JPH0450446A - Idling engine speed control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To minimize fluctuations in the engine speed at the time of idling by controlling the ignition timing and the fuel supply quantity in response to the deviation of an instantaneous value of information on the engine speed from a value obtained by treating the instantaneous value with first-order lag. CONSTITUTION:When an internal combustion engine 12 is controlled to be idled, an electronic control device 40 determines an instantaneous value of information on the engine speed obtained from a crank angle sensor 50 and a value obtained by treating the instantaneous value with first-order lag. Then the electronic control device delays or advances the ignition timing in response to the deviation of both the values, and increases or decreases the fuel supply quantity. Thus, even if the idling engine speed abruptly changes by disturbance, etc., restoring torque can be early generated, and thereby fluctuations in the engine speed at the time of idling can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling the idle speed of an internal combustion engine.

(Prior art) The amount of intake air supplied to the engine during a predetermined idle operation of the internal combustion engine is adjusted according to the deviation between the detected value of the engine rotation speed and the target rotation value, and the idle rotation speed is adjusted to the target rotation speed. A method of controlling the idle rotation speed in the vicinity is known. More specifically, a bypass passage is provided to bypass a throttle valve disposed in an intake passage of an internal combustion engine, and a bypass valve is provided in this bypass passage to adjust the amount of air supplied to the engine via this passage.
For example, when the idle switch indicating the throttle valve is fully closed is on, and a predetermined amount of time has elapsed since the engine was started, during idling operation, the valve opening of the bypass valve mentioned above will change the engine speed. Adjustment is made according to the deviation between the detected value and the target rotation speed, and the idle rotation speed is controlled to be close to the target rotation speed, thereby stabilizing the idle operation.

(Problem to be Solved by the Invention) By the way, a so-called MP1 (Mult
Many i-point injection (i-point injection) type engines are equipped with a large-capacity surge tank in the intake system. In such an engine, when the above-mentioned idle speed control is applied to speed fluctuations, the response of the intake air amount is slow due to the large volume of the intake system, resulting in large speed fluctuations, and in the worst case There is a problem with the engine stalling.

The present invention has been made to solve these problems, and eliminates the inconvenience caused by the delay in response to the amount of intake air.
An object of the present invention is to provide a method for controlling the idle speed of an internal combustion engine, which is designed to suppress rotation speed fluctuations.

(Means for Solving the Problem) According to the present invention, in order to achieve the above object, the amount of intake air supplied to the engine during a predetermined idling operation of the internal combustion engine is determined based on the detected value of the engine rotation speed. In an idle rotation speed control method, the idle rotation speed is controlled in the vicinity of the target rotation speed by adjusting according to the deviation from the target rotation number,
The present invention is characterized in that an instantaneous value of engine rotational speed information and a value obtained by first-order delay processing of the instantaneous value are obtained, and the ignition timing is retarded or advanced according to these deviations, and the fuel supply amount is increased or decreased. A method for controlling idle speed of an internal combustion engine is provided.

(Function) The idle speed control method of the present invention counteracts the influence of the primary response delay of the intake air amount due to the large capacity of the intake system by advancing or retarding the ignition timing and increasing or decreasing the fuel supply amount. This is to correct and suppress fluctuations in rotational speed by increasing or decreasing torque. The magnitude of the primary response delay of the intake air amount is determined by relating the instantaneous value of the engine speed information to the deviation between the instantaneous value and the value obtained by processing the instantaneous value with the primary lag, and the above-mentioned ignition timing and fuel supply amount are adjusted according to this deviation. Adjustments will be made.

(Example) An example of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic configuration of a fuel supply control device for an internal combustion engine according to the present invention, and this control device is applied to, for example, a four-cylinder gasoline engine (hereinafter simply referred to as "engine") 12.

Intake manifold 1 connected to each cylinder of this engine 12
4, an electromagnetic fuel injection valve 16 is disposed adjacent to each intake port. One end of an intake pipe 20 is connected to the intake manifold 14 via a surge tank 18, and an air cleaner 22 is attached to the other end (the end open to the atmosphere) of the intake pipe 20. A throttle valve 24 is disposed in the middle of the intake pipe 20. Fuel whose fuel pressure is adjusted to a constant level by a fuel pressure regulator 26 is supplied to each fuel injection valve 16 from a fuel pump (not shown) via a fuel passage 25.

