JPS61234246A - Injection timing control for diesel engine - Google Patents

Abstract

PURPOSE:To prevent the abnormal delay angle in compression cycle in case of high speed and high load by prohibiting the feedback control according to the detected ignition timing when the detected ignition timing is within a set time starting from a standard position. CONSTITUTION:In a Diesel engine 10, the injection timing is feedback-controlled according to the deviation between the aimed ignition timing determined on the basis of the engine load and the engine revolution speed and the actual ignition timing detected by an ignition timing sensor 38. It is judged from an ignition timing sensor 38 if the detected ignition timing input into an ECU 56 is, for example, 10 deg. CA or not, for a set time from the standard position in the vicinity of the top dead center. If the result of judgement is 'NO', and the ignition timing is abnormally early, and when it is judged that the thermal infrared ray in compression cycle or the foreburning of the residual fuel is detected, or it is judged that the time is outside the ignition calculation time, the normal value in the preceding time is used as it is as the actual ignition timing.

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 diesel engine for automobiles 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 according to 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, Japanese Patent Laid-Open No. 57-28842 and Japanese Patent Laid-Open No. 58-25
582, ￥FI Open Show 58-192935, JP Open Show 59-
153942, etc., an ignition timing sensor such as a flame sensor is installed at the combustion point, 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). IIJ
It is proposed to do III. When performing feedback control of injection timing based on the output signal of such an ignition timing sensor, normally, the control shown in FIG.
The main waveform of the reference position sensor output (hereinafter referred to as TDC) as shown in
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 8(B), which is obtained by shaping the waveform of the raw waveform), the waveform shown in Figure 8(C) is calculated. The rise time T of the ignition pulse as shown in FIG. 8(D) obtained by shaping the ignition signal as shown in FIG.
The ignition timing (time) TIGTDC is calculated from the time up to int. FIG. 8(E) 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 or auxiliary combustion of residual fuel during the compression process other than the main combustion, and this timing may be incorporated into the control device as the ignition timing. be. Then, 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. Therefore, at high speed and high load, sometimes (
The injection timing is abnormally retarded (approximately once every 100 times), resulting in engine vibration due to a decrease in engine torque and an abnormal increase in exhaust gas temperature.

[Purpose of the invention]

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

[Means to solve the problem]

The present invention provides a diesel engine that performs feedback control of injection timing according to a 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. The above object is achieved by including a procedure for making a determination, and a procedure for prohibiting feedback control based on the currently detected ignition timing when the detected ignition timing is within a set period from the reference position. Further, in the embodiment of the present invention, the set period is set within 10° OA from the reference position near the top dead center, thereby reliably preventing erroneous feedback control due to thermal infrared rays and auxiliary combustion of residual fuel during the compression process. This is how it was done. Further, in another embodiment of the present invention, when the detected ignition timing is within a set period from the reference position, feedback control based on the previously detected ignition timing is continued, so that stable control is performed. This is what I did. Further, in another actual engine according to the present invention, when the detected ignition timing is within a set period from the reference position, feedback control is performed with the target ignition timing as it is as the current detected ignition timing, so that the actual In this case, feedback control is prohibited, and a stable l1lJt[l is performed.

