JP2018112072A - Exhaust system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the breakage of a sensor when fully closing the valve element of an exhaust throttle valve and injecting liquid from an injector.SOLUTION: An exhaust system for an internal combustion engine includes an exhaust pipe 5 defining an exhaust passage 6, an exhaust throttle valve 7 provided in the exhaust pipe, a sensor 8 provided in the exhaust pipe at the downstream side of the exhaust throttle valve, and an injector 9 provided in the exhaust pipe at the downstream side of the sensor for injecting liquid L into the exhaust passage, the exhaust throttle valve having a valve element 7A arranged in the exhaust passage, the valve element having a valve element hole 60 to be directed to the sensor or its vicinity when fully closed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust system for an internal combustion engine.

  In an exhaust system of an internal combustion engine such as a diesel engine, an exhaust throttle valve, a sensor, and an injector may be provided in the exhaust pipe in order from the upstream side. As is well known, an exhaust throttle valve is a device that opens and closes an exhaust passage in an exhaust pipe and restricts the exhaust passage to a substantially fully closed state while allowing a small amount of exhaust gas to pass when the exhaust passage is fully closed. The sensor is, for example, a lambda sensor for detecting an excess air ratio (λ) of exhaust gas. The injector is a device that injects liquid fuel into the exhaust passage for the purpose of raising the temperature of exhaust gas supplied to the particulate filter, for example, during regeneration of the particulate filter installed downstream thereof.

JP 2011-69321 A

  By the way, in such an exhaust system, a state in which fuel is injected from the injector may occur while the valve body of the exhaust throttle valve is fully closed. In this case, a gap is formed between at least a part of the outer peripheral edge of the valve body and the exhaust pipe, and the exhaust gas flows through the gap.

  However, due to the exhaust gas passing through the gap, there may be a backflow of exhaust gas coming from the downstream side of the sensor toward the sensor. Then, a part of the spray or droplet of the fuel injected from the injector rides on the reverse flow and goes to the sensor, adheres to the sensor, and may damage the sensor.

  Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust system for an internal combustion engine that can prevent damage to the sensor when the valve body of the exhaust throttle valve is fully closed and liquid is injected from the injector. Is to provide.

According to one aspect of the invention,
An exhaust pipe defining an exhaust passage;
An exhaust throttle valve provided in the exhaust pipe;
A sensor provided downstream of the exhaust throttle valve in the exhaust pipe;
An injector that is provided downstream of the sensor in the exhaust pipe and injects liquid into the exhaust passage;
With
The exhaust throttle valve has a valve body disposed in the exhaust passage, and the valve body has a valve body hole directed to the sensor or the vicinity thereof when fully closed. An exhaust system is provided.

Preferably, when the valve body is fully closed, a gap is formed between at least a part of the outer peripheral edge of the valve body and the exhaust pipe,
The exhaust system is configured to suppress the backflow of the exhaust gas generated due to the exhaust gas that has passed through the gap and directed toward the sensor by the flow of the exhaust gas that has passed through the valve body hole.

Preferably, the sensor has a detection element exposed in the exhaust passage,
The valve body hole is directed to the detection element or the vicinity thereof when the valve body is fully closed.

  Preferably, the sensor is any one of a lambda sensor, a NOx sensor, a PM sensor, and a pressure sensor.

  Preferably, the valve body is any one of a butterfly valve body, a poppet valve body, a swing valve body, and a shutter valve body.

  Preferably, the liquid is a fuel.

Preferably, the exhaust system is
An oxidation catalyst provided downstream of the injector in the exhaust pipe;
A particulate filter provided downstream of the oxidation catalyst in the exhaust pipe;
And a control unit for controlling the valve body of the exhaust throttle valve to be fully closed and injecting the fuel as the liquid from the injector during idle regeneration of the particulate filter.

  According to the present invention, it is possible to suppress damage to the sensor when the valve body of the exhaust throttle valve is fully closed and fuel is injected from the injector.

1 is a schematic diagram illustrating a configuration of an internal combustion engine according to an embodiment. It is sectional drawing which shows the structure of the exhaust system which concerns on this embodiment. It is III-III sectional drawing of FIG. It is sectional drawing similar to FIG. 2 for demonstrating the effect | action of this embodiment. It is sectional drawing similar to FIG. 3 for demonstrating the effect | action of this embodiment. It is sectional drawing which shows a 1st modification. It is sectional drawing which shows a 2nd modification. It is sectional drawing which shows a 3rd modification. It is sectional drawing which shows a 4th modification.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a configuration of an internal combustion engine according to the present embodiment. An internal combustion engine (engine) 1 in the present embodiment is a compression ignition internal combustion engine, that is, a diesel engine as a vehicle power source mounted on a vehicle. The vehicle is a large vehicle such as a truck, but the type, type, application, etc. of the vehicle is not particularly limited, and may be a small vehicle such as a passenger car. You can also change the engine type as needed. For example, the engine may be a gasoline engine. Although the illustrated example shows an in-line four-cylinder engine, the cylinder arrangement type, the number of cylinders, and the like of the engine are arbitrary.

