JP2002285879A - Exhaust gas recirculation system for turbocharged engines - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent deterioration of durability on the compressor side of a supercharger and prevent clogging of an intercooler during EGR operation. When EGR operation is stopped, the PM on the tail pipe side
Measure reduction. An exhaust pipe (9) and an intake pipe (10) are connected to an exhaust gas recirculation path (1).
1 is an exhaust gas recirculation device for an engine with a supercharger that communicates with the engine 1 and recirculates a part of the exhaust gas discharged from the engine 1 to the intake pipe 10. A filter with a catalyst 12 and an exhaust gas recirculation valve 14 are provided in this order in the exhaust gas recirculation path 11, a bypass pipe 15 is branched from the exhaust gas recirculation path 11 downstream of the filter with a catalyst 12, and a switching valve 16 is connected to the bypass pipe. The exhaust gas recirculation valve 1 is provided with the bypass pipe 15 connected to the exhaust path 9.
When the valve 4 is open, the switching valve 16 is closed, and when the reflux valve 14 is closed, the switching valve 16 is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recirculating a part of exhaust gas discharged from a diesel engine to an intake side to reduce N
The present invention relates to an exhaust gas recirculation device for a supercharged engine that measures Ox (hereinafter referred to as EGR).

[0002]

2. Description of the Related Art In a conventional EGR, as shown in FIG. 3, a part of exhaust gas a discharged from a diesel engine 1 is taken out from a position in front of a turbine 3 of a supercharger 2 and introduced into an inlet manifold 7. However, the differential pressure between the exhaust side and the intake side of the diesel engine 1 cannot be sufficiently obtained due to the improvement in the efficiency of the turbocharger 2, or the pressure on the intake side becomes higher than the exhaust side of the diesel engine 1 depending on conditions. This made it difficult to secure EGR.

[0003] As a method of improving this, it is conceivable and practiced to provide a reed valve 42 in an exhaust gas recirculation path 41 that connects the exhaust manifold 4 and the inlet manifold 7 of the diesel engine 1. It has been difficult to perform a large amount of EGR under a wide range of operating conditions. Further, by performing the EGR from the upstream of the turbine 3, the work amount of the supercharger 2 is reduced. In particular, when the supercharger is of a two-stage high / low pressure type, the pressure in front of the turbine of the supercharger on the high pressure side decreases, so that the two-stage supercharger cannot be used effectively.

In the drawing, 5 is a compressor of a supercharger, 43 is an EGR cooler, 44 is an EGR valve, 45
Indicates an intercooler, and a 'indicates intake air.

[0005]

Therefore, it is conceivable to take in EGR downstream of the turbine and return it to the upstream of the compressor of the turbocharger. Passing through the compressor and passing through the intercooler adversely affects the durability of the compressor side of the supercharger or causes a problem of clogging of the intercooler.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object thereof is to prevent deterioration of durability of a compressor side of a turbocharger during EGR operation.
In order to prevent clogging of the intercooler and to reduce PM on the tail pipe side when EGR is stopped.

[0007]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows.

(1) An exhaust gas recirculation path is branched from an exhaust pipe connected to the turbine side of the supercharger, and the exhaust gas recirculation path is connected to an intake pipe connected to the compressor side of the supercharger. In an exhaust gas recirculation device for a supercharged engine that recirculates a part of exhaust gas discharged from an engine to the intake pipe, a particulate filter and an exhaust gas recirculation valve are provided in this order in the exhaust gas recirculation passage, and a downstream of the particulate filter is provided. A bypass pipe is branched from the exhaust gas recirculation path on the side, a switching valve is provided on the bypass pipe or the exhaust gas recirculation path, and the bypass pipe is connected to the exhaust path, and a switching valve is provided when the exhaust gas recirculation valve is open. To the exhaust gas recirculation path, and to switch the switching valve to the exhaust path when the recirculation valve is closed. Exhaust gas recirculation system for turbocharged engines.

(2) The supercharger comprises two types of superchargers, a high-pressure supercharger and a low-pressure supercharger, and the exhaust gas recirculation path is connected to the turbine side of the low-pressure supercharger. Exhaust path,
The exhaust gas recirculation device for an engine with a supercharger according to (1), wherein the exhaust gas recirculation device is connected between intake passages connected to a compressor of the low-pressure supercharger.

(3) The exhaust gas recirculation system for a supercharged engine according to (1) or (2), wherein the bypass pipe is connected to a downstream side of a filter with a catalyst provided in the exhaust passage.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

In FIG. 1, reference numeral 1a denotes a diesel engine with a supercharger. The inlet side of the turbine 3 of the supercharger 2 is connected to an exhaust manifold 4, and the supercharger 2
The outlet side of the compressor 5 is connected to an inlet manifold 7 via a communication pipe 6. The communication pipe 6 is provided with an intercooler 8.

An exhaust pipe 9 is connected to an outlet side of the turbine 3, and an exhaust pipe 9 is connected to an inlet side of the compressor 5.
An intake pipe 10 is connected. And the turbine 3
Immediately after the outlet of the exhaust pipe 9, the exhaust pipe 9
1 is branched, and its end is connected to the intake pipe 10. The exhaust gas recirculation pipe 11 is provided with a particulate filter 12 with a catalyst, a cooler 13 for recirculating gas cooling, and an exhaust gas recirculation valve 14 in this order.

Further, on the downstream side of the particulate filter with catalyst 12, a bypass pipe 15 branches off from the exhaust gas recirculation pipe 11, and the end thereof is connected to the exhaust pipe 9. The switching valve 16 is connected to the bypass pipe 15.
Is provided.

Further, the exhaust pipe 9 has a bypass pipe 15
The main particulate filter 17 and a post-processing device 18 such as a silencer,
Are provided, and an air cleaner 19 is provided in the intake pipe 10. Further, the intake pipe 10 is provided with an intake throttle valve 20 located between the air cleaner 19 and the outlet of the exhaust gas recirculation pipe 11.

In the figure, reference numeral 21 denotes a control device for controlling the valve. When the exhaust gas recirculation valve 14 is opened by a command from the control device 21, the switching valve 16 is closed, and on the contrary, the recirculation valve 14 is closed. Then, the switching valve 16 is opened. Further, the control device 21 controls the degree of throttle of the intake throttle valve 20 to control the amount of EGR.

When the exhaust gas recirculation valve 14 is opened and the switching valve 16 is closed by a command from the control device 21, a part of the exhaust gas a discharged from the diesel engine 1a with a supercharger is introduced into the exhaust gas recirculation pipe 11. Soot and SOF (Soluble Organic Fraction) contained in exhaust gas
Such particulate matter (hereinafter, referred to as PM) is collected by the particulate filter 12 with a catalyst. The particulate filter 12 with a catalyst is periodically or
It is reproduced depending on how it is collected.

The exhaust gas a ″ from which the PM has been removed is appropriately cooled by the reflux gas cooling cooler 13 and then returned to the intake pipe 10. Accordingly, the durability of the compressor 5 in the supercharger 2 is adversely affected. Not only is not applied, but also is effective in preventing clogging of the intercooler 8. In the drawing, a 'indicates intake air.

On the other hand, when the exhaust gas recirculation valve 14 is closed and the switching valve 16 is opened in response to a command from the control device 21, a part of the exhaust gas a discharged from the turbocharged diesel engine 1a is partially recirculated. The PM contained in the exhaust gas is introduced into the pipe 11, and the PM contained in the exhaust gas is collected by the particulate filter 12 with the catalyst. The exhaust gas a ″ from which the PM has been removed is supplied to the bypass pipe 1 branched from the exhaust gas recirculation pipe 11.
5 and is returned to the exhaust pipe 9.

Therefore, the turbocharged diesel engine 1
a part of the PM contained in the exhaust gas a discharged from the main particulate filter 17 is removed by the particulate filter 12 with the catalyst.
It is possible to reduce the size, which is effective in reducing costs.

As described above, when an attempt is made to mount a particulate filter without bypassing a part of the exhaust gas to the exhaust gas recirculation pipe 11, a large-sized particulate filter is required. Although it is extremely difficult to mount, the particulate filter 12 can be reduced in size and good in mountability by passing a part of the exhaust gas as in the present invention. In addition, a large particulate filter is installed at a place distant from the engine, for example, on an underfloor.
When the R is taken out, the EGR pipe becomes longer, causing problems such as the response, the complexity of the pipe, and the difficulty in obtaining the differential pressure. However, according to the present invention, such a problem is solved.

The main particulate filter 1
When the switching regeneration type 7 is used, the outlet of the bypass pipe 15 is connected to the exhaust pipe 9 between the main particulate filter 17 and the post-processing device 18 as shown by a two-dot chain line,
When the EGR is not performed, it is possible to control so that the main particulate filter 17 is regenerated.

FIG. 2 is a schematic diagram showing a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

This supercharged diesel engine 1b
The turbocharger-equipped diesel engine 1a described above is different from the diesel engine with supercharger 1a only in the supercharger, and the other parts are almost the same.

That is, the diesel engine 1b with a supercharger has the two-stage supercharger of the high-pressure supercharger 30 and the low-pressure supercharger 40. It is different only from the diesel engine 1a.

That is, the exhaust sides of the high and low turbochargers 30, 40 are connected to the outlet side of the high pressure stage turbine 3a and the low pressure stage turbine 3b.
Of the high pressure stage turbine 3a is connected to the exhaust manifold 4 by the communication pipe 31.
, And the outlet side of the low-pressure stage turbine 3 b is connected to the exhaust pipe 9. In addition, the communication pipe 31 communicates with the inlet side of the high-pressure stage turbine 3 a through a bypass pipe 32.