[Effect] In the present invention, when performing feedback control of the injection timing, the detection When the ignition timing is within a set period from the reference position, feedback control based on the currently detected ignition timing is prohibited, and feedback control based on the previously detected ignition timing, for example, is continued. Therefore, even if the ignition timing sensor erroneously detects thermal infrared rays or auxiliary combustion of residual fuel during the compression process, especially at high speeds and high loads, the ignition timing sensor will not erroneously retard lllIw, and stable control will be performed. It is possible to prevent engine vibration and abnormal exhaust gas rise due to torque reduction due to constant retardation. 【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. A turbocharger 14 is provided downstream of the intake air temperature sensor 12 and includes a turbine 14A rotated by thermal energy of exhaust gas and a compressor 14B rotated by movement of the turbine 14A. A waste gate valve 1 is provided on the upstream side of the turbine 14A of the turbocharger 14 and on the downstream side of the compressor 14B to prevent excessive rise in intake pressure.
5. The venturi 16 downstream of the compressor 14B includes:
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, in order to limit the flow rate of intake air when the vehicle is idling. The opening degree of the accelerator pedal 17 (hereinafter referred to as the accelerator opening degree) AOCp is detected by the accelerator position 1 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 . Negative pressure generated by a negative pressure pump 26 is supplied to the diaphragm device 124 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 1o,
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 10G 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 with the rotation of the crankshaft of the diesel engine 10, and a feed pump 42B (FIG. 2 shows a feed pump 42B fixed to the drive shaft 42A for pressurizing fuel). ), a fuel pressure adjustment valve 42C for adjusting the fuel supply pressure, and a gear 4 fixed to the drive shaft 42A.
20 rotational displacement to the reference position, e.g. top dead center (TDC)
a reference position sensor 44 made of, for example, an electromagnetic pickup, for detecting the engine rotation speed, and an engine rotation sensor 46 made of, for example, an electromagnetic pickup, for detecting the engine rotation speed from the rotational displacement of the gear 42E, which is also fixed to the drive shaft 42A. , a roller ring 42H for reciprocating the face cam 42F and the plunger 42G and changing the timing thereof, and a timer piston 42J for changing the rotational position of the roller ring 42H (90° in FIG. 2).
), a timing control valve (hereinafter referred to as TCV) 48 for controlling the injection timing by controlling the position of the timer piston 42J, and fuel from the plunger 42G via the spill boat 42K. An electromagnetic spill valve 50 for controlling the fuel injection amount by changing the release timing, a fuel cut valve 52 for cutting fuel, and a delivery valve 42L for preventing fuel backflow and after-mold. is provided. A glow current is supplied to the glow plug 36 via a glow relay 37. The ignition timing sensor 38, as shown in detail in FIG.
A cylindrical case 38A that is inserted and fixed into the cylinder head IOA of the diesel engine 10, a light guide 38B made of quartz glass, for example, inserted into the center of the case 38A for transmitting combustion light, and the light A light receiving element 38C made of, for example, a silicon photodiode or a photodiode is provided for detecting the light transmitted by the conductor 38B and converting it into an electric signal. The intake temperature sensor 12, the low accelerator position sensor 201, the intake pressure sensor 32, the ignition timing sensor 38, the water wetness sensor 40,
A reference position sensor 44, an engine rotation sensor 46, a glow current sensor 54 that detects the glow current flowing through the glow plug 36, an engine switch, an air conditioner switch,
Neutral safety switch output, vehicle speed signal, etc.
The VSV28.30. Glow relay 37, TCV48,
The electromagnetic spill valve 50, fuel cut valve 52, etc. are controlled. As shown in detail in FIG. 4, the ECtJ 56 includes a central processing unit (hereinafter referred to as CPU) 56A for performing various arithmetic processing, and a central processing unit 4a'1j for recording control blocks and various data. Read-only memory (hereinafter referred to as RO)
56B, a random access memory (hereinafter referred to as RAM) 56G for temporarily storing calculation data etc. in the CPLI 56A, an output clock 56D for generating a clock signal, and a buffer 56E. The input water temperature sensor 40 output, buffer 56F
a multiplexer for sequentially taking in the output of the intake temperature sensor 12 inputted via the intake air temperature sensor 12, the output of the intake pressure sensor 32 inputted via the buffer 56G, the output of the accelerator position sensor 20 inputted via the buffer 56H, etc. (
g, below, referred to as MPX) 56,! :, aMPX56
11', power (7), and a common bus 56Y for transferring signals and commands. Input to input/output board 568 as well as input to input/output port 568 is input to the same input interrupt terminal 1' CA P 2 and below.
The operation of the embodiment will be explained. The injection timing control in this embodiment is carried out according to the flow charts shown in FIGS. 5 and 6. That is, the ICAP2 manual interrupt shown in FIG. 5 determines whether or not the current interrupt is due to an ignition signal. If the determination result is negative, that is, if it is determined that the current input is due to an input interruption of the reference position signal, the process proceeds to step 112, where the current interrupt time Tint is stored in the reference position time T o c in, and Exit this routine. On the other hand, if the determination result in step 110 is positive,
That is, when it is determined that the current input is due to an input interruption of the ignition signal, the process proceeds to step 114, and the ignition flag
IG is set, and then the process proceeds to step 116, where the time TIGTDC from the reference position to ignition is calculated by subtracting the reference position time TDCin from the current interrupt time Tint, as shown in the following equation 1. End the routine. TIGTO(, -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 determination result is positive, the process proceeds to step 212, where the engine is rotated by 1/2 revolution (
45°C calculated based on a time of 180° CA) minutes
Using the A rotation time T45, the ignition timing (time) TIGTDC is converted to the ignition timing (angle) IGCA as shown in the following formula.
Convert to IGCA4-T IGTDC/T45x45°...(
2) Next, the process proceeds to step 214, where the calculated ignition timing (angle) IGCA is calculated from the reference position for a set period of time, e.g.
Determine whether the temperature is 0°CA or higher. If the determination result is positive and it is determined that the ignition timing is not abnormally early, the process proceeds to step 216, and the overlap between the TDC pulse and the ignition pulse is calculated from the ignition timing (angle) IGCA as shown in the following equation. Subtracting the calculated offset of 7.6° to prevent this is set as the actual ignition timing ACTill, update the actual ignition timing ACT i. to the latest value, and proceed to the next step. ACT Ig←IGOA -7,6°...(3) On the other hand, if the judgment result in step 214 is negative, the ignition timing is abnormally early, and thermal infrared rays and auxiliary combustion of residual fuel are detected during the compression stroke. When the determination is made, or when the determination result in step 210 is negative and it is determined that it is not the ignition calculation time, the actual ignition timing ACTig is not updated, that is, the previous normal value is used as the actual ignition timing. A
As CT1, proceed to the next step. Feedback control is performed so that the deviation between the actual ignition timing A CT tg calculated in this way and the target ignition timing T RG iu 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 early, by performing feedback control using the previous actual ignition timing ACTig, abnormal retardation due to thermal infrared rays and supplementary combustion of residual fuel during the compression process can be avoided. Prevented. In this example, since the set period is within 10'CA from the reference position near top dead center, detection of an abnormally early ignition timing due to thermal infrared rays or auxiliary combustion of residual fuel during the compression process 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 a set period from the reference position is not limited to this, and for example, the target ignition timing T RG
iu as it is, the current detected ignition timing A CT i! As J, it is also possible to substantially not perform feedback control or to perform oven loop control it based on the basic injection timing T[) base. In the embodiment described above, the engine load was detected from the accelerator opening degree ACCI) output from the accelerator position sensor 2o, 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 supercharged diesel engine in which the fuel injection amount was controlled by the electromagnetic spill valve 50, but the scope of application of the present invention is not limited to this. It is clear that the present invention is equally applicable to general diesel engines equipped with fuel injection key control actuators other than electromagnetic spill valves.

