JPH0816465B2 - Exhaust gas recirculation control method for diesel engine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

TECHNICAL FIELD The present invention relates to an exhaust gas recirculation control method for a diesel engine, and more particularly to controlling an exhaust gas recirculation control amount for a diesel engine in which an actual injection timing of a fuel injection pump is controlled by a timer operated by a hydraulic actuator. The present invention relates to an improved exhaust gas recirculation control method for a diesel engine suitable for use in a diesel engine.

[Prior art]

Generally, in a diesel engine, fuel supplied to the combustion chamber is controlled by a fuel injection pump that is rotationally driven in synchronization with engine rotation.
That is, in the diesel engine, the fuel injection timing is controlled by operating the hydraulic timer provided in the fuel injection pump with the supply pressure from the feed pump to move the roller ring, and by the control lever. The fuel injection amount is controlled by moving the spill ring to change the end of pumping. On the other hand, in recent years, with the development of electronic control technology, particularly digital control technology, attempts have been made to electronically control the fuel injection amount of a diesel engine. An electronically controlled diesel engine using a solenoid valve spill system instead of the spill ring has been made. Is being studied experimentally. When the exhaust gas recirculation (hereinafter referred to as EGR) control is performed in the electronically controlled diesel engine with the solenoid valve spill system as described above, the EGR control amount is calculated from the two-dimensional map of the engine speed NE and the calculated injection amount. It is normal to decide
Further, regarding the fuel injection timing, for example, the applicant has described in JP-A-59
As shown in the -120778 publication, it is determined from the two-dimensional map of the engine speed and the calculated injection amount. Also,
When determining the EGR control amount and fuel injection timing, generally,
It is determined in consideration of the mutual influences of the EGR control amount and the fuel injection timing during engine steady operation. The emission contained in the exhaust gas is greatly affected by the fuel injection timing. However, in the fuel injection pump that controls the fuel injection timing with the hydraulic timer as described above. May cause a response delay during the engine transient operation, and the response delay may cause a difference between the target injection timing and the actual injection timing. As described above, conventionally, the EGR control amount is determined in consideration of the mutual influence of the EGR control amount and the fuel injection timing during the engine steady operation, but the EGR control amount is not determined in consideration of the difference. Therefore, there is a problem that the emission in the exhaust gas may deteriorate during the transient operation. As a technique related to the present invention, the applicant has already disclosed in JP-A-56-110536 that the fuel injection timing is set to the engine speed and the EG.
We have proposed a fuel injection timing control device for a diesel engine that is determined according to R. The fuel injection timing control device is configured to determine the fuel injection timing that is further advanced than the fuel injection timing determined based on the engine speed when exhaust gas recirculation is being performed. However, this fuel injection timing control device does not consider the response delay of the hydraulic timer, and is not a technique that can optimally control the EGR during engine transient operation. In addition, the applicant, in Japanese Utility Model Laid-Open No. 60-70747, discloses an injection timing detection device for a distribution type fuel injection pump that detects the advance angle of the injection timing based on the phase shift difference between the reference position sensor output and the injection start sensor output. is suggesting. In this injection timing detection device, the advance angle of the injection timing can be detected easily and accurately, but like the fuel injection timing control device, the EGR control amount during engine transient operation is optimally optimized. Not technology.

[Object of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and it is possible to obtain an EGR amount adapted to the actual injection timing even if the response delay of the timer of the fuel injection pump occurs during transient operation. Another object of the present invention is to provide a diesel engine EGR control method capable of optimally controlling the EGR in the entire operating range including the engine transient operation.

[Means for solving problems]

The present invention controls the actual injection timing of the fuel injection pump and the target injection timing when controlling the EGR amount of the diesel engine in which the actual injection timing is controlled by the timer provided in the fuel injection pump to be the target injection timing. By obtaining the difference and correcting the EGR amount according to the obtained difference, exhaust gas recirculation control is performed according to the difference between the actual injection timing and the target injection timing caused by the response delay. Thus, the above-mentioned object is achieved.

[Action]

In the present invention, when the EGR amount of the diesel engine is controlled, the difference between the actual injection timing of the fuel injection pump and the target injection timing is obtained, and the EGR amount is corrected according to the obtained difference. Therefore, even if the timer response is delayed during the transient operation and the actual injection timing is retarded or advanced from the target injection timing, the EGR amount suitable for the actual injection timing can be obtained. It is possible to optimally control the EGR amount and thus the EGR rate in the entire operating range including time. Therefore, the deterioration of the engine can be prevented and the acceleration can be improved without deteriorating the properties of the emission in the exhaust gas.

