JPH036341B2 - - Google Patents

Description

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

The present invention relates to an injection timing control method for a diesel engine, and in particular, a target determined based on at least engine load and engine rotation speed, suitable for use in an electronically controlled automobile diesel engine equipped with an ignition timing sensor. The present invention relates to an improvement in an injection timing control method for a diesel engine in which the injection timing is feedback-controlled in accordance with the deviation between the ignition timing and the actual ignition timing detected using an ignition timing sensor.

[Conventional technology]

Regarding injection timing control for optimizing the exhaust gas purification performance of diesel engines, especially automotive diesel engines, JP-A-57-28842, JP-A-58-25582, JP-A-58-192935, JP-A-59 −
153942 etc., an ignition timing sensor such as a flame sensor is installed in the combustion chamber, and the ignition timing sensor detects the ignition timing in the combustion chamber (when the pressure in the cylinder suddenly rises due to combustion, or when the combustion light rises due to ignition). It has been proposed to perform feedback control of the injection timing so that the actual ignition timing becomes the required ignition timing determined by the engine load, engine speed, etc., by feeding back the detection results of the timing at which the injection timing increases. In such feedback control of the injection timing based on the output signal of the ignition timing sensor, a waveform-shaped waveform of the reference position sensor output raw waveform (hereinafter referred to as TDC raw waveform) as shown in FIG. 8A is usually used. Figure 8D is obtained by shaping the ignition signal as shown in Figure 8C from the rise time (hereinafter referred to as reference position time) TDCin of the reference position pulse (hereinafter referred to as TDC pulse) as shown in Figure 8B. The ignition timing (time) TIGTDC is calculated from the time until the rise time Tint of the ignition pulse as shown in . FIG. 8E shows an engine rotation pulse (hereinafter referred to as NE pulse) generated in accordance with engine rotation.

[Problems to be solved by the invention]

However, at high speeds and high loads, the ignition timing sensor may detect thermal infrared rays during the compression process and pre-combustion of residual combustion other than the main combustion, and this timing may be taken into the control device as the ignition timing. be. As a result, the detected ignition timing becomes abnormally fast, so the control device performs feedback control to delay the ignition timing in order to bring the detected ignition timing closer to the target ignition timing. degree) injection timing is abnormally retarded,
This has had problems in that engine vibrations and abnormal exhaust temperature increases may occur due to a decrease in engine torque.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and is an injection method for a diesel engine that can prevent abnormal angle retardation due to thermal infrared rays and pre-combustion of residual fuel during the compression process, especially at high speed and high load. The purpose is to provide a timing control method.

[Means to solve the problem]

The present invention provides a diesel engine in which injection timing is feedback-controlled in accordance with the deviation between a target ignition timing determined based on at least engine load and engine speed and an actual ignition timing detected using an ignition timing sensor. In the engine injection timing control method, as shown in FIG. A procedure for determining whether or not the detected ignition timing is within the set period in which no ignition occurs, and when the detected ignition timing is within the set period, prohibits feedback control based on the current detected ignition timing and performs control based on the false detection value. By including steps to prevent
The above objective has been achieved. Further, in an embodiment of the present invention, the set period is set as a period from a reference position near top dead center to a predetermined position near 10° CA, so that thermal infrared rays and pre-combustion of residual fuel during the compression process are avoided. This makes it possible to reliably prevent erroneous feedback control. Further, in another embodiment of the present invention, when the detected ignition timing is within the set period, feedback control based on the previously detected ignition timing is continued, so that stable control is performed. It is. Further, in another embodiment of the present invention, when the detected ignition timing is within the set period, feedback control is performed using the target ignition timing as it is as the current detected ignition timing, thereby substantially performing feedback control. This is to ensure stable control.

[Effect]

