JPH0530982B2 - - Google Patents

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 a method for controlling the fuel injection timing of a diesel engine installed in a vehicle such as an automobile. 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, a fuel injection timing control method for electronically controlling fuel injection timing according to the operating conditions of a diesel engine begins with step 101 as shown in FIG.
Then, the basic injection timing Tbase is read out from a two-dimensional data map using the engine speed Ne and engine load L (for example, fuel injection amount Q) as parameters as shown in Fig. 2, and interpolation calculations are performed as necessary. Then, in step 102, a correction coefficient is calculated using the fuel injection amount Q as a parameter as shown in FIG.
Kq is calculated, and then in step 103, a predetermined correction advance amount T(A) is calculated from the intake pressure Pim and engine speed Ne as shown in FIG. 4, and then in step 104 , the injection timing at or immediately after starting, which is usually determined by the engine coolant temperature.
Tsta is calculated, and finally, in step 105, the final injection timing Tfin is determined by the larger of the sum of the above Tbase and the above T(A) and the above Tsta. Here, the correction advance angle amount T
As is clear from Fig. 4, in (A), the smaller the intake pressure Pi is, the larger the value is set, and white smoke, which is particularly likely to occur when driving at high altitudes, can be prevented by increasing the correction advance amount T(A). This is taken into consideration.

However, in this type of control method, the correction advance angle amount T(A)
White smoke can be prevented by increasing as the intake pressure Pim decreases, but on the other hand, knocking tends to occur more easily.

Therefore, it is desirable to set the corrected advance angle amount T(A) to an appropriate value that can suppress the generation of white smoke and reduce knocking. However, an appropriate value for the corrected advance amount T(A) that achieves the above objective has not been obtained for all fuels used.

[Purpose of the Invention] 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. Differently, when using special No. 3 diesel oil, white smoke is less likely to occur, but the correction advance amount T (A)
It has been discovered that if the angle is set as shown in FIG. 4, the angle becomes overadvanced and knocking becomes noticeable.

The reason for this is thought to be that the specific gravity of the special No. 3 diesel oil is lower than that of the No. 2 diesel oil shown in FIG. 5, and incomplete combustion is less likely to occur.

The present invention has been made in view of the above points, and by determining the properties of the fuel used in terms of 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 reduce knocking while suppressing the occurrence of.

[Structure of the Invention] Therefore, the fuel injection timing control method for a diesel engine according to the present invention is as shown in FIG. As shown, the specific gravity of the fuel used is electrically detected (step a), and the larger the detected specific gravity is, the more the correction advance amount of the fuel injection timing is increased (step b). do.

[Operation] As described above, in the present invention, the larger the specific gravity of the fuel used, the greater the amount of correction advance of the fuel injection timing.

Here, as described above, the greater the specific gravity of the fuel used, the more likely it is that white smoke will be generated. Further, if the fuel injection timing is advanced, the generation of white smoke is suppressed, but on the other hand, knocking becomes more likely to occur.

In the present invention, when the specific gravity of the fuel used is relatively small and white smoke is difficult to generate, the advance angle of the fuel injection timing is reduced, so that knocking is reduced without generating white smoke. Further, when the specific gravity of the fuel used is relatively large and white smoke is likely to be generated, the advance amount of the fuel injection timing is increased, so that the generation of white smoke is sufficiently suppressed. The present invention will be explained below with reference to Examples.

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

In this electronic fuel injection control system,
The control circuit 1 has a built-in microcomputer, and the microcomputer detects the operating conditions of the diesel engine through an engine speed sensor 2, an engine load sensor 3, an intake pressure sensor 4, a water temperature sensor 5, and other operating condition detectors 7. In addition to receiving the detection signal from the fuel specific gravity sensor 6, the fuel injection timing is determined according to a predetermined program, and a drive signal corresponding to the determined fuel injection timing is sent to the injection timing adjustment member 8. This injection timing adjusting member 8 outputs an output to the injector 9-.
The injection timing of the fuel injected into the combustion chamber of the diesel engine from 1, 9-2, . . . , 9-n 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 installation. Two air tubes 10 with different tip lengths are fixedly installed in the fuel tank. The difference in air pressure between -1 and 10-2 is converted into an electrical signal by the piezoelectric conversion element 11. In addition, the code 12 in FIG. 7 is a battery, 1
3 represents an ignition switch, and 14 represents other driven parts.

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

In FIG. 9, an injector 17 is attached to a cylinder head 16 of an engine 15, and an electronic fuel injection pump 18 is connected to the high-pressure fuel introduction side of the injector 17. The fuel injection pump 18 is equipped with an injection timing adjustment member 8, that is, a timer mechanism, for determining the start of fuel distribution pressure delivery by the pump plunger 19, and an injection amount adjustment member for adjusting the position of the spill ring 20 to determine the injection amount. 21 is provided.

