JPS6282251A - Idling speed feedback control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To shift an engine into a feedback control smoothly by opening a control valve when the deceleration of the engine exceeds a specified one so as to feed supplemental air to the engine. CONSTITUTION:The plural number of discriminating engine speeds is provided to an ECU 9 is a speed range between a specified engine speed higher than an engine speed at which a feedback control starts, and a target idling speed. If deceleration exceeds the discriminating engine speed when the engine speed detected by an engine speed sensor 14 while being decelerated intersects the discriminating engine sped, a control valve 6 is set at a specified valve opening duty ratio so as to feed supplemental air to the engine 1 through both an air passage 8 and an air intake pipe 3 for a period of the time, which is the sum of the time determine by the discriminating speed and deceleration, and the time determined by the value corresponding to the amount of loading of an electric apparatus 16, and is corrected by a correction value which is determined by both atmospheric pressure detected by an atmospheric pressure sensor 15 and the variation with time in characteristics of an engine (1) performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an idle speed feedback control method for an internal combustion engine, and more particularly to an idle speed feedback control method for preventing engine stall when the engine suddenly decelerates to idle. .

(Technical Background of the Invention and Problems Thereof) Conventionally, the control amount, that is, the valve opening time, of a control valve that adjusts the amount of auxiliary air supplied to the engine via an auxiliary air passage that bypasses the throttle valve of the engine intake system has been The idle speed feedback control detects the difference between the target idle speed set according to the engine load condition and the actual engine speed, and determines the difference depending on the size of the difference so that this difference becomes zero. method is known.

Further, in such a feedback control method, a discrimination rotation speed is set higher than the starting rotation speed of the feedback control,
When the engine decelerates toward the feedback control starting rotation speed, the degree of change in the engine rotation speed at the discrimination rotation speed is detected, and the valve opening time of the control valve is determined according to the thus detected value and the value of the discrimination rotation speed. is determined, and the control valve is opened for the valve opening time thus determined, thereby supplying the engine with the amount of auxiliary air required when the engine suddenly decelerates into the feedback control region, thereby preventing engine stall. A shot air control method has been proposed (Japanese Patent Application No. 59-267508).

However, as described above, if the opening time of the control valve during sudden deceleration into the engine idle speed feedback control region is determined only according to the degree of change in engine speed and the discrimination speed value, the performance characteristics of the engine itself If there are changes over time or variations between engine production lots,
Alternatively, when the engine oil is replaced, the amount of auxiliary air supplied by the control valve and the amount of auxiliary air actually required by the engine may differ significantly, resulting in a decrease in engine speed. A rise or fall occurs, making it difficult to smoothly shift the engine to the idle speed feedback control region.

(Purpose of the invention) The present invention was made to solve the above problems.
When the engine suddenly decelerates to the idle speed feedback control area, the engine smoothly transitions to the feedback control area and quickly achieves a stable idle speed, regardless of changes in engine performance characteristics over time. An object of the present invention is to provide an idle rotation speed feedback control method that can control the idle speed.

(Structure of the Invention) In order to achieve such an object, according to the present invention, an air filter is provided in an auxiliary air passage that bypasses a throttle valve in an intake system of an internal combustion engine, and is supplied to the engine via the auxiliary air passage. In an idle rotation speed feedback control method that performs feedback control of a control valve that adjusts an auxiliary air amount according to a deviation between a target idle rotation speed and an actual engine rotation speed, a predetermined determination rotation speed is set higher than a starting rotation speed of the feedback control. detects the engine rotation speed, determines whether the engine rotation speed has decreased across the predetermined determination rotation speed during deceleration of the engine toward the feedback control start rotation speed, and determines whether the engine rotation speed has decreased by crossing the predetermined determination rotation speed; detecting the degree of deceleration of the engine speed when the number of rotations decreases across a predetermined value, and when the degree of deceleration thus detected is greater than a predetermined value, determining the opening time of the control valve according to the control amount used for the feedback control. There is also provided an idle rotation speed feedback control method for an internal combustion engine, characterized in that the control valve is opened over the valve opening time determined in this manner.

(Example of the invention) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram schematically showing the entire engine speed control device for an internal combustion engine to which the method of the present invention is applied. Reference numeral 1 indicates a four-cylinder internal combustion engine, for example,
An intake pipe 3 and an exhaust pipe 4 having an air cleaner 2 attached to their open ends are connected to the . A throttle valve 5 is arranged in the middle of the intake pipe 3, and an air passage 8 that opens into the intake pipe 3 downstream of the throttle valve 5 and communicates with the atmosphere is arranged.

An air cleaner 7 is attached to the open end of the air passage 8 on the atmosphere side, and an auxiliary air amount control valve (hereinafter simply referred to as "control valve") 6 is disposed in the middle of the air passage 8. This control valve 6 is a normally closed electromagnetic valve, and is composed of a solenoid 6a and a valve 6b that opens an air passage 8 when the solenoid 6a is energized. connected.

A fuel injection valve 10 is provided between the engine 1 of the intake pipe 3 and the opening 8a of the air passage 8, and this fuel injection valve 10 is connected to a fuel pump (not shown) and electrically connected to the ECU 9. It is connected.

A throttle valve opening (θTH) sensor 11 is installed in the throttle valve 5, and an intake pipe absolute pressure (PEA) is connected to the intake pipe 3 via a pipe 12 downstream of the opening 8a of the air passage 8 of the intake pipe 3. Sensor 13.

Engine speed (Ne) sensor 14 on the engine 1 body
However, there is an atmospheric pressure (PA) sensor 1 outside the air cleaner 2.
5 are respectively attached, and each sensor is electrically connected to the ECU 9. The Ne sensor 14 sequentially generates a crank angle position signal (hereinafter referred to as "rTDC signal") at a crank angle position a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder.
The DC signal is supplied to the ECU 9.

Reference numeral 16 indicates an electrical device such as a headlight, an electric radiator fan, a heater fan, etc., one terminal of which is connected to a connection point 17a via a switch 16a, and each other terminal is grounded. A regulator 19 that supplies field winding current to the generator 18 according to the load of the battery 17, the alternator 18, and the electric device 16 is connected in parallel between the connection point 17a and the ground. The field current output terminal 19a of the regulator 19 is connected to the field current input terminal 18a of the generator 18 via the power generation state detector 20.
It is connected to the. The power generation state detector 20 supplies the ECU 9 with a signal 1 indicating the power generation state of the generator 18, for example, a signal E having a voltage level corresponding to the magnitude of the fielder m current supplied from the regulator 19 to the generator 18. do.

The generator 18 is mechanically connected to an output shaft (not shown) of the engine 1 and is driven by the engine 1 . When the switch 16a is closed (on), power is supplied from the generator 18 to the electrical device 16, and if the power required to operate the electrical device 16 exceeds the power generation capacity of the generator 18, there will be a shortage. The power for this is supplemented from the battery 17.

Throttle valve opening sensor 11, absolute pressure sensor 13, Ne
Engine operating parameter signals from the sensor 14 and atmospheric pressure sensor 15 and a power generation status signal from the detector 20 are supplied to the ECU 9. The ECU 9 shapes these input signal waveforms, corrects the voltage level to a predetermined level,
The input circuit 9a has functions such as converting analog signal values into digital signal values, and the central processing circuit (rCPU)
9b, a storage means 9c for storing various calculation programs and calculation results executed by the CPU 9b, and an output circuit 9d for supplying drive signals to the fuel injection valve 10 and control valve 6.

Then, the ECU 9 determines the engine operating state and the engine load state such as electrical load based on the engine operating parameter signal value and the power generation state signal value, and sets the target idle rotation speed during idling operation according to these determined states. At the same time, the amount of fuel supplied to the engine 1, that is, the opening time of the fuel injection valve 10, and the amount of auxiliary air, that is, the valve opening duty ratio DouT of the control valve 6, are respectively calculated, and the fuel injection valve is adjusted according to each calculated value. A drive signal for operating the control valve 10 and the control valve 6 is supplied to each via the output circuit 9d.

The solenoid 6a of the control valve 6 is energized for a valve opening time corresponding to the calculated valve opening duty ratio, opens the valve 6b, and opens the air passage 8, so that the required amount of auxiliary air according to the valve opening time is released. It is supplied to the engine 1 via the air passage 8 and the intake pipe 3.

The fuel injection valve 1o is opened for a valve opening time according to the above-mentioned calculated value and injects fuel into the intake pipe 3, and the injected fuel is mixed with intake air to create a mixture with a desired air-fuel ratio in the engine 1. is being supplied to.

When the amount of auxiliary air is increased by lengthening the opening time of the control valve 6, the amount of air-fuel mixture supplied to the engine 1 increases, the engine output increases, and the engine speed increases. Conversely, control valve 6
If the valve opening time is shortened, the amount of air-fuel mixture supplied will decrease and the engine speed will decrease. By controlling the amount of auxiliary air, that is, the opening time of the control valve 6, the engine speed during idling can be controlled.

