invention, in order to obtain an acceleration detector having a long DWT characteristic while maintaining the dimension in the detection direction of the acceleration detector, the end face on the side opposite to the stopper side of the magnet is A cylindrical non-magnetic material having an inner diameter smaller than the inner diameter of the cylindrical magnet is additionally provided, and the biasing amount of the coil spring with respect to the magnet is defined at this location. By this, the longitudinal dimension L of the magnet
The dimension components of the _MAG and the coil spring storage portion L _SPR overlap. This overlapping dimension is the longitudinal dimension L of the magnet
_We will use this to increase the travel distance L _TR of the _MAG and magnet,
Prolongs DWT characteristics.

Further, according to the present invention, a convex portion is provided at the center of the inner surface of the cylindrical magnet in the lengthwise direction, and the biasing amount of the coil spring with respect to the magnet is defined at this portion. As a result, the longitudinal dimension L _{MAG of the} magnet partially overlaps with the dimension component of the coil spring housing portion L _SPR . This overlapping dimension is the longitudinal dimension L of the magnet
_MAG and D are used to increase the moving distance L _TR of the magnet.
Prolongs WT characteristics.

(Operation) According to the present invention, by accommodating a cylindrical non-magnetic member having an inner diameter smaller than the inner diameter of the magnet on the end face of the acceleration detector on the side far from the stopper, the coil spring housing portion is provided. L _SPR and the magnet longitudinal dimension L _MAG are made to overlap. This overlapping dimension can be used for increasing the longitudinal dimension L _{MAG of} the magnet and the moving distance L _TR of the magnet, and the section where the magnet exists in the ON region of the reed switch can be increased. DWT characteristic is ON of this reed switch
Since it depends on the region section length,
It is possible to obtain an acceleration detector that maintains the detection direction dimension of the acceleration detector and has a long DWT characteristic.

Further, according to the present invention, by providing a convex portion at the center of the inner surface of the cylindrical magnet of the acceleration detector in the length direction, one of the coil spring storage portion L _SPR and the magnet longitudinal dimension L _MAG can be obtained. The parts are duplicated. The overlap dimension of the magnet longitudinal dimension L _{MA G,} can be devoted to lengthening the travel distance L _TR magnet, the magnet can be increased section existing ON area of the reed switch. Since the DWT characteristic depends on the length of the ON region section of the reed switch, it is possible to obtain the acceleration detector having a long DWT characteristic while maintaining the dimension of the acceleration detector in the detection direction by the above-mentioned procedure. Further, since the biasing position with respect to the magnet comes closer to the center of gravity of the magnet, the follow-up to the complicated shock wave generated in the actual collision is improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the acceleration detector of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a schematic sectional view showing the structure of an acceleration detector according to Embodiment 1 of the present invention and the ON / OFF positions of reed switches.

In this structure, the magnet 2 provided with the cylindrical non-magnetic body 10 having an inner diameter smaller than the inner diameter of the cylindrical magnet 2 is arranged on the end surface A'in the case 4 on the side remote from the stopper 5. From the end surface A ′ of the magnet provided with the non-magnetic material 10 to the end surface A facing in the stopper direction, the coil spring 3 extends into the inside of the magnet 2 to support the magnet 2. The reed switch 1 is held at a predetermined position in the case 2 by a reed switch protection resin 9.

When acceleration G is applied to this detector from a predetermined direction, the magnet 2 moves from the initial stationary position L ₀ toward the stopper 5 to the stopper position L _{M AX} in accordance with the magnitude of the magnet G, The contact turns on at the L _ON position.
When the acceleration G is released, the magnet 2 returns to the initial rest position L ₀ by the restoring force of the coil spring 3,
_The contact turns _{OFF at} the _OFF position.

In this path, the DWT characteristic depends on the reed switch ON section which is the sum of the distance from the reed switch ON position L _ON to the stopper position L _{MAX and} the distance from the stopper position L _MAX to the reed switch OFF position L _{OF F.} To do. That is, in order to lengthen the DWT characteristic, it is necessary to increase the length of the reed switch ON section.