The injection timing adjustment member 8 is equipped with a timing control valve 23 that controls the flow rate when relatively high-pressure fuel boosted by the feed pump 22 is bypassed to the input side of the feed pump 22, and the timer piston 24 is connected to the high-pressure fuel as described above. The pump plunger 19 is positioned at a position where the force exerted by the return spring 25 is balanced, the phase of the timing roller 26 is determined, and the relative position between the timing roller 26 and the cam disc 27 is changed.
The fuel injection start timing is adjusted by adjusting the distribution pressure feeding timing. The position of the timer piston 24, that is, the fuel injection start timing, is input to the control circuit 1 as an electrical signal by a variable inductance type timer position sensor 28.

On the other hand, the fuel injection amount adjustment 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 amount is adjusted by adjusting the timing of fuel overflow from the pump plunger 19. The position of this spill ring 20, that is, the fuel injection amount is determined by a variable inductance type spill position sensor 3 similar to the timer position sensor 28.
1, the signal is converted into an electrical signal and input to the control circuit 1.

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

Further, the fuel injection pump 18 is provided with a fuel cut valve 32, and the fuel cut valve 32 is actuated by a drive signal from the control circuit 1 to cut off the fuel supply into the pump cylinder 33. .

The control circuit 1 includes a timer position sensor 2 as described above.
8. Each signal from the spill position sensor 31 and the rotation speed sensor 2 is input, and the timing control valve 2
3. It is connected to output a drive signal to the linear solenoid 29 and fuel cut valve 32. Furthermore, the control circuit 1 includes a fuel specific gravity sensor 6 for detecting other operating conditions, a water temperature sensor 5, an intake air temperature 34, an intake pressure sensor 4, an accelerator sensor 35,
Start signal generation circuit 36, air conditioner switch 3
7, a torque converter switch 38, and a battery voltage 39 are connected respectively.

FIG. 10 shows a block diagram showing the electrical connection relationship between the control circuit 1, the above-mentioned operating condition sensor group, and driven parts, including the fuel specific gravity sensor 6,
Water temperature sensor 5, intake temperature sensor 34, intake pressure sensor 4, accelerator sensor 35, spill position sensor 3
1. Each detection signal from the timer position sensor 28 is sent to the buffers 40 to 44 or the sensor signal detection circuit 4
The analog signal selected by the multiplexer 47 is converted into a digital signal by the A/D converter 48, and is input into the CPU 50 via the input/output port 49. . Note that sensor drive circuits 45 and 51 are connected to the spill position sensor 31 and the timer position sensor 28, respectively. In addition, the start signal generation circuit 36 and the air conditioner switch 3
7.Turkey converter switch 38 each has a buffer of 5
It is connected to another input/output port 56 via ports 3 to 55. In addition, the battery voltage 39 is
If an abnormality occurs in the battery voltage, the power abnormality detection circuit 58 detects this abnormality and outputs the linear solenoid 2.
A control signal is input to a drive circuit 59 of 9 and a drive circuit 60 of the fuel cut valve 32. In addition, the rotation speed sensor 2 is connected to the waveform shaping circuit 61.
It is connected to the CPU 50 via the CPU 50 so that the CPU 50 handles interrupts. Further, an analog ECU 62 is connected to the waveform shaping circuit 61, and failure detection is performed in this analog ECU 62. Input/output port 4
9 and 56 are backup via common bus 63.
RAM64 including RAM, ROM65 and CPU50
is connected to. The CPU 50 executes processing according to a program stored in advance in the ROM 65, outputs a control signal according to the processing result to the drive circuit 66, drives the timing control valve 23, and similarly controls the fuel via the drive circuit 60. cut valve 32
It also outputs a control signal to the D/A converter 67 and drives the linear solenoid 29 via the servo AmP 68 and the drive circuit 59. Also, A/D converter 48, input/output port 49,
D/A converter 67, input/output port 56, CPU5
A clock (timer) 69 is connected to clock 0 to determine processing timing in each section.

FIG. 11 is a flowchart showing one embodiment of the main processing according to the present invention among the processing by the CPU 50.

In this first embodiment, it is first determined in step 201 whether or not it has just been started, and if it has been immediately after starting, in step 202 the specific gravity ρ of the fuel is calculated based on the signal from the fuel specific gravity sensor 6 using the following formula: Calculated from ρ=△P/(X-Y)g (where X-Y, △P are the pipe length difference and differential pressure as shown in Figure 8), and in step 203, a correction coefficient Kρ based on the specific gravity ρ of the fuel is calculated. The spill position sensor 3 is calculated in accordance with the characteristics shown in FIG.
The correction coefficient Kq based on the fuel injection amount Q based on the signal from 1 is calculated according to the characteristics shown in FIG. Min[9+Ne/1000×Kq×Kρ−Pim/6
0, Ne/1000+1] (However, 480≦Pim≦1500[mmHg], 0≦T(A)
Calculated from ≦4 [°CA]). Note that this corrected advance angle amount T(A) can be expressed by a characteristic as shown in FIG. Next, in step 206, Tbase is calculated from the two-dimensional map of the engine speed Ne and the fuel injection amount Q, then in step 207, Tsta is calculated, and then in step 208, the fuel injection timing Tfin is finally calculated. is calculated from the following formula: Tfin=MAX[Tbase+T(A), Tsta].