In the present invention, when performing feedback control of the injection timing according to the deviation between the target ignition timing determined based on at least the engine load and engine speed and the actual ignition timing detected using the ignition timing sensor, detection is performed. If the ignition timing is within the set period from the reference position to the predetermined position in which normal ignition does not occur, feedback control based on the current detected ignition timing is prohibited, and, for example, feedback control based on the previously detected ignition timing is disabled. I'm trying to keep going. Therefore, even if the ignition timing sensor erroneously detects thermal infrared rays or pre-burning of residual fuel during the compression process, especially at high speeds and high loads, stable control is performed without erroneously retarding the ignition timing, and abnormalities are prevented. It is possible to prevent engine vibration and abnormal exhaust temperature rise due to torque reduction due to a sharp angle retard.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an electronically controlled diesel engine for automobiles in which an injection timing control method according to the present invention is adopted will be described in detail with reference to the drawings. As shown in FIG. 2, this embodiment includes an intake air temperature sensor 12 disposed downstream of an air cleaner (not shown) for detecting the temperature of intake air. Downstream of the intake air temperature sensor 12 is a turbine 14 that is rotated by the thermal energy of the exhaust gas.
A, and a compressor 14B that rotates 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 via a wastegate valve 15 for preventing an excessive rise in intake pressure. Bench lily 1 on the downstream side of the compressor 14B
6 is an accelerator pedal 1 disposed during driving to limit the flow rate of intake air during idling, etc.
A main intake throttle valve 18 is provided which is configured to rotate non-linearly in conjunction with the main intake throttle valve 7. Opening degree of the accelerator pedal 17 (hereinafter referred to as accelerator opening degree)
Accp is detected by the accelerator position sensor 20. A sub-intake throttle valve 2 is installed in parallel with the main intake throttle valve 18.
2, and the opening degree of the sub-intake throttle valve 22 is controlled by a diaphragm device 24. The diaphragm device 24 includes a negative pressure pump 26.
The negative pressure generated is supplied via a negative pressure switching valve (hereinafter referred to as VSV) 28 or 30. An intake pressure sensor 32 is provided downstream of the intake throttle valves 18 and 22 to detect the pressure of intake air. Cylinder head 10 of diesel engine 10
A is equipped with an injection nozzle 34 whose tip faces the engine combustion chamber 10B, a glow plug 36, and an ignition timing sensor 38. Further, the cylinder block 10C 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 drive shaft 42A that rotates in conjunction with the rotation of the crankshaft of the diesel engine 10;
Feed pump 42B for pressurizing fuel is fixed to A (Figure 2 shows the 90° expanded state)
and a fuel pressure adjustment valve 42 for adjusting the fuel supply pressure.
C, and a gear 42D fixed to the drive shaft 42A.
from the rotational displacement of the reference position, e.g. top dead center (TDC)
A reference position sensor 44 made of, for example, an electromagnetic pickup for detecting the
An engine rotation sensor 46 consisting of an electromagnetic pickup, for example, for detecting the engine rotation speed from the rotational displacement of a gear 42E fixed to the roller ring 4 for reciprocating the face cam 42F and the plunger 42G and changing the timing thereof.
2H, a timer piston 42J for changing the rotational position of the roller ring 42H (FIG. 2 shows a 90° unfolded state), and the timer piston 42.
A timing control valve (hereinafter referred to as TCV) 48 for controlling the injection timing by controlling the position of the valve J and a timing for releasing fuel from the plunger 42G via the spill port 42K. An electromagnetic spill valve 50 for controlling the fuel injection amount, a fuel cut valve 52 for cutting off fuel, and a delivery valve 42L for preventing backflow or dripping of fuel are provided. The glow plug 36 includes a glow relay 37.
Current is supplied through. As shown in detail in FIG. 3, the ignition timing sensor 38 has a cylindrical case 38A that is inserted and fixed into the cylinder head 10A of the diesel engine 10.
A light guide 38B made of quartz glass, for example, is inserted into the center of the case 38A to transmit combustion light, and the light transmitted by the light guide 38B is detected and converted into an electrical signal. A light receiving element 38C made of, for example, a silicon photodiode is provided for conversion. The intake temperature sensor 12 and the accelerator position sensor 2
0, intake pressure sensor 32, ignition timing sensor 38, water temperature sensor 40, reference position sensor 44, engine rotation sensor 46, glow current sensor 54 that detects the claw current flowing through the glow plug 36, engine switch, air conditioner switch, neutral The safety switch output, vehicle speed signal, etc. are input to an electronic control unit (hereinafter referred to as ECU) 56 and processed, and the output of the ECU 56 allows
Said VSV28, 30, glow relay 37, TCV
48, an electromagnetic spill valve 50, a fuel cut valve 52, etc. are controlled. The ECU 56, as shown in detail in FIG.
A central processing unit (hereinafter referred to as CPU) 56A for performing various calculation processes, a read-only memory (hereinafter referred to as ROM) 56B for storing control programs and various data, etc.
Random access memory (hereinafter referred to as
(referred to as RAM) 56C, a clock 56D that generates a clock signal, the output of the water temperature sensor 40 inputted via a buffer 56E, and a buffer 56C.
6F, the output of the intake pressure sensor 32, which is input via the buffer 56G, the output of the accelerator position sensor 20, which is input via the buffer 56H, etc. A multiplexer (hereinafter referred to as MPX) 56K and an analog converter for converting the analog signal of the MPX 56K output into a digital signal.
Digital converter (hereinafter referred to as A/D converter)
56L and the A/D converter 56L output to the CPU 5.
6A, an input/output port 56M, a starter signal inputted via a buffer 56N, an air conditioner signal inputted via a buffer 56P,
An input/output port 56S for inputting the torque converter signal inputted via the buffer Q, the output of the ignition timing sensor 38 inputted via the waveform shaping circuit 56R, etc. to the CPU 56A, and the ignition timing sensor 3