The intake pipe 20 is provided with a bypass passage 21 that bypasses the throttle valve 24.
A bypass valve 28 is provided. This bypass valve 28 is driven by, for example, a pulse motor to change the valve opening degree, and is connected to an electronic control unit (ECU) 40 described later, and the valve opening degree is controlled by a drive signal from the electronic control unit 40. bypass passage 21
The amount of auxiliary air supplied to the engine 12 via the air pump is adjusted.

On the other hand, an exhaust manifold 30 is connected to the exhaust side of each cylinder of the engine 12.
The atmospheric side end is connected to an exhaust pipe 34. Exhaust pipe 34
A three-way catalytic converter (catalytic exhaust gas after-treatment device) 36 is disposed in the middle of the exhaust gas. An 02 sensor 44 is attached to the exhaust manifold 30 to detect the amount of oxygen in the exhaust gas. The 02 sensor 44 is electrically connected to the input side of the electronic control device 40 and supplies an oxygen concentration detection signal to the electronic control device 40.

An ignition plug 13 is provided in each cylinder, and each ignition plug 13 is connected to an electronic control device 40 via a distributor 38 and an ignition coil 37. When the current supplied to the primary coil of the ignition coil 37 from the drive circuit (not shown) of the electronic control device 40 is cut off, a high voltage is generated in the secondary coil, and this high voltage causes a spark to fly to the ignition plug 13. The air-fuel mixture supplied to the combustion chamber of each cylinder is ignited. Timing to ignite this mixture (
ignition timing) is controlled according to the operating conditions.

Note that during idling, advancing the ignition timing from the standard advance position generally increases engine torque, and retarding it decreases it.

The electronic control device 40 includes a central processing unit (not shown), a control program for executing idle rotation control, calculating fuel supply amount, ignition timing, etc., a storage device for storing various program variables, etc., an input/output device, etc. configured. In addition to ROM and RAM, the storage device includes a non-volatile battery backup RAM whose stored contents do not disappear even after the engine 12 is stopped.

Each of the fuel injection valves 16 described above is electrically connected to the output side of the electronic control device 40, and is opened by a drive signal from the electronic control device 40, and the required amount of fuel is injected into each cylinder as will be described in detail later. Supply injection.

On the input side of the electronic control device 40, there are various sensors for detecting the operating state of the engine 12, such as the above-mentioned 02 sensor 4.
In addition to 4, an air flow sensor 42 is installed near the end of the intake pipe 20 open to the atmosphere and outputs a pulse proportional to the amount of intake air by detecting Karman vortices; The intake air temperature sensor 46 detects the opening of the throttle valve 24, the throttle opening sensor 48 detects the valve opening of the throttle valve 24, and the distributor 38 connected to the camshaft is provided with a predetermined crank angle position at or slightly before top dead center. Crank angle sensor 5 that outputs a pulse signal (TDC signal) every time it is detected
0, also provided in the distributor 38, so that a specific cylinder (for example, the first cylinder) is positioned at a predetermined crank angle position (
For example, a cylinder discrimination sensor 52 that detects whether the engine 12 is at the compression top dead center or a little before the angular position)
An idle switch 56 that detects the fully closed position of the throttle valve 24, an atmospheric pressure sensor 58 that detects the atmospheric pressure Pa, and an air conditioner switch (not shown) that detects the operating state of the air conditioner. ,
Sensors such as a headlamp switch 60 that detects the on/off state of the headlamp and a battery sensor that detects battery voltage are connected, and these sensors supply detection signals to the electronic control unit 40.

The electronic control device 40 determines a predetermined idle operating state, high load operating state, low load operating state, deceleration fuel cut operating state, and 02 feedback control operating state based on the detection signals of the various sensors described above, as will be described in detail later. etc., the fuel injection amount corresponding to the detected engine operating state, that is, the valve opening time TINJ of the fuel injection valve 16, is calculated, and a drive signal corresponding to the calculated valve opening time TINJ is injected into each fuel injection. The fuel is supplied to the valve 16 to open it, and the required amount of fuel is injected and supplied to each cylinder.

The electronic control device 40 calculates the above-mentioned valve opening time TINJ using the following equation (AI).

