JP4441103B2 - Sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sensor attached to an exhaust pipe of a heat engine.
[0002]
[Prior art]
Conventionally, various sensors such as an O ₂ sensor, an HC sensor, and a NOx sensor are known as sensors attached to an exhaust pipe of a heat engine such as an internal combustion engine.
[0003]
This type of gas sensor is configured, for example, such that a rod-shaped detection element is inserted and held in a cylindrical metal shell fixed to an exhaust pipe, and one end thereof is exposed to a gas to be measured. In addition to forming an electrode for taking out a signal on the detection element, an electrode for supplying power to the heater is also formed when the detection element is provided with a heater. In order to extract a detection signal from the electrode of the detection element or to supply power to the electrode, it is necessary to electrically connect a lead wire drawn to the outside to the electrode through a conductive connection member.
[0004]
Conventionally, the connection between the lead wire and the detection element via the connecting member has been performed as follows using a lead frame having the same number of tip portions as the electrodes. First, each front end portion of the lead frame is connected to the electrode of the detection element by an interference fit (see, for example, Japanese Patent Application Laid-Open No. 11-326263), and then the front end portion is separated by separating the rear portion of the lead frame. Then, a lead wire is welded to each remaining tip (that is, each connecting member), and in order to further insulate, a cylindrical insulating member provided with a through hole that accommodates each connecting member and the lead wire is provided. It is a condition of covering.
[0005]
[Problems to be solved by the invention]
However, in such a conventional method, there is a problem that it is difficult to automate and mechanize the welding of the lead wire to each tip portion of the lead frame. Further, when the connecting member is accommodated in the through hole of the insulating member, if the alignment between the through hole and the connecting member is not sufficient, the connecting member may be bent and short-circuited, and the assembly is not easy. .
[0006]
The present invention is based on such a problem, and an object thereof is to provide a sensor that can easily connect a lead wire and an electrode of a detection element via a connection member.
[0007]
[Means for Solving the Problems and Effects of the Invention]
In order to solve the above problems, in the sensor according to the present invention (claim 1), the insulating member has a housing portion that at least partially houses the connection member at a position farther from the exhaust pipe than the electrode of the detection element. In addition, the connection member has a rotation inhibiting portion that inhibits rotation around the axis of the connection member by engaging with the accommodating portion of the insulating member.
[0008]
That is, since the conventional insulating member merely accommodates the connecting member in order to insulate the connecting member, the connecting member cannot be reliably supported while preventing the connecting member from rotating. Then, after connecting the connection member to the electrode of the detection element, the procedure of covering the connection member with the insulating member is taken.
[0009]
On the other hand, in the present invention, rotation around the axis of the connecting member is inhibited by the rotation inhibiting portion that engages the accommodating portion of the insulating member, so that the connecting member previously connected to the lead wire is held by the insulating member. The connection member and the detection element can be connected. As a result, there is no process of covering the insulating member later, and it is possible to prevent the connecting member from being bent in that process. In addition, since the rotation of the connection member around the axis is suppressed, the connection member can be reliably aligned with the position of the electrode of the detection element, and the connection member and the detection element can be reliably and easily connected.
[0010]
Moreover, since the accommodating portion is provided at a position farther from the exhaust pipe than the electrode of the detection element, and at least partially accommodates the connecting member at that position, the connecting member can be reliably held. That is, the temperature of the detection element tends to increase because it touches the high-temperature exhaust gas, and the closer to the exhaust pipe, the more the connection member and the insulating member are exposed to high temperatures. Therefore, if the housing portion is provided at a position farther from the exhaust pipe than the electrode of the detection element, the possibility that the support of the connection member becomes unstable due to heat deformation can be reduced.
[0011]
Accommodating portion is configured to connect members as insertable insertion hole, the shape of the cross section, the size of the circumscribed circle is formed in a different shape and its inscribed circle. For this reason, rotation of a connection member can be prevented easily .
[0012]
Rotation preventing part of the connecting member is formed by bending along the plate-like body on the inner peripheral surface of the accommodating portion, thereby you can engage with the inner periphery of the housing portion of the rotation inhibiting unit. If connecting member having such rotation inhibiting unit manufactured Ru facilitates der.
In addition, as the cross-sectional shape of the accommodating portion, for example, a fan shape can be considered as described in claim 2, and various shapes such as a polygon, an ellipse, a shape with a key groove on a perfect circle, and a spline are adopted. Can do.
[0013]
As the connection mode between the connecting member and the lead wire, various things such as welding are conceivable. For example, as shown in claim 3 , a crimping portion to be crimped to the lead wire by caulking is integrally formed. If the connection member is used, the connection member and the lead wire can be easily connected. Further, various modes of connection between the connection member and the electrode of the detection element are conceivable, such as welding. For example, as shown in claim 4 , a press-fit ring press-fitted so as to surround the connection member and the detection element It is simple and preferable to use an interference fit in which the connecting member is crimped to the electrode of the detection element by the tightening force from above.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described below with reference to the drawings.
In this embodiment, the sensor of the present invention is configured as an oxygen sensor, and FIG. 1 is a cross-sectional view showing the overall configuration of the oxygen sensor.
[0015]
As shown in FIG. 1, the oxygen sensor 1 includes a shaft-shaped detection element 2 having a rectangular cross section, a cylindrical metal shell 7 through which the detection element 2 can be inserted, and the like.
The detection element 2 is formed by laminating an oxygen concentration cell element formed in a long plate shape and a heater for activating the oxygen concentration cell element (not shown). A holding member 4 made of ceramic for locking and fixing the detection element 2 in the casing 3 is bonded to the outer peripheral surface near the center in the axial direction of the detection element 2. In addition, a detection unit 2a that is exposed to the gas to be measured and detects a gas component to be measured is provided at the front end (lower side in the figure) of the detection element 2, and the detection unit 2a is provided at the rear end. The electrode 2b for taking out the electromotive force of the oxygen concentration cell generated and supplying power to the heater is provided at a plurality of locations (four locations in this embodiment), and the same number of metal terminals as the electrodes 2b 11 (corresponding to “connecting member” in the claims) is connected to each electrode terminal 2b.
[0016]
An insulating plate 12 is provided outside the metal terminal 11, and the clamping force by the press-fitting ring 13 press-fitted so as to surround the detection element 2, the metal terminal 11, and the insulating plate 12 is passed through the insulating plate 12. The electrical and mechanical connection between the electrode 2b and the metal terminal 11 is achieved by crimping 11 to the electrode 2b.
[0017]
The metal shell 7 attaches the oxygen sensor 1 to the wall surface of the exhaust pipe, holds the detection element 2 fitted with the holding member 4 therein, and touches the detection part 2a of the detection element 2 to the exhaust gas in the exhaust pipe. It is configured to make it happen.
Double metal protectors 31 and 32 having a plurality of holes are attached to the outer periphery of the front end side (lower side in the figure) of the metal shell 7 while covering the protruding portion of the detection element 2 by welding or the like.
[0018]
On the inner periphery of the metal shell 7, there is a step portion 7 a that protrudes inwardly on the tip side, and the step portion 7 a engages with the holding member 4 to support the detection element 2 from below. . Further, between the inner peripheral surface of the metal shell 7 and the outer peripheral surface of the detection element 2 on the rear end side (upper side in the drawing) of the holding member 4, a filler 5 made of talc powder is made of a ring-shaped metal. It is filled with a compressive force received from the cylindrical pressing member 6 via the packing 15.
[0019]
An outer cylinder 8 extends from the rear end of the metal shell 7. A lead wire 20 is drawn out from the upper end opening of the outer cylinder 8, and a rubber seal member 16 having a through hole through which the lead wire 20 passes is provided in the upper end opening for waterproofing. ing. The seal member 16 is fixed by being caulked in the radial direction via the outer cylinder 8.
[0020]
A separator 14 formed in a substantially cylindrical shape with an insulating resin is provided below the seal member 16 and between the detection elements 2 as shown in FIGS. The separator 14 corresponds to an “insulating member” in the claims, and includes a through hole 14 a into which the lead wire 20 is inserted from one side and the metal terminal 11 is inserted from the other side. Each lead wire 20 is joined to a part of the metal terminal 11 by caulking, but the caulking portion 11a is integrally formed at the rear end of the metal terminal 11 and is accommodated in the through hole 14a. Yes.
[0021]
In the through hole 14 a of the separator 14, an accommodation portion 14 b that partially accommodates the metal terminal 11 is formed on the detection element 2 side. That is, the accommodating portion 14b is formed as a hole (insertion hole) into which the metal terminal 11 can be inserted. The accommodating portion 14b is located farther from the exhaust pipe than the electrode 2b of the detection element 2, and the shape of the cross section is formed in a shape in which the size of the inscribed circle and the circumscribed circle are different. Has been.
[0022]
The metal terminal 11 is formed of a plate-like body, and a part of the metal terminal 11 is formed as a rotation restraining portion 11b that is bent along the inner peripheral surface of the housing portion 14b. And this rotation suppression part 11b is engaged with the inner periphery of the accommodating part 14b of the separator 14, and, thereby, the metal terminal 11 is being fixed to the separator 14. FIG.
[0023]
Although the metal terminal 11 can be inserted into the housing portion 14b from the detection element 2 side, when the metal terminal 11 is inserted, the rotation suppression portion 11b engages with the step portion 14c inside the through hole 14a. The metal terminal 11 is positioned inside the through hole 14a. Moreover, since the cross section of the accommodating part 14b is non-circular (specifically fan shape), this prevents the metal terminal 11 from rotating in the through hole 14a (that is, the accommodating part 14b). The
[0024]
In the oxygen sensor 1 having the above configuration, the metal terminal 11 is connected to the electrode 2b of the detection element 2 as follows. As shown in FIG. 5, the metal terminal 11 is crimped and connected to the lead wire 20 (FIG. 5A), and in this state, the metal terminal 11 is engaged with the separator 14 (FIG. 5B). Then, the tip of the metal terminal 11 is brought into contact with the electrode 2b of the detection element 2 (FIG. 5C), and the tip of the metal terminal 11 is pressed by the insulating plate 12, while the detection element 2, the metal terminal 11 and the insulating plate are pressed. The press-fitting ring 13 is press-fitted so as to surround 12 (FIG. 5D). In this way, the metal terminal 11 is fixed to the electrode 2b of the detection element 2.
[0025]
As described above, in the oxygen sensor 1 of the present embodiment, the separator 14 has the fan-shaped housing portion 14b that engages with the rotation restraining portion 11b of the metal terminal 11, and the metal terminal 11 is connected to the housing portion 14b. Supports not to rotate. Therefore, as shown in FIG. 5, the metal terminal 11 and the electrode 2 b of the detection element 2 can be reliably and easily connected in a state where the metal terminal 11 previously connected to the lead wire 20 is held by the separator 14. It is possible to prevent the metal terminal 11 from being bent.
[0026]
In addition, since the accommodating portion 14b of the separator 14 is provided at a position farther from the exhaust pipe than the detection element 2 and holds the metal terminal 11 at that position, it is hardly affected by heat and reliably holds the metal terminal 11. Can do.
As mentioned above, although the Example of this invention was described, this invention is not limited to the said Example, It can take a various aspect.
[0027]
For example, the present invention is not limited to gas sensors such as oxygen sensors.
In addition, the material, arrangement, shape, and the like of the separator 14 and the metal terminal 11 described above are not limited to those of the above-described embodiments, and may be changed as appropriate for convenience of design.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an oxygen sensor as one embodiment.
FIG. 2 is a diagram showing a separator from the detection element side.
FIG. 3 is a cross-sectional view taken along the line AA in FIG.
FIG. 4 is an explanatory view showing a state in which a metal terminal is supported on a separator.
FIG. 5 is an explanatory diagram showing a procedure for connecting a metal terminal to a detection element;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Oxygen sensor 2 ... Detection element 2b ... Electrode 11 ... Metal terminal 11a ... Clamping part 11b ... Rotation suppression part 12 ... Insulation plate 13 ... Press-fit ring 14 ... Separator 14a ... Through-hole 14b ... Housing part 20 ... Lead wire

Claims (4)

A sensing element;
A lead wire electrically connected to the electrode of the detection element and drawn to the outside;
A conductive connection member for electrically connecting the lead wire and the detection element;
An insulating member for insulating the connecting member by holding the connecting member;
A sensor comprising
The insulating member has an accommodating portion that at least partially accommodates the connecting member at a position farther from the exhaust pipe than the electrode of the detection element;
The accommodating portion is formed as an insertion hole into which the connection member can be inserted, and the shape of the cross section is formed in a shape in which the size of the inscribed circle and the circumscribed circle is different,
The connecting member have a rotation inhibiting unit that inhibits rotation about the axis of the connecting member by engagement with the receiving portion,
The rotation restraining portion is formed by bending a plate-like body along the inner peripheral surface of the housing portion, and is engaged with the inner circumference of the housing portion.
Sensor characterized by. The housing part is formed in a fan-shaped cross section,
The sensor according to claim 1. The connecting member is formed by integrally forming a caulking portion to be crimped to the lead wire by caulking,
The sensor according to claim 1 or 2. The connection member is pressure-bonded to an electrode of the detection element by receiving a force from a press-fitting ring press-fitted so as to surround the connection member and the detection element;
The sensor according to any one of claims 1 to 3.

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