JP2019082181A - Exhaust device of engine - Google Patents

Abstract

To efficiently activate a monolithic catalyst 12 with limited heat quantity exhaust gas has.SOLUTION: A monolithic catalyst 12 is stored in a case 11 in a state of making its axial core substantially horizontal. The case 11 is provided with an inflow port 13 facing an upstream side end surface of the monolithic catalyst 12 and making exhaust gas substantially horizontally flow into the monolithic catalyst 12, and an outflow port 14 making exhaust gas flow out from a downstream side of the monolithic catalyst 12. Each center of the inflow port 13 and the outflow port 14 is offset below with respect to the axial core of the monolithic catalyst 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an exhaust system of an engine.

  An exhaust system of an automobile engine is provided with a catalytic converter for purifying exhaust gas. In Patent Document 1, a monolith catalyst is disposed substantially horizontally, and exhaust gas is introduced from above obliquely to the monolith catalyst by a C-shaped curved connecting conduit, and the exhaust gas is caused to flow obliquely downward from the monolith catalyst. It is described. It is intended to make the flow of exhaust gas flowing into the monolith catalyst uniform and prevent the exhaust gas from being concentrated on a part of the monolith catalyst.

Patent 4326145

  By the way, recently, with the improvement of the thermal efficiency of the engine, the energy to be discarded to the exhaust gas decreases, and the temperature of the exhaust gas tends to decrease accordingly. Therefore, it becomes important how efficiently the catalyst is activated by the limited amount of heat obtained from the exhaust gas.

  Even after the temperature at which the catalyst exhibits activity, the exhaust gas temperature becomes low when the operating condition of the engine shifts to low load operation or when fuel is cut. As a result, the catalyst is cooled by the low temperature exhaust gas and its activity is reduced. Thereafter, when the engine operating condition shifts to a medium load operation or a high load operation, the exhaust gas temperature becomes high, and as a result, the catalyst is heated and becomes active again.

  The decrease in the catalyst activity is temporary caused by a change in engine operating conditions, but in the meantime, the purification rate of the exhaust gas decreases. Therefore, the longer the time required for catalyst reactivation, the worse the emission performance of the vehicle.

  The above is true for both gasoline engines and diesel engines, but is particularly problematic for diesel engines that are inherently low in exhaust gas temperature.

  Then, this invention makes it a subject to activate a catalyst efficiently by the limited amount of heat which exhaust gas has.

  In order to solve the above problems, the present invention offsets the centers of the exhaust gas inlet and outlet of the catalytic converter with respect to the axis of the monolith catalyst.

The exhaust system of the engine presented here comprises a catalytic converter for exhaust gas purification,
And a particulate matter processing device having a filter for collecting particulate matter in exhaust gas flowing out of the catalytic converter,
The catalytic converter is disposed along the side of the engine body,
The particulate matter processing device is disposed below the catalytic converter and along the catalytic converter and the engine body,
In the above-mentioned catalytic converter, the case contains a monolithic catalyst for exhaust gas purification, the axis of which is horizontal.
The case includes a cone-shaped upstream cover covering the upstream end face of the monolith catalyst, and a downstream cover covering the downstream end face of the monolith catalyst,
The upstream cover is provided with an inlet portion which is laterally opposed to the end face on the upstream side of the monolith catalyst and allows the exhaust gas to flow laterally toward the monolith catalyst,
The downstream cover is provided with an outlet portion through which the exhaust gas flows out from the downstream side of the monolith catalyst,
The inlet and the outlet are formed such that their respective bores are smaller than the diameter of the monolith catalyst,
The center of the inlet and the center of the outlet are offset with respect to the axis of the monolith catalyst,
In a side view of the engine body, the offset amount of the center of the outlet portion with respect to the axis of the monolith catalyst is smaller than the offset amount of the center of the inlet portion with respect to the axis of the monolith catalyst. .

