JPS633250A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To detect accurate oxygen concentration by providing a solid-state electrolytic element, a couple of electrodes, a housing, leads, an insulating layer, etc. CONSTITUTION:This oxygen sensor is provided with the couple of electrodes 7 and 7', the insulating layer 12 which is laminated on the external surface of the solid-state electrolytic element 4 and covers a lead 8' at a position including the position of engagement with the housing 6, etc. Then, a signal from the electrodes 7 is outputted to a control circuit through leads 8, 10, and 9. A signal from the electrode 7', on the other hand, is outputted to the control circuit through leads 8', 10', and 9' and grounded. The output systems for those signals including the electrodes 7 and 7' are both insulated by insulating elements from the housing 6 which conducts to an engine system. Consequently, an output signal sent from the oxygen sensor 1 to the control circuit through a lead element 5 is hardly affected by noises from the engine system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an oxygen sensor, and particularly to an oxygen sensor installed in the exhaust gas system of a vehicle (hereinafter referred to as a vehicle oxygen sensor).

(Prior art and problems) A vehicle oxygen sensor has a bag-shaped solid electrolyte element,
A pair of electrodes are provided on the inner and outer surfaces of the element, the inner electrode (reference electrode) is connected to mulberry oxygen gas, and the outer electrode (measurement electrode) is connected to the mulberry oxygen gas.
The sensor is brought into contact with oxygen gas to be measured, a potential difference is created between the two electrodes in response to the difference in oxygen concentration between the inner and outer surfaces of the element, and a signal based on this potential difference is output to a control circuit to detect the oxygen concentration. be.

The housing of such a vehicle oxygen sensor is attached to an exhaust gas system manifold.

One electrode (usually the base electrode) was electrically connected to the control circuit, while the other electrode (usually the measuring electrode) was grounded through the housing and therefore through the exhaust gas system (for example, Japanese Patent Publication No. 59-41952).

However, since the output of this type of oxygen sensor is weak, it is affected by engine noise, such as spark plug noise or noise due to a potential difference in ground current, making accurate detection difficult. is difficult. There are problems such as:

Therefore, an attempt could be made to incorporate a noise filter into the control circuit to electrically reduce noise related to the output of the oxygen sensor, but this would make the device complicated.

In addition to being expensive, it is difficult to completely eliminate noise.

(Means for Solving Problems) In view of the problems of the prior art, it is an object of the present invention to prevent the output of an oxygen sensor from being affected by engine noise as much as possible, and to ensure accurate oxygen concentration using a vehicle oxygen sensor. The purpose is to enable the detection of

The oxygen sensor of the present invention includes a bag-shaped solid electrolyte element whose front end is a detection part and whose rear end is an output extraction part, and a pair of electrodes provided on the inner and outer surfaces of the element in the detection part. ,
a housing that accommodates the element and the electrode; the housing is provided on the outer surface of the element, the tip thereof is connected to the rear end of the electrode mounted on the outer surface, and the rear end is connected to the output extraction part; and an insulating layer laminated on the outer surface of the element and cresting the lead at a position that includes at least the engagement portion with the housing.

(Embodiment) (1) The lead preferably extends in a band shape along the front-rear direction of the outer surface of the element.

The lead material may be a noble metal such as platinum (Pt).

(2) The insulating layer covers the tip of the lead (the part used for connection with the outer electrode) and the rear end (the part that is the output extraction part of the element and is used for connection with the intermediate lead described later). It is preferable to remove the lead and remove the lead.

Examples of the material for the insulating layer include ceramic, glass, and cement.

(Function) With this configuration, the signal from the electrode based on the difference in oxygen concentration between the inner and outer surfaces of the solid electrolyte element is output to the outside of the housing through the lead without going through the housing.
earth).

(Example) An embodiment of the present invention will be described below based on the drawings.

1 to 4, reference numeral 1 denotes an oxygen sensor. This oxygen sensor 1 is attached to an exhaust gas manifold 2 of an engine system of a vehicle, and its signal is output to a control circuit 3.

The oxygen sensor 1 generally includes a bag-shaped solid electrolyte element 4 that generates a partial pressure difference depending on the oxygen gas concentration.

It is composed of a lead element 5 that outputs a signal based on the element 4 to the control circuit 3, and a housing 6 that surrounds the element 4 and the lead element 5 (the negative part).

The tip of the element 4 is a detection part 4a, and exhaust gas A is present on the outside thereof, and base gas B is present on the inside thereof, and a difference in oxygen concentration is created between the exhaust gas A and the base gas B. I'm starting to get it. Further, the rear end portion serves as an output extraction portion 4b.

The signal from the element 4 is transmitted to the control circuit from this output extraction section 4b. Note that 4c is a flange portion formed to protrude outward at an intermediate portion of the element 4 in the front-rear direction.

This element 4 has a porous reference electrode 7 on its inner surface in the entire circumferential direction of the detection part 4a. A porous measuring electrode 7' is provided on its outer surface, and is adapted to generate a potential difference based on the oxygen concentration difference.

The lead cable 5 includes element leads 8, 8° and external leads 9.
．． 9' and intermediate lead 10. It consists of 10 degrees. The element leads 8, 8° are provided on the inner and outer surfaces of the cord 4, and their tips are connected to the rear ends of the respective electrodes 7, 7°, and extend backward in a band shape along the shape of the element 4, and output. It has reached the take-out part 4b. - direction.

External leads 9 and 9° extend from the control circuit 3 and are inserted into the rear end of the housing 6. intermediate lead 1
0.10' is disposed in the housing 6 1) between the output extraction part 4b of the element 4 and the insertion end of the external lead 9.9°, and a pair of electrodes 7, related to the element 4. 7° and a pair of external leads 9.9° related to the control circuit 3 are connected. Here, the tip of the intermediate lead 10.10° is a springy band-like body lOa, 10'a, and at the output extraction portion 4b of the element 4, the band-like body 10a is brought into contact with the rear end of the element lead 8. By bringing the strip 10°a into contact with the rear end of the element lead 8°, the electrodes 7 and 7° and the intermediate leads lo and too are connected via the element leads 8 and 8°. - On the other hand, the rear end of the intermediate lead 10°10° is formed into a split cylindrical body 10b, 10°b.

By fitting the cylindrical bodies 10b and 10°b into the insertion ends of the external leads 9 and 9°, respectively, the control circuit 3
and intermediate lead 10. 10° are connected via external leads 9° and 9°. Then, in the control circuit 3,
The output related to measurement electrode 7° is grounded.

Here, the measurement was performed on the outer surface side of the element 4.

A porous protective layer 11 is laminated to cover the electrode 7', and also covers the element lead 8' (excluding the rear end 8'a used for connection to the intermediate lead 10'). Insulating layers 12 are laminated. Note that since the 71+11 constant electrode 7'' and the protective layer 11 are porous, contact of the exhaust gas A to the element 4 is ensured.

The housing 6 has a mounting bracket 13 fixed to the manifold 2, and a protective cap 14 for preventing thermal deterioration of the detection portion 4a of the element 4 is provided at the front of the mounting bracket 13, while The intermediate leads to, to
A first cylindrical body 15 and a second cylindrical body 16 are disposed to surround a portion (insertion end) of the external leads 9 and 9'. A stepped portion 13a is formed on the inner surface of the mounting bracket 13, and a portion corresponding to the collar portion 4C of the element 4 engages with this stepped portion 13a, and is pressed by the sealing body 17 from the rear. Element 4 is held in place. Cylindrical body 15.
l[i and outer element lead 8°, intermediate lead 10.
10', there is an insulator 18 as appropriate in the front-to-back direction.
．． 18.18 has been interposed.

Note that 19 is a heater, and 20 is a lead element related to the heater.

Next, the operation of the oxygen sensor having such a configuration will be described.

Now, the potential difference based on the concentration difference of oxygen gas is between the picture electrodes 7 and 7.
′. Then, the signal from the base electrode 7 is transmitted to the element lead 8. It is output to the control circuit 3 via the intermediate lead IO and the external lead 9. - On the other hand, the signal from the measuring electrode 7° is.

Element lead 8°, intermediate lead 10° and external part 9
It is outputted to the control circuit 3 via .degree. and grounded. Here, the output system of such a signal is a housing that can be electrically connected to the engine system (namely, the mounting bracket 13, the protective cap 14, and the cylinder body 15, 16), regardless of whether the two electrodes are connected at 7.7 degrees.

Insulator cord (i.e. insulator layer 12 and insulator 18°1
8, 18). Therefore, the output signal from the oxygen sensor 1 via the lead element 5 to the control circuit 3, or the noise from the engine system.

Therefore, it is hardly affected.

(Other Embodiments) (1) The solid electrolyte element 4 may have a flange portion that serves as a rear end portion, that is, an output extraction portion.

In this case, the element lead 8' is extended to the rear end surface of the element 4.
It is preferable to take out the output by surface contact.

(2) The solid electrolyte element 4 has an outer circumferential surface that is substantially flat over the entire front and back direction.

The measurement electrode 7 may also be formed in a flat shape), and the insulating layer 12 may form a flange portion that engages with the mounting fitting 13.

(3) The signals related to the electrodes 7, 7° may be grounded in any manner as long as they are not grounded through the housing 6 directly connected to the engine system.

For example, the signal output to the outside of the housing δ via the external lead 9° may be grounded without passing through the control circuit 3. Further, the signal related to the reference electrode 7 may be grounded.

(4) Element lead 8°8" in the output extraction part 4b
Nine different means can be used to connect the intermediate lead 10.10° to the intermediate lead 10. Specifically, this includes joining (for example, welding) or locking (for example, locking ring).

(Effects of the Invention) As described above, according to the present invention, the problems of the prior art described above can be solved and the accuracy of detecting oxygen concentration by an oxygen sensor can be improved.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an example of the mounting position of an oxygen sensor according to the present invention. FIG. 2 is a partial sectional view showing the whole of one embodiment of the present invention. FIG. 3 is a perspective view showing a reed-like portion of the solid electrolyte element of the embodiment, and FIG. 4 is an enlarged sectional view of a main part of the embodiment. represents. 1...Oxygen sensor, 4...Solid electrolyte element. 4a...detection section, 4b...output extraction section. 6.Housing. 7.7°...electrode (reference electrode, measurement electrode). 8°...Lead (element lead provided on the outer surface). 12...Insulating layer. Applicant: Uhon Tokushu Togyo Co., Ltd. Agent: Asamichi Kato (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 7'

Claims (1)

[Scope of Claims] A bag-shaped solid electrolyte element whose front end is a detection part and whose rear end is an output extraction part; a pair of electrodes provided on the inner and outer surfaces of the element in the detection part; a housing for accommodating the element and the electrode; a lead provided on the outer surface of the element, the tip of which is connected to the rear end of the electrode provided on the outer surface, and the rear end of which extends to the output extraction section; and an insulating layer that is laminated on the outer surface of the element and covers the lead at a position that includes at least a portion that engages with the housing.