JP5769077B2 - Gas sensor wet prevention device - Google Patents

Description

  The present invention relates to a water sensor for a water sensor for a gas sensor provided in an intake pipe of an internal combustion engine, and more specifically, condensed water generated inside an intake pipe having an intake downstream side located above flows down and adheres to a detection unit. The present invention relates to an apparatus for preventing damage to the detection unit.

In an internal combustion engine such as a diesel engine or a gasoline engine, a sensor for detecting a specific gas component in the intake air is provided in an intake pipe or an exhaust pipe. Such sensors, for example, using a gas detecting element comprising a solid electrolyte such as zirconia, and the air-fuel ratio sensor for detecting the O ₂ concentration, there is a NO _X sensor for detecting the concentration of NO _X in the exhaust gas. The detectors incorporating the gas detection elements of these sensors are arranged so as to project into the intake or exhaust flow path, and detect the specific gas component when the gas detection elements are exposed to the intake or exhaust.

  Since the intake or exhaust contains water vapor, condensed water is generated when the temperature of the intake or exhaust decreases, such as after the engine is stopped. Since the gas detection element of the sensor is made of ceramic that is vulnerable to thermal shock, if low-temperature condensed water adheres to the gas detection element, the sensor is rapidly cooled, and cracks and cracks occur in the gas detection element due to thermal shock. There is a fear. In particular, in an intake pipe provided with an intercooler, the intake air is cooled by the intercooler, so that condensed water is easily generated on the downstream side of the intercooler. Further, since water vapor is generated by fuel combustion, the partial pressure of water vapor is higher in the exhaust than in the intake air. Therefore, in an internal combustion engine equipped with an EGR device that recirculates exhaust gas, condensed water is particularly likely to be generated in the downstream side intake pipe of the intercooler.

  In the intake pipe arranged in the vertical direction, the condensed water condensed above the gas sensor flows down along the inner wall surface of the intake pipe, reaches the detection unit, contacts the gas detection element built in the detection unit, and gas The detection element may be damaged by thermal shock.

  Patent Document 1 discloses a means for preventing water exposure to a gas sensor provided in an exhaust pipe arranged in a horizontal direction. This moisture prevention means covers the entire area of the detection part protruding from the exhaust flow path with a cup-shaped protective cover to prevent the condensed water from adhering to the detection part. Further, a large number of gas introduction holes are formed in the protective cover so that only gas components are introduced into the protective cover, thereby maintaining the detection accuracy of the gas sensor.

  Similarly, Patent Document 2 discloses a moisture prevention means for a gas sensor provided in an exhaust pipe arranged in the horizontal direction. This moisture prevention means is provided with a rectifying plate that deflects the exhaust gas in a direction away from the detection unit of the gas sensor in the upstream exhaust flow path of the gas sensor to reduce the probability that condensed water adheres to the detection unit. .

  Patent Document 3 discloses a means for preventing water exposure when a gas sensor is disposed in a surge tank provided in an intake pipe. This moisture prevention means forms an annular projection so as to surround the detection portion with respect to the gas sensor attached so that the detection portion is exposed in the internal space of the surge tank, and the wall surface of the surge tank is formed by the annular projection. The condensate and oil that flows down are blocked.

JP 2004-191096 A JP 2007-321593 A JP 2003-65171 A

  When the intake pipe is arranged in the vertical direction, there is a problem that the condensed water generated on the inner wall above the installation position of the gas sensor flows down along the inner wall of the intake pipe and adheres to the detection unit. The moisture prevention means disclosed in Patent Documents 1 and 2 are intended for exhaust pipes that are positioned in the horizontal direction, and do not solve the problem of flooding caused by condensed water generated in the intake pipes arranged in the vertical direction. Absent.