TINJ=TBxKAFxK+TD ・------
CA1) Here, TB is - the basic valve opening time set according to the intake air amount A/N taken into the cylinder during the intake stroke;
KAF is an air-fuel ratio correction coefficient that is set according to the intake air amount A/N, engine speed Ne, etc., and the details of how to set the value will be described later. K is another correction coefficient, and this correction coefficient includes a correction coefficient set according to the engine coolant temperature TW, a feedback correction coefficient set according to the oxygen concentration detected by the 02 sensor 44, an intake air temperature Ta, This includes a correction coefficient set according to the atmospheric pressure Pa, an acceleration increase correction coefficient set according to the opening speed of the throttle valve 24, a fuel increase correction after fuel cut, an engine start increase correction, and the like. TD is an invalid time correction value set according to the battery voltage.

In addition, since the crank angle sensor 50 outputs a TDC signal every 180 degrees of crank angle, the electronic control device 40
The engine rotation speed Ne can be detected from the reciprocal of the pulse generation interval (stroke period) of this TDC signal. Also,
The electronic control device 40 stores the firing order of the cylinders, that is, the order of fuel supply to each cylinder, and when the above-mentioned cylinder discrimination sensor 52 detects the predetermined crank angle position of the above-mentioned specific cylinder, the next It is possible to determine which cylinder should be injected with fuel.

Next, details of the rotation speed control procedure during idling by the electronic control device 40 described above will be explained with reference to a program flowchart.

FIG. 2 shows a flowchart of the idle rotation speed control routine executed by the electronic control device 40, in which step S
IO to S14 are for determining whether or not the engine 12 is in a predetermined operating state in which it is possible to execute idle speed control. First, in step SlO, it is determined whether a predetermined time (for example, one minute) has elapsed since the engine 12 was started. Immediately after the engine starts, the operation is unstable, and executing rotation speed feedback control may cause problems. In step S12, it is determined whether the idle switch 56 is outputting an on signal. That is, it is determined whether the throttle valve 24 is in a fully open state.

In step S14, it is determined whether the engine speed Ne is within a predetermined upper and lower limit range.

The electronic control unit 40 determines whether all of these conditions are satisfied, and if any of these conditions are not satisfied, the process proceeds to step S.
The routine proceeds to step 16, where the flag value FLGISC is set to 0 and the routine ends. In this case, the bypass valve 28
Idle rotation speed control is not performed. Flag value F
LGISC is a program control variable that stores whether or not idle speed control is being executed, and is used in ignition timing control, air-fuel ratio correction coefficient calculation routines, etc., which will be described later.

On the other hand, if all the above-mentioned conditions are satisfied, the process proceeds to step 318, where idle rotation speed control is executed, and
The flag value FLGISC is set to 1 and the routine ends. As long as all of the above conditions are met,
Step 318 is executed repeatedly.

Although the method of controlling the idle speed is not particularly limited, for example, the valve opening degree of the bypass valve 28 is PID-controlled according to the deviation between the engine speed Ne detected by the crank angle sensor 5o and the target idle speed, and the engine speed is controlled by PID control. The rotational speed Ne is maintained near the target idle rotational speed. The target idle speed is set to an appropriate value depending on, for example, the engine coolant temperature detected by the water temperature sensor 54, the on/off status of the air conditioner switch and headlamp switch, the operating status of the oil pump that supplies hydraulic oil to the power steering, etc. be done.

FIG. 3 shows an ignition timing control procedure for idle stabilization during idle speed control. This routine is
It is executed as part of the main routine that is constantly executed repeatedly. The electronic control device 40 sets the basic ignition timing θ in step S20. This basic ignition timing θB is set by reading out a value corresponding to the engine rotational speed Ne and the intake air amount A/N representing the engine load from the ignition timing map stored in advance in the storage device mentioned above.

Next, it is determined whether the flag value FLGISC is 1, that is, whether the engine 12 is in an operating state in which idle speed control is executed (step 522).
. If the determination result is negative (NO), the process proceeds to step S24, sets the value O to the idle stabilization correction value θID, and proceeds to step 828, which will be described later.

If the determination result in step S22 is affirmative (Yes), an idle stabilization correction value θID is calculated using the following equation (1).

θID=KIDX (NFL Nx)...
... (1) Here, KID is the correction coefficient (control gain), N.

is the instantaneous value of the engine speed Ne, and NFL is the average value of the engine speed Ne (a value subjected to minus order lag processing), and this average value is calculated from the following equation (2).