Next, the idle speed control method according to the present invention will be explained with reference to temporal changes in the engine speed Ne and the valve opening duty ratio Dour of the control valve 6 shown in FIG.

First, the engine speed Ne is set between the predetermined engine speed NA and the target idle speed upper limit No. Second. Third discrimination rotation speed NSA, N5A2°NsA,
The difference in engine speed detected before and after the crossing point, that is, the deceleration rate Δ
Detect Na. This deceleration amount ΔNe is the predetermined judgment value ΔN
When it is larger than S A, the time TSAM determined by the crossed discrimination rotation speed and deceleration amount ΔNe, and the electric device 16
The time TsA is determined by the value DH depending on the size of the load.
Calculate the time equal to the sum of E and the thus calculated time,
The valve opening duty ratio of the control valve 6 is corrected by a correction value xDX contribution EF determined according to changes over time in the performance characteristics of the engine 1, the auxiliary air amount control valve 6, etc. according to the present invention, and the valve opening duty ratio of the control valve 6 is adjusted over the thus corrected time TEA. DouT is set to a predetermined value DSA (for example, 100
%, for example, 80% depending on the opening area of the control valve 6), and control for supplying an auxiliary air amount to the engine (hereinafter referred to as "shot air control") is executed.

More specifically, first, the engine is in a deceleration state with the throttle valve fully open, and the engine speed Ne is equal to the predetermined speed NA.
(time t□ in Figure 2), the valve opening duty ratio Dour of the control valve 6 is controlled by feedback control (when the engine speed decelerates along the solid line a in Figure 2, tta to t).
When decelerating along the dashed line C for 14 time points, from t8 to □When decelerating along the broken line C for 4 time points, from t1□ to t1
Initial value (DXRE
F+DE) is set to XKPAD (Figure 2 (B))
. Then, the engine speed Ne is the solid line a in Fig. 2 (A).
When decelerating along the slow deceleration line shown by , the engine speed Ne is at the time (ts)? (ts)? (The first, second, and third discrimination rotation speeds NSA□, NsA, respectively)
, , each time when it drops across N5A3,
The deceleration amount ΔNe of the rotational speed when crossing each of the discrimination rotational speeds NsA□, NSA, N5A3 is determined, but this deceleration amount ΔNe shows a value smaller than the predetermined discrimination value ΔI'1JIA, and therefore the engine is Is it determined that the engine is in a slow deceleration state at any of the determined rotational speeds, and does the engine rotational speed Ne exceed the predetermined rotational speed NA? At the time (
t□) reaches the upper limit value NH of the target idle speed,
Until the time point (t□, ) when feedback control is started, the initial value (DXIII):F+Di)
Auxiliary air is continuously supplied to the engine according to the valve opening duty ratio set in PAD (this is referred to as "deceleration mode control"). The engine rotation speed Ng is the predetermined rotation speed NA
By supplying the auxiliary air amount set in the deceleration mode to the engine in advance from the time when the target idle speed reaches the upper limit value NH until the control by the feedback mode, which will be described later, starts. It is possible to smoothly shift to feedback mode control without the rotational speed crossing the target idle rotational speed and dropping significantly.

Engine speed Ne is the upper limit of target idle speed NH
From the time when the engine is drained (ti3), the engine speed changes from this upper limit value N)l to the lower limit value NL, which is smaller than this by a predetermined number of revolutions.
The valve opening duty ratio Do of the control valve 6 is adjusted according to the deviation between the target idle speed and the actual engine speed so that the target idle speed is maintained between
uT is feedback controlled.

When the engine shifts from an idle state to an acceleration state by opening the throttle valve 5 (after time tLI in Fig. 2),
The valve opening duty ratio DouT is set to an initial value of the valve opening duty ratio set immediately before the throttle valve 5 is opened, and is set to gradually decrease until this value becomes zero (t14 in FIG. 2(B)). (Hereinafter, this will be referred to as "acceleration mode control.") When the throttle valve 5 is opened, auxiliary air via the control valve 6 is not required, but by gradually reducing the amount of auxiliary air as described above, the acceleration state is achieved. The transition can be made smoothly.