【Example】

Hereinafter, embodiments of the EGR control method for a diesel engine according to the present invention will be described in detail. In this embodiment, as shown in FIG.
An intake air temperature sensor 12 is provided downstream of 11 for detecting the temperature of intake air. The intake air temperature sensor 12
A turbocharger 14 including a turbine 14A that is rotated by the heat energy of the exhaust gas and a compressor 14B that is rotated in conjunction with the turbine 14A is provided downstream of the turbine. The upstream side of the turbine 14A of the turbocharger 14 and the downstream side of the compressor 14B are communicated with each other through a waste gate valve 15 for preventing an excessive rise in intake pressure. In the intake passage 16 on the downstream side of the compressor 14B, a main intake throttle which is adapted to move in a non-linear manner by moving with an accelerator pedal 17 arranged in the driver's seat for limiting the flow rate of intake air during idling. A valve 18 is provided. Opening of the accelerator pedal 17 (hereinafter referred to as accelerator opening)
Accp is detected by the accelerator opening 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. A negative pressure generated by a negative pressure pump (not shown) is supplied to the diaphragm device 24 via a negative pressure switching valve (hereinafter, referred to as VSV) 28 or 30. An intake pressure sensor 32 for detecting the pressure of intake air is provided downstream of the intake throttle valves 18 and 22. The cylinder head 10A of the diesel engine 10 has an injection nozzle 3 whose tip faces the engine combustion chamber 10B.
4, a glow plug 36 and an ignition timing sensor 38 are provided. Also, the cylinder block 10 of the diesel engine 10
C has a water temperature sensor 4 for detecting the engine cooling water temperature.
0 is provided. Fuel is injected from the injection pump 42 to the injection nozzle 34. The injection pump 42 has a diesel engine
A pump drive shaft 42A that is rotated in association with the rotation of the crankshaft 10 and a feed pump 42B fixed to the pump drive shaft 42A for pressurizing fuel (FIG. 2 shows a 90 ° expanded state). And a fuel pressure adjusting valve 42C for adjusting the fuel supply pressure and a rotational displacement of a pump drive shaft pulley 42D fixed to the pump drive shaft 42A to detect a crank angle reference position of the engine, for example, top dead center (TDC). A crank angle sensor 44 composed of, for example, an electromagnetic pickup, an adjusting resistor 45 for electrically adjusting the displacement of the mounting position of the crank angle sensor 44, and an engine speed fixed to the pump drive shaft 42A. Pulser (hereinafter referred to as NE pulser)
An engine speed sensor (hereinafter, referred to as NE sensor) 46, which is fixed to the roller ring 42H and includes, for example, an electromagnetic pick-up, for detecting the engine rotation angle, the tooth-missing position and the engine speed from the rotational displacement of 42E, and A roller ring 42H for reciprocating the face cam 42F and the plunger 42G and changing the timing thereof, and a timer piston 4 for changing the rotational position of the roller ring 42H.
2J (FIG. 2 shows a 90 ° deployed state) and a timing control valve (hereinafter referred to as TCV) 4 for controlling the injection timing by controlling the position of the timer piston 42J.
8 and an electromagnetic spill valve 49 for controlling the fuel injection amount by changing the fuel escape timing from the plunger 42G via the spill port 42K, and cutting the fuel when the engine is stopped or abnormal Fuel cut valve (hereinafter FC
(Referred to as V) 50 and a delivery valve 42L for preventing backflow of fuel and backward drip. The intake pipe 51 and the exhaust pipe 52 of the diesel engine 10 are connected by an EGR passage 53 that connects the two. In the middle of the EGR passage 53, an EGR valve 54 for controlling the EGR amount is provided. The negative pressure applied to the diaphragm chamber of the EGR valve 54 is an electronically controlled negative pressure adjusting valve (hereinafter, referred to as EVRV).
Controlled by 55. The EVRV55 is controlled by an ON-OFF duty signal, and the control duty ratio Degr
The current value of the EVRV 55 increases, and the negative pressure in the diaphragm chamber of the EGR valve 54 increases, so that the EGR amount increases. The intake air temperature sensor 12, accelerator opening sensor 20, intake pressure sensor 32, ignition timing sensor 38, water temperature sensor 40, crank angle sensor 44, adjustment resistor 45, NE sensor 46, key switch,
An air conditioner switch, a neutral safety switch output, a vehicle speed signal, and the like are input to an electronic control unit (hereinafter referred to as an ECU) 56 and processed, and the VSVs 28, 30, TCV48, electromagnetic spill, Valve 49, FCV50, E
VRV55 and the like are controlled. As shown in detail in FIG. 3, the ECU 56 includes a central processing unit (hereinafter, referred to as a CPU) 56A for performing various arithmetic processing, an output of the water temperature sensor 40 input via a buffer 56B, and a buffer 56C. The output of the intake air temperature sensor 12 input via the buffer 56D, the output of the intake pressure sensor 32 input via the buffer 56D, the output of the accelerator position sensor 20 input via the buffer 56E, and input via the buffer 56F. A multiplexer (hereinafter, referred to as MPX) 56H for sequentially taking in a phase (θ) correction voltage signal, a response (τ) correction voltage signal, etc. input via a buffer 56G;
Convert the analog signal of the MPX56H output to a digital signal
An analog-to-digital converter (hereinafter referred to as an A / D converter) 56J for taking in the CPU 56A, and a waveform shaping circuit 56K for shaping the output of the NE sensor 46 and taking in the CPU 56A.
The waveform of the output of the crank angle sensor 44 is shaped by the CPU 56A.