  In this exhaust system, since the inlet of the catalytic converter and the upstream end face of the monolith catalyst are laterally opposed to each other and the center of the inlet is offset with respect to the axis of the monolith catalyst, exhaust The mainstream portion where the gas flow is fast mainly passes through the portion of the monolith catalyst which is offset from near the axial center. The exhaust gas having passed through the monolith catalyst flows out of an outlet portion smaller than the offset amount of the catalytic converter with respect to the axis of the monolith catalyst and flows to the particulate matter processing device.

  Also, since the catalytic converter is disposed along the side of the engine body and the particulate matter processing device is disposed below the catalytic converter and along the catalytic converter and the engine body, the catalytic converter and The particulate matter processing device can be compactly arranged on the side of the engine body in a compact manner, and the three of the engine body, the catalytic converter and the particulate matter processing device interfere with each other to dissipate heat, thereby reducing the heat loss Be advantageous to

  In a preferred aspect of the present invention, the offset amount of the center of the inlet to the axis of the monolith catalyst is not less than 1/4 and not more than 1/2 of the radius of the monolith catalyst.

In a preferred aspect of the present invention, the particulate matter processing device comprises a case in which a monolithic filter for trapping particulate matter in exhaust gas is accommodated in a case, and the axis is horizontal.
The outlet port portion of the catalytic converter and the inlet portion in which the exhaust gas flows in the case of the particulate matter processing device are connected by a curved connecting pipe,
In a side view of the engine body, the outlet of the catalytic converter is closer to the inlet of the catalytic converter than a position corresponding vertically to the inlet of the particulate matter processing device. It is located at a close position,
The downstream end of the connection pipe is the flow of the particulate matter processing device so that the exhaust gas flowing out of the outflow portion of the catalytic converter flows obliquely from the upper side into the inflow portion of the particulate matter processing device It is connected to the entrance.

  As described above, according to the present invention, the center of the inlet and the center of the outlet of the catalytic converter are offset with respect to the axis of the monolithic catalyst, and the center of the outlet in a side view of the engine body Since the offset amount of the monolith catalyst to the axis of the catalyst is smaller than the offset amount of the center of the inlet to the axis of the monolith catalyst, the limited amount of heat possessed by the exhaust gas is effective for raising the temperature of the catalyst and maintaining the temperature. It can be used to

It is a perspective view showing an exhaust system of an engine. It is a side view which shows the exhaust device in part longitudinal cross section. It is a front view showing a catalytic converter of the exhaust system. It is an exploded perspective view showing a particulate matter processing device, an EGR cooler, and an EGR valve. It is a schematic longitudinal cross-sectional view which shows the other example of a catalytic converter.

  Hereinafter, an embodiment for carrying out the present invention will be described based on the drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its applications or its uses.

  In FIG. 1, reference numeral 1 denotes an engine body of a diesel engine provided in an engine room of a car. In the present embodiment, the crankshaft 1 of the engine body 1 is disposed horizontally extending in the vehicle width direction, and the exhaust turbocharger 2, catalytic converter 3 and particulate matter processing device 4 are mounted on the side (in this case, the back) of the engine 1 The EGR cooler 5 and the EGR valve 6 are disposed.

  The catalytic converter 3 in this example is an oxidation catalyst that oxidizes and purifies HC and CO in the exhaust gas. The particulate matter processing device 4 is a so-called DPF (diesel particulate filter) that collects and burns and removes particulate matter in exhaust gas. The EGR cooler 5 cools the exhaust gas returned to the intake system. The EGR valve 6 regulates the amount of EGR (exhaust gas recirculation) to the intake system.

  The turbocharger 2 and the catalytic converter 3 have their respective axes substantially horizontal, that is, the axes are horizontal, and along the upper side of the engine body 1 in the longitudinal direction of the engine body 1 (in the vehicle width direction) It is arranged in a row. The particulate matter processing device 4 is disposed such that the axial center is substantially horizontal along the lower surface of the catalytic converter 3 and the side surface of the engine body 1 on the lower side of the catalytic converter 3. The catalytic converter 3 is connected to the particulate matter processing device 4 by a curved connecting pipe 7.

