JPS61187556A - Fuel injection timing control method of diesel engine - Google Patents

Abstract

PURPOSE:To suppress the generation of knocking by correcting the correction term which varies according to the intake pressure and correcting the aimed ignition timing to the delayed angle side according to the correction term when the intake pressure is low, in the feedback control of the ignition timing according to the deviation between the aimed ignition timing and the actual ignition timing. CONSTITUTION:When the feedback conditions for fuel injection timing are fulfilled, aimed ignition timing is calculated on the basis of each output signal of a revolution speed sensor (not shown in the figure) and an acceleration position sensor 20 in an ECU56. Then the deviation between the aimed ignition timing and the actual ignition timing obtained from the output of an ignition timing sensor 38 is calculated, and the fundamental injection timing calculated beforehand is corrected according to the deviation, and the timer mechanism of an injection pump is controlled according to the corrected injection timing. In the above, the correction term which varies according to the intake pressure detected by an intake pressure sensor 32 is obtained, and when the intake pressure is low, the aimed ignition timing is corrected to the delayed angle side according to the correction term so as not to advance excessively.

Description

[Detailed description of the invention]

(Industrial Application Field 1) The present invention relates to an injection timing control method for a diesel engine, and in particular, a method 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 a target ignition timing determined based on a numerical value and an actual ignition timing detected using an ignition timing sensor.

[Prior art] Japanese Patent Application Laid-open No. 57-28842 and No. 58-25 disclose injection timing control for optimizing the exhaust gas purification performance of diesel engines, especially diesel engines for automobiles.
582, JP 58-192935, JP 59-15
3942, etc., an ignition timing sensor such as a flame sensor is installed at the end of combustion, and the ignition timing sensor detects the ignition timing in the downward direction of combustion (when the pressure in the cylinder suddenly rises due to combustion, or when the combustion light due to ignition is detected). By feeding back the detection results of the start-up timing), the actual ignition timing can be adjusted.
It has been proposed to perform feedpack control on the injection timing so that the required ignition timing is determined by the engine load, engine speed, etc. In such feedback control of the injection timing based on the output of the ignition timing sensor, the signal from the ignition timing sensor is usually waveform-shaped by a certain threshold value vth, as shown by the solid line A in FIG. 7 (in the case of flat ground). The ignition timing is calculated from the difference between that signal and the reference position. According to this method, when the intake pressure decreases, such as when going up to a high altitude, the ignition delay is corrected and the injection timing is automatically advanced, as shown by IiB in FIG. Therefore, even if the intake pressure decreases, the same torque as in normal times can be obtained. (Problems to be Solved by the Invention) However, when the intake pressure decreases, such as when going up to a high altitude, there is not only an ignition delay due to the decrease in intake pressure (Fig. 7C), but also a delay in start-up due to a decrease in the ignition timing sensor output. Due to the slowing, the time to exceed the same threshold m v th is also delayed (7th
Figure D). For this reason, the feedback correction causes the injection timing to be advanced by an amount D more than necessary, resulting in a problem that knocking occurs. OBJECT OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and the ignition timing is not controlled to be excessively advanced even at high altitudes. An object of the present invention is to provide an injection timing control method for a diesel engine that can minimize torque reduction.

[Means to solve the problem]

