JP2002243441A - Tilt sensor - Google Patents

Abstract

(57) [Problem] To provide a tilt sensor capable of accurately detecting tilt in two directions of an X axis and a Y axis with a simple structure. A tilt sensor is provided at a position on each axis deviating from an intersection of two orthogonal axes (XY axes) in a plane parallel to the upper and lower surfaces of a sensor container 12 containing a liquid 11.
Two optical liquid level sensors 13 and 14 are arranged to detect the inclination of the sensor container 12 from the X-axis direction and the Y-axis direction. Two optical liquid level sensors 1
Each of the liquid crystals 3 and 14 has a refractive index different from that of the liquid 11 stored in the sensor container 12, and has a rectangular cross section whose size is arranged in the air from one end side arranged in the liquid. A solid rod-shaped light guide formed so as to become gradually smaller toward the other end is used as a sensing unit for detecting a liquid level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tilt sensor for detecting a tilt of a container by optically detecting a liquid level of a liquid contained in the container.

[0002]

2. Description of the Related Art An inclination sensor for detecting an inclination of a surveying instrument or the like is provided by placing a liquid in a sensor container fixed to a detection target such as a surveying instrument and optically measuring the inclination of the liquid surface with respect to the sensor container. It is configured to detect and output the detected value as a value indicating the inclination of the sensor container itself.

As this kind of tilt sensor, for example, the one shown in FIG. 8 is conventionally known. This is disclosed in
Although described in Japanese Patent No. 21638, an outline of this conventional tilt sensor will be described.

In FIG. 8, a control circuit 81 instructs a drive circuit 84 to shift the position of a light emitting diode 83 in a light emitting device 82.

The control circuit 81 controls the light emitted from the light emitting diode 83 at the standard position and the shifted light emitting diode 8.
The half value of the angle formed between the light emitted from 3 and
It is stored as the correction angle θ1.

The light emitted from the shifted light emitting diode 83 and reflected by the liquid surface L of the silicon oil 86 in the liquid tank 85 is converged on the light receiving surface of the PSD 88 by the fθ lens 87.

[0007] The spot position of the converged light is calculated by a signal processing circuit 89.

The signal processing circuit 89 calculates the inclination of the light with respect to the optical axis of the fθ lens 87 based on the calculated spot position. Then, the half value is input to the control circuit 81 as the tilt detection angle θ2.

The control circuit 81 corrects the inclination detection angle θ2 by the correction angle θ1 to calculate a relative inclination angle of the liquid level L.

[0010]

However, the above-mentioned conventional tilt sensor has a complicated structure, and requires considerable accuracy in designing. Further, the inclination direction to be detected is an inclination in one direction, such as an inclination from the X-axis direction or an inclination from the Y-axis direction, and cannot be detected in two directions.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to provide a tilt sensor capable of accurately detecting tilt in two directions of X-axis and Y-axis with a simple structure. I do.

[0012]

In order to achieve the above object, the tilt sensor according to the present invention has a refractive index different from that of the liquid stored in the sensor container, and the size of the rectangular cross section is A sensing part for detecting a liquid level by a solid rod-shaped light guide formed so as to gradually decrease from one end side arranged in the liquid toward the other end side arranged in the air; On the other end side, an optical liquid level sensor in which a projection unit for projecting light toward the end surface on the one end side and a light receiving unit for detecting light propagating from the one end side in the sensing unit are arranged, The sensor container is arranged at a position on each axis deviating from the intersection of two orthogonal axes in a plane parallel to the upper and lower surfaces of the sensor container.

According to this configuration, the optical liquid level sensor can detect the liquid level on the X-axis and the Y-axis based on a change in the amount of propagating light in the light guide constituting the sensing unit. it can. Since the change in the liquid level and the change in the amount of light associated therewith have a substantially linear relationship, it can be detected with high accuracy.

