JP4995598B2 - Liquid state detection sensor - Google Patents

Description

  The present invention relates to a liquid state detection sensor that detects a liquid state, and more particularly, to a liquid state detection sensor that includes a liquid concentration detection element that detects the concentration of a specific component in a liquid.

  In recent years, a NOx selective reduction catalyst (SCR) may be used in an exhaust gas purification device that reduces and renders harmless nitrogen oxide (NOx) discharged from a diesel engine, for example, an automobile equipped with a diesel engine. In this device, an aqueous urea solution is used as a reducing agent. However, in order to effectively reduce nitrogen oxides in this device, the aqueous urea solution must be in an appropriate concentration range (the range of urea liquidity in the aqueous urea solution). is required.

  However, even when a urea aqueous solution having an appropriate concentration is stored in the urea aqueous tank that stores the urea aqueous solution, the urea concentration may deviate from the appropriate range due to a change over time or the like. Moreover, liquids other than urea aqueous solution of appropriate urea concentration, such as tap water, may be injected into the urea water tank.

Therefore, a concentration sensor that detects the urea concentration of the urea aqueous solution is attached to the urea water tank, and when the urea concentration of the urea aqueous solution deviates from the appropriate range, a warning or the like is issued when there is an abnormality, and nitrogen oxides are reduced in the exhaust gas purification device. Systems have been proposed that inform the driver that (purification) cannot be performed properly (see Patent Documents 1 and 2).
JP 2000-371831 A WO 2007/004543 A1 publication

  By the way, a liquid state detection sensor that detects the concentration of a specific component in a liquid and that detects the concentration by submerging a liquid concentration detection element forming the detection means in the liquid is as follows. There is a problem to be solved. This is because when detecting the concentration of a specific component such as urea in a liquid such as an aqueous urea solution using such a liquid concentration detection element (hereinafter also referred to simply as an element), a large number of bubbles contained in the liquid, The bubble (group) may interfere with the measurement. This is because when bubbles are attached to the liquid concentration detecting element to measure the concentration of a specific component in the liquid, the influence of the bubbles is superimposed on detecting the concentration of the liquid. Because.

  On the other hand, around the portion of the liquid concentration detecting element that is arranged in the liquid, there is a through-hole (through hole) that allows the liquid to flow or go in and out for the purpose of controlling the flow of the liquid or protecting the element. An element protection cover (protector) may be provided. In addition to such an element protective cover, the liquid that enters the cover through the penetration portion is prevented from directly colliding with the element, or from the configuration or structure of the liquid state detection sensor. In some cases, it may be desired to have a structure in which an outer surrounding member made of a cylindrical member or an annular member is disposed with a support member interposed outside (periphery) of the density detection element or an element protective cover surrounding the element. Further, as in Patent Document 2, the liquid state detection sensor has a cylindrical outer cylinder electrode made of a conductor, and an inner electrode made of a conductor provided along the axial direction in the outer cylinder electrode. And a level (liquid level) detecting unit formed by forming a capacitor whose capacitance changes according to the level of the liquid between the electrodes, and the element is attached to the tip of the internal electrode. In order to further protect the element from the liquid flow, the tip of the outer cylinder electrode is extended to form an outer surrounding portion that plays the same role as the outer surrounding member. The element may be surrounded.

  However, in the case where the outer surrounding member or the outer surrounding portion (hereinafter also referred to as the outer surrounding portion) is provided in this way, bubbles that enter or are contained in the liquid in the space (region) surrounded by the outer surrounding portion. Or a bubble group (henceforth only a bubble) may stay. As described above, the bubbles that have entered the outer enclosure portion may enter the inside of the element protection cover through the penetrating portion of the device protection cover as the liquid flows or shakes. In that case, the bubble that has entered encloses the periphery of the liquid concentration detecting element, resulting in erroneous detection of the concentration. As described above, when the outer surrounding portion is disposed, there is a problem that bubbles are likely to stay inside due to the presence of the outer surrounding portion, and as a result, the density detection may be adversely affected.

  As a countermeasure against such bubbles, it is proposed to provide a bubble discharge path by providing a through portion on the wall surface of the outer surrounding member or the outer surrounding portion itself. In this way, since the bubbles can be discharged (or guided) from the penetrating portion to the outside of the outer surrounding portion, it is possible to prevent the bubbles from coming into contact with the element regardless of the presence or absence of the element protective cover. However, providing such a penetrating portion is not originally preferable for the purpose of providing the outer surrounding portion. Moreover, even if a through-hole is simply provided, smooth discharge of bubbles is not easy, and sweeping out is not achieved.

  The present invention has been made in view of such problems, and in a liquid state detection sensor including a liquid concentration detection element that detects the concentration of a specific component in a liquid, it is possible to reduce adverse effects on concentration detection caused by bubbles. The purpose is to do so.

The present invention according to claim 1 is a cylindrical outer cylinder electrode made of a conductor;
It has an internal electrode made of a conductor provided along the axial direction in the outer cylinder electrode,
It has a level detector formed by forming a capacitor whose capacitance changes according to the level of the liquid between the two electrodes,
Furthermore, a holder member attached to the tip of the internal electrode;
A liquid concentration detection element for detecting the concentration of a specific component in the liquid, which is held by the holder member in a state where the tip of the holder member protrudes from the lower end of the holder member;
A cylindrical or annular support member that is externally fitted to the outer peripheral surface of the holder member so that its downward surface does not become lower than the lower end of the holder member, and is internally fitted to the outer cylindrical electrode. A liquid state detection sensor comprising:
The outer cylindrical electrode has an outer surrounding portion that extends below the downward surface of the support member and forms a space on the outside and the inside of the tip of the element,
One or a plurality of bubble exhaust penetrating portions that communicate with the inside and outside are formed on the side wall of the outer surrounding portion, and when the element is submerged in the liquid with its tip portion downward, Bubbles that have penetrated into the liquid in the space inside are configured to pass through the through portion and be discharged to the outside of the outer enclosure portion,
Moreover, a notch portion is formed in a portion corresponding to the penetrating portion in the circumferential direction of the outer surrounding portion of the intersecting ridge portion formed by the downward surface and the outer peripheral surface of the support member, or in the circumferential direction. A chamfer is formed along
At least a part of the penetrating portion is disposed within a height range of the notch portion or the chamfered portion.

According to the second aspect of the present invention, the downward surface of the support member may be a flat surface as a whole, an upward inclined surface that becomes higher as it goes from the inside toward the outer peripheral edge, or at least a portion near the outer peripheral edge. The liquid state detection sensor according to claim 1, wherein the liquid state detection sensor is formed on an upward inclined surface that becomes higher as it goes toward the periphery. According to a third aspect of the present invention, in the liquid state detection sensor according to the first aspect, the notch or the chamfered portion of the support member is formed in an inclined chamfered shape. .

