JP2004257261A - Exhaust pipe and exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust pipe capable of avoiding damage to a sensor element by preventing water generated by the moisture condensation in exhaust gas from contacting with the sensor and preventing a drop in detection accuracy by the sensor, and to provide an exhaust emission control device for an internal combustion engine with the pipe. <P>SOLUTION: A partition plate 100 separating an exhaust passage into upper and lower parts is provided in the exhaust pipe 50 to form a first passage 50A in the upper part and a second passage 50B in the lower part. A plurality of communication holes 101 communicating the first passage 50A and the second passage 50B is provided in the plate 100. There is further provided a wall 102 inclined downwards below the hole 101, thereby forming a communication passage communicating the first and the second passages 50A, 50B. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust pipe provided with a sensor for detecting a component in exhaust gas in an exhaust passage, and an exhaust purification device for an internal combustion engine provided with the exhaust pipe.
[0002]
[Prior art]
Generally, a sensor for detecting components in exhaust gas is provided in the exhaust pipe to perform various controls. In many cases, such a sensor element has an active temperature, and accurate detection cannot be performed unless the environment is at a certain temperature. For example, in order to measure the oxygen concentration in the exhaust gas, the oxygen sensor that detects the components in the exhaust gas does not have high detection accuracy unless the environment is, for example, 200 ° C. or higher. Therefore, there is known a technique in which a heater for heating an element is provided in a sensor, and the element is heated to an activation temperature early.
[0003]
By the way, when the engine is stopped, the exhaust gas in the exhaust passage cools down, and the moisture in the exhaust gas condenses, or immediately after the engine starts, the exhaust gas flows into the low temperature exhaust passage, and the exhaust gas is cooled and the moisture in the exhaust gas is reduced. When water condenses, water may accumulate in the exhaust passage.
[0004]
If such water is scattered by exhaust gas and touches the high temperature element, the element will be cooled rapidly, and the detection accuracy may be reduced. It may be damaged. Therefore, it is necessary to take measures to prevent water from touching the element.
[0005]
Conventionally, as a countermeasure for this, a technique for preventing the temperature of the element from being raised until the condensed water has evaporated (for example, Patent Document 1) and a technique for disposing a protector around the element (for example, Patent Document 2) It has been known. In the former case, there is a problem that emission and fuel consumption deteriorate while the temperature of the element is not increased. There are Patent Documents 3 and 4 as other related technologies.
[0006]
[Patent Document 1]
JP-A-8-15213
[Patent Document 2]
JP 2001-73827 A
[Patent Document 3]
Japanese Utility Model Application Laid-Open No. 61-62221
[Patent Document 4]
Japanese Utility Model Publication No. Sho 62-18319
[Problems to be solved by the invention]
As described above, it is necessary to take measures to prevent water from touching the sensor element.
[0007]
Therefore, one of the objects of the present invention is to reduce accumulation of water near the sensor element and prevent the sensor element from being touched by water.
[0008]
Another object of the present invention is to prevent water from splashing near the sensor element and prevent water from touching the sensor element.
[0009]
One of the objects of the present invention is to prevent damage to the sensor element by preventing water from touching the sensor element in a high temperature state.
[0010]
Another object of the present invention is to prevent a decrease in detection accuracy due to a decrease in temperature due to contact of water with the sensor element. Accordingly, the object of the present invention is to improve the exhaust air-fuel ratio control and the purification performance.
[0011]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
[0012]
In the present invention, one-way movement of water is performed from a region (first region) where water (condensed water) is likely to be scattered toward the sensor element (first region) to a region where water (condensed water) is not likely to be scattered (less). Is provided. According to this configuration, the water in the first area moves to the second area by the one-way passage, so that the accumulation of water in the first area can be reduced, and the water scattered toward the sensor element can be reduced. It becomes. In addition, since the passage is one-way, the movement of the water in the second region to the first region is suppressed, and the water in the second region is prevented from scattering near the element through the passage.
[0013]
More specifically, as a configuration of the exhaust pipe of the present invention, a first passage that forms a flow of exhaust gas passing through a sensor element portion of a sensor that detects a component in exhaust gas,
A second passage that forms a flow of exhaust gas that does not pass through the sensor element from the upstream side to the downstream side of the sensor element;
The water formed by condensing the moisture in the exhaust gas on the first passage side is moved to the second passage side, and the water formed by condensing the moisture in the exhaust gas on the second passage side and moving from the first passage side. And a communication passage that communicates the first passage with the second passage, in which the drained water is suppressed from being moved to the first passage side.
[0014]
According to this configuration, since the water on the first passage side is moved to the second passage side by the communication passage, the accumulation of water in the first passage can be reduced, and the accumulation of water near the sensor element portion can be reduced. it can. Further, in the communication path, the water on the second path side is suppressed from moving to the first path side, so that the water scattered on the second path side scatters toward the sensor element through the communication path. Can be suppressed.
[0015]
Further, as another configuration of the exhaust pipe of the present invention, a first passage that forms a flow of exhaust gas passing through a sensor element portion of a sensor that detects a component in exhaust gas,
A second passage that forms a flow of exhaust gas that does not pass through the sensor element from the upstream side to the downstream side of the sensor element;
A communication passage having an inclined portion for guiding water produced by condensation of moisture in the exhaust gas to the second passage side on the first passage side, the communication passage connecting the first passage and the second passage;
And a blocking portion for blocking entry of water scattered from the second passage side into the communication passage.
[0016]
According to this configuration, since the water on the first passage is guided to the second passage by the inclined portion of the communication passage, the accumulation of water in the first passage can be reduced, and the water accumulates near the sensor element. Can be reduced. Further, since the water scattered from the second passage side is prevented from entering the communication passage by the blocking portion, the water scattered on the second passage side can be suppressed from scattering toward the sensor element through the communication passage. .
[0017]
Further, as another configuration of the exhaust pipe of the present invention, a first passage that forms a flow of exhaust gas passing through a sensor element portion of a sensor that detects a component in exhaust gas,
A second passage that forms a flow of exhaust gas that does not pass through the sensor element from the upstream side to the downstream side of the sensor element;
A first passage having an inclined portion for guiding water produced by condensing moisture in the exhaust gas to the second passage on the first passage side, and having an opening toward the second passage facing downstream; And a communication passage communicating with the second passage.
