WO2006064671A1

WO2006064671A1 - Exhaust gas purification device for diesel engine

Info

Publication number: WO2006064671A1
Application number: PCT/JP2005/022127
Authority: WO
Inventors: Daisuke Yamazaki
Original assignee: Bosch Corporation
Priority date: 2004-12-13
Filing date: 2005-11-25
Publication date: 2006-06-22

Abstract

An exhaust gas purification device (30) in which an oxidation catalyst (31) is placed on the upstream side of a filter section (32) that collects particulates in the exhaust gas of a diesel engine (1) and, in regeneration of the filter section (32), unburned fuel is supplied from a supply device (38) to the oxidation catalyst (31). A filter control unit (40) for regeneration control is provided with a signal output section that outputs an operation stop signal (S6A) for stopping the operation of exhaust gas recirculation when the supply device (38) starts its operation and also outputs signal (S6B) for permitting valve opening operation of an EGR control valve (17) after the elapse of a predetermined delay time (t) from the time at which a command to stop the operation of the supply device (38) is issued to finish the regeneration operation. This effectively prevents the unburned fuel from flowing around into the suction side of the diesel engine via an exhaust gas recirculation control system.

Description

Description Exhaust purification device for diesel engine

Technical field

The present invention relates to an exhaust emission control device for a diesel engine. Background art

In recent years, in order to suppress the diffusion of particulates (fine particles) contained in the exhaust gas of a diesel engine into the atmosphere, the diesel particulates in the exhaust gas have been installed in the exhaust system of the diesel engine in recent years. Various devices have been developed for post-processing. As this type of exhaust gas treatment device, a device equipped with a filter for collecting particulates contained in exhaust gas discharged from a diesel engine when the exhaust gas passes through the exhaust passage is being put into practical use. As particulates collected in a force filter accumulate, losses due to increased exhaust resistance gradually increase and eventually the filter becomes clogged.

Therefore, in the case of an exhaust purification device using a filter, an oxidation catalyst is provided in the front stage of the filter, and the temperature of the exhaust gas passing therethrough is raised by supplying unburned fuel to the oxidation catalyst and collected in the filter. Conventionally, a filter regeneration control system that promotes the combustion of the particulate soot has been employed (Japanese Patent Application Laid-Open No. 11-11001 2 2).

On the other hand, an exhaust gas recirculation control device (EGR control device) may be installed in the exhaust system of a diesel engine to improve the combustion state of the diesel engine. In this case, since the filter regeneration control system using the oxidation catalyst and the EGR control system coexist, the EGR control is performed when unburned fuel is supplied to the oxidation catalyst during the regeneration control of the exhaust gas purification device. The engine is stopped so that unburned fuel is not fed into the cylinder of the diesel engine and fuel combustion in the cylinder is not accelerated.

Specifically, for example, the timing of ending the supply of unburned fuel to the exhaust purification device Therefore, the EGR control valve is gradually opened by ramp control, and this increases the recirculation amount of exhaust gas to the intake side. However, according to the conventional configuration described above, even if the supply of unburned fuel to the oxidation catalyst is stopped by the start of EGR control, unburned fuel remains in the exhaust gas sent to the exhaust purification device. There is a problem that unburned fuel remaining in the exhaust gas flows into the intake side of the diesel engine together with the recirculated exhaust gas, which hinders EGR control.

An object of the present invention is to provide an exhaust emission control device for a diesel engine that can solve the above-mentioned problems in the prior art.

Another object of the present invention is to provide an exhaust emission control device for a diesel engine that can effectively prevent unburned fuel supplied during filter regeneration from entering the intake side of the engine via an EGR control system. It is to provide. Disclosure of the invention

A feature of the present invention for solving the above problems is that exhaust gas from a diesel engine equipped with an exhaust gas recirculation control system having an EGR control valve for adjusting the exhaust gas recirculation amount is disposed after the exhaust gas. An exhaust purification device for processing, a filter unit for collecting particulates contained in exhaust gas, an oxidation catalyst unit disposed upstream of the filter unit, and an oxidation catalyst unit A supply device for supplying unburned fuel; and a control unit for controlling the supply unit for regeneration of the filter unit, wherein the control unit starts the operation of the supply unit. A signal output unit that outputs a valve opening operation permission signal for the EGR control valve with a delay of a predetermined time from the operation stop signal for stopping the exhaust gas recirculation operation and the timing at which the operation stop of the supply device is commanded. With There is in point.

