JPH07253052A - Exhaust gas recirculation controller of engine - Google Patents

Abstract

PURPOSE:To enable the proper control of EGR at the time of acceleration by reducing exhaust gas recirculation amount in correspondence to the of engine speed and load. CONSTITUTION:In an exhaust gas recirculation device of an engine which is provided with a valve means 1 which recirculates exhaust gas of the engine into an air intake system via an exhaust gas recirculation passage and controls exhaust gas recirculation amount step by step, a means 2 for detecting an engine speed, a means 3 for detecting load of the engine, and an exhaust gas recirculation control means 4 which drives the valve means 1 based on the engine speed and load are provided. Furthermore, a means 5 for detecting the acceleration condition of the engine and an exhaust gas recirculation stop means 6 which stops exhaust gas recirculation forcedly via the valve means 1 for a predetermined period of time when exhaust gas recirculation amount in the predetermined acceleration condition is decrease controlled are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas recirculation control device.

[0002]

2. Description of the Related Art In a diesel engine, NO in exhaust gas
In order to reduce x, an exhaust gas recirculation (EGR) device that recirculates a part of the exhaust gas to the intake system is adopted.

An example of the conventional exhaust gas recirculation system for a diesel engine is the one described in Nissan Motor Co., Ltd., New Model Manual, Bluebird (U31-1), published in September 1991.

This is because an EGR valve is provided in an exhaust gas recirculation passage that guides exhaust gas (EGR gas) from an engine exhaust passage, an intake throttle valve is provided in an intake passage upstream of an opening of the exhaust gas recirculation passage, and a control device is provided. It has an EGR map in which the EGR region of I to IV and the EGR cut region are set. Based on the engine speed and the control lever opening (accelerator opening or fuel injection amount), a predetermined electromagnetic field is set according to the control data of the corresponding area. It is designed to drive the EGR valve to full open or half open or full close and the intake throttle valve to full close or half open or full open via the valve, and when the engine load is high, the particulate matter (PM) in the exhaust gas is discharged. In order to prevent the deterioration of (1), EGR is cut and the EGR gas amount is gradually increased as the engine load becomes lighter (EGR region IV → I). You have me.

As described above, the one that controls the exhaust gas recirculation by driving the EGR valve and the intake throttle valve stepwise is more effective than the one that continuously changes the opening degree thereof (to satisfy the required EGR performance to some extent). Control is simplified and the cost is low.

[0006]

However, in such a conventional exhaust gas recirculation control, PM in the exhaust gas, especially soot in the PM (ISF), is generated during acceleration, especially during start acceleration.
Is likely to increase, which is adversely affecting mode emission.

This is because at the time of starting acceleration, the EGR region changes according to the acceleration as shown in FIG. 11, and the amount of EGR gas decreases accordingly.
As can be seen from the actual behavior of EGR with respect to the control value of, this is due to the delay of the flow of residual EGR gas in the intake pipe. It is considered that this delay causes excess fuel with respect to oxygen in the combustion chamber, resulting in deterioration of combustion and part of the partially incompletely burned fuel becoming PM.

FIG. 12 shows the PM emission characteristics immediately after starting the vehicle. When the EGR exceeds a certain level, the PM and emission are greatly deteriorated regardless of the fuel injection timing. That is, the PM deterioration cannot be avoided by controlling the fuel injection timing, and the driving performance and the fuel consumption may deteriorate during the acceleration.

JP-A-60-162048 discloses a technique of closing the EGR valve by closing the EGR valve at the time of sudden acceleration.
It is premised that the R-cut region is entered, and the required EGR cannot be performed when the R-cut region is within the EGR region.

An object of the present invention is to solve such a problem by appropriately reducing the exhaust gas recirculation amount according to the acceleration state.

[0011]

As shown in FIG. 1, a first invention comprises valve means 1 for stepwise controlling the exhaust gas recirculation amount for recirculating engine exhaust gas to an intake system via an exhaust gas recirculation passage. In an exhaust gas recirculation system for an engine, means 2 for detecting the engine speed, means 3 for detecting the engine load, and exhaust gas recirculation control means 4 for driving the valve means 1 based on the engine speed and the load. And a means 5 for detecting the acceleration state of the engine, and an exhaust gas recirculation stop means for forcibly stopping the exhaust gas recirculation through the valve means 1 for a predetermined period during the control of reducing the exhaust gas recirculation amount in the predetermined acceleration state. 6 and are provided.

According to a second aspect of the invention, the predetermined period is determined by the load of the engine before shifting to a predetermined acceleration state.

