JPH10232217A - Oxygen sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure accurate conduction between both terminals while preventing damages of a sensor element which are caused by an increase in contact pressure between an element side terminal of the sensor element and an outputting terminal of a connection member and an inertial force of the connection member. SOLUTION: An oxygen sensor 11 comprises upper and lower sides cases 12, 13 and a sensor element 14 which is fixed inside the lower side case 12 and is provided with an electrode terminal and a heater terminal on both side faces. A connection member 26 having a recess part 28 inside the upper side case 13 is supported pivotably by a support shaft 27. On both side faces of the connection member 26 is provided an electrode lead line terminal 30 and a heater lead line terminal 31 connecting with external lead lines 33, 34. Lower end parts of the respective lead line terminals 30, 31 are bent in a leaf spring in the recess part 28, to form a pressure contact parts 30, 31. When the sensor element 14 is inserted into the recess part 28, pressure contact parts 30a, 31a are brought into pressing contact with the electrode terminal and heater terminal at a specific contact pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor for detecting an oxygen concentration of a gas, and more particularly, to an oxygen sensor for detecting an oxygen concentration of a gas. The present invention relates to an oxygen sensor in which both are electrically connected by pressure contact with each other.

[0002]

2. Description of the Related Art Conventionally, in air-fuel ratio control of an internal combustion engine, feedback control using an oxygen sensor has been performed. In general, this type of oxygen sensor has a sensor element in which an element body having a pair of electrodes and a heater for activating the element having a heating section are integrally formed, and this sensor element is held in a case. It has a structure. An external lead wire is connected to each electrode of the element body, and a detection signal from the electrode is input to an input circuit of the control device via the lead wire. Similarly, an external lead wire is also connected to the heat generating portion of the heater, and a predetermined current flows from the drive circuit of the control device to the heat generating portion via the lead wire.

Here, in the conventional oxygen sensor, an electrode or a heating part is connected to an external lead wire by, for example, soldering in order to ensure electrical conduction. However, since the sensor element is held in the case, the work of soldering the external lead wires to the electrodes or the like has been extremely complicated.

Therefore, an oxygen sensor has been proposed in which an electrode or the like and an external lead wire are pressed against each other at a predetermined contact pressure so as to ensure electrical conduction between the two. FIG. 6 shows a configuration example of this type of oxygen sensor. In this oxygen sensor 100, a case 101 is divided into an upper case 101a and a lower case 101b as shown in FIG. The sensor element 102 of the oxygen sensor 100 includes a plate-shaped element main body 103 having a pair of electrodes (not shown),
A plate-shaped heater 104 provided with a heat generating portion (not shown) is integrally formed. And this sensor element 1
02 has its lower end fixed to the inside of the lower case 101b via the support member 105.

[0005] As shown in FIG.
On the side surface (the left side surface of the sensor element 102 in FIG. 6), an electrode terminal 106 connected to the electrode is provided. Further, a heater terminal (not shown) connected to the heat-generating portion is provided on the side surface of the heater 104 (the right side surface of the sensor element 102 in FIG. 6), similarly to the electrode terminal 106.

On the other hand, inside the upper case 101a, a pair of electrode lead wires 10 connected to the electrode terminals 106 is provided.
7 and a pair of heater leads 108 connected to the heater terminals, respectively.
Portions 7 and 108 are fixed to the upper end of the upper case 101a by a seal member 109.

[0007] Lead terminals 110 and 111 are attached to the lower ends of the lead wires 107 and 108, respectively, and these terminals 110 and 111 are connected to the lower case 1 respectively.
01b is held by the connection member 112 provided in the inside. The connecting member 112 is formed of an insulating resin material, and the upper end thereof is
It is fixed to.

An insertion hole 113 is formed at a lower end of the connection member 112, and an upper end of the sensor element 102 is inserted into the insertion hole 113. A part of each of the lead wire terminals 110 and 111 is exposed inside the insertion hole 113, and the exposed portion and the electrode terminal 106 are formed.
The electrical contact between the lead wires 107 and 108 and the electrode terminals 106 and the like is secured by pressing the heater terminals and the heater terminals with a predetermined contact pressure.