  Each cylinder of the engine 1 is provided with an in-cylinder injector 2 for directly injecting fuel into the cylinder. The engine 1 is also provided with an exhaust manifold 3 for collecting exhaust gases discharged from the exhaust ports of the cylinders. The inlet of the turbine 4T of the turbocharger 4 is connected to the outlet of the exhaust manifold 3. An upstream end portion of the exhaust pipe 5 is connected to an outlet portion of the turbine 4T, and the exhaust pipe 5 defines an exhaust passage 6 having a circular cross section therein. In addition, although 4C shows the compressor of the turbocharger 4, since this embodiment has the characteristics in the structure of an exhaust system, description and illustration are abbreviate | omitted about the structure of an intake system, and the structure of an exhaust system is explained in full detail below.

  In the exhaust pipe 5, an exhaust brake valve 7, which is an example of an exhaust throttle valve, is provided on the downstream side of the turbine 4 T. A lambda sensor 8 as a sensor is provided on the downstream side of the exhaust brake valve 7. An exhaust pipe injector 9 as an injector is provided on the downstream side. The exhaust brake valve 7 includes a valve body 7A disposed in the exhaust passage 6 and an actuator 7B that opens and closes the valve body 7A. In the present embodiment, a butterfly valve body 7A is used, and a pneumatically operated actuator 7B is used. The lambda sensor 8 is a sensor for detecting the excess air ratio λ or the air-fuel ratio of the exhaust gas. The exhaust pipe injector 9 is a device that injects fuel as liquid into the exhaust passage 6. The exhaust brake valve 7 is a device that opens and closes the exhaust passage 6 in the exhaust pipe 5 and restricts the exhaust passage 6 to be substantially fully closed while allowing a small amount of exhaust gas to pass when fully closed.

  The exhaust brake valve 7 is disposed at a position immediately after the turbine 4T. Further, the exhaust brake valve 7, the lambda sensor 8, and the exhaust pipe injector 9 are arranged close to each other, and these are laid out in a compact layout.

  In the exhaust pipe 5, an oxidation catalyst (DOC) 10, a particulate filter (hereinafter referred to as “DPF”) 11, a NOx catalyst 12, and ammonia oxidation are sequentially arranged from the upstream side to the downstream side relatively far from the exhaust pipe injector 9. A catalyst 13 is provided. These oxidation catalyst 10, DPF 11, NOx catalyst 12, and ammonia oxidation catalyst 13 each constitute an aftertreatment device.

The oxidation catalyst 10 oxidizes and purifies unburned components (hydrocarbon HC and carbon monoxide CO) in the exhaust gas, raises the temperature of the exhaust gas with the reaction heat at this time, and reduces NO in the exhaust gas. It is oxidized to NO _2. The DPF 11 is a so-called continuous regeneration type DPF with a catalyst, which collects particulate matter (PM) contained in the exhaust gas and continuously burns and removes the collected PM. In this embodiment, the NOx catalyst 12 is a selective reduction type NOx catalyst (SCR), and when urea water is added from the addition valve 14 installed on the upstream side of the NOx catalyst 12, ammonia derived from the urea water. Using NO as a reducing agent, NOx in the exhaust is reduced and removed. The ammonia oxidation catalyst 13 oxidizes and purifies excess ammonia discharged from the NOx catalyst 12.

  In the present embodiment, an electronic control unit (hereinafter referred to as “ECU”) 100 serving as a control unit or a controller is provided. ECU 100 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like. The ECU 100 is configured to control the in-cylinder injector 2, the exhaust brake valve 7 (particularly, the actuator 7B), the exhaust pipe injector 9, and the addition valve 25 in accordance with a program stored in advance.

  Regarding the sensors, in addition to the lambda sensor 8 described above, the rotational speed of the engine, specifically, the rotational speed sensor 21 for detecting the rotational speed per minute (rpm), and the accelerator for detecting the accelerator opening. An opening degree sensor 22 is provided. Also provided are a differential pressure sensor 23 for detecting the differential pressure before and after the DPF 11, and a regeneration switch 24 that is manually turned on when manual regeneration described later is executed. Output signals from these sensors are sent to the ECU 100.

  The ECU 100 executes various controls and arithmetic processing of the engine 1 using the value of the excess air ratio detected by the lambda sensor 8. For example, the ECU 100 controls the EGR using the detected value.