As described above, according to the present invention, the injection timing is not abnormally retarded due to thermal infrared rays during the compression process or auxiliary combustion of residual fuel, especially at high speeds and high loads. Therefore, it has an 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 the drawing]

FIG. 1 is a flow chart 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 diesel engine for automobiles in which the present invention is adopted. Sectional diagram including block diagram, 3rd
FIG. 4 is a block diagram showing the configuration of the electronic control unit, and FIG. FIG. 6 is a flowchart showing an input interrupt routine for calculating injection timing, and FIG. 7 is a flowchart showing a routine in the main routine for controlling injection timing. FIG. FIG. 8 is a diagram showing an example of the relationship between pulses. FIG. 2 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. DESCRIPTION OF SYMBOLS 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”-9 Imink Mm Valve (TCV), 56
...Electronic control unit (ECU), TDCIn・
...Reference position time, TIGTDC...Ignition timing (time), IGCA...
Ignition timing (angle), AGT ta...Actual ignition timing, TRGig...Target ignition timing.

Claims (4)

[Claims] (1) A diesel engine that performs feedback control of 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 an ignition timing sensor. In the injection timing control method, the steps include: detecting ignition timing from the output signal of the ignition timing sensor; determining whether the detected ignition timing is within a set period from a reference position; and A method for controlling injection timing of a diesel engine, comprising: a step of prohibiting feedback control based on the currently detected ignition timing when it is within a set period from . (2) Set the above setting period to 10 from the reference position near top dead center.
The injection timing control method for a diesel engine according to claim 1, wherein the injection timing is within °CA. (3) The injection timing control method for a diesel engine according to claim 1, wherein when the detected ignition timing is within a set period from the reference position, feedback control based on the previously detected ignition timing is continued. (4) The diesel engine according to claim 1, wherein when the detected ignition timing is within a set period from the reference position, feedback control is performed using the target ignition timing as it is as the current detected ignition timing. Injection timing control method.