JPS63198765A - Exhaust gas recirculation control method for diesel engine - Google Patents

Abstract

PURPOSE:To prevent smoke or white smoke from occurring by controlling the EGR quantity in response to the change quantity of the corrected rotating speed on condition that the corrected rotating speed is changed by a preset quantity during the preset low-speed rotation of an engine when EGR is performed even at the low-speed rotation. CONSTITUTION:When an EGR valve 54 provided on the EGR passage 53 of a Diesel engine with supercharger 10 is to be controlled by an ECU 56, first the normal EGR control duty ratio is calculated based on the engine rotating speed, fuel injection quantity, and accelerator opening, then whether the engine operation state is an idle state or not is judged. If YES is judged, the dedicated EGR control duty ratio Di is calculated, the the difference between the current value and the previous value of the engine rotation correction quantity (rotating speed difference) is determined, and the EGR correction duty ratio DELTAEGR is calculated based on this rotating speed difference via a map. The value obtained by subtracting DELTAEGR from Di is used as the control duty ratio to control a negative pressure adjusting valve 55 and control the EGR valve 54.

Description

[Detailed description of the invention] [Industrial application field]

The present invention provides exhaust gas recirculation for diesel engines. ? The present invention relates to a control method, and particularly to an improvement in a diesel engine exhaust gas recirculation control method suitable for use in an electronic RRJ control diesel engine for automobiles.

[Conventional technology]

In diesel engines used in vehicles such as automobiles, N is a harmful component in exhaust gas. For the purpose of reducing X, some vehicles employ exhaust gas recirculation (hereinafter referred to as EGR). This EGR is
Conventionally, the engine was cut off at low speeds, but in recent years, with stricter exhaust gas regulations, it has been considered to perform EGR even at low speeds, including during idling.

[Problems to be solved by the invention]

However, when the power steering device is idle,
When a load such as an air conditioner (hereinafter referred to as an air conditioner) or an automatic transmission (hereinafter referred to as a torque converter) or an electrical load is applied, the engine load increases, so the fuel injection amount increases. At this time, if the same EGR level as normal idling is applied, smoke and white smoke will increase even when idling, which will not only greatly damage the image of the vehicle, but also cause the engine to stall in the worst case. Sometimes I put it away. This is because when EGR is applied, the ignitability of the fuel becomes slower.
This is because there is a large amount of unburned gas, which is emitted as smoke or white smoke. In addition, since it becomes difficult to burn, the output torque of the engine decreases, so there is a problem that the engine may stall, especially when a load is applied to the power steering device. Regarding these problems, the applicant has already filed a patent application in 1986-
006962, when a load is applied by an engine-driven device such as an air conditioner or a power steering device head when the engine speed is below a set value, the load is detected with a simple configuration and EGR is performed. This paper proposes an exhaust gas recirculation 5H control method for an electronically controlled diesel engine that prevents an increase in smoke and white smoke by setting the amount to yAm or zero. However, in this method, EGRi is controlled according to the target fuel injection amount at low speeds, for example, when idling, but the target fuel injection amount at idling is f1r! Since the absolute value of the n injection amount is affected by variations in the fuel injection control system, such as manufacturing tolerances of the fuel injection pump, there is a problem that an appropriate EGR level may not be obtained near the upper and lower limits of the variations in the intermediate system. There was a point. In addition, in a diesel engine that performs idle speed control to control the engine speed to a predetermined value at low engine speed, the applicant of the present application has disclosed, for example, Japanese Patent Application No. 61-24225.
As shown in 5, depending on the amount of change in the corrected rotation speed, E
It is conceivable to control the GR corrected view. However, when controlling the EGR correction amount in this way, the EGR, base, and may change, making it impossible to prevent the generation of white smoke or smoke.Also, due to variations in engine characteristics or operating conditions before idling, optimal EGR may not be possible and emission characteristics may vary. There is a problem.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to easily detect from a change in the corrected rotation speed that a load is applied by an engine driven device at low rotation speed, and to detect smoke at that time. The purpose of the present invention is to provide an exhaust gas recirculation control method for a diesel engine that can prevent the generation of smoke and white smoke, and reduce variations in emissions due to variations in engine characteristics and variations in operating conditions before idling. shall be.