According to the present invention, the injection timing is feedback-controlled in accordance with 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. As shown in Figure 1, the diesel engine injection timing control method includes a procedure for determining a correction term that changes depending on the intake pressure, and a method that prevents the injection timing from advancing too far when the intake pressure is low. The above object is achieved by including a step of correcting the target ignition timing to the retarded side. (Effect 1 In the present invention, depending on 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,
When performing feedback control on the injection timing, a correction term that changes depending on the intake pressure is used to correct the target ignition timing to the retarded side so that the injection timing does not advance too far when the intake pressure is low. Therefore, even at high altitudes, the injection timing does not become overadvanced, and knocking does not occur. [Example] Hereinafter, an example of an electronically controlled diesel engine for automobiles in which the injection timing control method according to the present invention is adopted will be described in detail with reference to the drawings. In this embodiment, as shown in FIG. 2, it is disposed downstream of an air cleaner (not shown). An intake air temperature sensor 12 is provided to detect 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 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 via a wastegate valve 15 for preventing the intake pressure from rising too much. The venturi 16 downstream of the compressor 14B includes:
A main intake air control valve 18 is provided which is configured to rotate non-linearly in conjunction with an accelerator pedal 17 disposed at the driver's seat to limit the flow rate of intake air during idling or the like. The opening degree of the accelerator pedal 17 (hereinafter referred to as accelerator opening degree) A ccp is detected by an accelerator position 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 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 valve 18.22. In the cylinder head 1°A 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 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, and a feed pump 42B that is fixed to the drive shaft 42A and that pressurizes the fuel. 90' shows the expanded state>, a fuel pressure adjustment valve 42C for adjusting the fuel supply pressure, and a gear 4 fixed to the drive shaft 42A.
From the 2D 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 speed 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. , face cam 42F and plunger 42G
and a timer piston 42J (90 in FIG. 2) for changing the rotational position of the roller ring 42H.
48 (hereinafter referred to as TCV) for controlling the injection timing by controlling the position of the timer piston 42J, and a plunger 42G via a spill port 42K. an electromagnetic spill valve 50 for controlling the fuel injection amount by changing the fuel release timing of the fuel, a fuel cut solenoid 52 for cutting fuel, and a delivery valve 42L for preventing fuel backflow and rear molding. A glow current is supplied to the glow plug 36 via a glow relay 37.The ignition timing sensor 38 includes, as shown in detail in FIG.
A cylindrical case 38A inserted and fixed into the cylinder head 10A of the diesel engine 10, a light guide 38B made of, for example, quartz glass inserted into the center of the case 38A and made of quartz glass for transmitting combustion light, and the light A light receiving element 3 made of, for example, a silicon photodiode, for detecting the light transmitted by the conductor 38B and converting it into an electrical signal.
8C is provided. 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 reference position sensor 44, an engine speed sensor 46, a glow current sensor 54 that detects the glow current flowing through the glow plug 36, 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, and by the output of the ECU 36, the VSV28.30
, glow relay 37, TCV48, II magnetic spill valve 50
, fuel cut solenoid 52, etc. are controlled. As shown in detail in FIG. 4, the EC1J56 includes a central processing unit (hereinafter referred to as CPU) 56A for performing various arithmetic operations, and a read-only memory (hereinafter referred to as CPU) for storing control programs and various data. , ROM) 56B, a random access memory (hereinafter referred to as RAM) 56C for temporarily storing calculation data etc. in the CPLI 56A, a clock 560 that generates a clock signal, and a buffer 56E. The water temperature sensor 40f + force inputted, the output of the intake temperature sensor 12 inputted via the buffer 56F, and the buffer 5
The M P 'X 56K
An analog-digital converter (hereinafter referred to as an A/D converter) 56L for converting an output analog signal into a digital signal, and a CPU 56A that converts the output of the A/D converter 56L.
Input/output boat 56M and buffer 56N for importing into
The CPU 56 receives the starter signal inputted via the starter signal, the air conditioner signal inputted via the buffer 56P, the torque converter signal inputted via the buffer 56Q, the output of the ignition timing sensor 38 inputted via the waveform shaping circuit 56R, etc.
an input/output boat 56S for inputting the output to the input interrupt terminal A, the waveform shaping circuit 56R for waveform shaping the output of the ignition timing sensor 38 and inputting it directly to the input interrupt terminal ICAP2 of the CPU 56A, and the output of the reference position sensor 44. After shaping the waveform, the same input interrupt terminal ICAP2 of the CPU 56A is used.
a waveform shaping circuit 56T for directly inputting the output to the CPU 56;
A waveform shaping circuit 56U for directly capturing the waveform into the CP
A drive circuit 56V for driving the electromagnetic spill valve 50 according to the calculation result of the U56A, a drive circuit 56W for driving the TCV 48 according to the calculation result of the CPtJ56A, and a drive circuit 56W for driving the TCV 48 according to the calculation result of the CPU 56A. It is comprised of a drive circuit 56X that drives the fuel cut solenoid 52, and a common bus 56Y that connects each of the component devices and transfers data and commands. Here, the ignition signal output from the waveform shaping circuit 56R is
The reason why this signal is input not only to the input interrupt terminal ICAP2 of the PU 56A but also to the input/output port 56S is to distinguish it from the reference position signal output from the waveform shaping circuit 56T that is input to the same input interrupt terminal ICAP2. The effects of the embodiment will be explained below. Injection timing control in this embodiment is executed according to a flowchart as shown in FIG. That is, step 11 is performed every time a certain period of time, for example, 50 msec, elapses.
For example, the basic injection timing 7[)base is calculated from the engine speed Ne and the accelerator opening ACp. Next, the process proceeds to step 112, where it is determined whether a feedback condition is satisfied based on, for example, the operating state (deceleration or absence) and the presence or absence of an ignition signal. If the determination result is positive, the process proceeds to step 114, and the target ignition timing T Ra i is determined from the engine speed Ne and the accelerator opening A ccp.
Calculate g. The target ignition timing T RG ig is, for example, advanced from the ignition timing corresponding to the basic injection timing T D base. Next, the process proceeds to step 116, where a correction term pigt corresponding to the intake pressure piIO determined from the output of the intake pressure sensor 32 is calculated using the relationship shown in FIG.
I do. Next, the process proceeds to step 118, where the correction term P1 (It is added to the target ignition timing TRG iu and set as a new target ignition timing, as shown in the following equation. TRG ig+p irim →TRG
iIJ ...... (1) Here, the correction term P
The intake pressure -1501 mHu at which the value of tut begins to rise is a value corresponding to idling at a high altitude. Next, the process proceeds to step 120, where the deviation ΔIG between the target ignition timing T RG ig and the actual ignition timing A CT ig determined from the output of the ignition timing sensor 38 is calculated as shown in the following equation.
Calculate. ΔIG-TRGio-ACTig (2)
Next, the process proceeds to step 122, in which an integral term Qi and a proportional term Dp for feedback control of the injection timing are calculated according to the obtained deviation ΔIG, as shown in the following equation. [)i −r(ΔIG) ・・・・・・・・・
(3) Dp-g (ΔIG) ・・・・・・・・・
・(4) Next, proceed to step 124, and calculate the control duty ratio □uty of the TC 48 by adding the integral term Di and the proportional term Dp to the basic injection timing T D base as shown in the following equation, and then execute this routine. end. Duty = TDbase + [)i + DD - (5)
On the other hand, if the determination result in step 112 is negative,
That is, when the feedback condition is not satisfied, the process proceeds to step 126, where the basic injection timing T[) base is directly set as the control duty ratio □uty of the TCV 48,
Exit this routine. In this embodiment, when the intake pressure is less than -150n)-1g, the control duty ratio Duty is equal to the correction term p.
It is corrected to the lag side by igt. Therefore, even when the intake pressure decreases at high altitudes, the calculated target ignition timing T RG +o will not advance too much due to a delay in detecting the actual ignition timing. Knocking caused by corners is prevented. In the above embodiment, the engine load is detected from the accelerator opening ACCF+ output from the accelerator position sensor 20, but the method for detecting the engine load is not limited to this. In the above embodiment, the present invention has 1! Magnetic spill valve 50
However, the scope of application of the present invention is not limited to this, and is applicable to general diesel engines equipped with fuel injection amount control actuators other than electromagnetic spill valves. It is clear that the same applies to diesel engines. Effects of the Invention 1 As explained above, according to the present invention, even when the intake pressure decreases at high altitudes, the injection timing is not controlled to be overadvanced due to a delay in detecting the actual ignition timing. Therefore, there is an excellent effect that knocking does not occur and torque reduction at high altitudes can be minimized.