NyL Fable=KKLXNFLI-1+ (I KFL)
XNR... (2) KKL is a filter constant (0<Kxt<1), and N
F L s-1 and N F L m are the previous value and the current value of the average value.

Note that the idle stabilization correction values θ and D calculated as described above may be limited by comparing their absolute values with a predetermined value so that the absolute values are equal to or less than a predetermined value. In addition, the idle stabilization correction value θ1D was set according to the deviation between the instantaneous value of the engine speed Ne and the value subjected to first-order lag processing, but the pulse of the TDC signal detected by the crank angle sensor 50 is Occurrence interval (
The stroke period) may be used as is, and in this case, the idle stabilization correction values θ and D are set in accordance with the deviation between the instantaneous value of the stroke period and its first-order delayed value.

When the setting of the idle stabilization correction value θ1D is completed, the process proceeds to step 828, and the ignition timing advance value θADV is calculated using the following formula (3).
Calculate by

θADv=θ8+θ1tl (3) The electronic control unit 40 adjusts the ignition timing advance value θA set as described above.
An ignition signal is output to the ignition coil 37 using Dv, and the ignition plug 13 is ignited at the crank angle position corresponding to the set ignition timing advance value θADV. The ignition timing at this time is advanced or retarded by the amount corrected by the idle stabilization correction value θ1D. and,
When the ignition timing is advanced, the torque increases according to the correction value θ1D, and when the ignition timing is retarded, the torque increases according to the correction value θID.
Torque decreases accordingly.

FIG. 4 shows a calculation procedure for an air-fuel ratio correction coefficient for idle stabilization during idle rotation speed control. This routine is also executed as part of the main routine that is constantly executed repeatedly. The electronic control device 40 is
In step S30, the basic air-fuel ratio correction coefficient value KA4
Set.

This basic air-fuel ratio correction coefficient value KAFI is determined from the air-fuel ratio correction coefficient map stored in advance in the storage device mentioned above, based on the engine speed Ne and the intake air amount A/N representing the engine load.
The value corresponding to the value is set by reading.

Next, it is determined whether the flag value FLGISC is 1, that is, whether the engine 12 is in an operating state in which idle speed control is executed (step 532).

If the determination result is negative (No), the process proceeds to step S34, sets the idle stabilization correction coefficient value KID to a value of 1.0, and proceeds to step 838, which will be described later.

If the determination result in step S32 is affirmative (Yes), the idle stabilization correction coefficient value KID is set according to the deviation ΔN (=NFL Nl) between the instantaneous value of the engine speed Ne and the first-order lag-processed value NFL. do. FIG. 5 shows an example of a table of idle stabilization correction coefficient values KID set according to this deviation ΔN. When the engine speed Ne decreases (when the deviation ΔN is a positive value), the engine speed N
When e increases (when deviation ΔN is a negative value),
This will be set to a value that reduces the fuel injection amount.

When the setting of the idle stabilization correction coefficient value KID is completed, the process proceeds to step 838, where the basic air-fuel ratio correction coefficient value KAFB set as described above and the idle stabilization correction coefficient value KI are set.
An air-fuel ratio correction coefficient value KAF is calculated from D using the following equation (4).

KAF=KAFII XKID --(4)
The electronic control unit 40 calculates the valve opening time TINJ by applying the air-fuel ratio correction coefficient value KAF set as described above to the formula (AI).
is calculated, and the amount of fuel corresponding to the calculated valve opening time TINJ is injected and supplied to the engine 12. The fuel supply amount at this time is increased or decreased by the amount corrected by the idle stabilization correction coefficient value KID. When the amount of fuel supplied increases, the engine torque increases accordingly,
When the weight is reduced, it decreases accordingly.

Next, the idle stabilization correction value θ1. Refer to Figure 6 to see how the ignition at the ignition timing corrected by and the supply of fuel amount corrected by the idle stabilization correction coefficient value KID contribute to the increase/decrease in engine torque and the stabilization of the engine speed. and explain.

