JP4296992B2 - Liquid level sensor - Google Patents

Description

  The present invention relates to a liquid level liquid quality sensor for detecting the liquid level and liquid quality of various oils such as engine oil, gear oil, torque converter oil, CVT oil, brake oil, etc. for automobiles, construction machines, aircrafts and the like.

  A conventional liquid level liquid quality sensor will be described below with reference to the drawings.

  FIG. 8 is a front view of a detection element of a conventional liquid level liquid quality sensor.

  In FIG. 8, the liquid level liquid quality sensor includes a detection element 1 that detects the liquid level liquid quality of the liquid, and a signal processing circuit (not shown) that is connected to the detection element 1 and processes a signal of the detection element 1. It has. The detection element 1 is formed by arranging a pair of comb-shaped detection electrodes 3 on a rectangular printed circuit board 2 so as to mesh with each other at intervals, and is detected by contacting with various liquids such as oil. The capacitance of the electrode is detected to detect the liquid level liquid quality.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP-A-63-79016

  In the above-described conventional configuration, if the liquid is displaced beyond the length of the comb-shaped detection electrode 3, the liquid level cannot be detected properly, and even if an attempt is made to replace the detection element with a longer detection electrode 3. However, there is a problem that the position of the newly installed detection element cannot be easily fixed in place of the already installed detection element.

  The present invention solves the above-described problems, and an object of the present invention is to provide a liquid level liquid quality sensor in which a detection element can be easily replaced in accordance with a liquid for detecting the liquid level liquid quality.

In order to achieve the above object, the present invention particularly has a detection element having a liquid level detection electrode for detecting the liquid level and a liquid quality detection electrode for detecting the liquid quality, and one of the front and back surfaces of the substrate. The liquid level detection electrode is arranged on the surface, and the liquid quality detection electrode is arranged on the other surface of the front and back surfaces of the substrate. According to this configuration, the liquid level detection electrode detects the liquid level. And the liquid quality detection electrode for detecting the liquid quality, the liquid level and the liquid quality can be accurately detected, and the liquid level detection electrode is disposed on one surface of the front and back surfaces of the substrate. Since the liquid quality detection electrode is arranged on the other surface of the front and back surfaces, the liquid level detection electrode and the liquid quality detection electrode can be easily arranged in a limited substrate area.

The liquid level liquid quality sensor of the present invention is provided by arranging a pair of comb-shaped detection electrodes on a substrate so as to be engaged with each other with a space therebetween, and detecting the capacitance of the detection electrodes by contacting with the liquid. A combination of a detection element that detects the liquid level liquid quality, a cylindrical case that houses the detection element, and a main body case to which the cylindrical case is joined, and the cylindrical case is immersed in the liquid And the detection element includes a liquid level detection electrode for detecting the liquid level and a liquid quality detection electrode for detecting the liquid quality, and the detection element is provided on one surface of the front and back surfaces of the substrate. The liquid level detection electrode is disposed, and the liquid quality detection electrode is disposed on the other surface of the front and back surfaces of the substrate. According to this configuration, the liquid level detection electrode and the liquid quality are detected. Because it has a liquid quality detection electrode that detects the liquid level and the liquid quality, Since the liquid level detection electrode is disposed on one surface of the front and back surfaces of the substrate, and the liquid quality detection electrode is disposed on the other surface of the front and back surfaces of the substrate, The liquid level liquid quality sensor can be provided in which the liquid level detection electrode and the liquid quality detection electrode can be easily arranged in the area.

  Hereinafter, a liquid level liquid quality sensor according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view of a liquid level liquid quality sensor according to an embodiment of the present invention, FIG. 2 is a perspective view thereof, FIG. 3 is a sectional view thereof, and FIG. FIG. 4B is a plan view of the back side of the detection element that is the main part, FIG. 5 is an enlarged sectional view of part A in FIG. 3, and FIG. 6 is a perspective view of a presser spring that is the main part. FIG. 7 is a diagram for explaining the use state.