  In addition, the ECU 100 determines that the fuel injection amount of the in-cylinder injector 2 is zero when the fuel cut execution condition that the accelerator opening is zero and the engine speed is higher than a predetermined return speed during vehicle deceleration is satisfied. And decelerate the vehicle with the engine brake. At this time, if the operating condition of the exhaust brake valve 7 is satisfied, the exhaust brake valve 7 is also operated to increase the engine braking force. At this time, the ECU 100 sends a valve closing instruction signal to the actuator 7B to control the valve body 7A to be fully closed. On the other hand, when the operating condition of the exhaust brake valve 7 is not satisfied, the ECU 100 sends a valve opening instruction signal to the actuator 7B to control the valve body 7A to be fully open, thereby setting the exhaust brake valve 7 to the non-operating state. The operating condition of the exhaust brake valve 7 may be satisfied, for example, when a fuel cut execution condition is satisfied and an exhaust brake switch (not shown) is on, and not satisfied at other times.

  Further, the ECU 100 estimates the amount of PM accumulated on the DPF 11 based on the differential pressure detected by the differential pressure sensor 23, that is, the PM accumulation amount. Then, when it is determined that the estimated amount of accumulated PM exceeds a predetermined allowable upper limit value, filter regeneration control for forcibly removing the accumulated PM and recovering the PM collecting ability of the DPF 11 is executed. During this filter regeneration control, the ECU 100 injects fuel from the exhaust pipe injector 9. Then, this fuel is burned by the oxidation catalyst 10 and the temperature of the exhaust gas is raised in the oxidation catalyst 10. High temperature exhaust gas is discharged from the oxidation catalyst 10. This high-temperature exhaust gas is supplied to the DPF 11, and the deposited PM in the DPF 11 is removed by combustion. On the other hand, when ECU 100 determines that the estimated PM accumulation amount has fallen below a predetermined allowable lower limit value lower than the allowable upper limit value, ECU 100 stops the filter regeneration control.

  The above is an example of automatic regeneration in which regeneration of the DPF 11 is automatically performed, but manual regeneration may be performed in addition to this. That is, when the regeneration switch 24 is turned on, the ECU 100 forcibly executes the filter regeneration control even if the estimated PM accumulation amount does not exceed the allowable upper limit value. However, when the PM accumulation amount exceeds the allowable upper limit value, a warning device (not shown) (not shown) is activated, and the driver normally turns on the regeneration switch 24 in response to this. Accordingly, the timing when the regeneration switch 24 is turned on is often the timing when the PM accumulation amount exceeds the allowable upper limit value.

  The NOx catalyst 12 may be an NOx storage reduction catalyst (referred to as LNT) instead of the SCR. In this case, LNT regeneration control for removing NOx and sulfur components stored in the LNT may be performed. At this time, fuel may be injected from the exhaust pipe injector 9 as in the filter regeneration control.

  Next, the configuration of the exhaust system including the exhaust brake valve 7, the lambda sensor 8, and the exhaust pipe injector 9 will be described with reference to FIGS. 3 is a cross-sectional view taken along the line III-III in FIG.

  As described above, in the exhaust pipe 5, the exhaust brake valve 7, the lambda sensor 8, and the exhaust pipe injector 9 are arranged in this order from the upstream side in close proximity to each other. The exhaust pipe 5 has a bent shape in the illustrated portion, but the shape is arbitrary. Here, the exhaust pipe 5 is not limited to being formed of a pipe material, and may be a cast product, for example. Any member that defines the exhaust passage 6 through which the exhaust gas flows can be used as the exhaust pipe 5. The exhaust passage 6 extends along a passage axis C1 that is the central axis thereof.

  The exhaust brake valve 7 includes a butterfly valve body 7A that is disposed in the exhaust passage 6 and can be opened and closed, and a valve shaft 31 to which the valve body 7A is fixed. The valve shaft 31 is attached to the valve body 7A along the diameter of the circular plate-like valve body 7A, and both ends thereof are rotatably supported by the bearing portions 32 of the exhaust pipe 5. One end portion (upper end portion in FIG. 2) of the valve shaft 31 is connected to the above-described actuator 7B at a position outside the figure and is rotated by the actuator 7B. By this rotation, the valve body 7A can be rotated around the valve axis C2 between the fully closed position shown in FIGS. 2 and 3 and the fully open position shown in phantom in FIG. is there.

  The lambda sensor 8 includes a sensor body 35, a detection element 36 protruding from the tip of the sensor body 35, a sensor cover 37 fixed to the sensor body 35 and covering the detection element 36, and a plurality of sensors provided on the sensor cover 37. And a cover hole 38. A detection unit 39 is formed by the detection element 36 and the sensor cover 37. The detection element 36 is exposed in the exhaust passage 6 through the cover hole 38. The lambda sensor 8 is attached to the exhaust pipe 5 so that the detection element 36 and thus the detection unit 39 are disposed in the exhaust passage 6.

  The method of attaching the lambda sensor 8 is arbitrary. In the present embodiment, a sensor mounting boss 40 is provided on the exhaust pipe 5 so as to protrude outward, and a sensor mounting hole 41 is provided through the center of the boss 40. A female screw 42 is formed at the base end of the sensor mounting hole 41. The sensor body 35 is provided with a male screw 43 and a tool engaging portion 44 for engaging a tool such as a spanner. The tool is engaged with the tool engaging portion 44, and the male screw 43 is fastened to the female screw 42, whereby the lambda sensor 8 is attached to the boss 40 and the exhaust pipe 5.