[Brief explanation of drawings]

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
The figure is a vertical cross-sectional view showing the configuration of the ignition timing sensor used in the embodiment, FIG. 4 is a block line section showing the configuration of the electronic control unit, and FIG. 5 is the injection timing sensor. FIG. 6 is a flowchart showing a routine for controlling the same, and FIG. 7 is a flowchart showing an example of the relationship between intake pressure and correction term.
The figure is a miniature diagram showing an example of the output signal of the ignition timing sensor. □ 10...Diesel engine, 17...Accelerator pedal, 20...Accelerator position sensor, 32...Intake pressure sensor, pim...Intake pressure, 34...Injection nozzle, 38...Blue Fire timing sensor, 42... Injection pump, 42J... Timer piston, 44... Reference position sensor, 46... Engine speed sensor, 48... Timing control valve (TCV), 56... Electronic control unit (ECU), T Q base...basic injection timing, TRG1...target ignition timing, Pigt...correction term, ACTi...actual ignition timing, ΔIG...deviation, [ )uty...control duty ratio.

Claims (1)

[Claims] (1) A diesel engine that performs 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 an ignition timing sensor. In an engine injection timing control method, a procedure for determining a correction term that changes according to intake pressure, and using the correction term, the target ignition timing is corrected to the retarded side so that the injection timing does not advance too much when the intake pressure is low. A method for controlling the injection timing of a diesel engine, the method comprising: