JPH10206372A - Oxygen sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain introducing holes formed in a cover of an oxygen sensor from being clogged by a deposit. SOLUTION: An oxygen sensor 30 has a sensor element 31 and a cover 32 to cover an outer periphery of the element 31. The cover 32 is formed in a bottomed cylindrical shape, and plural introducing holes 40 are formed in its side part. A rotary body 50 is arranged between the sensor element 31 and the cover 32 so as to be rotatable around the axis of the element 31. The rotary body 50 has four blades 51 and first and second deposit removing parts 52 and 54 formed in the respective blades 51. Since a movement of the rotary body 50 is regulated by annular members 55 and 56 fixed to the cover 32, the second deposit removing part 54 is arranged in a position capable of coming into contact with a part containing the introducing holes 40. The second deposit removing part 54 scrapes away and removes a deposit sticking to an inside surface of the cover 32 according to vibration of a vehicle and vibration of an engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor used in an internal combustion engine or the like, and more particularly, to an oxygen sensor having a cover for covering a sensor element and having an introduction hole through which a gas for detecting oxygen concentration can pass. About.

[0002]

2. Description of the Related Art Generally, in air-fuel ratio control of an internal combustion engine, the oxygen concentration of exhaust gas is detected by an oxygen sensor (exhaust-side oxygen sensor) provided in an exhaust passage, and an actual air-fuel ratio is calculated based on the oxygen concentration. Is done. Then, feedback control is performed so that the actual air-fuel ratio matches the target air-fuel ratio (normally, the stoichiometric air-fuel ratio).

In an internal combustion engine, an exhaust gas recirculation device (EGR device) for reducing NOx (nitrogen oxides) in exhaust gas, an exhaust gas and an air-fuel mixture leaking into a crankcase of the engine (blow-by gas, etc.) are used. ) May be provided with a blow-by gas reduction device (PCV device).

In an internal combustion engine provided with such an EGR device or a PCV device, the actual air-fuel ratio is set to the target air-fuel ratio because the oxygen concentration of the intake air changes due to changes in the EGR gas amount and the blow-by gas amount. It is difficult to accurately control the change.

Therefore, another oxygen sensor (intake-side oxygen sensor) is provided in the intake passage, and a method of detecting the oxygen concentration of the intake air including the influence of the EGR gas or the blow-by gas by the intake-side oxygen sensor is also taken. . In this way, the control accuracy in the above-described air-fuel ratio control can be improved by also referring to the oxygen concentration of the intake air.
By the way, each of the oxygen sensors is exhaust gas or EGR gas,
Since it is always exposed to the intake air containing the blow-by gas, the following problems cannot be ignored. That is, fine particles (hereinafter, referred to as “deposit”) composed of a mixture of carbon, engine oil, and the like are used for intake and exhaust.
This deposit may adhere to the sensor element of the oxygen sensor and the detection accuracy may be deteriorated.

For this reason, in the conventional oxygen sensor, the outer peripheral side of the sensor element is covered with a cover, and the intake / exhaust gas is introduced into the inside through an introduction hole formed in the cover, and then brought into contact with the surface of the sensor element. (For example,
"Oxygen sensor" described in JP-A-5-26842. ). Therefore, it is possible to prevent the flow of the intake and exhaust air from directly colliding with the surface of the sensor element, and it is possible to reduce the amount of deposit adhering to the surface.

[0007]

However, in the conventional oxygen sensor, although the deposition of the deposit on the sensor element is suppressed, a large amount of the deposit adheres to the cover. There is a problem that clogging of holes occurs. When such clogging of the introduction hole occurs, the detection accuracy of the oxygen sensor, particularly the responsiveness, may be deteriorated.