Therefore, it is possible to provide a tilt sensor which can accurately detect tilt in two directions of the X axis and the Y axis with a simple structure.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an external view of a tilt sensor according to an embodiment of the present invention. FIG. 1A is a perspective view,
FIG. 1B is a top view.

As shown in FIG. 1, the tilt sensors are located on respective axes that deviate from the intersection of two orthogonal axes (XY axes) in a plane parallel to the upper and lower surfaces of a sensor container 12 containing a liquid 11. And two optical liquid level sensors 13 and 14
Are arranged to detect the inclination of the sensor container 12 from the X-axis direction and the Y-axis direction.

Two optical liquid level sensors 13 and 14
Have a refractive index different from that of the liquid 11 stored in the sensor container 12, and have a rectangular cross-section having a size from one end arranged in the liquid to the other end arranged in the air. A solid rod-shaped light guide formed so as to become gradually smaller toward is used as a sensing unit for detecting a liquid level, and is configured as shown in FIG. 2, for example.

FIG. 2 is a configuration diagram of an optical liquid level sensor used in one embodiment of the present invention. Note that FIG.
(A) is an external view configuration diagram. FIG. 2B is a sectional view taken along the line AA in FIG.

As shown in FIG. 2A, the optical liquid level sensor 20 includes a sensing unit 21 having a predetermined length,
One end (hereinafter referred to as “base end”) 2 of the sensing unit 21
The sensing unit 21 includes a projecting unit 23 and a light receiving unit 24 that are arranged opposite to the end surface of the sensing unit 2a.

The sensing section 21 is made of a solid rod-shaped light guide having a refractive index different from that of the liquid to be measured, such as acrylic resin or glass, and has a rectangular cross section as shown in FIG. Has become. The size of the rectangular cross section is formed to be slightly smaller from the distal end portion 22b toward the proximal end portion 22a. That is, the vertical section along the length direction of the sensing unit 21 has a trapezoidal shape with long oblique sides.

The specular reflecting portion 25 is formed by inclining the end surface of the tip portion 22b with respect to the longitudinal direction (the optical axis direction) of the sensing portion 21, and the inclined end surface is subjected to mirror finishing.

As a result, from the base end 22a to the front end 22
The light propagating toward b is totally reflected toward the boundary surface by the specular reflection unit 25, and propagates toward the base end 22a while repeating reflection between the boundary surfaces.

The projection unit 23 may be configured to directly project the light emitted from the light emitting element onto the end face of the base end 22a, or may be guided by an optical fiber and project the light onto the end face of the base end 22a.

The light receiving portion 24 may be configured to receive the light emitted from the end face of the base end portion 22a directly by the light receiving element.
The light may be received by an optical fiber and guided to a light receiving element.

Next, the operation of the tilt sensor using the optical liquid level sensor configured as described above will be described with reference to FIG. FIG. 3 shows an arrangement 1 on the X-axis or the Y-axis.
FIG. 5 is a diagram illustrating a use state of two optical liquid level sensors.

As shown in FIG. 3, the optical liquid level sensor 20 includes a sensing part 21 having a base end 22a formed of air 31.
It is arranged so that the tip 2 b is located in the liquid 11.

The liquid level S crosses an appropriate position of the sensing section 21. Although the refractive index of the sensing unit 21 is different from that of the liquid 11, the refractive indexes of both are air 3
It is larger than the refractive index of 1.

Light is projected substantially perpendicularly from the projection unit 23 toward the end face of the base end 22a. The sensing part 21 forms a divergent optical waveguide from the base end 22a toward the front end 22b.

The light projected from the projection section 23 has a certain directivity width. For this reason, the sensing unit 21
The light incident on the sensing portion 21 is divided into light that is incident straight and travels straight, and light that is incident at a certain angle and that is repeatedly reflected between the boundary surfaces of the sensing portion 21 and heads toward the tip portion 22b. The sensing unit 21 is designed in an optimal shape for most of these lights. In addition, light incident over a certain width exceeds the critical angle, and is refracted outside regardless of air or liquid.

As described above, the incident light projected on the base end portion 22a is divided into light that travels substantially straight in the sensing portion 21 and light that travels by repeating reflection at the boundary surface of the sensing portion 21.
The light reaches the mirror reflection unit 25.

Since the specular reflection portion 25 is inclined at a predetermined angle with respect to the optical axis, the incident light is reflected toward the boundary surface of the sensing portion 21. Since the reflected light is incident on the boundary surface of the sensing unit 21 at an angle, reflection is repeated between the boundary surfaces of the sensing unit 21, and the reflected light is reflected by the base end 2.
Propagation toward 2a.

At this time, the sensing section 21 is
Since an optical waveguide that gradually narrows from 2b toward the base end 22a is formed, the angle of incidence on the boundary surface of the sensing unit 21 increases toward the base end 22a.

In the section from the tip 22b to the liquid level S, the ratio of the reflected light reflected at the boundary surface and returning to the inside and the refracted light refracted at the boundary surface and going outside is determined by the sensing unit 21 Relationship between the refractive index of the liquid 11 and the sensing unit 21
Although it depends on the angle of incidence on the boundary surface, part of the light is emitted as refracted light into the liquid 11, and the amount of reflected light (propagating light) is reduced accordingly.

On the other hand, in the section from the liquid level S to the base end 22a, the outside is air 31 and the sensing section 21
Since the angle of incidence on the boundary surface of falls within the range of the critical angle, almost all the incident light is reflected.

That is, the light level of the propagating light reaching the light receiving portion 24 reflects the section length from the tip 22b to the liquid level S, so that the liquid level S can be detected. In addition, this value has a linear correspondence relationship that the value decreases as the section length from the tip end portion 22b to the liquid level S increases.

Therefore, the optical liquid level sensor configured as described above has the following advantages. (1) Since the sensing unit 21 is formed of a rod-shaped light guide, the size can be reduced. (2) Since glass, acrylic resin, or the like is used for the light guide, chemical resistance is improved. (3) Since there is no mechanical structure and no heat generation, the durability is improved. (4) Since a linear output is obtained for the liquid level, accurate measurement is possible.

The optical liquid level sensor disposed on the X axis and the optical liquid level sensor disposed on the Y axis are connected to independent detection circuits. This detection circuit can be configured, for example, as shown in FIG.

FIG. 4 is a configuration diagram of the X (Y) direction detection circuit.

In FIG. 4, a constant current pulse generating circuit 41
Generates a constant current pulse for causing the light emitting element 42 to emit light. The light emitted from the light emitting element 42 is guided to the projection unit 23.

Propagation light having a changed light amount and emitted from the light receiving section 24 is detected by the light receiving element 43.

The output (pulse signal) of the light receiving element 43 is X
In the (Y) direction offset circuit 44, a shift operation is performed to set an optimum value without a tilt, and the voltage is amplified to an appropriate level by a voltage amplifier circuit 45.

The amplified pulse signal is converted into a DC voltage by a pulse / voltage conversion circuit 46 and input to an X (Y) direction voltage / inclination amount conversion circuit 47.

X / Y direction voltage / inclination amount conversion circuit 47
Has a conversion table and converts the input DC voltage to X (Y)
Is converted to a tilt amount (digital value or analog value) in the direction. This detected value (inclination amount) is provided for display or the like.

FIG. 5 shows an example of detection characteristics of the tilt sensor according to the present embodiment. In FIG. 5, the horizontal axis is X
The amount of inclination in the (Y) direction [°], and the vertical axis is the relative output of the liquid level sensor.

As shown in FIG. 5, when the amount of inclination increases from 0 (zero) in the negative direction, the light-receiving unit 24 receives a large amount of light emitted from the projection unit 23 with an increase in the section of the sensing unit 21 in the air. Since the part is incident, the output value increases linearly.

On the other hand, when the tilt amount increases from 0 (zero) in the plus direction, the amount of light incident on the light receiving unit 24 decreases linearly with the increase of the submerged section in the sensing unit 21, so that the output It is shown that the values also decrease linearly and correspondingly.

Further, since it is shown that a sufficient change can be obtained even for a small inclination, it can be understood that detection can be performed with high accuracy.

Next, a specific mounting structure of the liquid level sensor will be described with reference to FIGS. FIG. 6 is a diagram (Example 1) showing the structure of the optical liquid level sensor and the structure for attaching the optical liquid level sensor to the sensor container. FIG. 7 is a diagram (Example 2) showing a structure of the optical liquid level sensor and a structure for attaching the optical liquid level sensor to the sensor container.

In FIG. 6, the upper surface 61 of the sensor container 11
The space between the sensor case 62 of the liquid level sensor and the sensor case 62 is hermetically sealed by a packing 63 and fixed by a sensor fixing bracket 64.

The sealing post plug 65 has a shape in which the vertex of a cone is cut in accordance with the taper of the sensor case 62, and a through hole for the light guide 66 is provided at the center. The sealing column plug 65 is pushed into the tapered portion of the sensor case 62 by the sealing column plug fixing screw 67 to separate the inside and outside of the container.

The light guide 66 is fixed by a light guide fixing frame 68 via a light guide support spacer 69 to fix the strength. A light emitting / receiving element 70 is provided at the upper end of the light guide 66. Above it, a substrate 71 on which a detection circuit is mounted is provided.

FIG. 7 shows a case in which the sensor case 75 has a metal screw structure and is screwed and fixed to the upper surface 76 of the sensor container 11, and the other structure is the same as that shown in FIG.

With the screw structure shown in FIG. 7, versatility can be provided.

[0055]

As described above, according to the present invention,
With the simple structure, it is possible to provide an inclination sensor that can accurately detect inclination in two directions of the X axis and the Y axis.

[Brief description of the drawings]

FIG. 1 is an external view of a tilt sensor according to an embodiment of the present invention. (A) is a perspective view, (b) is a top view.

FIG. 2 is a configuration diagram of an optical liquid level sensor used in one embodiment of the present invention. (A) is an external view configuration diagram. FIG. 3B is a sectional view taken along line AA in FIG. 2.

FIG. 3 is a diagram illustrating a use state of one optical liquid level sensor disposed on an X axis or a Y axis.

FIG. 4 is a configuration diagram of an X (Y) direction detection circuit.

FIG. 5 is a diagram illustrating an example of detection characteristics of the tilt sensor according to the present embodiment.

FIG. 6 is a diagram (Example 1) showing a structure of an optical liquid level sensor and a structure for attaching the optical liquid level sensor to a sensor container.

FIG. 7 is a diagram (example 2) showing a structure of an optical liquid level sensor and a structure for attaching the optical liquid level sensor to a sensor container.

FIG. 8 is a diagram illustrating a configuration example of a conventional tilt sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Liquid 12 Sensor container 13, 14 Optical liquid level sensor 20 Optical liquid level sensor 21 Sensing part 23 Projection part 24 Light reception part 25 Mirror reflection part

Claims (1)

[Claims] 1. A sensor having a refractive index different from that of a liquid contained in a sensor container, and having a rectangular cross section having a size from one end arranged in the liquid to the other end arranged in the air. A solid bar-shaped light guide formed so as to become gradually smaller constitutes a sensing unit for detecting a liquid level, and a projection unit for projecting light toward the one end surface on the other end side. And an optical liquid level sensor in which a light-receiving unit for detecting light propagating from the one end side in the sensing unit is disposed, and the optical liquid level sensor deviates from the intersection of two orthogonal axes in a plane parallel to the upper and lower surfaces of the sensor container. A tilt sensor disposed at a position on each axis.