JPH0371060A - Acceleration sensor - Google Patents

Abstract

PURPOSE: To generate an extending narrow and effective magnetic field with concentrated magnetic fluxes by constituting a sensor magnet by at least two permanent magnets and directing their magnetic polarities parallel to each other toward a Hall element. CONSTITUTION: An acceleration sensor 11 which is provided with a plate spring 15 of which one side is tightened tightly and a sensor magnet fixed on the free end part of the spring 15 that is directed toward the Hall element 20 side, is formed of at least two permanent magnets 18 and 19. These magnets almost parallel to each other are extended toward the direction of the Hall element 20. In addition, the magnetic polarities of the magnets 18 and 19 are oriented in the opposite direction to each other. Further the free end part 16 of the spring 15 is arranged between the magnets 18 and 19. Thus, the extending narrow and effective magnetic field with concentrated magnetic fluxes can be obtained. This magnetic field can give a large Hall voltage signal through small change in the spring 15. Therefore a high rigidity can be given to the spring 15, reducing the possibility of breakage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention includes a leaf spring that is tightened on one side, and a sensor magnet directed toward the Hall element is fixed to the free end of the leaf spring. Regarding acceleration sensors.

[Conventional technology]

In acceleration sensors of this type, the polarity of the permanent magnet is either oriented perpendicularly to the surface of the leaf spring or parallel to the Hall element. Although this results in a relatively large effective flux width, it produces only a relatively small Hall voltage, especially if the displacement of the leaf spring is small. Also, the permanent magnet must be fixed to the leaf spring using expensive adhesive.

[Problem of invention]

The object of the present invention is therefore to eliminate this drawback.

[Means to solve the problem]

According to the present invention that solves this problem, the sensor magnet is separated from at least two permanent magnets, and the magnetic polarities of these permanent magnets extend substantially parallel to each other toward the Hall element. , the magnetic polarities of these permanent magnets are oriented in opposite directions.

〔effect〕

The acceleration sensor according to the invention has the advantage of producing a narrow effective magnetic field in which the magnetic flux lines extend in a concentrated manner. Stray magnetic fields are relatively small. This magnetic field generates relatively large Hall voltage signals even with small strokes, ie small displacements of the leaf spring. This allows the leaf spring to have a high stiffness, so that the risk of the leaf spring breaking is reduced. Good drop resistance can be obtained even when the acceleration sensor is intentionally dropped from a slight height during manufacturing. Also, the risk of breakage is avoided when the spring is subjected to a sustained load. Since the leaf spring is placed between the two magnets and is pulled against each other, the load at the bonding point between the magnet and the leaf spring is reduced. Therefore, simpler and cheaper adhesives can be used.

[Example] Next, the configuration of the present invention will be specifically explained with reference to an example shown in the drawings. FIG. 1 shows a housing lO of an acceleration sensor 11, in which a thick layer -
or a base plate with evaluation electronics 13 for the acceleration sensor 11, manufactured in thin-layer technology) 12
is located. A web 14 extends perpendicularly above this base plate 12, to which a leaf spring 15 is fixed, in particular by spot welding. The leaf spring 15 is arranged parallel to the base plate 12 in the longitudinal direction, has a lower edge extending substantially parallel to the base plate 12, and has an upper edge extending obliquely downward. An extension 16 is provided at the free end of the leaf spring 15. Of course, other shapes of leaf springs are also possible.

In the shape of the leaf spring 15 according to the illustrated embodiment, the leaf spring 15 is prevented from rotating about its longitudinal axis.

One permanent magnet 18, 19 is in each case fixed by adhesive on both wide sides of the extension part (6). The polarities of the two permanent magnets 18 and 19 are opposite to each other,
It is oriented parallel to the plane of the leaf spring 15. A Hall sensor (Hall element) 20 is fixed on the base plate 12, facing the permanent magnets 18 and 19.