A third invention is the exhaust gas recirculation control means 4
Has an exhaust gas recirculation map during steady operation and an exhaust gas recirculation map during acceleration operation in which recirculation data is set based on the engine speed and load, and drives the valve means 1 according to the recirculation data of the map. .

[0014]

In the first aspect of the invention, when the acceleration state is entered, the valve means is controlled so as to reduce the exhaust gas recirculation amount in accordance with the acceleration state, that is, in accordance with the engine speed and the load. At this time, the valve means is driven to forcibly stop the exhaust gas recirculation for a predetermined period.

By reducing the exhaust gas recirculation amount while stopping the exhaust gas recirculation for a predetermined period, it becomes possible to perform exhaust gas recirculation control in consideration of the residual EGR gas in the intake pipe while using the valve means that is driven in stages. The reflux rate is reduced as required.

As a result, deterioration of combustion caused by residual EGR gas during acceleration is prevented, and PM and emission are improved.

In the second aspect of the invention, the exhaust recirculation stop period of the first aspect of the invention is determined by the load of the engine before shifting to the predetermined acceleration state, so that the residual EGR gas is accurately reduced.

In the third aspect, in addition to the first aspect, the exhaust gas recirculation amount is controlled more appropriately because the exhaust gas recirculation amount is performed according to the dedicated map data during acceleration.

[0019]

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

In FIG. 2, 20 is an engine, 21 is an intake passage, 22 is an exhaust passage, and 23 is an exhaust gas recirculation passage that connects the exhaust passage 22 to the intake passage 21.

An opening 25 is formed in the exhaust gas recirculation passage 23 on the upstream side of the manifold 24 in the intake passage 21, and a diaphragm type EGR valve 26 is interposed in the opening 25.

A diaphragm type intake throttle valve 27 is provided in the intake passage 21 upstream of the opening 25 of the exhaust gas recirculation passage 23.

The operating negative pressure from the vacuum pump is introduced to the EGR valve 26 and the intake throttle valve 27 through the negative pressure passage, but the first and second negative pressure passages 30 to the EGR valve 26 are provided.
EGR control solenoid valves 31 and 32 are provided.

Turning on (opening) the first EGR control solenoid valve 31
At the same time, operating negative pressure is supplied to the EGR valve 26, and it is turned off (closed).
At that time, the supply is cut off, and the second EGR control solenoid valve 32
The operating negative pressure is diluted by the atmosphere when the
The dilution is blocked at N (closed).

The EGR valve 26 is fully closed when both the first and second EGR control solenoid valves 31, 32 are OFF, and is half-opened when only the first EGR control solenoid valve 31 is ON, When both are turned on, it is fully opened.

In the negative pressure passage 33 to the intake throttle valve 27, first and second intake throttle control electromagnetic valves 35 and 36 are provided.

ON of the first intake throttle control solenoid valve 35
At the time of (opening), the operating negative pressure is supplied to the intake throttle valve 27, and the OF
When F (closed), the supply is cut off, when the second intake throttle control solenoid valve 36 is turned off (open), the operating negative pressure is diluted with the atmosphere, and when it is turned on (closed), the dilution is cut off.

The intake throttle valve 27 is fully opened when both the first and second intake throttle control solenoid valves 35 and 36 are OFF, and is half-opened when only the first intake throttle control solenoid valve 35 is ON. When both are turned on, they are fully closed.

The opening degree of the accelerator 37 is detected by an accelerator opening sensor 38. The fuel injection pump 39, which injects fuel into the engine 20 according to the accelerator opening, is provided with a rotation speed sensor 40 that detects the engine rotation speed from the shaft rotation. The cooling water temperature of the engine 20 is detected by the water temperature sensor 42.

The signals from the sensors 38, 40 and 42 are supplied to the control unit 43 which is a microcomputer.
Entered in. The control unit 43 has an EGR
A control map is provided.

Based on the signals from the sensors 38, 40 and 42, the control unit 43 controls the first,
The second EGR control solenoid valves 31, 32, the first and second intake throttle control solenoid valves 35, 36 are driven, that is, the EGR valve 26,
The intake throttle valve 27 is controlled and EGR control is performed.

Next, the control content of the control unit 43 will be described with reference to the flowchart of FIG. 3. First, in step 1, the engine speed Ne and the accelerator opening degree CL are read.

In step 2, based on the engine speed Ne and the accelerator opening CL, the corresponding EGR region (I to IV, cut region), EGR from the EGR control map of FIG.
Search for data.

This EGR control map has engine speed and accelerator opening set as parameters. Instead of the accelerator opening, a map in which the engine load obtained from the engine speed and accelerator opening is set as a parameter is used. be able to.

