JPS62199945A - Control of pilot injection in diesel engine - Google Patents

Abstract

PURPOSE:To reduce the vibration and noise of an engine by correcting the pilot injection control timing in each cylinder on the basis of the distribution of the pilot injection quantity between the cylinders and executing the proper pilot injection control in all the cylinders. CONSTITUTION:The distribution of the injection quantity for each cylinder is calculated on the basis of the variation of revolution in each cylinder in the engine idling stable state by inputting each signal of an engine revolution speed sensor 22, etc. into a microcomputer 70. Then, the pilot injection control timing correction quantity is calculated according to the distribution of the injection quantity, and the instruction value is calculated by adding the correction value onto a fundamental pilot injection control value. The pilot injection starting time is controlled properly by outputting the instruction value. Therefore, the distribution of the timing of pilot injection from an injection nozzle 40 is reduced to zero, and the ignition and combustion in each cylinder are balanced, and the variation of revolution is reduced.

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD 1 The present invention relates to a pilot injection control method for a diesel engine, and in particular to an improvement in a diesel engine pilot injection control method suitable for use in an electronic L1 control diesel engine for automobiles. [Prior Art] Generally speaking, diesel engines suffer from problems such as ignition delay.
Especially when idling, rapid combustion tends to generate large combustion noise and vibration. In order to prevent this and reduce the amount of NOx emissions, which are harmful components in exhaust gas, a small amount of pilot fuel is injected prior to main injection to shorten the ignition delay of the main injected fuel and achieve slow combustion. A pilot injection control method for controlling fuel injection in diesel engines has been studied. There is a fuel injection rate control device in a diesel engine.This device is provided with a variable volume !i!I empty which communicates with a plunger high pressure chamber of a fuel injection pump and includes an accumulation piston, and which controls the variable volume empty volume. PZT<1eaadz
irconium + titanium trioxi
This is a device that controls the pilot injection of a diesel engine by making changes using a rainbow stack consisting of elements. This is so that when the angle of the face cam that drives the plunger of the fuel injection pump reaches a certain angle, the PZT cord is short-circuited or a voltage is applied to cause pilot injection.

[Problems to be solved by the invention]

By the way, the inter-nozzle valve pressure when the fuel pumped from the fuel injection pump is injected from the injection nozzle is
Usually, variations occur for each cylinder. If the inter-nozzle valve pressure varies in this way, the actual injection port (start timing and actual injection port) when injecting fuel from the injection nozzle will vary accordingly. Therefore, the command value for pilot injection of the fuel injection device However, in actual pilot injection, this twisted layer injection DI fd for each cylinder corresponds to a certain angle of the face cam.
There was a problem in that the pilot injection o4υ could not be controlled in an optimal state due to variations in the pilot injection, which distorted the effect of the pilot injection and caused rotational fluctuations in the diesel engine. OBJECT OF THE INVENTION 1 The present invention has been made in view of the above-mentioned problems of the conventional art. The purpose of this invention is to provide a pilot injection control method for diesel engines that enables the following. [Means for Solving the Problems] The present invention detects variations between each cylinder during fuel injection when pilot injecting fuel into each cylinder of a diesel engine, and based on the detected variations, performs pilot injection for each cylinder. Pilot squirt! ) The above object is achieved by estimating the fuel injection start timing and correcting the pilot injection control timing for each cylinder according to the estimated fuel injection start timing. [Operation 1] In the present invention, when pilot injecting fuel into each cylinder of a diesel engine, variations in fuel injection timing between each cylinder are detected, and based on the detected variations,
The pilot injection start timing for each cylinder is estimated, and the pilot injection start timing for each cylinder is corrected according to the estimated fuel injection start timing. Therefore, it is possible to eliminate the influence of variations in the pilot injection amount of each cylinder, so it is possible to further prevent vibrations and noise of the diesel engine during pilot injection. [Embodiment 1] Hereinafter, a fuel injection device in which a pilot injection control method for a diesel engine according to the present invention is implemented will be described in detail. The fuel injection device according to this embodiment includes a fuel injection pump 8, as shown in FIG. The fuel injection pump 8 includes a drive shaft 12 that rotates in conjunction with the rotation of a crank (not shown) of a diesel engine 10, and a feed pump 14 (first pump) connected to the drive shaft 12 for pumping fuel. 2 shows a state rotated by 90"), a crank angle sensor 18 for detecting the crank angle position from the rotational displacement of the pump drive pulley 16 fixed to the drive shaft 12, and a crank angle sensor 18 fixed to the drive shaft 12. gear 2
An engine rotation sensor 22 for detecting the rotational state of the diesel engine 10 from a rotational displacement of 0, an O-crank 28 for driving the pump plunger 26 in cooperation with the face cam 2° 4, and the roller ring 28. a timer piston 30 for controlling the rotational position of the timer piston 30, and a timing control valve (TCV) 3 for controlling the fuel injection timing by controlling the position of the timer piston 30.
2, an electromagnetic spill valve (SPV) 34 for controlling the timing of fuel release from the pump plunger 26, and a fuel cut valve (FC) for cutting fuel when the engine is stopped.
V) 36 and the delivery vibe 3 of this fuel injection pump 8
an injection nozzle 40 for injecting the fuel discharged from 8 into the combustion chamber of the diesel engine 10;
has. In addition, 41 in the figure is the injection nozzle 4.
This is an adjustment resistance for adjusting the injection DA fuel condition from 0. The fuel injection pump 8 is also equipped with an injection rate control device 39 that changes the pilot injection rate by changing the voltage applied to the PZT stack made of PZT elements. The air supply system of the engine 1o includes an intake temperature sensor 46 for measuring the temperature of the air taken in by the compressor 42B of the turbocharger 42 via the air cleaner 44, and an intake air temperature sensor 46 for measuring the temperature of the air taken in by the compressor 42B of the turbocharger 42 via the air cleaner 44. A main intake throttle valve 50 for controlling, an accelerator position sensor (not shown) for detecting an opening degree signal (accelerator signal) of the main intake throttle valve 5o, and the main intake throttle valve 5
an auxiliary intake throttle valve 52 that is parallel to 0 and adjusts the air port;
is provided. The 171 degrees of the iWJ intake throttle valve 52 is controlled by a diaphragm device 54, in which the negative pressure generated by a negative pressure pump (not shown) is connected to a negative pressure switching valve (VSV) 58 or 60. Supplied via An intake pressure sensor 62 for detecting the pressure of intake air is provided downstream of the intake throttle valves 50, 52. In the cylinder head 10A of the diesel engine 1o,
The injection nozzle 40 and glow plug 64 are provided with their tips facing toward the engine combustion chamber 10B. Further, the cylinder block 10C of the diesel engine 10 is equipped with a water temperature sensor 66 for detecting the engine cooling water temperature. The exhaust system of the diesel engine 10 is equipped with a turbine 42A of the turbocharger 42, and the upstream side of the turbine 42A of the turbocharger 42 and the compressor 42 are connected to each other.
The downstream side of B is communicated with through a wastegate valve 68 for preventing an excessive rise in intake pressure. the crank angle sensor 18, the engine rotation sensor 22,
Output signals from the intake temperature sensor 46, accelerator position sensor, intake pressure sensor 62, water temperature sensor 66, etc. are input to a microcomputer 70 that performs various calculation processes and controls the diesel engine 10. As shown in FIG. 3, the microcomputer 7o includes a central processing unit (C
PU) 72, the output of the water Ω sensor 66 inputted via a buffer 74A, the output of the intake air temperature sensor 46 inputted via a buffer 748, the output of the intake pressure sensor 62 inputted via a buffer 74C, Buffer 74D
The accelerator sensor output is input via the buffer 74E, the phase complementary a voltage is input via the buffer 74E, and the buffer 74
A multiplexer 76 for sequentially taking in the τ correction voltage etc. inputted through F, and an analog-to-digital converter (hereinafter referred to as ,A