Furthermore, an eddy current disk 22 is arranged at the free end of the leaf spring 15, which eddy current disk 22 is approximately rectangular in design and extends horizontally in a direction perpendicular to the leaf spring 15. ing. The eddy current disk 22 penetrates into a cage-shaped flux guiding member 23, which is preferably made of a flexible magnetic material.

Two rectangular parallelepiped-shaped brake magnets 24 are arranged within the magnetic flux guide member 23 at a distance from each other, and the brake magnets 24 extend toward the eddy current disk 22. It is not in contact with plate 2. The width of the magnetic flux guiding member 23 is slightly larger than the width of the eddy current disk 22, so that the eddy current disk 22 can reciprocate within the magnetic flux guiding member 23 without difficulty. However, permanent magnet 18.
19 can also be arranged in such a way that it simultaneously acts as a brake magnet.

FIG. 2 shows magnetic flux lines 27 extending between the poles of two permanent magnets 18,19. Since this line of magnetic flux 27 extends from the north pole to the south pole, a magnetic flux is formed between the two permanent magnets via the extension 16 and each permanent magnet 18.1
A mutually extending magnetic flux is formed from each type of 9. However, in this case the effective magnetic flux width is the same as that of the two permanent magnets 18.
It is defined by the magnetic flux extending between the 19 poles, whereas the other magnetic fluxes can be characterized as somewhat stronger than the stray magnetic field.

The eddy current disk 22 cooperates with the flux guiding member 23 and the brake magnet 24 to form an eddy current brake. Since the brake magnets 24 are magnetized in opposite directions, the magnetic flux is highly inhomogeneous in the air gap between the eddy current disk 22 and the brake magnet 24 according to this mutually opposite magnetization, resulting in eddy currents. During the reciprocating vibration of the current disk 22, generation of eddy current is required. The acceleration sensor 11 is arranged, for example, at right angles to the traveling direction of the vehicle.

The acceleration sensor 11 is arranged, for example, at right angles to the traveling direction of the vehicle. Leaf spring 15, permanent magnets 18, 19,
and a mass in the form of an eddy current disk 22 at the end of the leaf spring 15 is displaced in proportion to the acceleration acting at right angles to the leaf spring 15. This displacement is further defined by the spring constant of the leaf spring 15 and the mass. The measurement signal is generated by the movement of the magnetic flux 27 within the Hall sensor 20. Hall sensor 20 due to changes in magnetic flux
A voltage is induced within. Unlike conventionally known acceleration sensors, the effective width of the magnetic flux 27 is smaller than the width of the Hall sensor 20. In contrast, in conventional solutions, the effective width of the magnetic flux was larger than the width of the Hall sensor. According to the invention, therefore, even small displacements of the leaf spring 15 cause a change in the magnetic flux 27 within the range of the Hall sensor 20. Therefore, it is possible to measure a small stroke with a spring constant like that of a leaf spring. The damping of the movement of the leaf 15 due to the eddy current brake is caused by the eddy current disc 22 in the air gap of the magnet circuit.
This is done through the exercise of Vibration energy is dissipated by eddy currents induced during vibration. The respective desired damping can be achieved by correspondingly configuring the leaf spring-magnet circuit system.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an acceleration sensor according to an embodiment of the present invention, and FIG. 2 is a perspective view showing details of a leaf spring and a permanent magnet.

Claims (1)

[Claims] 1. A leaf spring (15) is provided with one side tightened, and a sensor magnet directed toward the Hall element (20) is fixed to the free end of the leaf spring (15). Acceleration sensor (11)
wherein the sensor magnet comprises at least two permanent magnets (18, 19), the magnetic polarities of these permanent magnets extending substantially parallel to each other in the direction of the Hall element (20), and These permanent magnets (18,
19) An acceleration sensor characterized in that the magnetic polarities of the elements are oriented in opposite directions. 2. Claim 1, wherein the free end (16) of the leaf spring (15) is arranged between two permanent magnets (18, 19).
Acceleration sensor listed.