JP2008261672A - Liquid state detection element fitted with terminal fitting and liquid state detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminal joint structure effectively preventing joint fracture from happening even if external force is exerted on terminal fittings brazed to a metal layer which is an external terminal of a liquid state detection element. <P>SOLUTION: This liquid state detection element fitted with terminal fittings comprises: a liquid state detection element 110 equipped with a heating resistance element 117 with its resistance value changing according to its own temperature within an insulated substrate while equipped with an external terminal 114 connected to the resistance element 117 on one principal surface 111c of the insulated substrate; and the terminal fittings 201 brazed to the external terminal 114 via an element-side joint part 203a. Aside from a first metal layer 114 which is the external terminal, the element 110 is equipped with a second metal layer 124 on a principal surface 112c on the opposite side thereof. The terminal fittings 201 each comprise a joint part 203b for the second metal layer in addition to the element-side joint part 203a, with the joint part 203a brazed to the metal layer 124. Joint strength is doubled owing to this brazing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid state detection element with terminal fittings and a liquid state detection sensor using the liquid state detection element with terminal fittings.

  In an exhaust gas purification apparatus that reduces nitrogen oxide (NOx) discharged from a diesel vehicle, a NOx selective reduction (SCR) catalyst may be used, and an aqueous urea solution is used as the reducing agent. In order to perform this reduction reaction efficiently, it is preferable to use an aqueous urea solution having a urea concentration of 32.5 wt%. However, the urea concentration of a urea aqueous solution stored in a urea water tank mounted on a diesel vehicle may change due to a change with time. In addition, a different type solution (such as light oil) or water may be mistakenly mixed into the urea water tank. Therefore, a liquid state detection sensor (also referred to as a urea concentration identification device) for managing the state of the liquid (liquid) such as the urea concentration of the urea aqueous solution in the tank has been proposed (Patent Document 1).

  In the liquid state detection sensor (urea concentration discriminating device) described in Patent Document 1, there is a side having a detection element (thin film chip) in which a substrate, a temperature sensing element, an insulating layer, a heating element, and a protective layer are sequentially laminated. A thermal concentration detector is provided. In this apparatus, the heating element is energized for a predetermined time, and the urea concentration is detected based on the temperature change of the heating element measured by the temperature sensing element before and after the energization. Specifically, by utilizing the difference in the temperature change of the heating element due to the difference in the urea concentration, the concentration is detected by detecting the temperature change of the heating element. In the sensing element used in this apparatus, since it is necessary to prevent the aqueous urea solution from entering the inside, this sensing element is molded with resin. For this reason, it is difficult for heat to be transmitted to the urea aqueous solution, and therefore the aqueous solution is difficult to increase in temperature, so that a difference in temperature change of the temperature sensing element of the element hardly occurs and the detection sensitivity is not good.

  Under such circumstances, the inventor of the present application has proposed a liquid state detection sensor using a liquid state detection element in which a heating resistor is sealed in, for example, a two-layer ceramic laminate (Patent Document 2). Since the liquid state detection element in this liquid state detection sensor has a ceramic laminate structure in which a heating resistor is sealed in a ceramic laminate, liquid does not enter the inside. Therefore, since the element itself can be directly immersed in a liquid (urea aqueous solution), compared with the element having a structure in which the periphery is molded with a resin, heat conduction is also good, and therefore sensitivity or response characteristics as a sensor are improved. improves. In addition, in such a liquid state detection element having a ceramic laminate structure, since a heating resistor whose resistance value changes according to its own temperature is used, if the heating resistor is energized, the concentration of liquid, etc. Depending on the liquid state, a signal corresponding to the resistance value of the heating resistor can be obtained. Therefore, based on this signal, the state of the liquid (liquid) such as the liquid concentration (concentration of the predetermined component in the liquid) can be detected.

FIG. 11 shows a liquid state detecting element 110 constituting the liquid state detecting sensor described in Patent Document 2. This element 110 includes a ceramic laminated body (not shown) including a heating resistor (not shown). One main surface (main surface) 111 of the insulating base) is provided with a pair of energization or voltage application external terminals (metal layers) 114 connected to the heating resistor. A terminal fitting 201 is joined to the external terminal 114 by brazing or soldering via an element-side joint 203 at the left end of the figure, and an electric wire (not shown) is attached to a barrel (not shown) of the terminal fitting 201. Connected and wired to controller. In addition, such an element 110 is provided, for example in the front-end | tip part of a cylindrical body, and comprises a liquid state detection sensor. This sensor is used by being attached to a urea water tank mounted on a diesel vehicle. At that time, the element 110 is attached so as to be immersed in a urea aqueous solution accommodated in the tank. . In addition, in this specification, the liquid state means the presence / absence of the liquid (liquid) to be measured (state of whether or not the liquid is present) and the type of liquid (what the liquid is) in addition to the concentration and temperature of the liquid. ).
JP-A-2005-84026 Japanese Patent Application No. 2005-200808