/D converter) 78. Further, the CPU 72 includes a waveform shaping circuit 80A that shapes the waveform in order to directly take in the rotational speed signal (NE>) output from the engine rotational speed sensor 22, and a reference pulse signal (TDC) output from the crank angle sensor 18. A waveform shaping circuit 80B for capturing, a buffer 74G for capturing the starter signal of the engine 10, a buffer 74H for capturing the operating signal of the vehicle interior air temperature controller (near conditioner), and a torque converter. A buffer 741 for receiving the signal is connected to the CPU 72.Furthermore, the CPU 72 is connected to a drive circuit 82 for driving the fat cut valve (FCV) 36 according to the result of the calculation, A drive circuit 84 for driving the timing v control valve (TCV) 32 according to the result, and a drive circuit 84 for driving the timing v control valve (TCV) 32 according to the calculation result, and the electromagnetic spill valve (SPV) 34 also according to the calculation result.
a current detection port 88A for detecting the current output from the drive circuit 86 and feeding back a detection signal; and a current detection port 88A for detecting a voltage drop in the drive circuit 86. Low voltage detection circuit 88B and CPU 7
A drive circuit 90 for outputting (diagnosis output) the diagnostic result obtained by diagnosing the operating state of the diesel engine in step 2, and a drive circuit 92 for blinking a warning light are connected. The effect of an actual flow example will be explained below. Regarding pilot injection control in this practical example, the first
This will be explained based on the flowchart shown in the figure. First, in step 110, it is determined whether the diesel engine 1O is in a stable idle state. If the determination result is negative, this routine is ended without pilot injection. When the determination result is positive, that is, when the idle is in a stable state, the process proceeds to step 120, and from the rotational fluctuation of each cylinder at the time of trouble, the dispersion of the injection ff4 for each cylinder is calculated as follows, for example. do. That is, the engine rotation sensor 22 obtains an NE raw waveform from the rotational speed signal part, and as shown in FIG. 5”PA (pump angle) (For each 45°CA rotation of the engine, calculate the engine rotation fiNEi (i-1 to 4) at 45°CA rotation of direct + if from the time ΔT required for the rotation of 45°CA. Then, from the engine speed NEi, the rotational fluctuation DNEp (p-1 to
4) is detected, and the average value WND of the rotation fluctuation of the gold cylinder is detected.
As a result, if the rotational fluctuation of the relevant cylinder is smaller than the average value WNDLT, it is assumed that the twisted layer injection rgIa of the relevant cylinder is small, and the difference DONE+) (1) = 1 to 4) is determined. , for example, due to the relationship shown in FIG. 6, 1! A
The twisted layer jet Q4ωΔq to be ffl is learned. On the other hand, if the rotational fluctuation of the relevant cylinder is greater than the average value WNDLT, then 1, the reduced opening Δq of the relevant cylinder is similarly learned. Next, in step 130, according to the variation in the fuel injection range Δq that is to be corrected by increasing or decreasing learned in step 120, the pilot injection start timing (Pi 0 + II tall angle) for each cylinder is adjusted, for example, the Calculated based on the relationship shown in Figure 7. In this case, if the fuel injection port Δq is greater than zero,
The pilot control correction amount is retarded. Next, in step 140, the calculated control oil position is added to the basic pilot injection control value to calculate a command value for the pilot injection timing for each cylinder. In this case, the basic pilot feed tAili control value is a constant value determined in advance based on the cam profile of the face cam 24 of the fuel injection pump 8, the required pilot characteristics, the characteristics of the injection nozzle 40, etc. Next, in step 150, 39 PZT stacks are short-circuited in the injection rate control device of the fuel injection pump 8 for each cylinder based on the calculated command value, and the pilot injection start timing is set to vjlH. This eliminates variations in pilot injection timing from the injection nozzle 40, balances ignition and explosion in each cylinder of the diesel engine 10, and eliminates negative effects caused by variations in twisted layer injection such as rotational fluctuations and crankshaft undulations. be done. In the above embodiment, since the variation in the twisted-layer injection Mm of each cylinder was determined from the rotational fluctuation, this variation could be detected relatively easily. However, the method for determining the variation is not limited to this, and the variation can also be determined by other methods, for example, by detecting the fuel injection rate of the direct cylinder. In the embodiment described above, the fuel I1 is controlled by the injection tJ4 rate control till device 39 having a PZT stack.
1°1 (JJi;i), but the scope of application of the present invention is not limited to this, and may be applied to other fuel injection amount control actuators. It is clear that the invention can be similarly adopted in other diesel engines that control the injection amount. [Effect 1 of the invention] As explained above, according to the present invention, the twisted layer of each cylinder during pilot injection It is possible to eliminate the effects of fluctuations in injection 11Fiffl, such as vibration and noise. Therefore, when pilot injection is performed in a diesel engine, jq
This has the excellent effect of further improving vibration and noise prevention effects.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a routine for controlling pilot injection till to explain the operation of an embodiment of the pilot injection tI+ control method for a diesel engine according to the present invention, and FIG. FIG. 3 is a cross-sectional view that does not show the overall structure of an embodiment of an automotive diesel engine, but includes a partial block diagram; FIG. 3 is a block diagram showing the internal structure of a microcomputer used in the embodiment; FIG. 4 shows a 45-mm
Figures 5 and 6 are diagrams showing how to determine the engine speed for each °GA, and Figures 6 and 7 are diagrams showing how to determine the variation in fuel injection intervals for each cylinder. 2 is a dimensional diagram showing an example of the relationship between the pilot injection control correction port and the fuel injection correction amount used in the routine shown in FIG. 1. FIG. 8... Fuel injection pump, 10... Diesel engine, 18... Crank angle sensor, 22... Engine rotation speed sensor, 32... Timing II + control valve, 34... Electromagnetic spill valve, 39 ... Injection rate control device, 40... Injection nozzle, 70... Microcomputer, 72... CPU.

Claims (1)

[Claims] (1) When pilot injecting fuel into each cylinder of a diesel engine, the variation in fuel injection amount between each cylinder is detected, and based on the detected variation, the pilot injection start timing for each cylinder is estimated. A pilot injection control method for a diesel engine, comprising correcting a pilot injection start timing for each cylinder according to a fuel injection start timing determined by the engine.