  Further, in the case where the moisture prevention means of Patent Document 1 is applied to an intake pipe arranged in the vertical direction, water droplets flowing down from the upper intake pipe inner wall may enter the inside of the protective cover from the gas introduction hole. . In addition, since the entire area of the detection unit is covered with a protective cover, a decrease in detection accuracy cannot be avoided. Further, since the water-preventing means of Patent Document 2 only deflects the exhaust gas in a direction away from the detection unit, it cannot prevent water droplets flowing down from the upper intake pipe inner wall from adhering to the detection unit. In the water-preventing means of Patent Document 3, the projecting dimension of the annular convex portion surrounding the detection portion is small, and a large amount of condensed water cannot be dammed up. Further, it is impossible to prevent water vapor in the intake air from coming into contact with the gas detection element.

  In the present invention, in view of the problems of the prior art, the detection part of the gas sensor provided in the intake pipe arranged in the vertical direction is wetted by the condensed water flowing down from the upper intake pipe inner wall, and the gas detection element is heated. The object is to prevent breakage due to impact by simple and low-cost means.

In order to achieve such an object, the water sensor for water sensor according to the present invention is disposed in an intake pipe that is connected to a cylinder head of an internal combustion engine and has a downstream side positioned upward, and a detection unit that protrudes into the intake pipe. in the water prevention device of the gas sensor, the inner wall of the intake pipe to be and downstream only above said detecting section of the gas sensor is provided with a shielding member that covers the entire area of the detector as viewed from the downstream side of the intake flow direction, upstream with contacting the gas component to the detection portion from the side, in which the condensed water flows down along the inner wall surface of the intake pipe by the shielding member is to be prevented from adhering to the detection unit.

The apparatus according to the present invention is such that the shielding member having the above-described configuration is provided on the inner wall of the intake pipe only at the upper position on the downstream side of the detection portion of the gas sensor at a position not too far from the gas sensor. Accordingly, the condensed water that is generated in the intake pipe above the detection section and flows down the inner wall of the intake pipe is blocked by the shielding member, thereby preventing the condensed water from adhering to the detection section. In the present specification, the “intake pipe whose downstream side is positioned upward” is, for example, an intake pipe arranged in a vertical direction or an intake pipe arranged in an up-down direction, and the downstream side is more upstream than the upstream side. It refers to the intake pipe located above.

  Thereby, it is possible to prevent the condensed water from adhering to the detection part protruding from the inner wall of the intake pipe. Therefore, the thermal shock of the gas detection element built in the detection part can be prevented, and it can prevent that a crack and a crack generate | occur | produce in a gas detection element. Moreover, since it is not the shape which covers the perimeter of a detection part, a gas component can contact a detection part with margin, Therefore, the detection accuracy of a gas component is not reduced.

  In the device according to the present invention, the shielding member may have a dam formed on the entire periphery of the end portion, and the water collecting recess may be formed by the dam. As a result, the condensed water received by the shielding member is collected in the catching recess, so that the condensed water does not fall onto the detection unit. Even when condensed water is generated in the intake pipe cooled while the internal combustion engine is stopped, and this condensed water is stored in the water catching section, the intake air is warmed if the internal combustion engine is started, so that it is stored in the water catching section. Water droplets gradually vaporize. Therefore, it is possible to prevent the stored water stored in the water catcher from overflowing from the water catcher.

Further, the invention apparatus, the shielding member is being formed so as to cover the entire area of the detector as viewed from the downstream side of the intake flow direction. As a result, even if condensed water overflows from the shielding member , the condensed water that has dropped does not come into contact with the detection unit, so that the detection unit can be prevented from being damaged.

  In the device according to the present invention, the upper surface of the shielding member is formed in an arc surface whose central portion is convex upward, and a weir is formed at the front end side of the shielding member disposed so as to face the inner wall of the intake pipe. The condensed water that has flowed down to the upper surface of the shielding member may be configured to flow down from the lower end on at least one side. Thereby, it is possible to flow down the condensed water flowing down the inner wall of the intake pipe without contacting the detection unit with a simpler and lower cost configuration.

