JP4908351B2 - 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 the reducing agent. However, in order to effectively reduce nitrogen oxides with this device, the aqueous urea solution must be in an appropriate concentration range (range of urea concentration in the aqueous urea solution). is required.
However, even when a urea aqueous solution having an appropriate concentration is stored in the urea water tank storing 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 urea concentration identification device that is attached to a urea water tank and detects the urea concentration of an aqueous urea solution has been proposed (see Patent Documents 1 and 2).
In particular, in Patent Document 2, as the urea concentration identification device, a urea solution identification device capable of accurately and quickly identifying the urea concentration of the urea solution even while the vehicle is running is provided. That is, this Patent Document 2 (in particular, see FIGS. 1 and 2 of this document) has an indirectly heated concentration detection unit and a liquid temperature detection unit (detection unit) provided with metal fins in the concentration identification sensor unit. ing. In addition, the concentration identification sensor unit (liquid concentration detection element) is provided with a cover member that forms a urea solution introduction path so as to surround the metal fins, and a urea concentration identification that includes an enclosure in which flow holes are formed in the upper and lower end face plates. An apparatus (liquid state detection sensor) is described.

JP-A-11-153561 JP-A-2005-84025

In general, the liquid concentration detection element (concentration identification sensor unit) is configured in this manner around a detection unit (an indirectly heated concentration detection unit and a liquid temperature detection unit). Since the liquid (urea solution) that appropriately reflects the state such as the concentration and temperature of the entire urea solution) needs to be positioned, the liquid (urea solution) is appropriately detected around the detection unit. The liquid needs to be circulated so that the liquid can be exchanged with the liquid (urea solution) outside the (urea concentration identification device).
On the other hand, when the liquid (urea solution) around the detector moves violently, it is difficult to detect the state of the liquid (urea solution), such as concentration and temperature, due to this effect. This is because it is necessary to limit the movement of the liquid to some extent because the value error may increase.

By the way, the inventors have a liquid state detection sensor having a liquid concentration detection element, an outer protector, and an inner protector as a liquid state detection sensor for detecting a state such as the concentration of a liquid such as an aqueous urea solution. Is developing. Specifically, the outer protector has a distal end and a base end, and has a cylindrical shape extending along the axis. The distal end is opened to form a distal end opening, and the liquid concentration detecting element is disposed in the outer protector. And a detection unit for detecting the concentration of the specific component in the liquid. Further, the inner protector is disposed in the outer protector, and the detection part of the liquid concentration detection element is spaced from the detection part, and at least from the radially outer side of the axis line from at least the radially outer side of the axis line. The surrounding enclosure, which communicates with the tip of itself between the inside of the enclosure and a portion closer to the tip than the enclosure, and in the direction along the axis of the liquid (axial direction) between them It has an envelopment part in which a tip circulation hole which can be formed is formed.
Also in the liquid state detection sensor of such a form, the liquid exchange between the periphery of the detection unit of the liquid concentration detection element and the outside of the liquid state detection sensor, while the liquid around the detection unit is intense As with the case of Patent Document 2, it is necessary to consider the restriction on movement.

  On the other hand, in the concentration identification sensor unit (liquid concentration detection element) described in Patent Document 2, an enclosure is provided to deal with these problems, and the enclosure has a peripheral edge on the end surface of the cylindrical side plate. The plate-like upper end face plate and lower end face plate in which through holes are formed in the vicinity are arranged so that the through holes are shifted from each other, and abutted and fixed to the side plates (paragraph (0029) of Patent Document 2). reference). Specifically, it is understood that a flat upper end face plate and a lower end face plate are welded to the both end faces of the cylindrical side face plate over the entire circumference. Accordingly, it is understood that the liquid flow in the enclosure is suppressed while allowing a certain amount of liquid exchange through the through-hole, thereby suppressing the problem that the error of the concentration measurement value becomes large.

  However, for this enclosure, it is not preferable to weld the upper end face plate and the lower end face plate to the end face of the side face plate because of the number of man-hours. On the other hand, in order to perform spot welding on the end surface of the side plate using resistance welding or laser welding, the width of the end surface of the side plate is small (thin plate thickness is thin), so positioning is difficult and welding is unstable. There is a problem that tends to become. Also, brazing (soldering, brazing) requires heating of a urea concentration identification device (liquid state detection sensor) including a side plate, an upper end plate, or a lower end plate, which is inconvenient in terms of mass productivity and equipment.

The same can be said for a liquid state detection sensor having the above-described liquid concentration detection element, outer protector, and inner protector. That is, it is possible to prepare a flat lid member having a through hole, and press the outer protector against the tip of the outer protector so as to close the tip opening of the outer protector while leaving a through hole by the through hole. Conceivable.
However, in the same manner as described above, it is not preferable to weld the flat cover member to the tip of the outer protector over the entire circumference because it takes time. On the other hand, when spot welding is performed on the tip surface of the outer protector by resistance welding or laser welding, the width of the tip surface of the outer protector is small (thin plate thickness), so positioning is difficult and welding is unstable. There is a problem that tends to become. Also, brazing (soldering, brazing) requires heating of the liquid state detection sensor including the outer protector and the lid member, which is inconvenient in terms of mass productivity and equipment.

  The present invention has been made in view of such problems, and for a liquid state detection sensor having a liquid concentration detection element, an outer protector, and an inner protector, the periphery of the detection unit of the liquid concentration detection element, A member that enables liquid exchange with the outside of the liquid state detection sensor, can suppress the occurrence of intense liquid movement around the detection unit, and can appropriately control the liquid flowing through the tip opening of the outer protector. An object of the present invention is to provide a liquid state detection sensor which is easily and reliably welded.

  The solution means is a liquid state detection sensor for detecting the state of the liquid, and has a distal end and a base end, is a cylindrical shape extending along the axis, and an outer protector having the distal end opened to form a distal end opening; A liquid concentration detection element that is disposed in the outer protector and has a detection unit that detects the concentration of a specific component in the liquid, and a detection unit that detects the concentration of the liquid concentration detection element that is disposed in the outer protector. An inner protector having an enclosing portion that surrounds at least from the radially outer side of the axial line from the distal end side and from the radially outer side of the axial line, and is fixed to the outer protector, with a gap between the distal end opening and the distal end opening. The inner protector has a tip flow hole formed in the tip portion of the surrounding portion that communicates between the inside of the surrounding portion and a portion on the tip side of the surrounding portion. The rectifying member is a shielding portion located on the distal end side of the inner protector, and the shielding member projection region in which the rectifying member is projected on the proximal end side in the axial direction includes the rectifying member. A plurality of bridge portions that are arranged apart from each other in the circumferential direction of the axis and extend from the shielding portion toward the outer protector, and a shielding portion having a configuration in which the surrounding portion of the inner protector is positioned. And a plate-like plate-like portion arranged along the inner circumferential surface or outer circumferential surface of the outer protector, which is connected to each bridge portion, and the plate-like portion extends in the circumferential direction of the axis. A welded part that is welded to the outer protector and the plate-like part, and includes a plurality of welded parts welded in the thickness direction of the outer protector and the plate-like part. At least one of the plate-like portions of the member and the bridge portion and the shielding portion of the rectifying member constitute a flow passage through which the liquid flows in the axial direction through the tip opening and inside and outside of the outer protector. This is a liquid state detection sensor.

The liquid state detection sensor of the present invention includes a rectifying member that is fixed to the outer protector and closes a part of the front end opening of the outer protector. In addition, at least one of the outer protector and the plate-like portion of the rectifying member, and the bridge portion and the shielding portion of the rectifying member constitute a flow passage through which liquid flows in the axial direction through the front end opening. Become. Therefore, the liquid exchange between the periphery of the detection part of the liquid concentration detection element and the outside of the liquid state detection sensor (outer protector) becomes possible. On the other hand, due to the presence of the flow regulating member, it is possible to suppress the occurrence of intense liquid movement around the detection unit.
In addition, the rectifying member has a plate-like plate-like portion that is connected to the bridge portion and is disposed along the inner peripheral surface or the outer peripheral surface of the distal end portion of the outer protector. And this plate-shaped part is a some welding part spaced apart in the circumferential direction of the axis line, and welds this plate-shaped part to an outer protector. That is, since the outer protector and the rectifying member are connected by welding, the liquid is less likely to swell and deteriorate. In addition, by providing a plurality of welded portions spaced in the circumferential direction, welding can be performed more easily than when annular welding is performed. Moreover, the welded portion welds the outer protector and the plate-like portion in the thickness direction. For this reason, compared with the case where the flat lid member is abutted against the front end surface of the outer protector described above and welded, the position of the welded portion that welds the outer protector and the plate-like portion is higher in the degree of freedom of positioning. It is easy and both can be reliably welded.

The liquid state detection sensor may be any sensor that detects at least the concentration of the specific component in the liquid, and includes the liquid temperature and the liquid level in addition to the concentration of the specific component. It is good also as a composite type sensor so that it can detect.
In addition, the liquid concentration detection element is an element configured to detect the concentration of a specific component of the liquid in contact with the liquid concentration detection element. For example, the liquid concentration detection element heats the liquid and changes the temperature (specific heat) of the liquid. The indirectly heated liquid concentration detecting element described in Patent Documents 1 and 2 is used. In addition, it consists of a heating resistor whose resistance value changes with temperature, and when this heating resistor is energized for a certain period of time while immersed in a liquid, the tendency of the heating resistor to rise with energization and the accompanying resistance value From the tendency of the change, there is a direct heat type element that detects the concentration of a specific component (for example, urea) of the liquid. Furthermore, the liquid concentration detecting element includes not only the concentration of a specific component in the liquid but also a device configured to detect the temperature of the liquid, the presence / absence of the liquid (whether or not it falls below the lower limit level), and the like. .

Further, the surrounding portion of the inner protector surrounds the detection portion with a gap from the detection portion at least from the peripheral direction of the axial line from the distal end side and the radial outside of the axial line. In addition, a distal end circulation hole is formed in the distal end portion of the surrounding portion so as to allow the liquid to flow between the inside of the surrounding portion and the distal end side portion from the surrounding portion.
Therefore, as the enclosure part of the inner protector, for example, the detection part of the liquid concentration detection element is enclosed only from the outside in the radial direction of the axis without surrounding from the tip side, and the entire inside of the tip part of the enclosure part is the tip. The thing which has made the circulation hole is mentioned. In addition, the detection part of the liquid concentration detection element is surrounded from the outside in the radial direction of the axis and from the tip side, and one or more tip flow holes are formed in a part of the tip part of the surrounding part. What is made is mentioned. In addition to the tip circulation hole, one or a plurality of circulation holes through which the liquid flows may be formed in a portion of the surrounding portion that surrounds the detection unit from the outside in the axial direction.

