JPS61167869A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To realize simple structure, high reliability, and high density and to reduce errors due to temperature variation by providing a permanent magnet, alternating magnetic field generating means, and a magnetic detecting means, etc. CONSTITUTION:An alternating magnetic field is generated at right angles to a magnetic field established by the permanent magnet 2 by the excitation of a coil 6, and attractive force and resiliency operates alternately on the magnet 2. Consequently, the friction to the contact surface between the magnet 2 and a storage chamber 1a is only dynamic friction and when inertial force by acceleration operates, displacement in the direction is easy to occur. Then, the position of a magnet holding member 8 is adjusted to position the magnet 2 laterally. At this time, the ratio of right and left speed detection is normally equalized, so the position of the member 8 is adjusted so that the magnet 2 is in the center of the storage chamber 1a. In such a state, when detection signals detected by magneto-resistance elements 4 and 4 are regarded as references, the magnet 2 moves in proportional to the acceleration in the acceleration, so signals proportional to the movement extents are obtained from the detecting elements 4 and 4 and the acceleration is known from the differences from the references.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an acceleration sensor that detects acceleration of a moving body, and is used in, for example, an automobile.

(Conventional Example) Conventionally, as an acceleration sensor, for example, the
As shown in Japanese Patent No. 72, a movable iron core is supported within a housing via a mechanical support mechanism consisting of a spring, etc.
It is known that a differential transformer is used to detect the amount of displacement of this movable core in response to inertial force.

(Problems to be Solved by the Invention) However, in such a conventional example, since the movable iron core is supported by a mechanical support mechanism, the mechanical part is complicated and easily damaged, and the reliability of the acceleration sensor is There was a problem of inhibiting the

Accordingly, one object of the present invention is to solve the problems of the prior art described above and provide a highly reliable acceleration sensor.

(Means for Solving the Problems) Therefore, the gist of the present invention is to provide a permanent magnet movably housed in a storage case made of a non-magnetic material;
An acceleration sensor comprising an alternating magnetic field generating means for generating an alternating magnetic field orthogonal to the magnetic field of the permanent magnet, and a magnetic detecting means for detecting a magnetic change due to displacement of the permanent magnet in the vicinity of at least one magnetic pole of the permanent magnet. It is in.

(Function) Therefore, the permanent magnet rotates inside the storage case due to the alternating magnetic field, and the friction between the permanent magnet and the wall surface of the storage case is only dynamic friction, and the permanent magnet moves inside the storage case in response to changes in acceleration. It is possible to detect acceleration by detecting changes in the magnetic flux near the magnetic poles accompanying this movement, thereby achieving the above-mentioned problem.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

1 and 2, a first embodiment of the present invention is shown, in which an acceleration sensor has a storage case l made of a non-magnetic material, and a storage chamber la of the storage case 1 has a column-shaped permanent A magnet 2 is housed. The permanent magnet 2 is formed smaller than the storage chamber 1a so as to be movable in the acceleration direction when detecting acceleration. In addition, embedded grooves 3°3 are formed in the wall surfaces 1b, lb of the storage case l facing both end surfaces of the permanent magnet 2, and in the embedded grooves 3, 3, for example, a magnetoresistive element constituting magnetic detection means is formed. 4.4 is buried.

The storage case l is formed in a cylindrical shape, and a winding frame 5 is fitted around the outer periphery, and a coil 6 is wound around the winding frame 5. The terminal of this coil 6 is connected to an AC power source (not shown), and the winding frame 5 and coil 6 together with this AC power source constitute an alternating magnetic field generating means.

Support members 7,
7 are joined to each other. The support member 7.7 has screw holes 7a, 7 communicating with the opening surface 5at5b of the winding frame 5.
a is formed at the same position as the storage chamber 1a. A cylindrical magnet holding member 8 is screwed into this screw hole 7a.

The magnet holding member 8 has, for example, a cylindrical fitting hole 8a formed in one end surface, and positioning magnets 9, 9 are fitted into the fitting hole 8a. And the opening surface 5a of the positioning magnets 9,9.

The magnetic pole on the 5b side is arranged so as to be different from the closest magnetic pole of the permanent magnet 2.

