JPH04344467A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor with an inspecting function whereby the normal action of the sensor is easily checked before use. CONSTITUTION:A magnetic fluid 11 is sealed in an annular case 10 formed of a nonmagnetic material and an annular permanent magnet 12 attached to the inside of the magnetic fluid 11 in its diametral direction is made to float and is then made still by utilizing the balance between the displacement force of the permanent magnet 12 due to acceleration and the resilient force of the magnetic fluid 11 concentrated in the attached portion of the permanent magnet 12 and this still position is detected by Hall elements 13-16 provided on the outer periphery of the case 10 and acceleration of an object to which the base 10 is fixed is detected. Electromagnetic coils 17, 18 are provided on the inner periphery of the case 10 and the permanent magnet 12 is displaced by transmission of electricity to the coils 17, 18 and the displacement is detected by the Hall elements 13-16 whereby actuation of an acceleration sensor can be readily recognized before the sensor is used.

Description

[Detailed description of the invention]

0001

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

0002

[Prior Art] Conventionally, this type of device has been used, for example, in Japanese Patent Application Laid-Open No.
-205775, inside a sealed cylindrical case made of non-magnetic material,
enclosing a magnetic fluid and placing a circular or annular radially magnetized permanent magnet in a floating state within the magnetic fluid;
The Hall element uses the balance between the displacement force of the permanent magnet due to the acceleration of the case and the repulsive force of the magnetic fluid concentrated in the magnetized part of the permanent magnet to keep the permanent magnet stationary, and this stationary position is provided on the outer periphery of the case. The case is designed to detect the acceleration of an object to which it is fixed by detecting it with a magnetically sensitive element such as a magnetic sensor.

0003

[Problems to be Solved by the Invention] In the above-mentioned conventional acceleration sensor, the sensor may not function properly due to reasons such as the permanent magnet not displacing normally or the magnetic sensing element not normally outputting a signal representing the position of the permanent magnet. It may not work properly. Therefore, when using this type of acceleration sensor, it is necessary to test whether the sensor is working properly before use, but the conventional acceleration sensor mentioned above does not have the above-mentioned testing function. There was a problem in that the reliability of the sensor was poor. The present invention has been made to address the above-mentioned problems, and its purpose is to provide an acceleration sensor with a normal operation inspection function.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention has a case that is made of a non-magnetic material and has a sealed space therein, and An acceleration sensor comprising a magnetic fluid sealed in a magnetic fluid, a permanent magnet placed in a floating state within the magnetic fluid, and a magnetic sensing element provided outside the case to detect displacement of the permanent magnet, An electromagnetic coil that displaces the permanent magnet when energized is provided near the case.

[0005]

[Operations and Effects of the Invention] In the present invention configured as described above, when the electromagnetic coil is energized before using the acceleration sensor, the permanent magnet can be displaced by the electromagnetic force of the magnet. A signal corresponding to the displacement of the permanent magnet can be extracted from the magnetically sensitive element. This allows you to confirm the normal displacement of the permanent magnet and the normal operation of the magnetic sensing element, making it easy to test whether the acceleration sensor is working properly before using it. , the reliability of the sensor is improved.

[0006]

[Embodiment] An embodiment of the present invention will be explained below with reference to the drawings. Fig. 1 shows the external appearance of an acceleration sensor according to the embodiment, and Fig. 2 shows a cross section of the sensor. Moreover, FIG. 3 shows the same sensor in a longitudinal section.

This acceleration sensor includes a case 10 which is formed into an annular shape from a non-magnetic material such as aluminum and has a sealed annular space inside the case 10. Projections 10a to 10d extending in the radial direction at 90 degree intervals are integrally formed on the inner bottom surface of the case 10. In the annular space of the case 10, a magnetic fluid 11 in which ultrafine particles such as manganese zinc ferrite are dispersed in isoparaffin is sealed, and a permanent magnet 1 formed in an annular shape is enclosed.
2 is incorporated in a suspended state within the magnetic fluid 11. This permanent magnet 12 is magnetized in the radial direction every 90 degrees, and each magnetized pole is located between each of the protrusions 10a to 10d of the case 10.

Hall elements 13 to 16 constituting a magnetically sensitive element are fixed on the outer periphery of the case 10 at positions facing each magnetized pole of the permanent magnet 12. A voltage signal approximately proportional to the distance from the permanent magnet 12 is outputted via the lead wires 13a to 16a. Further, electromagnetic coils 17 and 18 are provided on the inner circumference of the case 10, facing each magnetized pole of the permanent magnet 12, and the electromagnetic coils 17 and 18 are connected to the lead wire 17.
18a and 18a. The electromagnetic coils 17 and 18 are fixed to the case 10 by a support member (not shown) made of a non-magnetic material.

In the acceleration sensor according to the present embodiment as described above, the case 10 is formed into an annular shape, and the Hall elements 13 to 16 are provided on the outer circumference of the case 10, and the electromagnetic coils 17 and 18 are provided on the inner circumference of the case 10. Since the sensor is provided, the entire sensor device can be configured compactly.