Waveform shaping circuit 56L for taking in, the waveform shaping circuit 56M for taking the waveform of the ignition timing sensor 38 into the CPU 56A by shaping the output, the buffer 56N for taking in the starter signal to the CPU 56A, and the air conditioning signal. A buffer 56P for taking in the CPU 56A, a buffer 56Q for taking in a torque converter signal to the CPU 56A, a drive circuit 56R for driving the FCV50 according to the calculation result of the CPU 56A, and a calculation result of the CPU 56A. Drive circuit 56S for driving the TCV48, a drive circuit 56T for driving the electromagnetic spill valve 49 according to the calculation result of the CPU 56A, and current detection for detecting the current of the electromagnetic spill valve 49. Circuit 56U and a low voltage circuit for detecting a low voltage applied to the electromagnetic spill valve 49.
56V and a drive circuit for outputting a self-diagnosis signal (hereinafter referred to as a diagnostic signal) according to the calculation result of the CPU 5A
56W and a drive circuit 56X for driving the EVRV 55 according to the calculation result of the CPU 56A. Here, the θ correction voltage signal is a signal for correcting the phase difference and the like between the normal position and the actual mounting position that occur when the crank angle sensor 44 is attached to the injection pump 42. Further, the τ correction voltage signal is a signal for correcting the responsiveness shift due to the individual difference of each component in the injection pump 42. The operation of the embodiment will be described below. The EGR control in this embodiment is executed according to the flowchart shown in FIG. The figure (A) is a main routine for calculating the difference ΔCA between the target ignition timing TRGca and the actual ignition timing ACTca, and the figure (B) is the calculated difference ΔCA.
EGR correction coefficient Degra is calculated from
This routine is for correcting the GR control duty ratio Degr, and FIG. 7C is an output conveyor IR for converting the calculated control duty ratio Degr into an external output signal.
It is a Q routine. In the main routine, first, step 110
Then, the engine speed NE is calculated based on the output signal of the NE sensor 46, and a pseudo accelerator opening Accpa is calculated in step 120. Next, at step 130, the fuel injection amount Qv is calculated based on the calculated engine speed NE, accelerator opening Accpa, and the like. Next, at step 140, the target injection timing TRG is calculated from the calculated engine speed NE, accelerator opening Accpa, etc.
Calculate ca. Then, in step 150, the combustion injection pump 4
Calculate the actual injection timing ACTca of 2. This actual injection timing ACTca
The calculation of is basically performed by detecting the position of the timer piston 42J. That is, the position of the timer piston 42J is, for example, the time T ₁ at the engine top dead center position detected by the crank angle sensor 44, the time T ₂ at any position on the pump drive shaft 42A detected by the NE sensor 46, and the engine rotation. Calculate from the number NE. In that case, the difference ΔT (= T ₁ between the times T ₁ and T ₂
-T ₂ ) is changed by the rotation of the timer piston 42J, and from the engine speed NE and the difference ΔT,
Further, the crank angle position from time T ₁ (top dead center) when the time T _2, can detect, sub connexion, the position of the timer piston 42J can be detected. Next, at step 160, the calculated target injection timing T
The difference Δca between RGca and the actual injection timing ACTca is calculated by the following equation (1), and this main routine is once ended. Δca ← TRGca-ACTca (1) Next, the control duty ratio Degr of EGR shown in FIG.
A routine for calculating is described. This routine is, for example, a routine that is started every 50 milliseconds, and when it is started, first in step 210, the target EGR is calculated from the engine speed NE and the fuel injection amount Qv calculated in the main routine.
The control duty ratio Degr that yields the rate is calculated. Next, at step 220, the EGR with respect to the delay from the target injection timing of the actual injection timing caused by the response delay of the timer piston 42J
In order to prevent the non-conformity of (3) and the influence on the emission in the exhaust gas, the correction coefficient Degra for correcting the EGR rate is calculated from the difference Δca between the target and the actual injection timing calculated in the main routine. The correction coefficient Degra can be calculated, for example, using a map of the correction coefficient Degra corresponding to the difference Δca as shown in the following table. Generally, if the injection timing is delayed, NOx in the exhaust gas
Decreases. Therefore, the actual injection timing ACTca is the target injection timing T
When it is delayed with respect to RGca, the injection timing is delayed, so the NOx has already decreased, and therefore the correction coefficient Degra is set to a value such that the target EGR rate is decreased. On the contrary, when the actual injection timing ACTca is ahead of the target injection timing TRGca, NOx is increasing because the engine is advancing, and accordingly, the correction coefficient Degra is set to a value such that the target EGR rate increases. To do. Next, at step 230, the control duty ratio Degr at which the calculated target EGR rate is obtained is multiplied by the correction coefficient Degra as in the following equation (2) to correct the EGR amount to optimize the EGR rate. Degr ← Degr × Degra (2) Next, in the output conveyor IRQ routine shown in FIG. 7C, EVRV55 corresponding to the corrected control duty ratio Degr calculated in the 50 millisecond routine.
By writing the energization signal of, and controlling the EVRV55 with the energization signal, the EGR amount becomes a value at which the target EGR rate can be obtained. In the above embodiment, the case where the present invention is applied to the electronically-controlled diesel engine having the configuration shown in FIGS. 2 and 3 has been illustrated, but the diesel engine to which the present invention is applied is shown in the drawings. The present invention is not limited to those described above, and it is possible to employ the present invention in a diesel engine having another configuration and perform optimum EGR control. Also, in this case, the EGR is executed by the routine of the flow chart as shown in FIG.
Although the control was performed, it is clear that the EGR can be controlled by a routine having another procedure as long as the routine adopts the present invention.