In such an oxygen sensor 100, when the upper case 101a is fitted to the upper end of the lower case 101b to which the sensor element 102 is fixed, the upper end of the sensor element 102 is inserted into the connecting member 112. Hole 113
Then, each lead wire terminal 110, 111 is pressed into contact with the electrode terminal 106 and the heater terminal to electrically connect them. Thereafter, the two cases 101a and 101b are fixed to each other by caulking the overlapping portion 114 of the two cases 101.

Thus, in the oxygen sensor 100,
Since the lead terminals 110 and 111 are connected to the electrode terminals 106 and the heater terminals by pressure contact, the lead wires 107 and 10 are compared with the case of soldering.
Electrical conduction between the electrode 8 and the electrodes can be easily ensured.

[0011]

However, in the conventional oxygen sensor 100, the sensor element 102 is not fixed at a predetermined position in the lower case 101b, and the sensor body 102 is displaced as shown in FIG. May be fixed. In such a case, a bending moment acts on the sensor element 102 due to an excessive contact pressure to cause the sensor element 102 to be damaged, or conversely, each of the lead wire terminals 110 and 111 is not in contact with the electrode terminal 106 and the heater terminal. There is a possibility that a state in which electrical conduction is not ensured due to the state may occur.

In order to avoid such a problem, a slight gap is formed between the connecting member 112 and the lower case 101b, and the seal member 109 is formed of a rubber material. When the position shift occurs, the position of the connection member 112 is changed to the position of the seal member 10.
It is conceivable to adopt a configuration that changes according to the position of the sensor element 102 by the elastic deformation of No. 9. According to this configuration, it is possible to ensure electrical continuity between each of the lead wires 107 and 108 and the electrodes and the like.

However, in such a configuration, for example, when an impact is applied to the oxygen sensor 100, the inertial force of the connecting member 112 directly acts on the upper end of the sensor element 102, and May be damaged.

The present invention has been made in view of the above circumstances, and an object of the present invention is to press-contact an element-side terminal provided on a sensor element and an output terminal for outputting a lead wire provided on a connection member. In an oxygen sensor that electrically connects both terminals, secure conduction between both terminals while preventing damage to the sensor element due to increased contact pressure between the two terminals and the inertial force of the connecting member Is to do.

[0015]

In order to achieve the above object, an invention according to claim 1 is provided in which first and second cylindrical cases fitted to each other and held in the first case,
A rod-shaped sensor element having an element-side terminal for electrical connection provided on an outer peripheral surface of one end thereof, and a recess held in the second case and into which one end of the sensor element is inserted. A connection member provided with an output terminal for outputting an external lead wire which is pressed into contact with the element-side terminal and is electrically connected to the peripheral surface, wherein the connection member is swingable to the second case. The purpose is to be able to tilt with respect to the axis of the sensor element by being supported by the sensor element.

The element side terminal is a terminal electrically connected to an electrode for detecting oxygen concentration of the sensor element, a heating section of a heater provided in the element, and the like. In the above configuration, one end portion of the sensor element is inserted into the recess of the connection member when the first case and the second case are fitted. The output terminal provided in the recess is pressed against the element-side terminal of the sensor element. As a result, the element side terminal and the output terminal are electrically connected, and conduction between them is ensured.

Here, according to the above configuration, even if the sensor element is not held at a predetermined position in the first case, the connection member is inclined with respect to the axis of the sensor element. Does not greatly increase or decrease the contact pressure at Further, since the connection member is supported by the second case, even when an impact is applied to the oxygen sensor and an inertia force acts on the connection member, the inertia force is prevented from directly acting on the sensor element.

According to a second aspect of the present invention, there is provided an oxygen sensor according to the first aspect, wherein the connecting member is swingably supported by the second case by a supporting shaft. The purpose of the axis is to pass through the center of gravity of the connecting member.

According to the above construction, the connecting member is supported by the support shaft passing through the center of gravity in addition to the effect of the first aspect of the present invention. Even when a force is applied, the member does not swing around the support shaft due to the inertial force, and no external force due to the swing acts on the sensor element.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an oxygen sensor used for air-fuel ratio feedback control of an engine will be described below.

FIG. 1 is a sectional view showing the oxygen sensor 11, and FIGS. 2 and 3 are sectional views of the oxygen sensor 11 showing a state before an upper case 13 is fitted to a lower case 12 which will be described later. .