[Means to solve the problem]

The present invention provides an EGR CIJ control method for a diesel engine in which the engine speed is controlled to a predetermined value at low speeds and EGR is performed even at low speeds, when the engine speed is below a set value, The above objective is coupled by controlling EGRJi according to the amount of change in the corrected engine speed, provided that the corrected engine speed when controlling the engine speed to a predetermined value changes by a predetermined amount or more. It is.

[Effect]

In the present invention, the engine rotational speed at low rotational speed is set to a predetermined value y.
When the engine speed is below the set value, the ECrRf dead zone is set to To provide this, the EGR amount is controlled according to the amount of change in the corrected rotation speed, provided that the corrected rotation speed has changed by a predetermined amount or more. It is possible to easily detect torque converter load, etc. from changes in the corrected rotation speed, and reliably prevent the generation of smoke or white smoke, as well as to prevent variations in characteristics that differ from engine to engine, and to prevent operation before it becomes idling. It is possible to perform EGR optimally in response to variations in conditions and reduce variations in emission properties.Therefore, it is possible to prevent EGR from being applied too much during high load conditions during idling, thereby preventing engine stalls. [Example] Hereinafter, an example of an electronically controlled diesel engine for automobiles in which the EGR control method according to the present invention is adopted will be described in detail with reference to the drawings. An intake air temperature sensor 12 is provided downstream of the air cleaner 11 to detect the temperature of intake air. a turbine 14A;
A turbocharger 14 consisting of a compressor 14B rotated in conjunction with the engine is provided. The upstream and downstream sides of the turbine 14A of the turbocharger 14 are communicated via a wastegate valve 15 for preventing an excessive rise in intake pressure. The venturi 16 downstream of the compressor 14B includes:
A main intake throttle valve 18 is provided, which is configured to rotate non-linearly in conjunction with an accelerator pedal 17 disposed at the driver's seat, for restricting the flow of intake air during idling. The opening degree of the accelerator pedal 17 (hereinafter referred to as the accelerator opening degree) ACCp is detected by the accelerator sensor 20. A sub-intake throttle valve 22 is provided in parallel with the main intake throttle valve 18 , and the opening degree of the sub-intake throttle valve 22 is controlled by a diaphragm device 24 . Negative pressure generated by a negative pressure pump (not shown) is supplied to the diaphragm device 24 via a pressure cutoff valve (hereinafter referred to as SV) 28 or 30. An intake pressure sensor 32 for detecting the pressure of intake air is provided downstream of the intake throttle valve 18.22. In the cylinder head 10A of the diesel engine 10,
An injection nozzle 34 whose tip faces the engine combustion chamber 10B, a glow plug 36, and an ignition timing sensor 38 are provided. Further, the cylinder block IOC of the diesel engine 10 is equipped with a water temperature sensor 40 for detecting the engine cooling water temperature. Fuel is fed under pressure to the injection nozzle 34 from an injection pump 42 . The injection pump 42 includes a pump drive shaft 42A that rotates in conjunction with the rotation of the crankshaft of the diesel engine 10, and a feed pump 42B (a second pump) fixed to the pump drive shaft 42A for pressurizing fuel. (The figure shows a 90° unfolded state), a fuel pressure adjustment valve 42C for adjusting the fuel supply pressure, and the pump drive shaft 42A.
The rotational displacement of the driving shaft pulley 42D determines the engine crank angle reference position, such as top dead center (TDC)
) and an adjustment resistor 45 for electrically adjusting the positional deviation.
and a roller ring 42H for detecting the engine rotation angle, the position of missing teeth, and the engine rotation speed from the rotational displacement of the engine rotation speed pulser (hereinafter referred to as NE balsa) 42E fixed to the pump [1 shaft 42A]. A fixed engine speed sensor (for example, consisting of an electromagnetic pickup)
(hereinafter referred to as NE sensor) 46 and face cam 42
