JP2626055B2 - Acceleration sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration caused by movement of an object.

2. Description of the Related Art As a conventional acceleration sensor, a sensor as disclosed in Japanese Patent Application Laid-Open No. 63-148168 has been known. In this configuration, a ferromagnetic fluid is sealed in an airtight container, a magnetic sphere is placed on the object, and this magnetic sphere is held by a holding coil. When acceleration is applied to the magnetic sphere, it is provided outside the container. The acceleration detection is performed by detecting a change in magnetic permeability based on the displacement of the magnetic fluid caused by the displacement of the magnetic sphere by the excitation coil and the detection coil.

Problems to be Solved by the Invention However, in the above-described configuration, since a change in the magnetic permeability of the ferromagnetic fluid is detected, a magnetic fluid having a high saturation magnetization is required.

The present invention solves the above-mentioned conventional problems, and provides an acceleration sensor with high sensitivity.

Means for Solving the Problems In the present invention, a spherical moving magnet having a magnetic fluid adhered therein is enclosed in a chamber having a spherical curved surface, and a magnet for holding the moving magnet is provided outside the chamber. Along with
In order to detect the movement of the moving magnet, an acceleration sensor is constituted by three pairs of magnetic sensing elements such that their axes are perpendicular to each other.

Operation According to the above-described configuration, the moving magnet is disposed in a fluid lubricated state with respect to the curved surface in the room via the magnetic fluid, and when acceleration is applied to the acceleration sensor, the magnet moves, and the magnetic sensing element detects a change in the magnetic field due to the acceleration. This is for detecting and detecting acceleration.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes an acceleration sensor. Numeral 2 denotes a spherical moving magnet, with one hemisphere magnetized at the N pole and the other hemisphere magnetized at the S pole. Reference numeral 1 denotes a magnetic fluid attached so as to surround the magnet. The magnet 2 is located inside a main body 4 made of a non-magnetic material, and is arranged in a spherical chamber 5. The spherical chamber 5 is sized to be completely filled with the magnetic fluid 3.

Reference numeral 6 denotes an annular holding magnet arranged outside the chamber 5. This magnet 6 is magnetized on one side with an N pole and the other side with an S pole.

7x, 7x 'are proportional MR elements arranged on the xx' axis in a horizontal plane passing through the center of the chamber 5, 7y, 7y 'pass through the center of the chamber 5,
Proportional MR placed on yy 'axis perpendicular to xx' axis in horizontal plane
The elements 7z and 7z 'pass through the center of the chamber 5 and the xx' axis and y
This is a proportional MR element disposed on the zz 'axis perpendicular to the y' axis.

FIG. 3 shows a circuit 10 for a proportional MR element 7x as an example. 11 is DC power supply, 12x is operational amplifier, 1
3x is an output terminal. Other proportional MR elements use similar circuits for 7x 'to 7z'.

FIG. 4 is a block diagram showing the processing contents of the signal processing unit 14. 13x, 13x ', 13y, 13y', 13z, 13
z ′ are proportional MR elements 7x, 7x ′, 7y, 7y ′, 7z, 7z ′, respectively.
Is the output corresponding to 15x, 15y, and 15z are differential amplifiers, respectively, and 16x, 16y, and 16z are acceleration calculation results in x, y, and z directions, respectively.

 Next, the operation will be described.

FIG. 1 shows a state in which no acceleration is applied to the acceleration sensor 1.

The moving magnet 2 causes the surrounding magnetic fluid 3 to adhere to the entire surface by the magnetic field. Thereby, the magnet 2 becomes the magnetic fluid 3
Floating state. In the vertical direction, the gravity of the magnet 2, its buoyancy and the magnetic force of the holding magnet 6 are balanced and held at the center of the chamber 5. At this time, the direction of the magnetic pole of the magnet 2 is stabilized by the action of the magnetic field of the magnet 6 such that the magnetic pole in the direction opposite to the magnetic pole of the magnet 6 in the vertical direction is arranged. That is, in FIG. 1, the magnetic pole of the magnet 2 is an N-pole above and a S-pole below the holding magnet 6, while the pole above the holding magnet 6 is an N pole. Stabilizes in the state of coincidence with the ZZ 'axis. In the direction other than the vertical direction, if the center of the magnet 2 tries to deviate from the center of the chamber 5, asymmetry occurs in the magnetic flux in the magnetic fluid 3, so that a restoring force for returning to the center acts. That is, by these actions, the magnet 2 is held at the center of the chamber 5.

In this state, the outputs 13x of the proportional MR elements 7x and 7x '
13x ', outputs 13y and 13y' of proportional MR elements 7y and 7y ', and outputs 13z and 13z' of proportional MR elements 7z and 7z ', respectively. That is, the outputs of the differential amplifiers 15x, 15y, and 15z do not occur, and the accelerations 16x, 16y, and 16z in the x, y, and z directions have zero output.

