JPS6371542A - Idle revolution speed control for diesel engine - Google Patents

Abstract

PURPOSE:To control revolution with high precision without generating hunting in idling by controlling the fuel injection quantity according to the nonsensitive region formed for the aimed idle revolution speed. CONSTITUTION:In an ECU 56, the idle operation state of a Diesel engine is judged. When the average number of engine revolution NEV detected by an engine revolution speed sensor 46 is within the nonsensitive region NF+ or - NF which is set by the aimed number of revolution NF which is previously set and the revolution speed range NF which is allowable in the upper and lower regions of the aimed number of revolution, the fuel injection quantity is not varied. When the average number of engine revolution NEV is outside the nonsensitive region NF+ or - NF, the actual engine revolution speed is set to control the fuel injection quantity by increasing and decreasing the detected engine revolution speed within the revolution speed range ANF so that the fuel injection quantity does not become discontinuous. Therefore, the actual engine revolution speed does not vary discontinuously from the aimed engine revolution speed, and the discontinuous change is not generated also in the fuel injection quantity.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for controlling the idle speed of a diesel engine, and particularly to a method for controlling the idle speed of a diesel engine, which is suitable for use in controlling the idle speed of a diesel engine equipped with an electronically controlled fuel injection pump. Regarding improvements.

[Prior Art] In a diesel engine equipped with an electronically controlled distribution type fuel injection pump, there is a technology for controlling the idle speed, for example, which the applicant has already proposed in Japanese Patent Publication No. 60-55697.
There is a method for electronically controlling the idle speed of a diesel engine disclosed in the above publication. In this control method, the error between the target idle rotation speed and the actual rotation speed is detected, and the fuel injection amount is adjusted so that the pattern of the fuel injection amount fA relative to the predetermined idle rotation speed is shifted in parallel according to the detected error. By correcting the pattern parameters and performing feedback control of the fuel injection amount according to the values of the parameters, the idle speed is kept constant. Similarly, in Japanese Patent Laid-Open No. 124045/1984, a method for controlling the idling speed of an internal combustion engine is proposed. In this rotational speed control method, if the difference between the engine idling rotational speed and a predetermined idling rotational speed is within a rotational speed range of 2 ORPM or less, the actual engine is within the target idle rotational speed zone. Since the rotational speed is not included, the amount of air flowing through the bypass passage connecting the upper and downstream parts of the throttle valve is not feedback-controlled, and when the rotational speed is not included in the above-mentioned rotational speed range, the amount of intake air is adjusted with a time delay of one step at a time. Hunting during idle rotation can be prevented by increasing or decreasing the idle rotation speed. [Problems to be Solved by the Invention] However, when the electronic rotational speed control method proposed in the above-mentioned Japanese Patent Publication No. 60-55697 is adopted and controlled for a direct injection diesel engine, the idle rotational speed becomes unstable and hunts. This problem arises. The causes of such problems can be considered as follows. In other words, if a specific irregular injection occurs in a direct-injection diesel engine, temporarily (for example, at a crank angle of 45° CA)
There are times when the rotational speed (calculated separately) decreases and the amount of fuel injection increases instantaneously depending on the governor pattern. and,
Because of this instantaneous increase, the engine speed increases and the injected fuel decreases in the next cycle. It is thought that hunting occurs during idling due to such repeated increases and decreases in the amount of injected fuel. In order to solve the above problem, the above-mentioned Japanese Patent Application Laid-Open No. 57-124045
It is conceivable to adopt the control method disclosed in the publication. However, if this control method is used to control a gasoline engine, the fuel amount is feedback-controlled according to the intake air amount, so it is sufficient to control the intake air amount, but in a diesel engine, only the intake air amount is controlled. Therefore, it is impossible to directly adopt the control method described in the above publication, and even if Even if the fuel injection mQ can be controlled by this control method, there is a problem as follows. Namely, as in the governor pattern not shown in FIG. Within the rotational speed zone (indicated by the symbol Z one in the diagram), the fuel amount DI and the amount Q are kept constant as indicated by the symbol A in the diagram, and no feedback control is performed.On the other hand, as the engine rotational speed decreases, If it falls off, in order to prevent the engine from stopping, the fuel injection is started with a time delay of 1 step according to the above control method.
Q is difficult to control. Therefore, the amount of fuel injection mQ is quickly increased according to the governor pattern. The point below the zone is the point indicated by the symbol B in the figure, and in this case, the fuel injection mQ rapidly increases from the symbol A to the symbol B in the figure.
As a result, the engine speed increases, exceeding the upper limit of the zone and causing hunting. Conversely, if the engine speed deviates above the zone, the opposite phenomenon occurs and the fuel injection amount Q suddenly decreases at a point J, not indicated by the symbol C in the figure, which also causes hunting. Wake up and put away. Therefore, in the past, the amount of fuel increased smoothly without any hunting during idling. 1) There was a problem that lffl could not be controlled.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and provides a method for controlling the idle speed of a diesel engine that can accurately control the diesel engine to a predetermined idle speed without causing hunting during idle. The purpose is to

[Means to solve the problem]

The present invention is a method for controlling the idle speed of a diesel engine, which controls the amount of fuel injection based on the actual engine speed so that the engine speed at idle becomes a predetermined target idle speed. As shown in
setting a predetermined dead band region in the target idle rotation speed;
The engine speed detected during idling is averaged, and if the averaged engine speed is within the dead band region, the fuel injection amount is not changed, and if it is outside the dead band region, the fuel injection amount is The above object is achieved by: 1) increasing or decreasing the detected engine rotation speed by the value of the dead zone so that the injection amount does not become discontinuous, and calling it the actual engine rotation speed; [Operation] In the present invention, in the idle speed control method for a diesel engine, a dead band region is set in the target idle speed, and the engine speed detected during the idling is averaged, and the averaged engine speed is If the engine speed is within the dead zone, the fuel injection amount is changed; if it is outside the dead zone, the detected engine speed is changed so that the fuel injection amount does not become discontinuous. The value is increased or decreased to determine the actual engine speed for controlling the fuel injection fA stone. Therefore, if the engine speed is outside the dead band region, the actual engine speed for controlling the fuel injection amount will not change discontinuously from the target engine speed, so the fuel injection amount will no longer change discontinuously. . Therefore, the diesel engine can be accurately controlled to a predetermined idle speed without causing hunting during idle. Therefore, conventionally, when performing idle control of a diesel engine with irregular injection, such as a direct injection diesel engine, various delivery valves or a reduction in the pump oil feed rate, etc. are used to suppress the irregular injection. However, with the present invention, there is no problem in idle speed control even with mild irregular injection, so injection systems with high output and low fuel consumption can be used. Specifications can be adopted. In addition, since it can be operated smoothly when idling, it is possible to lower the rotation speed of the diesel engine and achieve low fuel consumption. In addition, since the present invention makes it possible to easily set the governor pattern during idle, it is necessary to adapt the governor pattern described in +iQ, which was conventionally done to prevent problems under various conditions, and took a lot of effort and time. It will no longer be considered as such. [Example] Hereinafter, an example of an electronically controlled diesel engine for automobiles in which the method for controlling the idle speed of a deep-pil engine according to the present invention 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. 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. A waste gate valve 1 is provided on the upstream side of the turbine 14A of the turbocharger 14 and on the downstream side of the compressor 14B to prevent excessive rise in intake pressure.
5. 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, in order to limit the flow rate of intake air when the vehicle is idling. 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 SV) 28 or 30. 11. An intake pressure sensor 32 for detecting the pressure of intake air is provided downstream of the intake throttle valve 18 and 22 shown on the right. In the cylinder head 10A of the diesel engine 10,
An injection nozzle 3/11 and a glow plug 36 are provided, the tip of which faces the engine combustion chamber 10B. Moreover, the cylinder block 10C of the diesel engine 10
includes a water temperature sensor 4 for detecting engine cooling water temperature.
0 is provided. Fuel is fed under pressure from the injection pump 42 to the injection nozzle 11n. The injection pump 42 includes a pump drive shaft 42A that rotates in conjunction with the rotation of the crankshaft of the diesel engine 10, and a feed pump 42B (for pressurizing fuel) that is fixed to the pump drive shaft 42A.
FIG. 2 shows the crank angle reference position from the rotational displacement of the pump drive pulley 42D fixed to the pump drive shaft 42A, the fuel pressure adjustment valve 42C for adjusting the fuel supply pressure (FIG. For example, the engine rotation speed is detected from the reference position sensor 44, which is made of an electromagnetic pickup, for example, to detect the top dead center (TDC), and the rotational displacement of the gear/1.2E, which is also fixed to the pump drive shaft 4.2A. an engine rotation speed sensor 46 made of an electromagnetic pickup, for example, a roller ring 42H for reciprocating the face cam 42F and the plunger 42G, and changing the timing thereof;
Timer piston 4.2 for changing the rotational position of H
A timing control valve (hereinafter referred to as TC) that controls the injection timing by controlling the position of the timer piston 4.2
) 48 and an electromagnetic spill valve 50 for controlling the fuel injection port by varying the timing of fuel relief from the plunger 42G via the spill port 42K.
, a fuel cut valve 52 for cutting fuel, and a delivery valve 42L for preventing fuel backflow and double stacking.
It is equipped with. A glow current is supplied to the glow plug 36 via a glow relay 37. The intake temperature sensor 12, the accelerator position sensor 201, the intake pressure sensor 32, the water temperature sensor 40, the reference position sensor 44,
The engine speed sensor 46, the glow current sensor 54 that detects the glow current flowing through the glow plug 36, the gear switch, the air conditioner switch, the neutral safety switch output, the vehicle speed signal, etc. are controlled by an electronic control unit (hereinafter referred to as ECU) 56. input and processed, the EC
Output of U36, nQ VS V 28.3
o1 glow relay 37, TCV48, electromagnetic spill valve 50
°Fuel cut valve 52 etc. are controlled. As shown in detail in FIG. 3, the ECU 36 includes a central processing unit (hereinafter referred to as CPU) 56A for performing various calculation processes, and a read-only memory (hereinafter referred to as CPU) for storing control programs, various data, etc. , a random access memory (hereinafter referred to as RAM) 56C for temporarily storing data calculated by the CPU 56A, a clock 56D for generating a clock signal, and a buffer 56E. The output of the water temperature sensor 40 is input via the buffer 56F, the output of the intake air temperature sensor 12 is input via the buffer 56F, the output of the intake pressure sensor 32 is input via the buffer 56G, and the accelerator position sensor is input via the buffer 56H. A multiplexer (hereinafter referred to as
MPX) 56, an analog-to-digital converter (hereinafter referred to as A/D converter) 56L for converting an analog signal output to the MPX 56 into a digital signal, and an output of the A/D converter 56L. The input/output port 56M is used to input the information into the CPU 56A, and the starter signal input via the buffer 56N, the air conditioner signal input via the buffer 56P, the torque converter signal input via the buffer 56Q, etc. are input to the CPU 56A. and an input/output port 568 for inputting input signals to the CPU 56A by shaping the output of the reference position sensor 44 and inputting the input interrupt baud 1 to ICAP2 to the CPU 56A.
a waveform shaping circuit 56T for directly inputting the output to the CPU 5;
6A, and a waveform shaping circuit 56U for directly capturing the signal into the C.
A drive circuit 56V for driving the electromagnetic spill valve 50 according to the calculation result of the CPU 56A, a drive circuit 56W for driving the TCV 48 according to the calculation result of the CPU 56A, 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 for driving the fuel cut valve 52, and a common bus 56Y for connecting each component to transfer data and commands. The effects of the embodiment will be explained below. FIG. 4 shows a routine for determining the corrected rotation speed NEP for controlling the idle rotation speed of the diesel engine 10. In other words, in the routine shown in the figure, a timer (not shown) built into the ECU 36 body is used to determine the corrected rotation speed NEP for a certain period of time, e.g. Step 110 is entered every 50 milliseconds. Next, in step 120, whether or not the diesel engine 10 is in an idling state is determined based on, for example, the accelerator opening degree ACCI.
)-〇(idle switch ON>, vehicle speed-〇1, starter switch is OFF, etc.).
Proceed to. On the other hand, if the determination result is positive, that is, the engine is in an idling state, the process proceeds to step 130, where the detected engine speed NE is set in a dead band region where the detected engine speed NE is set within a preset target speed NF and an allowable speed range ΔNF above and below the target speed NF. It is determined whether the upper limit of NF±ΔNF (hereinafter referred to as upper limit rotation speed) exceeds NF+ΔNF. In this case, as shown in the following equation (1), the determination is made based on whether or not the value NEV obtained by averaging a plurality of detected values of the engine rotation speed NE (hereinafter referred to as the average rotation speed) is larger than the lower limit rotation speed NF + ΔNF. . NEV>N F+4N F - (1) If the judgment result is negative, that is, the average rotation speed NEV is equal to the upper limit rotation speed NF.
If it is less than +ΔNF, the process proceeds to step 140. In step 140, the average rotational speed NEV is determined by the dead zone area NEV.
Lower limit of F±ΔNF (hereinafter referred to as lower limit rotation speed) NF-
Whether or not it is less than or equal to ΔNF is determined as shown in the following equation (2). N E V < N F −ΔN F ・(2
>If the determination result is negative, that is, the average rotational speed NEV is larger than the lower limit rotational speed NF=ΔNF, the process proceeds to step 180. On the other hand, if the determination result in step 130 is positive, the process proceeds to step 150, and in the main routine to be described later, the corrected engine speed NEP used for compensating the detected engine speed NE is calculated using the following formula. As in (3), add a predetermined minute rotational speed ΔNE and set it as the new corrected rotational speed NE.
Put it in P. -] b- NEP+to 8 NEs +NEP (3) On the other hand, if the determination result in step 140 is positive, that is, if the average rotational speed NEV is equal to or less than the lower limit rotational speed NF-ΔNF, the process proceeds to step 160. In step 160, the minute rotational speed ΔNE is subtracted from the corrected rotational speed NEP as shown in the following equation (4), and is set as a new corrected rotational speed NEP. NEP-ΔNE-)NEP...<4)
In addition, since the constant rotational speed ΔNE increases or decreases from the corrected rotational speed NFP at fixed time intervals (50 m5 in the embodiment) through the processing in steps 150 and 160, the engine rotational speed tends to fall into the dead zone region. After the processing in steps 150 and 160 is completed, in step 170, 1 is set in the flag Xl5C and the flag
Perform processing to set up l5C. This processing indicates that the average rotational speed NEV is out of the dead zone area NF±ΔNF, and this corrected rotational speed NEP determination routine is ended. On the other hand, in step 180, the average rotational speed NEV
is within the dead zone 1ii1iNF±ΔNF, or the engine is in a state other than idling, the routine proceeds to a process of setting zero to the flag X1SC and clearing the flag X15G, and then executes a routine for determining the corrected rotation speed NEP. end. FIG. 5 is a flowchart showing the main routine for controlling the fuel injection amount Q during idling. That is, in step 210, it is determined whether the diesel engine 10 is in an idling state, and if it is not in an idling state, the process proceeds to step 270. On the other hand, the idle state Togi proceeds to step 220, where it is determined whether or not the aforementioned flag
Go to 0. On the other hand, if the flag X1SC is not cleared and remains standing (xlSC-1), the process proceeds to step 230, and the detected engine speed NE at idle is equal to the target engine speed NF.
From the detected engine speed NE to the target speed N
It is determined whether the value NE-NF obtained by subtracting F is greater than zero. When the determination result is negative, that is, when the value is NE-NF<0, the process proceeds to step 240, and the engine speed NE plus the allowable speed range ΔNF is calculated as D, as shown in the following equation (5). Put it in the register. NE+ΔNF-+D (5) On the other hand, when the determination result is positive, that is, when the value is NE-ΔNF≧○ and the engine speed NE is off upward, the process proceeds to step 25'O; As shown in the following equation (6), the allowable range ΔNF is subtracted from the engine speed NE and the result is stored in the D register. NE-ΔNF-+D (6) On the other hand, if the flag X1SC is not set in the previous step 220, in step 260, the target rotational speed NF is entered in the D register, and the process proceeds to step 270. Next step 2
The process also proceeds to step 270 when it is determined in step 10 that the device is not in the idle state, or when the processing in steps 240 and 250 is completed. In step 270, the corrected rotational speed NEP is added to the value of the D register obtained as described above to obtain the corrected rotational speed NE', as shown in the following equation (7). D+NEP-+NE' (7) Next, in step 280, fuel injection faQ is determined. In this step 280, the fuel injection ff1Q is changed to h0
Corrected rotation speed NE' and accelerator opening A CCI
) (not shown) using a relationship map as shown in FIG. Next, at step 290, a duty ratio for fuel spill corresponding to the determined fuel injection fMQ is determined, and at step 300, the determined duty ratio is output, and this main routine ends. Next, the results of controlling the fuel injection ♀Q by the above-mentioned idle speed control routine and main routine will be explained based on FIGS. 7 and 8 while comparing with the conventional method. FIG. 7 shows an example in which the fuel injection ff1Q is controlled by a conventional method in which the idle speed control routine and the main routine are not executed. The same figure (A) shows the change in the rotation speed NE of the diesel engine, and the same figure (B) shows the change in the fuel injection C
) shows the change in IffiQ. If irregular injection occurs in the shaded area indicated by symbol e in the same figure (A) and almost no fuel is injected, the calculated fuel injection 1jffiQ is constant but the actual fuel injection amount is small, so Engine speed NE decreases temporarily. Then, as the engine speed decreases, the fuel injection amount Q is increased as shown in FIG. 7(B) according to the governor pattern not shown in FIG. 9 mentioned above. however,
Since the irregular injection is a one-shot event, in the next combustion cycle, the actual injection amount is restored and at the same time, the fuel injection amount Q is increased as described above, so that the actual rotational speed NE increases. Further, as the engine speed NE increases, the amount of fuel injection fliikQ is reduced according to the governor pattern. Hunting occurs due to repeated increases and decreases in the fuel injection amount Q as described above. On the other hand, when fuel injection mQ is controlled by the method of the present invention using each of the above routines, FIG. 8(A)