According to a fourth aspect of the present invention, there is provided a positioning member having a positioning plate portion for positioning the support member on the downward surface thereof on the downward surface side of the support member and inside the outer cylindrical electrode. And
The positioning plate portion includes a notch portion through which bubbles can pass in a portion corresponding to the penetrating portion in the circumferential direction formed in the outer surrounding portion of the outer peripheral edge or a portion near the outer peripheral edge. It is a liquid state detection sensor of any one of Claims 1-3 characterized by the above-mentioned.

The present invention according to claim 5 is a liquid concentration detecting element for detecting the concentration of a specific component in the liquid;
A holder member configured to hold the element in a state where a tip portion located at the lower end of the element is protruded from the lower end of the element;
A cylindrical or annular support member that is externally fitted to the outer peripheral surface of the holder member so that its downward surface does not become lower than the lower end of the holder member;
It is formed in a cylindrical or annular shape that is externally fitted to the outer peripheral surface of the support member so that a space is formed below the downward surface of the support member and outside the tip of the element and inside the element. A liquid state detection sensor comprising:
One or a plurality of penetrating portions leading to the inside and the outside are formed on the side wall of the outer surrounding member, and the space inside the outer surrounding member when the element is submerged in the liquid with its tip portion downward. Air bubbles that have entered into the liquid inside is configured to pass through the penetrating portion and be discharged to the outside of the outer surrounding member,
Moreover, a notch portion is formed in a portion corresponding to the penetrating portion in the circumferential direction of the outer surrounding member among the intersecting ridge portions formed by the downward surface and the outer peripheral surface of the support member, or in the circumferential direction. A chamfer is formed along
At least a part of the penetrating portion is disposed within a height range of the notch portion or the chamfered portion.

According to a sixth aspect of the present invention, the downward surface of the support member is a flat surface as a whole, an upward inclined surface that becomes higher as it goes from the inner side toward the outer peripheral edge, or at least a portion near the outer peripheral edge from the outside. The liquid state detection sensor according to claim 5, wherein the liquid state detection sensor is formed on an upward inclined surface that becomes higher as it goes toward the periphery. The present invention according to claim 7 is the liquid state detection sensor according to claim 5, wherein the notch portion or the chamfered portion of the support member is formed in an inclined chamfered shape. .

  The operation or effect of the present invention will be described with reference to FIGS. 2 to 4. In the liquid state detection sensor of the present invention, a notch (or chamfer) 80 k in the rubber-like elastic member 80 that is a support member; The positional relationship between the outer surrounding portion (hereinafter also referred to as the outer surrounding member or the outer surrounding portion) 11b and the through portion 18 is such that at least a part of the through portion 18 is within the range of the height H at the notch 80k. It is provided to do. For this reason, even if the bubble W in the liquid enters the space inside the outer surrounding portion 11b (hereinafter also referred to as the surrounding space) in the process of using the present liquid state detection sensor, the bubble W remains in the outer surrounding member 11b. In the process of entering the liquid and rising in the liquid, the rubber-like elastic member 80 hits the downward surface 80a (or the positioning plate portion 152) and reaches the outer peripheral edge of the downward surface, and is guided by the notch 80k to be surrounded by the outer side. It can be discharged to the outside through the penetrating part 18 formed in the side wall of the part 11b. That is, in the liquid state detection sensor of the present invention, even if the bubble W in the liquid enters the enclosed space, it is formed on the outer periphery of the downward surface 80a of the rubber-like elastic member 80 located above the inside. Since the gas is guided to the notch 80k and discharged to the outside of the outer surrounding portion 11b using the penetrating portion 18 as a passage of bubbles, the bubbles W are prevented from staying in the surrounding space. As described above, according to the liquid state detection sensor of the present invention, bubbles that have entered the outer surrounding portion 11 b are prevented from adhering to the tip of the liquid concentration detection element 110. This is effective in preventing the occurrence of troubles in detecting the concentration of the specific component in the liquid. In addition, although the thing which consists of a rubber-like elastic member was shown as a supporting member here, it cannot be overemphasized that the material of a supporting member is not limited to this.

  In the present invention, it suffices that at least a part of the penetrating part is provided so as to exist within the height range of the notch part (or the chamfered part). In this case, it is preferable that the upper end edge of the penetrating portion is positioned above the upper end edge of the cutout portion (or the chamfered portion) from the viewpoint of bubble discharge performance. Furthermore, in addition to this positional relationship, it is preferable that the lower end edge of the penetrating portion is positioned below the lower end edge of the notch (or the chamfered portion). However, the lower the lower end edge of the penetrating part is, the more the original purpose of the outer surrounding part surrounding the element is impaired. Furthermore, it is preferable to set the shape and dimensions.

  The downward surface of the support member is a flat surface (horizontal plane) as a whole as described in claim 2 or claim 6, or an upward inclined surface that becomes higher as it goes from the inside toward the outer periphery, or When at least a portion near the outer peripheral edge is formed on the upward inclined surface that becomes higher as it goes from the inner side to the outer peripheral edge, the bubbles are smoothly guided to the outer side. By forming such an inclined surface, the downward surface has a tapered shape such as a conical shape or a truncated cone shape.

  In the present invention, the cutout portion or the chamfered portion of the support member is formed in an inclined chamfered shape as described in claim 3 or claim 7 in terms of bubble discharge performance. However, it may be formed in a circular chamfered shape. However, the shape of the notched portion or the chamfered portion of the support member of the present invention is not limited, for example, may have a stepped shape in the longitudinal section as shown in FIG.

  Furthermore, the liquid concentration detection element of the present invention may be a sensor that detects at least the concentration of a specific component in the liquid. However, in addition to this concentration, the temperature of the liquid, the presence / absence of the liquid (which detects whether the liquid level falls below the lower limit level), the type of liquid, or a combination of these may be detected. . The sensor described in claims 1 to 4 is a sensor including a level detection unit having both inner and outer electrodes, and can detect the liquid level, but is described in claims 5 to 7. The sensor is a sensor that does not include such a level detection unit.

  In the following, the best mode for carrying out the present invention will be described with reference to FIGS. 1 to 11. The liquid state detection sensor 100 according to the present embodiment is a nitrogen oxidation contained in exhaust gas of a diesel vehicle. In addition to a concentration detection unit composed of a urea concentration detection element or the like contained in a urea aqueous solution used for reduction of substances (NOx), a urea aqueous solution level (liquid level) detection unit (level detection unit) is provided. Is. That is, as shown in FIGS. 1 and 2, a liquid state detection sensor (hereinafter also simply referred to as a sensor) 100 includes an outer cylinder electrode 10 having a cylindrical shape, and an outer cylinder electrode inside the outer cylinder electrode 10. 10 includes a level detection unit 70 constituted by a cylindrical internal electrode 20 provided along the direction of the axis O, and a concentration detection unit 30 provided on the lower end side (the lower end side in FIGS. 1 and 2) of the internal electrode 20. The main body is configured as described in detail below.

  First, the level detection unit 70 will be described. The outer cylindrical electrode 10 forming the level detection unit 70 is made of a metal material (conductor) and has a long and thin cylindrical shape extending in the direction of the axis O. A plurality of narrow slits 15 are intermittently opened along each bus bar on, for example, three bus bars (not shown) that are equally spaced in the circumferential direction on the outer periphery of the outer cylindrical electrode 10. . Further, in the portion 11 near the lower end of the outer cylinder electrode 10, the rubber-like elastic member 80 as a support member interposed between the inner electrode 20 described later is prevented from coming off on each bus bar where the slit 15 is formed. Three openings (circular holes) 16 are provided in the same size and at the same height. Further, one air vent hole 19 is formed on one bus bar among the bus bars on which the slits 15 are formed at a position close to the base end portion (the upper end in the drawing) 12 of the outer cylinder electrode 10.

  Further, the lower end portion 11 of the outer cylinder electrode 10 is extended so as to surround a front end portion (lower end portion) 110b of a liquid concentration detecting element (ceramic heater) 110 constituting a concentration detecting portion 30 described later. In the example, the element protection cover 130 that covers and protects the tip 110b of the element 110 is provided with an outer surrounding portion 11b that surrounds and surrounds the space. This outer surrounding portion 11b is extended (extended) beyond the lower end of the element protection cover 130 in the example in the axis O direction (lower end side in the figure) on the lower end side from the position of the opening 16. The outer surrounding portion 11b is formed of a cylindrical member that forms the outer cylindrical electrode 10, and its lower end 10a is opened. Of the outer surrounding portion 11b, the side wall at the intermediate position in the circumferential direction of the three openings (circular holes) 16 for preventing the slipping will be described in detail later, but when the outer surrounding portion 11b is submerged. In addition, three through portions (circular holes) 18 through which bubbles can pass are provided inside and outside of the outer surrounding portion 11b, each having the same size and the same height. However, this height position is set to be positioned below the opening 16. Although details will be described later, as shown in FIGS. 3 and 4, the penetrating portion (circular hole) 18 has a lower end edge 18a that substantially coincides with the downward surface 80a of the rubber-like elastic member 80 in this embodiment. Set to position.

  On the other hand, the outer cylinder electrode 10 has an outer periphery of a cylindrical (cylindrical) electrode support portion 41 in which a base end portion 12 which is an upper end in the drawing protrudes downward to a lower center of a metal attachment portion (attachment member) 40. Are welded in a state of being fitted (engaged). The mounting portion 40 functions as a mounting flange for fixing the sensor 100 to a urea water tank (not shown), and a mounting hole (not shown) for inserting a mounting bolt is formed in the flange portion 42. Yes. Further, a relay provided to make electrical connection between the sensor 100 and an external circuit (not shown) on the opposite side (the upper side in the figure) of the electrode support part 41 with the flange part 42 of the attachment part 40 interposed therebetween. An accommodating portion 43 for accommodating the circuit board 60 for use is erected.

  The circuit board 60 is placed on a board placement part (not shown) protruding from the four corners of the inner wall surface of the housing part 43. The accommodating portion 43 is covered and protected by a cover 45, and the cover 45 is fixed to the flange portion 42. In addition, a connector 62 is fixed to the side surface of the cover 45, and a connection terminal (not shown) of the connector 62 and an electrode terminal on the circuit board 60 are connected by a wiring cable 61. The circuit board 60 and an external circuit (not shown) are connected.

  Further, the inner peripheral surface (hole) 46 of the electrode support portion 41 in the attachment portion 40 is opened in the accommodating portion 43, and the base end portion 22 of the internal electrode 20 is inserted into the hole 46. The internal electrode 20 of the present embodiment is made of a long and thin cylindrical metal material extending in the direction of the axis O. An insulating coating 23 made of a fluorine resin such as PTFE, PFA, ETFE, an epoxy resin, a polyimide resin, or the like is formed on the outer peripheral surface of the internal electrode 20. As will be described later, a level detector 70 is formed between the internal electrode 20 and the outer cylinder electrode 10 by forming a capacitor whose capacitance changes according to the level of the urea aqueous solution.

  A flange-shaped pipe guide 55 for fixing the internal electrode 20 to the mounting portion 40 is fixed to the outer periphery of the base end portion 22 on the upper end side of the internal electrode 20 in the direction of the axis O. 41 is disposed inside a cylindrical inner case 50 disposed in the hole 46, and is engaged in a suspended manner via a pipe guide 55. That is, the pipe guide 55 is an annular guide member (hanging portion) joined to the end edge of the base end portion 22 of the internal electrode 20. On the other hand, the inner case 50 is a flanged cylindrical resin member that positions and supports the internal electrode 20 so that the internal electrode 20 and the outer cylindrical electrode 10 are reliably insulated, and the lower end side is an electrode support portion of the mounting portion 40. 41 is inserted into the hole 46. A flange 51 protruding outward in the radial direction is formed at the upper end of the inner case 50, and when the inner case 50 is engaged with the electrode support part 41, The inner case 50 is prevented from passing through the hole 46 by being inserted into the hole 46 of the electrode support portion 41 and the flange portion 51 coming into contact with the bottom surface in the accommodating portion 43. The internal electrode 20 is inserted into the inner case 50 from the accommodating portion 43 side, and the pipe guide 55 is brought into contact with the upper surface of the flange portion 51, so that the internal electrode 20 is prevented from falling off.

  Further, an O-ring 53 and an O-ring 54 are provided on the outer periphery and the inner periphery of the inner case 50, respectively, and a gap between the outer periphery and the hole 46 of the mounting portion 40, and the inner periphery A gap between the base electrode 22 and the outer periphery of the internal electrode 20 is sealed. Thereby, when the sensor 100 is attached to the top plate or upper lid of the urea water tank (not shown), the inside and the outside of the urea water tank are prevented from communicating with each other via the housing portion 43. Sex is maintained. A plate-like seal member (not shown) is attached to the lower surface (bottom surface of FIG. 1) of the flange portion 42 of the attachment portion 40, and when the sensor 100 is attached to the urea water tank, Watertightness and airtightness with the urea water tank are maintained.

  In addition, as shown in FIG. 1, the pipe guide 55 is pressed against the flange 51 of the inner case 50 by the two pressing plates 56 and 57 as shown in FIG. It depends on. However, the presser plate 56 is fixed in the accommodating portion 43 by tightening with the screw 58 in a state where the presser plate 57 having an insulating property is sandwiched between the presser guide 55 and the pipe guide 55 is pressed. Thereby, the internal electrode 20 is fixed to the electrode support portion 41. A hole 59 is opened in the center of the holding plates 56 and 57 used for fixing, and an electrical connection between the electrode lead wire 52 of the internal electrode 20 and a liquid concentration detecting element 110 described later is performed 2. A two-core cable 91 containing one lead wire 90 (only one lead wire 90 is shown in FIG. 1) is inserted and electrically connected to the pattern on the circuit board 60, respectively. . An electrode (not shown) on the ground side of the circuit board 60 is connected to the mounting portion 40, whereby the outer cylinder electrode 10 welded to the mounting portion 40 is electrically connected to the ground side.