Next, it is assumed that acceleration α is applied to the acceleration sensor. As shown in FIGS. 5 and 6, the projection vector of this acceleration on the vertical section is αxz, and the projection vector on the horizontal section is αx
Let it be y.

At this time, a force in a direction opposite to the acceleration α acts on the magnet 2,
The magnet 2 moves in a direction opposite to the direction of the acceleration. As a result, the output 13x 'of the proportional MR element 7x' becomes larger than the output 13x of 7x. The output 13y 'of the proportional MR element 7y'
Becomes larger than the output 13y of 7y. Also, the proportional MR element 7
The output 13z 'of z' is larger than the output 13z of 7z. Based on these outputs, outputs of the differential amplifiers 15x, 15y, and 15z are generated, and accelerations in the x, y, and z directions, 6x, 16y, and 16z are obtained.

Since these outputs are generated in proportion to the amount of movement of the magnet 2 from the center, acceleration of any magnitude can be measured.

When the magnet 2 moves when an acceleration is applied, the magnetic pole of the magnet 2 moves while maintaining its direction in the vertical direction due to the magnetic field of the holding magnet 6, and becomes unstable due to the unstable rotation of the magnet 2. No reproducibility of the operation is assured since no significant output is produced.

Further, when the acceleration stops being applied, the asymmetry of the magnetic flux in the magnetic fluid 3 around the magnet 2 becomes a restoring force as described above, and the magnet 2 returns to the center of the chamber 5.

 Next, a second embodiment will be described.

FIG. 7 is a diagram in which the holding magnet 6 in FIG. 1 is replaced with an electromagnet 17 formed by a current coil, and the other configuration is the same as FIG.

In FIG. 8, reference numeral 18 denotes a control circuit for the electromagnet 17;
Is a DC power supply, 20 is a variable resistor, and 21 is a switch.

 Next, the operation will be described.

The switch 21 is turned on to excite the electromagnet 17 so that the upper part becomes the S pole and the lower part becomes the N pole in FIG. The operation of detecting the acceleration in such a state is exactly the same as that shown in the first embodiment. In this case, the strength of the electromagnet 17 can be adjusted by adjusting the variable resistor 20. This enables fine adjustment of the initial position of the magnet 2.

In this embodiment, the state in which the moving magnet is the center of the room as the initial position has been described.However, even if the initial position is deviated from the center, the acceleration difference can be calculated based on the output difference of the proportional MR element at that time. Detection is possible.

Also, an example in which a proportional type MR element is used as the magnetic field detecting means of the moving magnet has been described, but other means may be used as long as the magnetic field change can be continuously detected. For example, an excitation coil and a detection coil may be integrated.

Effects of the Invention As described above, the present invention has the following effects.

(1) A three-dimensional acceleration sensor with high sensitivity because a spherical moving magnet with a magnetic fluid adhered is enclosed in a room having a spherical curved surface and a magnetic field change due to the movement of the magnet is detected. Became possible.

(2) The initial position of the moving magnet can be finely adjusted by using an electromagnet as the holding magnet.

[Brief description of the drawings]

1 is a longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA 'of FIG. 1, FIG. 3 is a circuit diagram of a proportional MR element, and FIG. 5 is a longitudinal sectional view showing a different operation state of FIG. 1, FIG. 6 is a sectional view taken along the line BB 'of FIG. 5, FIG. 7 is a longitudinal sectional view showing a second embodiment of the present invention, FIG. 8 is a control circuit diagram of the electromagnet. 1 ... acceleration sensor, 2 ... magnet for movement, 3 ... magnetic fluid, 5 ... chamber, 6 ... magnet for holding, 7x, 7x ', 7y, 7y', 7
z, 7z ': Proportional MR element (magnetic sensing element); 17: Electromagnet.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-163972 (JP, A) JP-A-63-149568 (JP, A) JP-A-63-148168 (JP, A) JP-A-63-148168 153474 (JP, A) JP-A-60-143781 (JP, A) JP-A-1-202670 (JP, A) JP-A-2-138875 (JP, A) JP-A-2-90061 (JP, A) JP-A-2-205775 (JP, A) JP-A-63-151862 (JP, A) JP-A-2-212709 (JP, A) JP-A-63-218814 (JP, A) (JP, U)

Claims (3)

(57) [Claims] 1. A spherical moving magnet having a magnetic fluid adhered therein is sealed in a chamber having a spherical curved surface, and a holding magnet for the moving magnet is arranged outside the chamber. An acceleration sensor in which three pairs of magnetic detecting elements for detecting the movement of the moving magnet are arranged such that their axes are perpendicular to each other. 2. The acceleration sensor according to claim 1, wherein said holding magnet comprises a permanent magnet. 3. The acceleration sensor according to claim 1, wherein said holding magnet comprises an electromagnet.