JP2007198737A - Liquid level sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level sensor excelling in measurement accuracy on a liquid level and in measurement sensitivity. <P>SOLUTION: This liquid level sensor 10 includes: a hold member 11 including a rod-like base part 21 and a plurality of insulating ribs 22 radially extending from the base part 21; and a pair of electrodes 12 and 13 wound on outer edges of the ribs 22 spirally and parallel to each other. The level of a liquid surface S of a liquid L is measured, based on a change in capacitance between the pair of electrodes 12 and 13 when they are immersed in the liquid L. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid level sensor that is immersed in a liquid and measures the level of the liquid level.

  As an apparatus for measuring the liquid level, there is a float type liquid level sensor that floats a float on the liquid and measures the liquid level based on the displacement of the float accompanying the displacement of the liquid level. However, such a float-type liquid level sensor has a limit in the measurement accuracy of the liquid level due to the accuracy of a mechanism linked to the float.

  Therefore, conventionally, a capacitive liquid level sensor has been proposed that uses a pair of electrodes and measures the liquid level based on a change in capacitance of the pair of electrodes when immersed in a liquid ( For example, see Patent Document 1).

  The liquid level sensor disclosed in Patent Document 1 has a pair of electrodes formed on an insulating substrate. Along with the displacement of the liquid level, the length of the portion of the pair of electrodes that is immersed in the liquid and the liquid is interposed between the electrodes changes, thereby changing the capacitance of the pair of electrodes. The pair of electrodes is a so-called crossed finger electrode in which a plurality of electrode fingers are formed in a comb-like shape and the electrode fingers are arranged alternately to increase the amount of change in capacitance. .

  In such a capacitive liquid level sensor, which is used for a fuel tank of an automobile or the like, in general, the surface of the electrodes is insulative so that the pair of electrodes are not sulfided or oxidized by the fuel. An anticorrosive layer is provided.

Japanese Patent No. 3029482

  By the way, in the capacitance type liquid level sensor, the capacitance of the pair of electrodes is influenced by the relative dielectric constant of a substance (dielectric) interposed between the electrodes and in the vicinity thereof. Therefore, as in the liquid level sensor disclosed in Patent Document 1, a pair of electrodes are formed on an insulating substrate, in other words, the pair of electrodes are formed on the front and / or back surfaces of the insulating substrate. What is held over the entire surface is noticeably affected by the relative permittivity of the insulating substrate in the capacitance of the pair of electrodes. For example, the measurement accuracy of the liquid level is lowered due to non-uniform thickness of the insulating substrate. There is a fear.

  Further, as in the liquid level sensor disclosed in the above-mentioned Patent Document 1, a pair of electrodes, whose front and / or back are fully held by an insulating substrate, is an insulating substrate between the electrodes. Since the liquid cannot exist in the region, the amount of change in the electrostatic capacity with respect to the displacement of the liquid level is lowered, so that the measurement sensitivity of the liquid level may be lowered.

  In addition, in the case where an insulating anticorrosion layer is provided on the surface of the electrode, the relative dielectric constant of the anticorrosion layer affects the capacitance of the pair of electrodes. For example, the thickness of the anticorrosion layer is not uniform. There is a possibility that the measurement accuracy of the level is lowered.

  This invention is made | formed in view of the situation mentioned above, The objective is to provide the liquid level sensor which is excellent in the measurement precision and measurement sensitivity of a liquid level.

  The above object is achieved by the following liquid level sensors (1) to (8) according to the present invention.

(1) a holding member including a rod-shaped base and a plurality of insulating ribs extending radially from the base;
A pair of electrodes wound around the outer edges of the plurality of ribs in parallel and spirally;
With
A liquid level sensor that measures the liquid level of the liquid based on a change in capacitance between the pair of electrodes when immersed in the liquid.

  According to the liquid level sensor having the configuration (1), the portion where the dielectric is interposed between the pair of electrodes can be suppressed as much as possible, and the measurement accuracy and measurement sensitivity of the liquid level can be improved.

  (2) The liquid level according to (1) above, wherein a guide groove is provided on an outer edge of the plurality of ribs so as to correspond to the spiral pitch of the electrode and accommodate the electrode. Sensor.

  According to the liquid level sensor having the configuration (2), it is possible to prevent the positional deviation of the pair of electrodes, and to ensure the measurement accuracy of the liquid level.

  (3) The liquid level sensor according to (1), wherein a protrusion that is crushed by the electrode when the electrode is wound is provided on an outer edge of the plurality of ribs.

  According to the liquid level sensor having the configuration (3), the electrode bites into the protrusion in a state where the electrode is wound, so that the displacement of the electrode can be prevented, and the measurement accuracy of the liquid level can be improved. Can be secured. Further, the holding member can be shared even when the electrode winding specifications are changed, and the versatility is excellent.

  (4) The holding member is formed by two-color molding in which a material for forming the plurality of protrusions is a synthetic resin that is more easily plastically deformed than a synthetic resin for forming the base and the plurality of ribs. The liquid level sensor according to (3), which is characterized in that

  According to the liquid level sensor having the configuration of (4) above, it is possible to prevent the deformation of the center base portion and the ribs by ensuring the strength while facilitating the biting of the electrode into the protrusion, thereby preventing the deformation. It is possible to prevent changes in characteristics such as the measurement accuracy of the liquid level.

  (5) The liquid level sensor according to (1) above, wherein a protrusion that is melted by heat generated by energization of the electrode and fused to the electrode is provided on an outer edge of the plurality of ribs.

  According to the liquid level sensor having the configuration of (5) above, the protrusion is fused to the electrode in a state where the electrode is wound, so that the displacement of the electrode can be prevented, and the liquid level is measured. Accuracy can be ensured. Further, the holding member can be shared even when the electrode winding specifications are changed, and the versatility is excellent.

  (6) The holding member is formed by two-color molding in which a material for forming the plurality of protrusions is a synthetic resin having a melting point lower than that of the synthetic resin for forming the base and the plurality of ribs. The liquid level sensor according to (5) above.

  According to the liquid level sensor having the above configuration (6), it is possible to ensure the heat resistance of the central base and the rib and prevent the deformation thereof while facilitating the melting of the protrusion due to the heat generated by the electrode, Thereby, it is possible to prevent changes in characteristics such as the measurement accuracy of the liquid level.

  (7) The liquid level sensor according to any one of (1) to (6), wherein the holding member includes the four ribs and has a substantially cross-shaped cross section.

  According to the liquid level sensor having the configuration (7), design and manufacture are easy.

  (8) The liquid level sensor according to any one of (1) to (7) above, wherein the spiral pitch of the electrodes is constant or gradually increases or decreases.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid level sensor excellent in the measurement precision and measurement sensitivity of a liquid level can be provided.

  Preferred embodiments of the liquid level sensor according to the present invention will be described below in detail with reference to the drawings.

(First embodiment)
1 is a front view of a liquid level sensor according to a first embodiment of the present invention, FIG. 2 is an enlarged front view of the liquid level sensor of FIG. 1, and FIG. 3 is a bottom view of the liquid level sensor of FIG. .

  As shown in FIGS. 1 to 3, the liquid level sensor 10 of the present embodiment is immersed in the liquid L in the container 1 and measures the level of the liquid level S of the liquid L. The liquid level sensor 10 includes a holding member 11 extending in the displacement direction of the liquid level S, that is, the vertical direction, and a pair of electrodes 12 and 13 held by the holding member 11.

  The holding member 11 includes a rod-like base portion 21 and four ribs 22 extending radially from the base portion 21 over substantially the entire length of the base portion 21 and is formed in a substantially cross shape in a cross section perpendicular to the longitudinal direction. The material of the base portion 21 is not particularly limited, and various materials such as synthetic resin and metal can be used in consideration of strength, resistance to liquid, and the like. As the material of the rib 22, an insulating material is used, and it is preferable to use, for example, a synthetic resin such as a polyacetal resin in consideration of strength and resistance to liquid (for example, vehicle fuel).

  The pair of electrodes 12 and 13 are spirally wound around the outer edges of the four ribs 22 of the holding member 11 in parallel with each other at an equal pitch. A plurality of guide grooves 23 are engraved on the outer edge of each rib 22 corresponding to the spiral pitch of the electrodes 12 and 13, and the electrodes 12 and 13 are inserted into the guide grooves 23 while the four ribs 22 are formed. It is wrapped around the outer edge. Note that it is preferable to use SUS, white or the like for the materials of the electrodes 12 and 13 in consideration of resistance to a liquid (for example, vehicle fuel).

  With the displacement of the liquid level S, the length of the portion of the pair of electrodes 12 and 13 where the liquid is interposed therebetween changes. As a result, the capacitance between the pair of electrodes 12 and 13 changes. And the electrostatic capacitance between a pair of electrodes 12 and 13 which changes according to the displacement of the liquid level S is measured by the drive circuit 16 connected to the terminals 14 and 15 at the upper ends of the electrodes 12 and 13. .

  Then, in the drive circuit 16, the measured capacitance between the pair of electrodes 12, 13, the relative dielectric constant of the liquid L measured in advance, and the capacitance between the pair of electrodes 12, 13 in the air The level of the liquid level S is calculated based on

  According to the liquid level sensor 10 of the present embodiment, the pair of electrodes 12 and 13 are wound around the outer edges of the plurality of ribs 22 of the holding member 11, and a gap is provided between both side surfaces of the ribs 22. Are arranged. Therefore, the portion where the dielectric is interposed between the pair of electrodes 12 and 13 can be suppressed as much as possible, and the measurement accuracy and measurement sensitivity of the level of the liquid surface S can be improved.

  Further, according to the liquid level sensor 10 of the present embodiment, the pair of electrodes 12, 13 are guide grooves provided on the outer edges of the plurality of ribs 22 of the holding member 11 corresponding to the helical pitch of the electrodes 12, 13. 23, the positional deviation of the pair of electrodes 12 and 13 can be prevented, and the measurement accuracy of the level of the liquid surface S can be ensured.

  Further, according to the liquid level sensor 10 of the present embodiment, the holding member 11 includes the four ribs 22 and is formed in a substantially cross shape in a cross section perpendicular to the longitudinal direction, which is easy to design and manufacture. is there.

(Second Embodiment)
Next, with reference to FIG.4 and FIG.5, 2nd Embodiment of the liquid level sensor which concerns on this invention is described.
FIG. 4 is a perspective view of the main part of the holding member of the second embodiment of the liquid level sensor according to the present invention, and FIG. .

  The liquid level sensor 30 of the present embodiment is immersed in the liquid L in the container 1 and measures the level of the liquid level S of the liquid L, like the liquid level sensor 10 of the first embodiment described above. The liquid level sensor 30 includes a holding member 31 extending in the displacement direction of the liquid level S and a pair of electrodes 12 and 13 held by the holding member 31.

  The holding member 31 includes a rod-like base portion 41 and four ribs 42 extending radially from the base portion 41 over substantially the entire length of the base portion 41, and a protrusion 43 having a substantially triangular cross section over the entire length of each rib 42. And is formed in a substantially cross shape in a cross section perpendicular to the longitudinal direction.

  In the holding member 31 of the present embodiment, the base 41 and the four ribs 42 are integrally formed of, for example, the polyacetal resin described above, and the base 41 and the material for forming the protrusions 43 provided on each rib 42 are used. It is formed by two-color molding using a synthetic resin such as a polyethylene resin that is more susceptible to plastic deformation than the synthetic resin forming the four ribs 42.

  The pair of electrodes 12 and 13 are spirally wound around the outer edges of the four ribs 42 of the holding member 31 in parallel with each other at an equal pitch. Here, the electrodes 12 and 13 are wound around the outer edges of the four ribs 42 while squeezing into the protrusions 43 so as to crush the apex portions of the protrusions 43 protruding from the outer edges of the ribs 42. .

  The measurement of the level of the liquid level S by the liquid level sensor 30 configured in this way is the same as that of the liquid level sensor 10 of the first embodiment described above, and thus the description thereof is omitted.

  According to the liquid level sensor 30 of the present embodiment, the protrusions 43 that are crushed by the electrodes 12 and 13 are provided around the outer edges of the plurality of ribs 42 of the holding member 31. In the state where the electrodes 12 and 13 are wound, the electrodes 12 and 13 bite into the projections 43, so that the positional deviation of the electrodes 12 and 13 can be prevented and the measurement accuracy of the level of the liquid surface S can be ensured. I can do it. Furthermore, the holding member 31 can be shared even when the winding specifications of the electrodes 12 and 13 (for example, the helical pitch) are changed, and the versatility is excellent.

  Further, according to the liquid level sensor 30 of the present embodiment, the holding member 31 is a synthetic resin that is more likely to cause plastic deformation of the material forming the plurality of protrusions 43 than the synthetic resin forming the base 41 and the plurality of ribs 42. It is formed by the two-color molding, and while making the electrodes 12 and 13 bite into the protrusions 43, the center base 41 and the ribs 42 can ensure strength and prevent deformation thereof, Thereby, characteristic changes such as measurement accuracy of the level of the liquid level S can be prevented.

  Other functions and effects are the same as the functions and effects exhibited by the liquid level sensor 10 according to the first embodiment described above, and a description thereof will be omitted.

(Third embodiment)
Next, a third embodiment of the liquid level sensor according to the present invention will be described with reference to FIG.
FIG. 6 is a perspective view of a main part of a third embodiment of the liquid level sensor according to the present invention.

  The liquid level sensor 50 of the present embodiment is immersed in the liquid L in the container 1 and measures the level of the liquid level S of the liquid L, similarly to the liquid level sensor 10 of the first embodiment described above. The liquid level sensor 50 includes a holding member 51 extending in the displacement direction of the liquid level S and a pair of electrodes 12 and 13 held by the holding member 51.

  The holding member 51 includes a rod-like base portion 61 and four ribs 62 extending radially from the base portion 61 over substantially the entire length of the base portion 61, and a protrusion 63 having a substantially triangular cross section over the entire length of each rib 62. And is formed in a substantially cross shape in a cross section perpendicular to the longitudinal direction.

  In the holding member 51 of the present embodiment, the base 61 and the four ribs 62 are integrally formed of, for example, the polyacetal resin described above, and further, the base 61 and the material for forming the protrusion 63 provided on each rib 62 are used. It is formed by two-color molding using a synthetic resin such as a polyethylene resin having a lower melting point than the synthetic resin forming the four ribs 62.

  The pair of electrodes 12 and 13 are spirally wound around the outer edges of the four ribs 62 of the holding member 51 in parallel with each other at an equal pitch. Then, the end portions 12a and 13a of the electrodes 12 and 13 are electrically connected, and a predetermined DC voltage is applied between the terminals 14 and 15 at the upper ends of the electrodes 12 and 13, thereby providing the outer edges of the ribs 62. The projection 63 is melted by the heat generated by the electrodes 12 and 13 by energization, and is fused to the electrodes 12 and 13.

  The measurement of the level of the liquid level S by the liquid level sensor 50 configured in this way is the same as that of the liquid level sensor 10 of the first embodiment described above, and thus the description thereof is omitted.

  According to the liquid level sensor 50 of the present embodiment, the protrusions 63 that are melted by heat generated by energization of the electrodes 12 and 13 and are fused to the electrodes 12 and 13 are provided on the outer edges of the plurality of ribs 62 of the holding member 51. Therefore, it is possible to prevent the displacement of the electrodes 12 and 13 and ensure the measurement accuracy of the level of the liquid surface S. Furthermore, the holding member 51 can also be shared when changing the winding specifications (for example, helical pitch) of the electrodes 12 and 13, and the versatility is excellent.

  Further, according to the liquid level sensor 50 of the present embodiment, the holding member 51 is made of a synthetic resin having a melting point lower than that of the synthetic resin forming the base 61 and the plurality of ribs 62. It is formed by two-color molding, facilitating the melting of the protrusion 63 due to the heat generated by the electrodes 12, 13, while ensuring the heat resistance of the central base 61 and the rib 62 and preventing its deformation, Thereby, characteristic changes such as measurement accuracy of the level of the liquid level S can be prevented.

  Other functions and effects are the same as the functions and effects exhibited by the liquid level sensor 10 according to the first embodiment described above, and a description thereof will be omitted.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  For example, as shown in FIG. 7, in the holding member 51 of the liquid level sensor 50 according to the third embodiment described above, the base 61 and the four ribs 62 that are integrally formed have an appropriate interval in the longitudinal direction. In this case, a plurality of lightening portions 64 may be formed. According to this, the dielectric material arrange | positioned in the vicinity of a pair of electrodes 12 and 13 can be reduced further, and the measurement sensitivity of the level of the liquid level S can further be improved. Needless to say, the liquid level sensors 10 and 30 of the first and second embodiments described above can be similarly provided with a lightening portion in the holding members 11 and 31.

  In the liquid level sensor 10 according to the first embodiment described above, the pair of electrodes 12 and 13 are spirally wound around the outer edges of the four ribs 22 of the holding member 11, and the spiral pitch is equal. However, the pitch may be a gradually changing pitch that gradually becomes denser from the upper end toward the lower end as shown in FIG. In this case, the measurement sensitivity at the lower end of the liquid level sensor 10 is increased, and the liquid level S when the liquid L in the container 1 becomes small and the liquid level S approaches the bottom surface of the container 1. Level can be measured with high accuracy. Needless to say, in the liquid level sensors 30 and 50 of the second and third embodiments described above, the spiral pitch of the pair of electrodes 12 and 13 can be set to a gradually changing pitch.

It is a front view of 1st Embodiment of the liquid level sensor which concerns on this invention. It is an enlarged front view of the liquid level sensor of FIG. It is a bottom view of the liquid level sensor of FIG. It is a principal part perspective view of the holding member of 2nd Embodiment of the liquid level sensor which concerns on this invention. It is a principal part perspective view which shows the state by which the pair of electrode was hold | maintained at the holding member of FIG. It is a principal part perspective view of 3rd Embodiment of the liquid level sensor which concerns on this invention. It is a principal part perspective view of the modification of the liquid level sensor shown in FIG. It is a front view of the modification of the liquid level sensor shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid level sensor 11 Holding member 12 Electrode 13 Electrode 21 Base 22 Rib 23 Guide groove S Liquid level

Claims (8)

A holding member including a rod-shaped base and a plurality of insulating ribs extending radially from the base;
A pair of electrodes wound around the outer edges of the plurality of ribs in parallel and spirally;
With
A liquid level sensor that measures the liquid level of the liquid based on a change in capacitance between the pair of electrodes when immersed in the liquid.   2. The liquid level sensor according to claim 1, wherein a guide groove is provided on an outer edge of each of the plurality of ribs so as to correspond to a spiral pitch of the electrode and accommodates the electrode.   The liquid level sensor according to claim 1, wherein a protrusion that is crushed by the electrode when the electrode is wound is provided on an outer edge of the plurality of ribs.   The holding member is formed by two-color molding in which a material for forming the plurality of protrusions is a synthetic resin that is more easily plastically deformed than a synthetic resin for forming the base and the plurality of ribs. The liquid level sensor according to claim 3.   2. The liquid level sensor according to claim 1, wherein a protrusion that melts by heat generated by energization of the electrode and is fused to the electrode is provided on an outer edge of the plurality of ribs.   The holding member is formed by two-color molding in which a material for forming the plurality of protrusions is a synthetic resin having a lower melting point than a synthetic resin for forming the base and the plurality of ribs. 5. The liquid level sensor according to 5.   The liquid level sensor according to any one of claims 1 to 6, wherein the holding member includes four ribs and has a substantially cross-shaped cross section.   The liquid level sensor according to any one of claims 1 to 7, wherein the spiral pitch of the electrodes is constant or gradually increases or decreases.

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