JPS62210242A - Fuel injection timing control method for diesel engine - Google Patents

Abstract

PURPOSE:To prevent a lead angle in a fuel injection timing due to decrease in nozzle opening pressure with time by computing a correction value for the fuel injection timing based on change in a control value for idle engine speed. CONSTITUTION:An engine control device 56 receives signals on engine speed, the opening of an accelerator, cooling water temperature and the like from sensors 46, 20, 40, and the like for computing a command value for a basic fuel injection timing for this time. Subsequently, it computes a fuel injection quantity in order to assume a control to a target idle engine speed at the time of idling, that is, it computes an ICS control value for the valve opening time of an injection nozzle 34. And the ICS control value for a stable idle engine speed condition is stored for computing a correction value for the injection timing for this time based on the difference from the value stored for the first time whereby reducing the latest correction quantity from the injection timing command value in order to obtain an injection timing command value for this time. Owing to this constitution, a lead angle in the fuel injection timing due to decrease in nozzle opening pressure with time can be prevented for restraining knocking so as to attempt an reduction in NOX.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a fuel injection timing control method for a diesel engine, and is particularly suitable for use in an electronically controlled diesel engine. The present invention relates to a fuel injection timing control method for a diesel engine in which idle rotation speed control is performed to control m, and fuel injection timing is controlled in accordance with engine operating conditions.

[Conventional technology]

When controlling the fuel injection timing to optimize the exhaust gas purification performance of diesel engines, especially automotive diesel engines, the position of the timer piston of the fuel injection pump (hereinafter referred to as timer position) is detected and the detected timer position is A so-called timer position feedback control has been proposed in which a timer control valve that controls the position of the timer piston is feedback-controlled according to the difference between the target timer position and the target timer position determined from the engine operating state.

[Problems to be solved by the invention]

However, in the conventional fuel injection timing control device that performs timer position feedback control as described above, the valve opening pressure decreases due to deterioration of the injection nozzle, and the actual fuel injection timing shifts, resulting in fuel injection. Feedback control to correct the timing advance was not performed. Therefore, if the fuel injection timing shifts to the advance side, the knocking noise of the engine becomes louder, and NOx contained in exhaust gas, etc. However, there was a problem in that the amount of products contained increased. It is also possible to deal with such problems by using ignition timing feedback control. However, this device that performs ignition timing feedback control requires an ignition timing sensor, making its configuration complicated.
Furthermore, if the injection timing is overadvanced, the burden of feedback control to correct it becomes heavy. On the other hand, a fuel injection timing control device that does not perform such ignition timing feedback control has a problem in that it cannot prevent overadvancing of the fuel injection timing.

OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is capable of obtaining specific fuel injection timing by responding to static changes in nozzle valve opening pressure with good viscosity. The purpose of the present invention is to provide a fuel injection timing control method for a diesel engine that is possible.

[Means to solve the problem]

The present invention provides a diesel engine in which idle speed control is performed to control the fuel injection timing in order to set the engine speed to a target speed during idling, and the fuel injection timing is controlled according to the engine operating state. In the fuel injection timing control method, as shown in FIG. 1, a change value of the control value of the idle rotation speed control is calculated, a correction value of the fuel injection timing is calculated from the calculated change mother,
The purpose of 1) h2 is achieved by correcting the fuel injection timing using the calculated correction value.

[Effect]

