liquid sensor

Abstract

To provide a liquid sensor that can achieve a relatively wide detection range and relatively high detection sensitivity for foreign matter in a liquid. [Solution] The liquid sensor detects the amount of foreign matter in a liquid by immersing at least a portion of it in the liquid. The liquid sensor comprises a substrate and a detection circuit. The substrate includes a first electrode and a second electrode. The first end face of the first electrode and the second end face of the second electrode face each other with a predetermined gap between them. A capacitor is formed between the first and second end faces. The respective areas of the first and second end faces, as well as the predetermined gap, satisfy the conditions for an edge effect to occur in the capacitor. The detection circuit detects the amount of foreign matter based on the capacitance of the capacitor.

Description

Technical Field

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

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2024-3591 (Patent Document 1) discloses an oil change determination notification device. In this oil change determination notification device, the amount of contamination mixed into the oil is estimated, and the oil change timing is determined based on the amount of contamination mixed in.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a liquid sensor capable of realizing a relatively wide detection range and relatively high detection sensitivity with respect to foreign matter in a liquid.

Means for Solving the Problems

[0005] A liquid sensor according to an aspect of the present invention detects the amount of foreign matter in a liquid by immersing at least a part thereof in the liquid. The liquid sensor includes a substrate and a detection circuit. The substrate includes a first electrode and a second electrode. A first end face of the first electrode and a second end face of the second electrode face each other with a predetermined interval therebetween. A capacitor is formed between the first end face and the second end face. The area of each of the first end face and the second end face, and the predetermined interval satisfy the conditions for the edge effect to occur in the capacitor. The detection circuit detects the amount of foreign matter based on the capacitance of the capacitor.

[0006] In this liquid sensor, an edge effect occurs in the capacitor formed between the first and second end faces, causing electric field lines to bulge outwards from the end of the capacitor opposite to the substrate side. As a result of the edge effect, the density of electric field lines increases near the end of the capacitor opposite to the substrate side. Therefore, this liquid sensor can achieve a relatively wide detection range and relatively high detection sensitivity for foreign objects because the electric field lines bulge outwards from the capacitor and the density of electric field lines increases near the end of the capacitor opposite to the substrate side.

[0007] In the liquid sensor described above, a through hole may be formed in the first electrode, a second electrode may be placed inside the through hole, the first end face may be the inner circumferential surface of the first electrode in the through hole, and the second end face may be the outer circumferential surface of the second electrode.

[0008] With this liquid sensor, the edge effect can be obtained relatively easily by adjusting the length of each portion of the inner surface of the first electrode and the outer surface of the second electrode in the through hole, as well as the distance between the inner surface of the first electrode and the outer surface of the second electrode in the through hole.

[0009] In the liquid sensor described above, the first electrode may have a first through-hole and a second through-hole, the second electrode may include a first conductor and a second conductor, the first conductor and the second conductor may be arranged in the first through-hole and the second through-hole, the first end face may include the inner circumferential surface of the first electrode in the first through-hole and the inner circumferential surface of the first electrode in the second through-hole, and the second end face may include the outer circumferential surface of the first conductor and the outer circumferential surface of the second conductor.

[0010] With this liquid sensor, an edge effect can be obtained relatively easily by adjusting the length of each portion of the inner surface of the first electrode in the first through hole, the inner surface of the first electrode in the second through hole, the outer surface of the first conductor, and the outer surface of the second conductor, as well as the distance between the inner surface of the first electrode and the outer surface of the first conductor in the first through hole, and the distance between the inner surface of the first electrode and the outer surface of the second conductor in the second through hole.

[0011] A liquid sensor according to another aspect of the present invention detects the amount of foreign matter in a liquid by immersing at least a portion of it in the liquid. The liquid sensor comprises a first substrate and a second substrate, each including a first electrode and a second electrode. Each of the first and second substrates further comprises a first detection circuit. The first detection circuit detects the capacitance of a capacitor formed between the first and second electrodes. The effect of foreign matter on the capacitance detected by the first substrate is greater than the effect of foreign matter on the capacitance detected by the second substrate. The liquid sensor further comprises a second detection circuit. The second detection circuit detects the amount of foreign matter based on the capacitance detected by the first substrate and the capacitance detected by the second substrate.

[0012] In this liquid sensor, the amount of foreign matter is detected based on the capacitance detected by the first substrate and the capacitance detected by the second substrate. Therefore, with this liquid sensor, the degree to which foreign matter affects the capacitances detected by the first and second substrates differs from that of the first substrate, and the influence of factors other than foreign matter on capacitance is taken into account when detecting the amount of foreign matter, thus enabling more accurate detection of the amount of foreign matter in the liquid.

[0013] In the liquid sensor described above, the first end face of the first electrode and the second end face of the second electrode may face each other with a predetermined distance between them, a capacitor may be formed between the first end face and the second end face, and the respective areas of the first end face and the second end face, as well as the predetermined distance between them, may satisfy the conditions for an edge effect to occur in the capacitor.

[0014] In this liquid sensor, an edge effect occurs in the capacitor formed between the first and second end faces, causing electric field lines to bulge outwards from the end of the capacitor opposite to the substrate. As a result of the edge effect, the density of electric field lines increases near the end of the capacitor opposite to the substrate. Therefore, this liquid sensor can achieve a relatively wide detection range and relatively high detection sensitivity for foreign objects because the electric field lines bulge outwards from the capacitor and the density of electric field lines increases near the end of the capacitor opposite to the substrate.

[0015] In the above liquid sensor, the capacitance of the capacitor may be detected when the first substrate is below the second substrate, with at least a portion of it immersed in the liquid.

[0016] Foreign matter in liquids often accumulates in the lower part of the liquid. With this liquid sensor, when at least a portion of the liquid sensor is immersed in the liquid, the first substrate detects the capacitance of the capacitor below the second substrate. As a result, the second substrate can detect the influence of factors other than foreign matter on the capacitance, and consequently, the amount of foreign matter in the liquid can be detected with higher accuracy. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a liquid sensor that can achieve a relatively wide detection range and relatively high detection sensitivity for foreign matter in a liquid. [Brief explanation of the drawing]

[0018] [Figure 1] This diagram schematically shows the configuration of an oil sensor according to Embodiment 1. [Figure 2] This figure schematically shows the II-II section of Figure 1. [Figure 3] This is a schematic plan view of the circuit board. [Figure 4] This figure schematically shows a portion of the IV-IV section in Figure 3. [Figure 5]It is a perspective view schematically showing a partially enlarged view of a part in FIG. 3. [Figure 6] It is a flowchart showing the manufacturing procedure of a substrate. [Figure 7] It is a diagram for explaining the electric lines of force represented between electrodes in a substrate to be compared. [Figure 8] It is a diagram for explaining the electric lines of force represented between electrodes in a substrate included in the oil sensor according to Embodiment 1. [Figure 9] It is a flowchart showing the procedure for detecting the amount of contaminants mixed in oil. [Figure 10] It is a diagram for explaining the procedure for detecting the capacitance between electrodes. [Figure 11] It is a diagram schematically showing the configuration of an oil sensor according to Embodiment 2. [Figure 12] It is a flowchart showing the procedure for detecting the amount of contaminants mixed in oil in Embodiment 2. [Figure 13] It is a diagram for explaining other examples of the shape of each conductor and other examples of the shape of each through hole. [Figure 14] It is a diagram schematically showing other examples of the configuration of an oil sensor.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments according to one aspect of the present invention (hereinafter also referred to as "the present embodiments") will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. Also, each drawing is schematically drawn with appropriate omissions or exaggerations of the subject for easy understanding.

[0020] [1. Embodiment 1] <1-1. Configuration>

[0021] (1-1-1. Configuration of Oil Sensor) Figure 1 is a schematic diagram showing the configuration of an oil sensor S1 according to this first embodiment. The oil sensor S1 is installed, for example, in an oil tank of a vehicle and is configured to detect the amount of contaminants (hereinafter also referred to as "contaminant amount") mixed in the fuel (oil). Contaminants refer to contaminants and contamination. Examples of contaminants mixed in oil include soil components containing alumina and silica, iron, moisture, air bubbles, and sludge. The oil sensor S1 is configured to detect the amount of contaminants in the oil when at least a portion of it is immersed in the oil.

[0022] As shown in Figure 1, the oil sensor S1 includes an oil sensor body 10, a detection circuit 20, and a cable 30. In the oil sensor body 10, a circuit board 100 is housed in a plug 15. The circuit board 100 and the detection circuit 20 are electrically connected, for example, through the cable 30. The detection circuit 20 includes, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). Note that the circuit board 100 and the detection circuit 20 do not necessarily need to be connected through the cable 30. For example, the circuit board 100 and the detection circuit 20 may be substantially electrically connected by mounting the circuits mounted on the circuit board 100 and the detection circuit 20 on the same circuit board.

[0023] Figure 2 is a schematic diagram showing the II-II cross-section of Figure 1. As shown in Figure 2, the plug 15 is cylindrical, and the substrate 100 is housed inside the plug 15. Because the plug 15 is cylindrical, oil enters the plug 15 when the oil sensor body 10 is immersed in oil. As will be described in detail later, multiple electrodes are formed on the substrate 100. When the amount of contaminants in the oil changes, the relative permittivity of the oil changes, and as a result, the capacitance between pairs of electrodes contained in the multiple electrodes changes. The detection circuit 20 (see Figure 1) detects the capacitance between pairs of electrodes by using various known techniques. Based on the detected capacitance, the detection circuit 20 detects the amount of contaminants in the oil.

[0024] To achieve high detection accuracy regarding the amount of contaminants in the oil, it is preferable that the capacitance between the pair of electrodes changes more significantly in response to the change in the relative permittivity of the oil. Therefore, it is preferable to achieve a wide detection range and high detection sensitivity for contaminants in the oil. In the oil sensor S1 according to this embodiment 1, a wide detection range and high detection sensitivity for contaminants in the oil are achieved by devising the configuration of the substrate 100. Next, the configuration of the substrate 100 will be described in detail.

[0025] (1-1-2. Circuit board configuration) Figure 3 is a schematic plan view of the substrate 100. Figure 4 is a schematic view of a portion of the IV-IV cross-section in Figure 3. Referring to Figures 3 and 4, in a plan view, the shape of the substrate 100 is substantially rectangular with long and short sides. The substrate 100 is a so-called fluororesin substrate. Because fluororesin substrates have excellent weather resistance and chemical resistance, the substrate 100 can withstand use in harsh environments. Note that the substrate 100 does not necessarily have to be made of a fluororesin substrate, but it is preferable to make it of a substrate with excellent chemical resistance, for example.

[0026] The substrate 100 includes a substrate body 105, electrodes 110 and 120. The substrate body 105 is the fluororesin substrate described above and is composed of multiple layers including layers LY1 and LY2. For example, multiple through-holes TH1 are formed in layer LY1, and wiring L1 is formed on layer LY2. Each through-hole TH1 and wiring L1 are electrically connected. Each of the electrodes 110 and 120 is formed on the substrate body 105 and is composed of a conductive material such as gold, silver, copper, or aluminum.

[0027] Electrode 110 has a roughly rectangular shape with a long side and a short side. Electrode 110 has a plurality of through holes (through holes H1, H2, H3, H4, H5, and H6). Each of the through holes H1-H6 has a roughly rectangular shape with a long side and a short side. Electrode 120 contains a plurality of conductors (conductors 121, 122, 123, 124, 125, and 126). Each of the conductors 121-126 has a roughly rectangular shape with a long side and a short side. The size of conductors 121-126 is slightly smaller than the size of the through holes H1-H6. Conductors 121-126 are respectively arranged within the through holes H1-H6. Electrode 110 is connected to one pole of a power supply (not shown), and each of the conductors 121-126 is connected to the other pole of the power supply through a through hole TH1 and wiring L1. This applies a voltage between electrodes 110 and 120.

[0028] Figure 5 is a schematic perspective view that partially enlarges a portion of region A1 in Figure 3. As shown in Figure 5, the end face F1, which is part of the inner circumferential surface of electrode 110 in the through hole H3, and the end face F2, which is part of the outer circumferential surface of conductor 123 (corresponding to one side of conductor 123), face each other with a predetermined distance D1 between them. When a voltage is applied between electrodes 110 and 120, a capacitor C1 is formed between end faces F1 and F2. As will be explained in detail later, the respective areas of end faces F1 and F2 and the predetermined distance D1 satisfy the conditions for an edge effect to occur in capacitor C1. That is, the relationship that the area of ​​end face F2 >> predetermined distance D1 does not hold true. The reason why the respective areas of end faces F1 and F2 and the predetermined distance D1 are designed to produce an edge effect in capacitor C1 will be explained in detail later.

[0029] Referring again to Figure 3, the area of ​​each end face included in the outer surface of conductor 121, and the distance between the inner surface of electrode 110 in through hole H1 and the outer surface of conductor 121, satisfy the conditions for edge effects to occur in each capacitor formed between the opposing end faces. The same applies to the relationship between the outer surface of conductor 122 and the inner surface of electrode 110 in through hole H2, the relationship between the outer surface of conductor 123 and the inner surface of electrode 110 in through hole H3, the relationship between the outer surface of conductor 124 and the inner surface of electrode 110 in through hole H4, the relationship between the outer surface of conductor 125 and the inner surface of electrode 110 in through hole H5, and the relationship between the outer surface of conductor 126 and the inner surface of electrode 110 in through hole H6.

[0030] <1-2. Substrate Manufacturing Method> Figure 6 is a flowchart showing the manufacturing procedure for the substrate 100. Referring to Figure 6, first, a substrate body 105 is prepared in which a layer of conductive material (hereinafter also referred to as the "conductive material layer") is formed on at least one main surface (step S100). Multiple through-holes TH1 and wiring L1 are pre-formed on the substrate body 105. The manufacturing apparatus for the substrate 100 forms slits in the conductive material layer of the prepared substrate body 105 (step S110). The manufacturing apparatus forms slits in the conductive material layer by etching, for example. By forming slits in the conductive material layer, a gap is created between each of the conductors 121-126 and the electrode 110, and each of the conductors 121-126 and the electrode 110 are electrically isolated. This completes the substrate 100.

[0031] <1-3. Achieving a wide detection range and high detection sensitivity> Figure 7 is a diagram illustrating the electric field lines EL1 represented between electrodes 110X and 120X on the comparison substrate 100X. Referring to Figure 7, on substrate 100X, electrodes 110X and 120X face each other. When a voltage is applied between electrodes 110X and 120X, a capacitor is formed between electrodes 110X and 120X.

[0032] The respective areas of electrodes 110X and 120X, and the length between electrodes 110X and 120X, do not satisfy the conditions for edge effects to occur in this capacitor. That is, the relationship holds that the respective areas of electrodes 110X and 120X >> the length between electrodes 110X and 120X. Therefore, the electric field lines EL1 represented between electrodes 110X and 120X point linearly from electrode 110X to electrode 120X. In this case, contamination located between electrodes 110X and 120X is detected, but the detection range of the contamination is not necessarily wide, and the detection sensitivity of the contamination is not necessarily high.

[0033] Figure 8 is a diagram illustrating the electric field lines EL1 represented between electrodes 110 and 120 in the substrate 100 included in the oil sensor S1 according to this embodiment 1. Referring to Figure 8, as described above, the end face F1 of electrode 110 and the end face F2 of conductor 123 (electrode 120) face each other, and when a voltage is applied between electrodes 110 and 120, a capacitor C1 is formed between electrode 110 and conductor 123.

[0034] The area of ​​the end faces F1 and F2 and the predetermined spacing D1 satisfy the conditions for the edge effect to occur in capacitor C1. As a result, electric field lines EL1 bulge outwards from the end of capacitor C1 opposite to the substrate body 105. Furthermore, as a result of the edge effect, the density of electric field lines EL1 is higher near the end of capacitor C1 opposite to the substrate body 105. Contaminants in the oil are more often present in the space outside the space between the electrode 110 and the conductor 123 (slit portion) than in the space between the electrode 110 and the conductor 123. Therefore, with substrate 100, the electric field lines EL1 bulge outwards from capacitor C1, and the density of electric field lines EL1 is higher near the end of capacitor C1 opposite to the substrate body 105, thus enabling a relatively wide detection range and relatively high detection sensitivity for contaminants in the oil.

[0035] <1-4. Operation> Figure 9 is a flowchart showing the procedure for detecting the amount of contaminants mixed into the oil in this embodiment 1. The process shown in this flowchart is performed by the detection circuit 20 at predetermined intervals, for example, while a voltage is applied between electrodes 110 and 120.

[0036] Referring to Figure 9, the detection circuit 20 detects the capacitance of each capacitor formed between electrodes 110 and 120 and calculates the sum of these capacitances to determine the capacitance between electrodes 110 and 120 (step S200).

[0037] Figure 10 is a diagram illustrating the procedure for detecting the capacitance between electrodes 110 and 120. Referring to Figure 10, for example, around conductor 121 included in electrode 120, a capacitor C3 is formed between the end face F3 of conductor 121 and the inner surface of substrate 100, and a capacitor C4 is formed between the end face F4 of conductor 121 and the inner surface of substrate 100. Furthermore, a capacitor C5 is formed between the end face F5 of conductor 121 and the inner surface of substrate 100, and a capacitor C6 is formed between the end face F6 of conductor 121 and the inner surface of substrate 100. The capacitance between electrode 110 and conductor 121 is the sum of the capacitances in capacitors C3, C4, C5, and C6. Similarly, the capacitance between each of conductors 122, 123, 124, 125, and 126 and electrode 110 is calculated. The sum of the capacitances between each of the conductors 121, 122, 123, 124, 125, and 126 and electrode 110 is considered to be the capacitance between electrodes 110 and 120.

[0038] Referring again to Figure 9, when the capacitance between electrodes 110 and 120 is detected, the detection circuit 20 detects the amount of contaminants in the oil based on the capacitance between electrodes 110 and 120 (step S210). The relationship between the capacitance between electrodes 110 and 120 and the amount of contaminants in the oil when immersed in oil has been obtained in advance through experiments, and information showing this relationship (hereinafter also referred to as "first relationship information") is stored in the detection circuit 20. The detection circuit 20 estimates the amount of contaminants in the oil from the capacitance between electrodes 110 and 120 by referring to the first relationship information. The detection circuit 20 notifies the outside of the oil sensor S1 of the information indicating the detected amount of contaminants (hereinafter also referred to as "contaminant amount information") (step S220). The notified amount of contaminants is displayed, for example, on a display outside the oil sensor S1.

[0039] <1-5. Features> As described above, in the oil sensor S1 according to this embodiment 1, an edge effect occurs in the capacitor formed between the end face of electrode 110 and the end face of electrode 120, causing the electric field lines EL1 to bulge outwards from the end of the capacitor opposite to the substrate body 105. As a result of the edge effect, the density of electric field lines EL1 increases near the end of the capacitor opposite to the substrate body 105. Therefore, with the oil sensor S1, since the electric field lines EL1 bulge outwards from the capacitor and the density of electric field lines EL1 increases near the end of the capacitor opposite to the substrate body 105, a relatively wide detection range and relatively high detection sensitivity can be achieved with respect to contamination.

[0040] [2. Embodiment 2] <2-1. Oil Sensor Configuration> Figure 11 is a schematic diagram showing the configuration of the oil sensor S1A according to this second embodiment. The oil sensor S1A is installed, for example, in an oil tank of a vehicle and is configured to detect the amount of contaminants in the fuel (oil). The oil sensor S1A is configured to detect the amount of contaminants in the oil when at least a portion of it is immersed in the oil.

[0041] As shown in Figure 11, the oil sensor S1A includes a substrate 100A1, a substrate 100A2, a substrate 140, and a connector 150. Substrate 100A1 includes a substrate body 105, an electrode pattern EP1, and a detection circuit 130. On substrate 100A1, the electrode pattern EP1 is formed on the substrate body 105 and the detection circuit 130 is mounted thereon. The electrode pattern EP1 has substantially the same configuration as the electrodes 110 and 120 included in the oil sensor S1 according to Embodiment 1 described above. The detection circuit 130 includes, for example, a CPU, RAM, and ROM.

[0042] The substrate 100A2 includes a substrate body 105, an electrode pattern EP2, and a detection circuit 130. In substrate 100A2, the electrode pattern EP2 is formed on the substrate body 105 and the detection circuit 130 is mounted on it. The electrode pattern EP2 has substantially the same configuration as the electrodes 110 and 120 included in the oil sensor S1 according to the above embodiment 1. The positions of the electrode patterns in substrate 100A1 and substrate 100A2 are different when the oil sensor S1A is immersed in oil. That is, when the oil sensor S1A is immersed in oil, the electrode pattern EP1 of substrate 100A1 is located lower than the electrode pattern EP2 of substrate 100A2.

[0043] The circuit board 140 includes a circuit board body 141 and a detection circuit 142. The circuit board body 141 is made of, for example, a fluororesin substrate. In circuit board 140, the detection circuit 142 is mounted on the circuit board body 141. The detection circuit 142 includes, for example, a CPU, RAM, and ROM. The connector 150 electrically connects the circuit boards 100A1, 100A2, and 140 to each other.

[0044] <2-2. Achieving high detection accuracy for the amount of contaminants in oil> The dielectric constant of oil can also change due to factors other than contaminants in the oil (for example, the degree of oil degradation or the oil temperature). Therefore, in order to detect the amount of contaminants in the oil with higher accuracy, it is preferable to isolate the changes caused by contaminants from the overall change in the dielectric constant of the oil.

[0045] Contaminants in oil tend to accumulate in the lower part of the oil. In the oil sensor S1A according to this second embodiment, substrate 100A1 detects the capacitance of the capacitor formed in the lower electrode pattern EP1, and substrate 100A2 detects the capacitance of the capacitor formed in the upper electrode pattern EP2. Considering that contaminants mainly accumulate in the lower part of the oil, the capacitance detected by substrate 100A1 is greatly affected by both the change in the relative permittivity of the oil due to contaminants and the change in the relative permittivity of the oil due to factors other than contaminants. On the other hand, the capacitance detected by substrate 100A2 is mainly affected by the change in the relative permittivity of the oil due to factors other than contaminants.

[0046] In this second embodiment, the amount of contaminants in the oil is detected based on both the capacitance detected by substrate 100A1 and the capacitance detected by substrate 100A2. Therefore, the oil sensor S1A takes into account the influence of factors other than contaminants on capacitance when detecting the amount of contaminants, thus enabling more accurate detection of the amount of contaminants in the oil.

[0047] <2-3. Operation> Figure 12 is a flowchart showing the procedure for detecting the amount of contaminants mixed into the oil in this second embodiment. The process shown in this flowchart is performed at predetermined intervals by detection circuits 130 and 142, for example, when a voltage is applied between the electrodes included in electrode patterns EP1 and EP2, respectively.

[0048] Referring to Figure 12, the detection circuit 130 included in substrate 100A1 detects the capacitance between electrodes in electrode pattern EP1 and transmits a signal indicating the detected capacitance to the detection circuit 142 (step S300). The detection circuit 130 included in substrate 100A2 detects the capacitance between electrodes in electrode pattern EP2 and transmits a signal indicating the detected capacitance to the detection circuit 142 (step S310). The detection circuit 142 calculates the difference between the capacitance detected in substrate 100A1 and the capacitance detected in substrate 100A2 (step S320).

[0049] The detection circuit 142 estimates the amount of contaminants in the oil based on the calculated difference (step S330). The relationship between the capacitance difference and the amount of contaminants in the oil has been obtained in advance through experiments, and information showing this relationship (hereinafter also referred to as "second relationship information") is stored in the detection circuit 20. The detection circuit 20 estimates the amount of contaminants in the oil from the calculated capacitance difference by referring to the second relationship information. The detection circuit 20 notifies the outside of the oil sensor S1A of the information indicating the estimated amount of contaminants (step S340). The notified information is displayed, for example, on a display outside the oil sensor S1A. In addition, if the estimated amount of contaminants exceeds a predetermined amount, an alert may be displayed on the display.

[0050] <2-4. Features> As described above, in the oil sensor S1A according to this second embodiment, the amount of contamination is detected based on the capacitance detected by substrate 100A1 and the capacitance detected by substrate 100A2. Therefore, with the oil sensor S1A, the amount of contamination is estimated by taking into account the influence of factors other than contamination on capacitance, so the amount of contamination in the oil can be detected with higher accuracy.

[0051] [3. Other Embodiments] The concept of the above embodiments is not limited to those described above. Examples of other embodiments to which the concept of the above embodiments can be applied will be described below.

[0052] <3-1> In the above embodiment 1, the shapes of electrodes 110 and 120 are not limited to the shapes described above. For example, the shape of each conductor included in electrode 120 does not have to be substantially rectangular, and the shape of each through hole formed in electrode 110 does not have to be substantially rectangular.

[0053] Figure 13 illustrates other examples of the shapes of each conductor and each through-hole. Referring to Figure 13, a through-hole H1A is formed in electrode 110A. Conductor 121A is placed inside through-hole H1A. Multiple irregularities are formed on the outer circumference of both through-hole H1A and conductor 121A. As a result, when applied between electrode 110A and conductor 121A, the number of capacitors formed between electrode 110A and conductor 121A is increased compared to when the shapes of the electrode and conductor are approximately rectangular. Consequently, the sensitivity for detecting the amount of contamination is increased.

[0054] <3-2> In the above embodiment 2, the height position of electrode pattern EP1 and the height position of electrode pattern EP2 were different from each other, and as a result, the degree of influence of contamination on each capacitance detected by substrate 100A1 and substrate 100A2 was different from each other. However, the factors that cause the degree of influence of contamination on each capacitance detected by substrate 100A1 and substrate 100A2 to be different from each other are not limited to the height position of the electrode patterns.

[0055] Figure 14 is a schematic diagram showing another example of the configuration of an oil sensor. Referring to Figure 14, the oil sensor S1B includes a substrate 100B1, a substrate 100B2, and a substrate 140. The height position of the electrode pattern EP1 on substrate 100B1 is the same as the height position of the electrode pattern EP2 on substrate 100B2. On substrate 100B2, the upper part of the electrode pattern EP2 is covered by a concave enclosure 160. The enclosure 160 does not prevent the ingress of oil, but it does prevent the ingress of contaminants. As a result, the capacitance detected by substrate 100B1 is greatly affected by both the change in the relative permittivity of the oil due to contaminants and the change in the relative permittivity of the oil due to factors other than contaminants. On the other hand, the capacitance detected by substrate 100B2 is mainly affected by the change in the relative permittivity of the oil due to factors other than contaminants. The configuration of the oil sensor according to the above embodiment 2 may be as shown in Figure 14.

[0056] <3-3> In the above embodiments 1 and 2, the amount of contaminants in the oil was detected, but the amount of foreign matter other than contaminants in liquids other than oil may also be detected, or the amount of foreign matter other than contaminants in the oil may also be detected, or the amount of contaminants in liquids other than oil may also be detected.

[0057] <3-4> In the above embodiments 1 and 2, the detection of the amount of contamination may be performed based on the capacitance between the electrodes. For example, the amount of contamination may be directly estimated from the capacitance between the electrodes, or the relative permittivity of the oil may be calculated from the capacitance between the electrodes, and the amount of contamination may be estimated from the relative permittivity of the oil.

[0058] Embodiments of the present invention have been described illustratively above. That is, a detailed description and accompanying drawings have been disclosed for illustrative purposes. Therefore, some of the components described in the detailed description and accompanying drawings may not be essential for solving the problem. Consequently, the mere fact that these non-essential components are described in the detailed description and accompanying drawings does not mean that they should be immediately assumed to be essential.

[0059] Furthermore, the above embodiments are merely illustrative in every respect of the present invention. The above embodiments can be improved or modified in various ways within the scope of the present invention. For example, at least a part of the configuration of one embodiment may be combined with at least a part of the configuration of any other embodiment. In other words, in carrying out the present invention, specific configurations can be appropriately adopted depending on the embodiment. [Explanation of Symbols]

[0060] 10 Oil sensor body, 15 Plug, 20 Detection circuit 130, 142 Detection circuit, 30 Cable, 100, 140 Circuit board, 105, 141 Circuit board body, 110, 120 Electrodes, 121, 122, 123, 124, 125, 126 Conductors, 150 Connector, 160 Enclosure, A1 Area, EP1, C1, C3, C4, C5, C6 Capacitors, D1 Predetermined spacing, EL1 Electric field lines, EP1, EP2 Electrode patterns, F1, F2, F3, F4, F5, F6 End faces, H1, H2, H3, H4, H5, H6 Through holes, L1 Wiring, LY1, LY2 Layers, S1 Oil sensor, TH1 Through hole.

Claims

1. A liquid sensor that detects the amount of foreign matter in a liquid by immersing at least a portion of it in the liquid, The substrate includes a first electrode and a second electrode, The first end face of the first electrode and the second end face of the second electrode face each other with a predetermined distance between them. A capacitor is formed between the first end face and the second end face. The area of ​​the first end face and the second end face, and the predetermined distance, satisfy the conditions for an edge effect to occur in the capacitor. A liquid sensor further comprising a detection circuit that detects the amount of foreign matter based on the capacitance of the capacitor.

2. The first electrode has a through hole formed in it. The second electrode is placed inside the through hole, The first end face is the inner circumferential surface of the first electrode in the through hole, The liquid sensor according to claim 1, wherein the second end face is the outer circumferential surface of the second electrode.

3. The first electrode has a first through hole and a second through hole formed therein. The second electrode includes a first conductor and a second conductor, The first conductor and the second conductor are respectively placed in the first through-hole and the second through-hole. The first end face includes the inner circumferential surface of the first electrode in the first through hole and the inner circumferential surface of the first electrode in the second through hole. The liquid sensor according to claim 1, wherein the second end face includes the outer circumferential surface of the first conductor and the outer circumferential surface of the second conductor.

4. A liquid sensor that detects the amount of foreign matter in a liquid by immersing at least a portion of it in the liquid, Each comprises a first substrate and a second substrate, each including a first electrode and a second electrode, Each of the first substrate and the second substrate further includes a first detection circuit for detecting the capacitance of a capacitor formed between the first electrode and the second electrode, The effect of the foreign matter on the capacitance detected by the first substrate is greater than the effect of the foreign matter on the capacitance detected by the second substrate. A liquid sensor further comprising a second detection circuit that detects the amount of foreign matter based on the capacitance detected by the first substrate and the capacitance detected by the second substrate.

5. The first end face of the first electrode and the second end face of the second electrode face each other with a predetermined distance between them. The capacitor is formed between the first end face and the second end face. The liquid sensor according to claim 4, wherein the area of ​​the first end face and the second end face, and the predetermined interval, satisfy the conditions for an edge effect to occur in the capacitor.

6. The liquid sensor according to claim 5, wherein the first substrate detects the capacitance of the capacitor below the second substrate while at least a portion of it is immersed in the liquid.

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