According to the present invention, it is effective that unburned fuel mixed in the exhaust gas for regeneration of the exhaust gas purification device wraps around the intake side of the diesel engine through the exhaust gas recirculation control system. Can be prevented. Brief Description of Drawings FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a filter regeneration control program executed in the filter control unit.

FIG. 3 is a diagram for explaining the control operation of the EGR control valve. BEST MODE FOR CARRYING OUT THE INVENTION

In order to describe the present invention in more detail, it will be described with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram showing an embodiment of an exhaust emission control device according to the present invention. Reference numeral 1 indicates a four-cylinder diesel engine, and each cylinder 2-5 is provided with an indicator 6-9. These injectors 6 to 9 are controlled by an engine control unit 10 and have a known configuration capable of injecting and supplying high pressure fuel into a corresponding cylinder in a required amount at a required timing.

The intake duct 12 connected to the intake manifold 1 1 is provided with an intercooler 1 3 and an air cleaner 14, while the exhaust connected to the exhaust manifold 1 5. The duct 16 is provided with an exhaust purification device 30 according to the present invention.

Between the intake duct 1 2 and the exhaust duct 16 is provided an exhaust gas recirculation path 18 provided with an EGR control valve 17. The amount of exhaust gas flowing through the exhaust duct 1 6 is returned to the intake manifold 1 1 by adjusting the opening degree of the EGR control valve 1 7 by the actuator control 1 9 controlled by the engine control unit 1 0. An exhaust gas recirculation control system of known construction that can be adjusted is provided. Reference numeral 20 denotes an exhaust turbocharger, which is disposed in the exhaust duct 16 and the exhaust duct 21 and is driven by the exhaust turbine 21. Comprised with 2 and 2 compressors.

The exhaust purification device 30 includes an oxidation catalyst unit 31 and a filter unit 32 for collecting particulates, and is arranged in this order from the upstream side on the exhaust duct 16. The oxidation catalyst portion 31 is formed by forming a washcoat layer by coating activated alumina or the like on the surface of a carrier made of, for example, honeycomb-shaped cordierite or heat-resistant steel. An appropriate catalytically active component is supported on one base layer. With the above configuration, the oxidation catalyst unit 31 oxidizes NO in the exhaust gas to generate N 0 ₂ , and oxidizes HC and CO in the exhaust gas to generate H ₂ 0 and C 0 ₂ . Can be generated. The filter section 32 is a so-called honeycomb-flow type honeycomb filter in which a large number of cells are formed in parallel with, for example, porous cordierite or silicon carbide, and the inlet and outlet of the cells are alternately closed. In addition, it has a known configuration using a fiber type filter in which ceramic fibers are wound in several layers around a stainless porous tube and collects particulates in exhaust gas.

A first pressure sensor 33 and a second pressure sensor 34 for detecting the pressure of the exhaust gas are provided on the inlet side (front) and the outlet side (rear) of the filter section 32, respectively. The first pressure sensor 3 3 outputs a first pressure signal S 1 indicating the exhaust gas pressure P 1 on the inlet side of the filter section 3 2, and the second pressure sensor 3 4 exhausts on the outlet side of the filter section 3 2. A second pressure signal S 2 indicating the gas pressure P 2 is output. Further, a first temperature sensor 36 and a second temperature sensor 37 for detecting the temperature of the exhaust gas are provided on the inlet side (front) and the outlet side (rear) of the filter section 32, respectively. Yes. A first temperature signal S 3 indicating the temperature T 1 before the filter section 3 2 is output from the first temperature sensor 3 6, and a second temperature indicating the temperature T 2 after the filter section 3 2 is output from the second temperature sensor 3 7. Temperature signal S4 is output.

Reference numeral 35 indicates a flow rate sensor for detecting the flow rate of the exhaust gas flowing in the exhaust duct 16, and the exhaust flow rate signal F indicating the detected flow rate is the first pressure signal S 1, The second pressure signal S2, the first temperature signal S3, and the second temperature signal S4 are input to the filter control unit 40.

The filter control unit 40 is an element constituting the exhaust purification device 30. The filter control unit 40 is configured as a computer control system using a microcomputer 40 A and receives data M necessary for filter control from the engine control unit 10. The filter control unit 40 estimates the amount of accumulated particulate matter collected by the filter unit 32. Based on this estimation result, the filter control unit 40 determines that the amount of particulate accumulation has exceeded a predetermined level. , H Filter control for regenerating the filter unit 3 2 is performed.

Reference numeral 38 denotes a supply device for supplying fuel in a fuel tank (not shown) to the exhaust gas purification device 30 for the regeneration of the filter unit 32. The supply device 3 8 is disposed on the upstream side of the oxidation catalyst unit 31. In the present embodiment, the supply device 38 is provided in the middle of the exhaust duct 16 and between the exhaust manifold 15 and the exhaust recirculation path 18. In response to the regeneration control signal S 5 from the filter control unit 40, a solenoid valve (not shown) provided in the supply device 38 is activated, and the supply nozzle 3 8 Combustion fuel is injected into the exhaust duct 16 in a known configuration.

The filter control unit 40 allows the fuel supplied from the supply device 3 8 to flow into the intake duct 12 through the exhaust gas recirculation path 18 when the operation of the supply device 38 starts. In order to prevent the exhaust gas recirculation operation from occurring, an operation stop signal S 6 A is output, and in addition to the timing at which the operation stop of the supply device 3 8 is commanded by the regeneration control signal S 5 The EGR control valve 17 has a signal output section that outputs the valve opening operation permission signal S 6 B to the engine control unit 10 after a delay.

FIG. 2 is a flowchart showing a filter regeneration control program executed in the microcomputer 40 A of the filter control unit 40. The filter control unit 40 will be described below with reference to the flowchart in FIG. The filter regeneration control program 50 is repeatedly executed at predetermined time intervals. When the execution of the filter regeneration control program 50 is started, step 51 is entered first to determine whether or not the regeneration condition is satisfied. Here, the front-rear differential pressure Δ Ρ (= P 1 — P 2) of the filter 3 2 is calculated in response to the first pressure signal S 1 and the second pressure signal S 2, and the resulting front-rear differential pressure Based on the value of ΔP, the accumulated amount of particulates in the filter 3 2 is estimated, and it is determined whether or not the regeneration of the filter 3 2 should be performed according to the estimation result. .

If it is determined that the reproduction condition is not satisfied, the determination result of step 51 is N 0, and the process of step 51 is repeated again. Meanwhile, playback conditions in step 5 1 If it is determined that is satisfied, the determination result in step 51 is YES, and the process proceeds to step 52.

In step 52, a reproduction start instruction process is executed. That is, the regeneration control signal S 5 is output, and the supply device 3 8 responds to the start of the administration of unburned fuel in the exhaust gas, and the operation stop signal S 6 A is output and the engine control unit 10 is output. The engine control unit 10 is instructed to shut off the EGR control valve 17 by the operation stop signal S 6 A. As a result, unburned fuel is supplied into the exhaust gas from the supply device 38, and is supplied to the oxidation catalyst unit 31 together with the exhaust gas. At the same time, the EGR control valve 17 is closed. Therefore, when the exhaust gas purification device 30 is in the regeneration control mode, the EGR control valve 17 is closed, and the unburned fuel in the exhaust gas passes through the exhaust gas recirculation path 18 and the diesel engine 1 It is surely prevented from going around to the intake side.

In the next step 53, it is determined by a known method whether or not the reproduction completion condition is satisfied. This determination is made based on the first and second temperature signals S 3 and S 4 and the exhaust flow signal F. If it is determined in step 53 that the playback completion condition is not satisfied, the determination result in step 53 is NO, and the processing of steps 51, 52, 53 is executed again.

If it is determined in step 53 that the playback completion condition is satisfied, the determination result in step 53 is YES, and the process proceeds to step 54. In step 54, playback stop instruction processing is executed. That is, the regeneration control signal S 5 stops the unburned fuel from the supply device 38 from being injected into the exhaust gas, and the opening of the £ 0 control valve 17 is determined, and the process proceeds to step 55 .

In step 55, the valve opening operation permission signal S is delayed by the delay time t set in step 56 from the valve opening instruction timing t1 at which opening of the EGR control valve 17 was determined in step 54. 6 B is output, and the execution of the filter regeneration control program 50 ends.

The valve opening permission signal S 6 B is sent to the engine control unit 10. In the engine control unit 10, the EGR control valve 17 is turned on in response to the valve opening operation permission signal S 6 B. Thus, the execution of the exhaust gas recirculation control is resumed.