When the engine speed No decelerates along the rapid deceleration line shown by the dashed line in FIG. 2(A), when the engine speed Ne crosses the first discrimination speed NIA Decrease rate Δ of engine speed at time t2 in the figure)
Ne is compared with a predetermined determination value ΔNSA in the same manner as described above, and if the deceleration amount ΔNe is larger than the predetermined determination value ΔNSA, it is determined that the engine is in a rapid deceleration state. In such a case, the sum of the discrimination rotation speed NSA, the time TSAM determined by the deceleration Na, and the time TSAE determined by the value DH corresponding to the magnitude of the load on the electrical device 16 is added to the correction value KPAD determined by the detected atmospheric pressure value PA. , and a correction value KDX*IEF determined according to changes in engine performance characteristics over time, etc.
Time corrected by TSA= (TSAM+T8AE)X
KPAD X K5 X l! , :F, the control valve 6 is set to a predetermined valve opening duty ratio DsA (100%) to supply auxiliary air to the engine (from time t2' to TSA period).

Then, when such shot air control is carried out at the discrimination rotation speed N S Az p which is lower than the discrimination rotation speed NSA □ and the discrimination rotation speed N S A3 which is lower than this, respectively (
1 in Figure 2. , 1. ), except that the engine rotational speed is different from each discrimination rotational speed N5A2. If shot air control is already being executed when the vehicle crosses the NSA, this shot air control will continue to be executed. Second
In the figure, the broken line C indicates that the deceleration rate ΔNe of the rotation speed is sufficiently small when it crosses the first discrimination rotation speed NSA (at time t4 in FIG. 2), so there is no need to execute shot air control, and thereafter For example, the engine rotation speed changes when the engine rotation speed suddenly decreases between the first discrimination rotation speed NSA and the second discrimination rotation speed NsA due to the addition of a load to the electric device 15. In this case, shot air control is executed when the engine speed drops across the second discrimination speed NSA2 (at point 7 in Figure 2) (Figure 2 (B)).
period from t'7 to TEA period). Even if the engine speed Ne falls below the upper limit value NH which is the feedback control starting speed (at time ts), if the predetermined period TSA set for the discrimination speed N5A2 has not elapsed, the predetermined amount supply of auxiliary air (DouT=DsA
) will continue to be executed with priority over feedback control.

When the predetermined period T8A has elapsed (time t'za), feedback control is started with the valve opening duty ratio (Dx plus DIE) XKPAD as an initial value. In this way, even if the engine speed Ne rapidly decreases at any point during deceleration, the shot air control executed at a plurality of determined engine speeds will smoothly bring the engine speed to the target idle speed and with no control delay. It is possible to reliably migrate without any problems.

FIG. 3 is a program flowchart showing the procedure for calculating the valve opening duty ratio Dou〒 of the control valve 6, which is executed in the CPU 9b of the ECU 9 every time the TDC signal from the Ne sensor 15 is input.

First, a value Me that represents the generation time interval between the current TDC signal and the previous TDC signal and is proportional to the reciprocal of the engine speed Ne.
It is determined whether or not is larger than a value MA corresponding to the reciprocal of a predetermined rotational speed N A (for example, 1500 rpm) (step 1). If the determination result in step 1 is negative (No) (Me≧MA does not hold), that is, when the engine speed Ne is greater than the predetermined value NA (before time t in Fig. 2), there is no need to supply auxiliary air. Valve opening duty ratio D of control valve 6
outT is set to zero (step 2, the control mode in which the valve opening duty ratio Dour is set to zero and the control valve 6 is fully opened is referred to as "rest mode").

If the determination result is positive (Yes) in step 1 (Me
≧MA holds), that is, when the engine speed Na is smaller than the predetermined value NA (after time t1 in FIG. 2), it is determined whether the throttle valve 5 is substantially fully open (step 3). If the throttle valve 5 is substantially fully open, it is determined whether a value Me proportional to the reciprocal of the engine speed Ne is larger than a value MH corresponding to the reciprocal of the upper limit value NH of the target idle speed (step 4). ). If this determination result is negative (NO), that is, when the engine speed Ne is larger than the predetermined upper limit value NH of the target idle speed (between time t□ and t□1 of the solid line a in Fig. 2, or at one point If the previous control loop is not in the feedback mode (the determination result in step 5 is negative (No)), as will be described later, , step 6
Then, the valve opening duty ratio Dour in the deceleration mode is calculated.

The calculation of the valve opening duty ratio Dour in this deceleration mode is performed based on the following equation (1).

Do u T=(Dx large tp+Dt)XKrAo H・
・(1) DX here! ! ! F is the valve opening duty ratio Dou
The average value of T up to the previous loop, Dt, is an electrical load term, KPA, which is set according to the load state of the electrical device 16.

is the atmospheric pressure correction coefficient.

