JPS6047845A - Method of controlling fuel injection timing of diesel engine - Google Patents

Abstract

PURPOSE:To prevent generation of white smoke when a vehicle is driven at a highland, by detecting the specific gravity of used fuel, and determing a correction value for the fuel injection timing by using the detected specific gravity of fuel as one of parameters. CONSTITUTION:In operation of an engine, whether the engine is just after starting or not is judged at first by a control circuit 1. In case that judgement is made that the engine is just after starting, the specific gravity rho of fuel is calculated from the output signal of a sensor 6 for detecting the specific gravity of fuel, and a correction factor Krho corresponding to the specific gravity rho of fuel is calculated. Further, a correction factor Kq for the fuel injection quantity Q is calculated from the output signal of a spill position sensor 31, and a correction value T(A) for the fuel injection timing is calculated from the above two correction factors Krho, Kq. Then, a base injection timing Tbase is read out from the fuel injection quantity Q and the engine speed Ne detected by an engine-speed sensor 2 and the final fuel injection timing Tfin is calculated from the base fuel injection timing Tbase, the correction value T(A) and the injection timing Tsta read out from the output of a water-temperature sensor 5 just after starting of the engine.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fuel injection timing control method for a diesel engine installed in a vehicle such as an automobile, and is particularly applicable to the adoption of preventive measures against white smoke generated when driving at high altitudes. The present invention relates to a fuel injection timing control method for a diesel engine that can reduce knocking, which tends to occur, while suppressing the generation of white smoke.

[Prior Art] In general, fuel injection timing is electronically controlled according to the operating conditions of a diesel engine. The JJ timing control method is as shown in FIG. 1. First, in step 101, the basic injection timing T base is set as shown in FIG.
is read from a two-dimensional data map in which the parameters are read out and interpolated as necessary (til-C''), and then in step 102, a correction coefficient K is calculated using the fuel injection mQ as a parameter as shown in FIG. Q is calculated, and then in step 103, a predetermined correction advance angle f2 is determined from the intake pressure Pim and the engine speed NO as shown in FIG.
iT(△) is calculated, and then in step 104, t'?
) 1. Calculate the injection Q'l @ 1111 T sta at or immediately after starting, which is determined by the engine cooling water temperature, and finally in step 105, calculate the final injection timing Tf.
in is determined by the larger of the sum of the above 1N+as(! and the above T(A>) and the above Tsta. Here, the corrected advance angle fiT('A> is the fourth
As is clear from the figure, the smaller the intake pressure Pim is, the larger the value is set, and care has been taken to prevent white smoke, which tends to occur especially when driving at high altitudes, by increasing the correction advance amount T(A). ing.

However, in this type of control method, white smoke can be prevented by increasing the corrected advance angle ff1T(Δ) as the intake pressure Pim decreases, but there is a problem in that knocking is more likely to occur.

"Purpose of the Invention" By the way, as a result of studying the correlation between white smoke and knocking, the inventor found that the intake pressure at which the concentration of white smoke reaches the allowable limit varies greatly depending on the properties of the fuel used, as shown in Figure 5. ,
It has been found that when using special No. 3 light oil, white smoke is less likely to be generated, but when the corrected advance angle ff1T(A) is set as shown in FIG. 4, the over-advanced angle becomes noticeable and non-king appears.

The present invention has been made in view of the above points, and by determining the properties of the fuel used based on its specific gravity and determining the correction advance amount T<A> according to the properties of the fuel used, white smoke can be reduced when driving at high altitudes. The purpose is to suppress the occurrence of static knocking.

[Structure of the Invention] Therefore, the fuel injection timing control method for a diesel engine according to the present invention is as follows: FIG. As shown in step a), the specific gravity of the fuel used is detected electrically, and the detected ratio is set as the parameter 1.
The present invention will be described below with reference to an embodiment, which is characterized in that the correction advance amount for the fuel rlr5 timing is determined (step b).

[Embodiment] FIG. 7 shows a block diagram of an electronic fuel injection control system used in realizing the present invention.

In this electronic fuel control system, a control circuit 1 has a built-in microcomputer, and the microcomputer includes an engine speed sensor 2, an engine load sensor 3, an intake pressure sensor 4, and a cooling water temperature sensor for detecting operating conditions of the diesel engine. In addition to receiving detection signals from the sensor 5 and other operating condition detector 7, the fuel injection timing is determined according to a predetermined program based on the detection signal from the fuel specific gravity sensor 6. A corresponding drive signal is output to the injection timing adjustment member 8, and the injection timing adjustment member 8 controls the injectors 9-1, 9-2,
..., 9-n so that the injection timing of fuel injected into the combustion guide of the diesel engine is adjusted. As conceptually shown in FIG. 8, the fuel specific gravity sensor 6 is a bubble tube type hydrometer which is good in terms of cost and ease of mounting, and is fixedly installed inside the fuel tank and consists of two air tubes with different tip lengths. 10-1 and 10-2 is converted into an electric signal by the piezoelectric conversion element 11. In FIG. 7, reference numeral 12 represents a battery, 13 represents an ignition switch, and 14 represents a driven portion thereof.

FIG. 9 shows a block diagram specifically representing the electronic fuel injection control system.

';ts In Figure 9, the injector 17 is removed from the shilling head 16 of the engine 15.
A doublet type fuel injection pump 18 is connected to the high-pressure fuel introduction side of the three-wheel injector 17. The fuel injection pump 18 is provided with an injection timing adjustment member 8' for determining the start of fuel distribution pressurization at the pump plunger +719. In other words, an injection amount adjustment member 21 is provided with a timer mechanism and is used to adjust the position of the spill ring 20 to determine the injection amount.
Ii6 is obtained.

The injection timing adjustment member 8 is equipped with a timing control valve 23 that controls the outflow when the relatively high pressure fuel 1, which has been pressurized by the feed pump 22, is bypassed to the input side of the feed pump 22. , the timer piston 24 is positioned at a position where the force exerted by the high-pressure fuel return spring 25 as described above is balanced, and the phase of the timing roller 26 is determined.
By changing the relative position, the distribution pressure feed start timing of the pump plunger 19 is adjusted, thereby adjusting the fuel injection start timing. The position of the timer piston 24, that is, the fuel IEtII start timing is determined by the variable inductance type timer position sensor 2.
8, the signal is input to the control circuit 1 as an electrical signal.

On the other hand, the fuel injection amount adjusting section 21 includes a linear solenoid 29, and the solenoid 29 adjusts the position of the spill ring 20 via a link mechanism 30.
The fuel injection is adjusted by adjusting the timing of fuel overflow from the engine.

The position of the spill ring 20, that is, the fuel injection amount, is converted into an electrical signal by a variable inductance type spill position sensor 31 similar to the timer position sensor 28, and is input to the control circuit 1.

Further, the fuel injection pump 18 is equipped with a rotation speed sensor 2 for detecting the engine rotation speed, and the rotation speed sensor 2 is composed of a rotor 2a, which is an inductor, and an electromagnetic pickup 2b.

Furthermore, the fuel injection pump 18 has a fuconyl cut valve 3.
2 is provided, and in response to a drive signal from the control circuit 1, this fuconyl cut valve 32 is actuated to cut off the fuel supply into the pump cylinder 33.

The control circuit 1 receives signals from the timer position sensor 128, spill position sensor 31, and rotational speed regulators 1 and 2 as described above, and also inputs signals to the timing control valve 23, linear solenoid 29, and the gear unit 1 to valve 32. The drive signal is connected to the drive signal. Furthermore, the control circuit 1 includes a fuel specific gravity sensor 6 for detecting other operating conditions, and a water? j
%'L? sensor 5, intake temperature sensor 34, intake pressure sensor 4
, accelerator sensor 335, start signal generation circuit 36,
An air conditioner switch 37, a torque converter switch 38, and three battery voltages are connected to each other.