Since the exhaust purification device 30 is configured as described above, when unburned fuel is supplied into the exhaust duct 16 from the supply device 3 8 for regeneration of the filter section 32, 0 1 Control valve 1 7 is closed, so that unburned fuel remaining in the exhaust duct 16 does not enter the intake side of the diesel engine 1. Then, after the regeneration of the filter unit 3 2 is finished and the supply of unburned fuel from the supply device 3 8 is stopped, the EGR control valve 17 is opened for the time determined by the delay time t. There is nothing.

For this reason, by setting the delay time t appropriately, the concentration of unburned fuel in the exhaust duct 16 does not adversely affect EGR control after the regeneration of the filter section 32 is completed. The EGR control can be started with the state lowered to Therefore, when the exhaust gas purification device 30 is provided in the diesel engine 1 equipped with the exhaust gas recirculation control system, the exhaust gas purification device 30 has not been placed in the exhaust duct 16 for regeneration of the filter unit 32. Even if the combustion fuel is supplied, it is possible to reliably prevent the unburned fuel supplied for filter regeneration via the exhaust gas recirculation control system from flowing into the intake side of the diesel engine 1.

FIG. 3 is a diagram for explaining this operation. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the opening of the EGR control valve 17. When fuel supply from the supply device 3 8 to the filter unit 3 2 is started at time t 1, an operation stop signal S 6 A is output, and thereby the opening degree of the EGR control valve 17 rapidly becomes zero, Thereafter, the fuel supply from the supply device 38 to the filter unit 32 ends at a time t2 when a given fuel supply time TF has elapsed. In the example of Fig. 3, as shown by the broken line, unlike the case where the opening of the EGR control valve is gradually increased immediately after time t2, as shown by the solid line, it is delayed after time t2. After the elapse of time t, the valve opening operation permission signal S 6 is output, thereby permitting the valve opening operation of the EGR control valve 17, and the opening degree of the EGR control valve 17 is gradually increased. By setting the delay time t appropriately, the opening of the EGR control valve 17 is forcibly compared to the case indicated by the broken line that gradually increases the opening of the EGR control valve 17 immediately after time t2. Fuel supply time, which is essentially zero, unburned fuel in exhaust manifold 1 5 during TF The fee can be discharged without being recycled. Industrial applicability

According to the present invention, it is possible to appropriately control the fuel injection operation for activating the catalyst, which is useful for improving the exhaust gas aftertreatment device.

Claims

The scope of the claims

1. An exhaust gas purification device for post-processing exhaust gas of a diesel engine provided with an exhaust gas recirculation control system having an EGR control valve for adjusting an exhaust gas recirculation amount, wherein the exhaust gas is recirculated A filter unit for collecting the particulate contained therein, an oxidation catalyst unit disposed upstream of the filter unit, a supply device for supplying unburned fuel to the oxidation catalyst unit, A control unit for controlling the supply unit for regeneration of the filter unit, and the control unit operates to stop the exhaust gas recirculation operation when the operation of the supply unit is started. A signal output unit that outputs a stop signal and outputs a valve opening operation permission signal of the EGR control valve with a delay of a predetermined time from the timing at which the operation stop of the supply device is commanded is provided. Di Exhaust emission control device for the diesel engine.

2. a regeneration condition determining unit for determining whether or not a regeneration condition for regeneration of the filter unit is satisfied; and when the regeneration condition determining unit determines that the regeneration condition is satisfied, The exhaust gas purification device for a diesel engine according to claim 1, further comprising a regeneration start instruction processing unit that executes a regeneration start instruction process of the filter unit.

3. The exhaust emission control device for a diesel engine according to claim 2, wherein the operation stop signal is output when the regeneration start instruction processing unit is instructed to start regeneration of the filter unit. .

4. The exhaust emission control device for a diesel engine according to claim 2 or 3, wherein the establishment of the regeneration condition is determined based on a temperature differential pressure across the filter section.

5. The control unit determines whether the regeneration of the filter unit is completed or not. The claim 1 further comprising: an end condition determining unit; and a regeneration stop processing unit that executes the filter regeneration stop process when the regeneration completion condition determining unit determines that the regeneration completion condition is satisfied. Exhaust purification device for diesel engines.

6. When the regeneration stop processing unit is instructed to stop the operation of the supply device unit, the valve opening operation permission signal is output with a delay of a predetermined time from the timing of the instruction. 2. An exhaust emission control device for a diesel engine according to the item.

7. The exhaust emission control device for a diesel engine according to claim 5 or 6, wherein the establishment of the regeneration completion condition is determined on the basis of the temperature before and after the filter section and the exhaust gas flow rate. .