JP2013044270A - Structure for preventing water from adhering to gas sensor of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a gas sensor from being cracked due to water adhesion, by making a water droplet hardly get into an auxiliary chamber and preventing the water droplet from directly colliding with the gas sensor, because the water droplet mixed into intake air flowing through an intake passage flows together with a mainstream by providing the outward-protruding auxiliary chamber on the wall surface of the intake passage and arranging the gas sensor in the auxiliary chamber.SOLUTION: A structure for preventing water adhesion prevents the water droplet, which is mixed into the intake air, from adhering to an A/F sensor which is attached to the intake passage 62a of an engine 10. The structure for preventing the water adhesion includes the auxiliary chamber 63 which continues into an opening 63a provided on the passage wall surface 62b forming the intake passage 62a and which protrudes to the outside of the passage wall surface 62b, and an air-fuel ratio sensor 58 which is arranged in the auxiliary chamber 63. An inclined surface 63c, which is formed by inclining the passage wall surface toward the inside of the auxiliary chamber, is provided in the inlet part of the opening 63a to guide the intake air, which flows through the intake passage 62a, into the auxiliary chamber 63.

Description

  The present invention relates to a gas sensor wet prevention structure for an internal combustion engine that can prevent water droplets mixed in intake air from adhering to a gas sensor attached to an intake passage of the internal combustion engine with simple means.

Recent internal combustion engines are equipped with an EGR device that recirculates part of the exhaust gas to the intake passage as an exhaust gas purification device, a supercharger that pressurizes the intake air to increase combustion efficiency, and controls the fuel injection amount and injection timing. By controlling, it has become possible to improve the output and minimize the generation of NOx and smoke.
Further, in a diesel engine and other internal combustion engines, an intercooler is provided in the intake passage in order to improve the output by lowering the intake air temperature and increasing the intake mass per unit volume. However, if the intake air is cooled too much by the intercooler, condensed water is generated from the intake air on the outlet side of the intercooler.

When this condensed water collides with a sensor element such as a gas sensor provided in the downstream side intake pipe, the sensor may be damaged due to element cracking. That is, since the sensor element is heated by the heater, there is a possibility that cracking may occur due to thermal shock when a water droplet collides.
In addition, when a large amount of condensed water enters the cylinder, a steam explosion may occur, and the cylinder components may be damaged.
Since the exhaust gas contains water vapor generated by the combustion of the fuel, the amount of water vapor contained is greater than that of the intake air. In an internal combustion engine equipped with an EGR device, a part of the exhaust gas is introduced into the intake pipe, so that the intercooler Condensed water is more likely to be generated when cooled in

Japanese Patent Laid-Open No. 2007-321593 (Patent Document 1) describes the inside of an exhaust pipe in order to reduce the adhesion of condensed water in exhaust gas to an A / F sensor attached to an exhaust pipe extending in a substantially horizontal direction. The structure provided with the baffle plate for rectifying | straightening a part of waste gas to an acute angle with respect to the said A / F sensor in the upstream of the A / F sensor in FIG.
Since a part of the exhaust gas is rectified at an acute angle with respect to the A / F sensor by this rectifying plate, the probability that condensed water adheres to the A / F sensor is reduced. In addition, a technique is disclosed in which condensed water adhering to the current plate is urged to fall and is easily removed from the A / F sensor at an early stage.

  Japanese Patent Application Laid-Open No. 2003-65171 (Patent Document 2) includes an A / F sensor mounting portion that is depressed toward the inside of the surge tank and that protrudes into the internal space. The A / F sensor is assembled so as to be accommodated in the housing. An annular convex portion is provided on the bottom surface of the A / F sensor mounting portion to block oil and moisture flowing along the wall surface of the surge tank.

JP 2007-321593 A JP 2003-65171 A

  In Patent Document 1, in order to reduce water exposure of the A / F sensor, a rectifying plate is provided on the upstream side of the A / F sensor, and condensed water mixed in the exhaust gas adheres to the A / F sensor. Probability is further reduced, and the condensed water adhering to the water is urged to fall and is removed from the A / F sensor at an early stage to reduce the adhesion of condensed water, but the lower part of the A / F sensor is always directly in the mainstream of the exhaust gas. There is still a problem that the condensed water adheres to the A / F sensor.