  According to such a layout of the catalytic converter 3 and the particulate matter processing device 4, the catalytic converter 3 and the particulate matter processing device 4 can be compactly arranged on the side surface of the engine main body 1. In addition, the three members of the engine body 1, the catalytic converter 3 and the particulate matter processing device 4 are in a relation of preventing heat radiation from each other, which is advantageous for reducing the heat loss.

  An exhaust pipe 9 extending to the rear of the vehicle is connected to the particulate matter processing device 4 via a flexible tube 8 disposed under the floor of the passenger compartment. Although not shown, the exhaust pipe 9 continues to the tail pipe via an exhaust silencer. In FIG. 1, 26 is a temperature sensor for detecting the inlet gas temperature of the particulate matter processing device 4, and 27 is a pressure extraction portion of a pressure sensor (not shown) for detecting the gas pressure on the inlet side of the particulate matter processing device 4. It is.

  As shown in FIG. 2, the catalytic converter 3 is housed in the case 11 with the monolith catalyst 12 substantially horizontal. The case 11 includes a case body 11a for housing the monolith catalyst 12, a cone-shaped upstream cover 11b covering the upstream end face of the monolith catalyst 12, and a cone-shaped downstream cover covering the downstream end face of the monolith catalyst 12. And 11c. In the upstream side cover 11b, in the side view of the engine main body 1, the inlet portion 13 which allows the exhaust gas to flow substantially horizontally (laterally) toward the monolith catalyst 12 while facing the end face on the upstream side of the monolith catalyst 12 Is provided. In the downstream cover 11c, the monolith catalyst 12 is opposed to the inflow port 13 with the monolith catalyst 12 (opposite to the end face on the downstream side of the monolith catalyst 12), and the exhaust gas is approximately horizontal from the downstream side of the monolith catalyst 12 ( A lateral outlet 14 is provided for the outflow.

  The exhaust gas outlet 16 of the turbine housing 15 of the exhaust turbocharger 2 is directly connected to the inlet 13 of the case 11. The upstream end of the connecting pipe 7 is connected to the outlet port 14 of the case 11. Further, a temperature sensor 17 for detecting an inlet gas temperature of the catalytic converter 3 is attached to the upper half of the cone wall extending from the inlet 13 of the upstream cover 11b to the case body 11a.

  The diameter of each of the inlet 13 and the outlet 14 of the case 11 is smaller than the diameter of the monolithic catalyst 12, and the center Ci of the inlet 13 and the center Co of the outlet 14 are the axial centers of the monolithic catalyst 12. Offset downward to Cc. The offset amount D1 with respect to the axial center Cc of the monolith catalyst 12 at the center Ci of the inlet portion 13 and the offset amount D2 with respect to the axial center Cc of the monolith catalyst 12 at the center Co of the outlet portion 14 are both of the radius of the monolith catalyst 12 It is preferable that it is 1/4 or more and 1/2 or less. As shown in FIG. 2, the center Co of the outlet 14 is offset from the center Ci of the inlet 13, and the offset D 2 of the outlet 14 is set smaller than the offset D 1 of the inlet 13. It is done.

  As shown in FIG. 3, the inlet portion 13 and the outlet portion 14 are arranged such that at least 2/3 of the opening area of each of them is opposed to the lower half circumference end face of each of the upstream side and the downstream side of the monolith catalyst 12 Is preferred. Furthermore, it is preferable that the offset amounts D1 and D2 be 1/2 or less, and 2/3 or more of the opening area of each of the inlet 13 and the outlet 14 be below the upstream side and the downstream side of the monolith catalyst 12, respectively. It is to face the end face on the half circumference side.

  In the example of FIG. 3, most of the opening area of the inlet 13 faces the end surface of the lower half of the upstream side of the monolith catalyst 12, and at least 5/6 of the opening area of the outlet 14 is downstream of the monolith catalyst 12. It faces the end face of the lower half side of the side.

