Photoelectric liquid level sensor

Abstract

To provide a photoelectric liquid level sensor which is easily assembled and can reliably detect liquid levels without variation in measuring accuracy of a reflection type photosensor regardless of variation in a substrate body of a wiring board, or a component or assembly mounted on the substrate body.SOLUTION: A spring material 4 is attached to a substrate body 31. A substrate body 2 inserted into a polypropylene resin casing 2 is held in a close-fitting state against an internal surface of a substrate housing part 21 by energizing force of the spring material 4 on a position where a reflection type photosensor 32 mounted on the substrate body 31 is facing a prism lens part 22.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a photoelectric liquid level sensor.

Background Art

[0002] For example, when refueling a kerosene tank or the like into an airtight oil tank (cartridge tank) or an oil tank such as a household oil stove or an oil fan heater, an electric pump is used. And for this type of electric pump, a photoelectric liquid level sensor is attached to the tip of the fuel supply pipe so that refueling can be stopped at a level where kerosene does not spill from the tank. When refueling is completed up to a predetermined level, the motor automatically stops in some cases.

[0003] As the above photoelectric liquid level sensor, it includes a transparent resin housing with a prism-shaped tip and a wiring board on which a reflective photosensor composed of a light-emitting element and a light-receiving element is mounted. The wiring board is housed in a wiring board housing portion in the housing so as to face a prism lens portion provided so that the reflective photosensor (photoelectric sensor) portion protrudes outward from the wall surface of the housing. When the prism lens portion is in the liquid, the light beam emitted from the light-emitting element is hardly reflected by the prism reflection surface of the prism lens portion and is scattered in the liquid, so it hardly returns to the light-receiving element side. When the prism lens portion is in the air, it is reflected by the prism reflection surface of the prism lens portion and returns to the light-receiving element. It has already been proposed that the liquid level in the tank can be determined whether it has reached a predetermined level based on the amount of light returning to the light-receiving element (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in order to improve the detection performance of the above photoelectric liquid level sensor, it is necessary to use it effectively without degrading the optical output characteristics. However, when there is an air layer between the reflective photosensor (reflective photointerrupter) and the inner wall surface of the wiring board housing portion, due to variations in the substrate body of the wiring board and the components mounted on the substrate body, as well as assembly variations, the effective light amount changes. As a result, there is a risk that the liquid level may always be judged as being in the liquid, or products may be produced with a threshold value on the verge, resulting in a large variation range. In addition, some light may always be reflected by the prism lens portion even in the liquid, and there is also a risk that it may be judged to be in the air.

[0006] On the other hand, in order to solve the above problems, as shown in FIG. 9, a transparent resin adhesive (potting liquid) is filled between the wiring board 300 and the inner wall surface of the substrate housing portion 210 of the housing 200, and a transparent resin cured body layer 400 is formed between the reflective photosensor 320 and the inner wall surface of the substrate housing portion 210 to eliminate the air layer. There is also a photoelectric liquid level sensor 100 that employs a so-called potting method. That is, in the case of the photoelectric liquid level sensor 100 using the potting method, even if there are variations in the substrate body 310 of the wiring board 300 and components such as the reflective photosensor 320 mounted on the substrate body 310, or assembly variations, a transparent resin cured body layer 400 is formed between the reflective photosensor 220 and the inner wall surface of the substrate housing portion 210. Therefore, the light reaches the prism reflecting surface of the prism lens portion 220 in almost the same state emitted from the light emitting element, and the change in the light amount is small.

[0007] However, in the case of the above potting method, there is a problem that the curing of the transparent resin adhesive takes time, and there is a risk that bubbles may be mixed in the cured body or adhesion peeling may occur during the reaction curing of the transparent resin adhesive, resulting in sensor detection failures. That is, when a cured body layer mixed with bubbles is formed or adhesion peeling occurs, the degree of light scattering and refraction varies depending on the size and position of the bubbles and the adhesion peeling portion, etc., and it is always judged as being in the air, or a product right at the threshold is produced, resulting in a large variation range.

[0008] In particular, when a housing is made of a polypropylene resin with poor transparency or the like, this tendency becomes stronger. Therefore, the resin used for the housing is also limited.

[0009] In view of the above circumstances, an object of the present invention is to provide a photoelectric liquid level sensor that can surely detect a liquid level without variation in the measurement accuracy of a reflection type photosensor even when there are variations in the substrate body of a wiring board or the components mounted on the substrate body and variations in assembly, and that is easy to assemble.