  By the way, the terminal fitting 201 is brazed or soldered to the external terminal (metal layer) 114 in the liquid state detecting element 110 as described above via the element side joint portion 203 as described above (hereinafter simply referred to as “soldering”). Although it is also connected by brazing), external force acts on the terminal fitting 201 or the electric wire connected thereto due to various causes caused by traveling of the automobile or the like. Of course, in the joint portion (brazing portion) between the external terminal 114 in the element 110 and the element side joint portion 203 in the terminal fitting 201, defects such as separation or breakage occur in the solder in the terminal joint portion from such an external force. It is set not to. However, an external force (mainly a tensile force) of an unexpected magnitude may be applied to the terminal joint due to a pulling action on the electric wire. For this reason, there is a possibility that the joint breakage may occur at the terminal joint, such as when the solder at the joint breaks, or the terminal fitting 201 is peeled off from the external terminal 114 of the element 110 or separated by being twisted. There was an indication that there was. Needless to say, the occurrence of such breakage inevitably becomes a cause of sensor failure.

  Therefore, the first possible countermeasure is to increase the brazing area between the external terminal 114 in the element 110 and the element-side joint 203 in the terminal fitting 201. This leads to an increase in size and the size of the terminal fitting 201, resulting in an increase in the size of the element. In addition, by increasing the brazing area in this way, the joint strength can be temporarily improved, but sufficient effects cannot be obtained by itself. This is because, according to the inventor of the present application, the cause of the joint breakage in the terminal joint structure is also due to a certain imbalance due to the brazing being performed on one side of the element 110. It is. This is because in such a terminal joint structure, the direction of action of the external force (tensile force) on the electric wire is not necessarily parallel to the main surface (surface) 111 of the element 110 on which the external terminal 114 is formed. This is because they tend to be inclined with respect to the surface. That is, in such a case, since a peeling force acts on the terminal fitting 201 that is bonded, the bonding fracture occurs even with a relatively small force.

  The present invention was made in view of such problems, and even if an external force is applied to the terminal fitting brazed to the metal layer that is the external terminal without causing an increase in the size of the liquid state detection element, An object of the present invention is to provide a liquid state detection element with a terminal fitting and a liquid state detection sensor using the same, having a high-strength terminal joint structure capable of effectively preventing the joint breakage.

According to the first aspect of the present invention, the heating resistor is provided on one main surface of a plate-like insulating base formed by sealing a heating resistor whose resistance value changes according to its own temperature. A liquid state detection element comprising a first metal layer which is an external terminal connected to
The first metal layer is provided with a terminal fitting joined by brazing or soldering via an element side joining portion,
In the liquid state detection element, apart from the first metal layer, a second metal layer is provided on a main surface opposite to the one main surface,
The terminal fitting includes a second metal layer joint in addition to the element side joint, and the second metal layer joint is joined to the second metal layer by brazing or soldering. This is a liquid state detection element with terminal fittings.

  According to a second aspect of the present invention, in the terminal according to the first aspect, the second metal layer is provided at a portion facing the first metal layer through the insulating base. It is a liquid state detection element with metal fittings. According to a third aspect of the present invention, in the liquid state detection element, the second metal layer is not electrically connected to the first metal layer. The liquid with terminal fittings according to the first or second aspect It is a state detection element. According to a fourth aspect of the present invention, in the liquid state detection element, the second metal layer is electrically connected to the first metal layer. The liquid with terminal fitting according to the first or second aspect, It is a state detection element.

  According to a fifth aspect of the present invention, the element side joint portion and the second metal layer joint portion of the terminal fitting are formed in a bifurcated shape so as to sandwich the liquid state detection element on both main surfaces thereof. In addition, the crotch portion is in contact with an end portion of the liquid state detecting element. The liquid state detecting element according to any one of claims 1 to 4.

Invention of Claim 6 is the liquid state detection element with a terminal metal fitting of any one of Claims 1-5,
A detection unit that detects a state of a liquid that is a detection target based on an output signal that is output in response to the resistance value of the heating resistor when the heating resistor is energized. It is a liquid state detection sensor. The invention according to claim 7 is the liquid state detection sensor according to claim 6, wherein the liquid is an aqueous urea solution.

  In the liquid state detecting element with terminal fittings of the present invention (hereinafter also simply referred to as element), the terminal fitting joined to the first metal layer as the external terminal is the main surface (main surface) on the opposite side of the liquid state detecting element. ) Is also joined by brazing or soldering (hereinafter also simply referred to as brazing). That is, the external terminal (first metal layer of the present invention) in the conventional element is formed only on one main surface, and the terminal fitting is brazed to the external terminal via the element side joint. It has a terminal junction structure. For this reason, when a tensile force (load) is applied between the terminal fitting and the external terminal of the element by pulling the terminal fitting or an electric wire connected to the terminal fitting or the like, the soldering braze breaks. As a result, there was a high risk that the terminal fittings were separated from the external terminals. In particular, since such a tensile force tends to be applied to the main surface of the element in an inclined manner, in such a case, a peeling force acts on the terminal fitting at the brazed portion, so even a relatively small force can be applied. Bonding breakage occurred.

  On the other hand, when the invention according to claim 1 or 2 is applied, the element is provided with a second metal layer on the opposite main surface separately from the first metal layer which is the external terminal. On the other hand, the terminal fitting includes a second metal layer joint in addition to the element side joint, and the second metal layer joint is brazed or soldered to the second metal layer. It is joined. That is, two joint portions of the terminal fitting are joined to two metal layers provided on both surfaces of the element by brazing or the like. Therefore, even if a tensile force (load) is applied between the terminal fitting or the electric wire connected thereto and the external terminal (first metal layer) in the element, the bonding strength is doubled. It can effectively resist such external force. As described above, according to the element of the present invention, even if an external force is applied to the terminal fitting brazed to the metal layer that is the external terminal (first metal layer) without enlarging the size, It can be made to have a high-strength terminal joint structure, such as effectively preventing breakage.

  In addition, according to the element of the present invention, since the heating resistor whose resistance value changes according to its own temperature is provided, when the heating resistor is energized, the resistance value of the heating resistor is set according to the liquid state. Since a corresponding signal can be obtained, the liquid state can be detected based on this signal. In the element of the present invention, since the heating resistor is sealed in the insulating substrate, the element itself can be directly immersed in the liquid. Therefore, the sensitivity is superior to the element molded with resin around.

  As described in claim 3, the second metal layer is not electrically connected to the first metal layer and is intended only for mechanical joining with a terminal fitting (ie, a dummy terminal). However, as described in claim 4, when it is assumed that the first metal layer is electrically connected, the brazing in one of the first metal layer and the second metal layer is broken. However, since there is no immediate disconnection, a highly safe terminal connection structure can be obtained.

  Further, as described in claim 5, the element side joint portion and the second metal layer joint portion of the terminal fitting are formed in a bifurcated shape so as to sandwich the liquid state detection element on both main surfaces thereof. In addition, in the case where the crotch portion is held in contact with the end portion of the liquid state detecting element, the contact can be used for positioning at the time of brazing, so that the positioning is easy. it can. Further, after brazing, since the crotch portion is in contact with the end portion of the element, the terminal metal can be prevented from wobbling or shaking, so that an increase in strength is expected.

  In addition, since the liquid state detection sensor according to claim 6 includes a heating resistor whose resistance value changes according to its own temperature, and includes an element that is immersed in the liquid that forms the detection target, the heating resistor. The liquid state can be detected on the basis of an output signal output corresponding to the resistance value of the heating resistor by energizing the resistor.

  Next, an embodiment of a liquid state detection element with a terminal fitting according to the present invention will be described with reference to FIGS. 1 to 6. First, the liquid state detection element 110 will be described. The liquid state detection element 110 according to the present embodiment has an elongated rectangular plate shape, and has a laminated structure composed of first and second ceramic insulating layers 111 and 112 as shown in FIG. Yes. A conductor layer 118 including a heating resistor 117 is provided between the first ceramic insulating layer 111 and the second ceramic insulating layer 112 (interlayer portion), and is formed by simultaneous firing. In this structure, the inner conductor layer 118 is sealed in a liquid-tight manner between the first ceramic insulating layer 111 and the second ceramic insulating layer 112. Therefore, the element 110 is immersed directly in an aqueous urea solution. However, there is no possibility that the aqueous solution of urea is submerged therein and the conductor layer 118 is short-circuited.

  The conductor layer 118 is mainly composed of Pt. As shown in FIGS. 3 and 4, as shown in FIGS. 3 and 4, the heating resistor 117 disposed on the tip (bottom of FIGS. 3 and 4) side of the element 110, Lead portions 115 and 116 are provided between both insulating layers 111 and 112, which are connected to both ends of the heating resistor 117 and extend along the left and right long sides of the element 110, respectively. The main surface (front surface) 111c exposed to the outside of the first ceramic insulating layer 111 corresponding to a portion closer to the rear ends (FIG. 3, 4 upper ends) of the lead portions 115 and 116 is connected to the heating resistor 117. A pair of metal layers (hereinafter also referred to as first metal layers) 114 forming external terminals for energization are formed. The first metal layer 114 has a vertically long rectangular shape along the element 110 and is electrically connected to the rear end portions of the left and right lead portions 115 and 116 via the via conductor 113.

  The conductor layer 118 has a pattern as shown in FIG. 3 when the main surface of the element 110 is viewed in plan view. As described above, the conductor layer 118 extends forward and backward along the long side of the rectangle. The first lead portion 115, the second lead portion 116, and the heating resistor 117 connected to both of them at a portion near the tip are provided. The heating resistor 117 includes a plurality of parallel linear portions 117b extending linearly in parallel with each other in the longitudinal direction (vertical direction in FIG. 3) of the second ceramic insulating layer 112, and adjacent parallel linear portions 117b. As a whole, a line shape having a smaller cross-sectional area meanderingly extends than the first lead part 115 and the second lead part 116. There is no. For this reason, when the conductive layer 118 is energized, the heat generating resistor 117 is mainly configured to generate heat. The resistance value of the heating resistor 117 changes according to its own temperature.

  In addition, as described above, the element 110 includes the surface 111c of the first ceramic insulating layer 111 that forms one main surface of the element 110 at each rear end portion of the first lead portion 115 and the second lead portion 116. In addition, a metal layer (first metal layer) 114 that forms an external terminal (connection pad) is provided. The first metal layers 114 and 114 are electrically connected to the first lead portion 115 and the second lead portion 116 through vias (conductors) 113 and 113 that penetrate the first ceramic insulating layer 111, respectively. It is connected to the.

  On the other hand, in this embodiment, as shown in FIG. 4, among the second ceramic insulating layers 112 forming the liquid state detecting element 110, they correspond to the first metal layers 114 and 114 on the surface 111 c of the first ceramic insulating layer 111. On the surface 112c of the part, metal layers (second metal layer of the present invention; hereinafter also referred to as second metal layer) 124, 124 having the same size and shape (shape) as the first metal layer 114 are provided. That is, the first metal layer 114 and the second metal layer 124 are opposed to each other with the first ceramic insulating layer 111 and the second ceramic insulating layer 112 interposed therebetween. In the present embodiment, the second metal layer 124 is also formed by simultaneous firing with Pt as a main component. The first metal layer 114 and the second metal layer 124 do not have to be in the corresponding positions (same positions) on the front and back surfaces 111c and 112c of the element 110 (they may be shifted), but such a positional relationship. Therefore, the element 110 of this embodiment has the same appearance on both the front and back surfaces. Further, in the terminal fitting 201 to be described next, each joint portion to the metal layers 114 and 124 can be formed in the same form.

  Such a liquid state detection element 110 is manufactured as follows. A via hole 111b is drilled at a position corresponding to the via of the ceramic green sheet forming the first ceramic insulating layer 111, and Pt is formed at a portion corresponding to each of the metallized layers of the conductor layer 118 and the via 113, and further the first metal layer 114. A metallized paste containing as a main component is printed. On the other hand, the same metallized paste is printed on the portion corresponding to the second metal layer 124 of the ceramic green sheet forming the second ceramic insulating layer 112. Next, both ceramic green sheets are laminated, pressure-bonded, and fired simultaneously. Then, necessary plating is applied to the surface of the first metal layer 114 and the like that form the exposed external terminal of the liquid state detection element 110. The first and second metal layers 114 and 124 of the element 110 have terminal fittings (connectors) 121 described below via the element-side joint 203a and the second metal layer joint 203b. For example, it is joined (brazed) with silver solder to form a liquid state detecting element with terminal fittings.

  Next, the terminal fitting 201 of this embodiment will be described with reference to FIGS. 1 and 2 and FIGS. However, in the present embodiment, the left and right terminal fittings 201 have a symmetrical shape but are substantially the same, and therefore one of them will be described. That is, the terminal fitting 201 is formed of a thin metal plate, and has a U shape so that the core wire at the tip of the electric wire (end portion) 90 is connected to one end (upper end in FIG. 1) by crimping (caulking). A crimping part (barrel) 211 having a certain length formed by bending is provided. At the other end, an external terminal first metal layer 114 formed on the main surface 111c of the first ceramic insulating layer 111 of the element 110 and a main surface 112c of the second ceramic insulating layer 112 are formed. An element-side joint 203a and a second metal layer joint 203b are formed on the second metal layer 124 so that they can be joined to each other by brazing so that the two surfaces extend substantially parallel to each other. Yes. That is, the terminal fitting 201 of this embodiment includes a crimping portion 211 at one end, two joint portions 203a and 203b at the other end, and a relay wire portion 207 that integrally connects them. The relay wire portion 207 is formed of a strip 208 having a narrow portion near the crimping portion, and the two portions near the joining portion are formed by bending a wider strip so as to form a U-shaped portion 204 in the cross section. Yes. Of these, the joint portions 203a and 203b are formed so as to extend in a bifurcated shape from the ends of both flange portions 204b of the U-shaped portion 204 to sandwich the element 110 between the two principal surfaces 111c and 112c. It can be attached. However, about half of the portions closer to the tips of both joints 203a and 203b are bent so that the parallel distance between them is slightly reduced. Further, the thin band plate 208 near the crimping portion of the relay wire portion 207 is bent obliquely toward the opening side of the U-shaped portion 204, and in the vicinity of the crimping portion 211, the crimping portion 211 is joined to the joint portion 203a. , 203b are bent so as to extend substantially in parallel with each other.

  Note that the connecting wire portion 207 is bent when a connecting portion (hereinafter referred to as a web) 204 c that connects the upper portion and the lower portion of the U-shaped portion 204 when the terminal fitting 201 is joined to the element 110. Since the bifurcated joints 203a and 203b are brazed to the first and second metal layers 114 and 124 so as to be located near the center of the direction, the crimping portion in the brazed state 211 is separated from the crimping part 211 of the other terminal fitting 201. Further, in this embodiment, the band plate 208 forming the relay wire portion 207 is twisted 90 degrees near the crimping portion 211, whereby the U-shaped opening of the crimping portion 211 and the opening of the U-shaped material are 90 °. It is designed to face in different directions.

