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 technology]

[0002] For example, electric pumps are used when refilling kerosene from a kerosene can into an airtight oil tank (cartridge tank) or oil tank for a household kerosene stove or kerosene fan heater. Some electric pumps of this type are equipped with a photoelectric liquid level sensor at the end of the fuel supply pipe so that fuel supply can be stopped at a level where kerosene does not spill out of the tank, and the motor automatically stops when fuel supply has reached a specified level.

[0003] The photoelectric liquid level sensor has already been proposed, which includes a transparent resin housing with a prism-shaped tip and a wiring board on which a reflective photosensor consisting of a light-emitting element and a light-receiving element is mounted, and the wiring board is accommodated in a wiring board accommodating section within the housing so that the reflective photosensor (photoelectric sensor) portion faces a prism lens section that protrudes from the wall of the housing to the outside. When the prism lens section is submerged in liquid, the light emitted from the light-emitting element is hardly reflected by the prism reflective surface of the prism lens section and is scattered in the liquid, so that little of it returns to the light-receiving element. When the prism lens section is in the air, the light is reflected by the prism reflective surface of the prism lens section and returns to the light-receiving element, and it is possible to determine whether the liquid level in the tank 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] Japanese Utility Model Application Publication No. 64-8636 [Patent Document 2] Japanese Patent Application Publication No. 8-75531 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to improve the detection performance of the photoelectric liquid level sensor described above, it is necessary to use it effectively without reducing the optical output characteristics. However, if there is an air layer between the reflective photosensor (reflective photointerrupter) and the inner wall surface of the wiring board accommodating section, the effective amount of light will change due to variations in the board body of the wiring board, the components mounted on the board body, and assembly variations, which may result in a large range of variation, such as always determining that the sensor is in liquid or producing a product that is just at the threshold level. In addition, some light may always be reflected by the prism lens section even in liquid, causing it to be determined that the sensor is in air.

[0006] On the other hand, in order to solve the above problem, as shown in Figure 9, there is also a photoelectric liquid level sensor 100 that employs a so-called potting method, in which a transparent resin adhesive (potting liquid) is filled between the wiring board 300 and the inner wall surface of the substrate accommodating section 210 of the housing 200, and a transparent resin hardened layer 400 is formed between the reflective photosensor 320 and the inner wall surface of the substrate accommodating section 210, thereby eliminating the air layer. In other words, in the case of a photoelectric liquid level sensor 100 using a potting method, even if there is variation in components such as the substrate body 310 of the wiring board 300 and the reflective photosensor 320 mounted on the substrate body 310, or variation in assembly, a transparent resin hardened layer 400 is formed between the reflective photosensor 220 and the inner wall surface of the substrate accommodating section 210, so that the light emitted from the light-emitting element reaches the prism reflecting surface of the prism lens section 220 in almost the same state, resulting in little change in the amount of light.

[0007] However, with the potting method, there is the problem that it takes a long time for the transparent resin adhesive to harden, and there is also the risk that air bubbles may be mixed into the hardened body or the adhesive may peel off during the reaction and hardening of the transparent resin adhesive, which may result in sensor detection problems. In other words, if a cured body layer containing air bubbles is formed or if adhesive delamination occurs, the degree of scattering and refraction of light will vary depending on the size and position of the air bubbles or adhesive delamination, resulting in a wide range of variation, with products always being judged to be airborne or just barely meeting the threshold.

[0008] This tendency becomes even stronger when the housing is made of a polypropylene resin or the like which has poor transparency. Therefore, the resin that can be used for the housing is also limited.

[0009] In view of the above circumstances, the present invention aims to provide a photoelectric liquid level sensor that is easy to assemble and can reliably detect the liquid level without variation in the measurement accuracy of the reflective photosensor, even if there is variation in the substrate body of the wiring board or the components mounted on the substrate body, or variation in assembly. [Means for solving the problem]

[0010] In order to achieve the above object, the photoelectric liquid level sensor of the present invention comprises a wiring board on which a reflective photosensor having a light-emitting element and a light-receiving element disposed so as to face one side of the wiring board is mounted, and a housing having a board accommodation section in which the wiring board is accommodated, and when the board is accommodated in the board accommodation section, at least the portion of the housing facing the light-emitting element and the light-receiving element is formed of a light-transmitting material, and the housing comprises a prism lens section having a prism reflection surface that reflects light emitted from the light-emitting element and causes it to be received by the light-receiving element, and the photoelectric liquid level sensor further comprises an urging means for urging the board body so that the one side of the reflective photosensor is in close contact with the inner wall surface of the board accommodation section. A positioning recess or a positioning protrusion is provided on the wiring board, and when the wiring board is accommodated in the board accommodation section, the positioning recess or the positioning protrusion of the wiring board fits into the positioning recess or the positioning protrusion, and the positioning recess or the positioning recess is provided on the inner wall surface of the board accommodation section to position the wiring board. It is characterized by the following.

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

[0012] The photoelectric liquid level sensor of the present invention may be configured such that the prism reflecting surface is provided along the axial direction of the housing, and the wiring board is accommodated in the board accommodating portion parallel to the axis.

[0014] The material of the casing of the photoelectric liquid level sensor of the present invention is not particularly limited as long as the portion facing the transmitting element and receiving element of the reflective photosensor is made of a light-transmitting material, but examples include acrylic resin, polyester resin, polycarbonate resin, polypropylene resin, and polyethylene resin. Polypropylene resin and polyethylene resin are preferred when corrosion resistance to liquids is desired or when the sensor is used to manage the liquid level of liquids where even the slightest contamination or fouling cannot be tolerated. [Effects of the Invention]

[0015] As described above, the photoelectric liquid level sensor of the present invention comprises a wiring board on which a reflective photosensor, with a light-emitting element and a light-receiving element facing one side thereof, is mounted on a board body, and a housing having a board accommodating section in which the wiring board is accommodated, and when the housing accommodates the board in the board accommodating section, at least the portion of the housing facing the light-emitting element and the light-receiving element is formed of an optically transparent material, and the housing comprises a prism lens section having a prism reflecting surface that reflects light emitted from the light-emitting element and causes it to be received by the light-receiving element.The photoelectric liquid level sensor is also provided with a biasing means for biasing the board body so that the one side of the reflective photosensor is in close contact with the inner wall surface of the board accommodating section.Therefore, the biasing means can keep the one side of the reflective photosensor facing the light-emitting element and the light-receiving element in close contact with the inner wall surface of the board accommodating section, even if the board body is bent, there is variation in the height of the reflective photosensor, there is variation in the mounting of the reflective photosensor, or there is variation in the molding of the board body.

[0016] In other words, even if there is variation in the substrate body of the wiring board or the components mounted on the substrate body, or variation in assembly, almost no air layer is formed between the reflective photosensor and the inner wall surface of the substrate accommodating section, so there is no variation in the measurement accuracy of the reflective photosensor, and the liquid level can be detected reliably. Furthermore, since it is only necessary to provide a biasing means on the substrate body or substrate accommodating portion side, there is no need for adhesive hardening time as in the potting method, and assembly can be easily carried out in a short time. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view of a first embodiment of a photoelectric liquid level sensor of the present invention; [Figure 2] FIG. 2 is a side view of the photoelectric liquid level sensor of FIG. 1. [Figure 3] 2 is a cross-sectional view of the photoelectric liquid level sensor of FIG. 1 taken along a plane parallel to the substrate body. [Figure 4] 3 is a cross-sectional view taken along the line AA in FIG. 2. [Figure 5] FIG. 2 is a perspective view of the photoelectric liquid level sensor of FIG. 1 with the housing removed. [Figure 6] FIG. 4 is a cross-sectional view of the photoelectric liquid level sensor of FIG. 3 with the housing removed. [Figure 7] FIG. 2 is a bottom view of the photoelectric liquid level sensor of FIG. 1 with the housing removed. [Figure 8] FIG. 2 is a diagram showing an example of use of the photoelectric liquid level sensor of FIG. 1. [Figure 9] FIG. 1 is a cross-sectional view of a conventional photoelectric liquid level sensor. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below with reference to the drawings showing embodiments thereof. 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 made of polypropylene resin. As shown in Figure 3, the housing 2 has a substrate accommodating section 21 and a prism lens section 22 that protrudes outward in a position facing a reflective photosensor 32 mounted on the substrate main body 31 when the wiring substrate 3 described later is accommodated in the substrate accommodating section 21. The prism lens portion 22 has a cross section in the shape of a right-angled isosceles triangle, with the ridge line connecting the vertices of the triangle formed parallel to the longitudinal axis of the substrate accommodating portion 21, and is provided with orthogonal prism surfaces 22a, as shown in Figure 4.

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

[0021] The positioning portion 23b is provided along the central axis of the substrate accommodating portion 21, closer to the tip of the substrate accommodating portion 21 than the tapered portion 23a, and its upper end face is parallel to the inner wall surface of the substrate accommodating portion 21 on the prism lens portion 22 side, and the distance between the upper end face 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 when the substrate main body 31 is received on the upper end face of the positioning portion 23b, the reflective photosensor 32 will be in contact with the inner wall surface of the substrate accommodating portion 21 on the prism lens portion 22 side.

[0022] The tapered portion 23a is connected to the positioning portion 23b, and is formed so that the surface on the side where the prism lens portion 22 is formed gradually approaches the positioning portion 23b. The second positioning protrusion 24 protrudes from the inner wall surface of the substrate accommodating section 21 between the first positioning protrusions 23 and parallel to the first positioning protrusions 23.

[0023] As shown in Figures 3 to 7, the wiring board 3 comprises a board main body 31 and a spring material 4 as a biasing means, one end of a cable 5 is electrically connected to the board main body 31, and a sealing material 6 is attached to the base end side. The substrate main body 31 has multiple electronic components mounted thereon, including a reflective photosensor 32, and has a positioning recess 31a drilled at the tip end of the substrate accommodating section 21, as well as a pair of notched recesses 31b drilled at symmetrical positions on both sides of the reflective photosensor 32 near the same.

[0024] The spring material 4 is formed by bending a stainless steel wire, and includes a spring body 42 having a generally V-shape and a pair of board locking portions 41 having a generally V-shape connected to the upper ends of both sides of the V shape of the spring body 42. The spring material 4 is supported by the substrate body 31 with the spring main body portion 42 having the V-shaped bent lower end facing the tip side of the substrate main body 31 and protruding toward the side opposite the mounting surface of the substrate main body 31 on which the reflective photosensor 32 is mounted, and with the substrate locking portion 41 fitted into the notched recess 31b on both sides of the bent portion.

[0025] This optical liquid level sensor 1 is configured as described above, with the reflective photosensor 32 facing the prism lens portion 22, the second positioning protrusion 24 fitting into the positioning recess 31a side of the substrate main body 31, and the wiring board 3 being inserted to the back of the substrate accommodating portion 21 starting from the first, and assembled. That is, when the wiring board 3 is inserted into the board accommodating section 21, the tip of the board main body 31 first hits the tapered section 23a, but the taper of the tapered section 23a pushes the tip of the board main body 31 up toward the prism lens section 22 and up to the height of the positioning section 23b.

[0026] Then, when the substrate main body 31 reaches the positioning portion 23b, the tip of the substrate main body 31 is held at the height of the positioning portion 23b, that is, the distance between the tip of the substrate main body 31 and the inner wall surface of the substrate accommodating portion 21 on the prism lens portion 22 side becomes a distance that is approximately the same as the protruding height of the mounted reflective photosensor 32 from the substrate main body 31. Furthermore, when the substrate main body 31 is further inserted into the tip side of the substrate accommodating section 21 while being received in the positioning section 23b, the second positioning protrusion 24 fits into the positioning recess 31a, and the reflective photosensor 32 is accurately positioned facing the ridge line on the prism lens section 22 side.

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

[0028] As described above, this optical liquid level sensor 1 is equipped with a spring material 4, so that the substrate main body 31 is urged by the spring material 4 toward the inner wall surface of the substrate accommodating section 21 on the prism lens section 22 side, and even if there is variation in the height of the reflective photosensor 32, variation in the implementation of the reflective photosensor 32, or variation in the molding of the substrate main body 31, the transmitting surface of the transmitting element and the receiving surface of the receiving element of the reflective photosensor 32 can be brought into close contact with the inner wall surface of the substrate accommodating section 21 on the prism lens section 22 side. Therefore, even if the housing 2 of this optical liquid level sensor 1 is made of polypropylene resin, which is not as transparent as acrylic resin, assembly can be completed easily and in a shorter time than with the potting method, and measurement variations between products can be eliminated.

[0029] Furthermore, since the housing 2 is made of polypropylene resin, it can be used without any problems for managing the liquid surface of reagents that must be kept free from 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 is used as the biasing means. However, cylindrical protrusions may be formed on both sides of the substrate body, and the helical portion of the kick spring (torsion spring) may be fitted into the protrusions. Furthermore, a leaf spring may be used instead of the metal spring made of wire, or a spring made of synthetic resin, a rubber elastic body, a resin foam, or the like may be used. In the above embodiment, the positioning recess is provided at the tip of the substrate body, and the positioning protrusion is provided on the inner wall surface of the substrate accommodating portion, but the reverse may be possible as long as positioning is possible.

[0031] In the above embodiment, the entire housing is made of polypropylene resin, but other resins may be used if the application does not involve problems such as contamination, and as long as at least the light emitted from the transmitting element of the reflective photosensor can reach the prism surface and the light reflected from the prism surface can enter the light receiving element, only the translucent portion may be made of a translucent material, or only the prism lens portion may be made of glass. [Explanation of symbols]

[0032] 1 Optical liquid level sensor 2. Housing 21 Substrate storage section 22 Prism lens section 22a Prism surface 23 First positioning protrusion 23a Tapered section 23b Positioning part 24 Second positioning protrusion 3. Wiring board 31 Board body 31a Positioning recess 31b Notched recess 32 Reflective photosensor 4 Spring material 41 Circuit board locking portion 42 Spring body 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 is mounted, the photosensor having a light emitting element and a light receiving element disposed on one side of the wiring board; a housing having a board accommodating portion for accommodating the wiring board; a prism lens portion having a prism reflecting surface that reflects light emitted from the light emitting element and that reflects the light to the light receiving element, the prism lens portion having a prism reflecting surface that reflects the light emitted from the light emitting element and that reflects the light to the light receiving element, when the substrate is accommodated in the substrate accommodating portion; a biasing means for biasing the substrate body so that the one side surface of the reflective photosensor is in close contact with an inner wall surface of the substrate accommodating portion; A photoelectric liquid level sensor characterized in that a positioning recess or a positioning protrusion is provided on the wiring board, and when the wiring board is accommodated in the board accommodating section, a positioning protrusion or a positioning recess is provided on the inner wall surface of the board accommodating section into which the positioning recess or positioning protrusion of the wiring board fits, thereby positioning the wiring board.

2. 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 accommodated in the board accommodating portion in parallel with the axis of the wiring board.

3. 3. The photoelectric liquid level sensor according to claim 1, wherein the housing is made of polypropylene resin or polyethylene resin.

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