JPH0674967A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor allowing simple and inexpensive constitution, and capable of detecting acceleration from a DC zone. CONSTITUTION:A ring type magnetic yoke 4 is externally coupled to the outer surface of a hollow cylindrical body 1 of nonmagnetic material, and the internal space of the body 1 is filled with damper oil 2. Also, a cylindrical magnet 3 is retained in such a way as slidable and coming to the predetermined position due to a magnetic attraction force for the yoke 4 in acceleration-free state. Furthermore, magnetic resistance elements 5a and 5b are fixed to both edges of the body 1, and connected to each other in series. Then, an output line Lo is led from the connection point of the elements 5a and 5b, while a power line Lv and a grounding line Lg are respectively led from the terminals of the elements 5a and 5b not at the side of the connection point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor, and more particularly to an acceleration sensor which has a simple structure and can be constructed at a low cost and which can detect acceleration in a DC region.

[0002]

2. Description of the Related Art Accelerometers are used for acceleration, vibration,
Used to detect shock. FIG. 3 is a sectional view of a main part of an example of a conventional acceleration sensor. This acceleration sensor 3
In 00, the two piezoelectric bodies 301 are fixed to both side surfaces of the pillar 304 standing upright on the base 303.
A weight 302 is fixed to 01. Base 303
When an acceleration is applied to, the positive pressure is applied to one of the two piezoelectric bodies 301 and the negative pressure is applied to the other due to the inertia of the weight 302. Therefore, the acceleration can be detected by taking the difference between the output voltages of the two piezoelectric bodies 301.

FIG. 4 is a sectional view of the main part of another example of a conventional acceleration sensor. In this acceleration sensor 400, the box 40
Two strain gauges 401 are fixed to both side surfaces of a beam 402 vertically extending from the inner upper surface of the beam No. 4, and a weight 402 is fixed to the lower end of the beam 402. When acceleration is applied to the box body 404, the beam 402 is bent by the inertia of the weight 403, and one of the two strain gauges 401 is compressed and the other is stretched. Therefore, the acceleration can be detected by taking the difference between the output voltages of the two strain gauges 401.

[0004]

In the conventional acceleration sensor 300, since the piezoelectric body 301 is used, a charge amplifier is required, and it is difficult to reduce the cost.
Further, there is a problem that accelerations in the DC region and the ultra low frequency region cannot be detected. On the other hand, the above conventional acceleration sensor 40
At 0, since the output of the strain gauge 401 is small, an amplifier is required, and there is a problem that it is difficult to reduce the cost. Therefore, an object of the present invention is to provide an acceleration sensor which has a simple structure and can be inexpensively constructed, and further can detect acceleration from a DC region.

[0005]

SUMMARY OF THE INVENTION An acceleration sensor according to the present invention is capable of moving one of a magnet and a magnetic yoke with respect to the other, and when a non-acceleration state occurs, a predetermined position is obtained by a magnetic attraction force between the two. Hold so as to calm down,
Further, the structure is characterized in that a magnetoelectric conversion element that magnetically detects a change in the positional relationship between the two and outputs an electric signal is provided.

[0006]

In the acceleration sensor according to the present invention, in the non-acceleration state, the magnet and the magnetic yoke settle in a predetermined stable positional relationship by the magnetic attraction force of both. When acceleration is applied, the positional relationship between the magnet and the magnetic yoke changes due to inertia. This change is magnetically detected by the magnetoelectric conversion element and output as an electric signal. Here, since a large output can be obtained from the magnetoelectric conversion element, an amplifier may be omitted, and the configuration is simplified and the cost can be reduced. Further, the positional relationship between the magnet and the magnetic yoke changes even with the acceleration in the DC region, and the change can be detected by the magnetoelectric conversion element, so that the acceleration can be detected from the DC region.