FIG. 10 is a block diagram showing the electrical connection relationship between the control circuit 1, the above operating condition sensor group, and driven parts, including the fuel specific gravity sensor 6, water temperature sensor 5, intake air temperature sensor 34, Each detection signal from the barometric pressure sensor 4, the accelerator sensor 35, the spill position sensor 31, and the timer position sensor 28 is connected to the multiplexer 47 via a buffer 77=1.0-/14 or a sensor signal detection circuit 45,46. The analog signal selected at 47 is converted into a digital signal by an A/D converter 48, and is then taken into the CPU 50 via an input/output port 49. The spill position sensor 31 and the timer position Wit laser 28 each have a sensor drive circuit 51.5.
2 are connected. Also, a start signal generation circuit 36,
The air conditioner switch 37 and the torque converter switch 38 are connected to other input/output ports via buffers 53 to 55, respectively.
It is connected to the. Also, 3 battery voltages are buffer 5
When an abnormality occurs in the battery voltage, the power abnormality detection circuit 58 detects this abnormality and outputs a drive circuit 59 for two near solenoids.
, a control signal is input to the drive circuit 60 of the Fuconyl cut valve 32.

In addition, the rotation speed sensor 2 is connected to the CPU via a waveform shaping circuit 61.
50, and the CPU 50 handles interrupts. Further, an analog ECU 62 is connected to the waveform shaping circuit 61, and fail detection is performed in this analog ECU 62. Input/output capos 1 to 49.56 are connected to RAM 64 including backup RAM, ROM 65 and CPU via common bus 63.
50 are connected. The CPU 50 executes processing according to a program stored in advance in the ROM 65, and sends a control signal according to the processing result to the drive circuit 66 to drive the timing control valve 23, and also sends a control signal to the drive circuit 66 to drive the timing control valve 23. It drives the valve 32, outputs a control signal to the D/A converter 67, and outputs a control signal to the servo A m P 68.
Two linear solenoids are driven through five J-dynamic circuits.

1. : A/D converter 48, input/output capo-1 49,
A clock (timer) 69 is connected to the D/A converter 67, input/output capos 1 to 56, and CPU 50.
Rurudokoro J[! The timing is determined J: I'm confused.

FIG. 11 is a flow chart showing one embodiment of the main processing related to the present invention among the processing performed by the CPU 50.

In this first embodiment, it is first determined in step 201 whether or not it has just started, and if it is just after starting, step 201 is carried out.
02 from the fuel specific gravity sensor 6 (however, X-Y, △P
are calculated from the pipe length difference and differential pressure as shown in FIG. The correction coefficient KQ based on the fuel injection amount Q based on the signal from 31 is calculated according to the characteristics not shown in FIG. ≦1500 [mm1-19]
, 0≦T(A>≦4 [6CAI). Note that this corrected advance angle ff1T, (A) can be expressed by a characteristic as shown in FIG.

Next, in step 206, Tbase is set to engine speed N.
e and fuel injection ff1Q from a two-dimensional map, then in step 207 Tsta is calculated, and then in step 208 the fuel injection timing Tfin is finally determined by the following formula: Tfin = M'AX [Tbase+T (△) ,
−rsta ].

Therefore, since the correction advance angle ff1T (△) can be kept small for special No. 3 diesel oil, which has a relatively small specific gravity and does not easily generate white smoke, it is possible to reduce knocking when driving at high altitudes, and the specific gravity is relatively small. Since the corrected advance angle ff1T(Δ) is relatively large in the case of large light oil, it is possible to suppress the generation of white smoke during high-altitude driving.

FIG. 14 is a flowchart showing a second embodiment of the present invention.

In this embodiment, instead of calculating ρ as a correction coefficient, the intake pressure Pi11- for the T(Δ) cylinder used for calculating the injection timing is calculated according to the following formula, for example, according to the specific gravity ρ of the fuel. This equation can be expressed by the characteristics shown in FIG. 15, which shows the relationship between the engine speed Ne and the intake pressure difference (Pim--Pim). and corrected advance angle ff1
T(A) is expressed by the following formula (where 480≦Pim-≦
1500 [mm1-IQ].

051 block A)≦=1. ['CA]), and this characteristic is as shown in FIG.

Therefore, in this embodiment as well, the same effects as in the first embodiment described above can be obtained.

FIG. 17 is a flowchart showing the third embodiment of the present invention.

In this embodiment, instead of calculating ρ as in the first embodiment described above, T(A) is used for calculating the injection timing.
17 The engine rotational speed Ne' is calculated according to the specific gravity ρ of the fuel, for example, using the following equation. Note that this arithmetic expression is as shown in FIG. And this Ne
- and Pim and Kq, for example, the following formula (where 480≦pim≦1500 [mm1-1o
1, 0≦T(A)≦4°CA]) Calculate the corrected advance angle ff1T(A). In other words, the corrected advance angle IT (Δ) is as shown in FIG. 19.

Therefore, in this embodiment as well, when the specific gravity of the fuel is small, as in the first and second embodiments, the correction advance angle ff1T(A
> is reduced, it is possible to reduce white smoke generation and knocking at the high-altitude entrance 1.

[Effects] As explained above, the present invention provides a fuel injection timing control method for a diesel engine that electronically controls the fuel injection timing according to an engine operating condition f1 detection signal, in which the specific gravity of the fuel used is electrically detected. The corrected advance angle (m) for fuel injection timing is determined using the determined specific gravity as one of the parameters.As a result, the advance angle can be reduced with light oil, which has a relatively small specific gravity and is less likely to generate white smoke, thereby reducing knocking when driving at high altitudes. In addition, since the advance angle is set to be relatively large for light oil with a relatively high specific gravity that tends to generate white smoke, the amount of advance is set to be relatively large as before, suppressing the generation of white smoke when driving at high altitudes. I can do a lot of things.

Furthermore, according to the present invention, since knocking can be reduced during high-altitude driving as described above, it is also possible to extend the life of the engine and improve the driving feeling.

[Brief explanation of the drawing]

Figures 1 to 4 are for the purpose of explaining the conventional fuel injection timing control method. Figure 1 is a flowchart showing the process, Figure 2 is a two-dimensional map of the basic injection timing, and Figure 2 is a two-dimensional map of the basic injection timing. FIG. 3 shows a characteristic diagram of the correction coefficient Kq, and FIG. 4 shows a characteristic diagram of the correction advance angle IT<A>. Fig. 5 is a diagram showing the permissible white smoke 171 emission limit characteristics that differ depending on the type of light oil that was focused on in developing the present invention, Fig. 6 is a diagram showing the basic configuration of the present invention, and Fig. 7 is a diagram showing the present invention. Electronic fuel S'31 injection control system used to realize
+A schematic configuration diagram of the system, Figure 8 is a conceptual diagram of the fuel ratio sensor, Figure 9 is a configuration diagram specifically representing the electronic fuel injection control system, and Figure 10 is the operating condition detector and A block diagram showing the electrical connection relationship between the control circuit and the driven part, FIG. 11 shows the first embodiment of the present invention. Correction coefficient 1<ρ, correction advance angle ff1T for explaining the embodiment
(△) characteristic diagram, FIG. 14 is a flowchart representing the second embodiment of the present invention, and FIGS. 15 and 16 are pressure difference p im'-p im and correction for explaining this second embodiment. A characteristic diagram of advance angle ff1T(A>, FIG. 17 is a flowchart representing the third embodiment of the present invention, and FIGS. 18 and 19
The figures show characteristic diagrams of the engine rotational speed Ne' and the corrected advance angle ff1T(Δ), respectively, to explain the third embodiment. Agent: Patent Attorney Tsutomu Sadate (Yoka 1) Figure 1 Figure 5 Ne 288 Figure 6 Figure 15 Ne Figure 16 Pim mmHg Figure 18 Figure 19, 2 mmHg 293-

Claims (1)

[Claims] In a diesel engine fuel injection timing control method for electronically controlling fuel injection timing according to an engine operating condition detection signal, the specific gravity of the fuel used is electrically detected, and the detected specific gravity is A fuel injection timing control method for a diesel engine, characterized in that a correction advance amount of fuel injection timing is determined as one of the parameters.