JPH0638403Y2 - Permanent magnet for G sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Field of the Invention >> The present invention relates to a permanent magnet suitable for a G sensor for detecting acceleration.

<Prior art and its problems> It is a well-known fact that the number of car accidents has been increasing and the eradication of accidents has become a major social problem. A sudden start as one of the causes of the accident or the cause of the accident,
It is a fact that there are many cases of reckless driving such as sudden braking and sharp turning of the left and right steering wheels. Since such reckless driving damages the vehicle, it goes without saying that it should be avoided as much as possible.

Then, when the reckless driving as described above is performed, a sudden acceleration, that is, G is applied to the vehicle. Conventionally, various G sensors for detecting such acceleration have been developed and put into practice. For example, as one of them, there is a piezoelectric element type G sensor, but since this G sensor requires an amplifier circuit, a discrimination circuit, etc., the cost is high and it is not possible to detect a low frequency region. There was a problem that it was not suitable as a G sensor.

In addition, recently, a ramp is arranged opposite to the housing, and a steel ball is rollably arranged in the central recess of the housing.When a sudden acceleration is applied, the steel ball rolls on the ramp and the limit switch Configured to output a signal upon contact with the G
A sensor has also been developed, but in this case, when the vehicle climbs a steep slope or runs on a bumpy road, it is in a state where no sudden acceleration is applied. Since a steel ball rolls on a slope and comes into contact with a limit switch to erroneously detect an acceleration, a malfunction occurs, which is unreliable and is not configured as a small and compact body. I couldn't say it was appropriate.

The present inventor has made various studies in view of the above-mentioned conventional techniques, but until the present invention, a leaf spring provided with a weight in the center of the housing was hung vertically, and a limit switch or a reed switch was arranged on both sides of the leaf spring. I made a prototype of the installed G sensor.

However, in such a configuration, since the acceleration is detected by using the vibration of the leaf spring, it is extremely difficult to adjust the elastic force of the leaf spring, and if the leaf spring is too strong, accurate acceleration can be detected. If it is not possible, and if it is too weak, it will react to even minute accelerations and become over-detected, and vibration will not stop immediately, resulting in unstable operation and lack of reliability. Furthermore, before returning from the accelerated G to the original G It was discovered that it takes too much time.

Therefore, the present inventor arranges a pair of rod-shaped permanent magnets rollably in a box-shaped housing made of a non-magnetic material such as plastic, and opens and closes outside the both side walls of the housing by the magnetic flux of the permanent magnets. We developed a G sensor with a pair of reed switches.

According to such a structure, when the pole-like permanent magnets are arranged so as to face each other with the poles aligned, both magnets are pressed against both sides of the housing by the repulsive force, while maintaining a stationary state.
When a sudden acceleration is applied, this repulsive force is overcome and one of the magnets rolls in the housing due to its inertial force, and the magnetic flux of that magnet does not reach the reed switch, turning the reed switch on and off. Can be controlled.

That is, the G sensor developed by the present inventor uses the repulsive force of the permanent magnet to maintain the stationary state, while the inertial force is used to roll the magnet to control the on / off of the reed switch. , If the permanent magnet used for this sensor is composed of a conventionally known alnico magnet and the permanent magnets are arranged opposite to each other in the housing, it is experimentally found that the magnetic force is rapidly demagnetized or demagnetized with the passage of time. When a G sensor is constructed using such a permanent magnet, the magnetic flux range of the G sensor changes abruptly, so that the reed switch cannot be accurately turned on and off.
Therefore, it has been found that accurate acceleration cannot be detected, and there are problems such as lack of operational stability.

<The purpose of the device> This device was made in view of the above problems.
An object of the present invention is to provide a G sensor having excellent operation reliability by providing a permanent magnet that does not demagnetize or demagnetize even when rod-shaped permanent magnets are arranged opposite to each other in the housing. .

<< Constitution and Effect of the Invention >> In order to achieve the above-mentioned object, the present invention is arranged in a box-shaped housing made of a non-magnetic material such as plastic so as to be opposed to each other, and is disposed outside both sides of the housing. A permanent magnet for a G sensor, which opens and closes a reed switch by magnetic flux, wherein a rod-shaped magnetic body obtained by compression-molding magnetic powder of samarium cobalt is sliced to obtain a plate-shaped magnetic body. A large number of magnetic bodies are laminated to form a magnetic body unit, and the magnetic body unit is filled in an outer cylinder made of non-ferrous metal, and both ends of the outer cylinder are resin-molded.