Among the rectifying members, the shielding part is positioned on the tip side from the inner protector, and the detection part of the liquid concentration detection element and the surrounding part of the inner protector are located in the shielding part projection region.
Therefore, the shielding portion may be disposed on the proximal end side in the axial direction from the distal end of the outer protector on the distal end side of the inner protector, that is, in the outer protector, or at the same position in the axial direction as the distal end of the outer protector. Furthermore, it may be arranged in the axial direction tip side from the tip of the outer protector, that is, outside the outer protector. However, considering the shielding action of the liquid flow, it is preferable that the shielding portion is at the same position as the distal end of the outer protector in the axial direction or at the proximal end side in the axial direction.

On the other hand, among the rectifying members, the plurality of bridge portions are arranged apart from each other in the circumferential direction of the axis. The bridge portions may be non-uniformly arranged in the circumferential direction of the axis, but it is preferable to arrange them uniformly (equally spaced, equiangular, etc.) from the viewpoint of holding the shielding portion that receives the pressure of the liquid flow. . Moreover, it is preferable that the form of each bridge part is also the same form. This is because when the pressure due to the liquid flow is applied, the stress is less likely to be uneven.
In addition, the bridge portion has a shape of the shielding portion and the plate-like portion, and a positional relationship in the axial direction thereof, for example, a position such as whether or not the plate-like portion is located on the front end side in the axial direction as compared with the shielding portion. What is necessary is just to select the form according to a relationship. Alternatively, it may be bent in the axial direction, such as a U-shape or V-shape that extends to the distal end side or the proximal end side in the axial direction and then reverses and extends to the opposite side.

Of the rectifying members, the plate-like portion is plate-like, is connected to each of the bridge portions, and is disposed along the inner peripheral surface or outer peripheral surface of the outer protector. Therefore, a plurality of plate-like portions may exist corresponding to the plurality of bridge portions, respectively, or one plate-like portion and a plurality of bridge portions may be connected. Furthermore, the rectifying member may be provided with a single plate-shaped portion, for example, in a ring shape, and any bridge portion may be connected to the single plate-shaped portion.
The rectifying member may also be used as a member having another function, such as a positioning member for positioning the inner protector, the liquid concentration detection element, a member for holding the same, or the like.

  The flow path through which the liquid flows axially in and out of the outer protector through the tip opening is constituted by at least one of the outer protector and the plate-like portion of the rectifying member, and the bridge portion and the shielding portion of the rectifying member. The ease of liquid flow in the flow passage can be adjusted by appropriately selecting the form of the outer protector, the plate-like portion of the rectifying member, the bridge portion, and the shielding portion. Therefore, for example, when these are viewed in the axial direction, the peripheral edge of the shielding portion located between the bridge portions is projected radially outward to form a fin-like portion, and the radial dimension of the flow passage is reduced (narrow). The form which was made is mentioned. Moreover, the form which enlarged the circumferential width dimension of the fin-shaped part and made the circumferential direction dimension of the flow path between fin-shaped parts small (narrow) is also mentioned. Further, in such a configuration, the bridge portion is bent in the axial direction, and a part of the bridge portion is positioned closer to the proximal end side in the axial direction than the shielding portion, so that the liquid flow is also prevented in the bridge portion. The form which adjusted the ease of distribution is also mentioned.

  Further, in the above-described liquid state detection sensor, each of the bridge portions of the rectifying member extends from a bridge extension portion of the periphery of the shielding portion, and the shielding portion of the rectifying member is A fin-like portion that is located on the radially inner side of the outer protector, is located between the bridge portions in the circumferential direction of the axis, and protrudes toward the radially outer side of the axis, and is radially outer The radial gap between the outer protector and the plate-like part located closer to each other is larger than the radial gap between the bridge extension part and the outer protector and the plate-like part closer to each other. The bridge portion includes a fin-like portion as a small form, and at least a part of the bridge portion is located radially outside the bridge extension portion of the shielding portion and closer to the base end side than the shielding portion. liquid May the state detection sensor.

In the liquid state detection sensor of the present invention, the shielding portion includes the fin-shaped portion having the above-described form, and the bridge portion has the above-described form.
Therefore, consider a case where a liquid flow toward the proximal end in the axial direction occurs. In this case, the progress of part of the liquid flow can be stopped by the shielding part. On the other hand, the other part of the liquid flow tries to flow into the outer protector through the opening formed by at least one of the outer protector and the plate-like portion of the rectifying member and the bridge portion and the shielding portion of the rectifying member. To do.
However, in the liquid state detection sensor according to the present invention, since the shielding part includes the fin-like part, the radial gap between the bridge parts, that is, between the fin-like part and the outer protector or the plate-like part is narrow and passes therethrough. It is difficult to flow in. In other words, the liquid flow is also limited here.
On the other hand, the radial gap between the bridge extension part and the outer protector or plate-like part located radially outside of the peripheral edge of the shielding part is the radial direction between the fin-like part and the outer protector or plate-like part. It is relatively wider than the gap. For this reason, the liquid flow tends to flow into the outer protector through this portion (the radially outer portion of the bridge extension portion). Therefore, the direction of the liquid flow is changed here.
In addition, since at least a part of the bridge portion is located on the proximal end side of the shielding portion on the radially outer side of the bridge extension portion, it flows into the outer protector from the radially outer portion of the bridge extension portion. The liquid flow collides with this part of the bridge portion and is prevented from traveling toward the proximal side in the axial direction. Therefore, the direction of the liquid flow can be changed here.
Thus, in the liquid state detection sensor of the present invention, the fin-like portion and the bridge portion of the rectifying member are configured in the above-described form, so that the liquid flow flowing into the outer protector from the outside through the flow path is limited, The direction of travel is changed to reduce the momentum of the liquid flow. Thus, the liquid around the detection part of the liquid concentration detection element can be exchanged with the outside of the liquid state detection sensor, but the liquid around the detection part of the liquid concentration detection element is caused by the liquid flow flowing in from the flow path. , It is possible to further suppress the violent movement. In this manner, this liquid state detection sensor can more appropriately detect the liquid state such as concentration and temperature.

Furthermore, in any of the above liquid state detection sensors, the liquid concentration detection element is disposed on the axis, and the surrounding portion of the inner protector extends along the axis, and the axis The radial dimension of the axial line from the peripheral edge of the surrounding portion to the portion located on the radially outermost side of the axial line is r, and from the axial line to the peripheral edge of the shielding portion Assuming that the radial dimension to the portion located on the radially innermost side of the axial line is R and the shortest axial distance between the surrounding portion and the shielding portion is H, the following formula (1) is satisfied. A liquid state detection sensor is preferable.
H / 2 ≦ R−r ≦ 2H (1)

The radial dimension r (hereinafter also referred to as the first radius r) from the axis to the portion located on the radially outermost side of the axial line in the peripheral edge of the front end circulation hole of the surrounding part, and the peripheral edge of the shielding part from the axis Among them, a radial dimension R (hereinafter also referred to as a second radius R) to a portion located on the innermost radial direction of the axis, and an axial minimum distance H (hereinafter referred to as an enclosure-shield) between the enclosure and the shield. The relationship with the inter-part distance H is also considered.
When the difference (R−r) between the second radius R and the first radius r is less than half (H / 2) of the surrounding-shielding distance H (H / 2), the shielding part of the inner protector and the rectifying member are shielded. The part is too close. For this reason, it is difficult to exchange the liquid between the inside of the surrounding portion and the outside of the liquid state detection sensor (outside of the outer protector) through the front end flow hole of the surrounding portion. Thus, it becomes difficult for the liquid state detection sensor to appropriately detect changes in the concentration and temperature of the liquid.
On the other hand, when the difference (R−r) between the second radius R and the first radius r exceeds twice (2H) the distance H between the enclosure and the shield, the shield between the envelope of the inner protector and the rectifying member is shielded. The part is too far away. For this reason, the shielding effect of the liquid flow toward the proximal side in the axial direction by the shielding portion is not sufficient, and such a liquid flow enters the enclosure portion through the tip circulation hole, and surrounds the detection portion of the liquid concentration detection element in the enclosure portion. The liquid tends to move violently, and there is a risk that an error will increase in the detection of the concentration of the liquid in the detection part of the liquid concentration detection element.

  On the other hand, in the liquid state detection sensor of this invention, it is set as the relationship which satisfy | fills Formula (1). As described above, since the difference between the second radius R and the first radius r (R−r) and the distance H between the enclosure and the shield are in an appropriate relationship, the inside of the enclosure is passed through the tip circulation hole of the inner protector. Liquid exchange with the outside of the liquid state detection sensor (outside of the outer protector) can be appropriately performed. On the other hand, the concentration by the liquid state detection sensor is obtained by sufficiently obtaining the shielding effect of the liquid flow toward the proximal side in the axial direction by the shielding portion, and suppressing the movement of the liquid around the detection portion of the liquid concentration detection element in the surrounding portion. It is possible to appropriately detect the state such as temperature.

  Furthermore, in the liquid state detection sensor according to any one of the above, the rectifying member includes a positioning portion that engages with a tip of the outer protector and positions the rectifying member in the axial direction. It may be a liquid state detection sensor.

  In the liquid state detection sensor according to the present invention, since the rectifying member is provided with the positioning portion, the positioning of the rectifying member in the axial direction with respect to the outer protector can be easily performed by engaging the positioning portion with the tip of the outer protector. And a liquid state detection sensor in which the rectifying member is welded to an appropriate position of the outer protector.

  Note that the positioning portion of the rectifying member can be appropriately selected as long as the rectifying member can be positioned in the axial direction of the rectifying member. However, if the positioning part is formed at a position connected to the bridge part or the plate-like part, such as a portion between the bridge part and the plate-like part or the tip part of the plate-like part, the positioning part is independent of the bridge part, the plate-like part, etc. It is easier to form compared to the case of forming only. In addition, since the positioning can be performed at a position close to the plate-like portion to be welded by the welded portion, there is an advantage that the plate-like portion can be appropriately positioned.