  In this attached state, the detection part 39 is accommodated in the sensor attachment hole 41 with a gap therebetween, and only the tip part of the detection part 39 projects from the sensor attachment hole 41 into the exhaust passage 6. However, since the sensor mounting hole 41 communicates with the exhaust passage 6, the entire detection unit 39 to the detection element 36 are substantially exposed in the exhaust passage 6. The sensor cover 37 suppresses foreign matter in the exhaust passage 6 from adhering to the detection element 36. The sensor body 35, the detection element 36, the sensor cover 37, and the sensor mounting hole 41 are coaxial with the sensor axis C <b> 3 that is the central axis of the lambda sensor 8. As shown in FIG. 3, the sensor axis C <b> 3 is generally inclined toward the passage axis C <b> 1 and slightly inclined toward the downstream side of the exhaust passage 6.

  Since the internal structure and detection principle of the lambda sensor 8 are well known, a detailed description is omitted. The detection element 36 includes an electric heater such as a ceramic heater, and the detection element 36 is heated to a predetermined high temperature (for example, about 700 ° C.) at which the lambda sensor 8 can detect the excess air ratio (that is, becomes active). It has become so. The ECU 100 controls the heater on / off, and thus the temperature of the detection element 36.

  The exhaust pipe injector 9 has a nozzle hole 45 at its tip surface, and the fuel L is injected from the nozzle hole 45 into the exhaust passage 6 at a predetermined spray angle α and injection pressure. The nozzle hole 45 or the spray center C4 is inclined slightly toward the passage axis C1 and toward the downstream side of the exhaust passage 6. The exhaust pipe injector 9 is disposed coaxially with the spray center C4.

  The method of attaching the exhaust pipe injector 9 is also arbitrary. In the present embodiment, the exhaust pipe 5 is provided with an injector mounting boss 46 protruding outward, and an injector mounting hole 47 is provided through the center of the boss 46. A plurality of female screw holes 48 are provided in the base end surface of the boss 46. In the exhaust pipe injector 9, a flange 49 that protrudes toward the diameter expansion side at a position slightly proximal to the nozzle hole 45, and a plurality of bolt insertion holes 50 provided in the flange 49 corresponding to the female screw holes 48 are provided. Is provided. The flange 49 is seated on the base end surface of the boss 46, and after the plurality of bolts 51 are inserted into the bolt insertion holes 50, the exhaust pipe injector 9 is attached to the boss 46 and the exhaust pipe 5 by being tightened into the female screw holes 48. It is done.

  As shown in FIG. 2, the exhaust passage 6 is bent toward the diagonally lower side in FIG. 2 and then gently curved toward the upper side in FIG. 2 as it goes downstream or forward from the position of the valve body 7A. Has been. The detection part 39 and the sensor mounting hole 41 of the lambda sensor 8 are arranged at a position immediately after the former bent part. The exhaust pipe injector 9 is generally disposed at the position of the latter curved portion.

  If the left side in FIG. 2 is defined as the front, the right side is the rear, the front side in the thickness direction of the paper is defined as left, the back side in the thickness direction of the paper is defined as right, the upper side is defined as up, and the lower side is defined as down. The exhaust pipe injector 9 is arranged on the lower side of the exhaust pipe 5, and the phase around the passage axis C1 of the two differs by about 90 °. The valve shaft C2 extends in the vertical direction.

  2 and 3, the valve body 7A of the exhaust brake valve 7 is provided with a plurality of holes penetrating in the thickness direction, that is, a valve body hole 60. These valve body holes 60 are arranged so as to be directed to the lambda sensor 8, particularly the detection element 36 or the vicinity thereof, when the valve body 7A is fully closed.

  In the present embodiment, the number of valve body holes 60 is three, but the number is arbitrary, and may be one, two, four or more. In the present embodiment, the three valve element holes 60 are arranged in parallel in parallel with each other at equal intervals in the vertical direction, and one of the centers is located at the same height as the passage axis C1 and is substantially the same as the lambda sensor 8. It is arranged at the height position. Further, the three valve body holes 60 are arranged on the right side, that is, on the installation side of the lambda sensor 8 at an equal distance from the valve shaft C2 orthogonal to the passage shaft C1. Thereby, compared with the case where it arrange | positions to the non-installation side (left side) of the lambda sensor 8, the valve body hole 60 can be brought closer to the lambda sensor 8. FIG. But the installation position of the valve body hole 60 can also be changed, for example, you may arrange | position to the non-installation side (left side) of the lambda sensor 8. FIG.

  FIG. 3 shows the hole axis C5 of the central valve element hole 60. FIG. As can be seen from this, the valve body hole 60 of the present embodiment is directed to the position near and behind the sensor mounting hole 41 in detail. However, this directing direction can also be finely corrected. For example, it may be directed to a rearward position, may be directed directly to the sensor cover 37 to the detection unit 39, or may be directed to the cover hole 38.