In step 3, it is determined based on the accelerator opening degree CL whether or not the vehicle is in the acceleration operation state. The change amount ΔACCEL of the accelerator opening CL within the minute time becomes equal to or larger than the set value A _0, and the change amount ΔNe of the engine speed Ne is set to the set value Ne.
_When it exceeds ₀ , it is determined to be in the accelerated operation state.

In the acceleration operation state, the process proceeds to step 4,
If not, proceed to steps 8 and 9.

At step 4, the EGR cut timer E
It is determined whether it is during the GR cut time. When it is not during the EGR cut time, the routine proceeds to step 5, and when it is during the time, the routine proceeds to step 7.

In step 5, E retrieved in step 2 is searched.
It is determined whether the GR area is different from the previous time. If it is different from the previous time, proceed to steps 6 and 7, and if not, proceed to steps 8 and 9.

At step 6, the EGR cut timer is started and the EGR cut flag is turned on.

In step 7, E retrieved in step 2 is searched.
Regardless of the GR region and EGR data, the EGR cut signal (OFF signal) is transmitted to the first and second EGR control solenoid valves 3
It outputs to 1, 32. That is, the EGR valve 26 is fully closed.

At step 8, the EGR cut timer is reset and the EGR cut flag is turned off.

In step 9, E retrieved in step 2 is searched.
A control signal corresponding to the EGR data in the GR region is output to the first and second EGR control solenoid valves 31, 32 and the first and second intake throttle control solenoid valves 35, 36.

In the EGR region I, the EGR valve 26 is fully opened, the intake throttle valve 27 is fully closed, and in the EGR region II, E
GR valve 26 fully open, intake throttle valve 27 half open, EGR region
In the case of III, the EGR valve 26 is fully opened, the intake throttle valve 27 is fully opened, in the EGR region IV, the EGR valve 26 is half opened, the intake throttle valve 27 is fully opened, and in the EGR cut region, the EGR valve is EGR
Signals are output to the first and second EGR control solenoid valves 31 and 32 and the first and second intake throttle control solenoid valves 35 and 36 so that the valve 26 is fully closed and the intake throttle valve 26 is fully opened ( EG
R region I, II, III, IV are large in this order).

When the engine cooling water temperature is low,
Similarly to the EGR cut region, EGR is stopped.

That is, when the vehicle is not in the acceleration operation state, in steps 2 and 9, the EGR valve 26 and the intake throttle valve 27 are driven in accordance with the EGR region corresponding to the operation state (Ne, CL) at that time.

When the acceleration operation state is entered and the operation state is changed in steps 2 and 5 and the corresponding EGR region is different from the previous time, the EGR cut timer is started in steps 6 and 7 and the EGR valve 26 is fully closed. To do.

When the EGR cut time has passed, the EGR cut timer is reset in steps 8 and 9, and the EGR valve 26 and the intake throttle valve 27 are set according to the changed EGR region.
To drive.

Following this, when the operating state changes in steps 2 and 5 and the corresponding EGR region differs from the previous time, the EGR cut timer is started again in steps 6 and 7.
The EGR valve 26 is fully closed.

When the EGR cut time has passed, the EGR cut timer is reset in steps 8 and 9, and the EGR valve 26 and the intake throttle valve 27 are set according to the changed EGR region.
To drive.

This is repeated until the area does not change.

With such a configuration, when the acceleration operation is performed and the corresponding EGR region changes depending on the operation state,
According to this, the drive of the EGR valve 26 and the intake throttle valve 27 is switched, and the EGR amount is reduced, but every time the EGR region changes, the EGR valve 26 is fully closed for a predetermined period,
R is temporarily cut.

For example, when the EGR region changes from I to II to III, the EGR valve 26 in the fully open state is fully closed for a predetermined period, after which the EGR valve 26 is fully opened and the intake throttle valve 27 in the fully closed state is half opened. Then, the EGR valve 26 is fully closed for a predetermined period of time, and then the EGR valve 26 is fully opened and the intake throttle valve 27 in the half-open state is fully opened.

That is, the EGR gas is temporarily cut during the transition of the change of the EGR region, so that the residual EGR gas in the intake pipe before the transition is reduced. As a result, the EGR valve 26 and the intake throttle valve 27 that are driven in stages cause the EGR valve 26 to
The amount is accurately reduced.

Therefore, EGR does not become excessive during acceleration, acceleration performance and fuel efficiency are improved, and EGR is improved.
It is possible to reliably prevent the deterioration of the particulate matter (PM) and the emission due to.

