JPH0665857B2 - Fuel injection timing control method for diesel engine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a fuel injection timing control method for a diesel engine, and more particularly to an idle speed that is suitable for use in an electronically controlled diesel engine and that controls the fuel injection amount to set the engine speed as a target speed during idle. The present invention relates to a fuel injection timing control method for a diesel engine that controls the fuel injection timing according to the engine operating state.

[Prior art]

During fuel 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 a fuel injection pump (hereinafter referred to as a timer position) is detected, and the detected timer position is detected. A so-called timer position feed back control has been proposed in which the feed back control is performed on the timer control valve that controls the position of the timer piston according to the difference from the target timer position obtained from the engine operating state.

[Problems to be Solved by the Invention]

However, in the fuel injection timing control device in which the conventional timer position feedback control is performed as described above, the valve opening pressure decreases due to the deterioration of the injection nozzle, and the actual fuel injection timing shifts. The feedback control for correcting the advance of the fuel injection timing has not been performed. Therefore, when the fuel injection timing is shifted to the advance side, there is a problem that the knocking noise of the engine becomes loud and the content of NOx and the like contained in the exhaust gas increases. It is possible to deal with such a problem by the ignition timing feedback control. However, since the ignition timing feedback control device requires an ignition timing sensor, its configuration becomes complicated,
Further, if the injection timing is advanced too much, the load of the feedback control amount for correcting it will be heavy. On the other hand, such a fuel injection timing control device that does not perform ignition timing feedback control has a problem that it is not possible to prevent an excessive advance 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 a fuel injection for a diesel engine capable of accurately obtaining a specific fuel injection timing by accurately responding to a change over time of the nozzle opening pressure. An object is to provide a timing control method.

[Means for solving problems]

The present invention uses an injection nozzle that injects fuel into the engine combustion chamber when the fuel pressure becomes equal to or higher than the valve opening pressure, and further, at the time of idling, feedback control according to the difference between the target engine speed and the actual engine speed. The fuel injection amount is controlled by the feed back control amount so that the actual engine speed matches the target engine speed.
In a fuel injection timing control method for a diesel engine for controlling a fuel injection timing according to an engine operating state, an actual fuel injection amount is in an increasing direction from a change amount of the feed back control amount for decreasing the fuel injection amount. When it is determined that the fuel injection timing is in the increasing direction, the correction value of the fuel injection timing is calculated from the change amount of the feedback control amount as the decrease of the valve opening pressure, and the calculated correction value The above object is achieved by correcting the fuel injection timing to the retard side.

[Action]

The operation of the present invention will be described below. When the de-easel engine is operated, the deterioration of the injection nozzle progresses over time, and the valve opening pressure decreases, so even with the same pressure characteristics of the fuel injection pump, the valve opening timing becomes earlier, The actual injection timing is advanced, and NOx, etc. in the exhaust gas increases. The inventors have devised to use a control value for performing idle speed control (idle speed control) as a means for calculating the amount of decrease in the nozzle opening pressure. That is, when the nozzle valve opening pressure decreases, the actual injection timing advances and the actual injection amount also increases. In the idle speed control, in order to prevent the increase of the idle speed due to the increase of the actual injection amount, the fuel injection amount is controlled and decreased so that the idle speed becomes a predetermined speed.
In the present invention, the amount of change in the control value of the fuel injection amount is calculated, the amount of decrease in the valve opening pressure is roughly estimated, and the injection timing is corrected to the retard side accordingly. That is, the idle speed control (feedback control)
When it is determined that the actual fuel injection amount is in the increasing direction from the amount of change that attempts to decrease the fuel injection amount of the control amount of
It is assumed that the nozzle opening pressure has dropped. Further, it is determined that the valve opening pressure timing is advanced as the valve opening pressure is lowered and the actual injection timing is advanced. At this time, according to the amount of change, correction is made to the retard side. Therefore, it is possible to reliably correct and prevent an error in the fuel injection timing due to the decrease in the nozzle opening pressure. Yotsutte
It is possible to prevent an increase in the knock noise of the engine and an increase in NOx in the exhaust gas that accompany the advance of the injection timing.

【Example】

Hereinafter, an electronically controlled diesel engine for a vehicle in which the method for controlling a fuel injection timing of a diesel engine according to the present invention is implemented will be described in detail. 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, there is provided a turbocharger 14 including a turbine 14A rotated by heat energy of exhaust gas and a compressor 14B rotated in conjunction with the turbine 14A. 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 is provided with a main intake air which is adapted to rotate non-linearly 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, 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 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 shaft of
42A, a feed pump 42B fixed to the pump drive shaft 42A for pressurizing the fuel (FIG. 2 shows a state of being developed 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 speed and 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 cell, the fuel cut valve 52 for cutting the fuel, and the pilot valve for controlling the fuel injection rate during the pilot injection. An injection device 53, a delivery valve 42L for preventing backflow of fuel and backward drip,
Is provided. A glow current is supplied to the glow plug 36 via a glow relay 37. 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 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. 3, 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 an A / D converter 56L output to the CPU 56A. I / O port 56M to capture
Starter signal input via buffer 56N, air conditioner signal input via buffer 56P, torque converter signal input via buffer 56Q, ignition timing sensor 38 output input via waveform shaping circuit 56R, etc. I / O port 56S for taking in the CPU56A and the ignition timing sensor 3
8 Output is wave-shaped and the input interrupt port ICA of the CPU56A
The waveform shaping circuit 56R for directly capturing into P2 and the waveform shaping circuit 5 for waveform shaping of the output of the reference position sensor 44 and directly capturing into the same input interrupt port ICAP2 of the CPU 56A.
6T, a waveform shaping circuit 56U for shaping the output of the engine speed sensor 46 and directly taking it into the input interrupt port ICAP1 of the CPU 56A, and for driving the electromagnetic spill valve 50 according to the calculation result of the CPU 56A. A drive circuit 56V, a drive circuit 56W for driving the TCV 48 according to the calculation result of the CPU 56A, a drive circuit 56X for driving the fuel cut valve 52 according to the calculation result of the CPU 56A, and C
A drive circuit 56Y for driving the pilot injection device 53 according to the calculation result of the PU 56A, and a common bus 56Z for connecting between the respective constituent devices to transfer data and instructions.
It consists of and. 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 fuel injection timing in this embodiment is executed according to the flow chart shown in FIG. That is, at step 100, the engine speed Ne, the accelerator opening A
Incorporating ccp, engine water temperature THW, air conditioner signal and other signals, step 110 calculates the basic command value of fuel injection timing this time. Next, at step 120, it is judged if the engine is in the idle state. When the determination result is positive, that is, when the engine is in the idle state, the routine proceeds to step 130, where the fuel injection amount required to control the engine speed to a predetermined idle speed is calculated based on the signal acquired at step 100. A control value of the valve opening time of the injection nozzle 34 required to obtain the calculated fuel injection amount (hereinafter referred to as an ISC control value) is calculated. Then step 1
At 40, it is determined whether or not the conditions for calculating the injection timing correction amount are met. In the case of the embodiment, this calculation condition is that the idle speed is set to a value when the diesel engine 10 is completely warmed up, the transmission gear is neutral, the air conditioner is off, and a large electric load (headlight, differential degauss, etc.) is not used. When all the conditions that change of 20 rpm or less are satisfied and the stable state continues for 20 seconds or more. As a result, an appropriate ISC control value can be stored and erroneous correction of the fuel injection timing can be prevented. If the determination result in step 140 is positive, that is, if the injection timing correction amount is calculated, the process proceeds to step 150 and it is determined whether or not the process has proceeded to this step for the first time. If the determination result is positive, that is, if the correction amount calculation condition is satisfied and this step is executed for the first time, the process proceeds to step 180, and the current ISC control value is stored as a reference value for calculating the fuel injection timing. On the other hand, if the determination result of step 150 is negative, that is, if the execution of this step is the second time or later, the process proceeds to step 160, the current ISC control value calculated in step 130 and the ISC control stored in step 180 for the first time. The difference between the value and the reference value is calculated as indicated by symbol A in FIG. Then, from this difference, the correction amount of the injection timing at this time (reference A'in FIG. 5) is calculated from the relationship as shown in FIG. 6, and this is stored and updated as a new correction amount every time. The inclination of the graph showing the relationship of the correction amount in FIG. 6 changes depending on the μ-F characteristic of the injection nozzle 34 used, the cam profile of the injection pump 42 used, and the like. Is. Then proceed to step 170. Further, after step 180 is executed, if the determination result of step 120 or step 140 is negative, the process proceeds to step 170. In this step 170, the latest correction amount calculated and updated up to the previous time is subtracted from the calculated injection timing command value, as indicated by reference sign A'in FIG. 5, to obtain the current injection timing command value. To do. As described above, in step 160, the correction amount (reference numeral A'in the figure) of the injection timing command value is obtained from the difference between the first and second ISC control values in FIG. 5, and the result is reflected in the injection timing in step 170. As shown in the figure, the injection timing command value is corrected to an appropriate value, the deterioration of the injection nozzle progresses over time, and the valve opening pressure decreases, so that the actual injection indicated by symbol B in the figure The timing advance is corrected. Therefore, it is possible to prevent the injection timing from advancing excessively due to the decrease in the valve opening pressure, and to prevent NOx in the exhaust gas, engine vibration, and noise. It should be noted that in the above-mentioned embodiment, the IS is calculated by the correction amount calculation graph as shown in the flowchart of FIG. 4 and FIG.
The correction value of the injection timing command value was obtained from the C 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 can be used. In that case, different graphs can be used depending on individual conditions, for example, the μ-F characteristic of the injection nozzle, the cam profile of the injection pump used, and the like. Further, in the above embodiment, in calculating the amount of change in the control value of the idle speed control, the first control value was used as the reference value, but the calculation method is not limited to this, and other methods are used. The amount of change can be calculated with. Further, in the above-described embodiment, the present invention relates to a diesel engine with a supercharger in which the fuel injection amount is controlled by the electromagnetic spill valve 50 and the pilot injection amount is controlled by the pilot control device 53. However, the scope of application of the present invention is not limited to this, and it is obvious that the present invention can be similarly applied to a general diesel engine equipped with a fuel injection amount control actuator other than the electromagnetic spill valve.