A roller ring 42I for reciprocating the F and plunger 42G and changing the timing thereof (and a timer piston 42J for changing the rotational position of the roller ring 42H (FIG. 2 shows a 90° unfolded state) ), a timing control valve (hereinafter referred to as TCV) 48 for controlling the injection timing by controlling the position of the timer piston 42J, and timing for releasing fuel from the plunger 42G via the spill boat 42K. an electromagnetic spill valve 49 for controlling the fuel injection amount by changing the fuel injection amount, and a fuel cut valve (hereinafter referred to as FCV) 50 for cutting fuel when the engine is stopped or abnormality occurs.
Delivery pulp 4 to prevent fuel backflow and after-effects
It is equipped with 2L. The intake pipe 51 and exhaust pipe 52 of the diesel engine 10 are
The two are connected to each other by an EGR passage 53 that communicates them. An EGR valve 54 for controlling EGRi is provided in the middle of the EGR passage 53. The EGR valve 4
The negative pressure applied to the diaphragm chamber is controlled by an electronic IT+ controlled negative pressure regulating valve (hereinafter referred to as EVRV) 55. The EVRV 55 is controlled by an on-off duty signal, and the control duty ratio Degr
increases, the current value of EVRV55 increases, and the EGR
The negative pressure in the diaphragm chamber of the valve 54 increases, causing EGR
The foothills are being increased. The intake temperature sensor 12, accelerator sensor 20, intake pressure sensor 32, ignition timing sensor 38, water temperature sensor 40, crank angle sensor 44, illll resistance 45E sensor 46
, key switch, air conditioner switch, neutral safety switch output, vehicle speed signal, etc. are input to an electronic control unit (hereinafter referred to as EC1J) and processed.
0. TCV48, electromagnetic spill valve 49, FCV50, EV
RV55 Kasa is controlled. The operation of the embodiment will be explained below. In this embodiment, the control of the fuel injection amount is based on the engine rotation speed NE detected from the output of the NE sensor 46, the accelerator opening degree ACCp detected from the output of the accelerator position sensor 20, etc. Calculate,
This is done by controlling the energization time of the electromagnetic spill valve 49 by 1tlll'. Further, the fuel injection timing is similarly controlled to the target value by calculating the target injection timing from the accelerator opening degree ACCp, engine speed NE, etc., and controlling the TCV 48 i'cIJ. . During idling, the engine speed correction jlNEi is performed to bring the engine speed to the desired idle speed using idle speed control (hereinafter referred to as ISO), which is well known in Japanese Patent Application Laid-Open No. 57-181940.
sc signal (Ne' in JP-A-57-181940)
), the electromagnetic spill valve 49 and TCV 48 are controlled. Further, control of EGRffi is executed according to a flowchart as shown in FIG. In this case, Figure (A) shows a routine for calculating the EGR control duty ratio Degr (%), and Figure (B) shows the ISO engine speed correction JtNEisc and its learning [rotation speed difference with NEo]. ΔNE
The routine for calculating is shown below. That is, in the EGR control routine shown in FIG. Step 1
At step 20, it is determined whether or not the engine operating state is in the idle state. If the determination result is negative, that is, the engine is not in the idle state, the process proceeds to step 160, and the control duty ratio DeQr is outputted as the current command value. On the other hand, if the determination result in step 120 is positive, that is, it is determined that the idle state is present, the process proceeds to step 130, where a dedicated EGR control duty ratio D1dle during idling is calculated.
The rotational speed difference Δ obtained by the rotational speed difference ΔNE calculation routine shown in
From NE (rpi), the current EGR correction duty ratio ΔEGR (%) is calculated by one-dimensional interpolation using, for example, the map shown in FIG. In this map, a dead zone of the corrected duty ratio ΔEGR with respect to NH is provided for the rotation speed difference, and in the case of the embodiment, this dead zone is defined as the correction duty ratio of EGR to O when the rotation speed difference ΔNE is 130 rpm or less. The scope is set as follows. Next, in step 150, the duty ratio D 1dte calculated in step 130 is calculated as shown in the following equation (1).
The value obtained by subtracting the corrected duty ratio ΔEGR from (%) is entered into the rrA duty ratio Degr. D egr +D 1dle-ΔEGR-・----(
1) Then, in step 160, the control duty ratio Da
(lr is output as a command value and EGRi is controlled by M. Also, when it is determined in the previous step 120 that the vehicle is not in idle mode, the process proceeds to step 160, and the previous control duty ratio Deg r is output. , the rotational speed difference ΔNE calculation routine shown in FIG. In this case, 1.5 seconds have elapsed since the idle switch was ON, and the accelerator opening degree A CCp