Therefore, for special No. 3 light oil, which has a relatively small specific gravity and does not easily generate white smoke, the correction advance amount T(A)
This can reduce knocking when driving at high altitudes, and since the amount of correction advance T(A) is relatively large for light oil with a relatively large specific gravity, the generation of white smoke when driving at high altitudes can be reduced. Can be suppressed.

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

In this embodiment, instead of calculating the correction coefficient Kρ, an intake pressure Pim' for calculating T(A) used for calculating the injection timing is provided, and according to the specific gravity ρ of the fuel, for example, the following formula, Pim'=Pim+[Ne/50+40 ]×0.833−ρ／0.833
Calculated using −0.809. This equation is the 15th equation that expresses the relationship between the engine speed Ne and the intake pressure difference (Pim' - Pim).
This can be expressed by the characteristics shown in the figure. The corrected advance angle amount T(A) is calculated using the following formula: T(A)=Min[9+Ne/1000×Kq−Pim'/60, Ne/10
00+ 1] (480≦Pim′≦1500[mmHg], 0≦T
(A)≦4[°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 a third embodiment of the present invention.

In this embodiment, the above-mentioned first embodiment is Kρ
Instead of calculating the T(A) used for calculating the injection timing, the engine rotation speed Ne' is set, and depending on the fuel specific gravity ρ, the following formula, for example, Ne'=Ne×0.833−0.809/ Calculated by 2×0.833−(0.809+ρ). Note that this arithmetic expression is as shown in FIG. Then, using Ne′, Pim and Kq, for example, the following formula: T(A)=Min[9+Ne′/1000×Kq−Pim/60,
Ne'/1000+1] (480≦Pim≦1500[mmHg], 0≦T(A)
≦4 [°CA]) Calculate the corrected advance angle amount T(A). That is, the corrected advance angle amount T(A) is as shown in FIG.

Therefore, in this embodiment as well, as in the first and second embodiments, when the specific gravity of the fuel is small, the correction advance amount T(A) is reduced, which reduces white smoke generation and knocking when driving at high altitudes. It becomes possible to achieve this.

[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 detection signal, in which the correction advance of the fuel injection timing increases as the specific gravity of the fuel used increases. The amount of angle has been increased. Therefore, when the specific gravity of the fuel used is relatively small and white smoke is difficult to generate, it is possible to reduce the advance of the fuel injection timing to suppress white smoke and knocking at the same time. Also,
If the specific gravity of the fuel used is relatively large and white smoke is likely to be generated, the amount of advance of the fuel injection timing can be increased to sufficiently suppress the generation of white smoke. Therefore, in the present invention, for any fuel used, it is possible to suppress the generation of white smoke and reduce knocking when driving at high altitudes.

Furthermore, according to the present invention, it is possible to reduce knocking 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 drawings]

Figures 1 to 4 are for explaining the conventional fuel injection timing control method. Figure 1 is a flowchart showing the process, Figure 2 is a two-dimensional map diagram of the basic injection timing, Figure 3 shows the correction coefficient
A characteristic diagram of Kq and FIG. 4 respectively show a characteristic diagram of the corrected advance angle amount T(A). Fig. 5 is a diagram showing the permissible limit characteristics of white smoke emissions that vary depending on the type of light oil focused on in making the present invention, Fig. 6 is a diagram showing the basic configuration of the present invention, and Fig. 7 is A schematic configuration diagram of an electronic fuel injection control system used in realizing the present invention, FIG. 8 is a conceptual diagram of the fuel specific gravity sensor, and FIG. 9 is a concrete representation of the electronic fuel injection control system. 10 is a block diagram showing the electrical connection relationship between the operating condition detector, the control circuit, and the driven part; FIG. 11 is a flowchart showing the first embodiment of the present invention; FIGS. 1st
3 is a characteristic diagram of the correction coefficient Kρ and the correction advance amount T(A) for explaining the first embodiment, and FIG. 14 is a flowchart showing the second embodiment of the present invention.
Figures 15 and 16 show the pressure difference Pim'-Pim and the corrected advance angle amount T(A) for explaining this second embodiment.
FIG. 17 is a flowchart showing the third embodiment of the present invention, and FIGS. 18 and 19 show the engine rotation speed Ne' and the correction advance amount T, respectively, for explaining the third embodiment. A characteristic diagram of (A) is shown.

Claims (1)

[Claims] 1. A fuel injection timing control method for a diesel engine that electronically controls the fuel injection timing in accordance with an engine operating condition detection signal, comprising: electrically detecting the specific gravity of the fuel used; 1. A fuel injection timing control method for a diesel engine, characterized in that the larger the fuel injection timing is, the more the correction advance amount of the fuel injection timing is increased.