[0018]
According to this configuration, since the water on the first passage is guided to the second passage by the inclined portion of the communication passage, the accumulation of water in the first passage can be reduced, and the water accumulates near the sensor element. Can be reduced. Further, since the opening of the communication passage toward the second passage is directed to the downstream side, the water scattered from the second passage by the exhaust gas is prevented from entering the communication passage through the opening. Therefore, it is possible to suppress the water scattered on the side of the second passage from scattering toward the sensor element through the communication passage.
[0019]
The opening of the communication passage on the first passage side is preferably provided on the upstream side of the sensor element.
[0020]
According to this structure, the water on the first passage side can be reduced on the upstream side of the sensor element, so that the water scattered in the direction of the exhaust gas is scattered toward the sensor element. Can be reduced. In addition, even when the opening of the communication passage on the first passage side is downstream of the sensor element portion, some water is scattered in a direction opposite to the flow of the exhaust gas due to vibration or the like. This has the effect of reducing the scattered water.
[0021]
Here, the above-mentioned "first passage" and "second passage" can be configured by, for example, dividing one passage into two passages by a partition plate. Further, it can be constituted by a double tube provided concentrically. Furthermore, it can also be constituted by branching one tube into two tubes or providing two independent tubes.
[0022]
The “first passage that forms the flow of exhaust gas passing through the sensor element unit” means that exhaust gas flowing through the first passage passes through the sensor element unit. In addition to the case where the sensor element is provided, the case where the sensor element is provided near the opening end downstream of the first passage is also included. The “second passage that forms the flow of exhaust gas that does not pass through the sensor element unit” means that exhaust gas flowing through the second passage does not pass through the sensor element unit. In other words, this means that the sensor element portion is not provided in the second passage, and the exhaust gas flowing through the second passage flows downstream of the sensor element portion.
[0023]
Further, as another exhaust pipe of the present invention, a sensor provided at the upper part of the exhaust passage, which includes a sensor element portion of a sensor for detecting a component in the exhaust gas, or a portion near the sensor element portion Also, on the upstream side, a partition plate that partitions the exhaust passage into upper and lower passages is provided,
On the partition plate,
A communication hole communicating the upper and lower passages,
Below the communication hole, the upper surface is formed by an inclined surface that guides water formed by condensing moisture in the exhaust gas to the lower passage on the upper passage side, and the lower surface thereof is scattered from the lower passage side. And a wall configured with a blocking surface that blocks entry into the communication hole.
[0024]
According to this configuration, since the water on the upper passage is guided to the lower passage by the inclined surface on the upper surface of the wall provided below the communication hole, it is possible to reduce accumulation of water in the upper passage. In addition, accumulation of water near the sensor element can be reduced. Further, the water scattered from the lower passage side is prevented from entering the communication hole by the shielding surface on the lower surface of the wall. Therefore, it is possible to suppress the water scattered on the lower passage side from being scattered toward the sensor element through the communication hole.
[0025]
Here, it is preferable that the opening to the passage above the communication hole is provided on the upstream side of the sensor element portion. This makes it possible to reduce the amount of water on the upstream side of the sensor element portion, so that the water scattered in the exhaust flow direction can be effectively reduced from being scattered toward the sensor element. Even when the upper opening of the communication hole is on the downstream side of the sensor element, some water is scattered in a direction opposite to the flow of the exhaust gas due to vibration or the like. There is an effect that can be reduced.
[0026]
Further, as another exhaust pipe of the present invention, a sensor provided at the upper part of the exhaust passage, which includes a sensor element portion of a sensor for detecting a component in the exhaust gas, or a portion near the sensor element portion A first partition plate having an inclined portion that is inclined downward from one end in the width direction of the exhaust passage toward the other end, and an inclined portion that is inclined downward from the other end in the width direction of the exhaust passage toward the one end. A second partition plate having an inclined portion, and the inside of the exhaust passage is vertically divided by these partition plates,
In these partition plates, a gap is provided between the first partition plate and the second partition plate in the vertical direction to form a communication passage communicating vertically with the exhaust passage, and the first partition is formed in the width direction. There is one characterized by being arranged so that there is no gap between the plate and the second partition plate.
[0027]
According to this configuration, the water in the upper passage flows downward on the upper surface of the partition plate because the first partition plate and the second partition plate are inclined downward. Here, since a communication path is formed between the first partition plate and the second partition plate by providing a gap in the up-down direction, water starting from any of the partition plates will eventually reach the lower passage. It flows to. Therefore, the accumulation of water in the upper passage can be reduced, and the accumulation of water near the sensor element can be reduced. In addition, since there is no gap between the first partition plate and the second partition plate in the width direction, water scattered on the lower passage side is blocked by any one of the partition plates. Does not fly to the upper aisle side.
[0028]
Further, as an exhaust pipe of another invention, there is provided a sensor provided at an upper part of an exhaust passage, in a range where a sensor element portion of a sensor for detecting a component in exhaust gas is provided, or A partition plate is provided on the upstream side of the vicinity to partition the exhaust passage into upper and lower passages,
The partition plate is provided with a communication hole communicating the upper and lower passages.
[0029]
According to this configuration, since the water in the upper passage drops through the communication hole to the lower passage, the accumulation of water in the upper passage can be reduced. Further, water scattered on the lower passage side can be prevented from scattered to the upper passage side in a portion of the partition plate where there is no communication hole.
[0030]
Here, it is preferable that the opening to the passage above the communication hole is provided on the upstream side of the sensor element portion. This makes it possible to reduce the amount of water on the upstream side of the sensor element portion, so that the water scattered in the exhaust flow direction can be effectively reduced from being scattered toward the sensor element. Even when the upper opening of the communication hole is on the downstream side of the sensor element, some water is scattered in a direction opposite to the flow of the exhaust gas due to vibration or the like. There is an effect that can be reduced.
[0031]
Further, as an exhaust pipe of another invention, there is provided a sensor provided at an upper part of an exhaust passage, in a range where a sensor element portion of a sensor for detecting a component in exhaust gas is provided, or A partition plate is provided on the upstream side of the vicinity to partition the exhaust passage into upper and lower passages,
The partition plate is provided so as to be inclined downward toward the downstream side.
[0032]
According to this configuration, the water accumulated on the partition plate in the upper passage flows down along the partition plate. Further, even if water remains on the partition plate without flowing down, it is possible to prevent the exhaust from directly hitting the water. Therefore, it is possible to reduce the scattering of water toward the sensor element. Water scattered in the lower passage is blocked by the partition plate.
[0033]
Further, as an exhaust purification device for an internal combustion engine of the present invention, the exhaust pipe according to any one of the above is provided,
The exhaust gas component is controlled based on a detection result obtained by a sensor disposed in the exhaust pipe.
[0034]
According to this configuration, since the splashed water is prevented from touching the sensor element, the detection accuracy of the sensor does not decrease, stable exhaust gas component control can be performed, and stable purification can be performed. Performance can be realized.
[0035]
It should be noted that the above configurations can be employed in combination as much as possible.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless otherwise specified. Absent.
[0037]
First, before describing the exhaust pipe and the exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment, an overall outline and the like of an internal combustion engine provided with these components will be described.
[0038]
[Basic structure and function of internal combustion engine]
An internal combustion engine (hereinafter, referred to as an engine) 1 shown in FIG. 1 includes a plurality of cylinders (only one cylinder is shown in FIG. 1), and repeats four cycles of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke. It is a diesel engine that obtains output.
[0039]
A piston 12 is reciprocally accommodated in a cylinder 11 formed inside the engine 1. A space surrounded by the top surface 12a of the piston 12, the inner wall of the cylinder 11, and the ceiling 11a of the cylinder 11 forms a combustion chamber 13. A connecting rod 14 connected to the piston 12 converts a reciprocating motion of the piston 12 in the cylinder 11 into a rotational motion of a crankshaft (not shown) of the engine 1.
[0040]
On the ceiling 11a of the cylinder 11, a fuel injection valve 60 for directing the injection hole to the combustion chamber 13 is provided. The fuel injection valve 60 is pressurized by a high-pressure pump (not shown) or the like, and injects pressurized fuel stored in a pressure accumulator (not shown) into the combustion chamber 13 in an appropriate amount and at an appropriate timing. It is a drive type on-off valve.
[0041]
In addition, the ceiling 11a of the cylinder 11 has an intake port 41 communicating with the combustion chamber 13 and forming the most downstream portion of the intake pipe 40, and an exhaust port 51 communicating with the combustion chamber 13 and forming the most upstream part of the exhaust pipe 50. Is formed. Further, the ceiling 11a is provided with an intake valve 19 for opening and closing a boundary between the intake port 41 and the combustion chamber 13, and an exhaust valve 20 for opening and closing a boundary between the exhaust port 51 and the combustion chamber 13. I have. The intake valve 19 basically repeats a reciprocating motion (opening / closing operation) in synchronization with the rotation of the crankshaft. The exhaust valve 20 basically repeats a reciprocating motion (opening / closing operation) in synchronization with the rotation of the crankshaft.
[0042]
The intake pipe 40 forms a passage for air (intake) that is taken into the combustion chamber 13 from the outside. A throttle valve 42 is provided inside the intake pipe 40. The throttle valve 42 is an electronically controlled open / close valve whose opening is continuously adjusted by an actuator 42a having a step motor or the like.
[0043]
The exhaust pipe 50 forms a passage for exhaust gas discharged from the combustion chamber 13. Inside the exhaust pipe 50, a catalyst casing 54 and an oxygen concentration sensor 55 are provided. The catalyst casing 54 incorporates an unillustrated exhaust gas purification catalyst (hereinafter simply referred to as a catalyst). The catalyst is activated under conditions where the ambient temperature is above a predetermined value (for example, 200 ° C.), and purifies nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) in the exhaust gas. In particular, the catalyst temporarily holds NOx under the condition where the oxygen concentration in the exhaust gas is high (lean atmosphere) and holds it under the condition where the concentration of the reducing component (for example, unburned fuel component) is high (rich atmosphere). NOx is released and reduced.
[0044]
The oxygen concentration sensor 55 includes a detection element 55A that is exposed to gas in the exhaust passage, and an electric heater 55B that is provided in parallel with the detection element 55A, and outputs a signal corresponding to the oxygen concentration in the exhaust. The output signal of the oxygen concentration sensor 55 includes the ratio (air-fuel ratio) A / F of the amount of oxygen and the amount of fuel supplied to the engine in the combustion chamber 13 and the oxidizing component (for example, oxygen) and the reducing component contained in the exhaust gas. There is a high correlation with the concentration ratio (for example, unburned fuel component).
[0045]
An electronic control unit (ECU) 80 includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), a backup RAM, and a timer for measuring time during a period when the engine 1 is operating. , An external input circuit including an A / D converter, and an external output circuit. Further, the main circuit, the external input circuit, and the internal input circuit are mutually connected by a bidirectional bus to form a logical operation circuit.
[0046]
By operating the fuel injection valve 60, the throttle valve 42, and the like, the ECU 80 configured as described above performs various controls related to optimization of the operation state of the engine 1 and improvement of exhaust characteristics.
[0047]
For example, the ECU 80 can adjust the amount of fuel injected through the fuel injection valve 60 based on the output signal of the oxygen concentration sensor 55, and can execute feedback control for converging the air-fuel ratio to a predetermined target value.
[0048]
[Detection method of oxygen concentration in exhaust gas]
FIG. 2 shows a cross-sectional structure of a detection unit of the oxygen concentration sensor 55 including the detection element 55A and the heater 55B.
[0049]
As shown in FIG. 2, the detection element 55A of the oxygen concentration sensor 55 is made of zirconia (ZrO). ₂ ), Etc., are formed by laminating plate members 55a, 55b, 55c made of a porous insulating material having oxygen ion conductivity and heat resistance. An air introduction space S1 communicating with the atmosphere is formed inside the laminate of the plate members 55a, 55b, and 55c. Electrodes are provided on both sides of the plate member 55a, that is, a plate surface facing the external space (space in the exhaust passage) S2 of the detection element 55A and a plate surface facing the air introduction space S1 formed inside the detection element 55A. 55d and 55e are attached. Further, a gas diffuser 55h is provided between the electrode 55d and the external space S2.
[0050]
An electric heater 55B is attached to the plate 55c of the detection element 55A. The heater 55B includes a plate member 55f and a heating wire 55g built in the plate member 55f, and plays a role of heating the detection element 55A and maintaining the temperature at a predetermined value.
[0051]
When a predetermined voltage is applied between the two electrodes 55d and 55e, oxygen molecules existing near the two electrodes 55d and 55e are ionized and permeate the plate 55a along the arrow α direction. At this time, the value of the current flowing between the two electrodes 55d and 55e is quantitatively related to the difference between the oxygen concentration in the space S2 and the oxygen concentration near the electrode 55d (approximately zero). This is because the flow rate of the oxygen gas passing through the gas diffuser 55d is limited (by the action of the gas diffuser 55d), so that a quantitative relationship with high reproducibility between the current value and the oxygen concentration difference is obtained. Is guaranteed. Therefore, by observing the value of the current flowing between the electrodes 55d and 55e when a predetermined voltage is applied between the electrodes 55d and 55e, it is possible to grasp the oxygen concentration in the space S2 (oxygen concentration in the exhaust gas). it can.
[0052]
FIG. 3 is a graph showing the relationship between the applied voltage and the current between the electrodes 55d and 55e. In the graph, a plurality of conditions (oxygen excess ratios λ = a, b, c, d: where a <b <), in which the oxygen concentration (oxygen excess ratio) in the space S2 (in the detection target gas) is different. The relationship between applied voltage and current corresponding to c <d) is shown.
[0053]
As shown in FIG. 3, although the current value tends to increase as the applied voltage increases, it can be seen that the current value hardly changes when the applied voltage is in a specific range. The current values I1, I2, I3, and I4 in such a specific range are referred to as limiting current values corresponding to the oxygen excess ratio λ = a, b, c, and d. Therefore, an applied voltage (for example, a voltage value Vx shown in the drawing) for maintaining the current value flowing between the electrodes 55d and 55e at such a limit current value is appropriately set, and the limit current value is measured to detect the current. The oxygen concentration (excess oxygen ratio) in the target gas can be grasped quantitatively.
[0054]
FIG. 4 is a graph schematically showing the correspondence between the oxygen concentration in the space S2 and the limit current value. As shown in FIG. 4, as the oxygen concentration in the space S2 (oxygen concentration in the exhaust gas) increases, the limit current value also increases. Therefore, if two coordinates that clearly show the correspondence between the oxygen concentration in the exhaust gas and the limit current value are determined in advance, as shown at points A and B in FIG. 4, a line connecting the two coordinates ( The oxygen concentration in the exhaust gas can be quantified from the detection signal (limit current value) of the oxygen concentration sensor 55 based on the characteristic line).
[0055]
[Necessity of sensor element protection]
In order for the oxygen concentration sensor 55 to output an accurate signal according to the oxygen concentration in the exhaust gas, a predetermined temperature condition (for example, 200 ° C. or higher) needs to be satisfied. For this reason, the ECU 80 controls the temperature of the detection element 55A by controlling the energization of the heater 55B during the operation of the engine 1.
[0056]
By the way, as described in the related art, when the engine 1 is stopped, moisture contained in the gas in the exhaust passage condenses, or immediately after the engine 1 starts, the exhaust gas flows into the exhaust passage whose temperature is low. As a result, water (water droplets) may accumulate in the exhaust passage of the engine due to condensation of moisture in the exhaust gas. Then, the water (retained water) accumulated in the exhaust passage from the stop of the engine 1 to immediately after the start of the engine 1 is scattered by the flow of exhaust gas of the engine 1 and the like, and the splash is heated by the sensor element (detection) When the detection element 55A or the heater 55B) comes into contact with the element 55A or the heater 55B), the detection element 55A or the heater 55B is rapidly cooled and may be damaged by a thermal shock (thermal shock). In addition, when water comes into contact with the detection element 55A, the temperature decreases, and thus the detection accuracy may be reduced.
[0057]
Therefore, the oxygen concentration sensor is generally disposed at the top of the exhaust passage so that water does not touch the sensor element. However, this alone is not sufficient as a countermeasure, and in this embodiment, the structure of the exhaust pipe is further devised. Hereinafter, an exhaust pipe and an exhaust gas purification device for an internal combustion engine according to various embodiments of the present invention will be described. Here, the exhaust gas purification device mainly includes an exhaust pipe, a catalyst provided in the exhaust pipe, and a sensor (in this embodiment, an oxygen concentration sensor for measuring oxygen concentration) for detecting components in exhaust gas. Is done. The present embodiment is characterized by the structure of the exhaust pipe, and a known technique can be applied to the catalyst and the sensor. Therefore, in the following embodiments, the structure of the exhaust pipe will be mainly described. .
[0058]
(First Embodiment)
Referring to FIGS. 5 and 6, an exhaust pipe according to a first embodiment of the present invention and an exhaust purification device for an internal combustion engine including the same will be described. 5A and 5B are schematic views of the exhaust pipe according to the first embodiment of the present invention. FIG. 5A is a partially cutaway perspective view, and FIG. 5B is an enlarged view of a part of FIG. FIG. 6 is a part of a schematic cross-sectional view of the exhaust pipe according to the first embodiment of the present invention.
[0059]
In the present embodiment, as shown, a partition plate 100 is provided in the exhaust pipe 50 to partition the exhaust passage up and down. The partition plate 100 forms an upper first passage 50A and a lower second passage 50B. The area where the partition plate 100 is provided is sufficient for a part of the exhaust passage, but may be provided for the entire exhaust passage.
[0060]
The positional relationship between the partition plate 100 and the oxygen concentration sensor 55 will be described in more detail. The exhaust gas flowing on the first passage 50A side partitioned by the partition plate 100 passes through the oxygen concentration sensor 55, but the exhaust gas flowing on the second passage 50B side must not pass through the oxygen concentration sensor 55. That is, the oxygen concentration sensor 55 needs to be provided in the first passage 50A or in the vicinity of the downstream end of the first passage 50A. The reason for such a positional relationship is that the condensed water generated in the exhaust passage flows only to the second passage 50B side, as will be described in detail later. Therefore, the exhaust gas flowing through the second passage 50B does not pass through the oxygen concentration sensor 55, and only the exhaust gas flowing through the first passage 50A passes through the oxygen concentration sensor 55.
[0061]
The partition plate 100 is provided with a plurality of communication holes 101 that communicate the first passage 50A and the second passage 50B. A wall 102 inclined downward is provided below the communication hole 101, and the communication hole 101 and the wall 102 form a communication passage that communicates the first passage 50A and the second passage 50B. . The upper surface of the wall 102 is formed by an inclined surface 102a that is inclined downward as it goes in the direction in which the exhaust gas flows. As a result, the opening of the communication passage toward the second passage 50B faces downstream (downstream in the flow of exhaust gas). The arrows in the drawing indicate the direction in which the exhaust gas flows.
[0062]
With the above configuration, water generated by condensing the moisture in the exhaust gas on the first passage 50A side accumulates on the upper surface of the partition plate 100. It flows by gravity along the surface 102a. As described above, the water W1 on the first passage 50A side is guided and moved toward the second passage 50B by the inclined surface 102a. Here, since the wall 102 is provided below the communication hole 101, water does not accumulate in the communication hole 101 due to surface tension, and the water W1 in the communication hole 101 is preferably formed on the wall 102. It flows along the inclined surface 102a of the upper surface. In the present embodiment, the upstream end 103 of the partition plate 100 is curved downward. This effectively prevents water from adhering to the upstream end portion 103 due to surface tension.
[0063]
As described above, with the configuration of the present embodiment, the condensed water staying in the first passage 50A can be reduced. Therefore, it is possible to reduce the water scattered toward the oxygen concentration sensor 55 due to the flow of the vibration or the exhaust gas.
[0064]
In addition, water generated by condensing moisture in the exhaust gas on the second passage 50B side and water moved from the first passage 50A side stay on the floor of the second passage 50B. The water W2 retained in this manner may be scattered by vibration or exhaust. However, the scattered water is blocked by the lower surface of the flat plate portion of the partition plate 100 and is not moved to the first passage 50A side. Further, as described above, although the communication path connecting the first passage 50A and the second passage 50B is provided, the scattered water is blocked by the lower surface of the wall 102, so that the water passes through the communication path and passes through the first passage. It is not moved to the 50A side. In other words, the lower surface of the wall 102 functions as a blocking part (blocking surface 102b) that blocks entry of water scattered from the second passage 50B side into the communication passage. Here, most of the scattered water is scattered in the direction in which the exhaust gas flows. On the other hand, in the present embodiment, since the opening of the communication passage toward the second passage 50B faces the downstream side as described above, it is effective to prevent the scattered water from entering the inside of the communication passage. It is suppressed to.
[0065]
Thus, with the configuration of the present embodiment, it is possible to suppress the water scattered on the second passage 50B side from moving to the first passage 50A side. Therefore, it is possible to suppress the water scattered toward the oxygen concentration sensor 55 due to the vibration and the flow of the exhaust gas.
[0066]
The number and size of the communication passages can be set as appropriate. However, regarding the arrangement position of the opening of the communication passage on the side of the first passage 50A (the arrangement position of the communication hole 101 in the present embodiment), It is desirable that a larger number be provided upstream of the position of the density sensor 55. The reason is that, as described above, most of the scattered water is scattered in the direction in which the exhaust gas flows. Therefore, it is desirable to reduce stagnant water as much as possible on the upstream side from the position of the oxygen concentration sensor 55. is there.
[0067]
As described above, the reduction in the amount of water remaining in the first passage 50A and the suppression of the movement of water from the second passage 50B to the first passage 50A are combined, Splashing of water toward the detection element 55A and the heater 55B can be effectively suppressed. This can prevent water from touching the detection element 55A and the heater 55B. Therefore, it is possible to prevent them from being damaged. In addition, since the temperature of the detection element 55A can be prevented from lowering due to the adhesion of water, a decrease in detection accuracy can be prevented. As a result, stable exhaust air-fuel ratio control and purification performance can be realized.
[0068]
(Second embodiment)
FIG. 7 shows a second embodiment of the present invention. In the first embodiment, the configuration in which the upper and lower passages are formed by providing the partition plate in the exhaust passage has been described. On the other hand, the present embodiment shows a configuration in which upper and lower passages are formed by providing a branched exhaust pipe. The principle of the movement (one-way movement) of the condensed water between the upper and lower passages is the same as that of the first embodiment, and therefore the detailed description is omitted as appropriate. FIG. 7 is a part of a schematic sectional view of an exhaust pipe according to a second embodiment of the present invention.
[0069]
In the present embodiment, as shown in the figure, a branch pipe 110 is provided to form a branch passage that once branches a part of the exhaust passage and returns it to the original state. The branch pipe 110 forms an upper first passage 50A and a lower second passage 50B. Also in the present embodiment, an oxygen concentration sensor 55 is provided on the first passage 50A side.
[0070]
A plurality of (two in this case, two for simplicity) communicating pipes 111 and 112 for connecting the first passage 50A and the second passage 50B are provided between the main body of the exhaust pipe 50 and the branch pipe 110. Have been. A communication passage connecting the first passage 50A and the second passage 50B is formed by the inside of the communication tubes 111 and 112. These communication pipes 111 and 112 are arranged so as to be inclined downward as they go in the direction in which the exhaust gas flows.
[0071]
With the above configuration, a communication path similar to that of the first embodiment is formed in the present embodiment, and the water on the first passage 50A side is formed according to the same principle as that of the first embodiment. And the water in the second passage 50B can be prevented from moving to the first passage 50A, and the same effect can be obtained.
[0072]
(Third embodiment)
FIG. 8 shows a third embodiment of the present invention. In the second embodiment, the case has been described in which there is a gap between the branched pipe and the exhaust pipe main body, and the communication path is formed by a communication pipe connecting these pipes. On the other hand, in the present embodiment, there is no gap between the two pipes, the two pipes are separated by the pipe wall, and the communication path is formed by a communication hole formed in the wall. Show. FIG. 8 is a part of a schematic sectional view of an exhaust pipe according to a third embodiment of the present invention.
[0073]
In the present embodiment, as shown, a branch pipe 120 is provided to form a branch passage that once branches a part of the exhaust passage and returns it to the original state. The branch pipe 120 forms an upper first passage 50A and a lower second passage 50B. Also in the present embodiment, an oxygen concentration sensor 55 is provided on the first passage 50A side.
[0074]
In the present embodiment, the upper and lower pipes are configured to be separated by a pipe wall 121. The wall 121 is provided with a plurality of communication holes 122 that communicate the first passage 50A and the second passage 50B. The communication hole 122 forms a communication passage connecting the first passage 50A and the second passage 50B. These communication holes 122 are provided so as to be inclined downward as they go in the direction in which the exhaust gas flows.
[0075]
With the above configuration, a communication path similar to that of the first embodiment is formed in the present embodiment, and the water on the first passage 50A side is formed according to the same principle as that of the first embodiment. And the water in the second passage 50B can be prevented from moving to the first passage 50A, and the same effect can be obtained.
[0076]
(Fourth embodiment)
9 and 10 show a fourth embodiment. In the first embodiment, the configuration in which two passages are formed by providing the partition plate in the exhaust passage has been described. On the other hand, this embodiment shows a configuration in which two passages are formed by adopting a double pipe structure. The principle of the movement (one-way movement) of the condensed water between the two passages is the same as in the first embodiment, and a detailed description thereof will be omitted as appropriate. FIG. 9 is a partially broken perspective view of an exhaust pipe according to a fourth embodiment of the present invention. FIG. 10 is a part of a schematic sectional view of an exhaust pipe according to a fourth embodiment of the present invention.
[0077]
In the present embodiment, a small-diameter pipe 130 having a smaller diameter than the exhaust pipe 50 is provided concentrically with the exhaust pipe 50 in the exhaust pipe 50. The small-diameter pipe 130 forms a first passage 50A in the small-diameter pipe 130 and a second passage 50B formed by a gap between the small-diameter pipe 130 and the exhaust pipe 50. The positional relationship between the small-diameter pipe 130 and the oxygen concentration sensor 55 is the same as the positional relationship between the partition plate 100 and the oxygen concentration sensor 55 in the first embodiment. In the present embodiment, the oxygen concentration sensor 55 is provided so as to penetrate from the ceiling portion of the exhaust pipe 50 to the inside of the small-diameter pipe 130. Then, the portion of the detection element 55A and the heater 55B, which becomes a problem when touched by water, is disposed in the small diameter pipe 130. Therefore, the exhaust gas in the first passage 50A passes through the detection element 55A and the heater 55B, but the exhaust gas in the second passage 50B does not pass through the detection element 55A and the heater 55B.
[0078]
A plurality of communication holes 131 communicating the first passage 50A and the second passage 50B are provided in a lower portion of the small-diameter pipe 130. Below the communication hole 131, a wall 132 inclined downward is provided, and the communication hole 131 and the wall 132 form a communication passage connecting the first passage 50A and the second passage 50B. . That is, the lower part of the small-diameter pipe 130 corresponds to the partition plate in the first embodiment, and the communication holes 131 and the walls 132 are the same as those provided in the partition plate in the first embodiment. It is.
[0079]
With the above configuration, a communication path similar to that of the first embodiment is formed in the present embodiment, and the water on the first passage 50A side is formed according to the same principle as that of the first embodiment. And the water in the second passage 50B can be prevented from moving to the first passage 50A, and the same effect can be obtained.
[0080]
(Fifth embodiment)
FIGS. 11 and 12 show a fifth embodiment. FIGS. 11A and 11B are schematic views of an exhaust pipe according to a fifth embodiment of the present invention, in which FIG. 11A is a partially cutaway perspective view, and FIG. 11B is a schematic configuration cut perpendicular to the exhaust flow direction. It is sectional drawing. FIG. 12 is a part of a schematic sectional view of an exhaust pipe according to a fifth embodiment of the present invention.
[0081]
In the present embodiment, as shown, a first partition plate 141 and a second partition plate 142 that partition the exhaust passage up and down in the exhaust pipe 50 are provided. An upper first passage 50A and a lower second passage 50B are formed by these partition plates. The range in which these partition plates are provided and the positional relationship between these partition plates and the oxygen concentration sensor 55 are the same as those described in the first embodiment, and a description thereof will be omitted.
[0082]
The first partition plate 141 is disposed so as to be inclined downward from one end (the right end in FIG. 11B) in the width direction of the exhaust passage toward the other end (the left end in FIG. 11B). Have been. Further, the second partition plate 142 is disposed so as to be inclined downward from the other end in the width direction of the exhaust passage toward one end. In these partition plates, a gap is provided in the vertical direction between the first partition plate 141 and the second partition plate 142 as shown in the figure, and forms a communication passage 143 that connects the upper and lower passages. . On the other hand, in the width direction, no gap is provided between the first partition plate 141 and the second partition plate 142, and they are arranged so as to partially overlap.
[0083]
With the above configuration, water generated by condensing moisture in the exhaust gas on the first passage 50A side accumulates on the upper surface of the first partition plate 141 or the second partition plate 142. When the water droplets become large to some extent, they flow by gravity along the inclined surface on the upper surface side of each partition plate. Then, the water flowing through the first partition plate 141 falls on the second partition plate 142, and the water flowing through the second partition plate 142 passes through a communication passage 143 formed by a gap between the partition plates. Flows toward the second passage 50B.
[0084]
As described above, with the configuration of the present embodiment, the condensed water staying in the first passage 50A can be reduced. Therefore, it is possible to reduce the water scattered toward the oxygen concentration sensor 55 due to the flow of the vibration or the exhaust gas.
[0085]
In addition, water generated by condensing moisture in the exhaust gas on the second passage 50B side and water moved from the first passage 50A side stay on the floor of the second passage 50B. The water W2 retained in this manner may be scattered by vibration or exhaust. However, the scattered water is blocked by the lower surface of the first partition plate 141 or the second partition plate 142 and is not moved to the first passage 50A side.
[0086]
Thus, with the configuration of the present embodiment, it is possible to suppress the water scattered on the second passage 50B side from moving to the first passage 50A side. Therefore, it is possible to suppress the water scattered toward the oxygen concentration sensor 55 due to the vibration and the flow of the exhaust gas. In order to prevent the water scattered on the second passage 50B side from moving to the first passage 50A side, there is no gap in the width direction by the first partition plate 141 and the second partition plate 142. That is the condition. Therefore, between the first partition plate 141 and the second partition plate 142, a portion overlapping in the width direction is required in principle. The greater the overlapping portion, the greater the effect of suppressing the movement of the scattered water toward the first passage 50A.
[0087]
As described above, the reduction in the amount of water remaining in the first passage 50A and the suppression of the movement of water from the second passage 50B to the first passage 50A are combined, Splashing of water toward the detection element 55A and the heater 55B can be effectively suppressed. This can prevent water from touching the detection element 55A and the heater 55B. Therefore, it is possible to prevent them from being damaged. In addition, since the temperature of the detection element 55A can be prevented from lowering due to the adhesion of water, a decrease in detection accuracy can be prevented. As a result, stable exhaust air-fuel ratio control and purification performance can be realized.
[0088]
(Sixth embodiment)
13 and 14 show a sixth embodiment. FIG. 13 is a partially cutaway perspective view of an exhaust pipe according to a sixth embodiment of the present invention. FIG. 14 is a part of a schematic sectional view of an exhaust pipe according to a sixth embodiment of the present invention.
[0089]
In the present embodiment, as shown, a partition plate 150 is provided in the exhaust pipe 50 to partition the exhaust passage up and down. The partition plate 150 forms an upper first passage 50A and a lower second passage 50B. The range in which the partition plate 150 is provided and the positional relationship between the partition plate 150 and the oxygen concentration sensor 55 are the same as those described in the first embodiment, and a description thereof will be omitted.
[0090]
The partition plate 150 is provided with a plurality of communication holes 151 that communicate the first passage 50A and the second passage 50B. In the first embodiment, an inclined wall is provided below the communication hole, whereas in the present embodiment, such a wall is not provided, except that the wall is not provided. Since this is the same as the case of the embodiment, detailed description thereof will be omitted.
[0091]
Also in the configuration of the present embodiment, the water on the first passage 50A side falls to the second passage 50B side through the communication hole 151, so that the water condensed on the first passage 50A side is positively discharged on the second passage 50B side. Can be moved to Further, it is possible to suppress the water scattered from the second passage 50B side from moving to the first passage 50A side in a portion of the partition plate 150 where the communication hole 151 is not provided.
[0092]
Therefore, also in the present embodiment, the effect of reducing the water staying in the first passage 50A and the effect of suppressing the movement of water from the second passage 50B to the first passage 50A can be expected. The same effect as that of the embodiment can be expected.
[0093]
(Seventh embodiment)
15 and 16 show a seventh embodiment. FIG. 15 is a partially broken perspective view of an exhaust pipe according to a seventh embodiment of the present invention. FIG. 16 is a part of a schematic sectional view of an exhaust pipe according to a seventh embodiment of the present invention.
[0094]
In this embodiment, as shown, a partition plate 160 is provided in the exhaust pipe 50 to partition the exhaust passage up and down. The partition plate 160 forms an upper first passage 50A and a lower second passage 50B. The range in which the partition plate is provided, and the positional relationship between the partition plate and the oxygen concentration sensor 55 are the same as those described in the first embodiment, and a description thereof will be omitted.
[0095]
The partition plate 160 according to the present embodiment is disposed so as to be inclined downward toward the downstream side (the direction in which exhaust gas flows).
[0096]
According to the configuration of the present embodiment, the water condensed on the first passage 50A side flows downward due to gravity along the slope of the partition plate 160 when the water droplets become large to some extent, and flows to the outside of the first passage 50A. Swept away. In addition, even if the droplets are small enough not to flow along the partition plate 160 and remain attached to the partition plate 160, the partition plate 160 is inclined downward. It is difficult for the exhaust to directly hit the water droplets, and it is difficult for water to scatter upward. The water scattered on the second passage 50B side hits the lower surface of the partition plate 160, and is reliably prevented from moving to the first passage 50A side.
[0097]
As described above, in the present embodiment, the effect of reducing the stagnation of water in the first passage 50A is expected, and the effect of suppressing the scattering of water in the first passage 50A is expected. Then, it is possible to reliably prevent the water in the second passage 50B from moving to the first passage 50A.
[0098]
(Other)
By appropriately combining the characteristic configurations of the embodiments described above, a synergistic effect can be expected. For example, it is conceivable to form the communication path constituted by the communication hole and the wall shown in the first embodiment in the two partition plates shown in the fifth embodiment. Further, it is conceivable to form the communication path formed by the communication hole and the wall shown in the first embodiment on the inclined partition plate shown in the seventh embodiment.
[0099]
Further, in each of the embodiments described above, an oxygen concentration sensor has been described as an example of a sensor for detecting components in exhaust gas. However, the present invention is not limited to the oxygen concentration sensor, and can be effectively applied to sensors that detect components in various exhaust gases, such as a NOx sensor, an HC sensor, and a CO sensor. Further, in the above embodiment, the case where the internal combustion engine is a diesel engine has been described as an example, but the present invention is of course applicable to the case of a gasoline engine.
[0100]
【The invention's effect】
As described above, according to the present invention, the stagnation of water near the sensor element can be reduced. Further, scattering of water near the sensor element can be suppressed. And by these, it can prevent that a sensor element touches water. In addition, this can prevent the sensor element from being damaged and prevent the detection accuracy of the sensor from deteriorating.
[Brief description of the drawings]
FIG. 1 is a main configuration diagram of an internal combustion engine provided with an exhaust pipe according to the present embodiment.
FIG. 2 is a schematic configuration diagram showing a main part of an oxygen concentration sensor.
FIG. 3 is a graph showing a relationship between applied voltage and current between two electrodes of an oxygen concentration sensor.
FIG. 4 is a graph showing a correspondence relationship between a limiting current value of an oxygen concentration sensor and an oxygen concentration.
FIG. 5 is a schematic view of an exhaust pipe according to the first embodiment of the present invention.
FIG. 6 is a part of a schematic cross-sectional view of the exhaust pipe according to the first embodiment of the present invention.
FIG. 7 is a part of a schematic cross-sectional view of an exhaust pipe according to a second embodiment of the present invention.
FIG. 8 is a part of a schematic cross-sectional view of an exhaust pipe according to a third embodiment of the present invention.
FIG. 9 is a partially broken perspective view of an exhaust pipe according to a fourth embodiment of the present invention.
FIG. 10 is a part of a schematic sectional view of an exhaust pipe according to a fourth embodiment of the present invention.
FIG. 11 is a schematic view of an exhaust pipe according to a fifth embodiment of the present invention.
FIG. 12 is a part of a schematic cross-sectional view of an exhaust pipe according to a fifth embodiment of the present invention.
FIG. 13 is a partially broken perspective view of an exhaust pipe according to a sixth embodiment of the present invention.
FIG. 14 is a part of a schematic sectional view of an exhaust pipe according to a sixth embodiment of the present invention.
FIG. 15 is a partially broken perspective view of an exhaust pipe according to a seventh embodiment of the present invention.
FIG. 16 is a part of a schematic cross-sectional view of an exhaust pipe according to a seventh embodiment of the present invention.
[Explanation of symbols]
1 engine (internal combustion engine)
11 cylinder
11a Ceiling
12 piston
12a top surface
13 Combustion chamber
14 Connecting rod
19 Intake valve
20 Exhaust valve
40 intake pipe
41 Intake port
42 Throttle valve
42a actuator
50 exhaust pipe
50A 1st passage
50B 2nd passage
51 Exhaust port
54 Catalyst casing
55h Gas diffuser
55d gas diffuser
55 Oxygen concentration sensor
55a, 55b, 55c, 55f Plate
55d, 55e electrode
55g heating wire
55A detection element
55B heater
60 fuel injection valve
100 partition board
101 communication hole
102 wall
102a slope
102b Blocking surface
103 Upstream end
110 branch pipe
111, 112 communication pipe
120 branch pipe
121 wall
122 communication hole
130 Small diameter pipe
131 communication hole
132 walls
141 1st partition board
142 Second partition plate
143 connecting passage
150 Partition plate
151 communication hole
160 divider

Claims (8)

A first passage that forms a flow of exhaust gas through a sensor element portion of the sensor that detects a component in the exhaust gas;
A second passage that forms a flow of exhaust gas that does not pass through the sensor element from the upstream side to the downstream side of the sensor element;
The water formed by condensing the moisture in the exhaust gas on the first passage side is moved to the second passage side, and the water formed by condensing the moisture in the exhaust gas on the second passage side and moving from the first passage side. An exhaust pipe, comprising: a communication passage that communicates the first passage with the second passage, wherein the exhausted water is suppressed from moving to the first passage side. A first passage that forms a flow of exhaust gas through a sensor element portion of the sensor that detects a component in the exhaust gas;
A second passage that forms a flow of exhaust gas that does not pass through the sensor element from the upstream side to the downstream side of the sensor element;
A communication passage having an inclined portion for guiding water produced by condensation of moisture in the exhaust gas to the second passage side on the first passage side, the communication passage connecting the first passage and the second passage;
An exhaust pipe, which comprises: a shielding portion that blocks entry of water scattered from the second passage side into the communication passage. A first passage that forms a flow of exhaust gas through a sensor element portion of the sensor that detects a component in the exhaust gas;
A second passage that forms a flow of exhaust gas that does not pass through the sensor element from the upstream side to the downstream side of the sensor element;
A first passage having an inclined portion for guiding water produced by condensing moisture in the exhaust gas to the second passage on the first passage side, and having an opening toward the second passage facing downstream; And a communication passage communicating with the second passage. 4. The exhaust pipe according to claim 1, wherein the opening on the first passage side of the communication passage is provided upstream of the sensor element unit. 5. A sensor provided at the upper part of the exhaust passage, which includes a sensor element portion of a sensor for detecting a component in the exhaust gas, or a passage upstream and downstream of the vicinity of the sensor element portion. Equipped with a partition plate,
On the partition plate,
A communication hole communicating the upper and lower passages,
Below the communication hole, the upper surface is formed by an inclined surface that guides water formed by condensing moisture in the exhaust gas to the lower passage on the upper passage side, and the lower surface thereof is scattered from the lower passage side. A wall formed of a blocking surface that blocks entry into the communication hole. A sensor provided at an upper portion of the exhaust passage, the sensor including a sensor element portion of the sensor for detecting a component in the exhaust gas, or one end in the width direction of the exhaust passage at an upstream side of the vicinity of the sensor element portion. A first partition plate having an inclined portion inclined downward toward the other end side, and a second partition plate having an inclined portion inclined downward from the other end in the width direction of the exhaust passage toward one end side. Provided, and these partitions partition the inside of the exhaust passage up and down,
In these partition plates, a clearance is provided between the first partition plate and the second partition plate in the vertical direction to form a communication passage communicating vertically with the exhaust passage, and the first partition is formed in the width direction. An exhaust pipe, wherein the exhaust pipe is arranged so that there is no gap between the plate and the second partition plate. The exhaust pipe according to claim 5, wherein an opening to the upper passage of the communication hole is provided upstream of the sensor element. An exhaust pipe according to any one of claims 1 to 7 is provided,
An exhaust gas purifying apparatus for an internal combustion engine, wherein an exhaust gas component is controlled based on a detection result by a sensor disposed in the exhaust pipe.

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