JPH04148012A - Exhaust gas recirculation device for engine - Google Patents

Abstract

PURPOSE:To prevent a trap filter being clogged as well as to keep a reduction effect of NOx due to exhaust gas recirculation by forming a part of air compressed by a compressor to reversely flow into the trap filter so as to be led to an exhaust passage at the time of reducing speeds where exhaust gas recirculation is suspended. CONSTITUTION:A turbo-charger 4 allows a turbine 6 to be rotated at high speeds through the pressure energy of exhaust gas, and also allows air taken in by a compressor 5 through an air cleaner 7 to be super-charged. Meanwhile, a trap filter 20 is interposed at the halfway of an EGR passage 8 connecting an exhaust passage 3 to an intake air passage 2. In this case, a valve means is made up, which selectively communicates the EGR passage 8 with the upstream side or the down stream side with respect to the compressor 5 of the intake air passage 2 with valves 21 and 22 disposed to an outlet passage 8A and an auxiliary passage 8B respectively. And the valve means 21 and 22 controls compressed air fed by the compressor 5 to reversely flow to the trap filter 20 with the EGR passage 8 communicated to the downstream side of the compressor 5 by means of an electronic control unit 14 under a specified operating condition.

Description

[Detailed description of the invention] (Industrial application field) The present invention is directed to improving an exhaust gas recirculation system for an engine.

(Prior art and its problems) In automobile engines, etc., in order to reduce nitrogen oxides (NOx) in the exhaust gas, a part of the exhaust gas (EG
An exhaust gas recirculation device is used to recirculate R gas) into the gas system.

In the case of a diesel engine with a turbocharger,
In order to prevent particulates (fine particles such as carbon) contained in the exhaust recirculation gas from colliding with the compressor and damaging the blades, a trap filter is installed in the EGR passage to collect the particulates. There was something to protect the compressor.
(See Publication No. 5161, Publication No. 1-149559)
.

(Problem to be solved by the invention) By the way, in the case of a trap filter installed in the middle of an exhaust pipe, it has a self-regeneration function that burns the particulate accumulated in the trap filter under operating conditions where the exhaust gas temperature increases. However, in the case of a trap filter installed in the middle of the EGR passage, the temperature of the wandering soot drops before being guided to the trap filter, making it difficult to burn particulates deposited on the trap filter. As a result, the trap filter could become clogged due to the accumulation of particulates, stopping the flow of exhaust gas.

The present invention aims to solve these conventional problems.

(Means for solving problem α) In order to achieve the above object, the present invention includes a compressor for supercharging intake air in the middle of the intake passage, and communicates the exhaust passage and the intake passage upstream of the compressor with each other. In an exhaust gas recirculation system for an engine that is equipped with an EGR passage that recirculates a part of exhaust gas and a trap filter that collects particulates in the exhaust gas in the middle of the EGR passage,
Valve means for selectively communicating the R passage with an upstream side and a downstream side of the compressor in the intake passage is provided, and the EGR passage is connected to the downstream side of the compressor under predetermined operating conditions in an EGR stop region via the valve means. A control means is provided to cause the compressed air sent from the compressor to flow back into the trap filter.

(Function) Based on the above configuration, in the EGR1lI region, by connecting the downstream side of the trap filter to the upstream steel of the compressor, a part of #sgas is recirculated to the intake system via the valve means, and NOx in the exhaust gas is Reduce. At this time, particulates contained in the exhaust gas recirculation are collected by a trap filter to protect the compressor.

In the EGR stop region, under predetermined operating conditions such as deceleration operation or full load operation, the downstream side of the trap filter in the EGR passage is connected to the downstream side of the compressor in the intake passage through a valve means, and the compressor supercharges the air. By introducing the compressed air into the exhaust system through the EGR passage,
The compressed air flows back through the trap filter, blowing away the particulate accumulated on the trap filter, and preventing the trap filter from clogging.

