JPS62150052A - Pilot injection control method for electronically controlled diesel engine - Google Patents

Abstract

PURPOSE:To prevent a large torque fluctuation at the switching point between pilot injection and normal injection by augmenting the command value of the fuel injection quantity in advance at the time of performing pilot injection. CONSTITUTION:The CPU 56A of an engine control device calculates the injection quantity command value based on signals of a rotating speed sensor 46 and an accelerator opening sensor 20. Next, pilot injection conditions are judged, and if the engine rotating speed and injection quantity command value are predetermined values or less and the conditions are judged to be met, the pilot injection quantity is set to a value compensating the injection quantity decreased by the operation of a pilot injection device 54 based on the pump fuel temperature via a sensor 54 or the engine water temperature via a sensor 40. Next, the injection quantity command value and pilot injection quantity are added to generate the final injection quantity command value. Accordingly, the fuel injection quantity is not abruptly decreased during pilot injection, and a torque fluctuation and deterioration of drivability can be prevented.

Description

[Detailed description of the invention]

[Industrial Application Field] This defense relates to a pilot injection control method for an electronically controlled diesel engine. A variable volume control is provided in the plunger high pressure chamber of an injection pump suitable for use in an electronically controlled diesel engine for automobiles, and in a predetermined pilot injection region, the variable volume replenishment is performed at a predetermined time during fuel pumping in a predetermined pilot injection region. Improvement of a pilot l1cl injection control method for an electronically controlled diesel engine in which the volume of the plunger is increased to 111 to lower the pressure in the plunger high pressure chamber, thereby temporarily interrupting fuel injection and performing bi-L1 injection. Regarding. (Conventional technology) In general, diesel engines are used by young people due to the problem of aging.
Particularly when idling, rapid combustion tends to cause loud combustion noise and disturbances. In order to prevent this and reduce the emission of NOx, which is a harmful component in exhaust gas,
11 Q=low before I (i's pilot fuel is
Q 04 L, the ignition delay of the main injected fuel was reduced by XQ to perform slow combustion.
0725, JP-A-54-50726, JP-A-59-14
1735, etc. However, all of these conventional techniques are 11jl
Q (Applying back pressure to the needle valve that constitutes the valve, and controlling the timing when the back pressure is turned to the low pressure side using an electromagnetic on-off valve) 5/l-50726) or to control pilot injection with a cam shape (Japanese Patent Application Laid-Open No. 59-1/1735),
It has problems such as being disadvantageous in terms of responsiveness and under high pressure, or being unable to perform highly accurate control. On the other hand, a technique for controlling the rate by providing a variable volume constriction including an accumulation piston in the high-pressure constriction of the plunger of an injection pump (see Japanese Unexamined Patent Application Publication No. 59-3161, Japanese Unexamined Patent Application Publication No. 59-59)
No. 12131 and Japanese Unexamined Patent Publication No. 18249/1983. Therefore, it is conceivable to combine the chanting rate control technology using these accumulation pistons with the pilot injection technology described above. As shown in FIG. 7, the pilot injection device 53 is constructed by using Δ as an actuator for the accumulation screws 1 to 53B, and the piezoelectric element By shortening the generation of , the piezoelectric element is contracted, the volume of the variable volume 42M integrated with the plunge 17 is increased, and the injection is temporarily interrupted as shown in FIG. In this case, it is expected that highly accurate Pyrowers 1 to 1li1 law control 211 will be possible. In Figure 7, there is jJ3, 53C is the casing, 53
D is a book spring, 56 is an electronic control unit (hereinafter referred to as ECU), 56Y is a drive circuit for the piezoelectric element VI layer body 53A, and 57 is a power source thereof.

