JP3447452B2 - Liquid level detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detector for detecting the presence of a liquid level by being immersed in a liquid.

FIG. 10 is a sectional view of a conventional liquid level detector disclosed in, for example, Japanese Patent Application Laid-Open No. 5-99729. In FIG. 10, 11 is an optical fiber for projecting light, 12 is an optical fiber for receiving light, and 13 is both. A holding member fixed to the tips of the optical fibers 11 and 12 with an adhesive 14 in order to keep the tips at a constant interval and posture, and 15 denotes both optical fibers 1
1 and 12 and a space 15a for holding the holding member,
A protective member integrally formed with a conical prism 15b at its tip portion, and 16 is a retaining member for preventing the optical fibers from being detached by crimping and fixing to the inner peripheral surface of the protective member 15.

FIG. 11 is an enlarged view showing an example in which the tip portion 13a-1 of the optical fiber insertion hole 13a is bent at an acute angle, and the tip portions of the light projecting optical fiber 11 and the light receiving optical fiber 12 inserted into the inserting hole are , Is bent at an acute angle α. Therefore, when the conical prism 15b is in the liquid, the light from the light projecting optical fiber 11 to the conical prism has an emission angle β, and the optical fibers 11 and 12 project on the horizontal plane in contact with the apex of the conical prism 15b having the apex angle θ. The target spot S ₁₁ and the light receiving target spot S ₁₂ do not overlap with each other and are separated from each other, so that no inconvenience caused by the overlap of the target spots S ₁₁ and S ₁₂ occurs.

[0004]

Since the conventional liquid level detector is constructed as described above, as shown in FIG.
In order to bend the tip ends of the light projecting optical fiber 11 and the light receiving optical fiber 12 into an arc shape at an inclination angle α, the optical fiber insertion hole 13a to be machined in the holding member 13 also needs to be machined into an arc shape. Machining arc holes is very troublesome.

Further, as shown in FIG. 11, if the tip end portion 13a-1 of the optical fiber insertion hole 13a is bent at an acute angle to form a straight line, the hole for the holding member 13 is straight, so that it is easy. However, the optical fiber insertion hole 1
There is a problem that the tip of the optical fiber to be inserted hits the intersection of 3a and the tip 13a-1 and the insertion is difficult, and the tip of the optical fiber is damaged.

The present invention has been made to solve the above problems, and an object thereof is to obtain a liquid level detector which is easy to make a hole in a holding member of an optical fiber and has high detection sensitivity.

[0007]

According to a second aspect of the present invention, there is provided a liquid level detector in which an optical element having a condensing function is provided at the tip of the optical fiber for light projection and the optical fiber for light reception provided for each optical fiber. It is arranged non-coaxially .

The liquid level detector according to the second aspect of the invention is
An optical element having an optical axis bending function for bending the optical axes in mutually opposite directions is provided at the tips of the juxtaposed light emitting optical fiber and light receiving optical fiber.

A liquid level detector according to a third aspect of the invention is
As an optical element, a cylindrical lens is arranged with the optical axes of the optical fiber for light projection and the optical fiber for light reception provided side by side shifted in parallel to the outside.

According to a fourth aspect of the present invention, there is provided a liquid level detector,
As an optical element, a cylindrical lens is arranged with the optical axes intersecting the optical axes of the light projecting optical fiber and the light receiving optical fiber, which are provided side by side.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. FIG. 1 is a sectional view showing a liquid level detector according to the first embodiment, and FIG. 2 is an enlarged sectional view of a tip portion thereof. In the figure, 1 is a light projecting optical fiber, 2 is a light receiving optical fiber, and 3 is a holding member that holds both optical fibers 1 and 2 side by side, and is made of, for example, a synthetic resin such as polyacetal. Numerals 4 and 5 are columnar lenses as optical elements arranged at the tips of both optical fibers 1 and 2, for example, SELFOC microlenses (trademark of Nippon Sheet Glass Co., Ltd.,
Hereinafter, abbreviated as SML) is used. 6 has a space 6a for accommodating both the optical fibers 1, 2 and the holding member 3,
A conical prism 6b as a prism portion is integrally formed at the tip portion of the protective member, which is made of synthetic resin such as Teflon.

The SMLs 4 and 5 are cylindrical optical glass bodies in which the refractive index is distributed in a parabolic shape from the central axis toward the outer peripheral surface, and have properties equivalent to a curved lens even when both end surfaces are flat. have. These SMLs 4 and 5 are obtained by immersing a glass rod in a molten salt for a long time and preliminarily doping the glass with a large electron polarizability, and exchanging monovalent ions that easily move in the glass at high temperature with alkali ions in the molten salt. Then, by utilizing the parabolic approximation of the resulting ion diffusion distribution, the inflection rate distribution necessary for the lens-like medium is formed.

The lenticular medium of SML4, 5 is
It has an optical coupling function, a parallel beam forming function, and a light collecting function. In particular, by selecting the length L, a lens having an arbitrary focal length can be manufactured. Therefore, if the length L is selected so that the focal point is formed on the surface of the conical prism 6b as shown in FIG. 1, the light beam can be condensed. As a result,
The light projection target spots S ₁ and the light reception target spots S ₂ of both the optical fibers 1 and 2 on the horizontal plane that is in contact with the apex of the surface of the conical prism 6b do not overlap each other and are separated from each other, and the target spots S ₁ and S ₂ overlap. There is no inconvenience caused.

Next, the operation will be described. As shown in FIG. 2, when the liquid surface level 7 is at a lower level that does not contact the conical prism 6b, the emitted light A from the light projecting optical fiber 1 is condensed and reflected at one point of the conical prism 6b. The light B enters the light receiving optical fiber 2 and is detected.

On the other hand, when the liquid level 7 is at a higher level in contact with the conical prism 6b, the light projecting optical fiber 1
Part of the emitted light A from A ₁ and A ₂ is the conical prism 6b.
And the amount of incident light on the light receiving optical fiber 2 decreases. Therefore, by detecting this decrease in the amount of light, it is possible to detect that the liquid surface level 7 is at a predetermined position.

As described above, according to this embodiment,
Since the emission light A from the light projecting optical fiber 1 is configured to be condensed on the conical prism, the projection target spot S
It is possible to prevent overlapping of ₁ and the light receiving target spot S ₂ , prevent malfunction, and reduce light loss to improve the S / N ratio. The same effect can be obtained by using a condenser lens instead of the cylindrical lens.

Embodiment 2. FIG. 3 is a sectional view showing the liquid level detector according to the first embodiment, and FIG. 4 is an enlarged sectional view of the tip portion thereof. In the figure, 4a and 5a are SMLs whose optical axes are arranged parallel to the optical axes of the optical fibers 1 and 2 and displaced in the opposite directions by a dimension c. In this way, when the optical axes of the optical fibers 1 and 2 and the SMLs 4a and 5a are deviated from each other in parallel, the light projecting optical fibers 1 to SML4 are moved.
The light incident on a is reflected by the inner surface of the SML 4a, bent, and emitted at an emission angle β. Further, the light enters the SML 5a at the incident angle γ which is the same as the outgoing angle β. As a result, similarly to the first embodiment, the projection target spots S ₁ and the light reception target spots S ₂ of the optical fibers 1 and 2 on the horizontal plane in contact with the apex of the surface of the conical prism 6b do not overlap each other and are separated from each other, No inconvenience caused by the overlapping of the target spots S ₁ and S ₂ occurs.

FIG. 5 shows an example of the dimensions of each component assembled to the holding member 3 in the second embodiment. The holding member 3 has a length l = 15 mm and a diameter D = 5 mm. Spacing g1 with the optical fiber 2
= 2.2 mm, diameter d1 of the optical fiber insertion hole = 1.1
5 mm, SML 4a, 5a insertion interval g2 = 2.8m
m, the insertion length l of the SMLs 4a and 5a is 1 = 5 mm, and the wavelength of light used is 0.66 to 0.68 μm.

As described above, according to this embodiment,
Since the optical axes of the emitted light A from the light projecting optical fiber 1 and the incident light B to the light receiving optical fiber are bent in mutually opposite directions, the projecting target spot S ₁ and the receiving target spot S _{2 do not} overlap. Therefore, it is possible to reliably prevent malfunction.

Embodiment 3. FIG. 6 is a sectional view showing a liquid level detector according to the third embodiment. In the figure, SMLs 4b-1 and 5 with different diameters are provided at the tips of the optical fibers 1 and 2.
b-1 and 4b-2, 5b-2 are arranged so that their optical axes are sized c1,
It is provided by shifting by c2, and is an optical fiber 1 for projecting light.
Emitted light A from the light source and incident light B to the light receiving optical fiber
Each of the optical axes will be bent twice.

As described above, according to this embodiment,
Since the optical axes of the emitted light A from the light projecting optical fiber 1 and the incident light B to the light receiving optical fiber are bent by two SMLs, there is an effect that the optical axes can be smoothly bent at a desired angle. can get.

Fourth Embodiment FIG. 7 is a sectional view showing a liquid level detector according to the fourth embodiment. In the figure, the SMLs 4c and 5c having the same diameter at the tips of the optical fibers 1 and 2 are shown.
Is arranged so that the optical axis intersects the optical axis of the optical fiber.

As described above, according to this embodiment,
Since the SMLs 4c and 5c are arranged so as to intersect with the optical axes of the light projecting optical fiber 1 and the light receiving optical fiber, the optical axes of the outgoing light A and the incident light B are set to desired angles by selecting the crossing angles. The effect that it can be bent is obtained.