[0007]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a block diagram of an embodiment of the acceleration sensor of the present invention. In this acceleration sensor 100, a damper oil 3 is filled inside a non-magnetic hollow cylinder 1 whose both end surfaces are sealed, and a cylindrical magnet 3 is slidably inserted. A ring-shaped magnetic yoke 4 is fixedly provided on the outer circumference of the hollow cylinder 1. Further, magnetoresistive elements 5a and 5b are fixed to both end surfaces of the hollow cylinder 1, respectively. Magnetoresistive element 5
a and 5b are connected in series, and the output line L is connected from the connection point.
o has been derived. Furthermore, both magnetoresistive elements 5a, 5
A power supply line Lv and a ground line Lg are respectively derived from terminals not on the connection point side of b and are connected to the battery B. The size of the hollow cylinder 1 is, for example, about 12 mm in diameter × 12 mm in length.

Next, the operation of the acceleration sensor 100 will be described. FIG. 2 is an explanatory diagram of the positional relationship between the magnet 3 and the magnetic yoke 4 in the non-acceleration state. Due to the magnetic attraction of the magnet 3 and the magnetic yoke 4, the magnet 1
One of the magnetic poles is stable at a position close to the magnetic yoke 4. At this time, the magnetic potential energy between the two is the lowest.

When acceleration is applied, the positional relationship between the magnet 3 and the magnetic yoke 4 changes due to inertia, as shown in FIG. 1, and the magnetic potential energy between them increases. Then, the potential is stabilized at the position of potential energy that cancels the difference in the force applied to the magnet 3 and the magnetic yoke 4 caused by the acceleration.

That is, the magnet 3 moves according to the acceleration. The magnet 3 also moves with acceleration in the DC region. Then, since the magnet 3 approaches one of the magnetoresistive elements 5a and 5b and moves away from the other, the magnetoresistive element 5
The resistance values of a and 5b increase on the one hand and decrease on the other hand. Since the resistance values of the magnetoresistive elements 5a and 5b are differentially changed in this way, a large output can be obtained from the output line Lo without an amplifier.

The damper oil 2 appropriately suppresses the movement of the magnet 3. The maximum detectable acceleration can be freely designed depending on the strength and size of the magnetic force of the magnet 3, the magnetic permeability and size of the magnetic yoke 4, the distance between the magnetoresistive elements 5a and 5b, and the like.

[0012]

According to the acceleration sensor of the present invention, a large output can be obtained without an amplifier, so that the structure can be simplified and the cost can be reduced. Further, it becomes possible to detect even acceleration in the DC region and the ultra-low frequency region.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a positional relationship between a magnet 3 and a magnetic yoke 4 in a non-accelerated state.

FIG. 3 is a cross-sectional view of a main part of an example of a conventional acceleration sensor.

FIG. 4 is a sectional view of a main part of another example of a conventional acceleration sensor.

[Explanation of symbols]

 100 Accelerometer 1 Hollow cylinder 2 Damper oil 3 Magnet 4 Magnetic yoke 5a, 5b Magnetoresistive element Lo Output line Lv Power line Lg Ground line B Battery

Claims (2)

[Claims] 1. A magnet and a magnetic yoke, one of which is movable and the other of which is held so as to be settled at a predetermined position by a magnetic attraction force of both when it is in a non-acceleration state. An acceleration sensor comprising a magnetoelectric conversion element that magnetically detects a change in positional relationship and outputs an electric signal. 2. A ring-shaped magnetic yoke is attached to the outer periphery of a non-magnetic hollow cylinder whose both end faces are sealed, and a damper oil is filled in the inside of the cylinder, and a magnet for a column is attached. It is held so as to be slidable and returned to a predetermined position by a magnetic attraction force to the magnetic yoke when the tubular body is in an unaccelerated state, and further, on both end faces of the tubular body,
Magneto-resistive elements were fixed, the magneto-resistive elements were connected in series, the output line was derived from the connection point, and the power supply line and the ground line were derived from the terminals not on the connection point side of both magneto-resistive elements. Characteristic acceleration sensor.