  The liquid state detecting element 110 and the terminal fitting 201 are brazed with, for example, silver solder as follows. That is, in both of the above-described terminal fittings 201 used in this embodiment, the web 204c of the U-shaped portion 204 in each relay line portion 207 is positioned at the center portion in the width direction of the element 110 at the rear end 110b of the element 110. . Next, the bifurcated joints 203a and 203b sandwich the element 110 between the first and second metal layers 114 and 124 on both sides. Then, the end of the web 204c of the U-shaped portion 204 of the junction line portion 207 forming the crotch portion 203c of the joint portions 203a and 203b extending in a bifurcated shape is brought into contact with the rear end 110b of the element 110. The element 110 is positioned with respect to the front and rear. In this state, the first and second metal layers 114 and 124 of each element 110 are brazed to both the joints 203a and 203b of the terminal fitting 201, respectively.

  In this embodiment, in brazing, since the element 110 can be positioned before and after the brazing, the joining process is facilitated. In addition, what is necessary is just to connect the front-end | tip of the electric wire 90 to the crimping | compression-bonding part 211 of the terminal metal fitting 201 by crimping before or after brazing.

  Thus, in the joint structure of the liquid state detecting element with terminal fittings of the present embodiment in which the element 110 and the terminal fitting 201 are joined in this way, each terminal fitting 201 extends in a bifurcated shape. The joint portions 203a and 203b are brazed to the metal layers 114 and 124 on both surfaces of the element 110, respectively. That is, in this embodiment, in addition to the first metal layer 114 formed on one main surface 111c for energizing the heating resistor 117, the second metal layer 124 formed independently on the other main surface 112c. In addition, the joint portions (element side joint portion 203a and second metal layer joint portion 203b) in one terminal fitting 201 are brazed. Therefore, in such an element with a terminal fitting, when a tensile force is applied to the terminal fitting 201, only the element-side joint is brazed to the first metal layer that forms the external terminal, as in the past. Compared to the case, since the bonding strength can hold about twice the strength, high reliability is maintained.

  In the element with terminal fittings of the above-described form, the second metal layer 124 in the element 110 and the second metal layer bonding portion 203b in the terminal fitting 201 have only an action for ensuring the bonding strength. As shown, the second metal layer 124 is also electrically connected to the portions near the rear ends of the left and right lead portions 115 and 116 through vias (via conductors) 113b, similarly to the first metal layer 114. You may keep it. In this way, even if one of the metal layers is disconnected from the joints 203a and 203b of the terminal fitting 201, there will be no immediate joint failure. In this embodiment, the terminal fitting 201 is prevented from shaking because the crotch portion 203c of the element side bonding portion 203a and the second metal layer bonding portion 203b is in contact with the rear end (end portion) 110b of the element 110. Since each action of shaking prevention is achieved, the bonding strength can be increased.

  In addition, according to the element 110 described above, since the heating resistor 117 whose resistance value changes according to its own temperature is provided, when the heating resistor 117 is energized, the heating resistor 117 of the heating resistor 117 depends on the liquid state. Since a signal corresponding to the resistance value can be obtained, the liquid state can be detected based on this signal. In the element 110 described above, since the heating resistor 117 is sealed in the insulating base (ceramic insulating layer), the element 110 itself can be directly immersed in the liquid. Therefore, the sensitivity can be improved as compared with an element whose periphery is molded with resin.

  Next, another example of the terminal fitting will be described with reference to FIG. However, the terminal fitting 301 is basically the same as the terminal fitting 201 described above, and there is no essential difference. Therefore, only the differences will be described, and the same parts are only given the same reference numerals. That is, in the terminal fitting 301, the element side joint portion 203a and the second metal layer joint portion 203b are not bifurcated as in the above embodiment, and the crossing in the relay line portion 207 in the above embodiment is performed. The U-shaped portion 204 has a shape extending toward the tip while maintaining its transverse cross section. However, in the terminal fitting 301, the band-shaped portion 204 is open so that the openings of the U-shaped portions 204 face each other and the crimping portions 211 are separated from each other so that the terminal fitting 301 can be attached from both outer sides of the element 110. A plate 208 is bent. In such a terminal fitting 301, the web 204c of the U-shaped portion 204 is pressed against the side surface of the element 110, and the portions connected to both flanges 204b serve as joint portions 203a and 203b, so that both main surfaces 111c and 112c of the element 110 are formed. However, the strength of the terminal fitting 301 itself is enhanced by the fact that the joint portions 203a and 203b have a U-shaped cross section.

  Next, a liquid state detection sensor 100 using the liquid state detection element with terminal fittings having the above-described configuration will be described with reference to FIG. FIG. 8 is a fragmentary longitudinal sectional view for explaining the entire liquid state detection sensor 100 according to the present embodiment. As shown in FIG. 8, the liquid state detection sensor 100 includes a cylindrical outer cylinder electrode 10, a cylindrical inner cylinder electrode 20 that is held inside the inner cylinder electrode 20, and the inner cylinder electrode 20. The above-described liquid state detection element 110 arranged at the tip (lower end in FIG. 8) and these electrodes 10 and 20 are fixed at the upper end in the drawing, and the sensor 100 itself is mounted on, for example, a top plate portion of a urea water tank (not shown). It is comprised from the attaching part 40 etc. which have a flange for attaching.