Embodiment 5. 8 is a sectional view showing a liquid level detector according to the fifth embodiment, and FIG. 9 is a perspective view of an SML used in the fifth embodiment. In the figure, the SMLs 4d and 5d having the same diameter are provided at the distal ends of the optical fibers 1 and 2 so as to be spread out so that the optical axis intersects with the optical axis of the optical fibers. As shown in FIG. SML4d (5d)
Both ends 4d-1 (5d-1) of the optical fiber 1, 2
And, it is formed in a slope so that the surface of the holding member 3 is well matched.

As described above, according to this embodiment,
Since the SML whose both ends are formed to be slanted and the facing portions of the light projecting optical fiber 1 and the light receiving optical fiber 2 and the SMLs 4d and 5d are made extremely close to each other, the optical loss between the optical fiber and the SML is reduced. The effect that can be obtained is obtained.

[0026]

According to the first aspect of the invention, the optical element having a light-collecting function is provided at the tip of each of the light-transmitting optical fiber and the light-receiving optical fiber provided side by side.
Since it is arranged non-coaxially, the light projecting spot formed by the light projecting optical fiber and the light receiving target spot of the light receiving optical fiber do not overlap with each other, and there is an effect that a malfunction does not occur .

According to the second aspect of the present invention, since the optical elements having the function of bending the optical axes in the opposite directions are arranged at the tips of the juxtaposed light emitting optical fiber and light receiving optical fiber, the light emitting optical fiber and the light receiving optical fiber are arranged. The light projecting spot formed by the optical fiber and the light receiving target spot of the light receiving optical fiber do not overlap with each other, and no malfunction occurs. Further, since the hole for assembling the optical element and the optical fiber is a straight line, there is an effect that a hole can be easily formed in the holding member.

According to the third aspect of the present invention, as the optical element, a cylindrical lens is arranged such that the optical axes of the juxtaposed optical fiber for projection and optical fiber for light reception are shifted in parallel to the outside. Therefore, the cylindrical lenses can bend the optical axes of the emitted light A and the incident light B in directions opposite to each other and reliably prevent malfunction. Moreover, since the hole for assembling the optical fiber to the holding member is a straight hole, there is an effect that it can be easily and easily performed.

According to the invention described in claim 4, as the optical element, a cylindrical lens is arranged so that the optical axes intersect with the optical axes of the light-transmitting optical fiber and the light-receiving optical fiber which are provided side by side. By selecting the crossing angle, the optical axes of the outgoing light A and the incoming light B can be bent at a desired angle. Moreover, since the hole for assembling the optical fiber to the holding member is a straight hole, there is an effect that it can be easily and easily performed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a liquid level detector according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a tip portion of the liquid surface detector according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a liquid level detector according to a second embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view showing a tip portion of a liquid level detector according to Embodiment 2 of the present invention.

FIG. 5 is a dimensional explanatory view of each part of the liquid level detector according to the second embodiment of the present invention.

FIG. 6 is a sectional view showing a liquid level detector according to a third embodiment of the present invention.

FIG. 7 is a sectional view showing a liquid level detector according to Embodiment 4 of the present invention.

FIG. 8 is a sectional view showing a liquid level detector according to a fifth embodiment of the present invention.

FIG. 9 is a perspective view showing an SML used in a fifth embodiment of the present invention.

FIG. 10 is a sectional view showing a conventional liquid level detector.

FIG. 11 is an enlarged cross-sectional view of a tip portion of a protection member of a conventional liquid level detector.

[Explanation of symbols]

1 Optical fiber for projecting light 2 Optical fiber for receiving light 4, 4a, 4b-1, 4b-2, 4c, 4d, 5, 5
a, 5b-1, 5b-2, 5c, 5d SML (optical element, cylindrical lens) 6b Conical prism (prism part)

Claims (4)

(57) [Claims] 1. A prism having a light projecting optical fiber and a light receiving optical fiber provided side by side, and having an inner reflecting surface for allowing light emitted from the light projecting optical fiber to be incident on the light receiving optical fiber in front of the front ends of the both optical fibers. In the liquid level detector provided with a section, an optical element having a light collecting function is provided at the tip of each of the optical fibers.
A liquid level detector characterized by being arranged non-coaxially with respect to the surface. 2. A prism having a light-projecting optical fiber and a light-receiving optical fiber provided side by side, and having an inner reflecting surface for allowing light emitted from the light-projecting optical fiber to enter the light-receiving optical fiber, in front of the front ends of the both optical fibers. In the liquid level detector having a section, an optical element having an optical axis bending function for bending the optical axes in opposite directions is arranged at the tip ends of the both optical fibers. 3. The optical element is a cylindrical lens arranged such that the optical axes of the light-transmitting optical fiber and the light-receiving optical fiber, which are provided side by side, are arranged so as to be shifted in parallel to the outside. Liquid level detector. 4. The liquid surface according to claim 2, wherein the optical element is a cylindrical lens disposed such that the optical axes of the optical fiber for projecting light and the optical fiber for receiving light which are provided side by side intersect each other. Detector.