The reason why the average value DX*i:F is applied is that the amount of auxiliary air required for the engine varies depending on changes in engine performance characteristics over time, variations between engine manufacturing lots, engine oil replacement, etc. . The average value DXi
F): F is set when the switch 16a of the electrical device is in the off state, and is also used when determining the initial value at the start of feedback control and the correction value KDXREF during shot air control, which will be described later. . Also, the reason for applying the electrical load term DI: is that when the engine speed Ne is higher than the predetermined rotation speed NA, the electric device 1 that affects the engine speed
The influence of load No. 5 is relatively small, but when the engine speed is
This is because when the electrical load term D! decreases below NA, the influence of the load on the engine speed becomes relatively large. : is the control time Ts during shot air control, which will be described later.
It is also used when determining H.

The atmospheric pressure correction coefficient KPAD compensates for the fact that the relationship between the opening degree of the control valve 6 that controls the auxiliary air flow rate and the inflow air flow rate differs depending on changes in atmospheric pressure, and the operation of the control valve 6 This is also applied when performing duty control and when performing shot air control, which will be described later.

The average value Dx*tp is 1, for example, calculated by the following equation (2).

DxHp=”Dr+n+’ cD, X1lf:F
・++ (2) A, A Here, A and C (1≦C<A) are constants, D p Hn
are the values of the feedback modes of this loop, and D'
X*EP is the average value of the valve opening duty ratios DouT obtained up to the previous loop. D' Xll in calculating the average value by changing the constant C! The weight of the value of F can be changed.

Further, the following equation (3) may be used instead of the previous equation (2).

Here, DPIn-j is the feedback mode type value calculated in the loop j times before the current loop, and B is a constant. In this case, the average value I)x*tp is equal to the arithmetic mean value of the feedback modes from the previous loop eight times to the current loop.

Electrical load term DI! To determine, first compare the valve opening duty stored in the storage means 9c of the ECU 9! :X-Power generation status signal value From the E table (not shown), D! is determined according to the output signal of the power generation status detector 20 in FIG. ! Read the n value.

More specifically, first, for example, the valve opening duty ratio according to the power generation state signal value E is determined from the valve opening duty ratio DI: x - power generation state signal value E table at the reference engine rotation speed (for example, 700 rpm) shown in FIG. Determine DEX.

The table in FIG. 5 shows E□ (for example, IV), E (for example, 2V) as power generation status signal values.

E, (e.g. 3V) and E, (e.g. 4.5V) (7)
Thus, the valve opening duty ratio as a reference correction value with respect to the set value is Di□ (for example, 50%) t Dtz (for example, 3
0%).

Dta (eg 10%) and DI! 4 (for example, 0%). Then, when the power generation state signal detection value E indicates a value between adjacent set values, the valve opening duty ratio DI is calculated by interpolation using the interpolation method! x is calculated.

D at the reference engine speed determined as described above
The EX value is applied to the following equation (4) to calculate the electrical load term DHn according to the engine speed.

D! ! n=2XDHx - (4) The correction coefficient KE is a value calculated based on the following equation (5) according to the deviation between the value Mec corresponding to the reciprocal of the reference engine rotation speed (700 rpm) and the value Me.

Kt=η

In this way, the electrical load term Dgn is expressed by the signal value E representing the power generation state according to the field winding current of the generator and the engine rotation speed Ne.
The load placed on the engine when the generator is operating is proportional to the amount of power generated by the generator.
This is because the amount of power generation is given as a function of the magnitude of the field current and the engine rotation speed, that is, the rotation speed of the generator rotor.

The atmospheric pressure correction coefficient KPAD is, for example, P shown in FIG.
It is determined from the detected value PA from the A-KPAD table. The PA-KPAD table sets predetermined values KPADx-s*PA1 as calibration variables for the correction value KPAD and the detected atmospheric pressure value PA, respectively, as the atmospheric pressure increases.
-6 is set, and if the actual detected atmospheric pressure value P^ is between each value PAany, the correction value is set to A.

is determined by interpolation calculation.