On the other hand, before using the acceleration sensor according to this embodiment configured as described above, in order to inspect the sensor, lead wires 17a and 18a are connected to the electromagnetic coils 17 and 18.
energize each via. If the permanent magnet 12 is in a state of normal displacement, the energization of the electromagnetic coil 17 causes the permanent magnet 12 to be displaced to the right or left in FIG. 2, and the energization of the electromagnetic coil 18 causes the permanent magnet 12 to move upward in FIG. Or displaced downward. In this case, since the density of the magnetic fluid 11 is high in the vicinity of each magnetized pole of the permanent magnet 12, the magnetic fluid 11 is elastic against the displacement of the permanent magnet 12 due to the energization of the electromagnetic coils 17 and 18. acts as a reaction force,
The permanent magnet 12 comes to rest at a position corresponding to the amount of current applied to the electromagnetic coils 17 and 18. If the Hall elements 13 to 16 are normal, each Hall element 13 to 16 is connected to the lead wire 13.
A signal corresponding to the amount of current applied to the electromagnetic coils 17 and 18 is outputted via a to 16a, respectively.

On the other hand, if the acceleration sensor is not able to operate normally because the permanent magnet 12 cannot be displaced normally or the Hall elements 13 to 16 are not operating normally, the electromagnetic Due to the energization of the coils 17 and 18, the Hall elements 13 to 16 do not output signals corresponding to the amount of energization of the electromagnetic coils 17 and 18 via the lead wires 13a to 16a, respectively. As a result, if the relationship between the amount of current applied to the electromagnetic coils 17 and 18 and the detection signals from the Hall elements 13 to 16 when the acceleration sensor is normal can be determined in advance, it is possible to confirm that the acceleration sensor is normal before using the sensor. You can easily check whether it is working or not.

When using an acceleration sensor that has passed the above inspection, the bottom or top surface of the case 10 is fixed to an object. This causes the object to move through the Hall elements 13 and 15.
When acceleration is applied in a straight line connecting the two, the permanent magnet 12 is displaced in the same direction and the opposite direction with respect to the case 10, and the case 12 is moved at a position where the force proportional to the acceleration and the reaction force of the magnetic fluid 12 are balanced. Stand still for 10. Then, the Hall elements 13 and 15 detect the stationary position of the permanent magnet 12 and output a signal proportional to the acceleration of the object in a straight line connecting both elements 13 and 15. On the other hand, the object is the Hall element 14,
16, the permanent magnet 12 is displaced in the same direction and the opposite direction, and the case 1 is moved at a position where the force proportional to the acceleration and the reaction force of the magnetic fluid 12 are balanced.
Stand still relative to 0. Then, the Hall elements 14 and 16 detect the rest position and output a signal proportional to the acceleration of the object in a straight line connecting both the elements 14 and 16. As a result, by taking the vector sum of both detected accelerations, the acceleration of the object within the plane to which the permanent magnet 12 belongs can be detected.

[0013] Furthermore, a rotational force may be generated in the object within the plane to which the permanent magnet 12 belongs. In this case, the permanent magnet 12 tries to rotate with respect to the case 10 in the opposite direction to the rotation direction, but since the magnetic fluid 11 is concentrated near each magnetized pole of the permanent magnet 12 as described above, this Dense magnetic fluid 11 and protrusions 10a located on both sides thereof
Rotation of the permanent magnet 12 is prevented by the repulsive action of the magnet 10d. This improves the detection of the acceleration.

Furthermore, when the acceleration sensor is applied to a vehicle, the Hall elements 13 and 15 (or the Hall elements 14,
16) If the case 10 is fixed to the vehicle body so that the straight line connecting Hall elements 13 and 15 (or Hall elements 14 and 16) is fixed to the vehicle body, the permanent magnet 12 will move along the straight line connecting Hall elements 13 and 15 (or Hall elements 14 and 16) according to the longitudinal acceleration of the vehicle. Displace the top. Further, the permanent magnet 12 moves the Hall element 1 according to the lateral acceleration of the vehicle.
4 and 16 (or Hall elements 13 and 15). In this case as well, the permanent magnet 12 comes to rest at a position where the force proportional to each of the accelerations and the reaction force of the magnetic fluid 12 are balanced, and this resting position is maintained by the Hall elements 13 to 12.
16 detects. Therefore, by applying the acceleration sensor of the above embodiment, the longitudinal acceleration and lateral acceleration of the vehicle can be easily and independently extracted.

[0015] In the above embodiment, two orthogonal
Although an example has been described in which acceleration in one direction can be detected, if it is sufficient to detect acceleration in one direction, the permanent magnet 12 is magnetized at a pair of opposite locations, and the Hall element 13 is .about.16, only a pair of opposing Hall elements may be used. Also, in this case,
It is sufficient to use only one of the electromagnetic coils 17 and 18 facing the Hall element.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the appearance of an acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional plan view of the acceleration sensor of FIG. 1;

FIG. 3 is a longitudinal sectional front view of the acceleration sensor taken along line 3-3 in FIG. 2;

[Explanation of symbols]

10... Case, 11... Magnetic fluid, 12... Permanent magnet, 13
~16... Hall element, 17, 18... Electromagnetic coil.

Claims (1)

[Claims] 1. A case made of a non-magnetic material and forming a sealed space inside, a magnetic fluid sealed in the case, and a permanent magnet placed in a floating state within the magnetic fluid. and a magnetic sensing element provided outside the case to detect displacement of the permanent magnet, characterized in that an electromagnetic coil for displacing the permanent magnet when energized is provided near the case. acceleration sensor.