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

In Figure 1, 1 is the diesel engine body, 2 is @
3 is the exhaust passage, 4 is the exhaust passage, and 4 is the exhaust passage.
In the turbocharger 4, a turbine 6 rotates at high speed due to the pressure energy of exhaust gas discharged from each stage, and a compressor 5, which rotates together with the turbine 6, sucks air taken in from an air cleaner 7 according to its rotation speed. The engine is designed to supercharge each cylinder. Note that a waste date valve 18 is provided in the middle of the exhaust passage 3 to adjust the amount of exhaust gas bypassing the turbine 6, and the maximum supercharging pressure of the compressor 5 is regulated.

An EGR passage 8 is provided that communicates the exhaust passage 3 and the intake passage 2 and recirculates part of the exhaust gas, and a trap filter 2o is interposed in the middle of the EGR passage 8 to collect particulates in the exhaust gas. This protects the compressor 5.

One layer of the EGR passage 8 is branched into an outlet passage 8A that communicates with the downstream side of the compressor 5 of the intake passage 2, and an auxiliary passage 8B that communicates with the downstream side of the compressor 5. 21 and 22 are respectively interposed. These constitute a valve means that selectively communicates the EGR passage 8 with the upstream side and the downstream side of the compressor 5 of the intake passage 2.

At the other end of the EGR passage 8, an inlet passage 8C that communicates with the upstream side of the turbine 6 of the exhaust passage 3 and an auxiliary passage 8D that communicates with the downstream side of the turbine 6 are branched. 23 and 24 are interposed respectively.

Each of the valves 21, 22, 23, and 24 is opened and closed by the negative pressure generated by the vacuum pump 11 being sent to the respective diaphragm chamber through the negative pressure passage 12 and via each pressure regulating valve 13.

Electronic control unit 1 that controls the operation of each pressure regulating valve 13
4 receives signals from an accelerator lever opening sensor 15 and a rotation sensor 16 provided in the fuel injection pump 10, and connects the EGR passage 8 to the downstream side of the compressor 5 under predetermined operating conditions in the EGR stop region. The compressed air sent from the compressor 5 is made to flow back to the trap filter 20.

In the EGR 11 region, the control unit 14 opens each pulp 21.23 via each pressure regulating valve 13, and closes each pulp 22.24.

As a result, exhaust gas taken into the EGR passage 8 from the upstream side of the turbine 6 is recirculated to the upstream side of the compressor 5 via the trap filter 20.

At this time, the pulp 21 interposed in the outlet passage 8A functions as an EGR control pulp that adjusts the amount of recirculation of the exhaust gas according to a preset control map, so that the exhaust gas effectively removes NOx from the human body. Reduced.

Furthermore, the exhaust gas from which particulates and the like have been removed by the trap filter 20 is guided to the compressor 5, thereby preventing the compressor 5, which rotates at high speed, from being damaged.

The control unit 14 controls each pressure regulating valve 1 under predetermined operating conditions such as during deceleration operation in the EGR stop region or during full load operation.
3, each pulp 22, 24 is opened, and
Each pulp 21.23 is closed. As a result, EGR
The passage 8 communicates the downstream 11I@air passage 2 of the compressor 5 and the downstream 111# air passage 3 of the turbine 6, and a part of the air supercharged to the compressor 5 passes through the EGR passage 8 to the downstream side of the turbine 6. flows. Immediately after deceleration, the compressor 5 continues to rotate, or the supercharging pressure is excessive during full-load operation, so the air pressurized by the compressor 5 flows back through the trap filter 20 and enters the trap filter 20. The accumulated particulates are blown away and discharged into the exhaust passage 3.

This prevents the trap filter 20 from becoming clogged and allows the NOx reduction effect to be maintained by recirculating the exhaust gas.

Note that a trap filter 17 is interposed in the middle of the exhaust passage 3 to prevent particulates from being discharged to the outside. The deposits in the trap filter 17 are automatically combusted and regenerated under operating conditions where the exhaust gas temperature increases.

Next, referring to another embodiment shown in FIG. 2, in this case as well, the other end of the EGR passage 8 is connected to an outlet passage 8A that communicates with the upstream side of the compressor 5 of the intake passage 2, and an outlet passage 8A that communicates with the upstream side of the compressor 5 of the intake passage 2. The auxiliary passage 8B that communicates with the
Pulp 21 and 22 are interposed in the outlet passage 8A and the auxiliary passage 8B, respectively. These constitute a valve means that selectively communicates the EGR passage 8 with the upstream side and the downstream side of the compressor 5 of the intake passage 2.

One end of the EGR passage 8 is connected to the exhaust passage 3 upstream of the turbine 6, and a throttle valve 31 is provided downstream of the opening of the auxiliary passage 8B of the intake passage 2.
is provided with a fest date valve 32 that adjusts the amount of exhaust gas that bypasses the turbine 6. The throttle valve 31 and the waste date valve 32 are provided with a Guya 7 ram device 33 that opens and closes them, and the negative pressure created by the vacuum pump 11 is applied to each Guya 7 ram device 33 through the negative pressure passage 12 to each pressure regulating valve 13. FIIM by being sent via
Operate.

Electronic control unit 1 that controls the operation of each pressure regulating valve 13
4 is an accelerator lever provided on the fuel injection pump 10;
Signals from the opening sensor 15 and rotation sensor 16 are input, and the compressor 5 and throttle valve 3 of the intake passage 2
1, the signal from the pressure sensor 34 provided between The waste date pulp 32 is opened and closed based on the waste date pulp 32 to regulate the maximum boost pressure, while the throttle valve 31 is closed during deceleration operation in the EGR stop region to reduce the pressure in the intake pipe. '−)
After opening the pulp 32 and reducing the pressure inside the exhaust pipe, the EG
The R passage 8 is communicated with the downstream side of the compressor 5. As a result, compressed air from the intake passage 2 is transferred to the trap filter 2.
0 to blow the deposits into the exhaust passage 3111. Further, by closing the throttle valve 31 during deceleration, intake noise can be reduced.

(Effects of the Invention) As described above, the present invention provides an exhaust gas recirculation device that supports a trap filter that collects particulates in the middle of an EGR passage, and prevents the compressor from overloading during deceleration when exhaust gas recirculation is stopped or during full-load operation. Since a part of the supplied compressed air flows back through the trap filter and is guided into the exhaust passage, this air flow blows away the deposits in the trap filter into the exhaust passage, thereby preventing the trap filter from clogging. , the NOx reduction effect due to exhaust gas recirculation is maintained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a configuration diagram showing another embodiment. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Intake passage, 3... Exhaust passage, 4... Turbocharger, 5... Compressor, 6... Turbine, 8... EGR passage, 14...
...Electronic control unit, 15...Accelerator lever opening degree sensor 16...Rotation sensor 20...Trap filter, 21.2L23.24...Pulp. Patent originator Nissan Motor Co., Ltd. agent
Patent Attorney Masaru Goto Figure 4-11 Tarho 4 Ya 2' Electronic Control Wholesale 21.22 Hull 7

Claims (1)

[Claims] Equipped with a compressor that supercharges intake air in the middle of the intake passage,
An EGR passage is provided which communicates the exhaust passage and intake passage upstream of the compressor with each other and recirculates a portion of the exhaust gas.
In an exhaust gas recirculation system for an engine including a trap filter for collecting particulates in exhaust gas in the middle of an EGR passage, a valve means is provided for selectively communicating the EGR passage with an upstream side and a downstream side of a compressor in an intake passage. , through this valve means under predetermined operating conditions in the EGR stop region.
An exhaust gas recirculation system for an engine, characterized in that a control means is provided that connects a GR passage to the downstream side of a compressor and causes compressed air sent from the compressor to flow back into a trap filter.