Hereinafter, the effects of the present invention will be explained. When a diesel engine is operated, the deterioration of the injection nozzle progresses over time, and its valve opening pressure decreases, causing the actual injection date to advance and NO in the exhaust gas to increase.
X, etc. will increase.Inventors and engineers have devised the idea of using the control value when performing idle rotation speed control (idle speed control) as a means of calculating such a decrease in the nozzle opening pressure. Ta. That is, as soon as the nozzle opening pressure decreases, the actual injection C and J timings advance and the actual injection blades immediately increase. 1) In the idle rotation fault control described below, this actual injection O
In order to prevent the idle speed from increasing due to an increase in jm, the fuel injection peak is controlled and decreased to keep the idle speed at a predetermined number. The present invention calculates the amount of change in the control value at the time of fuel injection, roughly estimates the amount of decrease in valve opening pressure, and corrects the injection timing to the retarded side accordingly. Therefore, it is possible to reliably correct and prevent errors in the n period of fuel injection caused by a decrease in the nozzle opening pressure. Therefore,
It is possible to prevent an increase in engine knocking noise and an increase in NOx in exhaust gas, which occur as the injection timing advances. (Example) Hereinafter, an electronically controlled diesel engine for automobiles in which the fuel injection timing control method for a diesel engine according to the present invention is implemented will be described in detail. An intake air temperature sensor 12 is provided downstream of the intake air temperature sensor 12 for detecting ?HIα of the intake air (not shown). A turbocharger 14 including a turbine 14A and a compressor 14B rotated in conjunction with the turbine 14A is provided.The turbocharger 14
The upstream side of the turbine 14Δ and the downstream side of the compressor 14B are communicated via a wastegate valve 15 for preventing an excessive rise in intake pressure. 1) The venturi 1G downstream of the compressor 14B is equipped with a
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. The opening degree of the accelerator pedal 17 (hereinafter referred to as the accelerator opening degree) A (Cp is the accelerator position sensor 2
0 has been detected. 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 26 is supplied to the diaphragm device 24 via a negative pressure switching valve (hereinafter referred to as VS) 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 10C of the diesel engine 10 includes a water temperature sensor +J for detecting the engine cooling water temperature. O is provided. 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 Deep Pill engine 10, and a feed pump 42B (a second pump) fixed to the pump drive shaft 42A for pressurizing fuel. Figure 2 does not show the 90° unfolded state (f)), a fuel pressure adjustment valve 420 for adjusting the fuel supply pressure, and the pump drive shaft 42.
The same reference position sensor 44 (fixed to the pump drive shaft 42A), which is composed of, for example, an electromagnetic pickup, is used to detect the crank angle reference position, for example, top dead center (TDC), from the rotational displacement of the pump drive pulley 42D fixed to A. was done,
An engine rotation sensor 46 consisting of, for example, an electromagnetic pickup provided on the roller ring 42H and a face cam 4
A roller ring 42H for reciprocating the 2F and plunger 42G and changing the timing thereof, and a timer piston 42J for changing the rotational position of the roller ring 42H (Figure 2 shows the 90° unfolded state). ) and a timing control valve (hereinafter referred to as
(referred to as TCV) 48, an electromagnetic spill valve 50 for controlling the fuel injection source by changing the timing of releasing fuel from the plunger 42G via the spill port 42K, and a fuel cut valve for cutting the fuel. 52 and
A pilot injection device 53 for controlling the fuel injection rate during pilot injection, and a delivery valve 42L for preventing fuel backflow and rearward slippage are provided. A glow current is supplied to the glow plug 36 via a glow relay 37. The intake temperature sensor 12, the accelerator position sensor 20, the intake pressure sensor 32, the ignition timing sensor 38, the water temperature sensor 40.
! A quasi-position sensor 44, an engine rotation sensor 46, a glow current sensor 54 that detects the glow current flowing through the glow plug 36, a key switch, an air conditioner switch, a neutral safety switch output, a vehicle speed signal, etc. are controlled by an electronic control unit (hereinafter referred to as ECU). ) 56 and processed by the output of the ECLJ 56.
V28.30, G C1-'JL/-37, TCV48,
The electromagnetic spill valve 50, fuel cut valve 52, etc. are controlled. The ECU 36, as not shown in detail in FIG.
A central processing unit (hereinafter referred to as C
(referred to as PU) 56A, and a read-only memory (referred to as RO) for storing control program and various data.
A random access memory (hereinafter referred to as RAM) 56C for temporarily storing calculation data etc. in the CPU 56A, a clock 560 that generates a clock signal, and a buffer 56E. the output of the water temperature sensor 40, the output of the intake air temperature sensor 12 that is input via a buffer 56F, the output of the intake pressure sensor 32 that is input via a buffer 56G,
A multiplexer (hereinafter referred to as MPX) 561 for sequentially taking in the outputs of the accelerator position sensor 20 etc. inputted through a buffer 56H, and an analog multiplexer (hereinafter referred to as MPX) for converting the analog signal output to the MPX 56 into a digital signal. Digital converter (hereinafter referred to as A/D converter) 5
6L, an input/output port 56M for taking the output of the A/D converter 56L into the CPU 56A, a starter signal inputted via the buffer 56N, an air conditioner signal inputted via the buffer 56P, and an input/output port 56M used to input the output of the A/D converter 56L to the CPU 56A. an input/output port 568 for inputting the torque converter signal input through the CPU 56A, the output of the ignition timing sensor 38 inputted via the waveform shaping circuit 56R, etc.; The waveform shaping circuit 56R directly inputs the input interrupt baud 1 to ICAP2 of the CPU 56A, and the waveform shaping circuit 56R shapes the output of the reference position sensor 44 to input the same input interrupt baud MCAP2 of the CPU 56A.