  In addition, a detection unit 160 including a wiring board 60 on which a CPU and the like are mounted is provided at the upper portion of the attachment unit 40 in the drawing, and will be covered with a protective cover 161. Hereinafter, the liquid state detection sensor 100 as a whole is viewed in the vertical direction in the figure, and the liquid state detection element 110 located below is the front end side, and the detection unit 160 located above is the rear end side. Will be described. The liquid state detection sensor 100 of the present embodiment is immersed in the urea aqueous solution in the urea water tank, the liquid state detection element 110 determines the concentration of the same liquid, and both the electrodes 10 and 20 have the liquid level. It is formed to detect.

  The outer cylinder electrode 10 constituting the sensor 100 is made of a metal and has a cylindrical straight tube, and is fixed in a suspended state from the upper mounting portion 40 with its axis G being up and down. The outer cylinder electrode 10 is fixed to the attachment portion 40 by welding the rear end portion (upper end in the drawing) 12 to the attachment portion 40. The attachment portion 40 is connected to the wiring substrate 60 constituting the detection portion 160 so as to have the same potential as a wiring portion (not shown) that forms the ground potential, and is welded to the attachment portion 40. The outer cylinder electrode 10 is also set to the ground potential.

  On the other hand, the inner cylinder electrode 20 is made of metal and has a cylindrical straight tube having a smaller diameter than the outer cylinder electrode 10, and the inner cylinder electrode 20 is arranged inside the outer cylinder electrode 10 with its axis line coincident with the axis G. Although not shown, the inner cylinder electrode 20 is fixed to the attachment portion 40 via an insulating member at the rear end portion. Further, the length of the distal end portion is set so as not to protrude from the distal end of the outer cylindrical electrode 10, and the insulating portion is elastically retained inside the portion closer to the distal end of the outer cylindrical electrode 10 as described later. It is supported. In this embodiment, the above-described liquid state detection element 110 is arranged so as to protrude from the inner tip of the inner cylinder electrode 20 inside the portion closer to the tip of the outer cylinder electrode 10.

  The detailed configuration of the liquid state detection element 110 (hereinafter also simply referred to as the element 110) itself is as described above. This element 110 has a sealing member at the intermediate portion of the element 110 itself by a fixing member (resin) 126 filled in a small-diameter portion at the bottom of a holder 120 having a different diameter cylindrical shape attached to the tip of the inner cylinder electrode 20. The portion near the tip is projected from the tip of the holder 120 by a predetermined amount. In addition, the holder 120 fixing the element 110 is externally fitted on the outer peripheral surface of the distal end portion of the inner cylindrical electrode 20 with the large-diameter portion at the upper portion interposed with a sealant (rubber ring) 127 inside. It is attached with. In addition, an electric wire 90 connected via a metal fitting 201 to a metal layer (hereinafter also referred to as an external terminal) 114 for energizing the heating resistor 117 inside the element 110 is passed through the inner cylindrical electrode 20. Then, it is pulled out to the rear end side and is electrically connected to the wiring board 60 constituting the detection unit 160.

  As described above, the holder 120 formed by holding and fixing the element 110 and externally fitted to the outside of the distal end portion of the inner cylindrical electrode 20 has a holder contact portion that is in close contact with the outer peripheral surface thereof, and the liquid state detection element 110. A protector 130 formed in a cylindrical shape with a different diameter is installed so as to surround and protect. However, the protector 130 is provided with a plurality of through holes for allowing the urea aqueous solution to flow inside and outside thereof. On the other hand, a rubber bush 80 having a large inner diameter and a different diameter cylindrical shape is fitted and fixed inside the portion near the tip of the outer cylinder electrode 10, and a holder adhesion portion of the protector 130 is formed inside the rubber bush 80. Thus, the holder 120 is fitted, whereby the liquid state detection element 110 is elastically supported together with the tip of the inner cylinder electrode 20. The rubber bush 80 is fixed to the outer cylinder electrode 10 by fitting a protrusion formed on the outer peripheral surface of the rubber bush 80 into a through hole formed on the peripheral surface (cylinder wall) of the outer cylinder electrode 10. .

  Further, in this embodiment, the inner cylinder electrode 20 is configured to be electrically connected to the wiring board 60 constituting the detection unit 160 and to be applied with an AC voltage. An insulating coating 23 made of a fluororesin is formed on the outer surface of the inner cylinder electrode 20 that contacts the urea aqueous solution. The mounting portion 40 that fixes the outer cylindrical electrode 10 and the inner cylindrical electrode 20 at the rear end is made of a metal plate, and a through-hole for bolts (not shown) is drilled in the surrounding flange portion. Yes. Thus, the liquid state detection sensor 100 is configured to be attached to the urea water tank through the attachment bolt through the bolt through hole of the attachment portion 40.

  Next, a detection system in this sensor will be described. As described above, the detection unit 160 includes the wiring board 60 on which a CPU and the like are mounted, and is disposed inside the protective cover 161. As shown in FIG. 9, the detection unit 160 includes a microcomputer 220, a first detection circuit unit 280, a second detection circuit unit 250, and an input / output circuit unit 290. Among these, the microcomputer 220 includes a CPU 221, a ROM 222, and a RAM 223, and performs various controls. The input / output circuit unit 290 controls a communication protocol for inputting / outputting signals between the microcomputer 220 and an ECU (engine control unit).

  The second detection circuit unit 250 applies a predetermined AC voltage between the outer cylinder electrode 10 and the inner cylinder electrode 20 based on a command from the microcomputer 220. The current flowing at this time is converted into a voltage, and the voltage signal is output to the microcomputer 220. In the microcomputer 220, the capacitance between the outer cylinder electrode 10 and the inner cylinder electrode 20 differs depending on the amount of the urea aqueous solution L located between the outer cylinder electrode 10 and the inner cylinder electrode 20. Based on the output voltage signal, the liquid level of the urea aqueous solution L can be detected.

  The first detection circuit unit 280 includes a differential amplifier circuit unit 230, a constant current output unit 240, and a switch 260. The first detection circuit unit 280 applies a constant current to the liquid state detection element 110 based on a command from the microcomputer 220 and outputs a voltage signal output corresponding to the resistance value of the heating resistor 117 to the microcomputer. To 220.

  Specifically, the constant current output unit 240 is electrically connected to the heating resistor 117 and outputs a constant current. The switch 260 is located on the energization path between the constant current output unit 240 and the heating resistor 117, and on / off of energization from the constant current output unit 240 to the heating resistor 117 based on a command from the microcomputer 220. Switch. The differential amplifier circuit unit 230 outputs a difference value between the input terminal side potential Pin and the output terminal side potential Pout of the heating resistor 117 to the microcomputer 220 as a detection voltage value. Thereby, the microcomputer 220 calculates, for example, the urea concentration of the urea aqueous solution L based on the detected voltage value, detects whether the urea concentration is appropriate, or calculates the temperature of the urea aqueous solution L. Can be.

  For example, when the urea concentration of the urea aqueous solution L is 32.5 wt%, as indicated by the solid line in FIG. 10, the voltage of the heating resistor 117 varies as the energization time elapses. This will be described with reference to this example. First, a constant current is supplied from the constant current output unit 240 to the heating resistor 117 and immediately after the heating resistor 117 is energized (specifically, the heating resistor 117 is energized). A voltage signal (first detection voltage value V1) output corresponding to the resistance value of the heating resistor 117 is detected 10 seconds after the start). Next, after a predetermined energization time t1 (for example, t1 = 700 msec) has elapsed since the start of energization, a voltage signal (second detection voltage value V2) output corresponding to the resistance value of the heating resistor 117 is detected.

  Next, a difference value ΔV (ΔV1 in this example) = V2−V1 between V2 and V1 is calculated, and this ΔV (ΔV1 in this example) is a threshold value Q (ΔV acquired in advance for urea aqueous solutions L of various concentrations). If it is equal to or less than the maximum value, it can be determined that the urea water tank 98 contains the urea aqueous solution L. Furthermore, if the urea concentration of the urea aqueous solution is calculated based on a predetermined arithmetic expression, it can be determined whether or not the urea concentration is appropriate. In this example, the urea concentration is calculated as 32.5 wt%, and the urea concentration is determined to be appropriate.

  This is realized based on the following principle. Since the thermal conductivity of the urea aqueous solution L varies depending on the concentration of urea contained in the urea aqueous solution L, when the urea aqueous solution L is heated by the heating resistor 117, the temperature of the urea aqueous solution L increases due to the difference in urea concentration. The rate will be different. For this reason, the temperature increase rate of the urea aqueous solution L (that is, the concentration of the urea aqueous solution L) affects the temperature increase of the heating resistor 117 included in the liquid state detection element 110 immersed in the urea aqueous solution L. .

  As described above, the resistance value of the heating resistor 117 changes according to its own temperature. Therefore, after a constant current is passed through the heating resistor 117 for a predetermined time, a difference occurs in the resistance value of the heating resistor 117 due to a difference in urea concentration of the urea aqueous solution L or a difference in liquid type. For this reason, when a constant current is passed through the heating resistor 117 for a predetermined energization time t1, a difference value ΔV between the first detection voltage value V1 and the second detection voltage value V2 due to a difference in urea concentration of the urea aqueous solution L or the like. = V2−V1 is also different. Therefore, it is possible to detect the urea concentration of the urea aqueous solution L or the difference in the liquid type based on ΔV. Further, since the temperature of the resistance value of the heating resistor 117 immediately after the start of energization is substantially the same as the temperature of the aqueous urea solution L located around the liquid state detection element 110 (the heating resistor 117), immediately after the start of energization. The resistance value of the heating resistor 117 is a resistance value corresponding to the temperature of the urea aqueous solution L located around the liquid state detection element 110 (heating resistor 117). Therefore, the temperature of the urea aqueous solution L can also be detected using the first detection voltage value V1.

