JP3099459B2 - Magnetic acceleration 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 acceleration sensor used for controlling an automobile and detecting an earthquake, and more particularly to a small and inexpensive magnetic acceleration sensor using a reed switch and a permanent magnet.

For example, in the field of automobiles, various electronic devices for ensuring safe driving have been developed. In order to operate these electronic devices reliably, an inexpensive acceleration sensor with high detection accuracy is required. became. In the fields of electronic exchanges and various information processing devices, inexpensive, high-accuracy earthquake detection acceleration sensors have been demanded in order to prevent damage to equipment in the event of an earthquake and to ensure safety.

[0003] Therefore, a permanent magnet is attached to the tip of a beam that is deflected by the applied acceleration, and at least two magnetoresistive elements are provided at symmetrical positions on both sides of the permanent magnet. Although an acceleration sensor having an adding unit for adding the data has appeared, there has been a demand for higher performance, smaller size, lighter weight, and lower cost.

[0004]

2. Description of the Related Art FIG. 2 is a perspective view showing a schematic configuration example of a conventional acceleration sensor using a magnetoresistive element. An acceleration sensor 1 supports a top end of a plate-like beam 2 which is bent by an applied acceleration. Fix to 3. An appropriate weight 4 is fixed to the lower end of the beam 2 made of a nonmagnetic material, and a permanent magnet 5 is fixed to the lower surface of the weight 4. In the thickness direction of the beam 2, magnetic detecting elements 6a and 6b facing the permanent magnet 5 are provided.
Housed in

In the acceleration sensor 1, when an acceleration is applied in the thickness direction of the beam 2, the beam 2 bends in the thickness direction corresponding to the magnitude of the applied acceleration. The magnet 5 moves, and the magnetic detection elements 6a and 6b output an electric signal corresponding to the magnetic field change by the permanent magnet 5. By detecting this electric signal, the magnitude of the applied acceleration can be known.

[0006]

A conventional acceleration sensor using a magnetoresistive element and its detecting device has high performance and can detect a value of an applied acceleration. Therefore, there has been a problem that the accuracy is higher than necessary and the cost is high for an application in which it is desired to detect whether the applied acceleration is lower than or higher than a certain value.

[0007]

Means for Solving the Problems The above-mentioned problem is solved in FIG.
, A fixed reed switch 13, a cylindrical permanent magnet 22 for externally fitting a contact portion of the reed switch 13, a spring 18 having one end fixed, and the spring elastically deformed in a predetermined direction by an applied acceleration. And a cylindrical shield member 24 fixed to the other end of 18, and between the reed switch 13 and the permanent magnet 22 to play the reed switch 13 as a concentric circle. When the spring 18 is stationary, the magnetism of the permanent magnet 22 is cut off from the contact portion, and when acceleration is applied to elastically deform the spring 18, the magnetism of the permanent magnet 22 is reduced. The problem is solved by a magnetic acceleration sensor configured to move to a position for operating a contact portion.

[0008]

As described in the above-mentioned means, the acceleration sensor of the present invention is constructed by using the reed switch 13, the cylindrical permanent magnet 22, the shield member 24, and the spring 18. Therefore, the acceleration sensor of the present invention for detecting whether or not the applied acceleration exceeds a certain value is less expensive than the conventional acceleration sensor using a magnetoresistive element or the like, because the sensor body and its detection device are inexpensive and used Since the circuit configuration of the detection device is significantly simplified as compared with the conventional detection device, the size can be reduced.

[0009]

FIG. 1 is a configuration diagram of a magnetic acceleration sensor according to an embodiment of the present invention.

In FIG. 1, an acceleration sensor 21 accommodates and fixes a ring-shaped permanent magnet 22 and a reed switch 13 having a contact portion at the center of the permanent magnet 22 in a housing 23. For example, the housing 23 made of a resin includes a pair of members 23a and 23.
b, and the terminal portions 13b of a pair of reed pieces of the reed switch 13 protrude.

A spring (coil spring) 18 having one end fixed to the inner end surface of the housing 23 has a ring-shaped shield member 24 attached to the other end.
The shield member 24 fits between the reed switch 13 and the permanent magnet 22 with the reed switch 13 at the center of the concentric circle.

Shield member when no acceleration is applied
24 is to prevent the magnetic field generated by the permanent magnet 22 from affecting the contact portion of the reed switch 13, but when the spring 18 is elastically deformed in the longitudinal direction of the reed switch 13 when a predetermined acceleration or more is applied, The magnetic field generated by the permanent magnet 22 acts on the contact portion, and the contact portion operates (closes or opens).
I will be.

[0013]

As described above, the magnetic acceleration sensor of the present invention for detecting whether or not the applied acceleration exceeds a certain value is less expensive than the conventional acceleration sensor, and has a smaller detecting device. There is an effect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic configuration example of a conventional acceleration sensor.

[Explanation of symbols]

 13 Reed switch 18 Spring 22 Permanent magnet 24 Shield member

Continuation of the front page (56) References JP-A-4-252962 (JP, A) JP-A-2-203276 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15 / 135 H01H 35/14

Claims (1)

(57) [Claims] A fixed reed switch;
A cylindrical permanent magnet that externally fits the contact point of the switch, and one end
Is fixed by the fixed spring and the applied acceleration.
Fixed to the other end of the spring elastically deformed in the
The reed switch is concentric between the switch and the permanent magnet.
And a cylindrical shield member that fits as the center of the spring.
Blocks the magnetism of the permanent magnet at the point and applies acceleration
When the spring is elastically deformed, the permanent magnet
The magnetic acceleration sensor moves to a position for operating the contact portion .