On the other hand, the intake sides of the high and low superchargers 30, 40 communicate with the inlet side of the high-pressure stage compressor 5a and the outlet side of the low-pressure stage compressor 5b through a communication pipe 33.
Further, the outlet side of the high-pressure stage compressor 5 a is connected to the inlet manifold 7 via the communication pipe 6, and the inlet side of the low-pressure stage compressor 5 b is connected to the intake pipe 10.
In addition, an intercooler 34 is provided in each of the communication pipes 6 and 33.

In the case of this example, in addition to the effects described in the first embodiment, there is an advantage that the two-stage supercharger can be effectively used.

In the above description, the case where the bypass pipe 15 is provided between the exhaust gas recirculation pipe 11 and the exhaust pipe 9 and the switching valve 16 is provided in the bypass pipe 15 has been described. Or you may provide in a branch part.

Further, when the particulates at the outlet of the tail pipe are to be reduced, the level can be reduced by mounting the main particulate filter 17 on the downstream side.

[0031]

As described above, according to the present invention, EGR
During operation, the exhaust gas from which PM has been removed by the particulate filter with catalyst provided in the exhaust gas recirculation path is returned to the intake pipe, so that not only does it not adversely affect the durability of the compressor in the supercharger, but also the intercooler This is very effective in preventing clogging.

Further, according to the present invention, when the EGR operation is stopped, the exhaust gas from which PM has been removed by the particulate filter with a catalyst is returned to the exhaust pipe through a bypass pipe branched from the exhaust gas recirculation pipe. In addition, the size of the main particulate filter can be reduced, which is effective in reducing costs.

When a particulate filter is to be mounted without bypassing a part of the exhaust gas to the exhaust gas recirculation pipe, a large-sized particulate filter is required. Although it is difficult, as in the present invention, by allowing a part of the exhaust gas to pass through, the particulate filter can be reduced in size and has good mountability.

When a large particulate filter is installed at a place distant from the engine, for example, on an underfloor, and the EGR is taken out from the downstream, the EGR pipe becomes long, and the response, the complexity of the pipe, and the differential pressure are reduced. Although problems such as difficulty in taking out occur, such problems are solved according to the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of an exhaust gas recirculation device for a supercharged engine according to the present invention.

FIG. 2 is a schematic view showing a second embodiment of the exhaust gas recirculation device for a supercharged engine according to the present invention.

FIG. 3 is a schematic view of a conventional exhaust gas recirculation device for a supercharged engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 3 Turbocharger turbine 5 Supercharger compressor 9 Exhaust pipe 10 Intake path 11 Exhaust gas recirculation path 12 Filter with catalyst 14 Exhaust gas recirculation valve 15 Bypass pipe 16 Switching valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02B 37/00 302 F02M 25/07 580D F02M 25/07 570 580A 580 F02B 37/00 301B 301F 301G F term ( Reference) 3G005 DA02 EA16 EA23 EA25 FA27 GA02 GB15 GB26 GD11 HA12 HA13 HA18 JA23 JA28 3G062 AA01 AA05 ED00 ED01 ED03 ED08 ED09 ED10 ED11 3G090 AA03 AA04 CB25 EA05 EA06 3G092 AA02 EA10 AA18 EA00

Claims (3)

[Claims] An exhaust gas recirculation path is branched from an exhaust pipe connected to a turbine side of a supercharger, and the exhaust gas recirculation path is connected to an intake pipe connected to a compressor side of the supercharger. In the exhaust gas recirculation system for a supercharged engine that recirculates a part of the exhaust gas discharged from the exhaust pipe to the intake pipe, a particulate filter and an exhaust gas recirculation valve are provided in this order in the exhaust gas recirculation path, and a downstream side of the particulate filter is provided. In the above, a bypass pipe is branched from the exhaust gas recirculation path, a switching valve is provided on the bypass pipe or the exhaust gas recirculation path, and the bypass pipe is connected to the exhaust path, and when the exhaust gas recirculation valve is open, the switching valve is opened. On the exhaust gas recirculation path side, a switching valve is switched to the exhaust path side when the recirculation valve is closed. Exhaust gas recirculation system for turbocharged engines. 2. An exhaust system wherein the supercharger comprises two types of superchargers, a high-pressure supercharger and a low-pressure supercharger, and the exhaust gas recirculation path is connected to a turbine side of the low-pressure supercharger. The exhaust gas recirculation device for an engine with a turbocharger according to claim 1, wherein the exhaust gas recirculation device is connected between a passage and an intake passage connected to a compressor side of the low-pressure supercharger. 3. The exhaust gas recirculation system for a turbocharged engine according to claim 1, wherein the bypass pipe is connected to a downstream side of a catalyst-equipped filter provided in the exhaust passage.