In the present invention, as described above, the outer cylinder is filled with the magnetic body unit molded from the magnetic powder of samarium cobalt, so that the characteristics of samarium cobalt, that is, demagnetization or non-demagnetization, are utilized to the maximum extent. It is possible,
Therefore, even when the rod-shaped permanent magnets are arranged opposite to each other in the housing, they are not demagnetized or demagnetized, so that it is possible to provide a G sensor having excellent operation reliability.

Also, samarium cobalt has a characteristic of being weak against impact, but since the outer circumference of the magnetic body unit made of samarium cobalt is protected by the outer cylinder made of non-ferrous metal, permanent magnets collide with each other or side walls of the housing and other parts. Even if it collides with an object, it will not be damaged in any way,
Since the outer cylinder itself is highly durable and has a mass, it has the effect of being able to detect acceleration more accurately.

Further, according to the present invention, a bar-shaped magnetic body is sliced to obtain a plate-shaped magnetic body, and a large number of the plate-shaped magnetic bodies are laminated to form a magnetic body unit. The length can be arbitrarily changed, and therefore, the degree of freedom in design and usability are improved.

<< Explanation of Embodiments >> A rod-shaped permanent magnet according to the present invention is shown in FIG.
Indicates an outer cylinder made of non-ferrous metal, such as brass, and the outer cylinder 10 is filled with a magnetic body unit 11 made of magnetic powder of samarium cobalt. That is, this samarium-cobalt powder has the property of being demagnetized when high heat is applied, but it has the property of not being demagnetized or demagnetized by normal heat, and has the property of being weak against impact. Then, this magnetic powder is compression-molded to form a rod shape, and this is sliced thinly to form a plate-shaped magnetic body 11a, and a large number of these are laminated to form the magnetic body unit 11,
The magnetic body unit 11 is filled in the outer cylinder 10, and the outer cylinder 10
Both ends of the resin are resin-molded with an epoxy resin 12 or the like to form the permanent magnet of the present application.

As shown in FIG. 2, the obtained permanent magnet has a pair of rod-shaped permanent magnets 21, 21 having the above-described structure, which are rollably opposed to each other in a box-shaped housing 20 made of a non-magnetic material such as plastic. A pair of reed switches 22, which are opened and closed by the magnetic flux of the permanent magnets 21, 21 outside the both sides of the housing 20.
22 is arranged.

Therefore, according to the present invention, even if the permanent magnets are arranged facing each other, they are not demagnetized or demagnetized at all due to the passage of time, etc., so that the magnetic flux can always be spread within a certain range. Therefore, since the reed switch can be accurately controlled to be turned on and off, a G sensor having excellent operation reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a permanent magnet according to the present invention, FIG. 2 is a plan view of a G sensor using the permanent magnet of the present invention, and FIG. 3 is a longitudinal sectional view of the same. 10 …… Outer cylinder 11 …… Magnetic substance unit 11a …… Magnetic substance 20 …… Housing 21 …… Rod-shaped permanent magnet 22 …… Reed switch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-50-37476 (JP, A) JP-A-52-120400 (JP, A) Actually open 58-172376 (JP, U) Actual-open Sho-54- 36100 (JP, U) Actually opened Sho 58-170808 (JP, U) Japanese Patent Sho 60-9328 (JP, B2)

Claims (1)

[Scope of utility model registration request] 1. A permanent magnet for a G sensor, which is arranged in a box-shaped housing made of a non-magnetic material such as plastic so as to face each other and which opens and closes a pair of reed switches arranged outside both sides of the housing by magnetic flux. Then, a rod-shaped magnetic body obtained by compression-molding magnetic powder of samarium-cobalt is sliced to obtain a plate-shaped magnetic body, and a plurality of plate-shaped magnetic bodies are laminated to form a magnetic body unit. A permanent magnet for a G sensor, characterized in that the magnetic body unit is filled in an outer cylinder made of non-ferrous metal, and both ends of the outer cylinder are resin-molded.