  Further, in Patent Document 2, an annular convex portion is provided on the bottom surface of the A / F sensor mounting portion to block oil and moisture flowing along the wall surface of the surge tank, but the lower portion of the A / F sensor is an annular convex portion. The oil or moisture that flows along the wall of the surge tank may fall from the annular convex part and ride on the intake gas and adhere to the lower part of the A / F sensor. Furthermore, since the lower part of the A / F sensor is always directly exposed to the main stream of intake air, there still remains a problem that condensed water adheres to the A / F sensor.

  In view of the problems of the prior art, the present invention provides a sub chamber protruding outward on the wall surface of the intake passage, and disposing a gas sensor in the sub chamber, so that water droplets mixed in the intake air flowing through the intake passage are directly applied to the gas sensor. The object is to prevent collision and prevent cracking of the gas sensor.

  In order to achieve such an object, the present invention provides a water passage prevention wall structure for preventing water droplets mixed in intake air from adhering to a gas sensor attached to an intake passage of an internal combustion engine. The sub-chamber is formed so as to project outward from the wall surface of the passage continuously to the opening provided in the sub-chamber, and a gas sensor disposed in the sub-chamber.

  According to this invention, since the gas sensor is arranged in the sub chamber protruding outward from the wall surface of the passage continuously with the opening provided on the wall surface of the passage forming the intake passage, water droplets mixed in the intake air flowing through the intake passage Since it flows along the mainstream, it is difficult for water droplets to enter the sub chamber and it is possible to prevent water droplets from directly colliding with the gas sensor.

  In the present invention, it is preferable that an inclined surface having a passage wall surface inclined toward the sub chamber is provided at the inlet of the opening so as to guide the intake air flowing through the intake passage into the sub chamber.

  As described above, since the inclined surface is formed by inclining the passage wall surface toward the sub-chamber side at the entrance of the opening so as to guide the intake air flowing through the intake passage into the sub-chamber, the intake air easily enters the sub-chamber, Misdetection of gas sensor and response delay can be avoided.

  In the present invention, it is preferable that the inclined surface is formed so that an extended line of the inclined surface is positioned on the intake passage side with respect to the gas sensor.

  In this way, the inclined surface is formed so that the extended line of the inclined surface is located on the intake passage side with respect to the gas sensor, so that water droplets mixed in the introduced intake air do not directly collide with the gas sensor. Can do.

  Preferably, in the present invention, the inclined surface is formed at an inclined surface angle so that an angle formed by an extension line of the inclined surface and a tangent line of the sub chamber wall intersecting the extension line is an obtuse angle. Good.

  In this way, the angle formed between the extension line of the inclined surface and the tangent line of the sub chamber wall intersecting with the extension line is an obtuse angle, so that water droplets mixed in the intake air introduced into the sub chamber are So that it flows along the wall surface of the sub chamber without rebounding toward the gas sensor.

  In the present invention, preferably, the sub chamber has an annular wall surface for swirling the intake air introduced into the sub chamber, and the gas sensor is arranged at the center of the swirl flow flowing along the annular wall surface. It is good to arrange | position along the axis line.

  By adopting such a configuration, by making the wall surface of the sub chamber an annular wall surface, the intake air is swirled, and the water droplets mixed in the intake air are utilized in a large specific gravity. It is possible to effectively prevent the water droplet from colliding with the gas sensor by being captured by the wall surface.

  In the present invention, it is preferable that a discharge portion for discharging water droplets trapped by the sub chamber wall surface to the outside of the sub chamber is provided on the lower side of the sub chamber in the gravity direction.

By adopting such a configuration, by providing the sub chamber wall surface below the gravitational direction, water droplets adhering to the sub chamber wall surface are swirled and discharged outside the sub chamber, so that water droplets enter the sub chamber chamber. I can not.
In addition, when the flow of the intake air stops after the engine is stopped and the sub-chamber swirling flow is not generated, the sub-chamber is provided with an inclination (θ3). It can be discharged without contact.