At this time, in order to maintain the detection direction dimension of the acceleration detector, the dimension of the magnet longitudinal dimension L _MAG and the magnet movement distance L _{TR which} are increased due to the lengthening of the DWT characteristic are changed to other dimensions. The ingredients must absorb.

In the present embodiment, a cylindrical non-magnetic body 10 having an inner diameter smaller than the inner diameter of the magnet 2 is provided on the end surface A'of the magnet 2 far from the stopper 5, and the coil spring 3 is attached at this position. Therefore, in the inner diameter portion of the magnet 2, the coil spring storage portion L _SPR and the magnet longitudinal dimension L _MAG overlap. This overlapping dimension is applied to the increased dimension of the longitudinal dimension L _{MAG of} the magnet and the moving distance L _TR of the magnet.

As described above, the dimension of the acceleration detector in the detection direction can be maintained, the reed switch ON section can be increased, and the DWT characteristic can be lengthened.

(Embodiment 2) In this embodiment, as shown in FIG. 2, an inwardly projecting portion is provided at the center of the inner surface of a cylindrical magnet 2 in the longitudinal direction. Since the coil spring 3 is attached to the step B on the stopper side by being inserted into the inside of the magnet as well, in the section from the step B of the magnet 2 to the magnet end surface A, the coil spring housing portion L _SPR and the magnet longitudinal dimension. L _MAG will be duplicated. This overlapping dimension component is applied to the increased dimension of the magnet longitudinal dimension L _MAG and the magnet movement distance L _TR .

As described above, it is possible to maintain the dimension of the acceleration detector in the detection direction, increase the ON section of the reed switch, and realize a long DWT characteristic.
Further, since the biasing position with respect to the magnet is closer to the center of gravity of the magnet, the followability to a complicated shock wave at the time of collision is improved and the reliability is improved.

[0024]

As described above, according to the present invention, the reed switch ON section is increased while maintaining the detection direction dimension of the acceleration detector, and the DWT characteristic is lengthened.
It has become possible to provide an acceleration detector with improved reliability.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an acceleration detector according to an embodiment of the present invention and a diagram schematically showing ON and OFF positions of a reed switch.

FIG. 2 is a vertical sectional view of an acceleration detector according to another embodiment of the present invention and a diagram schematically showing ON / OFF positions of reed switches.

FIG. 3 is a diagram schematically showing a vertical cross-sectional view of a conventional acceleration detector.

FIG. 4 is a schematic diagram of characteristics of an acceleration detector against impact.

[Explanation of symbols]

1,11 Reed switch 2,12 Magnet 3,13 Coil spring 4,14 Case 5,15 Stopper 6,16 Lid 7,17 Signal terminal 8,18 Reinforcement terminal 9,19 Reed switch protective resin 10 Non-magnetic material A, A 'Magnet end surface B Step of the convex part provided in the center of the inner surface of the magnet L _MAG Longitudinal dimension of the magnet L _TR Magnet moving distance L _SPR Coil spring housing dimension L _ETC Signal terminal lead-out / other dimension L ₀ Initial static position of magnet L _MAX Stopper position L _ON Reed switch ON position L _OFF Reed switch OFF position G Acceleration

Claims (2)

[Claims] 1. An acceleration detector, which is composed of a reed switch, a magnet, and a coil spring, moves the magnet by an acceleration applied in the detection direction and operates the reed switch. An acceleration detector characterized in that a non-magnetic material is attached to an end face portion, and the amount of bias of the coil spring with respect to the magnet is defined by the non-magnetic material. 2. An acceleration detector, which is composed of a reed switch, a magnet, and a coil spring, and in which the magnet is moved by the acceleration applied in the detection direction to operate the reed switch, in the longitudinal direction of the inner surface of the magnet An acceleration detector characterized in that a convex portion is provided in a central portion, and the convex portion defines the biasing amount of the coil spring with respect to the magnet.