  In the apparatus of the present invention, when the gas sensor is provided in a surge tank provided at the junction of the intake manifold, a shielding member may be provided on the inner wall of the surge tank above the gas sensor. In the surge tank where the intake manifold joins, the condensed water generated in the intake manifold gathers and a large amount of condensed water joins. Therefore, damage to the gas detection element can be effectively prevented by providing a shielding member in the gas sensor provided in the surge tank.

  When the gas sensor is provided on the intake manifold, the shielding member of the present invention may be provided on the inner wall of the intake manifold above the gas sensor. Since the shielding member has a simple configuration, it can be easily attached to each branch pipe of the intake manifold. Thus, even when the gas sensor is attached to the intake manifold, it is possible to prevent the gas detection element from being damaged. In this case, it is necessary to attach the same number of shielding members as the branch pipes of the intake manifold. However, since the shielding members may have a simple configuration, it does not require much labor for attachment, and the cost can be reduced.

  In addition, when a moisture prevention means for water vapor contained in the intake air upstream of the gas sensor is required, a known means such as a moisture prevention means disclosed in Patent Document 2 may be employed.

According to the present invention, the intake pipe downstream is connected to a cylinder head of an internal combustion engine is positioned above, in the water prevention apparatus arranged a gas sensor so as to protrude inside the detector is an intake pipe, a gas sensor of the detection A shielding member that covers the entire area of the detection unit as viewed from the downstream side in the intake air flow direction is provided on the inner wall of the intake pipe that is only above and downstream of the unit, so that the gas component contacts the detection unit from the upstream side since the condensed water flowing down along the inner wall surface of the intake pipe by the shielding member is to be prevented from adhering to the detection unit, the built in detector gas detection element, the intake pipe wall It is possible to prevent the condensed water flowing down from above from adhering.

  Therefore, it is possible to prevent thermal shock of the gas detection element, prevent the gas detection element from cracking, and reduce the gas component detection accuracy because the shielding member is not shaped to cover the entire circumference of the detection unit. I won't let you. Moreover, since it is a simple structure, it can also be installed in the intake manifold.

It is a whole block diagram of the diesel engine which concerns on 1st Embodiment of this invention apparatus. It is a partially expanded sectional view of FIG. It is sectional drawing which follows the AA line in FIG. It is a partially expanded sectional view which concerns on 2nd Embodiment of this invention apparatus. It is sectional drawing which follows the BB line in FIG. It is a partially expanded sectional view which concerns on 3rd Embodiment of this invention apparatus.

  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.

(Embodiment 1)
1st Embodiment which applied this invention to the diesel engine is described based on FIGS. FIG. 1 is a block diagram showing the entirety of a diesel engine to which the device of the present invention is applied. In FIG. 1, a diesel engine 10 of the present embodiment is provided with a plurality of cylinder blocks 12, and a cylinder head 14 is provided above each cylinder block 12. A fuel injection device 16 is provided at the center of each cylinder head 14, and an intake introduction portion and an exhaust discharge portion are provided on both sides of the fuel injection device 16 of the cylinder head 14. The intake air introduction portion is connected to an intake pipe 18 via an intake manifold 17, and the exhaust discharge portion is connected to an exhaust pipe 20 via an exhaust manifold 19.

  In the middle of the intake pipe 18 and the exhaust pipe 20, a variable blade supercharger 22 including a compressor provided in the intake pipe 18 and an exhaust turbine provided in the exhaust pipe 20 is provided. An exhaust gas purification device 24 having a diesel particulate filter is provided in the exhaust pipe 20 on the downstream side of the supercharger 22. A high pressure EGR pipe 26 connecting the upstream exhaust pipe 20 of the supercharger 22 and the intake pipe 18 downstream of the supercharger 22, and an exhaust gas purification device 28 that is interposed in the high pressure EGR pipe 26 and purifies EGR gas. And a high-pressure EGR device 32 comprising a high-pressure EGR valve 30 provided at the outlet of the high-pressure EGR pipe 26 and capable of adjusting the flow rate of the EGR gas flowing through the high-pressure EGR pipe 26.

  A low pressure EGR pipe 34 connecting the downstream exhaust pipe 20 of the supercharger 22 and the intake pipe 18 upstream of the supercharger 22, a low pressure EGR cooler 36 interposed in the low pressure EGR pipe 34, and an EGR pipe 34 Is provided with a low pressure EGR device 38 including a low pressure EGR valve 37 capable of adjusting the flow rate of the EGR gas flowing through the low pressure EGR pipe 34.

  An intercooler 40 for cooling the intake air is provided in the intake pipe 18 on the downstream side of the supercharger 22. An intake filter 42 and an air flow sensor 44 and an intake air temperature sensor 46 for detecting the intake air flow rate are provided at the inlet 18 a of the intake pipe 18 and on the downstream side of the intake filter 42. In addition, intake throttle valves 50 and 52 for adjusting the amount of intake air sucked into the cylinders are provided on the downstream side intake pipe and the intercooler downstream side intake pipe of these sensors. Each intake manifold 17 is provided with an intake air temperature sensor 54, a boost sensor 56 that detects intake air pressure, and an air-fuel ratio sensor 58.

  At the start of operation of the diesel engine 10, the exhaust turbine of the supercharger 22 is driven by the exhaust e, and the air is sucked into the intake pipe 18 by the compressor of the supercharger 22. Also, detection signals are input to the ECU 60 from the sensors. The ECU 60 controls the intake throttle valves 50 and 52, the EGR valves 30 and 36, the fuel injection device 16, and the like according to these detection signals.

In the diesel engine 10 of the present embodiment, the reason why the air-fuel ratio sensor 58 is provided in the surge tank 62 on the intake pipe side is that the actual oxygen concentration of the intake air a is detected by the air-fuel ratio sensor 58 and based on the detected value. Te, along with controlling the fuel injection amount of the fuel injection device 16 adjusts the EGR gas amount, in order to minimize the amount of NO _X in the exhaust gas.

  As shown in FIGS. 2 and 3, the intake pipe 18 is arranged in the vertical direction, and is connected to the surge tank 62 at the upper end of the intake pipe 18. An intake manifold 17 having the same number of branch pipes as a plurality of cylinders is connected to the surge tank 62 in the horizontal direction. The other end of each branch pipe of the intake manifold 17 is connected to an intake introduction portion of the cylinder head 14 of each cylinder. An air-fuel ratio sensor 58 is attached to the surge tank 62. A detection part 58a of the air-fuel ratio sensor 58 is projected from the vertical wall 62a arranged in the vertical direction of the surge tank 62 into the internal space (intake flow path). The detection unit 58a includes a gas detection element, and a gas component flows in from a gas introduction hole (not shown) formed in the case of the detection unit 58a, and detects the oxygen concentration by contacting the gas detection element. . An intercooler 40 is provided on the upstream side of the intake pipe 18.

  A shield 64 is provided on the vertical wall 62 a above the air-fuel ratio sensor 58. The shield 64 includes a bottom wall 64a protruding toward the inner space, a weir 64b provided on the entire periphery of the end of the bottom wall 64a, and a bent portion 64d formed at the upper end of the weir 64b. By forming the weir 64b on the bottom wall 64a, a water catching recess 64c for storing condensed water is formed. As shown in FIG. 2, the intake passage side protrusion dimension t1 of the shield 64 is configured to be larger than the intake passage side protrusion dimension t2 of the detector 58a. Further, as shown in FIG. 3, the horizontal width dimension p1 of the shield 64 is configured to be larger than the horizontal width dimension p2 of the gas detection element 58a.

  In such a configuration, the intake air a cooled by the intercooler 40 includes condensed water w, and the condensed water w adheres to the inner wall of the surge tank 62. The condensed water w adhering to the vertical wall 62a above the air-fuel ratio sensor 58 becomes water droplets and descends the wall surface. However, since the shield 64 is above the air-fuel ratio sensor 58, the condensed water w is received by the shield 64 and stored in the water catching recess 64 c of the shield 64. If the amount of water drops is an appropriate amount, it can be stored in the water catching recess 64c.

  Water droplets tend to be generated in large quantities mainly at low temperatures when the diesel engine 10 is started, but when the diesel engine 10 is warmed up, the condensed water w stored in the water catching portion 64c is gradually vaporized, Since the amount of storage is reduced, there is little possibility of overflowing from the water catching recess 64c.

  According to the present embodiment, the condensed water w that is generated in the vertical wall 62a above the air-fuel ratio sensor 58 and descends the vertical wall 62a is collected in the water-collecting recess 64c of the shield 64. w does not adhere to the detection part 58a. Therefore, it is possible to prevent the thermal shock of the gas detection element built in the detection unit 58a and to prevent the gas detection element 58a from being cracked or cracked. Moreover, since the shielding body 64 is not shaped to cover the entire circumference of the detection unit 58a as in Patent Document 1, the detection accuracy of the gas component of the air-fuel ratio sensor 58 is not reduced.

  In addition, since the protrusion dimension t1 of the shield 64 is larger than the protrusion dimension t2 of the detector 58a, and the width dimension p1 of the shield 64 is larger than the width dimension p2 of the detector 58a, it should Even when the condensed water w overflows, the condensed water w that has fallen does not come into contact with the detection unit 58a, so that the detection unit 58a can be prevented from being damaged. Further, condensed water generated in the plurality of branch pipes joins the surge tank 62 where the intake manifold 17 joins. Therefore, the condensate water w generated in all the branch pipes of the intake manifold 17 can be collected by one shield 64 provided in the surge tank 62.

  In addition, in this embodiment, the structure which does not provide the bending part 64d in the weir 64b may be sufficient. Further, in the case where the water prevention means for the condensed water contained in the intake air a on the upstream side is necessary, for example, a water prevention means as disclosed in Patent Document 2 may be adopted.

(Embodiment 2)
A second embodiment of the device of the present invention will be described with reference to FIGS. As in the first embodiment, the present embodiment is an example in which the air-fuel ratio sensor 58 is provided on the vertical wall 62a of the surge tank 62, and the shield 70 is provided on the upper vertical wall 62a. The shielding body 70 is composed of a bottom wall 70a of a plate-like body that is formed in an arc shape with a quadrangular surface convex upward, and a weir 70b that is integrally formed on the tip side facing the inner wall of the surge tank 62. In addition, the dam is not formed in the lower end side 70c and 70d of the bottom wall 70a located in the both ends side of the dam 70b.

  The intake passage side protrusion dimension t1 of the shield 70 is configured to be larger than the protrusion dimension t2 of the detector 58a, and the horizontal width dimension p1 of the shield 70 is configured to be greater than the horizontal width dimension p2 of the detector 58a.

  In such a configuration, the condensed water w flowing down from above the shield 64 along the vertical wall 62 a is temporarily received by the bottom wall 70 a of the shield 70. Thereafter, the upper surface of the bottom wall 70a having an arc shape is slid and falls from the lower end sides 70c and 70d. Since the horizontal width dimension p1 of the shield 70 is greater than the horizontal width dimension p2 of the detection unit 58a, the lower end sides 70c and 70d are located outside the detection unit 58a when viewed from the intake flow direction. The condensed water w that has fallen from the sides 70c and 70d does not come into contact with the detection unit 58a.

  According to the present embodiment, the condensed water w generated on the inner wall of the surge tank above the air-fuel ratio sensor 58 falls without coming into contact with the detection unit 58a, so that the gas detection element can be prevented from being damaged due to thermal shock.

(Embodiment 3)
Next, a third embodiment of the device of the present invention will be described with reference to FIG. In this embodiment, each branch pipe of the intake manifold 17 connected to the downstream side of the surge tank 62 includes an intake manifold vertical portion 17a disposed in the vertical direction and an intake manifold horizontal portion 17b disposed in the horizontal direction. Become. An air-fuel ratio sensor 58 is provided on the inner wall of each branch pipe arranged in the vertical direction of the intake manifold vertical portion 17a. The shield 64 of the present invention is provided on the vertical wall above the air-fuel ratio sensor 58. The shield 64 has the same configuration as that of the first embodiment, and includes a protruding wall 64a, a bank 64b, and a bent portion 64d, and forms a water catching recess 64c. The shield 64 may be formed integrally with the intake manifold 17.

  According to this embodiment, since the condensed water w generated on the wall surface of the intake manifold vertical portion 17a and flowing downward can be collected by the shield 64, the gas detection of the air-fuel ratio sensor 58 provided in the intake manifold vertical portion 17a. Damage to the element can be prevented. Further, according to the present embodiment, since the air-fuel ratio sensor 58 can be provided in the intake manifold vertical portion 17a, the air-fuel ratio of the intake air a can be accurately detected for each branch pipe. In the present embodiment, the same number of shields 64 as the number of branch pipes are required. However, since the shields 64 have a simple configuration, they do not require much labor for mounting and can be made at low cost. Further, if the shield 64 is formed integrally with the intake manifold 17, the shield 64 can be easily attached.

  ADVANTAGE OF THE INVENTION According to this invention, the gas sensor provided in the intake pipe arrange | positioned to an up-down direction can be protected with a simple and low-cost structure with respect to the condensed water which flows down along the upper inner wall of a downstream side.

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Cylinder block 14 Cylinder head 16 Fuel injection apparatus 17 Intake manifold 17a Intake manifold vertical part 17b Intake manifold horizontal part 18 Intake pipe 18a Inlet 19 Exhaust manifold 20 Exhaust pipe 22 Supercharger 24, 28 Exhaust gas purification apparatus 26 High pressure EGR Pipe 30 High pressure EGR valve 32 High pressure EGR device 34 Low pressure EGR pipe 36 Low pressure EGR cooler 37 Low pressure EGR valve 38 Low pressure EGR device 40 Intercooler 42 Intake filter 44 Air flow sensor 46, 54 Intake temperature sensor 50, 52 Intake throttle valve 56 Boost sensor 58 Air-fuel ratio sensor (gas sensor)
58a detector 60 ECU
62 Surge tank 62a Vertical wall 64, 70 Shield 64a, 70a Bottom wall 64b, 70b Weir 64c Recess for catching water 64d Bent part 70c, 70d Lower end side a Intake e Exhaust w Condensed water

Claims (5)

In a water sensor for a water sensor of a gas sensor, which is connected to a cylinder head of an internal combustion engine and whose downstream side is located at an upper side and a detection part is arranged so as to protrude into the intake pipe,
A shielding member is provided on the inner wall of the intake pipe that is only above and downstream from the detection part of the gas sensor, and covers the entire area of the detection part as viewed from the downstream side in the intake flow direction, from the upstream side to the detection part. with contacting the gas component, the shielding member by flows down along the inner wall surface of the intake pipe has the condensed water is exposed to water prevention device of a gas sensor being characterized in that so as to prevent from adhering to the detection unit .   The said shielding member is formed with a weir on the entire periphery of the end portion thereof, and has a water catching recess formed by the weir. The upper surface of the shielding member is formed in an arc surface whose central portion is convex upward, and a weir is formed at the distal end side of the shielding member disposed so as to face the inner wall of the intake pipe. 2. The apparatus for preventing water from being exposed to a gas sensor according to claim 1, wherein the condensed water flowing down to the upper surface of the gas sensor is allowed to flow down from at least one lower end . 2. The apparatus of claim 1, wherein the gas sensor is provided in a surge tank provided at a junction of an intake manifold, and the shielding member is provided on an inner wall of the surge tank above the gas sensor. . 2. The apparatus for preventing water exposure of a gas sensor according to claim 1, wherein the gas sensor is provided on an intake manifold, and the shielding member is provided on an inner wall of the intake manifold above the gas sensor.

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