Means for Solving the Problems

[0010] The photoelectric liquid level sensor of the present invention includes a wiring board on which a reflection type photosensor provided such that a light emitting element and a light receiving element face one side surface thereof is mounted on a substrate body, and a housing having a substrate accommodating portion for accommodating this wiring board. In a state where the housing accommodates the substrate in the substrate accommodating portion, at least a portion of the housing facing the light emitting element and the light receiving element is formed of a light transmissive material, and a prism lens portion having a prism reflecting surface for reflecting light emitted from the light emitting element and causing it to be received by the light receiving element. The photoelectric liquid level sensor is characterized in that biasing means for biasing the substrate body is provided so that the one side surface of the reflection type photosensor is in close contact with the inner wall surface of the substrate accommodating portion.

[0011] In the present invention, examples of the biasing means include a metal spring, a resin spring, a rubber elastic body, etc., and these may be used alone or in combination. Further, the biasing means may be attached to the substrate body, may be attached to the inner wall surface of the substrate housing portion, or may be attached to both sides of the inner wall surface of the substrate body and the substrate housing portion.

[0012] In the photoelectric liquid level sensor of the present invention, the prism reflecting surface may be provided along the axial direction of the housing, and the wiring board may be housed in the substrate housing portion parallel to its axis.

[0013] In the photoelectric liquid level sensor of the present invention, a positioning recess or a positioning projection is provided on the wiring board, and when the wiring board is housed in the substrate housing portion, the positioning recess or the positioning projection of the wiring board fits in, and a positioning projection or a positioning recess for positioning the wiring board is provided on the inner wall surface of the substrate housing portion.

[0014] The material of the casing of the photoelectric liquid level sensor of the present invention is not particularly limited as long as the portions facing the transmitting element and the receiving element of the reflection type photosensor are formed of a light transmissive material. For example, acrylic resin, polyester resin, polycarbonate resin, polypropylene resin, polyethylene resin can be mentioned. When corrosion resistance against the liquid agent is desired, or when it is used for liquid level management of a liquid agent that cannot tolerate even a little contamination or pollution, polypropylene resin and polyethylene resin are preferable.

Advantages of the Invention

[0015] As described above, the photoelectric liquid level sensor of the present invention includes a wiring board on which a reflection type photosensor provided such that a light emitting element and a light receiving element face one side surface thereof is mounted on a substrate body, and a housing having a substrate accommodating portion for accommodating this wiring board. In a state where the housing accommodates the substrate in the substrate accommodating portion, at least a portion of the housing facing the light emitting element and the light receiving element is formed of a light transmissive material, and the photoelectric liquid level sensor includes a prism lens portion having a prism reflecting surface for reflecting light emitted from the light emitting element and causing it to be received by the light receiving element. The substrate body is provided with biasing means for biasing the substrate body so that one side surface of the reflection type photosensor is in close contact with the inner wall surface of the substrate accommodating portion. Therefore, even if there are variations in the bending of the substrate body, variations in the height of the reflection type photosensor, variations in the mounting of the reflection type photosensor, and variations in the molding of the substrate body due to the biasing means, the one side surface of the reflection type photosensor facing the light emitting element and the light receiving element can be held in a state of being in close contact with the inner wall surface of the substrate accommodating portion.

[0016] That is, even if there are variations in the substrate body of the wiring board, variations in the components mounted on the substrate body, and variations in assembly, almost no air layer is formed between the reflection type photosensor and the inner wall surface of the substrate accommodating portion. Therefore, there are no variations in the measurement accuracy of the reflection type photosensor, and the liquid level can be reliably detected. In addition, since it is only necessary to provide the biasing means on the substrate body side or the substrate accommodating portion side, there is no need for the curing time of the adhesive like the potting method, and assembly can be easily performed in a short time.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail with reference to the drawings showing its embodiments. FIGS. 1 to 4 show a first embodiment of the optical liquid level sensor of the present invention.