  Furthermore, in the liquid state detection sensor according to any one of the above, the rectifying member may be a liquid state detection sensor formed integrally by press forming a metal plate.

  In the liquid state detection sensor of the present invention, since the rectifying member is integrally formed by press molding of a metal plate, the cost is low. In addition, since the shielding part, bridge part, plate-like part, and further positioning part are integrally formed with each other, it is possible to make a rectifying member having a structure in which these are properly connected to each other without welding, etc. Is also expensive.

  In addition, examples of the press forming technique for forming the rectifying member include punching by bending, bending, drawing, and the like, and not only these but also a plurality of techniques may be applied in combination.

  Further, in the liquid state detection sensor according to any one of the above, the outer protector may be configured such that the detection portion of the liquid concentration detection element is radially inward of the axially proximal end portion of the liquid concentration detection element. A liquid state detection sensor comprising an inner electrode body extending in the axial direction and capable of measuring a liquid level of the liquid interposed between the inner electrode body and the outer protector by means of a capacitance generated between the inner electrode body and the outer protector; Good.

  The liquid state detection sensor of the present invention can detect the liquid concentration and also the liquid level by using the liquid concentration detection element. In addition, since the outer protector is also used as one electrode for measuring the liquid level, it can be an integrated sensor that can detect the liquid concentration and the liquid level, but can be a simple and inexpensive sensor.

(Embodiment 1)
1st Embodiment of the liquid state detection sensor which actualized this invention is described with reference to FIGS.

The liquid state detection sensor 1 according to the first embodiment is, for example, in an exhaust gas purification device that reduces nitrogen oxide (NOx) contained in an exhaust gas of an automobile equipped with a diesel engine or the like with an aqueous urea solution to make it harmless. The apparatus is used for a device that detects the concentration of the aqueous urea solution LQ stored in the storage tank and the liquid level LQH of the aqueous urea solution LQ.
The liquid state detection sensor 1 (hereinafter, also simply referred to as sensor 1) includes a base 2 and a sensor unit 3 extending downward from the base 2 in FIG. The liquid state detection sensor 1 has a base 2 attached around an opening of a storage tank (not shown) that stores a urea aqueous solution LQ indicated by a broken line, and a posture in which the sensor unit 3 extends in the direction of gravity. It is used by dipping in an aqueous urea solution LQ.
Therefore, in the present specification, in the description of the sensor 1 and each component, in the direction (axial direction) along the axis AX shown in FIG. 1, the upper side in FIG. To do.
In addition, when specifying or describing a part related to the posture of the sensor 1 or the direction of gravity, the direction in which the sensor unit 3 extends with respect to the base 2 (the direction along the axis AX shown in FIG. 1 (axis direction)) The description is based on the posture with the direction of gravity as the direction of gravity. Therefore, for example, the sensor unit 3 positioned on the tip side with respect to the base 2 is set to the lower side (downward), and conversely, the base 2 is in the direction opposite to the direction of gravity, that is, higher than the sensor unit 3. The explanation will be made on the side (upper side).

  Of the liquid state detection sensor 1, the base 2 includes a mounting flange portion 21, a lid body 25, a wiring board 22 surrounded by them, an external connection cable 24, and a bush 23 that holds this. The sensor unit 3 includes a double cylindrical liquid level sensor unit 4 and a liquid concentration sensor unit 5 which is positioned on the distal end side and positioned on the lower level side during use.

  First, the base 2 will be described. The mounting flange 21 is made of metal, and is used as a pedestal for mounting the liquid state detection sensor 1 on the periphery of the opening of a storage tank (not shown). The mounting flange 21 is provided with a bolt insertion hole (not shown) so that the liquid state detection sensor 1 (base portion 2) can be fixed to the storage tank with a bolt.

On the other hand, the wiring board 22 indicated by a broken line in FIG. 1 is disposed at a position higher than the mounting flange 21. The wiring board 22 is formed with a control circuit (not shown) including a CPU, an electric circuit, and the like, and is electrically connected to the liquid level sensor unit 4 and the liquid concentration sensor unit 5 as well as an external connection cable. 24 can be connected to an external electric circuit. Further, the wiring board 22 is covered with a lid body 25 attached to the attachment flange portion 21, and is protected liquid-tightly.
The control circuit formed on the wiring board 22 energizes the concentration sensor element 51 shown in FIG. Based on the output signal corresponding to the resistance value of the internal heater wiring 518, specifically, based on a potential difference (voltage value) generated at both ends of the internal heater wiring 518 by passing a predetermined current through the concentration sensor element 51. Then, the concentration of the urea aqueous solution LQ is detected.
The measurement of the liquid level LQH of the urea aqueous solution LQ will be described later.

Next, the sensor unit 3 will be described. As described above, the sensor unit 3 includes the liquid level sensor unit 4 and the liquid concentration sensor unit 5. Among these, first, the liquid level sensor unit 4 will be described, and then the liquid concentration sensor unit 5 will be described.
As shown in FIG. 1, the liquid level sensor unit 4 is disposed inside a cylindrical outer cylinder 41 extending in a direction (axial direction) AXD along the axis AX, and is coaxial with the outer cylinder 41. Includes an inner cylinder 42 having a relatively small diameter and a cylindrical shape. The inner peripheral surface of the outer cylinder 41 and the outer peripheral surface of the inner cylinder 42 are separated from each other at a predetermined interval.

Out of these, the outer cylinder 41 is made of metal and serves as one electrode for detecting the liquid level. Further, the outer cylinder 41 has a narrow oval slit 41S with the axial direction AXD as a longitudinal direction, and is connected to the outside between the inner cylinder 42 and urea as shown by a broken line. The aqueous solution LQ can be accommodated. In addition, among the outer cylinder 41, the distal end (lower end in FIG. 1) 41T opens to form a distal end opening OP, while the proximal end (upper end in the figure) 41B is fixed to the mounting flange 21 by welding or the like. .
In the sensor 1 of the present embodiment, the outer cylinder 41 is welded to the mounting flange 21. Further, the mounting flange 21 is connected to a ground potential in a control circuit (not shown) formed on the wiring board 22. As a result, the outer cylinder 41 is set to the ground potential.

  Further, a rubber bush 56 described later is interposed between the holding portion 412 located slightly on the proximal side of the distal end 41T in the outer cylinder 41 and the distal end portion 421 located on the distal side of the inner cylinder 42. Yes. The holding portion 412 of the outer cylinder 41 is engaged with an engaging protrusion 562 formed on the outer periphery of the rubber bush 56, and a holding hole 41H for holding the rubber bush 56 (liquid concentration sensor portion 5). However, it is formed at a plurality of predetermined positions in the circumferential direction (three places in the present embodiment) (see FIGS. 1 to 3). Furthermore, a flow hole 41R for flowing the urea aqueous solution LQ to and from the inside of the outer cylinder 41 is formed on the tip side (lower side in the drawing) from the holding hole 41H.

  The inner cylinder 42 is also made of metal, and is electrically insulated from the outer cylinder 41 as the other electrode for measuring the liquid level. And are electrically connected. The outer peripheral surface 42G of the inner cylinder 42 is covered with an insulating coating 43 made of, for example, fluorine resin such as PTFE, PFA, ETFE, epoxy resin, polyimide resin, or the like. Even if the urea aqueous solution (liquid to be measured) LQ is interposed between the outer cylinder 41 and the outer cylinder 41, the outer cylinder 41 is electrically insulated.

In order to detect the liquid level LQH of the urea aqueous solution LQ by the liquid level sensor unit 4, the liquid level sensor unit 4 is immersed in the urea aqueous solution LQ, and the urea aqueous solution LQ is connected to the outer cylinder 41 through the slit 41S. It flows between the inner cylinder 42 (insulating coating 43).
Then, in this liquid level sensor unit 4, between the outer cylinder 41 and the inner cylinder 42, a portion where the urea aqueous solution LQ exists and a portion where the urea aqueous solution LQ does not exist can be formed according to the liquid level LQH. The capacitance of the capacitor formed between the cylinder 42 changes according to the liquid level. Therefore, when an AC voltage is applied between the outer cylinder 41 and the inner cylinder 42 by the control circuit of the wiring board 22, a current corresponding to the magnitude of this capacitance flows, so knowing the magnitude of the current The liquid level LQH of the urea aqueous solution LQ can be detected.

Next, the liquid concentration sensor unit 5 will be described.
The liquid concentration sensor unit 5 is disposed on the front end side (downward in FIG. 1) of the liquid level sensor unit 4, and includes a concentration sensor element 51, a holder member 55, an inner protector 58, a rubber bush 56, and the like ( 2 to 4).
Among these, the density sensor element 51 (see FIG. 5) is held by the holder member 55 in a form in which the tip portion thereof protrudes. The density sensor element 51 is electrically connected to a control circuit formed on the wiring board 22 via a connection terminal 52 and a connection cable 53 that are fixed to the density sensor element 51 by brazing. On the other hand, the holder member 55 is fixedly held on the holding portion 412 of the outer cylinder 41 by a rubber bush 56 interposed between the holder member 55 and the outer cylinder 41 surrounding the holder member 55. Further, the inner protector 58 is engaged with and held by the tip end portion (small diameter portion 553) of the holder member 55 so as to surround the tip end portion 511 of the density sensor element 51 protruding from the holder member 55. .

  First, the concentration sensor element 51 (see FIG. 5) in the liquid concentration sensor unit 5 will be described. This concentration sensor element 51 has a rectangular plate shape in plan view, and has two plate-like ceramic layers 519 (519A, 519B) made of alumina ceramics, and an internal liquid-tightly disposed therebetween. Wiring 516 is provided. The internal wiring 516 includes a pair of wide internal lead wirings 517 and an internal heater wiring (heating resistor) 518 disposed between them and folded in a bellows shape.

The concentration sensor element 51 includes a distal end portion 511 protruding from the holder member 55, an insertion portion 512 inserted through the holder member 55 adjacent to the proximal end side of the distal end portion 511, and a proximal end of the insertion portion 512. The resin holding portion 513 located on the side and the pair of connection terminals 52 are divided into base end portions 514 formed by brazing connection. An internal heater wiring 518 is disposed inside the distal end portion 511. Therefore, in the present embodiment, the tip portion 511 includes a temperature rise detection unit 510 that raises the temperature by energization and detects the urea concentration of the urea aqueous solution LQ.
The density sensor element 51 has a main surface 511A composed of the ceramic layer 519A and a back surface 511B composed of the ceramic layer 519B in parallel with the main surface 511A. Further, regarding the temperature increase detection unit 510, the temperature increase detection unit 510 includes a temperature increase unit main surface 511AS included in the main surface 511A and a temperature increase unit back surface 511BS included in the back surface 511B.