  Now, the concentration detector 30 will be described. The concentration detector 30 is provided at the lower end 21 of the internal electrode 20 (see FIGS. 1 and 2). Specifically, it is as follows. In this example, the concentration detection unit 30 has a liquid concentration detection element (ceramic heater) 110 that detects the concentration of urea in the urea aqueous solution, and a state in which the tip (lower end) 110b of the liquid concentration detection element 110 protrudes. And a holder member 120 made of an insulating resin attached to the lower end portion 21 of the internal electrode 20. However, in this embodiment, the tip portion 110 b of the liquid concentration detection element 110 protruding from the lower end of the holder member 120 is surrounded and protected by the element protection cover 130. Details of the element protection cover 130 will be described later.

  Among these, as shown in FIG. 5, in the liquid concentration detecting element 110, a heater pattern 115 mainly composed of Pt or W is formed on a rectangular plate-like ceramic base 111 made of an insulating ceramic, and a pair of rectangular plates is formed. The heater pattern 115 is embedded in a state of being sandwiched by a ceramic substrate (not shown). Here, the cross-sectional area of the pattern constituting the heating resistor 114 is made smaller than the pattern of the lead portions 112 and 113 serving as both poles for voltage application, so that heat is generated mainly in the heating resistor 114 during energization. To be done. In addition, via conductors or through-hole conductors (not shown) penetrating the surface of the ceramic substrate 111 are provided at both ends of the lead portions 112 and 113, respectively, and the connection with the two lead wires 90 is relayed. Each of the two terminals 119 (only one is shown in FIG. 2) is electrically connected.

  In addition, as shown in FIG. 2 and the like, the holder member 120 made of an insulating resin that supports the liquid concentration detecting element 110 is concentric and includes a large diameter cylindrical portion 122 having a large diameter and a small diameter cylindrical portion 121 having a small diameter. The lower end portion 21 of the internal electrode 20 is inserted inside the large-diameter cylindrical portion 122 to cover the outer periphery thereof. In this embodiment, the holder member 120 is attached to the lower end portion 21 of the internal electrode 20 as described above, and will be described later in detail, but inside the annular rubber elastic member 80 via the holder member 120. The lower end 21 of the internal electrode 20 is elastically supported. Further, the outer peripheral surface of the portion connecting the large-diameter cylindrical portion 122 and the small-diameter cylindrical portion 121 in the holder member 120 is a tapered step portion (tapered portion) 123 that decreases in diameter toward the lower end. Then, on the outer peripheral surface of the small-diameter cylindrical portion 121 that forms a portion closer to the lower end of the holder member 120, four concave portions 124 that are substantially rectangular in front view are formed (recessed) at equal angular intervals in the circumferential direction. Further, a portion near the outer periphery of the lower end (surface) 125 of the small-diameter cylindrical portion 121 of the holder member 120 has a tapered surface that is tapered upward. The downward surface 80 a of the rubber-like elastic member 80 is held at a position that is not lower than the lower end (surface) 125 of the holder member 120.

  On the other hand, the inner peripheral surface of the holder member 120 is formed in a circular cross section that expands in a stepped shape toward the small diameter cylindrical portion 121, the stepped portion 123, and the large diameter cylindrical portion 122. However, the lower end surface 125 of the small diameter cylindrical portion 121 is formed with an opening 126 having a rectangular shape (in the cross section) when viewed from the direction of the axis O so that the tip end portion 110b of the liquid concentration detecting element 110 can protrude without a substantial gap. . The short side and long side of the rectangle in the cross section of the opening 126 are set to correspond to the dimensions of the thickness and width of the liquid concentration detection element 110, respectively. The element 110 has the longitudinal lead portions 112 and 113 (see FIG. 5) side inserted into the small-diameter cylindrical portion 121, and the distal end portion 110 b side in which the heating resistor 114 is embedded is the lower end surface 125 of the holder member 120. In this state, the liquid concentration detecting element 110 is placed in the opening 126 of the holder member 120 by filling and solidifying the adhesive or resin 129 into the inner peripheral surface 127 of the small-diameter cylindrical portion 121. The seal is held and fixed.

  On the other hand, the inner diameter of the large-diameter cylindrical portion 122 is configured to be slightly larger than the outer diameter of the lower end portion 21 of the internal electrode 20, and in this embodiment, two concave grooves 128b are formed in the circumferential direction on the inner peripheral surface 128 thereof. Has been. Thus, such a holder member 120 is attached to the lower end portion 21 of the internal electrode 20 from the large-diameter cylindrical portion 122 side in an outer fitting manner. However, a seal between the inner peripheral surface 128 and the outer peripheral surface of the internal electrode 20 is ensured via the respective seal rings (for example, rubber O-ring packing) 140 loaded in the two concave grooves 128b. The liquid that forms the measurement object is prevented from entering the internal electrode 20 through this space. An annular shelf step portion 128 c is formed on the inner peripheral surface of the step portion 123 of the holder member 120, and the lower end portion 21 of the holder member 120 is attached to the lower end portion 21 of the internal electrode 20. The end surface 21b of this is in contact with the shelf step portion 128c and is positioned in the direction of the axis O. The insulating coating 23 is formed from the lower end portion on the outer peripheral surface of the internal electrode 20 to the position where the O-ring 54 is disposed at the base end portion 22 on the upper end side, and is in a urea water tank (not shown). Even if the level detector 70 is immersed in the urea aqueous solution, the internal electrode 20 is not directly in contact with the urea aqueous solution.

  Before the holder member 120 is attached to the internal electrode 20, the core wires of the two lead wires 90 of the cable 91 are joined to the terminal 119 of the liquid concentration detecting element 110 by caulking or soldering, respectively. In the mounted state, the terminal 119 and the lead wire 90 are covered and protected by the insulating protection member 95 together with the joint portion. Further, the two lead wires 90 are inserted through the cylindrical internal electrode 20 and connected to the circuit board 60.

  Further, in this example, an element protection cover 130 that covers and protects the periphery of the lower end portion of the liquid concentration detection element 110 is attached to the lower end side of the holder member 120 with the upper portion thereof being fitted externally. The element protection cover 130 is made of, for example, a metal plate and has a bottomed cylindrical shape. In addition, on the outer periphery of the body portion 133 of the element protection cover 130, in this embodiment, on the four bus bars that are equally spaced in the circumferential direction, the liquid circulation holes 135 that form the measurement target respectively opened in two circles. Is formed. The bottom portion 132 is formed with a flow hole 136 that is similarly opened at the center thereof. Such an element protection cover 130 is set so that the inner diameter of the body part 133 is the same as or slightly larger than the outer diameter of the small-diameter cylindrical part 121 in the holder member 120 described above. The element protection cover 130 is a base end (upper end) or a portion near the base end of the body portion 133 that is externally fitted to the holder member 120, and is provided at four locations at equal angular intervals in the circumferential direction. Further, a convex portion (tongue-like claw) 137 projecting downward is provided on the inside thereof, and is elastically deformed to fit into the concave portion 124 of the holder member 120 so as to prevent the holder member 120 from coming off, and the axis line. Rotation around O is impossible.

  On the other hand, the rubber-like elastic member 80 is externally fitted to the outer peripheral surface of the holder member 120 so that its downward surface 80a does not become lower than the lower end 125 of the holder member 120. The outer cylinder electrode 10 is fitted into the inner peripheral surface of the portion 11 near the lower end. Thereby, the internal electrode 20 and the outer cylinder electrode 10 have the shape which mutually supports in the downward direction. However, in this embodiment, the rubber-like elastic member 80, as shown in FIGS. 6 and 7, is configured so as to be entirely cylindrical or annular, but the inner peripheral surface thereof is an element protective cover. Out of the outer peripheral surface of the body portion 133 of 130, the portion corresponding to the convex portion 137 and the outer peripheral surface of the large-diameter cylindrical portion 122 of the holder member 120 avoiding the element protection cover 130 are straddled forward and backward in the axis O direction. Thus, a cylindrical shape with different inner diameters is formed so that the body portion 133 and the large-diameter cylindrical portion 122 are attached to the outer peripheral surface in an interference fit. The inner peripheral surface 81 of the cylindrical portion on the lower end side has a small diameter, and the inner peripheral surface 82 of the cylindrical portion on the upper end side has a large diameter. The inner diameter surface 81 of the small diameter is slightly smaller in outer diameter than the outer diameter of the body portion 133 of the element protection cover 130, and the inner diameter surface 82 of the large diameter cylindrical portion is the inner diameter of the holder member 120. The outer diameter of the cylindrical portion 122 is slightly smaller, and both are connected by a tapered inner peripheral surface 83. However, the inner peripheral surface 83 has a slightly convex arc shape before being fitted onto the holder member 120.

  Thus, the inner peripheral surface 81 of the rubber-like elastic member 80 is formed so that the outer peripheral surfaces of the holder member 120 and the element protection cover 130 are fitted in an interference fit. , 82 and a tapered inner peripheral surface 83 connecting the two. However, on the inner peripheral surfaces 82 and 83, at positions corresponding to the three bus bars that are equally spaced in the circumferential direction on the outer peripheral surface 89, the groove portions 84 that continue on the inner peripheral surfaces 82 and 83 are provided. Are respectively provided with grooves (see FIGS. 6 and 7).

  Further, the rubber-like elastic member 80 of the present embodiment is formed on the outer peripheral surface 89 corresponding to the groove portion 84 and on each of the openings 16 of the outer cylindrical electrode 10 on three bus bars that are equally spaced in the circumferential direction. Protrusions 87 are provided which are fitted (engaged) and function to prevent disconnection and rotation. In this embodiment, the protrusion 87 has a substantially circular shape on the front surface, but in a side view, the height increases toward the lower end side (the amount of protrusion increases) and the shape of a saw tooth (or human nose). Presents. A plurality (five in the present embodiment) of groove portions 88 are provided along the axis O direction between the protrusions 87 in the circumferential direction of the outer peripheral surface 89. Thus, the rubber-like elastic member 80 is press-fitted into the outer cylinder electrode 10 from the lower end 10a side, and the element protection cover 130 fitted to the small diameter cylindrical portion 121 of the holder member 120 is inserted into the lower end side cylinder. The protrusions 87 of the outer peripheral surface 89 are fitted into the openings 16 of the outer cylindrical electrode 10 respectively. Thereby, the internal electrode 20 is elastically supported at a portion near the lower end of the outer cylinder electrode 10.

  On the other hand, a minute round chamfer is given along the circumferential direction to the intersecting ridge formed by the downward surface 80a and the outer peripheral surface 89 in such a rubber-like elastic member 80. A cutout portion 80k that is partially cut out is provided at a position that is located in the middle of each protrusion 87 in the circumferential direction. Thereby, in this embodiment, in a state where the rubber-like elastic member 80 is fitted to the lower end portion of the outer cylindrical electrode 10, the notch portion 80k is provided at a portion corresponding to the through portion 18 in the circumferential direction of the outer surrounding portion 11b. Is provided. However, the notch 80k is formed so as to form an inclined chamfered portion with a predetermined width. In the present embodiment, as shown in FIGS. 3 and 4, the lower end edge of the notch 80k (in this embodiment, the same position as the lower end surface 80a) substantially coincides with the lower end edge 18a of the penetrating portion 18, and The upper end edge 80b of the notch 80k is set to have a positional relationship so as to substantially coincide with the upper end edge 18b of the penetrating part 18. Thereby, the flow path is formed inside and outside of the outer surrounding portion 11b via the notch portion 80k and the through portion 18. In the present embodiment, it has been described that the notches 80k are formed at positions corresponding to the three through portions 18, but instead of the notches 80k, the whole of the notches 80k is provided along the circumferential direction. A chamfered portion may be provided, or such a chamfered portion may be provided intermittently so as to correspond to the three through portions 18.

  However, in this embodiment, the rubber-like elastic member 80 attached to the inner side of the outer cylindrical electrode 10 is on the downward surface 80a side and on the inner side of the outer cylindrical electrode 10 (inner side of the outer surrounding portion 11b). As shown in FIG. 2, a positioning member 150 having a positioning plate portion 152 for positioning the rubber-like elastic member 80 on the downward surface 80a side is attached. The positioning member 150 is formed as shown in FIGS. 2, 8, and 9. That is, the positioning member 150 includes a positioning plate portion 152 having a notch portion 153 that is formed by cutting the outer peripheral edge of a circular plate having an annular shape into a straight line parallel to the tangential direction at three equiangular intervals. It has three leg portions 154 that extend substantially at a right angle to the positioning plate portion 152 at the lower end side at a portion of the outer periphery where the notch portion 153 is not provided, and a hook 156 that protrudes outward at the lower end of the leg portion 154. ing. Each hook 156 is provided at the center of the lower end of the leg portion 154, and the hook 156 is engaged with the lower end 10a of the outer surrounding portion 11b of the outer cylinder electrode 10 to perform positioning in the axis O direction. The plate portion 152 supports and positions the downward surface 80a of the rubber-like elastic member 80.

  The positioning member 150 is fixed by welding the leg portion 154 to a portion of the outer cylinder electrode 10 near the lower end 10a of the outer surrounding portion 11b. Further, in this fixing, the notch portion 153 of the positioning member 150 is set at a position corresponding to the circumferential through portion 18 of the outer surrounding portion 11b, and as shown in FIG. 2, the outer surrounding portion 11b The bubble W that has entered inside passes through the cutout portion 153 of the positioning plate portion 152 and the cutout portion 80k of the rubber-like elastic member 80, reaches the penetration portion 18, and is discharged to the outside of the outer enclosure portion 11b. It is configured.

  A circular hole 152 a is provided in the center of the positioning plate portion 152, and the body portion 133 of the element protection cover 130 attached to the lower end portion of the holder member 120 is inserted therethrough. Further, the positioning plate portion 152 has an outer diameter smaller than the inner diameter of the outer cylindrical electrode 10, and the leg portion 154 is set along the inner peripheral surface in the axial direction of the outer cylindrical electrode 10.

  Further, the positioning member 150 of the present embodiment is provided with a bottom plate 157 that horizontally closes the circular hole 152a in a plan view at a position near the lower end of the leg portion 154. However, the bottom plate 157 is provided with mounting pieces 158 that are bent upwardly in a “<” shape at three equiangular intervals on the periphery thereof, and each mounting piece 158 is located near the upper end of each leg 154. It is fixed to the inner surface of the part by welding. The bottom plate 157 serves to prevent the liquid flow from directly hitting the element 110 from the flow hole 136 at the bottom of the element protection cover 130 when the liquid flows upward from the bottom into the outer surrounding portion 11b. Yes. Thus, the positioning member 150 is configured such that after the rubber-like elastic member 80 is attached to the outer cylinder electrode 10, the hook 156 is disposed on the inner side from the lower end 10 a side of the outer cylinder electrode 10, and the hook 156 is disposed at the lower end of the outer cylinder electrode 10. In this state, each leg 154 is fixed to the outer cylinder electrode 10 by resistance welding, for example, thereby supporting the downward surface 80a of the rubber-like elastic member 80.

  In the sensor 100 of the present embodiment having the above-described configuration, the following specific operational effects can be obtained. That is, such a sensor 100 is attached to a tank (not shown), for example, a top plate so that the element 110 is located at the lower end, and is suspended in the liquid (urea aqueous solution) in the tank. Element 110 is submerged. Although details of each detection principle will be described later, the liquid level is detected by changing the capacitance between the electrodes 10 and 20 in accordance with the level of the liquid. Further, the concentration of urea in the liquid is detected based on the difference in thermal conductivity of the liquid. In this concentration detection, bubbles enter the liquid in the space (region) surrounded by the outer surrounding portion 11b, and the flow holes 135, 136 of the element protection cover 130 are accompanied by the liquid flow. If it passes through and enters the inside, the bubble that has entered will surround the periphery of the liquid concentration detecting element 110, resulting in erroneous detection of the concentration.

  However, in the sensor 100 of this embodiment, as shown in FIG. 2, even if the bubbles W in the liquid enter the inside of the outer surrounding portion 11b as described above, the bubbles W are provided on the side wall of the outer surrounding portion 11b. The air bubble can be smoothly discharged to the outside from the bubble-passing through-hole 18. That is, in the sensor 100 of this embodiment, a notch 80 k is provided at the intersection ridge between the downward surface 80 a of the rubber-like elastic member 80 and the outer peripheral surface 89. Further, the notch portion 80k is located at a position corresponding to the notch portion 153 of the positioning plate portion 152 in the positioning member 150 and the through-hole portion 18 for discharging air bubbles of the outer surrounding portion 11b. Moreover, the penetrating portion 18 is provided in a positional relationship that substantially matches the height H of the notch portion 80k as described above (see FIGS. 2 to 4). For this reason, even if the bubble W in the liquid enters the inside (space) of the outer surrounding portion 11b, the bubble W is in the process of rising in the outer surrounding portion 11b, or the downward surface 80a of the rubber-like elastic member 80 or When it hits the positioning plate portion 152 and reaches the outer peripheral edge side thereof, it is guided by the notch portion 153 and the notch portion 80k, and is discharged to the outside through the penetrating portion 18 of the outer surrounding portion 11b. For this reason, since the bubbles W that have entered the outer surrounding portion 11b are prevented from coming into contact with the tip portion 110b of the liquid concentration detecting element 110, it is effective in preventing the occurrence of troubles in detecting the concentration of a specific component in the liquid. It is. In this embodiment, some of the bubbles reach the inner side of the outer cylinder electrode 10 through the flow passage 85 provided in the rubber-like elastic member 80 and are discharged from the slit 15 to the outer side.

  In the above embodiment, a notch 80k is formed in a portion corresponding to the through-hole 18 in the circumferential direction of the outer surrounding portion 11b in the intersecting ridge formed by the downward surface 80a and the outer peripheral surface 89 of the rubber-like elastic member 80. However, in the present invention, as described above, a chamfered portion may be provided in the whole along the circumferential direction of the intersecting ridge portion instead of the partial notch portion 80k. However, the chamfered portion in this case may be provided intermittently in a part or a plurality of portions in the circumferential direction, not in the entire circumferential direction. In addition, what provided the chamfering part in the part along the circumferential direction becomes a notch part.

  The positional relationship on the height H between the notch or chamfered portion of the rubber-like elastic member 80 and the penetrating portion 18 of the outer surrounding portion 11b is exemplified as the upper and lower end edges matching each other in the above example. However, in the present invention, it is sufficient that at least a part of the penetrating portion is provided so as to exist within the height range of the cutout portion or the chamfered portion. Incidentally, when this is schematically represented, typical examples thereof are divided into four cases as shown in FIGS. That is, FIG. 1A shows a case where the entire penetrating portion 18 is within the range of the height H at the notch 80k. FIG. 7B shows a case where the lower end edge 18a of the penetrating portion 18 exists in the range of the height H at the notch portion 80k, and the upper end edge 18b is positioned higher than the upper end edge 80b at the notch portion 80k. is there. FIG. 5C shows a case where the upper end edge 18b of the penetrating portion 18 exists within the range of the height H at the notch 80k, and the lower end edge 18a is positioned lower than the lower end edge at the notch 80k. . And FIG. 4D shows the case where the upper end edge 18b of the penetrating portion 18 is positioned higher than the upper end edge 80b of the notch portion 80k, and the lower end edge 18a is positioned lower than the lower end edge of the notch portion 80k. is there. As described above, it is preferable that the bubble is discharged as shown in FIG. 4D. However, from the viewpoint of preventing the liquid from directly hitting the element 110, FIG. The positional relationship shown is preferable.

  Moreover, in the said form, although the downward surface 80a in the rubber-like elastic member 80 was made into the flat surface except for the notch part 80k, this is an upward inclined surface which becomes higher as it goes to an outer periphery from the inner side (center). Or you may form in the upward inclined surface which becomes a high rank as it goes to an outer periphery from an inner side at least in the site | part near an outer periphery. From the viewpoint of bubble discharge properties, it is preferable to use an upwardly inclined surface that becomes higher as it goes from the inside toward the outer periphery. That is, it is preferable that the downward surface 80a of the rubber-like elastic member 80 has a shape such as a cone or a truncated cone from the viewpoint of bubble discharge. In this case, when the positioning member is provided as in the above embodiment, the positioning plate portion preferably has a shape that follows the downward surface of the rubber-like elastic member 80.

  The flow or movement of the liquid in the sensor when the above-described liquid state detection sensor 100 is used while attached to a urea water tank (not shown) will be described with reference to FIG. As shown in FIG. 2, the outer cylindrical electrode 10 has an outermost B portion at the lower end side in the axis O direction and a C portion at the upper end side from the rubber-like elastic member 80, respectively. The aqueous urea solution flows in through the opening at the lower end and the slit 15. In addition, the urea aqueous solution flows into the part D in the element protection cover 130 from the part B through the liquid circulation holes 135 and 136.

  Next, the principle of detecting the urea aqueous solution level and urea concentration by the above-described liquid state detection sensor 100 will be described. First, the principle of detecting the level of the urea aqueous solution in the level detection unit 70 will be described with reference to FIG. FIG. 11 is an enlarged cross-sectional view of the vicinity of the water surface of the urea aqueous solution filled in the gap between the outer cylinder electrode 10 and the inner electrode 20.

  The liquid state detection sensor 100 is assembled in a urea water tank (not shown) containing an aqueous urea solution in a state where the lower end sides of the outer cylinder electrode 10 and the inner electrode 20 are directed to the bottom wall side. That is, the level detection unit 70 of the liquid state detection sensor 100 sets the displacement direction of the urea aqueous solution (the level of the urea aqueous solution level) in the urea water tank (not shown) as the axis O direction. 10 and the inner electrode 20 are assembled to a urea water tank (not shown) so that the lower end side of the urea aqueous solution is on the side with a low capacity of the urea aqueous solution (low level side). And the electrostatic capacitance between the gaps of the outer cylinder electrode 10 and the inner electrode 20 is measured, and it is detected to what level the urea aqueous solution existing between the two is present in the axis O direction. As is well known, this is based on the fact that the capacitance increases as the difference in diameter between two points having different potentials in the radial direction decreases.

  That is, as shown in FIG. 11, in the portion not filled with the urea aqueous solution, the distance of the portion where the potential difference occurs between the gaps is interposed between the inner peripheral surface of the outer cylindrical electrode 10 and the insulating coating 23. This is the total distance (indicated by distance E) of the distance corresponding to the thickness of the air layer (indicated by distance F) and the distance corresponding to the thickness of the insulating coating 23 (indicated by distance G). On the other hand, in the portion filled with the urea aqueous solution, the potential difference between the gaps is such that the potential of the outer cylinder electrode 10 and the urea aqueous solution is almost equal because the urea aqueous solution exhibits conductivity. The distance G corresponds to a thickness of 23.

  In other words, the capacitance between the gaps in the portion that is not filled with the urea aqueous solution is that the distance between the electrodes is F and the capacitance between the capacitor using air as a dielectric (non-conductor) and the distance between the electrodes is It can be said that this is the combined capacitance of a capacitor in which a capacitor having the insulating coating 23 as a dielectric is connected in series with G. The capacitance between the gaps in the portion filled with the urea aqueous solution can be said to be the capacitance of a capacitor in which the distance between the electrodes is G and the insulating coating 23 is a dielectric. And the electrostatic capacitance of the capacitor | condenser which connected both in parallel will be measured as an electrostatic capacitance of the level detection part 70 whole.

  Here, since the distance F between the electrodes sandwiching the air layer is larger than the distance G between the electrodes sandwiching the insulating coating 23, the capacitance per unit between the electrodes using air as a dielectric is The capacitance per unit between the electrodes using the insulating coating 23 as a dielectric is smaller. For this reason, the change in the capacitance of the portion filled with the urea aqueous solution is larger than the change in the capacitance of the portion not filled with the urea aqueous solution. Is proportional to the level of the aqueous urea solution. In this embodiment, the level detection of the aqueous urea solution is performed by a level detection circuit including a microcomputer mounted on the circuit board 60, and the level information signal obtained by the level detection circuit is sent via the connector 62. It outputs to an external circuit (for example, ECU). The external circuit determines whether or not the level of the urea aqueous solution is appropriate based on the input level information signal, and appropriately performs a process of notifying the driver when it is not appropriate.

  Next, the principle of detecting the concentration of urea as a specific component contained in the urea aqueous solution in the liquid concentration detecting element 110 constituting the liquid property detecting unit 30 will be described. In general, it is known that the thermal conductivity of a liquid varies depending on the concentration of a specific component contained in the liquid. That is, when a heating resistor is used and the surrounding liquid is heated for a certain period of time, the temperature increase rate differs for liquids having different concentrations. It is also known that when a constant current is passed through the heating resistor, the resistance value of the heating resistor increases in proportion to an increase in the temperature around the heating resistor. From this, when a heating resistor is used and the surrounding liquid is heated for a certain period of time, if the degree of change in the resistance value of the heating resistor is found, the degree of temperature change in the surrounding liquid can be found and The concentration of the component can be obtained.

  The liquid state detection sensor 100 according to the present embodiment is configured to flow a constant current through the heating resistor 114, and a detection voltage Vd corresponding to the magnitude of its own resistance value is applied to both ends of the heating resistor 114. appear. When the potential at one end of the heating resistor 114 is Pin and the potential at the other end of the heating resistor 114 is Pout, the detection voltage Vd is obtained by the difference between the potential Pin and the potential Pout. Specifically, first, the detection voltage Vd immediately after the start of energization of the heating resistor 114 is measured, and the detection voltage Vd is measured again after a certain time (for example, after 700 ms). Then, the concentration of the urea aqueous solution is determined using a table (not shown) created in advance by experiments or the like, using the difference value between the two detection voltages Vd as a parameter. In this embodiment, similarly to the level detection of the urea aqueous solution, the concentration detection (calculation) of the urea aqueous solution is performed by the concentration detection circuit including the microcomputer mounted on the circuit board 60, and is obtained by the concentration detection circuit. The obtained concentration information signal is output to an external circuit (for example, ECU) via the connector 62. The external circuit determines whether or not the concentration of the urea aqueous solution is within an appropriate range based on the input concentration information signal, and appropriately performs a process of notifying the driver when it is not within the appropriate range.

  In the above-described embodiment, the heating resistor 114 of the liquid concentration detecting element 110 and the lead portions 112 and 113 are mainly the heating resistor 114 by using the same material and having different pattern cross-sectional areas. Although heat generation is performed, each material may be different.

  Now, a sensor of the present invention different from the above-described sensor will be described with reference to FIG. While the above embodiment is an embodiment of a sensor including the level detection unit 70, the present example does not include such a level detection unit and detects the concentration of a specific component in the liquid. This is a sensor 200 provided with only elements. FIG. 12 is a cross-sectional view of the main part showing an example of this, but this is only different in that the means for forming or configuring the level detection part is removed in relation to FIG. Only the difference will be described, and the same parts are designated by the same reference numerals.

  That is, the sensor 200 removes the outer cylinder electrode 10 and the inner electrode 20 in the above-described form, and instead of the outer surrounding portion 11b extending near the lower end portion of the outer cylinder electrode 10, a cylindrical independent In addition to providing the outer surrounding member 11b, the element 110 is provided in the same manner as described above at the tip of a simple cylindrical member 20 that extends vertically instead of the internal electrode 20. More specifically, in FIG. 2, the outer cylinder electrode 10 is cut at the upper end portion of the rubber-like elastic member 80 to remove the upper portion, and instead of the internal electrode 20, a simple cylindrical member 20 extending vertically is used. Is. Thus, the sensor 200 is submerged in the portion including the liquid concentration detecting element 100 and used for detecting the concentration. In the process of use, the bubble W that has entered the inside of the outer surrounding member 11b In the same manner as in the case of the above-described form, it is smoothly discharged to the outside.

  As described above, the liquid concentration detection element 110 is used to detect the detection of the temperature of the liquid and the lower limit level of the liquid in addition to the detection of the concentration of a specific component (for example, urea) contained in the liquid. Also good. For example, when the temperature of the liquid is detected by the liquid concentration detection element 110, the resistance value of the heating resistor 114 immediately after the constant current starts to flow through the heating resistor 114 (more specifically, the heating value) The temperature of the liquid can be detected based on the magnitude of the detection voltage Vd generated across the resistor 114. Since the resistance value immediately after the heating resistor 114 is energized shows a value corresponding to the temperature of the liquid, the temperature of the liquid can be detected by such a method. In addition, since the change behavior of the resistance value of the heating resistor 114 is greatly different between when the liquid is present around the liquid concentration detecting element 110 and when it is not present, the lower limit level of the liquid is detected using this difference. May be performed.

The longitudinal section front view showing the embodiment of the liquid state detection sensor of the present invention. The enlarged view of the front-end | tip part (lower end part) of the liquid state detection sensor of FIG. The A section enlarged view of FIG. The figure which looked at FIG. 3 from the arrow B. FIG. The schematic diagram which shows the heater pattern of a liquid concentration detection element (ceramic heater). The perspective view of the rubber elastic member as a supporting member used for the sensor of FIG. It is explanatory drawing of the rubber elastic member as a supporting member of FIG. 6, Comprising: A is a front view (side view), B is a top view, C is a center horizontal sectional view of B, D is a bottom view. The perspective view of the positioning member used for the sensor of FIG. It is explanatory drawing of the positioning member of FIG. 8, Comprising: A is a front view (side view), B is a top view, C is the center longitudinal cross-sectional view of B, D is a bottom view. Explanatory drawing which shows the height relationship between a penetration part and the notch part of the rubber elastic member as a supporting member. The expanded sectional view of the water surface vicinity of the urea aqueous solution with which it filled between the gaps of an outer cylinder electrode and an internal electrode. The principal part expanded sectional view of another example of the liquid state detection sensor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Outer cylinder electrode 11b Outer surrounding part or outer surrounding member 18 Bubble-penetrating penetration part 18b Upper part edge 18a of penetration part Lower edge 20 of penetration part Internal electrode 70 Level detection part 80 Rubber elastic member (supporting member)
80a Downward surface 80c of the rubber-like elastic member 80c intersecting ridge 80k formed by the downward surface and the outer peripheral surface of the rubber-like elastic member 89 Notch 89 in the rubber-like elastic member Outer surface 100 of the rubber-like elastic member Liquid state detection sensor 110 Liquid concentration Sensing element 110b Lead end 120 of liquid concentration sensing element Holder member 125 Lower end 150 of holder member Positioning member 152 Positioning plate 153 Notch portion through which air bubbles can pass through positioning plate portion O Axis line H Height at notch portion W Bubble

Claims (7)

A cylindrical outer cylinder electrode made of a conductor;
It has an internal electrode made of a conductor provided along the axial direction in the outer cylinder electrode,
It has a level detector formed by forming a capacitor whose capacitance changes according to the level of the liquid between the two electrodes,
Furthermore, a holder member attached to the tip of the internal electrode;
A liquid concentration detection element for detecting the concentration of a specific component in the liquid, which is held by the holder member in a state where the tip of the holder member protrudes from the lower end of the holder member;
A cylindrical or annular support member that is externally fitted to the outer peripheral surface of the holder member so that its downward surface does not become lower than the lower end of the holder member, and is internally fitted to the outer cylindrical electrode. A liquid state detection sensor comprising:
The outer cylindrical electrode has an outer surrounding portion that extends below the downward surface of the support member and forms a space on the outside and the inside of the tip of the element,
One or a plurality of bubble exhaust penetrating portions that communicate with the inside and outside are formed on the side wall of the outer surrounding portion, and when the element is submerged in the liquid with its tip portion downward, Bubbles that have penetrated into the liquid in the space inside are configured to pass through the through portion and be discharged to the outside of the outer enclosure portion,
Moreover, a notch portion is formed in a portion corresponding to the penetrating portion in the circumferential direction of the outer surrounding portion of the intersecting ridge portion formed by the downward surface and the outer peripheral surface of the support member, or in the circumferential direction. A chamfer is formed along
At least a part of the penetrating portion is disposed within a height range of the notched portion or the chamfered portion.   The downward surface of the support member is a flat surface as a whole, an upward inclined surface that becomes higher as it goes from the inner side to the outer peripheral edge, or an upward inclined surface that becomes higher as it goes from the inner side to the outer peripheral edge at least at a portion near the outer peripheral edge The liquid state detection sensor according to claim 1, wherein the liquid state detection sensor is formed. The liquid state detection sensor according to claim 1, wherein the notch portion or the chamfered portion of the support member is formed in an inclined chamfered shape. A positioning member having a positioning plate portion for positioning the support member on the downward surface thereof is attached to the downward surface side of the support member and inside the outer cylinder electrode.
The positioning plate portion includes a notch portion through which bubbles can pass in a portion corresponding to the penetrating portion in the circumferential direction formed in the outer surrounding portion of the outer peripheral edge or a portion near the outer peripheral edge. The liquid state detection sensor according to claim 1, wherein the liquid state detection sensor is a liquid state detection sensor. A liquid concentration detecting element for detecting the concentration of a specific component in the liquid;
A holder member configured to hold the element in a state where a tip portion located at the lower end of the element is protruded from the lower end of the element;
A cylindrical or annular support member that is externally fitted to the outer peripheral surface of the holder member so that its downward surface does not become lower than the lower end of the holder member;
It is formed in a cylindrical or annular shape that is externally fitted to the outer peripheral surface of the support member so that a space is formed below the downward surface of the support member and outside the tip of the element and inside the element. A liquid state detection sensor comprising:
One or a plurality of penetrating portions leading to the inside and the outside are formed on the side wall of the outer surrounding member, and the space inside the outer surrounding member when the element is submerged in the liquid with its tip portion downward. Air bubbles that have entered into the liquid inside is configured to pass through the penetrating portion and be discharged to the outside of the outer surrounding member,
Moreover, a notch portion is formed in a portion corresponding to the penetrating portion in the circumferential direction of the outer surrounding member among the intersecting ridge portions formed by the downward surface and the outer peripheral surface of the support member, or in the circumferential direction. A chamfer is formed along
At least a part of the penetrating portion is disposed within a height range of the notched portion or the chamfered portion.   The downward surface of the support member is a flat surface as a whole, an upward inclined surface that becomes higher as it goes from the inner side to the outer peripheral edge, or an upward inclined surface that becomes higher as it goes from the inner side to the outer peripheral edge at least at a portion near the outer peripheral edge The liquid state detection sensor according to claim 5, wherein the liquid state detection sensor is formed. The liquid state detection sensor according to claim 5, wherein the cutout portion or the chamfered portion of the support member is formed in an inclined chamfered shape.

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