[Problems to be solved by the invention]

However, when pilot injection is performed with the device shown in Fig. 7, as shown in Fig. 8, during pilot injection (solid line A
), compared to normal injection (broken line B), the amount of fuel M corresponding to the area of the shaded area is 1'l rr! I1. Fl iff decreases. Therefore, for this pilot, 'J C1
If fuel is spilled at the same timing as normal injection at 1 o'clock, the injection amount will drop significantly during pilot injection, resulting in torque fluctuations at the switching point from normal injection to pilot injection This has the problem of being undesirable in terms of security. Also, pressure? 'Il? When the temperature of the element increases, the same charge iQ
Shrinkage tr'! , becomes large, the total volume of the plunger high-pressure constriction becomes large at high temperatures, and the pressure horn of the plunger high-pressure blank becomes dull. Like, Practical QJ
It also has the problem of further decreasing speed. J3, in order to solve this problem, the 1 hour injection time in 1988-12131 was changed to -0 for the injection time at idle.
Set the spill ring order n to lengthen it to 1 (1
5, it is disclosed that this lengthens the injection time without reducing the injection time during idling operation, but as in the present invention, the pilot injection [11 o'clock l1111! J
It was not possible to effectively compensate for the decrease in lffl alone. [Objective of the Invention j] The present invention was made to solve the above-mentioned conventional problems, and the fuel +10 injection maximum does not change suddenly at the switching point between the normal patrol area and the pilot injection area, and therefore,
An object of the present invention is to provide a pilot injection control method for an electronically controlled diesel engine that does not deteriorate drivability due to torque fluctuation. [Means for solving the problem 1''] The present invention provides a variable volume chamber in the high pressure air of the plunger of an injection pump, and in a predetermined pilot injection region, the variable volume is Fig. 1 shows a pilot injection control method for an electronically controlled diesel engine in which pilot injection is performed by temporarily interrupting fuel injection by increasing the volume and lowering the pressure of the plunge 17 to the high pressure. As shown in the summary, when performing the pilot patrol 1, the fuel injection amount command ("(
The above objective was achieved by increasing the weight in advance so that jJ3<. [Effect 1] In the present invention, the above-mentioned electronically controlled till day
When controlling the pilot injection of the ZEL engine, the command value of the fuel injection amount is increased in advance when pilot IQIJ is performed. Therefore, the fuel injection amount does not drop suddenly during pilot injection, and the fuel injection rate does not change significantly at the switching point between normal injection and pilot injection. Therefore, torque fluctuation does not occur and drivability does not deteriorate. [Example 1] With reference to the drawings below, pilot singing DI according to the present invention
ill? An example of an electronically controlled diesel engine for automatic small use in which the i1 method is adopted will be described in detail. 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. The intake 'f
Downstream of the iA sensor 12, there is a turbine 14A rotated by the thermal energy of the exhaust gas;
A turbocharger r14 consisting of a compressor 14B that is rotated by one motion is provided. The upstream side of the turbine 14Δ of the turbocharger 14 and]
The downstream side of 4B is communicated via a wastegate valve 15 for preventing intake pressure from rising excessively. 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, for restricting the flow m of intake air when the vehicle is idling. The opening degree of the accelerator pedal 17 (referred to as the accelerator opening degree) ACC+'1 is detected by the 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 10A of the diesel engine 10,
An injection nozzle 34 whose tip faces the engine combustion chamber 10B, a glow plug 36, and a spark 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 THW. Fuel is fed under pressure to the injection nozzle 34 from an injection pump 42 . The injection pump 42 is connected to the crank l? of the diesel engine 10. ih rotation) ■ Pump drive 'llll1l/12A that is moved and rotated, and a feed pump 42B for pressurizing fuel that is fixed to the pump drive shaft 42△ (
Figure 2 shows the 90° unfolded state. I'), a fuel pressure adjustment valve 42G for adjusting the fuel supply pressure, and 1) a pump drive pulley 42D fixed to the pump drive @42A.
In order to detect the crank angle base t ((position HH7, for example, top dead center < TDC) from the rotation degree 1t of
Similarly, a convex gear 42E is fixed to the pump drive shaft 42A.
NE for detecting engine speed etc. from rotational displacement of
An engine rotation sensor 7I6 that outputs pulses and is composed of, for example, an electromagnetic pink-up, an IC-th roller ring 42H that reciprocates the face cam 42F and the plunger 42G, and changes the timing thereof, and rotation of the roller ring 42H. Timer piston 4 for changing position
2J (FIG. 2 shows a 90° expanded state), 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 a spill boat 42K. By changing the timing of fuel release from the plunger 42G through the fuel control! ■A spill control valve 50 for controlling
A fuel cut valve 52 for cutting off fuel and a delivery valve 42 for preventing fuel backflow and 197B leakage.
1-, a (14-component pilot injection device 53) as shown in FIG. A glow current is supplied to the glow plug 36 via a glow relay 37. 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.
Crank angle reference sensor '44, engine rotation sensor 46
, the fuel temperature sensor 54, the glow current sensor 55 that detects the glow current flowing through the glow plug 36, the key switch, the air conditioner switch, the neutral safety switch output, the vehicle speed signal, etc. are input to the ECtJ56 and processed, and the output of the ECU 36. According to the VSV28.3
0, glow relay 37, TCV48, spill control valve 50