  In this embodiment, the valve body hole 60 is extended | stretched along the thickness direction of 7 A of valve bodies. However, this extension direction can also be changed, and the extension direction may be inclined at a predetermined inclination angle with respect to the thickness direction.

  As can be seen from FIG. 2, the uppermost and lowermost two valve element holes 60 are directed to a position higher and lower than the sensor mounting hole 41 and to a position immediately rearward thereof. However, this directing direction can also be finely corrected. For example, the directing direction may be directed directly to the sensor cover 37 or the detection unit 39 and may be directed to the cover hole 38 after being made non-parallel to one of the centers. The sensor mounting hole 41 may be directed to a higher position and a lower position.

  Any one or two of these three valve body holes 60 may be omitted.

  Next, the operation of this embodiment will be described.

  As shown in FIGS. 4 and 5, in the exhaust system of the present embodiment, the valve body 7 </ b> A of the exhaust brake valve 7 is fully closed, while a situation in which the fuel L is injected from the exhaust pipe injector 9 may occur. . This situation is, for example, a situation where the above-described filter regeneration control is executed during idling of the engine 1, that is, a situation where idle regeneration of the DPF 11 is executed.

  During idle regeneration of the DPF 11, the accelerator opening is zero (0%) corresponding to the accelerator pedal fully closed, and the ECU 100 causes the engine 1 to perform an idling operation in response to the output signal of the accelerator opening sensor 22 indicating this. In many cases, the vehicle is stopped, the engine speed is lower than the return speed, the fuel cut execution condition is not satisfied, and the fuel cut is not executed. The ECU 100 sets the target idle speed to a slightly higher speed than the specified number, and controls the engine speed to the higher target idle speed.

  Then, the ECU 100 controls the exhaust brake valve 7 to be fully closed. Then, the exhaust pressure upstream of the fully closed valve body 7A increases, and the load on the engine 1 increases. By the cooperative action of the increase in idle speed and the increase in load, the fuel injection amount of the in-cylinder injector 2 is increased, and exhaust gas having a temperature higher than that during normal idling operation is discharged from the in-cylinder. As a result, the exhaust temperature can be raised even during idling when the exhaust temperature is relatively low. This is advantageous for the regeneration of the DPF 11. It should be noted that idle regeneration can be executed at any time of automatic regeneration and manual regeneration. Thus, the exhaust brake valve 7 can be used for another purpose of increasing the temperature of the exhaust gas in addition to the original purpose of increasing the engine brake force, that is, the exhaust brake.

  As shown in FIGS. 4 and 5, when the valve body 7 </ b> A is fully closed, a relatively narrow gap 62 is formed between at least a part of the outer peripheral edge 61 of the valve body 7 </ b> A and the exhaust pipe 5. More specifically, a relatively narrow radial gap 62 is formed between substantially the entire circumference of the outer peripheral edge 61 of the valve body 7A and the inner peripheral surface 63 of the exhaust pipe 5. On the other hand, the exhaust gas G whose pressure has been increased upstream or in front of the valve body 7A flows downstream through the gap 62 and the valve body hole 60 formed through the valve body 7A.

  At this time, as shown by arrows in FIGS. 4 and 5, the flow F1 of the exhaust gas that has passed through the gap 62 flows along the inner peripheral surface 63 of the exhaust pipe 5 for a while, but eventually the inner peripheral surface of the exhaust pipe. A separation flow F <b> 2 that separates from 63 is generated. The separated flow F2 is directed toward the center of the exhaust passage 6, that is, toward the passage axis C1, and then generates a reverse flow F3 that flows in a direction opposite to the flow direction of the exhaust gas G. Then, due to the separation flow F2, a swirling flow F4 is generated at a location near the lambda sensor 8 in the exhaust passage 6. The swirl flow F4 is a flow that goes in the flow direction of the exhaust gas G, that is, the forward flow direction on the radially outer side of the exhaust passage 6, but goes in the reverse flow direction on the radially inner side of the exhaust passage 6. This swirl flow F4 can also be regarded as a kind of the backflow F3.

  The backflow F <b> 3 is a flow that comes from the downstream side of the lambda sensor 8 toward the lambda sensor 8. On the other hand, when the fuel L is injected from the exhaust pipe injector 9 at this time, a part L1 on the upstream side of the spray or droplet of the fuel L rides on the backflow F3 toward the lambda sensor 8. A part L 1 of the fuel spray may enter the sensor cover 37 from the cover hole 38 of the lambda sensor 8 and adhere to the detection element 36. Since the detection element 36 is heated by the heater and becomes a high temperature, when a part L1 of the fuel spray which is a liquid adheres to the detection element 36, the element temperature rapidly decreases at the adhesion portion, and due to thermal stress concentration. There is a possibility that the detection element 36 is cracked (this is called element cracking). Thus, if a part L1 of the fuel spray adheres to the lambda sensor 8, particularly the detection element 36, the lambda sensor 8 may be damaged.