  1 to 4, a liquid level liquid quality sensor according to an embodiment of the present invention includes a detection element 11 that detects a liquid level liquid quality of a liquid, and an outer case 12 that houses the detection element 11. .

  The outer case 12 is provided by combining a cylindrical case 13 that houses the detection element 11 and a main body case 14 to which the cylindrical case 13 is joined. The main body case 14 accommodates a circuit board 16 on which an electronic component 15 is mounted, and is provided with a metal terminal portion 17 that is electrically connected to the electronic component 15. The electronic component 15 forms a signal processing circuit that processes the signal of the detection element 11.

  As for the combination, the cylindrical case 13 and the main body case 14 may be joined to each other by screwing, fitting, bonding, connector, or the like, but the cylindrical case 13 and the main body case 14 can be attached and detached. It is joined. The cylindrical case 13 and the main body case 14 are each formed by injection molding and joined. At this time, if the cylindrical case 13 and the main body case 14 are integrally molded, it is not suitable because it is difficult to detach.

  The detection element 11 is formed by arranging a pair of comb-shaped detection electrodes 18 on a polyimide film substrate 19 so as to mesh with each other with a gap therebetween. As the substrate 19, a general ceramic having a relative dielectric constant of about 10 is not suitable because it has a capacity, and a polyimide film having a dielectric constant of about 3.5 and hardly having a capacity is suitable. The detection electrode 18 is formed on the polyimide film substrate 19 by a thick film printing method, and is drawn out to the end of the substrate 19 by a lead wire 20. 4A, on the front side of the detection element 11, the electrode width of the detection electrode 18 is about 12 mm, the length is about 60 mm, the distance between the electrodes is about 0.5 mm, and the line width is about 0.5 mm. 4B, on the back side of the detection element 11, the electrode width of the detection electrode 18 is about 12 mm, the length is about 20 mm, the distance between the electrodes is about 0.5 mm, and the line width is about 0.5 mm. It is said.

  This detection element 11 has a liquid level detection electrode 18 for detecting the liquid level and a liquid quality detection electrode 18 for detecting the liquid quality, and the liquid level detection electrode 18 is arranged on the surface of the substrate 19. In addition, a liquid quality detection electrode 18 is disposed on the back surface of the substrate 19. The detection electrode 18 is provided with a metal pad portion 21 that is electrically connected to the metal terminal portion 17 provided on the main body case 14 through the lead wire 20, and the metal pad portion 21 is all formed on the surface of the substrate 19. ing. The main material of the detection electrode 18 and the main material of the metal pad portion 21 are carbon, and a resin paste containing carbon is formed by thick film printing, and the surface of the metal terminal portion 17 is plated with gold. In addition, if the metal terminal part 17 and the metal pad part 21 use the material whose mutual surface hardness approximates, the abrasion accompanying a hardness difference can be suppressed.

  5 and 6, the metal pad portion 21 and the metal terminal portion 17 are disposed so as to face each other and are brought into electrical contact by pressing the substrate 19 with a pressing spring 22. In particular, the presser spring 22 is provided with two arm portions 24 having a hemispherical protrusion 23 at the tip. If the protrusion 23 of the arm portion 24 presses the metal pad portion 21, the presser spring 22 is surely secured. Can be pressed.

  Since the two arm portions 24 are independent of each other, even if there is a dimensional variation in the exterior case 12, the metal terminal portion 17, etc., this variation can be absorbed. It is desirable that the generated load per one arm portion 24 is set to 400 to 600 gf. In this case, in the thermal shock endurance test in which the atmosphere at 130 ° C. and −40 ° C. is alternately repeated within a short time, the resistance value generated at the contact portion is about 10Ω at the maximum even if it is repeated about 1000 times. Has no effect.

  Then, as shown in FIG. 7, the cylindrical case 13 of the outer case 12 is immersed in a liquid such as engine oil 25 and the liquid is brought into contact with the detection element 11 to detect the capacitance of the detection electrode 18. The liquid level and liquid quality are detected.