is 0%, the gear position is in the neutral range or drive range, the vehicle speed is Qk+s/hour, and the starter switch is turned off. When this determination result is positive, that is, it is determined that the idle is in a stable state, the process proceeds to step 220, and a 0 determination is made to determine whether or not the current engine rotation correction MNEisc is larger than the learned value NEn of the engine rotation correction amount up to the previous time. If the result is positive, the process proceeds to step 230, where the learned value NEm of the engine rotation correction amount is increased by one as shown in the following equation (2), and the process proceeds to step 240. NEn 4-NEn+1 ・・・・・・(2
) On the other hand, if the judgment result is negative, that is, engine rotation correction,
When 1NEisc is less than the learned value N E +, the process proceeds to step 240, and a value obtained by reducing the value of the engine speed correction amount NEisc by 4 as shown in the following equation (3) is set as a new learned value NEII of the engine speed correction amount. Update the learned value as . After updating, the process proceeds to step 250. NEn←NE11-4 ・・・・・・(3)
On the other hand, when the determination result in the previous step 210 is negative, that is, when it is determined that the idle state is not stable, step 25
Go to 0. In step 250, the calculated learning value NEm is subtracted from the engine rotation correction 1NEisc as shown in the following equation (4) to calculate and store the rotational speed difference ΔNE, and this routine is temporarily terminated in preparation for the next activation. ΔNE=NE isc −NE+e −−−−−
- (4) As described above, in the embodiment, the idle rotation speed correction, (lNEisc is the previous stored learning value NEi
If it is larger, increase this learning value NEI (step 230), and use the increased learning value NE1 (
4) is used to calculate the rotational speed difference ΔNE'jI: (step 240). Therefore, when the idle rotational speed correction NEisc''('EGR correction foot ΔEGR is determined, the variation in this correction 1NEisc) Affected, but setting?+tt Positive RNEisc learning value N E +e
″C is increased and decreased step by step (step 23
0.240>, the variation in the EGR correction foot can be reduced, the emission characteristics can be improved, and excessive application of EGH can be prevented, thereby preventing the occurrence of engine stall. In addition, in the above embodiment, the present invention is based on the electromagnetic spill valve 49.
However, the scope of application of the present invention is not limited to this, and is applicable to general electronically controlled diesel engines. The same can be applied to the engine as well. [Effects of the Invention] As explained above, according to the present invention, it is possible to easily detect from a change in the corrected rotation speed that a load is applied by an engine driven device at low rotation speeds, and to eliminate smoke and white smoke at that time. In addition, since EGR, Q dead zones are provided for the amount of change in the corrected rotation speed, emissions caused by variations in the characteristics of each engine or variations in operating conditions before reaching the idle state can be prevented. Variations can be reduced. Therefore, it is possible to correct the increase in the EGR load when a high load condition occurs at a predetermined low rotation speed, so that excellent effects such as prevention of engine stall can be obtained.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are flowcharts showing a routine for calculating the EGH limit of an electronically controlled diesel engine for automobiles in which the present invention is implemented, and Figure 2 shows the overall configuration of the diesel engine. FIG. 3 is a diagram showing an example of a map of the rotational speed difference and the correction duty ratio used in the routine. 10...Diesel engine, 20...Accelerator senna, ACCp...Accelerator opening degree, 46...NE sensor, NE...Engine speed, 55...1 bar control negative pressure regulating valve (EVRV),
56...Electronic control unit (ECU), Degr...
・EGR control duty ratio.

Claims (1)

[Claims] (1) In a diesel engine exhaust gas recirculation control method in which the engine speed is controlled to a predetermined value at low speeds and exhaust gas is recirculated even at low speeds, the engine speed is below the set value. At times, the exhaust gas recirculation amount is controlled in accordance with the amount of change in the corrected engine speed, provided that the corrected engine speed when controlling the engine speed to a predetermined value changes by a predetermined amount or more. Exhaust gas recirculation control method for diesel engines.