Particularly, in the above-described intake-side oxygen sensor, the temperature of the intake air passing through the intake passage is lower than the exhaust temperature, and the adhesiveness of the deposit tends to be relatively high. In such a situation, clogging of the introduction hole is more likely to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent an inlet hole formed in a cover of an oxygen sensor from being clogged by a deposit.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rod-shaped element for detecting the oxygen concentration of a gas, and a cylinder covering the rod-shaped element and having an introduction hole through which the gas can pass. In an oxygen sensor having a cover in the shape of, between the cover and the rod-shaped element, a rotating body rotatable around the axis of the rod-shaped element, at a portion including at least an introduction hole on the inner peripheral wall surface of the cover. The intent is to be provided so as to be able to abut.

[0011] According to the above configuration, the rotating body is rotated by, for example, vibration of the internal combustion engine or the like.
It comes into contact with the portion including the introduction hole on the inner peripheral wall surface of the cover. As a result, the deposit attached to the inner peripheral wall surface of the cover is scraped off by the rotating body and removed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in an oxygen sensor used in a vehicle diesel engine will be described with reference to FIGS.

FIG. 1 shows a schematic configuration of a diesel engine system according to this embodiment. As shown in FIG. 1, an intake pipe 12 and an exhaust pipe 14 are connected to a diesel engine (hereinafter simply referred to as “engine”) 11. The intake air taken into the intake pipe 12 via an air cleaner (not shown) passes through the pipe 12 to the engine 11.
Is introduced into a combustion chamber (not shown). A throttle valve 13 provided in the intake pipe 12 controls the amount of intake air introduced into the combustion chamber. In the combustion chamber, fuel injected from an injector (not shown) and intake air are mixed, and the air-fuel mixture burns, so that a driving force is obtained for the engine 11. The exhaust gas after the combustion is introduced into the exhaust pipe 14 from the combustion chamber,
After passing through a catalyst or the like (not shown), it is discharged outside.

The engine 11 includes an exhaust gas recirculation device (hereinafter, referred to as an exhaust gas recirculation device).
An “EGR device” 15 is provided. This E
The GR device 15 includes an EGR passage 16 that connects the exhaust pipe 14 and a portion of the intake pipe 12 downstream of the throttle valve 13, and a flow control valve 17 provided in the middle of the EGR passage 16.
And Part of the exhaust gas flowing through the exhaust pipe 14 (E
The GR gas passes through the EGR passage 16 and is introduced into the intake pipe 12. The flow control valve 17 is controlled by an electronic control unit (not shown) of the engine 11, so that the EGR
The amount of EGR gas passing through the passage 16 (EGR amount) is adjusted according to the opening degree.

Further, the engine 11 is provided with a blow-by gas reducing device (hereinafter, referred to as “PCV device”) 18. The PCV device 18 includes a pressure passage 19 that communicates the inside of a cylinder head cover (not shown) with a portion upstream of the throttle valve 13 in the intake pipe 12, and the throttle valve 13 in a crankcase (not shown) and the intake pipe 12. And a PCV passage 20 that communicates with a downstream portion. A flow control valve 21 is provided in the middle of the PCV passage 20. The flow control valve 21 is controlled by the electronic control unit to adjust the amount of blow-by gas (PCV amount) introduced into the intake pipe 12 from the inside of the crankcase through the PCV passage 20 according to the opening degree.

In the intake pipe 12, the EGR passage 16 and the P
An oxygen sensor 30 is mounted at a position downstream of each opening of the CV passage 20. The oxygen sensor 30
An oxygen concentration of the intake air including the EGR gas and the blow-by gas is detected, and a detection signal is output to the electronic control unit. The electronic control unit performs EGR amount feedback control of the engine 11 and P P based on the detection signal from the oxygen sensor 30.
The CV amount feedback control is performed.

FIG. 2 is a sectional view showing a tip side portion of the oxygen sensor 30, and FIG. 3 is a sectional view taken along line 3-3 in FIG.
As shown in these drawings, the oxygen sensor 30 has a bottomed cylindrical sensor element 31 having a pair of electrodes (not shown).
And a cover 32 provided so as to cover the outer periphery of the sensor element 31, and a housing 33 for fixing the sensor element 31 and the cover 32. Sensor element 31
Has a portion for detecting the oxygen concentration at the tip side, and outputs a signal corresponding to the oxygen concentration of the intake air coming into contact with the same from each electrode.

A heater 34 is provided inside the sensor element 31. The heater 34 has a function of activating the sensor element 31 by heating the sensor element 31 to increase the temperature to 650 to 700 ° C.

The oxygen sensor 30 is mounted so that the housing 33 is fixed to the intake pipe 12 so that the tip side (the lower side in the figure) protrudes into the pipe 12. By attaching the oxygen sensor 30 to the intake pipe 12 as described above, the intake air flowing through the pipe 12 collides with the side of the cover 32.

The cover 32 is made of stainless steel (for example, SUS310S, SUS43) having excellent heat resistance and corrosion resistance.
0) to form a bottomed cylinder. A plurality of introduction holes 40 for introducing intake air into the inside of the cover 32 are formed in the side portion. As shown in FIG. 3, each introduction hole 40 is substantially 90 ° around the axis of the sensor element 31.
They are arranged at intervals. Cover 3 through introduction hole 40
The intake air introduced into 2 comes into contact with the tip side portion of sensor element 31.

The bottom of the cover 32 has a function of introducing intake air into the inside thereof similarly to the introduction hole 40, and a deposit discharge hole 41 for discharging the deposit removed by the rotating body 50 described later to the outside. Are formed.

In the present embodiment, between the sensor element 31 and the cover 32, there is provided a rotating body 50 for removing the deposit attached to the cover 32 and the sensor element 31. The rotating body 50 includes four blades 51 arranged at 90 ° intervals about the axis of the sensor element 31.
It has. Each of the blades 51 is formed of a stainless material, similarly to the cover 32. An inner peripheral side portion (a portion on the sensor element 31 side) of each blade 51 is a first deposit removing portion 52 for scraping off a deposit attached to an outer peripheral surface of the sensor element 31. As shown in FIG. 2, the first deposit removing section 52 is formed in a shape having a minute constant gap with the outer peripheral surface of the sensor element 31.

The outer peripheral portion of each blade 51 (cover 3)
A semicircular cutout 53 is formed at the center of the sensor element 31 in the axial direction of the sensor element 31. By forming the notch 53 in each blade 51 in this manner, the weight of the rotating body 50 is reduced. Further, the upper and lower portions of the notch 53 in the outer peripheral portion of each blade 51 serve as a second deposit removing portion 54 for scraping off the deposit attached to the inner peripheral surface of the cover 32. A minute gap is formed between the second deposit removing portion 54 and the inner peripheral surface of the cover 32.

A pair of annular members 55 and 56 are fixed to the inner peripheral surface of the cover 32 at positions above and below the rotating body 50. The position change of the rotating body 50 in the axial direction is restricted by the annular members 55 and 56, so that the second deposit removing section 54 is formed in the portion where the introduction hole 40 of the cover 32 is formed in the axial direction of the sensor element 32. It is arranged at a position where it can face. In addition, each of the annular members 55, 5
A minute gap is formed between 6 and rotating body 50, and rotating body 50 is rotatable about the axis of sensor element 32.

Next, the operation and effects of this embodiment will be described. According to the present embodiment, the vehicle 50 and the vibrations associated with the operation of the engine 11 are transmitted to the oxygen sensor 30, so that the rotator 50 is attached to each of the deposit removing units 52 and 5.
4 rotates irregularly around the axis of the sensor element 31 while repeatedly contacting the outer peripheral surface of the sensor element 31 or the inner peripheral surface of the cover 32. As a result, the deposit attached to the outer peripheral surface of the sensor element 31 is scraped off and removed by each first deposit removing unit 52. Therefore, it is possible to suppress the detection accuracy of the oxygen sensor 30 from being lowered due to the deposit adhering to the outer peripheral surface of the sensor element 31.