According to the present invention, since the gas sensor is arranged in the sub chamber protruding outward from the passage wall surface continuously to the opening provided in the passage wall surface forming the intake passage, water droplets mixed in the intake air flowing through the intake passage Since it flows along the mainstream, it is difficult for water droplets to enter the sub chamber and it is possible to prevent water droplets from directly colliding with the gas sensor.
In addition, since an inclined surface with the passage wall surface inclined toward the sub-chamber side is provided at the entrance of the opening so as to guide the intake air flowing through the intake passage into the sub-chamber, the intake air easily enters the sub-chamber. False detection and response delay can also be avoided.
Furthermore, by rotating the intake air and utilizing the high specific gravity of the water droplets mixed in the intake air, it is possible to effectively prevent the water droplets from colliding with the gas sensor by capturing the water droplets on the wall surface of the sub chamber. it can.
In addition, when the flow of the intake air stops after the engine is stopped and the sub-chamber swirling flow is not generated, the sub-chamber is provided with an inclination (θ3). It can be discharged without contact.

1 is an overall configuration diagram in which the present invention is applied to a diesel engine mounted on a vehicle. The AA sectional view of Drawing 1 in a 1st embodiment of the present invention is shown. (A) shows the partial enlarged detail view of the Y part of FIG. 2, (B) shows the X arrow directional view of (A). (A) shows the elements on larger scale of Y section of Drawing 2 in the 2nd embodiment of the present invention, and (B) shows the AA sectional view of (A).

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

  The whole structure which applied this invention to the diesel engine mounted in the vehicle is demonstrated based on FIGS. 1-2. In the diesel engine 10 of the present embodiment shown in FIG. 1, a cylinder head 14 is provided on the cylinder block 12. The cylinder head 14 is provided with a fuel injection device 16 at the center of the combustion chamber 15 (center of each cylinder) formed by the piston 13 and the cylinder head 14 that reciprocate in the cylinder block 12. On both sides of the device 16, an intake air introduction part and an exhaust gas discharge part are provided. The intake air introduction portion is connected to the second intake pipe 18 via the intake manifold 17, and the exhaust gas discharge portion is connected to the exhaust pipe 20 via the exhaust manifold 19.

  A supercharger 22 including a compressor provided in the second intake pipe 18 and an exhaust turbine provided in the first exhaust pipe 20 is provided in the middle of the second intake pipe 18 and the first exhaust pipe 20. The second exhaust pipe 21 downstream of the supercharger 22 is provided with an exhaust gas purification device 24 having a diesel particulate filter. A high-pressure EGR pipe 26 connecting the first exhaust pipe 20 upstream of the supercharger 22 and the second intake pipe 18 downstream of the supercharger 22, and the high-pressure EGR pipe 26, purify EGR gas. There is provided a high pressure EGR device 32 including a catalyst device 28 that performs the above operation and a high pressure EGR valve 30 that is provided at the outlet of the high pressure EGR pipe 26 and that can adjust the flow rate of the EGR gas flowing through the high pressure EGR pipe 26.

  A low pressure EGR pipe 34 that connects the second exhaust pipe 21 downstream of the supercharger 22 and the first intake pipe 23 upstream of the supercharger 22, A low-pressure EGR device 38 comprising a low-pressure EGR cooler 36 interposed in the EGR pipe 34 and a low-pressure EGR valve 37 provided at the outlet of the EGR pipe 34 and capable of adjusting the flow rate of EGR gas flowing through the low-pressure EGR pipe 34. Is provided.

  An intercooler 40 for cooling the intake air is provided in the second intake pipe 18 on the downstream side of the supercharger 22. An inlet 23 a of the first intake pipe 23 on the upstream side is provided with a filter device 42 and an air flow sensor 44, an intake air temperature sensor 46, and an intake humidity sensor 48 that detect the intake air flow rate on the downstream side of the filter device 42. . Further, intake throttle valves 50 and 52 for adjusting the amount of intake air sucked into the cylinder are provided in the first intake pipe 23 on the downstream side of these sensors and the second intake pipe 18 on the downstream side of the intercooler. Each intake manifold 17 is provided with an intake temperature sensor 54, a boost sensor 56 that detects intake pressure, and an A / F sensor 58.

  At the start of operation of the diesel engine 10, the exhaust turbine of the supercharger 22 is driven by the exhaust gas e, and the air is sucked into the first intake pipe 23 on the upstream side by the compressor of the supercharger 22. Also, detection signals are input to the ECU 60 from the sensors. In accordance with these detection signals, the ECU 60 performs a shutter device (not shown) and an electric fan (not shown) provided in the intake throttle valves 50 and 52, the EGR valves 30 and 36, the fuel injection device 16, and the intercooler 40. Control etc.

In such a configuration, during medium and low loads, a large amount of exhaust gas is recirculated to the second intake pipe 18 by the high pressure EGR device 32 to reduce the amount of NOx in the exhaust gas. When the load is high, a small amount of exhaust gas is recirculated from the low-pressure EGR device 38 to the second intake pipe 18 with relatively high accuracy to reduce the amount of NOx in the exhaust gas. Further, intake air temperature sensors 46 and 54 provided in the second intake pipe 18 and an air-fuel ratio sensor 58 (hereinafter referred to as an A / F sensor) which is one of gas sensors, new intake air and EGR gas introduced into the cylinder The mixed gas temperature and O ₂ concentration are detected, and these detection signals are input to the ECU 60. The ECU 60 controls the supercharging pressure, the EGR gas amount introduced from the low pressure EGR device 38 and the high pressure EGR device 32, the fuel injection amount of the fuel injection device 16, and the injection timing in accordance with these detection signals. Thereby, the amount of NOx in the exhaust gas can be minimized. The supercharging pressure is adjusted by adjusting the angle of the variable vane of the supercharger provided with the variable vane, or adjusting the opening degree of the wastegate of the supercharger provided with the waste gate.

  The amount of water vapor Wm that can be contained in the intake air is affected by the pressure and temperature of the intake air a. For example, the amount Wm of intake water increases when the pressure of the intake air a decreases, and decreases when the pressure of the intake air a increases. Further, the temperature decreases when the temperature of the intake air a is low, and increases when the temperature of the intake air a is high. In addition, the temperature has a larger effect on the water vapor content Wm than the pressure.

Therefore, since water is generated when the fuel burns, the water vapor content Wm of the EGR gas is greater than fresh air. Further, since the temperature of the EGR gas is high, the water vapor-containing amount Wm is greater than that of fresh air. Accordingly, the amount of water vapor in the intake air a after the EGR gas is mixed is the sum of the amount of water vapor contained in the fresh air and the EGR gas. After being supercharged by the supercharger 22, the pressure of the intake air a rises, but the temperature also rises, so that the possible water vapor content Wm slightly increases. Thereafter, when the intake air a is cooled by the intercooler 40A, the water vapor content Wm is reduced, and the difference between the water vapor content Wm and the water vapor content Wm becomes the condensed water generation amount Wn.
In this way, the condensed water generated during the intake air passes through the surge tank 62 that forms the intake passage 62a together with the intake air a, and is sucked from the intake manifold 17 into the combustion chamber. These condensed waters adhere to the A / F sensor 58 and the like.

(First embodiment)
A first embodiment of the gas sensor wet prevention structure according to the present invention will be described with reference to FIGS.
3A is a partially enlarged view of a Y portion in FIG. 2, and FIG. 3B is a view taken in the direction of arrow X in FIG.
The intake air a enters the intake manifold 17 through the intake passage 62a of the surge tank 62 from the direction of the arrow Z (from the lower side to the upper side in the direction of gravity), and is sucked into the combustion chambers 15 of the engine 10 from the branch pipes 17a of the intake manifold 17. The

An opening 63a is disposed in the passage wall surface 62b that forms the intake passage 62a, and the space 63s is formed by a cylindrical (annular) sub chamber wall surface 63b that protrudes outward from the intake passage 62a continuously to the opening 63a. A sub chamber 63 is formed in which the central axis CL of the cylindrical space 63s is horizontal.
The A / F sensor 58 is disposed in the vicinity of the cylindrical central axis CL along the central axis CL.

On the upstream side of the intake passage 62a of the opening 63a, an introduction inclined surface 63c that facilitates introduction of the intake air a into the space 63s is formed.
The inclination angle θ1 of the introduction inclined surface 63c is such that the angle θ2 formed by the extension line L1 of the introduction inclination surface 63c and the tangent to the portion P1 where the extension line L1 intersects the sub chamber wall surface 63b becomes an obtuse angle. The inclination angle of 63c is adjusted.
This is to prevent water droplets mixed in the introduced intake air a from colliding with the sub chamber wall surface 63b and splashing water droplets from adhering to the A / F sensor 58.
Further, the extension line L1 of the inclination angle θ1 is prevented from contacting the A / F sensor 58, and the A / F sensor 58 is positioned on the opposite side of the intake passage 62a with respect to the extension line L1. Has been placed.

With this arrangement, the introduced intake air a does not directly collide with the A / F sensor 58, and the A / F sensor 58 is effectively prevented from getting wet.
FIG. 3B shows a view taken in the direction of the arrow X in FIG. 3A, and the A / F sensor 58 is disposed in a state of being directed from the side wall surface 63e of the sub chamber 63 in the horizontal direction.
And the front-end | tip part 58a of the A / F sensor 58 is arrange | positioned with a clearance gap with respect to the opposite side wall surface 63f.

Further, an upstream side of the intake passage 62a of the opening 63a is formed with a discharge inclined surface 63d that is inclined to the upstream side (lower side in the direction of gravity) of the intake passage 62a.
On the discharge inclined surface 63d, water droplets adhering to the sub chamber wall surface 63b are pushed by the flow of the intake air a to reach the discharge inclined surface 63d of the space 63s, and again the water droplets come from the discharge inclined surface 63d with the intake air a. It returns to the intake passage 62a.

With such a structure, the intake air a flowing through the intake passage 62a is introduced into the space 63s along the introduction inclined surface 63c, rotates circumferentially along the cylindrical sub-chamber wall surface 63b, and has a specific gravity. Large water droplets adhere to the sub chamber wall 63b due to centrifugal force, and the water droplets of the intake air a are separated, so that the water droplets can be prevented from directly colliding with the A / F sensor 58.
Further, the water droplets adhering to the sub chamber wall surface 63b are pushed by the flow of the intake air a, travel along the discharge inclined surface 63d, and return to the intake passage 62a.
The intake air a in the space portion 63s is accelerated in the space portion 63s, and water droplets on the accelerated intake air a have a large specific gravity, so that they easily enter the intake passage 62a and enter the sub chamber 63 again. Without entering, it is possible to more effectively prevent the A / F sensor 58 from getting wet.
In addition, when the flow of the intake air stops after the engine is stopped and the sub-chamber swirling flow is not generated, the sub-chamber is provided with an inclination (θ3). It can be discharged without contact.

(Second Embodiment)
A second embodiment of the present invention will be described based on FIGS. 4 (A) and 4 (B).
In the second embodiment, the flow direction of the intake air a is the same as that in the first embodiment, while the flow in the horizontal direction is the same as in the first embodiment. The same parts are denoted by the same reference numerals, and description thereof is omitted.

4A shows a partially enlarged detail view of the Y portion in FIG. 2, and FIG. 4B shows a cross section taken along the line AA in FIG.
The intake air a enters the intake manifold 17 through the intake passage 62a of the surge tank 62 from the Z arrow (horizontal direction), and is sucked into the combustion chambers 15 of the engine 10 from the branch pipes 17a of the intake manifold 17.
An A / F sensor 58 is disposed at the center of the sub chamber 65. A / F sensor 58
As shown in FIG. 4 (B), it is mounted from the upper side (gravity direction) in the sub chamber 65 toward the lower side.

As shown in FIG. 4A, the intake air a flows through the intake passage 62a in a substantially horizontal direction. Intake a flows from the direction of arrow Z.
An opening 65a is disposed in the passage wall surface 62b that forms the intake passage 62a, and the space portion 65s is formed by a cylindrical (annular) sub chamber wall surface 65b that protrudes outward from the intake passage 62a continuously to the opening 65a. A sub-chamber 65 is formed in which the central axis CL of the cylindrical space 65s is substantially horizontal.

An introduction inclined surface 65c that facilitates introduction of the intake air a into the space 65s is formed on the upstream side of the intake passage 62a of the opening 65a.
The A / F sensor 58 is disposed in the vicinity of the cylindrical central axis CL along the central axis CL.
The inclination angle θ1 of the introduction inclined surface 65c is adjusted such that the angle θ2 formed by the extension line L1 of the introduction inclination surface 65c and the tangent line of the portion P1 where the extension line L1 intersects the sub chamber wall surface 65b becomes an obtuse angle. .
This is to prevent water droplets mixed in the introduced intake air a from colliding with the sub chamber wall surface 65 b and preventing the splashed water droplets from adhering to the A / F sensor 58.
Further, the extension line L1 of the inclination angle θ1 is prevented from contacting the A / F sensor 58, and the A / F sensor 58 is positioned on the opposite side of the intake passage 62a with respect to the extension line L1. Has been placed.

With this arrangement, the introduced intake air a does not directly collide with the A / F sensor 58, and the A / F sensor 58 is effectively prevented from getting wet.
4B shows a cross section taken along the line AA of FIG. 4A, and the A / F sensor 58 is arranged in a state where it hangs downward (in the direction of gravity) from the upper wall surface 65e of the sub chamber 65. Yes.
And the front-end | tip part 58a of A / F sensor 58 has a clearance gap with respect to the lower wall surface 65d.
Further, the lower wall surface 65d is a surface inclined downward with respect to the intake passage 62a, so that water droplets adhering to the sub chamber wall surface 63b flow downward, travel along the inclined lower wall surface 65d, and flow to the intake passage 62a. ing.
In addition, when the flow of the intake air stops after the engine is stopped and the sub-chamber swirling flow is not generated, the sub-chamber is provided with an inclination (θ3). It can be discharged without contact.

With such a structure, the intake air a flowing through the intake passage 62a is introduced into the space 65s along the introduction inclined surface 65c, rotates along the circumference of the cylindrical sub chamber wall surface 65b, and has a specific gravity. Large water droplets adhere to the sub chamber wall 63b due to centrifugal force, and the water droplets of the intake air a are separated, so that the A / F sensor 58 can be prevented from being wet.
Further, the water droplets adhering to the sub chamber wall surface 65b flow downward due to gravity, and flow along the lower wall surface 65d to the intake passage 62a.
Further, when the flow of the intake air stops after the engine is stopped and the swirling flow in the sub chamber no longer occurs, the inclination (θ3) is provided in the sub chamber, so that water droplets remaining in the sub chamber after the engine is stopped It can be discharged without contact.
Thereby, the separated water droplet does not enter the sub chamber 65 again due to the flow of the intake air a, and the A / F sensor 58 can be more effectively prevented from being wet.

  It can be used as a moisture prevention structure for preventing a gas sensor attached to an intake or exhaust passage of an internal combustion engine from getting wet and being damaged.

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Cylinder block 14 Cylinder head 16 Fuel-injection apparatus 17 Intake manifold 18 2nd intake pipe 19 Exhaust manifold 20 Exhaust pipe 22 Supercharger 23 1st intake pipe 24 Exhaust gas purification apparatus 32 High pressure EGR apparatus
38 Low pressure EGR device 40 Intercooler
44 Air flow sensor 50, 52 Intake throttle valve 58 A / F sensor (gas sensor)
60 ECU
62 Surge tank 62a Intake passage 63, 65 Sub chamber 63a, 65a Opening 63b, 65b Sub chamber wall 63c, 65c Introducing inclined surface
a Intake e Exhaust gas

Claims (6)

  A sub-chamber formed to project outward from the wall surface of the gas sensor attached to the intake passage of the internal combustion engine in a structure for preventing water exposure of the gas sensor. And a gas sensor wetting prevention structure for an internal combustion engine, comprising: a gas sensor disposed in the sub chamber.   2. A gas sensor for an internal combustion engine according to claim 1, wherein an inclined surface is formed by inclining a passage wall surface toward the auxiliary chamber side at an inlet of the opening so as to guide intake air flowing through the intake passage into the auxiliary chamber. Water-proof structure.   The gas sensor wetting prevention structure for an internal combustion engine according to claim 2, wherein the inclined surface is formed such that an extended line of the inclined surface is positioned on the intake passage side with respect to the gas sensor.   The inclined surface is formed at an inclined surface angle so that an angle formed by an extension line of the inclined surface and a tangent line of a sub chamber wall intersecting the extended line is an obtuse angle. 4. A structure for preventing gas sensor water in an internal combustion engine according to 3.   The sub chamber has an annular wall surface that swirls the intake air introduced into the sub chamber, and the gas sensor is disposed along the axis of the swirl flow at the center of the swirl flow that flows along the annular wall surface. 5. The gas sensor wetting prevention structure for an internal combustion engine according to claim 1, wherein:   6. The sub-chamber wall surface is provided with a discharge portion for discharging water trapped on the sub-chamber wall surface to the outside of the sub-chamber, on the lower side in the gravity direction of the sub-chamber. The gas sensor moisture prevention structure for an internal combustion engine according to any one of the preceding claims.

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