【The invention's effect】

As described above, according to the present invention, it is possible to prevent the advance of the fuel injection timing caused by the decrease in the nozzle opening pressure with time. Therefore, for example, even if the injection nozzle deteriorates with time and the valve opening pressure decreases, it is accurately corrected and the knocking noise of the diesel engine due to the excessive advance of the injection timing accompanying the increase of the valve opening pressure is caused. Prevent vibration and noise,
It has excellent effects such as reduction of NOx in exhaust gas.

[Brief description of drawings]

FIG. 1 is a flow chart showing the gist of the present invention, and FIG. 2 is a sectional view showing the overall construction of an embodiment of an electronically controlled diesel engine for an automobile to which the present invention is applied, including a partial block diagram, 3 is a block diagram showing the structure of the electronic control unit, FIG. 4 is a flow chart showing a routine for controlling the fuel injection timing, and FIG.
A diagram showing an example of a controlled command value of the fuel injection timing, 6th
The figure is a diagram showing an example of obtaining the correction amount of the fuel injection timing from the control value of the idle speed, which is used in the routine. 10 …… Diesel engine, 20 …… Accelerator position sensor, Accp …… Accelerator opening, 38 …… Ignition timing sensor, 42 …… Injection pump, 42J …… Timer piston, 44 …… Reference position sensor, 46 …… Engine Rotation sensor, NE …… Engine speed, 48 …… Timing control valve (TCV), 56 …… Electronic control unit (ECU).

Claims (1)

[Claims] 1. A fuel injection system which uses an injection nozzle for injecting fuel into an engine combustion chamber when the fuel pressure exceeds a valve opening pressure, and further, at the time of idling, a feed back according to a difference between a target engine speed and an actual engine speed. A fuel for a diesel engine that calculates a control amount and controls the fuel injection amount by the feedback back control amount so that the actual engine speed matches the target engine speed and controls the fuel injection timing according to the engine operating state. In the injection timing control method, it is determined that the actual fuel injection amount is in the increasing direction from the amount of change in the feedback control amount for decreasing the fuel injection amount. As a decrease in valve pressure, a correction value for the fuel injection timing is calculated from the amount of change in the feed back control amount, and the fuel correction timing is calculated according to the calculated correction value. Fuel injection timing control method for diesel engine and corrects the injection timing to the retard side.