  However, in the present embodiment, the flow F5 of the exhaust gas that has passed through the valve body hole 60 flows toward the lambda sensor 8. Therefore, the flow F5 pushes back and suppresses the reverse flow F3 that is directed toward the lambda sensor 8, and The swirl flow F4 around the lambda sensor 8 can be weakened. As a result, part of the fuel spray L1 is restrained from riding on the backflow F3 toward the lambda sensor 8, and part of the fuel spray L1 enters the sensor cover 37 and adheres to the detection element 36. Can be suppressed. And damage of the lambda sensor 8 can be effectively suppressed by element cracking.

  In the present embodiment, as shown in FIG. 5, the central valve body hole 60 is directed to the position near and behind the sensor mounting hole 41 and the lambda sensor 8, so that the flow F <b> 5 that has passed through the valve body hole 60 is You can reach that position. Therefore, the flow F5 after passing through the valve body hole 60 together with the flow F1 flowing along the exhaust pipe inner peripheral surface 63 after passing the gap 62 on the sensor side is applied to the lambda sensor 8 from the rear, and the inflow adhesion of the backflow F3 and fuel spray is applied. It can be effectively suppressed.

  Also, as can be seen from FIG. 4, the flow F5 that has passed through the uppermost and lowermost valve element holes 60 becomes a flow that passes through the upper side and the lower side of the lambda sensor 8, so that the flow F5 causes a reverse flow F3. It is also possible to effectively suppress the flow of fuel spray that rides from the upper side and the lower side.

  Further, the flow F5 that has passed through the valve body hole 60 can suppress the adhesion of dust to the sensor cover 37, and the dust clogging of the cover hole 38 can be suppressed. The valve body hole 60 also has a function of adjusting the upstream pressure thereof to a predetermined value when the valve body 7A is fully closed. The size, number, shape, arrangement, etc. of the valve body hole 60 are optimally determined so that the above-described effects can be obtained.

  Since the valve body hole 60 is disposed on the right side with respect to the valve shaft C2, that is, on the side where the lambda sensor 8 is installed, the valve body hole 60 is brought closer to the lambda sensor 8 and the flow reaching the lambda sensor 8 compared to the case where the valve body hole 60 is not. The flow rate of F5 can be increased. Accordingly, the backflow F3 can be effectively suppressed, and dust adhering to the sensor cover 37 can be effectively suppressed.

  Next, a modification of this embodiment will be described. In addition, the same code | symbol is attached | subjected in the figure to the part similar to the above-mentioned basic embodiment, and description is omitted, and the difference from a basic embodiment is mainly demonstrated below.

  In the first modification shown in FIG. 6, the valve body 71 of the exhaust brake valve 7 is a poppet type valve body. That is, the valve shaft 72 is fixed to the center of the valve body 71, and the valve body 71 is opened and closed by moving the valve shaft 72 in the axial direction as shown by the arrow by the actuator (not shown). . The exhaust pipe 5 has a ring-shaped valve seat 73 fixed to the inner peripheral surface 63 thereof. FIG. 6 shows the valve body 71 when fully closed. At this time, a relatively narrow gap 75 in the vertical direction is formed between the outer peripheral edge 74 of the valve body 71 and the valve seat 73. When the valve body 71 is fully opened, the valve body 71 is positioned below the illustrated position, and the gap 75 is enlarged.

  The valve body 71 is provided with a valve body hole 76 such as the valve body hole 60 described above. The valve body hole 76 is directed toward the lambda sensor 8. In the illustrated example, one valve body hole 76 inclined with respect to the axial direction of the valve shaft 72 is provided, but the number, arrangement, etc. thereof are arbitrary.

  As in the basic embodiment, the flow F1 of the exhaust gas that has passed through the gap 75 flows along the exhaust pipe inner peripheral surface 63 for a while, but eventually peels off from the exhaust pipe inner peripheral surface 63 and backflows F3 toward the lambda sensor 8. Give rise to There is a possibility that a part L1 of the fuel spray injected from the exhaust pipe injector 9 rides on the reverse flow F3 and moves toward the lambda sensor 8 and adheres to the detection element 36. However, also in this modification, the backflow F3 is suppressed by the exhaust gas flow F5 that has passed through the valve body hole 76, and a part L1 of the fuel spray rides on the backflow F3 and adheres to the lambda sensor 8, particularly the detection element 36. Can be suppressed. Therefore, damage to the lambda sensor 8 can be effectively suppressed.

  In this modification, the valve body 71 is disposed downstream of the bent portion of the exhaust pipe 5 bent at a substantially right angle. However, as described above, the shape of the exhaust pipe 5, the installation position of the valve body 71, etc. are arbitrary. It is.

  Next, a second modification will be described with reference to FIG. In this modification, the valve body 81 of the exhaust brake valve 7 is a swing type valve body. That is, the valve shaft 82 is fixed to the end of the circular plate-shaped valve body 81, and the valve shaft 82 is rotatably supported by the exhaust pipe 5. The valve body 81 is opened and closed by the valve shaft 82 being rotated as indicated by the arrow by the actuator (not shown). FIG. 7 shows the valve body 81 when fully closed. At this time, a relatively narrow radial gap 85 is formed between the exhaust pipe 5 and the substantially entire circumference of the outer peripheral edge 84 of the valve body 81. .

  The valve body 81 is provided with a valve body hole 86 such as the valve body hole 60 described above. The valve body hole 86 is directed toward the lambda sensor 8. In the illustrated example, one valve element hole 86 is provided, but the number thereof is arbitrary, and for example, three may be provided as in the basic embodiment.

  As in the basic embodiment, the flow F1 of the exhaust gas that has passed through the gap 85 flows along the exhaust pipe inner peripheral surface 63 for a while, but eventually peels off from the exhaust pipe inner peripheral surface 63 and backflows F3 toward the lambda sensor 8. Give rise to There is a possibility that a part L1 of the fuel spray injected from the exhaust pipe injector 9 rides on the reverse flow F3 and moves toward the lambda sensor 8 and adheres to the detection element 36. However, also in this modified example, the backflow F3 is suppressed by the exhaust gas flow F5 that has passed through the valve body hole 86, and a part L1 of the fuel spray rides on the backflow F3 and adheres to the lambda sensor 8, particularly the detection element 36. Can be suppressed. Therefore, damage to the lambda sensor 8 can be effectively suppressed.

  In this modification, the exhaust pipe 5 is a straight tube, but as described above, the shape of the exhaust pipe 5 is arbitrary.

  Next, a third modification will be described with reference to FIG. In this modification, the valve body 91 of the exhaust brake valve 7 is a shutter-type valve body. That is, the valve body 91 is opened and closed by the plate-shaped valve body 91 being reciprocated in the direction perpendicular to the exhaust pipe 5 as indicated by the arrow by the actuator (not shown). FIG. 8 shows the valve body 91 when fully closed. At this time, a relatively narrow radial gap 95 is provided between the lower end edge portion 94 which is a part of the outer peripheral edge portion of the valve body 91 and the exhaust pipe 5. Is formed.

  The valve body 91 is provided with a valve body hole 96 such as the valve body hole 60 described above. The valve body hole 96 is directed toward the lambda sensor 8. In the illustrated example, one valve element hole 96 is provided, but the number thereof is arbitrary, and for example, three may be provided as in the basic embodiment.

  Similar to the basic embodiment, the flow F1 of the exhaust gas that has passed through the gap 95 flows along the exhaust pipe inner peripheral surface 63 for a while, but eventually peels off from the exhaust pipe inner peripheral surface 63 and backflows F3 toward the lambda sensor 8. Give rise to There is a possibility that a part L1 of the fuel spray injected from the exhaust pipe injector 9 rides on the reverse flow F3 and moves toward the lambda sensor 8 and adheres to the detection element 36. However, also in this modified example, the backflow F3 is suppressed by the exhaust gas flow F5 that has passed through the valve body hole 96, and a part of the fuel spray L1 rides on the backflow F3 and adheres to the lambda sensor 8, particularly the detection element 36. Can be suppressed. Therefore, damage to the lambda sensor 8 can be effectively suppressed.

  In addition, although the exhaust pipe 5 is a straight pipe also in this modification, the shape of the exhaust pipe 5 is arbitrary.

  Next, a fourth modification will be described with reference to FIG. In this modification, the valve body 101 of the exhaust brake valve 7 is a butterfly valve body similar to the basic embodiment. That is, the valve shaft 102 extending in the diameter direction (the thickness direction in the drawing) is fixed to the central portion of the circular plate-like valve body 101, and the valve shaft 102 is rotatably supported by the exhaust pipe 5. The valve body 101 is opened / closed by rotating the valve shaft 102 as shown by the arrow by the actuator (not shown).

  FIG. 9 shows the valve body 101 when fully closed. At this time, almost the entire circumference of the outer peripheral edge portion 104 of the valve body 101 is brought into close contact with the valve stoppers 107 and 108 fixed to the exhaust pipe inner peripheral surface 63, so that the gap between the valve body outer peripheral edge portion 104 and the exhaust pipe inner peripheral surface 63 is maintained. The gap is almost closed. The valve body 101 is provided with a valve body hole 106 directed toward the lambda sensor 8.

  In this modification, the exhaust gas is allowed to pass through the valve body 101 only through the valve body hole 96 when the valve body 101 is fully closed. Thereby, there is a possibility that the upstream pressure can be easily adjusted when the valve body 7A is fully closed. The flow of the exhaust gas that has passed through the valve body hole 96 is indicated by F5.

  However, for structural reasons, the valve stopper is divided into an upper valve stopper 107 and a lower valve stopper 108 each having a substantially semicircular arc shape. When the valve body 101 is fully closed, the upstream surface, that is, the rear surface of the valve body outer peripheral edge portion 104 is in close contact with the upper valve stopper 107, and the downstream surface, that is, the front surface of the valve body outer peripheral edge portion 104 is in close contact with the lower valve stopper 108. . Therefore, in the outer periphery 104 of the valve body, the seal between the exhaust pipe inner peripheral surface 63 is unsatisfactory in the vicinity of the left and right side portions in the thickness direction of the drawing in the drawing, that is, in the vicinity of the valve shaft 102. A slight gap (not shown) is formed between the peripheral surface 63 and the peripheral surface 63. When the rotatable valve body 101 is provided in the exhaust pipe 5, it is difficult to completely eliminate the gap with the exhaust pipe inner peripheral surface 63 on the entire circumference of the valve body outer peripheral edge 104.

  Accordingly, also in the present modification, the exhaust gas flow F1 passing through the slight gap can be generated. The flow F1 flows along the exhaust pipe inner peripheral surface 63 for a while, as described above, but eventually peels from the exhaust pipe inner peripheral surface 63 and generates a backflow F3 toward the lambda sensor 8. There is a possibility that a part L1 of the fuel spray injected from the exhaust pipe injector 9 rides on the reverse flow F3 and moves toward the lambda sensor 8 and adheres to the detection element 36. However, also in this modification, the backflow F3 is suppressed by the exhaust gas flow F5 that has passed through the valve body hole 106, and a part L1 of the fuel spray rides on the backflow F3 and adheres to the lambda sensor 8, particularly the detection element 36. Can be suppressed. Therefore, damage to the lambda sensor 8 can be effectively suppressed.

  As mentioned above, although embodiment of this invention was described in detail, various embodiment of this invention can be considered.

  (1) For example, the sensor may be a sensor other than the lambda sensor 8, and may be any of a NOx sensor, a PM sensor, and a pressure sensor, for example. Any sensor that can be damaged by liquid adhesion can be a sensor. As is well known, the NOx sensor is a sensor for detecting the NOx concentration of the exhaust gas, and the PM sensor is a sensor for detecting the PM concentration of the exhaust gas.

  (2) The injector may inject liquid other than fuel, for example, may inject urea water used as an ammonia source to the SCR.

  (3) The exhaust throttle valve is not limited to the exhaust brake valve 7 described above, and may be, for example, another valve that does not have an exhaust brake function but has only an exhaust temperature raising function. The actuator for operating the exhaust throttle valve may be electric or hydraulic.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Exhaust pipe 6 Exhaust passage 7 Exhaust brake valve 7A, 71, 81, 91, 101 Valve body 8 Lambda sensor 9 Exhaust pipe injector 10 Oxidation catalyst 11 Particulate filter 36 Detection element 60, 76, 86, 96, 106 Valve body holes 61, 74, 84, 94, 104 Outer peripheral edge 62, 75, 85, 95, 105 Clearance 100 Electronic control unit L Fuel

Claims (7)

An exhaust pipe defining an exhaust passage;
An exhaust throttle valve provided in the exhaust pipe;
A sensor provided downstream of the exhaust throttle valve in the exhaust pipe;
An injector that is provided downstream of the sensor in the exhaust pipe and injects liquid into the exhaust passage;
With
The exhaust throttle valve has a valve body disposed in the exhaust passage, and the valve body has a valve body hole directed to the sensor or the vicinity thereof when fully closed. Exhaust system. When the valve body is fully closed, a gap is formed between at least a part of the outer peripheral edge of the valve body and the exhaust pipe,
The exhaust gas that is generated due to the exhaust gas that has passed through the gap and that flows toward the sensor is suppressed by the flow of the exhaust gas that has passed through the valve body hole. The internal combustion engine exhaust system. The sensor has a detection element exposed in the exhaust passage;
The exhaust system for an internal combustion engine according to claim 1 or 2, wherein the valve body hole is directed to the detection element or the vicinity thereof when the valve body is fully closed. The exhaust system for an internal combustion engine according to any one of claims 1 to 3, wherein the sensor is any one of a lambda sensor, a NOx sensor, a PM sensor, and a pressure sensor. The exhaust system for an internal combustion engine according to any one of claims 1 to 4, wherein the valve body is any one of a butterfly valve body, a poppet valve body, a swing valve body, and a shutter valve body. . The exhaust system for an internal combustion engine according to any one of claims 1 to 5, wherein the liquid is fuel. An oxidation catalyst provided downstream of the injector in the exhaust pipe;
A particulate filter provided downstream of the oxidation catalyst in the exhaust pipe;
And a control unit for controlling the valve body of the exhaust throttle valve to be fully closed and injecting the fuel as the liquid from the injector during idle regeneration of the particulate filter. The exhaust system for an internal combustion engine according to any one of 1 to 6.

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