, fuel cut valve 52, pilot injection rJJ device 5:3, etc. are controlled. As shown in detail in FIG. 3, the ECU 36 includes a central processing unit (hereinafter referred to as CPtJ) 56A for performing various calculation processes, and a read-only memory (hereinafter referred to as CPtJ) for storing control programs, various data, etc. A random access memory (hereinafter referred to as RAM) 56C for temporarily storing calculation data etc. in the CPU 56A, a clock 56D for generating a clock signal, and a buffer. The output of the water temperature sensor 710 is input via 56E, the output of the intake air temperature sensor 12 is input via buffer 56F, and the buffer 5
6G, the output of the accelerator position sensor 20 that is input via the buffer 56H, the output of the fuel temperature sensor 54 that is input via the buffer 56J, etc. Multiplexer (J, 1. lower, MP X, !l: name t 8 )
56 K, output to the MPX 56/l) An analog-to-digital converter (hereinafter referred to as an A/D converter) 56L for converting an analog signal into a digital signal, and the A/D converter 56L.
An input/output port 56M for taking the output of the converter 56L into the CP (J56A), a starter signal input through the buffer 56N, an air conditioner signal input through the buffer 56P, and a torque converter input through the buffer 56Q. The ignition timing inputted via the signal and waveform shaping circuit 56R is input to the input/output port 56S for taking in the output of the fuser 38 etc. to the CPU 56A, and the output of the spark timing sensor 38 is shaped into a waveform and outputted to the CP jJ. The waveform shaping circuit 5 for directly inputting to the input interrupt terminal ICAP2 of '56A.
6R and the same input interrupt terminal ICAP2 of the CPU 56A by shaping the output of the crank angle reference sensor 44 into a waveform.
a waveform shaping circuit 56T for directly inputting the output to the CPL 156A; a waveform shaping circuit 56U for shaping the output of the engine rotation sensor 46 and directly inputting it to the CPL 156A as an NE pulse; A drive circuit 56V for driving the spill control valve 50, a drive circuit 56W for driving the TCV 4B according to the calculation result of the CPIJ 56A, and a drive circuit 56W for driving the fuel cut valve 52 according to the calculation result of the CPU 56A. 1) Connect the drive circuit 56X for driving the pilot monitoring device 53 and the respective component devices to transfer data and commands according to the calculation results of the CPU 56A; A common bus 56Z has been planted for this purpose. Here, the ignition signal output from the waveform shaping circuit 56R is
In addition to the input interrupt terminal ICΔP2 of PLI56A,
The reason why it is also input to the input/output port 568 is to distinguish it from the reference position signal output from the waveform shaping circuit 56T, which is input to the same input interrupt terminal ICAP2. The effects of the embodiment will be explained below. The pilot injection control and the calculation of the final injection amount command value Q fin in this embodiment are executed according to a routine in the main routine as shown in FIG. That is, first, in step 110, the engine rotation speed Ne and the accelerator opening degree A are determined using the relationship shown in FIG.
Injection command 1st shift Qfin- is calculated from ccp. Next, the process proceeds to step 112, where, for example, the engine speed vlN
Determine whether or not the pilot duty conditions in which e is a low rotation of 1200 rpm or less and the injection amount command value Qfin- is 2Qmm3/S (low load or less) are satisfied. If the determination result is negative , proceed to step 114;
Prohibits pilot injection and causes normal injection to occur. This is because the pilot injection has no effect under conditions other than the above-mentioned pilot injection conditions, and in terms of the reliability of the actuator (piezoelectric element) of the pilot l-uQ[H device 53, the fewer the number of operations, the better. Next, the process proceeds to step 116, where the pilot is increased t. The value Qpi is set to zero so that no pilot increase is performed. On the other hand, if the determination result in step 112 is positive and it is determined that the pilot injection conditions are satisfied,
Proceed to step 120 and permit pilot injection. Next, the process proceeds to step 122, where a pilot increase value Qpi is calculated from the pump fuel temperature THF or the engine water temperature THW using, for example, the relationship shown in FIG. This pilot width IIQpi is the pilot injector 53
This value is set to compensate for the decrease in injection amount due to the operation of the engine. After step 116 or 122 is completed, the process proceeds to step 124, where the injection amount command value Qfin' and the pilot increase value Qpi are added as shown in the following equation, and the final nll weight command value r
Subtract 1q in. Qfin<−Qfin−+Qpi −−−−・−
(1) In this embodiment, pilot increase ΦIiT[Q
Since pi is changed according to the fuel temperature T I-I F in the pump or the engine water 'f AT +- I W, when the temperature increases, especially for the actuator of the pilot injection device 53, the It is suitable for those using piezoelectric elements where shrinkage becomes large. Note that the present invention is not limited to this, and is of course effective even if it has a pilot control device that does not use a piezoelectric element as an actuator. In the above embodiments, the present invention was applied to an electronically controlled automobile diesel engine with a turbocharger in which the fuel injection valve was controlled by a spill control valve, but the scope of application of the present invention is limited to this. It is clear that the same law can also be applied to general diesel engines in which the injection amount is controlled by a fuel injection color control actuator other than a spill control valve. [Effects of the Invention] As explained above, according to the present invention, the fuel injection amount does not suddenly decrease during pilot injection. Therefore, there is an excellent effect that the injection m does not change significantly at the switching point between the pilot injection and the normal injection, causing torque fluctuations or deteriorating drivability.