a waveform shaping circuit 2856T for directly inputting the output to the CPU 56;
A waveform shaping circuit 56U for directly capturing the input interrupt baud I-ICAP1, a drive circuit 56V for driving the electromagnetic spill valve 50 according to the calculation result of the CPtJ 56A, and a calculation result of the CPU 56A. drive circuits 56 to 5 for driving the TCV 48 according to the calculation result of the CPU 56A;
a drive circuit 56X for driving CPtJ5; and a drive circuit 56X for driving CPtJ5.
A drive circuit 56Y for driving the pilot injection device 53 according to the calculation result of 6△, and a common bus 5 for connecting each component to transfer data and general information.
It is composed of 6Z. Here, the ignition signal of the waveform shaping circuit 56R output is
What is input not only to the input interrupt port ICAP2 of the CPU 56A but also to the input/output port 563 is the waveform shaping circuit 5 that is input to the same input interrupt ports 1 to ICAP2.
This is to distinguish it from the reference position signal of the 6T output. The effects of the embodiment will be explained below. Control of fuel injection timing in this embodiment is executed according to a flowchart as shown in FIG. That is, in step 100, the engine rotation is ff1Ne. The accelerator pressure [Accp], engine water WTHW, air conditioner signal and other signals are taken in, and in step 110, the current basic fuel injection timing command value is outputted. Then,
In step 120, it is determined whether the engine is in an idle state. If the determination result is positive, that is, the engine is in an idle state, the process proceeds to step 130, and based on the signal acquired in step 100, the fuel injection 04 required to control the engine speed to the desired idle speed is performed. A control value for the valve opening time of the injection nozzle 34 (hereinafter referred to as an ISO control value) required to obtain the calculated fuel injection DI a is calculated. Next, in step 140, it is determined whether or not the weight conditions for injection timing correction have been met. In the case of the example, this calculation condition is based on the diesel engine 10
is completely warmed up, the transmission gear is in neutral, the air conditioner is off, and no large electrical loads (headlights, defogger, etc.) are in use, and all conditions are met that the change in idle speed is within 2 Q rpm. This is when a stable condition continues for 20 seconds or more. As a result, an appropriate SC control value can be stored and erroneous correction of fuel injection timing can be prevented. If the determination result in step 140 is positive, that is, the injection opening correction m
If the calculation condition is satisfied, the process proceeds to step 150, and it is determined whether this is the first time the process has proceeded to this step. If the determination result is positive, that is, if it is the first time to execute this step due to the condition for outputting the corrected mi, the process proceeds to step 180, and the current ISO control value is stored as a reference value for calculating the fuel injection timing. On the other hand, if the determination result in step 150 is negative, that is, this step is being executed for the second time or later, the process proceeds to step 160, in which the current ISO control value calculated in step 130 and the ISO control value stored in step 180 for the first time are used. The difference between the value and the reference value is calculated as 4, as shown by the symbol A in FIG. Then, from this value, the correction history of the current injection timing (sign AM in Fig. 5 is calculated from the relationship as shown in Fig. 6), and this is stored and updated as the new correction date. The slope of the graph showing the relationship between the correction ratios in FIG. 6 varies depending on the μmF characteristics of the injection nozzle 34 used, the cam profile of the injection pump 42 used, etc. Next, The process proceeds to step 170.Also, after step 180 is executed, if the determination results in step 120 and step 140 are negative, the process proceeds to step 170.In this step 170, from the calculated injection aj timing command value to the previous The latest correction amount calculated and updated is subtracted as indicated by the symbol A' in Fig. 5 to obtain the current injection timing command value.As described above, in step 160, the ISO control value Correct the injection timing command value from the difference between the first time and the second time.
<Symbol A- in the figure) is determined and reflected in the injection synchronization in step 170, so that the injection timing command value is corrected to an appropriate value as shown in the figure, and the actual injection timing indicated by the symbol B in the figure is corrected. The lead angle is corrected. Therefore, over-advancing of the injection timing due to a drop in valve opening pressure can be prevented, and NOX in the exhaust gas, engine vibration, and noise can be prevented. In the above embodiment, the correction calculation graph shown in FIG. 4 and FIG.
The amount of correction for the injection timing command value was determined using the SO control value. However, the procedure and graph for calculating the correction amount are not limited to those shown in FIGS. 4 and 6, and other procedures and graphs may be used. In that case, a graph can be used that depends on individual conditions, such as the μmF characteristics of the injection nozzle and the cam profile of the injection pump used. Further, in the above embodiment, the amount of change in the control value of the idle rotation speed $ control is calculated using the initial control value as a reference point, but the calculation method is not limited to this, and other methods may be used. The amount of change can be calculated using the following method. Further, in the above embodiment, the present invention provides an electromagnetic spill valve 50.
The fuel injection is controlled by the pilot 1IIJ.
However, the scope of application of the present invention is not limited to this, and is applicable to fuel injection control acticoators other than electromagnetic spill valves. It is clear that the present invention can be similarly applied to a general diesel engine equipped with the following.

【Effect of the invention】

As explained above, according to the present invention, it is possible to prevent the fuel injection timing from advancing due to the temporal decrease in the nozzle valve pressure <k. Therefore, for example, even if the injection nozzle deteriorates over time and the valve opening pressure increases, it can be accurately corrected, and vibrations such as diesel engine knock noise caused by overadvancing the injection timing due to the increase in valve opening pressure. It has excellent effects such as being able to prevent noise and reduce NOx in exhaust gas.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the present invention, and FIG. 2 is a cross-sectional view including a partial block diagram showing the overall configuration of an embodiment of an electronically controlled diesel engine for automobiles in which the present invention is adopted. 3 is a block diagram showing the configuration of the electronic control unit, FIG. 4 is a flowchart showing a routine for controlling the fuel injection timing, and FIG. 5 is a block diagram showing the configuration of the electronic control unit.
FIG. 6 is a line diagram showing an example of a command value for controlling the fuel injection timing. It is a diagram. DESCRIPTION OF SYMBOLS 10... Diesel engine, 20... Accelerator position sensor, A ccp... Accelerator opening degree, 38... Ignition timing sensor, 42... Injection pump, 42J... Timer piston, 44... Reference position sensor, 46... Engine rotation sensor, NE... Engine rotation speed, 48... Timing control valve (TCV), 56... Electronic control unit (ECU).

Claims (1)

[Claims] (1) Diesel engine fuel injection timing control that controls the fuel injection amount in order to set the engine rotation speed to the target rotation speed during idle, and also controls the fuel injection timing according to the engine operating state. The method is characterized by: calculating an amount of change in the control value of the idle rotation speed control; calculating a correction value for fuel injection timing from the calculated amount of change; and correcting the fuel injection timing using the calculated correction value. A fuel injection timing control method for a diesel engine.