  The connection terminal 52 is formed by bending a metal plate having a predetermined shape into a U shape. Among the connection terminals 52, the distal end portion 521 has a shape extending toward the distal end side (downward in FIG. 5), and is connected to a pad (not shown) formed at the proximal end portion 514 of the density sensor element 51. The density sensor element 51 is fixedly connected by attaching. Thus, the connection terminal 52 (tip portion 521) is connected to the internal lead wiring 517 via a via conductor (not shown) that penetrates the one ceramic layer 519A. For this reason, when a voltage is applied between the pair of connection terminals 52, a current flows through the internal lead wiring 517, and the internal heater wiring 518 mainly generates heat. The resistance value of the internal heater wiring 518 changes according to its own temperature.

  On the other hand, the core wire 533 of the lead wire 532 of the connection cable 53 is electrically and mechanically connected to the proximal end portion 522 of the connection terminal 52 by caulking. As shown in FIGS. 1, 3, and 4, the connection cable 53 is inserted into the inner cylinder 42 and extends to the proximal end side, and is connected to the wiring board 22 (control circuit).

Next, the holder member 55 (see FIG. 7) will be described. The holder member 55 is entirely made of an insulating resin material. The outer shape of the holder member 55 is a large-diameter portion 551 having a relatively large cylindrical shape, a small-diameter portion 553 having a cylindrical shape smaller than the large-diameter portion 551, and the large-diameter portion 551 and the small-diameter portion. An intermediate taper portion 552 that is positioned between 553 and the outer peripheral surface is a tapered surface (conical frustum surface), and is positioned on the tip side (downward in FIG. 7) from the small diameter portion 553, and the outer peripheral surface is a tapered surface (conical surface). A front end taper portion 554.
Moreover, this holder member 55 is a hollow member which has the holder through-hole 55H which penetrates self in the axial direction AXD, as shown in FIG. 3, FIG. The holder through hole 55H is a three-stage circular hole portion of the inner cylinder holding hole 55H1, the second step hole 55H2, and the third step hole 55H3, which gradually becomes smaller in diameter from the base end side (upward in the drawing). And a substantially square hole-shaped element holding hole 55H4 located on the most distal side (downward in the figure).

As shown in FIGS. 3 and 4, the holder member 55 holds the concentration sensor element 51. Specifically, the insertion portion 512 of the concentration sensor element 51 is inserted into the element holding hole 55H4 of the holder member 55, and the resin holding portion 513 of the concentration sensor element 51 arranged in the third step hole 55H3 is the third holding hole 55H4. It is fixed by a sealing resin 59 filled in the step hole 55H3. The gap between the concentration sensor element 51 and the holder member 55 is liquid-tightly sealed by the sealing resin 59.
As a result, in the concentration sensor element 51, the tip end portion 511 in which the internal heater wiring 518 is disposed protrudes from the element holding hole 55H4 of the holder member 55 to the tip end side (downward in FIG. 1). Be placed.

Further, as shown in FIG. 3, the holder member 55 holds the tip 421 of the inner cylinder 42 inside the inner cylinder holding hole 55H1 of the holder through hole 55H. The stepped inner cylinder contact surface 55D located between the two-step hole 55H2 contacts the tip 422 of the inner cylinder 42 to position the inner cylinder 42 and the holder member 55 in the axial direction.
Two O-ring insertion grooves 55G1 and 55G2 are recessed in the inner cylinder holding hole 55H1 of the holder through-hole 55H, and the holder member 55 and the inner cylinder 42 are formed by O-rings 571 and 572 disposed inside these. The space between (insulating coating 43) is sealed in a liquid-tight manner, and the inner cylinder 42 is held.

  Further, since the holder member 55 holding the concentration sensor element 51 and the inner cylinder 42 are connected as described above, most of the proximal end portion 514 of the concentration sensor element 51 and the entire connection terminal 52 are connected. Is disposed in the inner cylinder 42. The concentration sensor element 51 and the connection terminal 52 are elastically formed in the inner cylinder 42 while insulating the density sensor element 51 and the connection terminal 52 and the inner cylinder 42 in the tip portion 421 of the inner cylinder 42. A separator 54 made of an insulating rubber-like elastic resin is disposed.

Next, the inner protector 58 in the liquid concentration sensor unit 5 will be described.
As shown in FIGS. 3, 4, and 6, the inner protector 58 has a bottomed cylindrical shape including a cylindrical side portion 582 and a distal end portion 583 that closes the distal end side of the side portion 582. As shown in FIG. 7, when the inner protector 58 is put on the temperature rise detection unit 510 of the concentration sensor element 51 and engaged with the holder member 55, the side protector 58 of the inner protector 58 is The portion excluding a part on the base end side and the distal end portion 583 form an enveloping portion 581 that encloses the temperature rise detection portion 510 of the concentration sensor element 51 (see FIG. 6D).

In the side part 582, in order to allow the urea aqueous solution LQ to flow inside and outside of the inner protector 58, three circular liquid circulation holes 58H1, 58H2, 58H3, and a circular hole part 58H41 and the front end side thereof are extended. Keyhole-shaped liquid circulation holes 58H4 formed of the long slit portions 58H42 are uniformly arranged in the circumferential direction.
In addition, the inside and outside of the inner protector 58 are also communicated with the distal end portion 583, specifically, between the enclosed portion inner region EH surrounded by the enclosed portion 582 and the distal end side region FH on the distal end side of the inner protector 58. In order to allow the aqueous urea solution LQ to flow, one circular tip flow hole 58H6 is formed at the center thereof.

In addition, of the side portion 582 of the inner protector 58, in the vicinity of the base end (near the upper end in FIGS. 6A and 6B), a U-shaped notch is formed and bent to the inside. Four 584 are equally formed around the circumferential direction.
As shown in FIG. 7, the locking tongue 584 of the inner protector 58 is locked in the protector locking recess 55G3 formed on the outer periphery of the small diameter portion 553 of the holder member 55. Thereby, the surrounding portion 581 of the inner protector 58 is disposed so as to surround the temperature rise detecting portion 510 of the concentration sensor element 51.

  At this time, as shown in FIG. 7, in the inner protector 58, all of the liquid circulation holes 58H1 to 58H4 are formed on the main surface 511A and the back surface 511B of the tip end portion 511 of the concentration sensor element 51. Of these, the holder member 55 is engaged so as to be disposed at a position that does not face the temperature raising portion main surface 511AS and the temperature raising portion back surface 511BS. Accordingly, the liquid flow that has entered from the liquid circulation hole 58H1 or the like does not travel so as to collide from the front with the temperature riser main surface 511AS or the temperature riser rear surface 511BS of the temperature rise detection unit 510. The influence that the temperature rise of the temperature rise detection unit 510 is hindered by the flow can be reduced, and the urea concentration and the like of the urea aqueous solution LQ can be more accurately detected.

Further, in this way, the holder member 55 holding the concentration sensor element 51 and the inner protector 58 is held by an insulating rubber bush 56 having a holder holding hole 56H adapted to the outer peripheral surface thereof.
As shown in FIGS. 2 to 4, the rubber bush 56 is formed with a cylindrical bush main body 561 having the above-mentioned holder holding hole 56 </ b> H formed at the center thereof and having an outer diameter that can be fitted to the outer cylinder 41. The bush body 561 has locking projections 562 that are equally disposed at three locations on the outer periphery of the bush body 561 and project radially outward from the bush body 561. The holder holding hole 56 </ b> H of the bush main body 561 is in a shape capable of being in close contact with the holder member 55 and the inner protector 58 and holding them.

  The rubber bush 56 is held by the outer cylinder 41 by inserting and locking the locking projections 562 into the holding holes 41H of the outer cylinder 41. Thus, the holder member 55 that holds the concentration sensor element 51 and the inner protector 58 is held by the rubber bushing 56, and the rubber bushing 56 is held by the outer cylinder 41, so that the entire liquid concentration sensor unit 5 is made the outer cylinder 41. Are held between the holding portion 412 and the tip portion 421 of the inner cylinder 42.

  Further, a number of outer peripheral slits 561G extending in the axial direction (vertical direction in FIG. 2) are formed in the outer peripheral surface of the bush main body 561 between the locking projections 562. As shown in FIGS. 3 and 4, the outer circumferential slit 561G is fitted between the bush body 561 and the outer cylinder 41 in the axial direction (up and down in the figure) by fitting the rubber bush 56 into the outer cylinder 41. Direction) A flow passage that allows the aqueous urea solution LQ to flow and remove bubbles is formed in AXD.

  Further, a positioning member 60 shown in FIG. 8 is fitted into the outer cylinder 41 on the tip side (lower side in the drawing) from the rubber bush 56. The positioning member 60 includes a positioning plate portion 601 having an outer diameter substantially equal to the inner diameter of the outer cylinder 41, a flat plate ring shape having an insertion hole 601H at the center, and a direction perpendicular to the periphery of the positioning plate portion 601. And three leg portions 602 extending in the axial direction AXD. The ends of the leg portions 602 are bent outward in the radial direction to form engagement claw portions 602K. The three leg portions 602 of the positioning member 60 are arranged equally (an angle shifted by 120 °) in the circumferential direction of the positioning plate portion 601 (the circumferential direction AXP of the axis AX).

  In the sensor 1 of the present embodiment, as shown in FIGS. 3 and 4, the positioning member 60 is in a state in which the positioning plate portion 601 is inserted into the outer cylinder 41, and the engaging claw portion 602 </ b> K is in the outer cylinder 41. Of the plate-like leg portions 602 arranged along the inner peripheral surface 41N of the outer cylinder 41 in a state of being engaged with the tip 41T, spot welding is performed on the outer cylinder 41 by a welding portion 602W near the tip. Further, the positioning plate 601 is in a state in which the inner protector 58 and the distal end portion 511 of the density sensor element 51 are inserted into the insertion hole 601H and contacted with the flat distal end side surface 56S located at the distal end of the rubber bush 56. Yes. Since the dimension of the leg portion 602 in the axial direction (vertical direction in the drawing) is determined in advance, the positioning of the rubber bush 56 and thus the concentration sensor element 51 in the axial direction can be performed accurately.