The amount of decrease in the EGR amount corresponds to NOx during acceleration.
Although the amount of emission increases, the amount of increase in NOx emission is small compared to the amount of deterioration of PM when the amount of EGR is not decreased, and the amount of deterioration is due to proper control of fuel injection timing and other EGR. Improvement is easy by optimizing the area.

FIG. 5 shows another embodiment of the present invention, in which the EGR cut period is determined by the load of the engine before shifting to the acceleration state.

In step 11, the engine speed Ne and the accelerator opening CL are read.

In step 12, based on the engine speed Ne and the accelerator opening degree CL, the corresponding EGR region (I to IV, cut region), EG from the EGR control map of FIG.
Search R data.

At step 13, it is judged whether or not the vehicle is in the accelerated operating state based on the accelerator opening degree CL. If the vehicle is in the accelerated operating state, the process proceeds to step 14, otherwise, the step 1
Proceed to 9, 20.

In step 14, it is judged whether or not the EGR cut timer is in the EGR cut time. If it is not in the EGR cut time, the process proceeds to step 15, and if it is, the process proceeds to step 18.

In step 15, it is determined whether the EGR area searched in step 12 is different from the previous time. If it is different from the previous time, the process proceeds to steps 16 to 18, and if not, the process proceeds to steps 19 and 20.

Then, in step 16, the engine load is obtained from the engine speed Ne and the accelerator opening CL read in step 11 before entering the acceleration operation state, and based on this engine load, based on the data table of FIG. E
Calculate and set the GR cut time.

In this case, each EGR in each EGR region
Calculate and set the cut time. The lower the engine load, the longer the EGR cut time, but an upper limit is set for the EGR cut time.

In step 17, the EGR cut timer is started and the EGR cut flag is turned on.

In step 18, the EGR cut signal (OFF signal) is output to the first and second EGR control solenoid valves 31, 32 regardless of the EGR region and EGR data retrieved in step 12, and the EGR valve 26 is turned on. Fully close.

At step 19, the EGR cut timer is reset and the EGR cut flag is turned off.

In step 20, the control signals corresponding to the EGR data in the EGR region retrieved in step 12 are sent to the first and second EGR control solenoid valves 31, 32, the first and second intake throttle control solenoid valves 35, 35. Output to 36.

That is, when the acceleration operation is performed, every time the EGR region is changed, the EGR valve 26 is fully closed for a predetermined period corresponding to the engine load before the acceleration operation is started.

As a result, when the engine load is small and the amount of residual EGR gas in the intake pipe is large, the EGR is cut for a longer period, and the residual EGR gas is properly reduced.

Therefore, as shown in FIG. 7, the EGR amount can be reduced as required during acceleration, the acceleration performance and fuel consumption can be improved, and PM and emission can be improved.

By properly setting the EGR cut time, the EGR amount does not decrease too much, so that the deterioration of NOx due to the EGR cut can be minimized.

FIG. 8 shows another embodiment of the present invention, in which the EGR map based on different EGR maps for steady operation and acceleration operation is used.
The control is performed.

At step 21, the engine speed Ne and the accelerator opening CL are read.

In step 22, it is judged based on the accelerator opening degree CL whether or not the vehicle is in the accelerating operation state. In the accelerating operation state, the routine proceeds to step 23, and in the steady operation state, the routine proceeds to step 31.

At step 23, the engine speed N
Based on e and accelerator opening degree CL (or fuel injection amount),
From the EGR control map during acceleration operation set as shown in FIG. 9, the corresponding EGR region (III, IV, cut region), E
Search GR data.

In step 24, it is determined whether or not the EGR cut timer is in the EGR cut time. If the EGR cut time is not reached, the process proceeds to step 25, and if it is, the process proceeds to step 27.

In step 25, it is determined whether or not the EGR area retrieved in step 23 is different from the previous time. If it is different from the previous time, the process proceeds to steps 26 to 28. If not, the process proceeds to steps 29 and 30.

In step 26, the engine load is obtained from the engine speed Ne and the accelerator opening CL read in step 21 before entering the acceleration operation state, and the EGR cut time in each EGR region is calculated by this engine load. Calculate and set.

In step 27, the EGR cut timer is started and the EGR cut flag is turned on.

In step 28, an EGR cut signal (OFF signal) is output to the first and second EGR control solenoid valves 31 and 32 regardless of the EGR region and EGR data retrieved in step 23, and the EGR valve 26 is turned on. Fully close.

In step 29, the EGR cut timer is reset and the EGR cut flag is turned off.