【The invention's effect】

As described above, according to the present invention, it is possible to obtain the EGR amount adapted to the actual injection timing even if the timer response delay occurs during the transient operation. Therefore, the EGR amount can be optimally controlled in the entire operating range including the engine transient operation, and the deterioration of the engine can be prevented and the acceleration can be improved without deteriorating the property of the emission in the exhaust gas. An excellent effect such as being able to be obtained can be obtained.

[Brief description of drawings]

1 (A) to 1 (C) are flow charts showing a routine for performing EGR control in an embodiment of the exhaust gas recirculation control method for a diesel engine according to the present invention, and FIG. 2 is applied to the embodiment. FIG. 3 is a block diagram showing the overall configuration of the electronically controlled diesel engine including a partial block diagram, and FIG. 3 is a block diagram showing the overall configuration of the electronically controlled unit in the electronically controlled diesel engine. 10 …… Diesel engine, 20 …… Accelerator opening sensor, Accp …… Accelerator opening, 42 …… Fuel injection pump, 42J …… Timer piston, 46 …… NE sensor, NE …… Engine speed, 53 …… EGR passage, 54 …… EGR valve, 55 …… Electronic control negative pressure regulating valve (EVRV), 56 …… Electronic control unit (ECU), Degr …… Control duty ratio, Degra …… Correction coefficient.

Claims (1)

[Claims] 1. When controlling the exhaust gas recirculation amount of a diesel engine in which a timer provided in a fuel injection pump controls the actual injection timing to be a target injection timing, the actual injection timing of the fuel injection pump is By calculating the difference between the target injection timings and correcting the exhaust gas recirculation amount according to the calculated difference, the exhaust gas recirculation corresponding to the difference between the actual injection timing and the target injection timing caused by the response delay A method for controlling exhaust gas recirculation of a diesel engine, which is characterized by performing control.