  By the way, when ΔV exceeds the threshold value Q, an appropriate urea aqueous solution is not stored in the urea water tank 98. Specifically, when a liquid (specifically, light oil or the like) different from the urea aqueous solution L is injected into the urea water tank 98, ΔV exceeds the threshold value Q. Further, when the urea water tank 98 is empty, the value of ΔV is further increased.

  Therefore, if the threshold value R is set in advance based on ΔV acquired when the urea water tank 98 is empty, when the measured value of ΔV exceeds the threshold value Q and further exceeds the threshold value R, It can be determined that the urea water tank 98 is empty. On the other hand, when the actually measured ΔV is a value between the threshold value Q and the threshold value R, the urea water tank 98 is not empty, but the urea water tank 98 contains an appropriate urea aqueous solution L. It can also be determined that a liquid with low thermal conductivity (such as light oil) is contained. In this way, it is possible to detect an abnormality in the urea water tank 98 as well. Such abnormality detection is also an aspect of the state detection of the urea aqueous solution L.

  As described above, the sensor of the present invention has been described according to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the sensor can be appropriately changed and applied without departing from the gist thereof. . For example, in the liquid state detection sensor 100 of the above embodiment, the outer cylinder electrode 10 and the inner cylinder electrode 20 are provided to detect the liquid level of the urea aqueous solution L. However, in the sensor of the present invention, the outer cylinder electrode 10 and the inner cylinder electrode 20 may not be provided. However, in this case, as described above, it is preferable to detect an abnormality when the urea aqueous solution L becomes empty.

  In the liquid state detection sensor 100, the conductor layer 118 including the heating resistor 117 is formed mainly of Pt (platinum). However, the material of the conductor layer 118 is not limited to this, and W ( Tungsten) or the like may be used as a main component. Furthermore, a trace amount of ceramic components (alumina in this embodiment) constituting the first ceramic insulating layer 111 and the second ceramic insulating layer 112 may be added to the conductor layer 118.

The perspective view concerning embodiment of the liquid state detection element with a terminal metal fitting of the present invention. The figure (front view) which looked at the liquid state detection element with a terminal metal fitting of Drawing 1 from the principal surface side. The expanded fracture front view explaining the inside of the element of FIG. The figure which looked at the liquid state detection element with a terminal metal fitting of FIG. 1 from the side surface side, and the expanded fracture sectional view which exaggerated and showed the inside of the element for description. The exploded view of FIG. The perspective view of a terminal metal fitting (a pair) among the liquid state detection elements with a terminal metal fitting of FIG. The perspective view which shows another example of a terminal metal fitting (a pair). The partially broken sectional view of the liquid state detection sensor concerning an embodiment. The block diagram which shows the electrical structure of a liquid state detection sensor. The graph which shows an example of the fluctuation | variation of the voltage V of the heating resistor at the time of electricity supply. The figure explaining the problem in joining of a liquid state detection element and a terminal metal fitting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Liquid state detection sensor 110 Liquid state detection element 111 1st ceramic insulating layer 111c One main surface 112 of an insulation base | substrate 2nd ceramic insulating layer 112c Main surface 114 on the opposite side External terminal (1st metal layer)
117 Heating resistor 124 Second metal layer 160 Detection unit 201, 301 Terminal metal fitting 203a Element side joint 203b of terminal metal fitting 203b Second metal layer joint 203c of terminal metal fitting Element side joint and second metal layer joint Crotch

Claims (7)

A first metal layer serving as an external terminal connected to the heating resistor is provided on one main surface of a plate-like insulating substrate formed by sealing a heating resistor whose resistance value changes according to its own temperature. A liquid state detection element comprising:
The first metal layer is provided with a terminal fitting joined by brazing or soldering via an element side joining portion,
In the liquid state detection element, apart from the first metal layer, a second metal layer is provided on a main surface opposite to the one main surface,
The terminal fitting includes a second metal layer joint in addition to the element side joint, and the second metal layer joint is joined to the second metal layer by brazing or soldering. A liquid state detecting element with terminal fittings.   2. The liquid state detection element with terminal fitting according to claim 1, wherein the second metal layer is provided at a portion facing the first metal layer with the insulating base interposed therebetween.   3. The liquid state detecting element with terminal fitting according to claim 1, wherein the liquid state detecting element is configured such that the second metal layer is not electrically connected to the first metal layer.   The liquid state detecting element with terminal fitting according to claim 1 or 2, wherein the liquid state detecting element has a second metal layer electrically connected to the first metal layer.   The element side joint portion and the second metal layer joint portion of the terminal fitting are formed in a bifurcated shape so as to sandwich the liquid state detection element between both main surfaces thereof, and the crotch portion is in the liquid state. The liquid state detection element according to claim 1, wherein the liquid state detection element is in contact with an end portion of the detection element. The liquid state detection element with terminal fitting according to any one of claims 1 to 5,
A detection unit that detects a state of a liquid that is a detection target based on an output signal that is output in response to the resistance value of the heating resistor when the heating resistor is energized. Liquid state detection sensor.   The liquid state detection sensor according to claim 6, wherein the liquid is an aqueous urea solution.

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