The waveform shaping circuit 56R waveform-shapes the 8 outputs and takes them directly into the input interrupt terminal ICAP2 of the CPU 56A, and the waveform shaping circuit 56R shapes the output of the reference position sensor 44 and takes them directly into the same input interrupt terminal ICAP2 of the CPU 56A. Waveform shaping circuit 5 for
6T, a waveform shaping circuit 56U for waveform shaping the output of the engine rotation sensor 46 and directly inputting it into the CPU 56A, and a drive circuit 56V for driving the electromagnetic spill valve 50 according to the calculation result of the CPU 56A. , 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 a drive circuit 56X for driving the fuel cut-off valve 52 according to the calculation result of the CPU 56A, and a drive circuit 56X for driving the fuel cut-off valve 52 according to the calculation result of the CPU 56A, and a drive circuit 56X for driving the fuel cut-off valve 52 according to the calculation result of the CPU 56A. It is comprised of a common bus 56Y for connection and transfer of data and instructions. Here, the reason why the ignition signal output from the waveform shaping circuit 56R is inputted not only to the input interrupt terminal ICAP2 of the CPU 56A but also to the input/output port 56S is that the waveform shaping circuit is inputted to the same input interrupt terminal ICAP2. This is to distinguish it from the reference position signal of the 56T output. The effects of the embodiment will be explained below. The injection timing control in this embodiment is executed according to the flowcharts shown in FIGS. 5 and 6. That is, in the ICAP2 input interrupt routine shown in FIG.
Step 110 is entered when an input occurs in step 2, and it is determined whether or not the current interrupt is due to an ignition signal, depending on whether or not there is an output from the ignition timing sensor 38 inputted via the input/output port 56S, for example. judge. If the determination result is negative, that is, if it is determined that the current input is due to an input interrupt of the reference position signal, the process proceeds to step 112, stores the current interrupt time Tint in the reference position time TDCin, and
Exit this routine. On the other hand, if the judgment result in step 110 is positive, that is, if it is judged that the current input is due to an ignition signal input interrupt, the process proceeds to step 114, where the ignition flag XIG is set, and then step 114 is performed.
Proceeding to step 116, the current interrupt time is calculated as shown in the following formula.
By subtracting the reference position time TDCin from Tint, the time from the reference position to ignition TIGTDC is determined.
Calculate and end this routine. TIGTDC←Tint−TDCin (1) On the other hand, in the routine in the main routine as shown in FIG. 6, first in step 210 it is determined whether it is time to calculate the ignition timing. If the judgment result is positive, proceed to step 212, and calculate the time based on the time of 1/2 engine revolution (180° CA) from the NE pulse generation interval as shown in Figure 8E above. Using the calculated 45° CA rotation time T45, the ignition timing (time) TIGTDC is calculated as shown in the following formula.
Convert to ignition timing (angle) IGCA. IGCA←TIGTDC/T45×45° ...(2) Next, the process proceeds to step 214, where the calculated ignition timing (angle) IGCA is set within a predetermined position from the reference position, for example, within 10°CA (normal ignition occurs). It is determined whether or not it is after the period in which the If the judgment result is positive and the ignition timing is not abnormally early, that is, it is judged that the ignition is normal, the step
Proceed to step 216 and calculate the ignition timing (angle) as shown in the following formula.
The actual ignition timing ACTig is calculated by subtracting the calculated offset of 7.6° to prevent overlap between the TDC pulse and the ignition pulse, etc. from the IGCA.
Update ACTig to the latest value and proceed to the next step. ACTig←IGCA−7.6° ……(3) On the other hand, the judgment result of step 214 above is negative,
When the ignition timing is abnormally early and it is determined that thermal infrared rays or pre-burning of residual fuel during the compression stroke is detected, or the determination result in step 210 is negative,
If it is not the ignition calculation time and it is cut off, the actual ignition timing ACTig is not updated, that is, the previous normal value is used as the actual ignition timing ACTig.
Proceed to next step. Actual ignition timing ACTig calculated in this way
Then, feedback control is performed so that the deviation of the target ignition timing TRGig determined based on the engine load and engine speed becomes zero. FIG. 7 shows an example of the relationship between the TDC pulse and the ignition pulse in this embodiment. In this way, when the ignition timing is detected abnormally fast, feedback control is performed using the previous actual ignition timing ACTig to detect abnormal delays caused by thermal infrared rays and pre-burning of residual fuel during the compression process. Corners are prevented. In this example, since the set period is within 10° CA from the reference position near top dead center, detection of abnormally early ignition timing due to thermal infrared rays during the compression process or pre-combustion of residual fuel is reliably excluded. be able to. Note that the setting period is not limited to this. Furthermore, in this embodiment, when the detected ignition timing is within the set period from the reference position, feedback control based on the previously detected ignition timing is continued, so the control is simple and stable. There is. Note that the specific method of prohibiting feedback control based on the current detected ignition timing when the detected ignition timing is within the set period in which normal ignition does not occur is not limited to this, for example, the target ignition timing TRGig may be changed as is. Current detected ignition timing ACTig
As a result, it is also possible to substantially not perform feedback control or to perform open loop control using the basic injection timing TDbase. In the embodiment described above, the engine load was detected from the accelerator opening degree Accp output from the accelerator position sensor 20, but the method for detecting the engine load is not limited to this. In the embodiment described above, the present invention was applied to a diesel engine equipped with a supercharger in which the fuel injection amount was controlled by the electromagnetic spill valve 50, but the scope of application of the present invention is limited to this. not,
It is obvious that the present invention can be similarly applied to general diesel engines equipped with fuel injection amount control actuators other than electromagnetic spill valves.