Now, the time constant of the -th lag is 0.1 (・Vc/(Vc+Vs) from the relationship between the intake system capacity Vs and the cylinder capacity Vc.
), and it is assumed that the air-fuel ratio of the mixture supplied to the engine is kept constant. Under this assumption, when the engine speed Ne decreases by 10% in one stroke, if the intake air amount A/N per intake stroke increases by 10%, the engine torque increases and the engine rotation increases. Although the number Ne will be restored, the actual intake air amount A/N will only increase by about 10X0.1.1% due to the first-order delay in the intake system. If the engine speed Ne decreases by 10% near idle, the stroke cycle detected by the crank angle sensor 50 will be extended by that amount, and the opening time of the intake valve will also be extended. Although N is supposed to increase, it only increases by about 1%. As a result, a 9% air volume shortage occurs, and a similar air volume shortage occurs in the next stroke, and the tendency of the rotational speed to decrease does not stop easily (see FIG. 6(b)).

From the above phenomenon, it can be said that even if the engine speed Ne decreases by 10%, the amount of air actually taken in changes as if the engine speed decreased by only 1% (No. 6 (See figure (a)).

The shortfall in restoring torque can be interpreted as corresponding to the rotational speed of 9%. For this reason, the ignition timing correction value and air-fuel ratio correction coefficient value for idle stabilization are set according to the deviation between the instantaneous value of the engine speed Ne and the value obtained by first-order delay processing. .

Unless the insufficient amount of air is directly injected into the combustion chamber of each cylinder, it is impossible to perform torque correction without delay by operating the valves in the intake system, but ignition timing correction and air-fuel ratio correction follow the intake stroke. This is a correction operation that can be executed without time delay before the expansion stroke (when torque is generated). In order to realize such a correction operation, it is necessary to be able to increase or decrease torque through ignition timing correction and air-fuel ratio correction. A method that controls the air-fuel ratio of the supplied air-fuel mixture to a value on the fuel lean side of the stoichiometric air-fuel ratio)
This is particularly effective for engines in which

It should be noted that the idle speed control device is of course not limited to one that controls the opening and closing of the bypass valve 28 to adjust the amount of intake air as in the present embodiment, and it goes without saying that the idle speed control device is not limited to one that controls the opening and closing of the bypass valve 28 to adjust the amount of intake air, regardless of the amount of depression of the accelerator pedal. The method of the present invention may be applied to a device that adjusts the amount of intake air by forcibly opening and closing a throttle valve at an angle of 4 degrees near its fully closed position.

(Effects of the Invention) As detailed above, according to the idle speed control method for an internal combustion engine of the present invention, an instantaneous value of engine speed information and a value obtained by first-order delay processing of the instantaneous value are obtained, and these values are The ignition timing is retarded or advanced depending on the deviation of It is possible to suppress fluctuations in the rotational speed during operation to a small level, and it is possible to stabilize idling operation.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a block diagram schematically showing the configuration of a control device for an internal combustion engine to which the method of the present invention is applied, and FIG. FIG. 3 is a flowchart of the ignition timing control routine, FIG. 4 is a flowchart of the air-fuel ratio correction coefficient calculation routine, and FIG. 5 is a flowchart of the idle speed control routine to be executed. Figure 6 shows a table of the air-fuel ratio correction coefficient value KID that is set according to the deviation from the value obtained by first-order delay processing of the instantaneous value.
FIG. 2 is a graph showing the relationship between changes in /N over time. FIG. 12... Internal combustion engine, 13... Spark plug, 14...
・Intake manifold, 16...Fuel injection valve, 2o...
- Intake pipe, 24... Throttle valve, 21... Bypass passage, 28... Bypass valve, 37... Ignition coil, 38... Distributor, 40
...Electronic control unit (ECU), 42...Air flow sensor, 44...02 sensor, 48...Throttle opening sensor, 5°...Crank angle sensor, 54...
...Water temperature sensor, 56...Idle switch, 60.
・Headlamp switch. Applicant Mitsubishi Motors Corporation Agent Patent Attorney Kan Nagato Figure 5 Figure 6 Time

Claims (1)

[Claims] During a predetermined idle operation of the internal combustion engine, the amount of intake air supplied to the engine is adjusted according to the deviation between a detected value of engine rotation speed and a target rotation speed, and the idle rotation speed is controlled to be near the target rotation speed. In the idle speed control method, an instantaneous value of engine speed information and a value obtained by first-order delay processing of the instantaneous value are obtained, and the ignition timing is retarded or advanced according to these deviations, and the fuel supply amount is adjusted. A method for controlling the idle speed of an internal combustion engine, characterized by increasing or decreasing the idle speed.