Further, a rectifying member 61 shown in FIG. 9 is fitted into the holding portion 412 of the outer cylinder 41 on the tip side of the positioning member 60. The straightening member 61 includes a disc-shaped shielding portion 611 having an outer diameter smaller than the inner diameter of the outer cylinder 41, and a peripheral portion 611P of the shielding portion 611, from the bridge extending portion 611PB in the radial direction of the axis AX. It has three bridge portions 612 that extend to the base end side AXD2 (upward) in the axial direction AXD, that is, on the outer side AXR1, that is, obliquely and reach the distal end portion 411 of the outer cylinder 41. Further, at the end of the bridge portion 612, a curved plate-like plate-like portion 613 that is inverted along the distal end side AXD1 (downward) and disposed along the inner peripheral surface 41N of the distal end portion 411 of the outer cylinder 41 is provided. Is provided. The tip of the plate-like portion 613 is bent toward the radially outer side AXR1 to form an engaging claw portion 614. The three bridge portions 612 and the plate-like portion 613 of the rectifying member 61 are arranged equally (angles shifted by 120 °) in the circumferential direction of the shielding portion 611 (the circumferential direction AXP of the axis AX).
The rectifying member 61 is formed by punching a metal plate, and the shielding portion 611, the bridge portion 612, the plate-like portion 613, and the engaging claw portion 614 are integrated.

In the sensor 1 of the present embodiment, as shown in FIGS. 3 and 4, the engaging claw portion 614 of the rectifying member 61 is further connected to the tip of the outer cylinder 41 in a state where the positioning member 60 is inserted and fixed in the outer cylinder 41. Each plate-like portion 613 is spot-welded to the distal end portion 411 of the outer cylinder 41 by a welded portion 613W of the plate-like portion 613 in a state where it is engaged with 41T and positioned in the axial direction AXD. For this reason, unlike the case of using an adhesive or the like, the rectifying member 61 is not likely to swell or deteriorate due to the urea aqueous solution LQ. it can.
In addition, the plate-like portion 613 of the rectifying member 61 and the tip portion 411 of the outer cylinder 41 are welded in the thickness direction (the radial direction AXR of the axis AX). For this reason, compared with the case where a flat cover member is abutted against the front end surface 41T of the outer cylinder 41 and welded, the position selection of the welded portion 613W is high, positioning is easy, and the plate shape of the rectifying member 61 is easy. The part 613 and the tip 411 of the outer cylinder 41 can be reliably welded.
Further, since the rectifying member 61 is provided with the engaging claw portion 614, the axial direction AX of the rectifying member 61 with respect to the outer cylinder 41 can be easily positioned by engaging the positioning portion 614 with the tip 41T of the outer cylinder 41. The sensor 1 can be obtained by welding the rectifying member 61 to an appropriate position of the outer cylinder 41.
The engaging claw portion 602K of the positioning member 60 and the engaging claw portion 614 of the rectifying member 61 are shifted from each other by 60 degrees in the circumferential direction AXP of the axis AX on the distal end surface 41T of the outer cylinder 41. Placed in position. Also, the welded portion 602W of the positioning member 60 and the welded portion 613W of the rectifying member 61 are welded to each other in the circumferential direction AXP of the axis AX by 60 degrees.

  As a result, the urea aqueous solution LQ flows in the axial direction AXD through the inside and outside of the outer cylinder 41 through the front end opening OP of the outer cylinder 41 and the plate-like portion 613, the bridge portion 612, and the shielding portion 611 of the rectifying member 61. A flow passage LL is formed. For this reason, it is possible to exchange the liquid between the temperature sensor 511 of the concentration sensor element 51 and the outside of the sensor 1 (outer cylinder 41).

On the other hand, the shielding portion 611 of the rectifying member 61 is in a state of closing a part (center portion) of the distal end opening OP of the outer cylinder 41. Specifically, as shown in FIG. 10, when the sensor 1 (outer cylinder 41) is viewed from the front end side in the axial direction (downward in FIGS. 3 and 4), the shielding portion 611 of the rectifying member 61 The front end portion 583 of the inner protector 58 is not visible. That is, as shown in FIG. 11, the temperature rise detection unit 510 of the concentration sensor element 51 and the inside of the shielding unit projection area PJ in which the shielding unit 611 of the rectifying member 61 is projected onto the base end side AXD2 in the axial direction AXD. The surrounding portion 581 of the protector 58 is located.
By doing so, when the urea aqueous solution LQ stored in the tank (not shown) is moved by vibration and a violent liquid flow is generated in the tank, in particular, the concentration sensor above the outer cylinder 41 from below. Even when a liquid flow toward the temperature rise detection unit 510 of the element 51 occurs, the shielding unit 611 prevents such liquid flow from proceeding. For this reason, such a liquid flow enters the inner protector 58 through the tip circulation hole 58H6 provided in the tip portion 583 of the inner protector 58, and the liquid violently surrounds the concentration sensor element 51 (temperature rise detection unit 511). It is possible to appropriately suppress a problem that the output of the concentration sensor element 51 varies due to movement.

Furthermore, in the sensor 1 of the present embodiment, as shown in FIG. 11, the tip circulation hole 58H6 of the inner protector 58 and the shielding part 611 of the rectifying member 61 have the following relationship.
That is, the density sensor element 51 is disposed on the axis AX, while the surrounding portion 581 of the inner protector 58 extends along the axis AX. The radial dimension from this axis AX to the outermost peripheral edge 58H6PO located on the outermost side in the radial direction AXR of the axial line AX among the peripheral edges of the distal end flow hole 58H6 of the surrounding portion 581 is a first radius r (specifically, 2.5 mm). Further, the dimension in the radial direction AXR from the axis AX to the innermost peripheral edge 611PI located on the innermost side in the radial direction AXR of the axis AX among the peripheral edges 611P of the shielding portion 611 of the rectifying member 61 is the second radius R (specifically Is 9.0 mm). Furthermore, when the shortest distance H (distance between the enclosure and the shielding portion) in the axial direction AXD between the surrounding portion 581 and the shielding portion 611 is set, the following formula (1) is satisfied.
The enclosure-shielding portion distance H is specifically set to 5.0 mm.
H / 2 ≦ R−r ≦ 2H (1)

When the difference (R−r) between the second radius R and the first radius r is less than half (H / 2) of the surrounding-shielding portion distance H, the surrounding portion 581 of the inner protector 58 and the rectifying member It can be said that 61 shielding parts 611 are too close. It is difficult to exchange liquid between the inside of the surrounding portion 581 (the surrounding portion inner region EH) and the outside of the sensor 1 (outside of the outer cylinder 41) through the front end flow hole 58H6 of the surrounding portion 581. For this reason, it becomes difficult for the sensor 1 to properly detect the urea concentration change and temperature change of the urea aqueous solution LQ.
On the other hand, when the difference (R−r) between the second radius R and the first radius r exceeds twice (2H) the distance H between the enclosure and the shield, the enclosure 581 of the inner protector 58 and the rectifying member It can be said that the 61 shielding portions 611 are too far apart. The shielding effect of the liquid flow toward the axial base end side AXD2 by the shielding part 611 is not sufficient, and such a liquid flow enters the enclosure part 581 through the distal end circulation hole 58H6, and the concentration sensor element 51 in the enclosure part 581. The aqueous urea solution LQ around the temperature rise detection unit 511 tends to move violently. For this reason, there is a possibility that an error may increase in the detection of the urea concentration or the like of the urea aqueous solution LQ in the temperature increase detection unit 511.

  On the other hand, in the sensor 1 according to the first embodiment, the relationship satisfies the above-described formula (1). In this way, through the appropriate relationship between the difference (R−r) between the second radius R and the first radius r and the surrounding-shielding portion distance H, through the tip circulation hole 58H6 of the inner protector 58, Liquid exchange between the inside of the surrounding part 581 and the outside of the sensor 1 (outside of the outer cylinder 41) can be appropriately performed. On the other hand, a sufficient shielding effect of the liquid flow toward the axial base end side AXD2 by the shielding portion 611 is obtained, and the movement of the urea aqueous solution LQ around the temperature increase detection portion 510 of the concentration sensor element 51 in the surrounding portion 581 is suppressed. Thus, it is possible to appropriately detect the state such as urea concentration and temperature by the sensor 1.

Next, the operation of the liquid concentration sensor unit 5 of the sensor 1 in detecting the urea concentration of the urea aqueous solution LQ will be described.
In the liquid state detection sensor 1 of the present embodiment, a current of a predetermined magnitude (for example, 300 mA) is supplied from the control circuit configured on the wiring substrate 22 for a predetermined time (for example, 700 ms). The flow is passed through the sensor element 51 to cause the internal heater wiring 518 to generate heat. Then, a voltage drop (detection voltage) corresponding to the magnitude of its own resistance value is generated in the internal heater wiring 518.
Therefore, the change in the detection voltage is detected by the control circuit to detect the urea concentration of the urea aqueous solution. Specifically, the detection voltage immediately after the start of energization of the concentration sensor element 51 and the detection voltage after a predetermined time has elapsed from the start of energization are measured. Then, the urea concentration of the urea aqueous solution corresponding to the change amount is obtained from the relationship between the urea concentration of the urea aqueous solution and the change amount obtained in advance using the change amount of the detection voltage during this period.
In the present embodiment, the urea concentration detection of the urea aqueous solution is performed using a CPU or the like in the control circuit, and the concentration information signal obtained by this control circuit passes through the external connection cable 24 to the external circuit ( For example, it is output to ECU. This external circuit determines whether or not the urea concentration of the aqueous urea solution is within an appropriate range based on the input concentration information signal. If the concentration is not within the appropriate concentration range, the driver is notified accordingly. Processing such as performing is performed as appropriate.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIGS.
The sensor 1001 according to the second embodiment is mainly different from the sensor 1 according to the first embodiment described above, except that the shape of the rectifying member is mainly different. The description will be omitted or simplified. Further, only parts different from those of the first embodiment are given different numbers.
Moreover, the same part as Embodiment 1 has the effect | action and effect similar to Embodiment 1. FIG.

In the sensor 1 of the first embodiment described above, the positioning member 60 (see FIG. 8) is disposed in the distal end portion 411 of the outer cylinder 41, and the rubber bush 56 and thus the concentration sensor element 51 are positioned in the axial direction. In addition to the positioning member 60, a rectifying member 61 (see FIG. 9) is provided on the tip side of the positioning member 60.
On the other hand, in the sensor 1001 of the second embodiment, in the liquid concentration sensor unit 1500 of the sensor unit 3, the rectifying member 1610 having the configuration shown in FIGS. 15 and 16 is placed in the distal end portion 411 of the outer cylinder 41. (See FIGS. 12 and 13).

  The rectifying member 1610 is a member that also serves as the positioning member 60 in addition to the rectifying member 61 in the first embodiment. That is, as shown in FIGS. 15 and 16, the rectifying member 1610 has a shielding portion 1611 having an outer diameter smaller than the inner diameter of the outer cylinder 41 and a substantially disk shape. Further, out of the peripheral edge 1611P of the shielding portion 1611, from the bridge extending portion 1611PB to the radially outer side AXR1 of the axis AX and the proximal side AXD2 (upward) of the axial direction AXD, that is, the outer side of the oblique proximal end, Three bridge portions 1612 extending toward the tip portion 411 of the cylinder 41 are provided. Further, at the tip of the bridge portion 1612, a curved plate-like plate-like portion that is reversed and extends toward the distal end side AXD1 (downward) and is disposed along the inner peripheral surface 41N of the distal end portion 411 of the outer cylinder 41. 1613 is provided.

Furthermore, the tip of the plate-like portion 1613 is bent toward the radially outer side AXR1 to form an engaging claw portion 1614. The three bridge portions 1612 and the plate-like portion 1613 of the rectifying member 1610 are arranged equally (equal angles shifted by 120 °) in the circumferential direction of the shielding portion 1611 (the circumferential direction AXP of the axis AX).
The rectifying member 1610 includes two members: a member that forms a shielding portion 1611 and a bridge portion 1612, a plate-like portion 1613, an engaging claw portion 1614, and a member that forms a positioning plate portion 1601 described later. . The bridge portion 1612 and the plate-like portion 1613 are welded by a weld connecting portion 1612W formed by spot welding, and two members including both are integrated to constitute a rectifying member 1610.

In the sensor 1001 of the second embodiment, as shown in FIG. 13, the engaging claw portion 1614 of the rectifying member 1610 is engaged with the tip 41T of the outer cylinder 41, and the axial direction AXD is positioned. Each plate-like portion 1613 is spot-welded to the distal end portion 411 of the outer cylinder 41 by a welded portion 1613W. Therefore, unlike the case of using an adhesive or the like, there is no risk of swelling or deterioration due to the aqueous urea solution LQ, and on the other hand, the rectifying member 1610 can be fixed to the outer cylinder 41 more easily than in the case of welding in an annular shape. .
Moreover, the plate-like portion 1613 of the rectifying member 1611 and the tip portion 411 of the outer cylinder 41 are welded in the thickness direction (the radial direction AXR of the axis AX). For this reason, compared with the case where a flat cover member is abutted against the front end surface 41T of the outer cylinder 41 and welded, the position selection of the welded portion 1613W is high, positioning is easy, and the plate shape of the rectifying member 1610 is easy. The portion 1613 and the tip 411 of the outer cylinder 41 can be reliably welded.

  The rectifying member 1610 is also provided with a positioning plate portion 1601 corresponding to the positioning plate portion 601 in the first embodiment. The positioning plate 1601 has a triangular shape with rounded corners in plan view, and has an insertion hole 1601H at the center (see FIG. 16B). In a state where the rectifying member 1610 is disposed in the distal end portion 411 of the outer cylinder 41, the positioning plate portion 1601 is inserted into the inner protector 58 and the distal end portion 511 of the concentration sensor element 51 through the insertion hole, like the positioning plate portion 601 in the first embodiment. It is inserted into 1601H and is in a state of being in contact with the flat front end side surface 56S located at the front end of the rubber bush 1560. As a result, the rubber bushing 1560 and thus the density sensor element 51 can be accurately positioned in the axial direction.

  Further, as shown in FIG. 17, the rubber bush 1560 in the second embodiment is slightly different in shape from the rubber bush 56 used in the first embodiment. Specifically, three oblique plane cutout portions 1563 are provided on the distal end side (downward in FIG. 17) of the bush main body 561. As a result, in combination with the positioning plate 1601 having a substantially triangular shape in plan view as described above, the bubbles BB contained in the liquid are removed from the flow holes of the outer cylinder 41 as shown in FIG. 41R can be easily discharged to the outside.

Now, the shielding part 1611 of the rectifying member 1610 is different in planar shape from the shielding part 611 (disk shape) of the first embodiment. That is, as shown in FIG. 16D, the shielding portion 1611 is located on the radially inner side AXR2 of the outer cylinder 41 (see FIG. 15). Further, the shielding portion 1611 is located between the bridge portions 1612 with respect to the circumferential direction AXP of the axis line AX in addition to the size and shape corresponding to the shielding portion 611 (disc shape) of the first embodiment. It has a fin-like portion 1611F projecting toward the radially outer side AXR1 of AX. As shown in FIG. 14, the fin-shaped portion 1611 </ b> F is in the radial direction with the outer cylinder 41 or the plate-shaped portion 1613 located on the radially outer side AXR <b> 1 (which is the outer cylinder 41 in the second embodiment). The gap (hereinafter referred to as the second gap D2) is a radial gap (hereinafter referred to as the plate-like portion 1613 in the second embodiment) between the bridge extension portion 1611PB and the outer cylinder 41 or the plate-like portion 1613. Smaller than the first gap D1).
On the other hand, as shown in FIGS. 15, 16 (a) and 16 (d), the bridge portion 1612 is positioned on the proximal side AXD 2 from the shield portion 1611 on the radial outer side AXR 1 of the bridge extension portion 1611 PB of the shield portion 1611. is doing.

  As a result, the aqueous urea solution LQ flows in the axial direction AXD inside and outside the outer cylinder 41 through the tip opening OP of the outer cylinder 41 through the outer cylinder 41 and the plate-like portion 1613, the bridge portion 1612, and the shielding portion 1611 of the rectifying member 1610. A flow passage LL is formed. For this reason, the liquid exchange between the periphery of the temperature rise detection unit 511 of the concentration sensor element 51 and the outside of the sensor 1001 (outer cylinder 41) becomes possible.

On the other hand, the shielding portion 1611 of the rectifying member 1610 closes a part (center portion) of the distal end opening OP of the outer cylinder 41. Specifically, as shown in FIG. 14, when the sensor 1001 (outer cylinder 41) is viewed from the front end side in the axial direction (downward in FIG. 13), the inner protector 58 is covered by the shielding portion 1611 of the rectifying member 1610. The distal end portion 583 is not visible. That is, the temperature rise detection unit 510 of the concentration sensor element 51 and the surrounding part 581 of the inner protector 58 are within the shielding part projection region PJ obtained by projecting the shielding part 1611 of the rectifying member 1610 onto the base end side AXD2 in the axial direction AXD. It is supposed to be positioned.
Thereby, the malfunction that the liquid moves vigorously around the concentration sensor element 51 (temperature rise detection unit 511) and the output of the concentration sensor element 51 fluctuates can be appropriately suppressed.

Furthermore, in the sensor 1001 of the second embodiment, the fin portion 1611F is included in the shielding portion 1611 and the bridge portion 1612 is in the above-described configuration. Therefore, the liquid flow is further suppressed as compared with the sensor 1 of the first embodiment. ing.
This will be specifically described. First, consider a case where a liquid flow toward the axial base end side AXD2 occurs. In this case, part of the liquid flow can be stopped by the shielding part 1611. On the other hand, the other part of the liquid flow passes through the opening portion constituted by at least one of the outer cylinder 41 and the plate-like portion 1613 of the rectifying member 1610, the bridge portion 1612 and the shielding portion 1611 of the rectifying member 1610, and is outside. An attempt is made to flow into the cylinder 41.
However, in the sensor 1001 of the second embodiment, since the shielding portion 1611 includes the fin-shaped portion 1611F, the second gap D2 is narrow between the bridge portions 1612, that is, it is difficult to flow in through the bridge portion 1612. Yes. In other words, the liquid flow is also limited here.

On the other hand, of the peripheral edge 1611P of the shielding portion 1611, the first gap D1 in the radially outer portion of the bridge extension portion 1611PB is relatively wider than the second gap D2. For this reason, the liquid flow tries to flow into the outer cylinder 41 through the portion of the bridge extending portion 1611PB on the radially outer side AXR1. Therefore, the direction of the liquid flow is changed here.
In addition, the bridge portion 1612 is located on the axially proximal end side AXD2 of the shielding portion 1611 on the radially outer side AXR1 of the bridge extension portion 1611PB. For this reason, the liquid flow that has flowed into the outer cylinder 41 from the radially outer side AXR1 of the bridge extension portion 1611PB hits the bridge portion 1612 and is prevented from proceeding to the axial base end side AXD2. Therefore, the direction of the liquid flow can be changed here.
As described above, in the sensor 1001 of the second embodiment, the fin-like portion 1611F and the bridge portion 1612 of the rectifying member 1610 are configured in the above-described form, so that the liquid flow that flows into the outer cylinder 41 from the outside through the flow passage LL. Limit the direction of movement or change the direction of travel to reduce the momentum of the liquid flow. Thus, while allowing the liquid to be exchanged between the temperature rise detection unit 510 of the concentration sensor element 51 and the outside of the sensor 1001, the temperature rise detection unit 510 of the concentration sensor element 51 is caused by the liquid flow flowing in from the flow path LL. It is possible to further suppress the violent movement of the liquid around the. In this way, the sensor 1001 according to the second embodiment can more appropriately detect the urea concentration of the urea aqueous solution LQ.

Further, as in the first embodiment, in the sensor 1001 of the second embodiment, as shown in FIGS. 13 and 14, the tip circulation hole 58 </ b> H <b> 6 of the inner protector 58 and the shielding portion 1611 of the rectifying member 1610 are related as follows. It is said.
That is, the density sensor element 51 is disposed on the axis AX, while the surrounding portion 581 of the inner protector 58 extends along the axis AX. The radial dimension from this axis AX to the outermost peripheral edge 58H6PO located on the outermost side in the radial direction AXR of the axial line AX among the peripheral edges of the distal end flow hole 58H6 of the surrounding portion 581 is a first radius r (specifically, 2.5 mm). Further, the dimension in the radial direction AXR from the axis AX to the innermost peripheral edge 1611PI located on the innermost side in the radial direction AXR of the axial line AX among the peripheral edges 1611P of the shielding portion 1611 of the rectifying member 1610 is the second radius R (specifically Is 9.0 mm). Furthermore, when the shortest distance H (distance between the enclosure and the shielding portion) in the axial direction AXD between the surrounding portion 581 and the shielding portion 1611 is set, the following formula (1) is satisfied.
The enclosure-shielding portion distance H is specifically set to 5.0 mm.
H / 2 ≦ R−r ≦ 2H (1)

  As described above, by setting the difference (R−r) and the enclosure-shielding distance H to an appropriate relationship, the inside of the enclosure 581 and the outside of the sensor 1001 (outside (outside) through the tip flow hole 58H6 of the inner protector 58 are obtained. Liquid exchange with the outside of the cylinder 41) can be performed appropriately. On the other hand, a sufficient shielding effect of the liquid flow toward the axial base end side AXD2 by the shielding portion 1611 is obtained, and the movement of the urea aqueous solution LQ around the temperature rising detection portion 510 of the concentration sensor element 51 in the surrounding portion 581 is suppressed. Thus, it is possible to appropriately detect the state such as urea concentration and temperature by the sensor 1001.

(Embodiment 3)
Next, a third embodiment of the present invention will be described with reference to FIGS.
The sensor 2001 according to the third embodiment is different from the sensor 1 according to the first embodiment described above only in the shape of the rectifying member. Therefore, the description will focus on the different parts, and the same parts as in the first embodiment will be described. Is omitted or simplified. Further, only parts different from those of the first embodiment are given different numbers.
Moreover, the same part as Embodiment 1 has the effect | action and effect similar to Embodiment 1. FIG.

In the above-described sensors 1 and 1001 of the first and second embodiments, the three bridge portions 612 and 1612 of the rectifying members 61 and 1610 are separately provided with plate-like portions 613 and 1613 (accordingly, a total of three pieces each). It was.
On the other hand, in the sensor 2001 of the third embodiment, in the liquid concentration sensor unit 2500, the rectifying member 2610 having the form shown in FIG. 19 is inserted and arranged in the distal end portion 411 of the outer cylinder 41 (FIG. 18). reference).

The rectifying member 2610 has an outer diameter smaller than the inner diameter of the outer cylinder 41, and is a ring-shaped side portion (plate-like portion) extending from the periphery to one side around the main body portion having a substantially disk shape in plan view. 2613).
That is, the rectifying member 2610 has three bridge portions 2612 extending in three directions in the planar direction from the shielding portion 2611 having a size and shape corresponding to the shielding portion 611 (disk shape) of the first embodiment. Further, at the tip of the bridge portion 2612, a plate-like portion 2613 that extends perpendicularly to the shielding portion 2611, curves to form a flat ring shape, and is disposed along the inner peripheral surface 41 N of the distal end portion 411 of the outer cylinder 41. Is provided. Between the circumferential direction AXP of the axis AX and the bridge portions 2612, three flow holes 2610H forming the flow passage LL are formed.

This rectifying member 2610 has a distal end 2613T of the plate-like portion 2613 substantially in the same position as the distal end 41T of the outer cylinder 41, and the shielding portion 2611 is located on the axial base end side AXD2 with respect to the plate-like portion 2613. It is arranged in the outer cylinder 41. Among them, the rectifying member 2610 is fixed to the outer cylinder 41 by welding in the thickness direction of itself and the outer cylinder 41 at the welding portion 2613W of the plate-like portion 2613. Therefore, unlike the case of using an adhesive or the like, there is no risk of swelling or deterioration due to the aqueous urea solution LQ, and on the other hand, the rectifying member 2610 can be fixed to the outer cylinder 41 more easily than in the case of annular welding. .
Moreover, the plate-like portion 2613 of the rectifying member 2610 and the tip portion 411 of the outer cylinder 41 are welded in the thickness direction (the radial direction AXR of the axis AX). For this reason, compared with the case where a flat lid member is abutted against the front end surface 41T of the outer cylinder 41 and welded, the position of the welded portion 2613W is higher in the degree of freedom of positioning, positioning is easy, and the plate shape of the rectifying member 2610 is The portion 2613 and the distal end portion 411 of the outer cylinder 41 can be reliably welded.

  Even in the sensor 2001 of the third embodiment provided with such a rectifying member 2610, the outer cylinder 41, the plate-like portion 2613 of the rectifying member 2610, the bridge portion 2612, and the shielding portion 2611, urea passes through the distal end opening OP of the outer cylinder 41. A flow path LL through which the aqueous solution LQ flows in the axial direction AXD inside and outside the outer cylinder 41 is configured. For this reason, it is possible to exchange the liquid between the periphery of the temperature rise detection unit 511 of the concentration sensor element 51 and the outside of the sensor 2001 (outer cylinder 41).

On the other hand, the shielding portion 2611 of the rectifying member 2610 is in a state of closing a part (center portion) of the distal end opening OP of the outer cylinder 41. Specifically, as shown in FIG. 18, when the sensor 2001 (outer cylinder 41) is viewed from the front end side in the axial direction (from the lower left to the upper right in the figure), the shielding portion 2611 of the rectifying member 2610 The front end portion 583 of the inner protector 58 is not visible. That is, the temperature rise detection unit 510 of the concentration sensor element 51 and the surrounding part 581 of the inner protector 58 are within the shielding part projection region PJ (not shown) in which the shielding part 2611 of the rectifying member 2610 is projected on the proximal side AXD2. It is supposed to be positioned.
Thereby, also in the third embodiment, it is possible to appropriately suppress the problem that the liquid moves vigorously around the concentration sensor element 51 (temperature rise detection unit 511) and the output of the concentration sensor element 51 fluctuates.
The rectifying member 2610 is integrally formed by press forming of a metal plate such as press punching or drawing.

(Modification 1)
Next, a modification of the third embodiment will be described with reference to FIGS.
The sensor 3001 according to the first modification uses a rectifying member that is substantially the same shape as the rectifying member 2610 used in the sensor 2001 of the third embodiment. However, in the third embodiment, the rectifying member 2610 is inserted and fixed in the outer cylinder 41, but the present modified embodiment is different in that the outer cylinder 41 is covered with the rectifying member.
Therefore, different parts will be mainly described, and the description of the same parts as those in the third embodiment will be omitted or simplified. Further, only parts different from those in the third embodiment are given different numbers.
Further, the same parts as in the first and third embodiments have the same actions and effects as in the first and third embodiments.

In the sensor 3001 of the first modification, the rectifying member 3610 (see FIG. 21) is placed on the outer cylinder 41 in the liquid concentration sensor unit 3500. This rectifying member 3610 has an outer diameter larger than the inner diameter of the outer cylinder 41, a ring-shaped side portion (plate-like portion) extending from the periphery to one side around the main body portion of a substantially disk shape in plan view. 3613).
That is, the rectifying member 3610 has three bridge portions 3612 extending in three directions in the planar direction from the shielding portion 3611 having a size and shape corresponding to the shielding portion 611 (disc shape) of the first embodiment. Further, at the tip of the bridge portion 3612, there is a plate-like portion 3613 that extends perpendicularly to the shielding portion 3611, curves and forms a flat ring shape, and is arranged along the outer peripheral surface 41 G of the distal end portion 411 of the outer cylinder 41. Is provided. Between the circumferential direction AXP of the axis AX and the bridge portions 3612, three flow holes 3610H forming the flow path LL are formed.

As shown in FIG. 20, the straightening member 3610 is configured such that the tip contact portion 3614 of the plate-like portion 3613 abuts on the tip 41 T (not shown in FIG. 20) of the outer tube 41, and the tip 41 T of the outer tube 41 is moved. While covering, positioning in the axial direction AXD is performed. The rectifying member 3610 is fixed to the outer cylinder 41 by spot welding in the thickness direction of itself and the outer cylinder 41 at the welding portion 3613W of the plate-like portion 3613. For this reason, unlike the case of using an adhesive or the like, there is no risk of swelling or deterioration due to the urea aqueous solution LQ, and on the other hand, the rectifying member 3610 can be fixed to the outer cylinder 41 more easily than when annularly welded. .
Moreover, the plate-like portion 3613 of the rectifying member 3611 and the distal end portion 411 of the outer cylinder 41 are welded in the thickness direction (the radial direction AXR of the axis AX). For this reason, compared with the case where a flat lid member is abutted against the front end surface 41T of the outer cylinder 41 and welded, the position selection of the welded portion 3613W is high, positioning is easy, and the plate shape of the rectifying member 3610 is easy. The part 3613 and the tip 411 of the outer cylinder 41 can be reliably welded.

  Even in the sensor 3001 according to the first modified example including the rectifying member 3610, the urea cylinder 41 and the plate-like portion 3613, the bridge portion 3612, and the shielding portion 3611 of the rectifying member 3610 are used to form urea through the tip opening OP of the outer cylinder 41. A flow path LL through which the aqueous solution LQ flows in the axial direction AXD inside and outside the outer cylinder 41 is configured. For this reason, the liquid exchange between the periphery of the temperature rise detection unit 511 of the concentration sensor element 51 and the outside of the sensor 3001 (outer cylinder 41) is possible.

On the other hand, the shielding portion 3611 of the rectifying member 3610 is in a state of closing a part (center portion) of the distal end opening OP of the outer cylinder 41. Specifically, as shown in FIG. 20, when the sensor 3001 (outer cylinder 41) is viewed from the front end side in the axial direction (from the lower left to the upper right in the drawing), the shielding portion 3611 of the rectifying member 3610 The front end portion 583 of the inner protector 58 is not visible. That is, the temperature rise detection unit 510 of the concentration sensor element 51 and the surrounding portion 581 of the inner protector 58 are within the shielding portion projection area PJ (not shown) in which the shielding portion 3611 of the rectifying member 3610 is projected onto the proximal end AXD2. It is supposed to be positioned.
Thereby, also in this modification 1, the liquid can move vigorously around the concentration sensor element 51 (temperature rise detection unit 511), and the problem that the output of the concentration sensor element 51 fluctuates can be appropriately suppressed.
The rectifying member 3610 is also integrally formed by press forming of a metal plate such as press punching or drawing.