【Effect of the invention】

As explained above, according to the present invention, the injection timing is not abnormally retarded due to thermal infrared rays during the compression process or pre-burning of residual fuel, especially at high speeds and high loads. Therefore, it has the excellent effect of being able to prevent problems such as engine vibration and abnormal exhaust temperature rise due to torque reduction due to abnormal retardation.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the injection timing control method for a diesel engine according to the present invention, and FIG. 2 is a partial diagram showing the overall configuration of an embodiment of an electronically controlled automobile diesel engine to which the present invention is adopted. FIG. 3 is a longitudinal sectional view showing the structure of the ignition timing sensor used in the embodiment, FIG. 4 is a block diagram showing the structure of the electronic control unit, and FIG. FIG. 5 is a flow chart showing the input interrupt routine for calculating the actual ignition timing, FIG. 6 is a flow chart showing the routine in the main routine for controlling the injection timing, and FIG. 7 is a flow chart showing the input interrupt routine for calculating the actual ignition timing. , Diagram illustrating an example of the relationship between the reference position pulse and the ignition pulse in the embodiment, No. 8
The figure is a diagram showing an example of the relationship between output signals of a reference position sensor, an ignition timing sensor, and an engine rotation sensor. 10... Diesel engine, 20... Accelerator position sensor, 38... Ignition timing sensor, 42...
...Injection pump, 44...Reference position sensor, 46...
...Engine rotation sensor, 42J...Timer piston, 48...Timing control valve (TCV), 56...
...Electronic control unit (ECU), TDCin...Reference position time, TIGTDC...Ignition timing (time), IGCA
...Ignition timing (angle), AGTig...Actual ignition timing,
TRGig...Target ignition timing.

Claims (1)

[Claims] 1. Feedback control of the injection timing is performed according to the deviation between the target ignition timing determined based on at least the engine load and engine speed and the actual ignition timing detected using an ignition timing sensor. The injection timing control method for a diesel engine according to the present invention includes a procedure for detecting ignition timing from the output signal of the ignition timing sensor, and a set period during which normal ignition does not occur between a reference position and a predetermined position. a step of determining whether the detected ignition timing is within the set period, and a step of prohibiting feedback control based on the currently detected ignition timing to prevent control based on an erroneously detected value. A diesel engine injection timing control method characterized by the following. 2 The set period is calculated from the reference position near top dead center.
The injection timing control method for a diesel engine according to claim 1, wherein the period is set to a predetermined position in the vicinity of 10° CA. 3. The injection timing control method for a diesel engine according to claim 1, wherein when the detected ignition timing is within the set period, feedback control based on the previously detected ignition timing is continued. 4. The injection timing control method for a diesel engine according to claim 1, wherein when the detected ignition timing is within the set period, feedback control is performed using the target ignition timing as the current detected ignition timing. .