[0019] As shown in FIG. 1, this optical liquid level sensor 1 includes a housing 2 formed of polypropylene resin. As shown in FIG. 3, the housing 2 includes a substrate accommodating portion 21, and in a state where a wiring substrate 3 described later is accommodated in the substrate accommodating portion 21, a prism lens portion 22 that protrudes to the outside at a position facing a reflection type photosensor 32 mounted on a substrate main body 31. The prism lens portion 22 has a right-angled isosceles triangle cross-section, and a ridge line connecting the vertices of the triangle is formed parallel to the longitudinal axis of the substrate accommodating portion 21, and as shown in FIG. 4, it includes orthogonal prism surfaces 22a.

[0020] As shown in FIG. 3 or FIG. 4, the substrate accommodating portion 21 includes a pair of first positioning convex portions 23 and one second positioning convex portion 24. The first positioning convex portion 23 is provided along the central axis of the substrate accommodating portion 21 on the inner wall surface on the opposite side of the prism lens portion 22 on the tip side (lower end side when used as the optical liquid level sensor 1) of the substrate accommodating portion 21, and includes a tapered portion 23a and a positioning portion 23b.

[0021] The positioning portion 23b is provided on the tip side of the substrate accommodating portion 21 from the tapered portion 23a along the central axis of the substrate accommodating portion 21. The upper end surface thereof is parallel to the inner wall surface of the substrate accommodating portion 21 on the prism lens portion 22 side, and the interval between the upper end surface of the positioning portion 23b and the inner wall surface of the substrate accommodating portion 21 on the prism lens portion 22 side is such that in a state where the substrate body 31 is received on the upper end surface of the positioning portion 23b, the reflection type photosensor 32 is in contact with the inner wall surface of the substrate accommodating portion 21 on the prism lens portion 22 side substantially.

[0022] The tapered portion 23a is continuously provided with the positioning portion 23b, and is formed such that the surface on the prism lens portion 22 forming side gradually approaches the positioning portion 23b. The second positioning convex portion 24 projects from the inner wall surface of the substrate accommodating portion 21 in parallel between the first positioning convex portions 23 and between the first positioning convex portions 23.

[0023] As shown in FIGS. 3 to 7, the wiring board 3 includes a substrate body 31 and a spring material 4 as a biasing means. One end of the cable 5 is electrically connected to the substrate body 31, and a sealing material 6 is attached to the base end side. A plurality of electronic components including a reflection type photosensor 32 are mounted on the substrate body 31. A positioning recess 31a is formed on the tip side of the substrate accommodating portion 21. A pair of notch recesses 31b are formed at symmetric positions on both sides in the vicinity of the reflection type photosensor 32.

[0024] The spring material 4 is formed by bending a stainless steel wire, and includes a substantially V-shaped spring body portion 42 and a pair of substrate locking portions 41 having a substantially Z shape continuously provided at the upper ends on both sides of the V shape of the spring body portion 42. The spring body portion 42 of the spring material 4 projects toward the tip side of the substrate body 31 with the bent lower end of the V shape facing the opposite side of the mounting surface of the reflection type photosensor 32 of the substrate body 31. The substrate locking portions 41 are supported by the substrate body 31 in a state where both sides of the bent portion are fitted into the notch recesses 31b.

[0025] This optical liquid level sensor 1 is configured as described above. The reflective photosensor 32 faces the prism lens unit 22 side, and the second positioning convex portion 24 fits into the positioning recess 31a side of the substrate body 31. Then, the wiring board 3 is inserted into the substrate housing portion 21 up to the back to assemble it. That is, when the wiring board 3 is inserted into the substrate housing portion 21, first, the tip of the substrate body 31 hits the tapered portion 23a. Due to the taper of the tapered portion 23a, the tip of the substrate body 31 is pushed upward toward the prism lens unit 22 side and is pushed up to the height of the positioning portion 23b.

[0026] When the substrate body 31 reaches the positioning portion 23b, the tip of the substrate body 31 is held at the height of the positioning portion 23b. That is, the distance between the tip of the substrate body 31 and the inner wall surface of the substrate housing portion 21 on the prism lens unit 22 side becomes almost the same as the protruding height from the substrate body 31 of the mounted reflective photosensor 32. Also, when the substrate body 31 is further inserted into the tip side of the substrate housing portion 21 while being received by the positioning portion 23b, the second positioning convex portion 24 fits into the positioning recess 31a, and the reflective photosensor 32 is accurately position-regulated to face the ridge line on the prism lens unit 22 side.

[0027] Furthermore, at this time, the sealing material 6 is fitted watertightly to the open end of the housing 2, and the spring body portion 42 of the spring material 4 is in a pressure contact state with the inner wall surface of the substrate housing portion 21. This optical liquid level sensor 1 is used, for example, as shown in FIG. 8, immersed in the chemical solution of the reagent tank (bottle) T. In FIG. 8, 91 is a liquid suction nozzle for the reagent, and 92 is a reagent supply pipe.

[0028] As described above, since this optical liquid level sensor 1 is provided with the spring material 4, the substrate body 31 is biased by the spring material 4 toward the inner wall surface side on the prism lens portion 22 side of the substrate housing portion 21. Even if there are variations in the height of the reflection type photosensor 32, variations in the mounting of the reflection type photosensor 32, and variations in the molding of the substrate body 31, the emission surface of the emission element and the surface on the reception surface side of the reception element of the reflection type photosensor 32 can be brought into close contact with the inner wall surface on the prism lens portion 22 side of the substrate housing portion 21. Therefore, even if the housing 2 of this optical liquid level sensor 1 is formed of a polypropylene resin that is not as highly transparent as an acrylic resin, compared with the potting method, assembly can be easily performed in a short time, and measurement variations for each product can be eliminated.

[0029] In addition, since the housing 2 is formed of a polypropylene resin, it can be used without any problem for liquid level management of reagents that dislike contamination.

[0030] The present invention is not limited to the above-described embodiments. For example, in the above-described embodiments, a spring material obtained by bending a stainless steel wire was used as the biasing means. However, cylindrical protrusions may be formed on both sides of the substrate body, and the string winding portion of a kick spring (torsion spring) may be fitted to the protrusions. Further, a leaf spring may be used instead of the metal spring made of a wire material, or a spring made of a synthetic resin, a rubber elastic body, a resin foam, or the like may be used. In the above-described embodiments, a positioning recess is provided at the tip of the substrate body, and a positioning protrusion is provided on the inner wall surface of the substrate housing portion. However, if positioning can be achieved, the reverse may also be possible.

[0031] In the above-described embodiment, the entire housing was formed of a polypropylene resin. However, for applications where there are no problems such as contamination, other resins may be used. As long as the light emitted from the transmitting element of the reflective photosensor reaches the prism surface and the light reflected by the prism surface can enter the light receiving element, only the light-transmitting portion may be formed of a light-transmissive material, or only the prism lens portion may be formed of glass.

Explanation of Reference Numerals

[0032] 1 Optical liquid level sensor 2 Housing 21 Substrate housing portion 22 Prism lens portion 22a Prism surface 23 First positioning convex portion 23a Taper portion 23b Positioning portion 24 Second positioning convex portion 3 Wiring board 31 Substrate body 31a Positioning recess 31b Notch recess 32 Reflective photosensor 4 Spring material 41 Substrate locking portion 42 Spring body portion 5 Cable 6 Sealing material T Reagent tank 91 Liquid suction nozzle 92 Reagent supply pipe

Claims

1. A wiring board on which a reflective photosensor provided such that a light-emitting element and a light-receiving element face one side thereof is mounted on a substrate body, A housing having a substrate housing portion for housing this wiring board, In a state where the housing houses the substrate in the substrate housing portion, at least a portion of the housing facing the light-emitting element and the light-receiving element is formed of a light-transmissive material, and a prism lens portion having a prism reflecting surface for reflecting light emitted from the light-emitting element and causing it to be received by the light-receiving element. A photoelectric liquid level sensor, The photoelectric liquid level sensor, characterized in that biasing means for biasing the substrate body is provided such that the one side surface of the reflective photosensor is in close contact with the inner wall surface of the substrate housing portion.

2. The photoelectric liquid level sensor according to claim 1, wherein the prism lens portion is provided along the axial direction of the housing, and the wiring board is housed in the substrate housing portion parallel to its axis.

3. A positioning concave portion or a positioning convex portion is provided on the wiring board, and when the wiring board is housed in the substrate housing portion, the positioning concave portion or the positioning convex portion of the wiring board fits in, and a positioning convex portion or a positioning concave portion for positioning the wiring board is provided on the inner wall surface of the substrate housing portion. The photoelectric liquid level sensor according to claim 1 or claim 2.

4. The photoelectric liquid level sensor according to claim 1 or claim 2, wherein the housing is formed of a polypropylene resin or a polyethylene resin.

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