Further, according to the present embodiment, the deposit adhered to the inner peripheral surface of the cover 32 is removed by the second deposit removing section 5.
4 to be scraped off and removed. Thus, cover 3
As the deposit attached to the inner peripheral surface of No. 2 is removed, the deposit deposited on the inner peripheral wall surface of the introduction hole 40 is also removed at the same time. As a result, according to the present embodiment, clogging of the introduction hole 40 due to the deposit can be suppressed, and good detection accuracy of the oxygen sensor 30, particularly good responsiveness, can be secured. The deposit removed from the sensor element 31 and the cover 32 as described above is discharged outside through the deposit discharge hole 41.

Further, in this embodiment, since the rotating body 50 is made of stainless steel having a high thermal conductivity, the heat of the sensor element 31 which has been heated by the heater 34 and whose temperature has risen passes through the rotating body 50. It is transmitted to the cover 32 efficiently. As a result, the temperature of the cover 32 becomes higher.
Since the deposit usually tends to start burning at a temperature of 400 to 500 ° C., according to this embodiment, the cover 3
The deposit adhering to 2 loses its stickiness by burning and is removed from the cover 32. As a result, clogging of the introduction hole 40 by the deposit can be further suppressed in addition to the mechanical deposit removing action by the rotating body 50.

Further, according to the present embodiment, the rotation of the rotating body 50 inside the cover 32 causes the cover 32 to rotate.
The movement of intake air between the inside and the outside of the vehicle is promoted.
Therefore, according to the present embodiment, the responsiveness of the oxygen sensor 30 can be further improved, and the detection signal from the oxygen sensor 30 can quickly follow the change in the oxygen concentration of the intake air.

Next, the results of a durability test performed to confirm the effects of the present embodiment will be described. The conditions of this durability test are shown below. Engine speed: 1200 rpm EGR amount: 15% PCV amount: 10 ml / Hr in PCV passage 20
In the endurance test, the sensor response time of the oxygen sensor 30 of the present embodiment and the sensor response time of the conventional oxygen sensor without the rotating body 50 when the vehicle was actually run were determined. Was measured every 50 hours. Here, when the oxygen concentration of the intake air is increased from 15% to 20%, the sensor response time corresponds to 63% of a specified current value (a current value corresponding to an oxygen concentration of 20%) from the increase. This is the time until a current is output from the oxygen sensor 30.

FIG. 4 is a graph showing the results of the durability test. As shown in the figure, in the conventional oxygen sensor, the introduction hole 40 is clogged by the deposit, and the opening area of the introduction hole 40 gradually decreases with time, so that the sensor response time greatly increases. You can see that

On the other hand, in the oxygen sensor 30 according to the present embodiment, the increase in the sensor response time is extremely small even after 200 hours have elapsed from the start of the test, and good response is ensured. Recognize. As is clear from the above test results, according to the present embodiment, the oxygen sensor 3
Good response at 0 can be ensured.

The configuration of the above-described embodiment can be changed as in another embodiment described below. According to these other embodiments, substantially the same functions and effects as those of the above embodiment can be obtained.

The rotating body 50 is made of 4
In addition to the shape having the three blades 51, for example, as shown in FIG. 6 which is a cross-sectional view taken along line 6-6 in FIG. It may have a shape having two blades 51.

In the above embodiment, the rotating body 50 has the function of removing the deposits on both the sensor element 31 and the cover 32, but the second deposit removing section 54
Accordingly, if only the deposit attached to the cover 32 is removed, good detection accuracy of the oxygen sensor 30 can be ensured.

As shown in FIG. 7, the rotating body 50 is made of a tubular material having a long hole cross section. A pair of openings 57 for introducing intake air into the rotator 50 are formed on the side of the rotator 50, and the upper and lower portions of each of the openings 57 constitute a second deposit removal unit 54. FIG. 8 shows this rotating body 50.
9 is a cross-sectional view showing a state where it is arranged inside the cover 32, and FIG. 9 is a cross-sectional view showing a cross section along line 9-9 in FIG. The major axis L of the rotating body 50 is set slightly smaller than the inner diameter D of the cover 32 so that a minute gap is formed between both sides of the rotating body 50 and the inner peripheral surface of the cover 32. The intake air introduced into the cover 32 through the introduction hole 40 contacts the outer peripheral surface of the sensor element 31 through each opening 57.

According to such a configuration, the sensor element 31
The deposits adhered to the surface of the rotating body 50 are scraped off and removed when the inner peripheral wall of the rotating body 50 comes into contact with the element 31. Also,
The deposit attached to the inner surface of the cover 32 is scraped off and removed by the second deposit removing unit 54.

The cross-sectional shape of the rotating body 50 is not limited to the shape shown in FIG. 9, but may be, for example, a shape shown in FIG. 10 or FIG. In the above embodiment, the present invention is applied to the diesel engine 11
The present invention has been embodied in an oxygen sensor 30 attached to the intake pipe 12 of FIG. In contrast, the present invention relates to a diesel engine 11
, Or an oxygen sensor attached to an intake pipe or an exhaust pipe of a gasoline engine. Further, the present invention is not limited to an engine, but may be applied to an oxygen sensor used in various combustion devices.

In the above embodiment, the present invention is embodied in the oxygen sensor 30 used in the engine 11 having both the EGR device 15 and the PCV device 18.
The present invention can also be embodied in an oxygen sensor used in an engine having only one of 5, 18.

The technical ideas that can be grasped from the above embodiments will be described below together with their effects. (1) In the oxygen sensor according to the first aspect, the sensor is attached to an intake pipe of an internal combustion engine provided with an exhaust gas recirculation device or a blow-by gas reduction device.

As described above, in the oxygen sensor attached to the intake pipe of the internal combustion engine, since the temperature of the intake air is relatively low and the adhesion of the deposit is high as described above, the deposit tends to adhere to the cover. There is. The above (a)
The configuration described in (1) is suitable in the oxygen sensor having the above tendency in that the deposition of deposit is suppressed.

[0041]

According to the present invention, a rotating body rotatable about the axis of the rod-shaped element is provided between the cover and the rod-shaped element at a portion including at least the introduction hole on the inner peripheral wall surface of the cover. It is designed to be accessible. Therefore, when the rotating body rotates due to, for example, vibration of the internal combustion engine, the deposit attached to the portion including the introduction hole on the inner peripheral wall surface of the cover is removed. As a result, according to the present invention, clogging of the introduction hole due to the deposit can be suppressed, and good detection accuracy of the oxygen sensor can be secured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an intake and exhaust system of a diesel engine according to an embodiment.

FIG. 2 is a cross-sectional view showing a tip portion of the oxygen sensor.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a graph showing a result of a durability test for confirming an effect in one embodiment.

FIG. 5 is a cross-sectional view showing a tip portion of an oxygen sensor according to another embodiment.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;

FIG. 7 is a perspective view showing a rotating body according to another embodiment.

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

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is a sectional view showing the shape of a rotating body according to another embodiment.

FIG. 11 is a sectional view showing the shape of a rotating body according to another embodiment.

[Explanation of symbols]

30 ... oxygen sensor, 31 ... sensor element, 32 ... cover,
40 ... Introduction hole, 50 ... Rotating body.

Claims (1)

[Claims] 1. An oxygen sensor comprising: a rod-shaped element for detecting the oxygen concentration of a gas; and a cylindrical cover that covers the rod-shaped element and has an introduction hole through which the gas can pass. A rotating body rotatable around the axis of the rod-shaped element is provided between the rod-shaped element and the rod-shaped element so as to be able to contact at least a portion including the introduction hole on the inner peripheral wall surface of the cover. Oxygen sensor.