  With the above configuration, the detection element 11 is housed in the cylindrical case 13, and the cylindrical case 13 is joined to the main body case 14 in combination, so that the cylindrical case 13 can be freely detached from the main body case 14. That is, when the liquid is displaced beyond the length of the comb-shaped detection electrode 18 and proper detection cannot be performed, the cylindrical case 13 containing the detection element 11 having the long detection electrode 18 can be replaced with the main body. That's fine. In the above configuration, the detection element 11 having a different length of the detection electrode 18 and the cylindrical case 13 that houses the detection element can be freely selected according to the liquid and can be easily replaced.

  Since the detection element 11 includes the liquid level detection electrode 18 for detecting the liquid level and the liquid quality detection electrode 18 for detecting the liquid quality, the liquid level and the liquid quality can be accurately detected. If the liquid level detection electrode 18 is disposed on one surface of the substrate 19 and the liquid quality detection electrode 18 is disposed on the other surface of the substrate 19, the liquid level detection electrode can be easily formed in a limited area of the substrate 19. 18 and the liquid quality detection electrode 18 can be arranged.

  Since the substrate 19 is made of a polyimide film, the dielectric constant is low and it becomes difficult to have a capacity, and since it has flexibility, it is possible to suppress cracking and chipping.

  The body case 14 is provided with the metal terminal portion 17 electrically connected to the electronic component 15, and the detection electrode 18 is provided with the metal pad portion 21 electrically connected to the metal terminal portion 17 through the lead wire 20. The detection element 11 housed in the cylindrical case 13 and the electronic component 15 housed in the main body case 14 can be electrically connected.

  Since the main material of the detection electrode 18 is carbon, no migration occurs even if moisture adheres to the detection electrode 18 and the characteristics do not deteriorate.

  Since the main material of the metal pad portion 21 is carbon and the surface of the metal terminal portion 17 is plated with gold, the surface hardness of the metal pad portion 21 and the metal terminal portion 17 is approximated, and the hardness difference is accompanied. Wear can be suppressed. When the main material of the metal pad portion 21 is silver, the surface of the metal terminal portion 17 is not plated, but if the commonly used tin plating is used, the surface hardness approximates and wear due to the hardness difference occurs. Can be suppressed.

  As described above, the liquid level liquid quality sensor according to the present invention can freely select a detection element having a different length of the detection electrode and a cylindrical case for housing the detection element in accordance with the liquid. Such as engine oil, gear oil, torque converter oil, CVT oil, brake oil, and the like can be applied to liquid level liquid quality sensors that detect the liquid level and quality of various oils.

The disassembled perspective view of the liquid level liquid quality sensor in one embodiment of this invention Same perspective view Cross section Plan view of the detector element Enlarged sectional view of part A in FIG. The perspective view of the presser spring which is the principal part Diagram explaining the same usage state Front view of detection element, which is the main part of a conventional liquid level liquid quality sensor

DESCRIPTION OF SYMBOLS 11 Detection element 12 Exterior case 13 Cylindrical case 14 Main body case 15 Electronic component 16 Circuit board 17 Metal terminal part 18 Detection electrode 19 Substrate 20 Lead wire 21 Metal pad part 22 Pressing spring 23 Protrusion 24 Arm part 25 Engine oil

Claims (1)

A pair of comb-shaped detection electrodes are arranged on the substrate so as to mesh with each other with a gap therebetween, and the liquid level liquid quality is detected by detecting the capacitance of the detection electrodes by contacting with the liquid. A detection element; a cylindrical case that houses the detection element; and a main body case to which the cylindrical case is joined, and an outer case formed by immersing the cylindrical case in a liquid. The element has a liquid level detection electrode for detecting the liquid level and a liquid quality detection electrode for detecting the liquid quality, the liquid level detection electrode is disposed on one surface of the front and back surfaces of the substrate, and the substrate A liquid level liquid quality sensor in which the liquid quality detection electrode is disposed on the other surface of the front and back surfaces.

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