  As shown in FIG. 2, the particulate matter processing device 4 is configured such that a case 18 accommodates a monolith filter 19 that collects particulate matter in exhaust gas. The filter 19 is coated with a catalyst for burning and removing particulate matter deposited on the filter 19. The case 18 includes a case main body 18 a for housing the filter 19, an upstream cover 18 b covering the upstream end surface of the filter 19, and a downstream cover 18 c covering the downstream end surface of the filter 19. The exhaust gas inlet of the particulate matter processing device 4 is disposed in the vicinity of the outlet 14 of the catalytic converter 3, and the downstream end of the connecting pipe 7 is connected to the upstream cover 18b. An outlet portion of exhaust gas of the particulate matter processing device 4 is disposed in the vicinity of the inlet portion 13 of the catalytic converter 3. Here, in the side view of the engine body 1, the outlet 14 of the catalytic converter 3 is closer to the inlet 13 of the catalytic converter 3 than the position corresponding to the upper and lower sides with respect to the inlet of the particulate matter processing device 4. The downstream end of the connecting pipe 7 is provided so that the exhaust gas flowing out from the outlet portion 14 of the catalytic converter 3 flows obliquely from the upper side into the inlet portion of the particulate matter processing device 4. It is connected to the inflow port of the particulate matter processing device 4.

  As shown in FIG. 4, the downstream side cover 18 c of the particulate matter processing device 4 is flat and protrudes rearward of the particulate matter processing device 4, and exhaust gas is applied to the tail pipe at the tip thereof. An exhaust gas outlet 21 shown in FIG. Then, the exhaust gas is guided to the EGR cooler 5 at a position offset from the axial center Cf of the filter 19 in the downstream side cover 18c forward (on the opposite side of the exhaust gas outlet 21 across the axial center Cf) as shown in FIG. An exhaust gas outlet 22 for EGR is open.

  The EGR cooler 5 includes a series of connected gas introduction parts 5a for EGR, a cooler main body 5b, and a gas outflow part 5c for EGR. The EGR cooler 5 is water-cooled, and a cooling water supply pipe 23 and a cooling water discharge pipe 24 are connected to the cooler body 5 b. Then, the gas introduction part 5a is connected to the exhaust gas outlet 22 of the downstream cover 18c, and the EGR cooler 5 is disposed with the axial center Cf of the filter 19 along the flat downstream cover 18c. It extends to the opposite side of the gas outlet 22, that is, to the rear.

  An outlet 25 for the EGR gas opens laterally (opposite the particulate matter processing device 4) to a gas outlet 5c at the rear end of the EGR cooler 5, and an EGR valve 6 is connected to the outlet 25. It is done.

  As described above, the particulate matter processing device 4, the EGR cooler 5 and the EGR valve 6 are arranged in the longitudinal direction of the engine body 1 along the side surface (rear surface) of the engine body 1.

According to the exhaust system of the engine described above, the exhaust gas flows from the inlet 13 of the case 11 of the catalytic converter 3 substantially horizontally toward the monolithic catalyst 12. The center Ci of the inlet 13 is offset downward with respect to the axial center Cc of the monolith catalyst 12, and the center Co of the outlet 14 is also offset downward with respect to the axial center Cc of the monolith catalyst 12. The mainstream portion where the flow of exhaust gas is fast passes through the portion from the vicinity of the axial center Cc of the monolith catalyst 12 to the lower portion.

  On the other hand, although the amount of exhaust gas flowing in the upper portion of the monolithic catalyst 12 is smaller than that in the lower portion, the amount of exhaust gas discharged from the engine itself is large in medium load / high load operation of the engine. Moreover, since the turbine housing 15 of the exhaust turbocharger 2 is directly connected to the inlet portion 13 of the case 11, when the exhaust turbocharger 2 operates, the exhaust gas becomes a swirling flow due to the rotation of the turbine and the case Flow into 11 Therefore, even if the inlet portion 13 of the case 11 is offset as described above, the exhaust gas can be easily dispersed in the entire monolithic catalyst 12. That is, since a small amount of exhaust gas flows also to the upper part of the monolith catalyst 12, the upper part of the monolith catalyst 12 is also effectively used for purification of the exhaust gas.