In the above, the present invention has been described according to the first to third embodiments and the first modified embodiment. However, the present invention is not limited to the above-described embodiments and the like, and can be appropriately changed without departing from the gist thereof. Needless to say, this is applicable.
For example, in the above-described first embodiment, as the liquid state detection sensor 1, a sensor of a type in which the liquid level sensor unit 4 and the liquid concentration sensor unit 5 are combined is illustrated. However, the present invention can also be applied to a device that does not have a function as a liquid level sensor.
In the first embodiment, the method of detecting the urea concentration of the urea aqueous solution in the liquid concentration sensor unit 5 has been described. However, from the resistance value immediately after energization of the concentration sensor element 51 (internal heater wiring 518), the urea concentration is detected. The liquid temperature of the aqueous solution can also be measured. Therefore, it can also be used as a liquid temperature sensor for measuring the liquid temperature in addition to the urea concentration of the aqueous urea solution.
Further, in the first embodiment and the like, the liquid state detection sensor 1 is exemplified as having the wiring board 22 on which the control circuit is mounted. However, the liquid state detection sensor of the present invention only needs to include a liquid concentration detection element, a holder member that holds the liquid concentration detection element, a surrounding member, and the like, and includes a liquid state detection sensor that does not include a control circuit.

2 is a partially broken cross-sectional view of a liquid state detection sensor according to Embodiment 1. FIG. It is explanatory drawing which shows the external appearance of the rubber bush in the liquid concentration sensor part of a liquid state detection sensor, and an inner protector. It is a longitudinal cross-sectional view of a liquid concentration sensor part among the liquid state detection sensors concerning Embodiment 1. FIG. It is a longitudinal cross-sectional view of the liquid concentration sensor part in the longitudinal cross section orthogonal to the longitudinal cross-sectional view of FIG. (A) is explanatory drawing which shows each form and connection form of a density sensor element, a connection terminal, and a lead wire, (b) is a side view of the front-end | tip part of a density sensor element. It is a figure which shows the shape of an inner side protector, (a) is a front view, (b) is a side view, (c) is a bottom view, (d) is a longitudinal cross-sectional view. It is explanatory drawing which shows the mode of a coupling | bonding of a holder member and an inner side protector. It is a perspective view which shows the shape of a positioning member. It is a perspective view which shows the shape of a baffle member. It is explanatory drawing which shows the relationship between the outer cylinder, the rectification | straightening member, and the leg part of the positioning member at the time of seeing the liquid state detection sensor concerning Embodiment 1 from the axial direction front end side. It is a longitudinal cross-sectional view which expands and shows the front-end | tip part vicinity of an outer cylinder among the liquid state detection sensors concerning Embodiment 1. FIG. It is a fragmentary sectional view of the liquid state detection sensor according to the second embodiment. It is a longitudinal cross-sectional view of a liquid concentration sensor part among the liquid state detection sensors concerning Embodiment 2. FIG. It is the bottom view which looked at the liquid concentration sensor part from the tip side among the liquid state detection sensors concerning Embodiment 2. It is a perspective view which shows the shape of a baffle member. (A) is a top view of a rectifying member, (b) is a side view, (c) is a longitudinal sectional view, and (d) is a bottom view. It is a perspective view which shows the shape of a rubber bush. It is a perspective view which shows the external appearance of a liquid concentration sensor part among the liquid state detection sensors concerning Embodiment 3. FIG. The shape of a baffle member is shown, (a) (b) is a perspective view, (c) is a top view, (d) is a side view. It is a perspective view which shows the external appearance of a liquid concentration sensor part among the liquid state detection sensors concerning the modification 1. The shape of a baffle member is shown, (a) (b) is a perspective view, (c) is a top view, (d) is a side view.

Explanation of symbols

1, 1001, 2001, 3001 Liquid state detection sensor AX (A liquid state detection sensor) Axis line AXD (Axis line) Axial direction AXD1 Tip side AXD2 Base end side AXR (Axis line) radial direction (outer protector and plate-like part) Thickness direction)
AXR1 (axial) radially outer AXR2 (axial) radially inner AXP (axial) circumferential LQ urea aqueous solution (liquid)
LQH (Urea aqueous solution) level LL Flow path 2 Base 3 Sensor 4 Liquid level sensor 41 Outer cylinder (outside protector)
41T Tip OP Tip opening 411 Tip 41N Inner peripheral surface 41G Outer peripheral surface 41B Base end 42 Inner cylinder (inner electrode body)
5, 1500, 2500, 3500 Liquid concentration sensor unit 51 Concentration sensor element (liquid concentration detection element)
510 Temperature rise detection unit (detection unit)
58, 1580 Inner protector 581 Enclosing portion 582 Side portion 583 Tip portion (tip portion of the surrounding portion)
58H1, 58H2, 58H3, 58H4, 1580H1, 1580H2 Liquid circulation holes 58H6, 1580H6 Tip circulation holes 58H6P, 1580H6P Peripheries 58H6PO, 1580H6PO Peripheral outermost parts (outermost circumference of tip circulation holes in the radial direction of the axis) Part located in
r 1st radius (radial dimension from the axial line to the part located in the radial direction outermost side of the axial line in the peripheral edge of the tip circulation hole of the surrounding portion)
EH Surrounding area (parts in the surrounding area)
FH tip side area (site on the tip side of the enclosure)
61, 1610, 2610, 3610 Flow regulating members 2610H, 3610H Flow holes 611, 1611, 2611, 3611 Shield part PJ (shield part projected on axial direction base end side) Shield part projection region 1611F Fin-like part D2 Second gap ( (The radial gap between the fin-like part and the outer cylinder (outer protector) or plate-like part, whichever is closer)
611P, 1611P (outside edge of shield) 611PB, 1611PB (outside edge of shield) Bridge extension D1 First gap (bridge extension, outer cylinder (outside protector) and plate-like part, whichever is closer Radial gap)
611PI, 1611PI Periphery innermost part (part located in the innermost radial direction of the axis in the peripheral part of the shielding part)
R 2nd radius (radial dimension from the axis to the part located on the radially innermost side of the axis in the periphery of the shielding part)
H Distance between the enclosure and the shielding part (the shortest axial distance between the enclosure and the shielding part)
612, 1612, 2612, 3612 Bridge portions 613, 1613, 2613, 3613 Plate portions 613W, 1613W, 2613W, 3613W Welded portion 2613T (with outer cylinder (outer protector)) Tip LL flow path 614 , 1614 Engaging claw part (positioning part)
3614 Tip contact portion (positioning portion)

Claims (6)

A liquid state detection sensor for detecting a liquid state,
An outer protector having a distal end and a proximal end and extending along an axis, the distal end opening and forming a distal end opening;
Arranged in the outer protector,
A liquid concentration detection element having a detection unit for detecting the concentration of a specific component in the liquid;
Arranged in the outer protector,
An inner protector that surrounds the detection portion of the liquid concentration detection element with a gap from the detection portion, and surrounds the detection portion from at least the radial direction outside the axial line from the distal end side and from the radial outer side of the axial line. When,
A rectifying member fixed to the outer protector and closing a part of the tip opening; and
The inner protector is
The front end portion of the surrounding portion is formed with a front end circulation hole that communicates between the inside of the surrounding portion and a portion closer to the front end than the surrounding portion,
The rectifying member is
A shield located on the tip side of the inner protector,
A shielding portion having a form in which the detection portion of the liquid concentration detection element and the surrounding portion of the inner protector are located within a shielding portion projection region in which the projection portion is projected on the proximal end side in the axial direction;
A plurality of bridge portions disposed apart from each other in the circumferential direction of the axis, and extending from the shielding portion toward the outer protector; and
A plate-like plate-like portion connected to each of the bridge portions and disposed along the inner or outer peripheral surface of the outer protector;
The plate-like part is
A welded portion that is welded to the outer protector and welded in the thickness direction of the plate-shaped portion, the welded portion being welded to the outer protector, spaced apart from each other in the circumferential direction of the axis,
The liquid flows through the inside and outside of the outer protector in the axial direction through the tip opening by at least one of the outer protector and the plate-like portion of the rectifying member and the bridge portion and the shielding portion of the rectifying member. A liquid state detection sensor comprising a flow passage. The liquid state detection sensor according to claim 1,
Each of the bridge portions of the rectifying member extends from the bridge extension portion of the periphery of the shielding portion,
The shielding part of the rectifying member is
It is located on the radially inner side of the outer protector,
A fin-like portion that is located between the bridge portions in the circumferential direction of the axis and projects outward in the radial direction of the axis,
The radial gap between the outer protector and the plate-like portion located on the outer side in the radial direction is the diameter between the bridge extension portion and the outer protector or the plate-like portion, whichever is closer. Including a fin-shaped portion that is smaller than the directional gap,
The bridge part
A liquid state detection sensor in which at least a part of itself is located on a radially outer side of the bridge extension portion of the shielding portion and on a proximal end side with respect to the shielding portion. The liquid state detection sensor according to claim 1 or 2,
The liquid concentration detecting element is disposed on the axis,
The surrounding portion of the inner protector extends along the axis.
The dimension in the radial direction of the axis from the axis to the part located on the radially outermost side of the axis in the peripheral edge of the tip circulation hole of the surrounding portion is r,
The dimension in the radial direction from the axis to the part located on the radially innermost side of the axis in the periphery of the shielding portion is R,
A liquid state detection sensor configured to satisfy the following formula (1), where H is the shortest axial distance between the surrounding portion and the shielding portion.
H / 2 ≦ R−r ≦ 2H (1) The liquid state detection sensor according to any one of claims 1 to 3,
The rectifying member is
A liquid state detection sensor having a positioning portion that engages with a tip of the outer protector and positions the rectifying member in the axial direction. The liquid state detection sensor according to any one of claims 1 to 4,
The rectifying member is
A liquid state detection sensor formed integrally by press forming a metal plate. The liquid state detection sensor according to any one of claims 1 to 5,
Among the outer protectors, an inner electrode body extending in the axial direction is provided on the radial inner side of the axial direction proximal end side from the detection unit of the liquid concentration detection element,
A liquid state detection sensor capable of measuring a liquid level of the liquid interposed between the inner electrode body and the outer protector by a capacitance generated between the inner electrode body and the outer protector.

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