In step 30, the control signals corresponding to the EGR data of the EGR region retrieved in step 23 are supplied to the first and second EGR control solenoid valves 31, 32, the first and second intake throttle control solenoid valves 35, 35. Output to 36.

On the other hand, when the routine proceeds to step 31, based on the engine speed Ne and the accelerator opening degree CL (or the fuel injection amount), the corresponding EGR region (I ~ IV, cut region) and EGR data are searched, and the process proceeds to steps 32 and 33.

At step 32, the EGR cut timer is reset and the EGR cut flag is turned off.

In step 33, the control signals corresponding to the EGR data of the EGR region retrieved in step 31 are sent to the first and second EGR control solenoid valves 31, 32, the first and second intake throttle control solenoid valves 35, 35. Output to 36.

In this way, optimum EGR can be secured during steady operation and acceleration operation.

In particular, by setting the EGR control map of the regions III and IV in which the EGR amount is small and the cut region during the acceleration operation as shown in FIG. 9, the EGR amount can be more accurately and promptly reduced during the acceleration. .

[0088]

As described above, according to the first aspect of the present invention, the engine exhaust gas recirculation system is provided with the valve means for stepwise controlling the exhaust gas recirculation amount for recirculating the engine exhaust gas to the intake system via the exhaust gas recirculation passage. In which the means for detecting the number of revolutions of the engine, the means for detecting the load of the engine, and the exhaust gas recirculation control means for driving the valve means based on the number of revolutions and the load of the engine are provided, while the acceleration state of the engine Means for detecting the exhaust gas recirculation amount and the exhaust gas recirculation amount stopping means for forcibly stopping the exhaust gas recirculation amount through the valve means for a predetermined period when controlling the reduction of the exhaust gas recirculation amount in a predetermined acceleration state. Can be accurately reduced, acceleration performance and fuel can be improved, and deterioration of PM and emission can be prevented.

According to the second aspect of the present invention, the predetermined period is determined by the load of the engine before shifting to the predetermined acceleration state, so the exhaust gas recirculation amount is appropriately reduced during acceleration, and N
PM and emission can be improved while preventing deterioration of Ox.

According to the third invention, optimum exhaust gas recirculation control can be performed during steady operation and acceleration operation based on a dedicated exhaust gas recirculation map.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention.

FIG. 2 is a configuration cross-sectional view of an example.

FIG. 3 is a flowchart showing control contents.

FIG. 4 is a characteristic diagram showing an EGR control map.

FIG. 5 is a flowchart of another embodiment.

FIG. 6 is a characteristic diagram showing an example of setting an EGR map time.

FIG. 7 is an explanatory diagram showing a reduced state of EGR.

FIG. 8 is a flowchart of another embodiment.

FIG. 9 is a characteristic diagram showing an EGR control map during acceleration.

FIG. 10 is a table showing an EGR control map in a steady state.

FIG. 11 is an explanatory diagram showing a state in which EGR is reduced in a conventional example.

FIG. 12 is a characteristic diagram showing a discharged state of particulates.

[Explanation of symbols]

 20 engine 21 intake passage 22 exhaust passage 23 exhaust gas recirculation passage 25 opening 26 EGR valve 27 intake throttle valve 31 first EGR control solenoid valve 32 second EGR control solenoid valve 35 first intake throttle control solenoid valve 36 second Intake throttle control solenoid valve 37 Accelerator 38 Accelerator opening sensor 39 Fuel injection pump 40 Revolution sensor 42 Water temperature sensor 43 Control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02D 45/00 376 C

Claims (3)

[Claims] 1. An exhaust gas recirculation system for an engine, comprising means for stepwise controlling an exhaust gas recirculation amount for recirculating engine exhaust gas to an intake system via an exhaust gas recirculation passage, and means for detecting an engine speed. Means for detecting the load on the engine and exhaust gas recirculation control means for driving the valve means based on the engine speed and load are provided, while means for detecting the acceleration state of the engine and exhaust gas in a predetermined acceleration state are provided. An exhaust gas recirculation control device for an engine, comprising: an exhaust gas recirculation stop means for forcibly stopping exhaust gas recirculation through the valve means during a reduction control of the recirculation amount. 2. The exhaust gas recirculation control device for an engine according to claim 1, wherein the predetermined period is determined by the load of the engine before shifting to a predetermined acceleration state. 3. The exhaust gas recirculation control means has an exhaust gas recirculation map during steady operation and an exhaust gas recirculation map during acceleration operation in which recirculation data is set based on the engine speed and load, respectively, and the exhaust gas recirculation map for the map is recirculated. The exhaust gas recirculation control device for an engine according to claim 1, wherein the valve means is driven according to data.