As shown in FIG. 1, the oxygen sensor 11 includes a lower case 12 having a substantially cylindrical shape with a bottom, an upper case 13 having a substantially cylindrical shape located above the case 12, and a lower case 12.
Is provided with a sensor element 14 provided therein.

The two cases 12 and 13 are fixed to each other by fitting the upper end of the upper case 13 to the upper end of the lower case 12 and then caulking a part of the overlapped portion. An attachment member 15 is externally fitted to the lower case 12, and the attachment member 15 is fixed to an exhaust pipe (both not shown) of the engine, so that the oxygen sensor 11 has a tip portion (FIG. 1). The lower part) is attached so as to protrude into the exhaust pipe.

An outer cover 16 for protecting the sensor element 14 and improving heat retention is formed by the tip of the lower case 12. Inside the outer cover 16 is provided an inner cover 17 having a cylindrical shape with a bottom and having the same function as the outer cover 16, and the bottom of the cover 17 is fixed to the bottom of the outer cover 16. Sensor element 14
Is fixed to the lower case 12 by the support member 18 such that the tip portion protrudes into the inner cover 17.

Each of the covers 16 and 17 has an introduction hole 1.
A plurality of exhaust pipes 9 and 20 are formed. Exhaust gas flowing through the exhaust pipe is introduced into the inner cover 17 through the respective introduction holes 19 and 20 and comes into contact with the tip of the sensor element 12.

The sensor element 14 is configured by laminating an element body 22 formed in a plate shape from a solid electrolyte material such as zirconia and a heater 23 formed in a plate shape from an insulating ceramic material such as alumina.

A pair of electrodes (not shown) made of platinum are provided on both side surfaces of the distal end of the element body 22. As shown in FIG. It is electrically connected to a pair of electrode terminals 25 provided on one side surface (left side surface in FIG. 1) of the base end portion of the main body 22.

On the other hand, a heating portion (not shown) for heating the element body 22 is built in the tip portion of the heater 23. A pair of heater terminals (not shown) having the same shape as the electrode terminal 25 is provided on one side surface (right side surface in FIG. 1) of the base end portion of the heater 23.
The heating section is connected to this heater terminal via a lead section (not shown).

As shown in FIGS. 2 and 3, a connection member 26 made of a resin material having excellent heat resistance and insulation properties is provided inside the upper case 13. As shown in FIG. 2, the connection member 26 is provided with a pair of support shafts 27 extending on both sides thereof, and each support shaft 27 is rotatably supported on the side of the upper case 13. As a result, the connection member 26 can swing around the support shaft 27 with respect to the upper case 13.

The axis of each supporting shaft 27 passes through the center of gravity of the connecting member 26 so that the connecting member 26 does not swing due to an inertial force acting when an impact is applied to the oxygen sensor 11. Position.

A recess 28 is formed at the lower end of the connecting member 26, and the upper end of the sensor element 14 is inserted into the recess 28. As shown in FIG. 2, a pair of electrode lead wire terminals 30 is provided on the left side surface of the connection member 26, and extends in parallel with the longitudinal direction of the connection member 26 (the axial direction of the oxygen sensor 11).

As shown in FIG. 3, the lower end of the electrode lead wire terminal 30 is bent into a leaf spring shape inside the recess 28 to form a press contact portion 30a. The pressure contact portion 30a is pressed against the electrode terminal 25 with a predetermined contact pressure in an elastically deformed state.

On the other hand, as shown in FIG. 3, on the right side of the connection member 26, a pair of heater lead terminals 31 having the same shape as the electrode lead terminal 30 is provided. The lower end of the heater lead wire terminal 31
8 is bent into a leaf spring shape to form a press contact portion 31a. The press contact portion 31a is also elastically deformed and pressed against the heater terminal with a predetermined contact pressure.

As shown in FIG. 3, each case 12, 1
Before the assembly 3 is assembled, each of the press contact portions 30
The gap G1 between the contact elements 30a and 31a is set to be slightly shorter than the width B1 of the sensor element 14 in order to secure a predetermined contact pressure between each of the press contact portions 30a and 31a and the electrode terminal 25 and the heater terminal. .