As shown in the figure, even if a single irregular injection (indicated by symbols e1 and e2 in the figure) occurs and the actual engine speed NE temporarily decreases, the engine speed for determining the fuel injection faQ cannot be changed. By setting the engine speed to the average engine speed NEV, the amount of decrease in the engine speed becomes small. In addition, as shown in Figure (B), a dead band area NF±ΔNF with an upper limit (NF + ΔNF) and a lower limit (NF - △NF) is set for the target rotation speed NF. The rotational speed NEP and the corrected engine rotational speed NE' shown in <D> in the figure do not change, and therefore the fuel injection foot Q is determined by the governor pattern shown in FIG. 6, for example. The values are the same as shown in E). Since the irregular injection is recovered in the next combustion cycle, it is possible to maintain a constant engine speed during idling. On the other hand, if the average rotational speed NEV is outside the upper or lower limit of the dead band region, problems such as engine stop will occur, but in this case, as shown in Figure 9, the fuel injection amount Q is determined by the normal governor pattern. By doing so, it is possible to prevent such problems. Further, when the engine speed NF' changes from the dead zone region to outside the dead zone region, step 24 of the main routine is executed so that the fuel injection amount Q does not change suddenly.
At 0.250, the target rotational speed is shifted by a predetermined amount ΔNF, so that the fuel @Dj amount Q changes smoothly. The reason for shifting ΔNF by a predetermined amount is that the fuel injection rJUfJi Q calculated by the governor pattern based on the engine rotational speed NF that is outside the dead zone region 11i, NF4-ΔNF
and the fuel injection calculated from the target engine speed NF within the dead zone region! This is to prevent hunting from occurring due to an excessively large difference between the actual injection amount and the actual injection amount. In addition, in steps 150 and 160, in order to easily return the target rotation speed NF to the dead zone area NF±ΔNF, the correction rotation speed NEP is increased by a minute rotation speed ΔNE, and a series of processes of the idle rotation speed routine are performed. I am trying to shift it every millisecond. Thereby, the role of returning the engine speed NF to within the range can be enhanced, as if the proportional term when controlling the fuel injection amount Q was changed. In addition, in the above embodiment, the present invention is applied to the electromagnetic spill valve 5.
However, the scope of application of the present invention is not limited to this, and is applicable to fuel injection control actuators other than electromagnetic spill valves. It can be similarly applied to general diesel engines. [Effects of the Invention] As explained above, according to the present invention, an excellent effect can be obtained in that the diesel engine can be accurately controlled to a predetermined idle speed without causing hunting during idle.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the gist of the present invention, FIG. 2 is a sectional view including a partial block diagram showing the overall composition of an embodiment of an electronically controlled diesel engine for automobiles in which the present invention is adopted, and FIG. FIG. 3 is a block diagram showing the configuration of the electronic control unit l- used in the embodiment, and FIG.
FIG. 5 is a flowchart showing a routine for determining the corrected rotation speed for controlling the idle rotation speed, and FIG. 6 is a flowchart showing a routine for controlling the fuel injection amount. Figure 7 (△), (
B) is a diagram showing an example of changes in the engine speed and fuel injection DJ ffi when the fuel injection amount is controlled by the conventional method, and FIGS. FIG. 9 is a diagram showing an example of changes in the engine rotation speed, average rotation speed, corrected rotation speed, corrected engine rotation speed, and fuel injection amount when the fuel injection amount is controlled by controlling the engine rotation speed. FIG. 3 is a diagram illustrating an example of a governor pattern for determining a fuel injection amount for a fuel injection amount. DESCRIPTION OF SYMBOLS 10... Diesel engine, 42... Injection pump, 46... Engine rotation speed sensor, NE... Engine rotation speed, 50... Electromagnetic spill valve, 56... Electronic control unit (ECU).

Claims (1)

[Claims] (1) In a diesel engine idle speed control method that controls the fuel injection amount based on the actual engine speed so that the engine speed at idle becomes a predetermined target idle speed, the target idle speed is set to a predetermined target idle speed. A dead zone area is set, the engine speed detected during idling is averaged, and if the averaged engine speed is within the dead zone area, the fuel injection amount is not changed and the engine speed is outside the dead zone area. In this case, the method for controlling the idle speed of a diesel engine is characterized in that the detected engine speed is increased or decreased by the value of the dead zone so that the fuel injection amount does not become discontinuous to obtain the actual engine speed. .