[Brief Description of the Drawings] Fig. 1 is a flowchart showing the gist of the pilot injection control method for an electronically controlled diesel engine according to the present invention, and Fig. 2 is a flow chart showing the gist of the pilot injection control method for an electronically controlled diesel engine according to the present invention. FIG. 3 is a cross-sectional view that does not show the entire structure of the embodiment but includes a partial block diagram; FIG. 3 is a block diagram showing the 1.1.1 structure of the electronic control unit used in the embodiment; Figure 4 is a flowchart of the main routine for controlling pilot injection and determining the final injection amount command value, and Figure 5 is a flowchart showing the engine speed and accelerator opening used in the routine. degree and injection amount command fi
FIG. 6 is a diagram showing an example of the relationship between i'i and FIG. FIG. 8 is a sectional view including a partial block diagram without showing an example of the configuration of the pilot injection device used as an actuator.
Plunger lift when pilot injection is controlled by a pilot injection control device using a piezoelectric element stack,
FIG. 3 is a diagram showing an example of the relationship between high pressure chamber pressure, piezoelectric element generated voltage, and injection rate. 10...Diesel engine, 20...Accelerator position sensor, ACCD...Accelerator opening degree, 42...Injection pump, 42G...Plunger, 46...Engine rotation sensor, Ne...Engine rotation Number, 5o... Spill control valve, 53... Pilot control device, 56... Electronic control unit (ECU), Qfin -
···injection! ■Command, Qpi...Pilot increase value, Qrin...Final injection rAm command 1st shift.

Claims (1)

[Claims] (1) A variable volume chamber is provided in the plunger high pressure chamber of the injection pump, and in a predetermined pilot injection region, the volume of the variable volume chamber is increased at a predetermined time during fuel pumping to reduce the pressure in the plunger high pressure chamber. In the pilot injection control method for an electronically controlled diesel engine in which pilot injection is performed by temporarily interrupting fuel injection, when performing the pilot injection, the command value for fuel injection is increased in advance. A pilot injection control method for an electronically controlled diesel engine, characterized in that: