JPH079205B2 - Injection timing control method for diesel engine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention, the fuel injection timing of the diesel engine (hereinafter,
Ignition timing correction according to the difference between the target ignition timing and the detected ignition timing, which is particularly suitable for use in an electronically controlled diesel engine for an automobile equipped with an ignition timing sensor. The present invention relates to an improved injection timing control method for a diesel engine in which the injection timing is corrected by obtaining a term and guarding the ignition timing correction term with a guard value.

[Prior art]

During injection timing control for optimizing exhaust gas purification performance of a diesel engine, especially a diesel engine for automobiles, the position of a timer piston of an injection pump (hereinafter referred to as a timer position) is detected, and the detected timer position and engine operation are detected. A so-called timer position feed back control has been proposed in which the position of the timer piston is controlled by controlling the feed back of the timer control valve according to the difference from the target timer position obtained from the state. Further, in this timer position feed back control, as a means for solving the problems of injection timing deviation due to variations at the time of initial setting of the injection pump and injection timing deviation due to changes in atmospheric pressure, fuel properties, etc., JP-A-57-28842, Kaisho 58-25582,
In JP-A-58-192935, JP-A-59-153942, etc., an ignition timing sensor such as a fire sensor is installed in the combustion chamber, and the ignition timing in the combustion chamber by the ignition timing sensor (the timing when the combustion light rises due to ignition or The detected ignition timing (actual ignition timing) is adjusted to the target ignition timing determined by, for example, the engine speed and the accelerator opening by controlling the feedback control of the detection result of the timing when the pressure in the cylinder rises rapidly due to combustion. A so-called ignition timing feedback control for controlling the feedback control of the timer control valve has also been proposed. As a specific method for performing the ignition timing feedback control, the applicant has filed Japanese Patent Application No. 60-156649 (Japanese Patent Laid-Open No. 62-32247).
It is proposed that the ignition timing feedback control be performed and the ignition delay be learned in a specific engine operating region with a small variation in ignition detection, and that the learned value be used in the entire operating region. However, this method may cause overcorrection in a non-learning area, and therefore, in order to improve this, the applicant has set an upper limit on the correction value in Japanese Patent Application No. 61-56533 (JP-A-62-214252). We are proposing a method to deal with it

[Problems to be Solved by the Invention]

However, when the ignition delay is large, such as in highlands or immediately after cold start, it is not sufficient to use the same upper limit value as in normal time, and the advance angle is not sufficient and the advance angle is delayed and white smoke is generated. And engine vibration may increase. In order to solve such a problem, if the upper limit is set to a sufficient upper limit in high altitude or cold, on the contrary, when there is a delay in detection due to deterioration or breakage of the ignition timing sensor, there is a possibility that the ignition timing is advanced too much. Atsuta The present invention has been made to solve the above-mentioned conventional problems, and it is possible to set an appropriate limit value even at high altitude or during cold, and to widen the range that can be advanced by correcting ignition. An object of the present invention is to provide a method for controlling the injection timing of a diesel engine that can be used.

[Means for solving problems]

The present invention provides an injection timing of a diesel engine in which an ignition timing correction term is obtained according to a difference between a target ignition timing and a detected ignition timing, and the ignition timing is corrected by guarding the ignition timing correction term with a guard value. In the control method, as shown in the outline of FIG. 1, during low intake pressure or during cold,
The object is achieved by setting the guard value of the ignition timing correction term to a guard value on the more advanced side. Further, the limit value for the value on the advance side is only the upper limit value.