On the other hand, a tool insertion groove 8b is formed in the other end surface of the magnet holding member 8, and a tool such as a screwdriver is inserted into this tool insertion groove 8b to rotate the magnet holding member 8, and a tool is inserted into the screw hole 7a. By moving the inside, the distance between the permanent magnet 2 and the positioning magnet 9 can be adjusted.

How to perform acceleration detection in the above configuration.

First, the coil 6 is excited by an AC power source (not shown). By excitation of the coil 6, an alternating magnetic field is generated in a direction perpendicular to the magnetic field generated by the permanent magnet 2.
Attractive force and repulsive force act alternately between the two. Therefore, the friction between the contact surface between the permanent magnet 2 and the storage chamber 1a is only dynamic friction, and if an inertial force due to acceleration (solid line arrow or dotted line arrow in Figure 1) acts, it is likely to be displaced in that direction. becomes. Next, the position of the magnet holding member 8 is adjusted to position the permanent magnet 2 in the lateral direction. Normally, the ratio of left and right speed detection is equal, so the permanent magnet 2 is located in the center of the storage chamber 1a. Adjust the position of the magnet holding member 8 as follows.

In this state, if the detection signals detected by the magnetoresistive elements 4, 4 are used as a reference, then during acceleration, the permanent magnet 2
Since it moves in proportion to the magnitude of acceleration, a detection signal proportional to the amount of movement is obtained from the magnetic detection elements 4, 4, and the acceleration can be determined from the difference from the reference.

In FIG. 3, a second embodiment of the present invention is shown, and in comparison with the first embodiment, a positioning magnet 9 is formed into an annular shape and embedded in a groove 10 provided on the outer periphery of the storage case l. The only difference is that the same parts are given the same numbers and the explanation will be omitted.

FIG. 4 shows a third embodiment, which differs only in that the annular positioning magnet 9 shown in the second embodiment is an electromagnet, and other parts are the same as in the first embodiment. Since it is the same as the example, the same number is given and the explanation is omitted.

FIG. 5 shows a fourth embodiment, in which, in comparison with the first embodiment, the positioning magnet 9 is replaced by a bolt 12, 12 made of a magnetic material.

They are screwed into screw holes 13, 13 provided near the magnetic poles of the permanent magnets 2 in the storage case 1. and,
Since a magnetic pole opposite to the magnetic pole of the permanent magnet 2 is generated at the end of the bolt 12.12 on the storage chamber 1a side, by adjusting the attractive force between these magnetic poles at the insertion position of the bolt 12.12, the permanent magnet This embodiment differs from the first embodiment in that the position of the magnet 2 is adjusted. Other identical parts will be given the same numbers and their explanation will be omitted.

In the above embodiment, the magnetic detection means is constructed using a magnetoresistive element, but other means such as a Hall element may also be used.

(Effects of the Invention) As described above, according to the present invention, the member that is displaced in response to acceleration is a permanent magnet, and this permanent magnet is installed inside the storage case, and the magnetic field of the permanent magnet is alternately perpendicular to the magnetic field of the permanent magnet. A magnetic field is applied to rotate the permanent magnet to facilitate displacement within the storage case.

Since the magnetic change in the vicinity of the permanent magnet during displacement is detected by a magnetoresistive element, the structure is simple and reliable, and furthermore, the output signals of the two magnetoresistive elements are of a differential type. This has the effect of providing high sensitivity and reducing errors with respect to temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an acceleration sensor according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view showing the same acceleration sensor as above, and FIG. 3 is a longitudinal cross-sectional view showing an acceleration sensor according to a second embodiment. FIG. 4 is a longitudinal sectional view showing the third embodiment, and FIG. 5 is a longitudinal sectional view showing the fourth embodiment. DESCRIPTION OF SYMBOLS 1... Storage case, 2... Permanent magnet, 4... Magnetic resistance element, 5... Winding frame, 6... Coil. 9...Positioning magnet 9.11...Electromagnet, 12.
··bolt. Figure 1 Figure 2 / 110 4 Z II
o't 0 801Figure 3

Claims (1)

[Claims] a permanent magnet movably housed in a storage case made of a non-magnetic material; an alternating magnetic field generating means for generating an alternating magnetic field orthogonal to the magnetic field of the permanent magnet; An acceleration sensor comprising: magnetic detection means for detecting magnetic changes due to displacement of a magnet.