  Then, as described above, since the main flow of the exhaust gas passes from near the axial center of the monolith catalyst to the lower side, the lower side of the monolith catalyst 12 is heated by the main flow of the exhaust gas. On the other hand, since the hot air has the property of rising, when the exhaust gas flows into the case 11 from the inlet 13, the hot air flows upward and flows into the monolith catalyst 12, and the hot air also flows from the lower part of the monolith catalyst 12. To rise. As a result, the upper side of the monolith catalyst 12 is also heated by the rise of the hot air. Therefore, the entire monolithic catalyst is efficiently heated to activate the catalyst, and the activity is maintained.

  In short, the main flow of the exhaust gas passes through a portion extending from near the axial center of the monolith catalyst 12 to the lower part, and the upper part of the monolith catalyst 12 is heated by the rise of the hot air, so the limited amount of heat possessed by the exhaust gas is It will be efficiently utilized for temperature rising and temperature maintenance of the monolith catalyst 12 whole.

  When the operating condition of the engine shifts to a low load operation or a fuel cut operation, the temperature of the exhaust gas decreases, but the flow rate of the exhaust gas discharged from the engine also decreases. In addition, at the time of low load operation of the engine where the exhaust turbocharger 2 does not operate or at the time of fuel cut, the exhaust gas flowing into the catalytic converter 3 does not become swirl flow. Therefore, much of the exhaust gas having a low temperature passes through a portion extending from near the axial center of the monolith catalyst 12 to the lower portion, and the amount of exhaust gas passing through the upper side of the monolith catalyst 12 is small.

  Therefore, although the lower side of the monolith catalyst 12 is cooled by the low temperature exhaust gas, it is avoided that the upper side is cooled by the low temperature exhaust gas. Therefore, heat is held in the upper part of the monolith catalyst 12 whose temperature has been raised by the rise of the hot air first, and the temperature decrease is small.

  Therefore, when the engine operating state subsequently shifts to a medium load operation or a high load operation and the high temperature exhaust gas flows into the monolith catalyst 12, the amount of heat taken up by the upper part of the monolith catalyst 12 is small. The temperature on the side rises rapidly, and the entire monolith catalyst 12 tends to exhibit activity. Therefore, the deterioration of the emission performance can be avoided.

  Further, as described above, by offsetting the center Ci of the inflow portion 13 of the case 11 downward with respect to the axial center Cc of the monolith catalyst 12, the upstream cover 11b of the case 11 is compared with the lower half circumference side thereof. The distance from the inlet 13 to the case body 11 a of the cone wall on the upper half circumference side is long. Therefore, the layout of the temperature sensor 17 with respect to the cone wall on the upper half circumference side becomes easy.

  FIG. 5 shows a reference embodiment. In the embodiment shown in FIG. 2, the inlet 13 and the outlet 14 of the catalytic converter 3 are opposed to each other with the monolith catalyst 12 in between, but in FIG. 5, the inlet 13 and the outlet 14 are not opposed. It has become.

  First, the upstream cover 11b of the case 11 has the inlet portion 13 for causing the exhaust gas to flow substantially horizontally toward the monolith catalyst 12 relative to the end face on the upstream side of the monolith catalyst 12, as in the embodiment shown in FIG. Is equipped. The center Ci of the inlet 13 is offset downward with respect to the axial center Cc of the monolith catalyst 12. The offset amount D1 is preferably 1/4 or more and 1/2 or less of the radius of the monolith catalyst 12. An upstream exhaust pipe or a turbine housing of an exhaust turbocharger is coupled to an upstream pipe portion which is curved and rises from the inflow port portion 13.

  On the other hand, the downstream side cover 11 c of the case 11 extends obliquely downward from the case main body 11 a accommodating the monolith catalyst 12, and an outlet portion 14 which allows exhaust gas to flow obliquely downward from the downstream side of the monolith catalyst 12 at its tip. Is open downward. Then, a particulate matter processing device (not shown) is connected to the outflow port portion 14 by the connecting pipe 7.

  Also in the embodiment shown in FIG. 5, since the outlet portion 14 of the case 11 causes the exhaust gas to flow obliquely downward from the downstream side of the monolith catalyst 12, the main flow of the exhaust gas flowing from the inlet portion 13 is the monolith catalyst 12. It passes through the area from near the axis to the lower part.

  Therefore, at the time of medium load and high load operation of the engine, the lower side of the monolith catalyst 12 is heated by the main stream of the exhaust gas and the upper side is heated by the rise of the hot air, so the limited amount of heat retained by the exhaust gas is monolith It will be efficiently used for temperature rising and temperature maintenance of the whole catalyst 12.

  In addition, when the operating state of the engine shifts to a low load operation or a fuel cut operation, the lower side of the monolith catalyst 12 is cooled by the low temperature exhaust gas, but the monolith catalyst whose temperature is high due to the rise of hot air first. On the upper side of 12 heat is stored and the temperature drop is reduced. Therefore, when the high temperature exhaust gas subsequently flows into the monolith catalyst 12, the amount of heat taken up by the upper portion of the monolith catalyst 12 is small, so that the entire monolith catalyst 12 rapidly rises to the activation temperature.

Reference Signs List 1 engine body 2 exhaust turbocharger 3 catalytic converter 4 particulate matter processing device 5 EGR cooler 6 EGR valve 7 connecting pipe 11 case 12 monolith catalyst 13 inlet port 14 outlet port 15 turbine housing 16 exhaust gas outlet port 19 filter

Claims (3)

In an exhaust system of an engine provided with a catalytic converter for exhaust gas purification,
And a particulate matter processing device having a filter for collecting particulate matter in exhaust gas flowing out of the catalytic converter,
The catalytic converter is disposed along the side of the engine body,
The particulate matter processing device is disposed below the catalytic converter and along the catalytic converter and the engine body,
In the above-mentioned catalytic converter, the case contains a monolithic catalyst for exhaust gas purification, the axis of which is horizontal.
The case includes a cone-shaped upstream cover covering the upstream end face of the monolith catalyst, and a downstream cover covering the downstream end face of the monolith catalyst,
The upstream cover is provided with an inlet portion which is laterally opposed to the end face on the upstream side of the monolith catalyst and allows the exhaust gas to flow laterally toward the monolith catalyst,
The downstream cover is provided with an outlet portion through which the exhaust gas flows out from the downstream side of the monolith catalyst,
The inlet and the outlet are formed such that their respective bores are smaller than the diameter of the monolith catalyst,
The center of the inlet and the center of the outlet are offset with respect to the axis of the monolith catalyst,
In a side view of the engine body, the offset amount of the center of the outlet portion with respect to the axis of the monolith catalyst is smaller than the offset amount of the center of the inlet portion with respect to the axis of the monolith catalyst. Engine exhaust system. In claim 1,
An exhaust system of an engine, wherein an offset amount of the center of the inflow port portion with respect to an axis of the monolith catalyst is 1/4 or more and 1/2 or less of a radius of the monolith catalyst. In claim 1 or claim 2,
The above-mentioned particulate matter processing apparatus comprises, in a case, a monolith filter for trapping particulate matter in exhaust gas, and the axis is set to be horizontal,
The outlet port portion of the catalytic converter and the inlet portion in which the exhaust gas flows in the case of the particulate matter processing device are connected by a curved connecting pipe,
In a side view of the engine body, the outlet of the catalytic converter is closer to the inlet of the catalytic converter than a position corresponding vertically to the inlet of the particulate matter processing device. It is located at a close position,
The downstream end of the connection pipe is the flow of the particulate matter processing device so that the exhaust gas flowing out of the outflow portion of the catalytic converter flows obliquely from the upper side into the inflow portion of the particulate matter processing device An exhaust system of an engine connected to an inlet.

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