[Action]

In the present invention, when the ignition timing correction term is obtained according to the difference between the target ignition timing and the detected ignition timing, and the ignition timing correction is guarded by the guard value to correct the injection timing, at the time of low intake pressure or at the cold In the meantime, the guard value of the ignition timing correction term is set to the guard value on the more advanced side. Therefore, the range in which the ignition angle can be advanced is widened by the ignition correction, and it is possible to perform an appropriate injection timing control while ensuring a sufficient angle of advance even in a highland where the ignition delay is large or in cold weather. Therefore, problems such as generation of white smoke and increased engine vibration can be eliminated. On the other hand, in normal times, an unnecessary advance angle width is not provided, and even if extreme deterioration of the ignition timing sensor or glass breakage should occur, the advance angle will not be excessively advanced. Further, when the guard value which is the value on the advance angle side is only the upper limit value, the effect of the present invention can be easily obtained.

【Example】

An embodiment of an electronically controlled diesel engine for an automobile, in which an injection timing control method according to the present invention is adopted, will be described in detail below with reference to the drawings. In this embodiment, as shown in FIG. 2, an intake air temperature sensor 12 is provided downstream of an air cleaner (not shown) for detecting the temperature of intake air. Downstream of the intake air temperature sensor 12, a turbocharger 14 including a turbine 14A that is rotated by the thermal energy of exhaust gas and a compressor 14B that is rotated in conjunction with the turbine 14A is provided. 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. The bench lily 16 on the downstream side of the compressor 14B has a main intake air intake that is configured to rotate in a non-linear manner in conjunction with an accelerator pedal 17 provided in a driver seat for limiting the flow rate of intake air at the time of idling. A throttle valve 18 is provided. The opening of the accelerator pedal 17 (hereinafter referred to as the accelerator opening) Accp is detected by an accelerator position sensor 20. An auxiliary intake throttle valve 22 is provided in parallel with the main intake throttle valve 18, and the opening degree of the auxiliary intake throttle valve 22 is a diaphragm device.
Controlled by 24. Negative pressure generated by the negative pressure pump 26 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, 22. The cylinder head 10A of the diesel engine 10 has an injection nozzle 3 whose tip faces the engine combustion chamber 10B.
4, the glow plug 36 and the ignition timing sensor 28 are provided. A glow current is supplied to the glow plug 36 via a glow relay 37. Further, the cylinder block 10C of the diesel engine 10 is provided with a water temperature sensor 40 for detecting the engine cooling water temperature. Fuel is pumped from the injection pump 42 to the injection nozzle 34. The injection pump 42 includes a diesel engine 10
Pump drive shaft that rotates in conjunction with the rotation of the crank wheel
42A, a feed pump 42B fixed to the pump drive shaft 42A for pressurizing the fuel (FIG. 2 shows a state in which the fuel is expanded by 90 °), and a fuel pressure adjusting valve for adjusting the fuel supply pressure.
42C, and a reference position sensor 44, such as an electromagnetic pick-up, for detecting a crank angle reference position, for example, top dead center (TDC) from the rotational displacement of the pump drive pulley 42D fixed to the pump drive shaft 42A. Pump drive shaft 42
Gear 42E fixed to A and having missing teeth corresponding to the number of cylinders
In order to detect the engine rotation angle and the tooth-missing position from the rotational displacement of, the engine rotation sensor 46, which is provided on the roller ring 42H and is made of, for example, an electromagnetic pickup, reciprocates the face cam 42F and the plunger 42G, and also A roller ring 42H for changing the timing, a timer piston 42J for changing the rotational position of the roller ring 42H (FIG. 2 shows a 90 ° expanded state), and a position of the timer piston 42J The timing control valve (hereinafter referred to as TCV) 48 for controlling the injection timing by doing so, and the plunger 42G through the spill port 42K.
The electromagnetic spill valve 50 for controlling the fuel injection amount by changing the fuel escape timing from the fuel, the fuel cut valve 52 for cutting the fuel, and the delivery for preventing the backflow and the backward droop of the fuel. And a valve 42L. The ignition timing sensor 38, as shown in detail in FIG.
A cylindrical case 38A that is inserted and fixed in the cylinder head 10A of the diesel engine 10, and a light guide 38B made of, for example, quartz glass for transmitting combustion light, which is inserted in the central portion of the case 38A, and the light. A light receiving element 38C made of, for example, a silicon photodiode is provided for detecting the light transmitted by the conductor 38B and converting the light into an electric signal. Intake temperature sensor 12, accelerator position sensor 20, intake pressure sensor 32, ignition timing sensor 38, water temperature sensor 40, reference position sensor 44, engine rotation sensor 46, glow current sensor 54 for detecting 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 input to an electronic control unit (hereinafter referred to as an ECU) 56 for processing, and the VSV 28, 30, the glow signal is output by the ECU 56. Relay 37, TCV4
8. The electromagnetic spill valve 50, the fuel cut valve 52, etc. are controlled. As shown in detail in FIG. 4, the ECU 56 has a central processing unit (hereinafter referred to as CPU) 5 for performing various arithmetic processes.
6A, a read-only memory (hereinafter referred to as ROM) 56B for storing a control program, various data, and the like, and a random access memory (hereinafter referred to as RAM) for temporarily storing operation data and the like in the CPU 56A. ) 56C
, A clock 56D that generates a clock signal, and a buffer 5
Output of the water temperature sensor 40 input via 6E, buffer
The intake air temperature sensor 12 output input via 56F, the intake pressure sensor 32 output input via a buffer 56G,
A multiplexer for sequentially fetching the output of the accelerator position sensor 20 and the like input via the buffer 56H (hereinafter,
MPX) 56K, an analog-to-digital converter (hereinafter referred to as an A / D converter) 56L for converting an analog signal of the MPX 56K output into a digital signal, and the A / D converter 56L output to the CPU 56A. I / O port 56M for input to the air conditioner, a starter signal input via the buffer 56N, an air conditioner signal input from the air conditioner via the buffer 56P, and a torque converter input from the automatic transmission via the buffer 56Q. Input / output port 56 for taking in the signal, the output of the ignition timing sensor 38, etc. input via the waveform shaping circuit 56R to the CPU 56A
S and waveform of the ignition timing sensor 38 output is shaped into the CPU
The waveform shaping circuit 56R for directly capturing to the input interrupt port ICAP2 of 56A, and the waveform shaping circuit 56T for waveform shaping the output of the reference position sensor 44 and directly capturing to the same input interrupt port ICAP2 of the CPU 56A, A waveform shaping circuit 56U for waveform shaping the output of the engine circuit sensor 46 and directly taking it into the input interrupt port ICAP1 of the CPU 56A, and the CP
A drive circuit 56V for driving the electromagnetic spill valve 50 according to the calculation result of U56A, a drive circuit 56W for driving the TCV 48 according to the calculation result of the CPU 56A, and the CPU 56A
A drive circuit 56X for driving the fuel cut valve 52 in accordance with the calculation result of 1. and a common bus 56Y for connecting the respective constituent devices to transfer data and commands. Here, the ignition signal of the waveform shaping circuit 56R output is
Not only the input interrupt port ICAP2 of A, but also the input / output port 56
The signal is also input to S in order to distinguish it from the reference position signal output from the waveform shaping circuit 56T which is input to the same input interrupt port ICAP2. The operation of the embodiment will be described below. The control of the injection timing in this embodiment is executed according to the flow charts shown in FIGS. 5 and 7. That is, in order to perform the feed back control of the injection timing with respect to the crank angle, the routine shown in FIG. 5 is executed every predetermined time, for example, every 50 milliseconds. In this 50 millisecond routine, first, step 110 is entered, and the basic (target) injection timing CAbase is obtained by searching, for example, a map of the engine speed NE and the accelerator opening Accp. Next, at step 120, a map showing the relationship between the accelerator opening Accp and the upper limit GIGm which is the guard value of the ignition timing correction term (learning term) GIG, as shown by the solid line A in FIG. 6, is opened. Search by Accp. Next, at step 130, it is judged if the ignition timing correction term GIG is positive. If the judgment result is positive, step 14
Proceeding to 0, it is determined whether the intake pressure Pim is a set value, for example, a low intake pressure of less than 500 mmhg, or the engine cooling water temperature THW is a set value, for example, a cold state of less than 40 ° C. If the result of any of the determinations in step 140 is positive and it is determined that the altitude is high or cold, step 15
At 0, the ignition timing correction upper limit value GIGm is a predetermined value, for example, 6 ° C A
Is added to the new ignition timing correction upper limit value GIGm.
Therefore, the ignition timing correction upper limit value GIGm in this case is
As shown by the solid line C in FIG. 6 above. Step 150
After the end or when the determination result of the above-mentioned step 140 is negative, the process proceeds to step 160, the ignition timing correction term GIG is compared with the ignition timing correction upper limit value GIGm at that time, and the smaller value is set to the ignition timing. It is stored as the learning value GIGa of the correction term.
Next, in step 170, the sum of the basic injection timing CAbase and the ignition timing correction learning value GIGa is calculated as shown in the following equation,
Included in the target injection timing TRGca for the crank angle. TRGca ← CAbase + GIGa (1) On the other hand, when the result of the determination in the above-mentioned step 130 is negative and the value of the ignition timing correction term GIG is negative, after the determination of the sign of the ignition timing correction term GIG in step 180 , Step 190 and
At 200, the inverse calculations of steps 160 and 170, respectively, are performed. That is, in step 190, contrary to step 160, the larger value of the ignition timing correction term GIG and the upper limit GIGm is set to the learning value GIG.
Put in IGa. Further, in step 200, contrary to step 170, the difference obtained by subtracting the learning value GIGa from the basic injection timing GAbase is added to the target injection timing TRGca. Therefore, the ignition timing correction lower limit value is as shown by the solid line B in FIG. After the end of step 170 or 200, the process proceeds to step 210, from the target injection timing TRGca, as shown in the following formula, the tooth-missing position detected by the engine rotation sensor 46 and the reference position detected by the reference position sensor 44 The inclination angle is calculated and the calculated actual injection timing ACTca is subtracted from this to calculate the difference ΔCA between the two. ΔCA ← TRGca−ACTca (2) Next, at step 220, an integral term ΔDi and a proportional term Dp for duty-controlling the TCV 48 are calculated from the injection timing difference ΔCA. Next, at step 230, the integral term ΔDi and the proportional term Dp are added to and subtracted from the control duty ratio Di at that time, as shown in the following equation, the final duty ratio Duty is calculated, and this routine is ended. Duty = Di ± ΔDi ± Dp (3) On the other hand, the calculation of the ignition timing correction term GIG is executed by a routine that is performed every second as shown in FIG. 7, for example. That is, the step 210 is performed every predetermined time, for example, every second.
Then, it is determined whether or not the start signal STA is on. If the determination result is negative, the process proceeds to step 212, and it is determined whether or not the accelerator opening Accp is a set value, for example, 16% or less. When the determination result is positive, the routine proceeds to step 214, where it is determined whether or not the injection amount Q is a set value, for example, 5 mm ³ / st or more. When the determination result of the above-mentioned step 210 is positive and the start signal is ON,
The result of the determination in step 212 above is negative, and the accelerator opening A
When ccp is more than 16%, or when the determination result of the above-mentioned step 214 is negative and the injection amount Q is less than 5 mm ³ / st, the calculation condition of the ignition timing correction term GIG is not satisfied. So I leave this routine. On the other hand, the determination result of the above step 210 is negative, and
If the determination results of steps 212 and 214 are both positive, and it is determined that the ignition timing correction term GIG should be calculated, the process proceeds to step 216, for example, the engine speed NE and accelerator opening Accp map. The target ignition timing TRGig is calculated by searching for. Then step 2
Proceeding to 18, the difference ΔGIG between the actual ignition timing ACTig and the target ignition timing TRGig is calculated as shown in the following equation. ΔGIG ← ACTig-TRGig (4) Next, in step 220, the difference ΔGIG in the ignition timing is calculated, for example.
As shown in the following equation, 1/8 is the ignition timing correction term GIG at that time.
Is added to the new ignition timing correction term GIG. GIG ← GIG + (1/8) ΔGIG (5) In this embodiment, the ignition timing correction limit value is set to the same absolute value (GIGm) on the advance side and the retard side, and at the time of low intake pressure or cold. Only, since the upper limit value is moved to the advance side, it is easy to set the ignition timing correction limit value. The method of setting the lower limit value for ignition timing correction is not limited to this.For example, the ignition timing correction upper limit value and the lower limit value may be different absolute values, or the ignition timing correction upper limit value may be set when the intake pressure is low or cold. Not only this, but the lower limit value can also be configured to move to the advance side. Further, in the present embodiment, the ignition timing correction upper limit value during normal operation is uniformly set when the intake pressure is low or when it is cold.
The upper limit value can be easily changed because the temperature is moved toward the advance side by only ° C. The method of setting the ignition timing correction upper limit value at the time of cold or low intake pressure is not limited to this, and it has a common map different from normal time, or at the time of cold and low intake pressure. It is also possible to have different independent maps.

【The invention's effect】

As described above, according to the present invention, it is possible to secure a sufficient advance angle even in a highland where the ignition delay is large or during cold conditions, and prevent problems such as generation of white smoke and engine vibration. On the other hand, in normal times, it does not have an unnecessary advance angle width, and even in the unlikely event of extreme deterioration of the ignition timing sensor or glass breakage, it has the excellent effect of not being controlled to the advance angle side. Have.

[Brief description of drawings]

FIG. 1 is a flow chart showing the outline of the injection timing control method for a diesel engine according to the present invention, and FIG. 2 is a partial block diagram showing the overall configuration of an embodiment of an electronically controlled diesel engine for an automobile to which the present invention is applied. Fig. 3 is a sectional view showing a diagram, Fig. 3 is a block diagram showing the constitution of the ignition timing sensor used in the above-mentioned embodiment, and Fig. 4 is a block diagram showing the constitution of the electronic control unit. FIG. 6 is a flow chart showing a 50 mm second routine for similarly performing crank angle feed back control, FIG. 6 is a diagram showing an example of an ignition timing correction range used in the 50 mm second routine, and FIG.
It is a flowchart which similarly shows a 1 second routine for calculating an ignition timing correction term. 10 ... Diesel engine, 20 ... Accelerator position sensor, Ac
cp ... Accelerator opening, 32 ... Intake pressure sensor, Pim ... Intake pressure, 3
8 ... Ignition timing sensor, 42 ... Injection pump, 40 ... Water temperature sensor, THW ... Engine cooling water temperature, 42j ... Timer piston, 44
… Reference position sensor, 46… Engine speed sensor, NE… Engine speed, 48… Timing control valve (TCV), 56… Electronic control unit (ECU), GIG… Ignition timing correction term, GIGm… Ignition timing correction upper limit, GIGa ... Ignition timing correction learning value, TRGig
… Target ignition timing, ACTig… Detected (actual) ignition timing, Duty…
Control duty ratio.

Claims (2)

[Claims] 1. A fuel for a diesel engine, wherein an ignition timing correction term is obtained according to a difference between a target ignition timing and a detected ignition timing, and the ignition timing is corrected by guarding the ignition timing correction term with a guard value. In the injection timing control method, the guard value of the ignition timing correction term is set to a guard value on the more advanced side when the intake pressure is low or when the engine is cold. 2. A fuel injection timing control method for a diesel engine according to claim 1, wherein a guard value which is a value on the advance side is only an upper limit value.