JPS63298070A - Acceleration detector - Google Patents

Abstract

PURPOSE:To detect a displacement quantity with a light signal and to detect small acceleration with high accuracy by providing a means which displaces a base member relatively according to acceleration applied to the base member and a photodetecting means which photodetects light from a light projecting means, and connecting one-terminal sides of the projecting and photodetecting means to a displaying means and the other-terminal sides to the base member. CONSTITUTION:When acceleration is applied to an acceleration detecting device, a force proportional to the value of the acceleration is generated at a weight 4 and the whole of a cantilever beam 1 is stressed. The cantilever beam 1 is displaced by the stress. Then a point irradiated with light from one terminal of an optical fiber 4 moves on the photodetection surface of a detection element 6 according to the displacement of the beam 1. Phototransistors as thin film semiconductors form a 256X256 plane matrix on the photodetection surface of a detecting element 6. Then the detecting element 6 converts the point irradiated from one end of the optical fiber 4 into a binary code of 8X8-bit code which is outputted. Namely, the detecting element 6 outputs the acceleration and direction as binary codes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an acceleration detection device that detects acceleration.

(Prior Art) As a conventional acceleration detection device, an acceleration detection device as shown in FIG. 7 is known.

In the acceleration detection device shown in FIG. 7, one end of a beam 1 is fixed to a fixed member J to form a single beam 1, and a weight 3 is fixed to the free end of this cantilever beam 1. Furthermore, a strain gauge 16 is fixed to one side of the beam 1 for converting strain generated in the beam 1 due to acceleration into an electrical signal. Furthermore, although not shown, the strain gauge 16 is provided with an electrode for fixing a conducting wire 17, and an electrical signal is extracted from this electrode via the conducting wire 17.

Such an acceleration detection device is disclosed in, for example, Japanese Patent Laid-Open No. 61-14
It has been proposed in Publication No. 4576 and the like.

(Problem to be Solved by the Invention) However, in the conventional acceleration detection device, in order to detect acceleration at a relatively small level, stress concentration generated near the fixed end of the cantilever l due to acceleration causes strain gauge 16 It was designed to cause large distortions where it was fixed.

Therefore, when excessive acceleration is applied to the acceleration detection device, there is a problem in that excessive strain is generated at the location where the strain gauge 16 is fixed, and the cantilever beam 1 is damaged.

In addition, since the strain gauge 16 is fixed at a location where a large strain occurs, when acceleration is repeatedly applied to the acceleration detection device, the electrode formed on the strain gauge 16 and the conductive wire 17 fixed to the electrode will be damaged. There was also the problem that metal fatigue occurred and the detection characteristics of the acceleration detection device deteriorated.

Therefore, in the present invention, it is an object of the present invention to solve the above-mentioned problems of the prior art and to configure a highly sensitive and highly accurate acceleration detection device that has both durability against excessive acceleration and durability against repeatedly applied acceleration. Consider it a technical issue.

[Structure of the invention]

(Means for solving the problem) The technical means taken to achieve the above-mentioned technical problem includes: a base member; a displacement means that displaces relative to the base member in accordance with applied acceleration; A light emitting means that emits light in one direction and a light receiving means that detects the light emitted from the light emitting means are provided, one of the light emitting means and the light receiving means is used as the displacement means, and the other is used as the base member. This has been fixed to .

(Function) According to the above-mentioned technical means, the magnitude of acceleration is converted into a displacement of the displacement means, and this displacement is converted into an electric signal by the light projecting means and the light receiving means.

In the present invention, since the displacement of the displacement means is converted into an electric signal, the magnitude of strain occurring in the displacement means is unrelated to the detection sensitivity of the acceleration detection device. Therefore, even if excessive acceleration is applied to the acceleration detection device, the displacement means is unlikely to be damaged.

Further, since the strain caused by the displacement of the displacement means can be made relatively small, the characteristics of the acceleration detection device are unlikely to deteriorate even if acceleration is repeatedly applied to the acceleration detection device.

Furthermore, since the displacement of the displacement means is detected by light,
It is possible to accurately detect minute displacements of the displacement means. Therefore, highly sensitive and highly accurate acceleration detection can be performed.

In this way, according to the above-mentioned technical means, it is possible to construct a highly sensitive and highly accurate acceleration detection device that has both durability against excessive acceleration and durability against repeatedly applied acceleration.

In a preferred embodiment of the present invention, the displacement means includes: a pedestal fixed to the base member; a beam member having at least one end fixed to the pedestal; and a weight fixed to the beam member. Be prepared.

This allows the displacement means to be displaced relatively largely in response to a relatively small level of acceleration, thereby increasing the sensitivity of the acceleration detection device. Furthermore, the light emitting means and the light receiving means may be attached with poor accuracy. Therefore, an acceleration detection device suitable for mass production can be constructed.

Furthermore, in another preferred embodiment of the present invention, the displacement means includes a pedestal fixed to the base member and a pendulum means whose one end is pivotally supported by the pedestal.

This allows the displacement means to be displaced without generating stress or strain on the displacement means.

Therefore, an acceleration detection device with excellent durability can be constructed.

Furthermore, in another preferred embodiment of the present invention, the light projection means further includes a light generation means fixed on the base member and an optical fiber fixed to the light generation means, and , fixing the light receiving means on the base member;

In this way, the light projecting means and the light receiving means can be fixed to the same base member. Therefore, an acceleration detection device suitable for mass production can be constructed.

In another preferred embodiment of the present invention, the light receiving means is composed of one or more semiconductors.

If one semiconductor is used as the light receiving means, the acceleration applied to the acceleration detection device can be extracted as a level change of current or voltage.

Therefore, it is possible to configure an acceleration detection device that is easy to use in analog circuits.

Furthermore, if a plurality of semiconductors are used as the light receiving means, the acceleration applied to the acceleration detection device can be extracted as a digital value. Therefore, it is possible to construct an acceleration detection device that is easy to use for microcomputers and the like.

Furthermore, in another preferred embodiment of the present invention, the light receiving means comprises a cadmium sulfide cell.

In this way, the acceleration applied to the acceleration detection device can be extracted as a change in electrical resistance.

Furthermore, acceleration can also be extracted as a change in voltage using a bridge circuit or the like. Therefore, it is possible to configure an acceleration detection device that is easy to use in analog circuits.

(Example) Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 is a sectional view depicting a first embodiment of the invention.

A light emitting diode 5 and a detection element 6 are soldered to a printed circuit board 7 on which an electronic circuit is formed.

The light emitting diode 5 is covered with a cap 8.

Further, one end of the optical fiber 4 is fixed to the cap 8. One end of the optical fiber 4 is inserted into the cap 8 and faces the light emitting diode 5.

The detection element 6 is surrounded by a pedestal 2 having a U-shaped cross section. The pedestal 2 is a rectangular parallelepiped with one end open.
A cantilever beam 1 and a weight 3 are arranged inside it. Further, inside the pedestal 2, a cushioning material 11 having excellent light transmittance and hardly diffusing light is enclosed.

One end of a cylindrical cantilever beam 1 is firmly fixed to the center of the upper surface of the pedestal 2. Furthermore, a small hole (not shown) for inserting an optical fiber 4 is formed between the pedestal 2 and the cantilever 1, and the optical fiber 4 is drawn into the pedestal 2 through this small hole. There is.

A weight 3 is fixed to the other end of the cantilever beam 1. Furthermore, a small hole (not shown) is formed between the weight 3 and the cantilever beam 1, through which the optical fiber 4 is inserted, and one end of the optical fiber 4 is inserted into this small hole. One end of the optical fiber 4 faces the light receiving surface of the detection element 6.

Therefore, when the light emitting diode 5 is turned on, the light emitted by the light emitting diode passes through the inside of the optical fiber 4 and illuminates the light receiving surface of the detection element 6.

FIG. 2 shows how acceleration is applied to the acceleration detection device having such a configuration. FIG. 2 is a sectional view illustrating the operation of the first embodiment of the present invention.

When acceleration is applied to the acceleration detection device, a force proportional to the magnitude of the acceleration is generated in the weight 3, and stress is applied to the entire cantilever beam 1. This stress causes displacement in the cantilever beam 1. The point irradiated by one end of the optical fiber 4 moves on the light-receiving surface of the detection element 6 in accordance with the displacement of the cantilever beam 1.

On the light-receiving surface of the detection element 6, phototransistors, which are thin film semiconductors, form a matrix of 256×256 in plan. The detection element 6 is connected to the optical fiber 4.
The point illuminated by one end of the converter is converted into an 8-bit x 8-bit binary code and output.

That is, the magnitude and direction of acceleration are converted into a binary code and output from the detection element 6.

In the first embodiment, since the weight 3 is surrounded by the pedestal 2, the displacement of the cantilever beam 1 is limited by the inner surface of the pedestal 2. That is, once the outer surface of the weight 3 comes into contact with the inner surface of the pedestal 2, the cantilever beam 1 is no longer displaced. Therefore, even if excessive acceleration is applied, the cantilever beam 1 will not be displaced beyond its own elastic limit.

Further, in the first embodiment, as particularly shown in FIG. 2, the optical fiber 4 is deformed with a relatively large curvature along the side surface of the cantilever beam 1.

Therefore, the optical fiber 4 is unlikely to deteriorate.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view depicting a second embodiment of the invention. Note that members corresponding to those in the first embodiment are given the same reference numerals.

The second embodiment is an example in which a pendulum 9 is used instead of the cantilever beam 1 of the first embodiment. Although not shown, the light emitting diode 5 and the cap 8 are arranged in the same manner as in FIG.

A pendulum 9 is tiltably fixed to the base 2 by a slide 10. Further, a small hole (not shown) is formed in the pedestal 2, and an optical fiber 4 is drawn into the inside of the pedestal 2 through this small hole.

At one end of the pendulum 9, a weight 3 is integrally formed with the pendulum 9. A small hole (not shown) is formed inside the pendulum 9, and the optical fiber 4 is inserted into the small hole. One end of the optical fiber 4 faces the light receiving surface of the detection element 6 from the bottom surface of the weight 3.

Therefore, when the light emitting diode 5 is turned on, the light emitted by the light emitting diode 5 passes through the inside of the optical fiber 4 and illuminates the light receiving surface of the detection element 6.

When acceleration is applied to the acceleration detection device, a force proportional to the magnitude of the acceleration is generated in the weight 3. In proportion to this force,
Displacement occurs in the pendulum 9. The point irradiated by one end of the optical fiber 4 is determined by the detection element 6 according to the displacement of the pendulum 9.
move on the light-receiving surface of the

A PSD (position sensing detector) is arranged on the light receiving surface of the detection element 6. Then, the detection element 6 converts the point illuminated by one end of the optical fiber 4 into a voltage level and outputs the voltage level. That is, the magnitude of the acceleration is converted into a voltage level and output from the detection element 6.

By the way, the PSD is 32153 manufactured by Hamamatsu Photonics.
etc. are commercially available.

In the second embodiment, since the weight 3 is surrounded by the pedestal 2, the displacement of the pendulum 9 is limited by the inner surface of the pedestal 2. That is, once the outer surface of the weight 3 comes into contact with the inner surface of the pedestal 2, the pendulum 9 will not be displaced any further. Therefore, even if excessive acceleration is applied, the point irradiated by the optical fiber 4 will not be displaced beyond the light receiving surface of the detection element 6.

In addition, in the second embodiment, the pendulum 9 is
The tilting direction is limited to the left and right directions shown in the third figure. That is, the pendulum 9 does not tilt in the direction perpendicular to the plane of the paper. Therefore, the acceleration detection device of the second embodiment has detection sensitivity only in the -axis direction (left and right direction in the third figure).

Next, a third embodiment of the present invention will be described with reference to FIGS. 4a and 4b. FIG. 4a is a side view depicting a third embodiment of the present invention, and FIG. 4b is a sectional view depicting the third embodiment of the present invention. Note that members corresponding to those in the first embodiment are given the same reference numerals.

The third embodiment is an example in which a double-sided beam 12 is used instead of the cantilever beam 1 of the first embodiment.

Pedestals 2a and 2b are fixed on the printed circuit board 7 with a predetermined gap in between. Both ends of a thin plate-shaped double-supported beam 12 are fixed to the pedestals 2a and 2b, respectively. A weight 3 is fixed to the center of the double-supported beam 12. Moreover, on the printed circuit board 7, facing the weight 3,
The detection element 6 is fixed.

As in the first embodiment, a cap 8 is attached to the light emitting diode 5.
The optical fiber 4 is fixed using. The optical fiber 4 is arranged along the double-supported beam 12, and one end thereof is fixed to the weight 3. One end of the optical fiber 4 faces the light receiving surface of the detection element 6 from the bottom surface of the weight 3.

One end of the optical fiber 4 is specially processed.
Only the light-receiving surface of the detection element 6 is uniformly illuminated by the optical fiber 4.

Therefore, when the light emitting diode 5 is turned on, the light emitted by the light emitting diode passes through the inside of the optical fiber 4 and illuminates only the light receiving surface of the detection element 6.

When acceleration is applied to the acceleration detection device, a force proportional to the magnitude of the acceleration is generated in the weight 3, and stress is applied to the entire double-supported beam 12. Due to this stress, the entire double-supported beam 12 is twisted and displaced.

Then, the surface irradiated by one end of the optical fiber 4 moves in accordance with the displacement of the double-supported beam 12, and the amount of light entering the light receiving surface of the detection element 6 decreases.

A so-called CdS cell, in which a thin film of cadmium sulfide is uniformly applied, is formed on the light receiving surface of the detection element 6. Further, a resistor having a predetermined resistance value is disposed inside the detection element 6, and forms a bridge circuit together with the CdS cell. Then, the detection element 6 converts the amount of light entering the light receiving surface into a change in voltage level and outputs it. That is, the detection element 6 converts the magnitude of the acceleration into the magnitude of the voltage level and outputs it.

In the third embodiment, both ends of the double-supported beam 12 are connected to the pedestal 2a.
and 2b, the double-supported beam 12 is unlikely to be damaged even if excessive acceleration is applied.

Further, in the third embodiment, the double-supported beam 12 has a thin plate shape. Therefore, the direction of displacement of the double-supported beam 12 is the 4th b.
Limited to the left and right directions in the drawing. Therefore, the acceleration detecting device of the second embodiment has sharp detection sensitivity in the -axis direction (left and right direction in the figure 4b).

Next, a fourth embodiment of the present invention will be described with reference to FIGS. 5a and 5b. FIG. 5a is a left side view depicting a fourth embodiment of the present invention, and FIG. 5b is a sectional view depicting the fourth embodiment of the present invention.

The fourth embodiment is the acceleration detection device of the third embodiment,
Weight 3 is attached in a different way.

That is, in the fourth embodiment, the weight 3 is not directly fixed to the double-supported beam 12, but is fixed using the rod 13.

Therefore, in the fourth embodiment, it is possible to effectively utilize the torsional deformation of the double-supported beam 12 and detect a smaller level of acceleration.

In addition to this, the present invention can be implemented in various other ways. For example, Mr. B may support the weight 3 with springs 14 and 15 as in the fifth embodiment of the present invention shown in FIG.

As described above, the acceleration detection device of this embodiment converts the magnitude of acceleration into the amount of displacement of the cantilever beam 1, pendulum 9, etc., and converts this amount of displacement into an electrical signal using light. Therefore, the acceleration detection device of this embodiment has good durability against repeated acceleration. Further, hysteresis does not occur with respect to accelerations applied alternately between positive and negative.

In this embodiment, a detection element 6 that converts the amount of displacement into an electrical signal is used.
As (light receiving means), a phototransistor and a PSD,
Although an example using a cadmium sulfide cell has been introduced, similar light receiving means such as a solar cell or a photodiode can be used in the same manner as in this embodiment.

Further, although an example in which the light emitting diode 5 is used as a light projecting means for emitting light has been introduced, a discharge tube, an incandescent lamp, etc. can be considered as a similar light projecting means.

Furthermore, in this embodiment, the light emitting diode 5 is replaced by the detection element 6.
Although an example has been introduced in which the light emitting diode 5 and the detection element 6 are arranged on the same printed circuit board 7, it is not necessary to arrange the light emitting diode 5 and the detection element 6 on the same board 7. In particular, when using an ultra-small light emitting diode 5, the light emitting diode 5 may be directly fixed to the displacement means.

〔Effect of the invention〕

The present invention is an acceleration detection device that converts the magnitude of acceleration into a displacement amount of a displacement means, and detects this displacement amount using a light projecting means and a light receiving means.

Therefore, stress and strain applied to the displacement means can be dispersed. Therefore, the size and weight of the acceleration detection device can be reduced.

Furthermore, since the amount of displacement is detected using light, even a small amount of displacement can be detected with high accuracy.

Therefore, even relatively low-level accelerations can be detected with high accuracy.

Furthermore, since the amount of displacement is detected without contact, there are no members that become fatigued due to displacement of the displacement means. Therefore,
It is possible to construct an acceleration detection device that has both durability against excessive acceleration and durability against repeatedly applied acceleration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view depicting a first embodiment of the present invention, and FIG. 2 is a sectional view illustrating the operation of the first embodiment of the present invention. FIG. 3 is a cross-sectional view depicting a second embodiment of the invention. Figure 4a is a side view depicting a third embodiment of the invention;
Figure b is a sectional view depicting a third embodiment of the present invention. FIG. 5a is a left side view depicting a fourth embodiment of the present invention, and FIG. 5b is a sectional view depicting the fourth embodiment of the present invention. FIG. 6 is a sectional view depicting a fifth embodiment of the present invention. FIG. 7 is a sectional view depicting a conventional acceleration detection device. 1... Cantilever beam (displacement means) 2.2a, 2b... Pedestal 3... Weight 4... Optical fiber (light emitting means) 5... Light emitting diode (light emitting means) 6... Detection element (light receiving means) 7... Printed circuit board (base member) 8... Cap 9... Pendulum (displacement means) 10... Slip 11... Cushioning material 12... Double supported beam ( Displacement means) 13... Rod 14. 15... Spring (Displacement means) 16... Strain gauge 17... Conductor

Claims (6)

[Claims] (1) A base member, a displacement means that displaces relative to the base member in accordance with applied acceleration, a light projector that emits light in one direction, and a light receiver that detects the light emitted from the light projector. An acceleration detection device comprising: means, wherein one of the light projecting means and the light receiving means is fixed to the displacement means, and the other is fixed to the base member. (2) The displacement means further comprises: a pedestal fixed to the base member; a beam member having at least one end fixed to the pedestal; and a weight fixed to the beam member. The acceleration detection device according to item 1. (3) The acceleration detection device according to claim 1, wherein the displacement means further includes: a pedestal fixed to the base member; and a pendulum means whose one end is pivotally supported by the pedestal. (4) The light projecting means further includes a light generating means fixed on the base member, and an optical fiber fixed on the light generating means, and the light receiving means is fixed on the base member. An acceleration detection device according to claim 1. (5) The acceleration detection device according to claim 1, wherein the light receiving means is one or more semiconductors. (6) The acceleration detection device according to claim 1, wherein the light receiving means is a cadmium sulfide cell.