A pair of cutouts 32 (only one of them is shown in FIG. 3) are provided at the upper end of the lower case 12 to avoid interference with the support shaft 27.
Are located in the notches 32.

As shown in FIG. 1, the lead terminals 30 and 31 described above are electrically connected to external lead wires 33 and 34 at the upper end of the connecting member 26, respectively.
The external lead wires 33 and 34 are fixed at the upper end portion of the upper case 13 by a seal member 35 made of a rubber material, and extend to the outside of the case 13 to extend an input circuit or a drive circuit of a control device (both are illustrated). (Abbreviated). As a result, the electrode of the element body 22 is connected to the input circuit via the lead portion 24, the electrode terminal 25, the electrode lead terminal 30, and the external lead wire 33, and the heat generating portion of the heater 23 is the lead portion, It is connected to a drive circuit via a heater terminal, a heater lead wire terminal 31, and an external lead wire.

In such an oxygen sensor 11, the heating of the heater 23 is controlled by a control device via a drive circuit, so that the element body 22 is heated to a predetermined activation temperature. As a result, a signal corresponding to the oxygen concentration of the exhaust gas in contact with the element body 22 is stably output from the electrode to the input circuit. Then, the control device executes the air-fuel ratio feedback control of the engine based on the input detection signal.

Next, the operation and effect of the oxygen sensor 11 according to this embodiment will be described. In the present embodiment, as described above, the connection member 26 is provided to be swingable with respect to the upper case 13 by the support shaft 27. For this reason, as shown in FIG. 4, when the sensor element 14 is not arranged at a predetermined position (the position shown by a two-dot chain line in FIG. 4) and is fixed to the lower case 12 in a state where the sensor element 14 is misaligned, When the connecting member 26 swings around the support shaft 27 and the pressure contact portions 30a and 31a are pressed against the electrode terminals 25 and the heater terminals in a state where the connection members 26 are inclined by a predetermined angle with respect to the axis of the sensor element 14, respectively. You. For this reason, the contact pressure does not greatly increase or decrease as compared with the case where the connection member 26 is arranged at the predetermined position.

As a result, according to the present embodiment, it is possible to prevent the contact pressure from increasing and the sensor element 14 from being damaged due to an excessive bending moment acting on the sensor element 14. It is possible to avoid a state where the lead wire terminals 30 and 31 (press-contact portions 30a and 31a) and the electrode terminal 25 and the heater terminal do not come into a non-contact state, and to ensure reliable electrical conduction between the two terminals. .

Also, according to the present embodiment, the upper case 1
When the sensor element 14 is externally fitted to the lower case 12,
By simply inserting the upper end of the contact member into the concave portion 28 of the connection member 26, a predetermined contact pressure between each of the press contact portions 30a, 31a and the electrode terminal 25 and the heater terminal can be secured, and the contact pressure Therefore, the productivity of the oxygen sensor 11 can be improved in this sense.

By the way, unlike the present embodiment, if the connecting member 26 is not supported by the upper shaft 13 by the support shaft 27, the oxygen sensor 11 may vibrate,
When an impact is applied to the sensor, an excessive bending moment acts on the sensor element 14 due to the inertial force of the connecting member 26, and the element may be damaged. Further, even when the connection member 26 is supported on the upper case 13 by the support shaft 27, if the axial position of the support shaft 27 does not pass through the center of gravity of the connection member 26, for example, the oxygen sensor 11
When an impact or the like is applied, the connecting member 26 swings around the support shaft 27, and there is a concern that a bending moment acts on the sensor element 14 as described above.

In this regard, according to the present embodiment, the connection member 2
6 is supported on the upper case 13 by a support shaft 27, and the axis of the support shaft 27 passes through the center of gravity of the connecting member 26. Therefore, even when an impact is applied to the oxygen sensor 11, a bending moment caused by the inertial force of the connection member 26 does not act on the sensor element 14, so that the damage of the sensor element 14 as described above can be prevented. it can.

This embodiment can be implemented by changing the configuration as follows. With such a configuration, the same operation and effect as the embodiment can be obtained. In the above-described embodiment, the portions of the respective lead wire terminals 30 and 31 in the concave portion 28 are formed in a leaf spring shape so that the pressure contact portions 30 are formed.
However, for example, a pressure contact portion may be similarly formed on the electrode terminal 25 or the heater terminal, and each terminal may be pressed against each of the lead wire terminals 30 and 31 at this portion. Further, these pressure contact portions need not necessarily be formed to have a leaf spring shape, but may be formed in a coil spring shape, for example.

In the above embodiment, each lead wire terminal 3
The pressure contact portions 30a and 31a having a leaf spring shape are formed at 0 and 31. However, for example, a configuration as shown in FIG. 5 can be adopted. That is, in the connecting member 26, a convex portion 40 having a semicircular cross section
41 is formed, and the lower end portions of the electrode lead terminal 30 and the heater lead terminal 31 are bent and arranged on the respective convex portions 40 and 41. Even with such a configuration, as shown in FIG. 5, the connection members 26 are inclined so that the lead terminals 30, 31 are brought into pressure contact with the electrode terminals 25 and the heater terminals with a substantially predetermined contact pressure. Can be.

In the above-described embodiment, the oxygen sensor 11 according to the present invention is embodied as an oxygen sensor applied to air-fuel ratio control of an engine. Can also.

[0046]

According to the first aspect of the present invention, the connection member provided with the output terminal is swingably supported by the second case,
The sensor can be inclined with respect to the axis of the sensor element provided with the element-side terminals.

Therefore, even if the sensor element is not held at a predetermined position in the first case, since the connecting member is inclined with respect to the axis of the sensor element, the connection member between the element side terminal and the output terminal is not provided. The contact pressure does not greatly increase or decrease. Further, since the connecting member is supported by the second case, even when an inertial force acts on the connecting member due to an impact applied to the oxygen sensor, the inertial force is prevented from directly acting on the sensor element.

As a result, according to the present invention, it is possible to prevent the sensor element from being damaged due to the increase in the contact pressure between the two terminals and the inertial force of the connecting member, and to ensure the conduction between the two terminals. Can be secured.

According to the second aspect of the present invention, the connecting member is formed of the second member.
The axis of the support shaft supported by the case passes through the center of gravity of the connection member. Therefore, even when inertial force acts on the connecting member due to vibration or the like, the inertial force does not cause the member to swing around the support axis, and external force resulting from the swing acts on the sensor element. There is no. As a result, according to the present invention, in addition to the effects of the invention described in claim 1, it is possible to prevent the sensor element from being damaged due to the external force acting as described above.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an oxygen sensor according to one embodiment.

FIG. 2 is a partial cross-sectional view showing the oxygen sensor.

FIG. 3 is a partial sectional view showing the oxygen sensor.

FIG. 4 is a partial cross-sectional view showing a state where a connection member of the oxygen sensor is inclined.

FIG. 5 is a partial cross-sectional view showing a configuration change example of the connection member.

FIG. 6 is a sectional view showing a conventional oxygen sensor.

FIG. 7 is a side view showing a sensor element of the oxygen sensor.

FIG. 8 is a sectional view showing a main part of the oxygen sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Oxygen sensor, 12 ... Lower case, 13 ... Upper case, 14 ... Sensor element, 25 ... Electrode terminal, 26 ... Connection member, 27 ... Support shaft, 28 ... Depression, 30 ... Electrode lead wire terminal, 31 ... Head wire terminal for heater, 30a, 31a
... Press-contact part.

Claims (2)

[Claims] A first case and a second case which are fitted to each other and are held in the first case; and an element-side terminal for electrical connection is provided on an outer peripheral surface of one end of the first case and the second case. A rod-shaped sensor element, a recess held in the second case, into which one end of the sensor element is inserted, and an inner peripheral surface of the recess pressed into contact with the element-side terminal to be electrically connected thereto A connection member provided with an output terminal for outputting an external lead wire, wherein the connection member is pivotally supported by the second case so as to be inclined with respect to an axis of the sensor main body. An oxygen sensor characterized in that it is possible. 2. The connecting member is connected to the second member by a support shaft.
2. The device according to claim 1, wherein the supporting member is swingably supported by the case, and an axis of the supporting shaft passes through a center of gravity of the connecting member.
An oxygen sensor according to any of the preceding claims.