Returning to FIG. 3, if the engine speed decreases and the determination result in step 4 becomes affirmative (Yes) (Me≧MH holds true), that is, the engine speed Ne reaches the predetermined upper limit value NH of the target idle speed. If it becomes below (tt on the solid line a in Figure 2)
3 time points, 1. above the dashed-dotted line. t□□ at time point or on dashed line C
At step 7), it is determined whether the predetermined period TSA shown in FIG. 2 has elapsed, that is, whether the TSA value of the timer set in the shot air subroutine, which will be described later, has become zero. If the determination result is affirmative (Yes), the process proceeds to step 8, and the calculation of the valve opening duty ratio DouT is performed in the feedback mode.On the other hand, if the determination result is negative (No) (t t□.), step 6 is executed.

The calculated value of the valve opening duty ratio D o u T in the feedback mode in step 8 is composed of the following as shown in equation (6).

DouT=(DA+n+Dp)XKpao +++ (
6) That is, the DouT value is composed of the integral control term value DAIn and the proportional control term value DP, and the value DAIn of the integral control term during the current loop is the integral control term stored in the storage means 9c of the ECU 9 in FIG. A value obtained by adding a correction value ΔDI set according to the difference between the actual engine speed and the target idle speed and a correction value DIE caused by a change in the load condition of the electrical device 15 to the previous value DAmn-0 (DAl n == D.A.
In is set to 4+ΔDI+DI.

Note that when swing 8 is executed for the first time, the previous value DAIn-1 of the integral control term is the initial value and the valve opening duty ratio value CDx*tv+Di) set in step 6 above.
X KPAD is set. The proportional control term value Dp is set according to the difference between the actual engine speed and the target idle speed, is stored in the storage means 9c of the ECU 9, and is stored in the above-mentioned Dx large ip.
Used to calculate.

During idle speed control in feedback mode, the engine load is reduced due to disturbances, electrical load interruption, etc., and the engine speed Ne reaches the target idle speed upper limit No.
may exceed. Once the control in the deceleration mode is finished and the control in the feedback mode is started, the engine rotation speed N will be maintained as long as the throttle valve 5 is fully open.
Even if auxiliary air amount control is continued in feedback mode even if e exceeds the upper limit NH, there is no longer any risk of engine stall, and control in feedback mode can provide faster and more accurate rotation speed control. . Therefore, when the engine speed Ne exceeds the upper limit value NH of the target idle speed due to disturbances, electrical load interruption, etc., it is determined in step 4 that Me≧MH does not hold, and the process proceeds to step 5. It is determined whether the previous control loop was performed in feedback mode;
Since the previous loop was in feedback mode (determination result is affirmative (Yes)), the process proceeds to steps 7 and 8, and control in feedback mode is subsequently executed.

Next, when the throttle valve 5 is opened from idling operation under feedback control (at time 109 in FIG. 2), auxiliary air amount control is performed in acceleration mode. That is, if the determination result in step 3 is negative (No),
To proceed to step 9 and calculate the valve opening duty ratio in the acceleration mode, the valve opening duty ratio Do in the acceleration mode is calculated.
The uT calculation is performed in a feedback mode immediately before the opening of the throttle valve 5 without abruptly stopping the supply of auxiliary air by the control valve 6 when the throttle valve 5 is opened from idling operation and shifts to acceleration operation. The integral control term value DA1n-1 set during control is set as the initial value, and thereafter, the predetermined value Δ is increased every time a pulse of the TDC signal is generated until the initial value becomes zero.
The amount is gradually decreased by DAOc.

After calculating the valve opening duty ratio DouT in any one of steps 2, 6, 8, and 9, the process proceeds to step 10, where the shot air subroutine (FIG. 4) according to the present invention is executed.

First, in step 40 of FIG. 4, it is determined whether shot air control was executed when the TDC signal pulse was generated last time.

When the determination result in step 40 is negative (NO), in steps 41 to 46, it is determined that the engine rotational speed is the determined rotational speed NSA at the time of the previous pulse generation of the TDC signal and the current pulse generation time, N8A.

or N s A, is determined to determine whether or not it has decreased across N s A.

That is, in step 41, it is determined whether the value Men proportional to the reciprocal of the engine rotation speed at the time of the current TDC signal pulse generation is larger than the value M S A1 proportional to the reciprocal of the first discrimination rotation speed N5A1 (for example, 1100 pp m). determine whether
In step 42, a value Men-z proportional to the reciprocal of the engine rotation speed Ne at the time of the previous pulse generation of the TDC signal is smaller than the value M 8 A1 (that is, N en-, > N S
A1). If the determination result in step 41 is negative (No) (ie, Ne≧N8A1), this subprogram is ended. If the determination results in steps 41 and 42 are both affirmative (Yes), it means that the engine rotation speed has decreased across the first determination rotation speed N s A1 between the previous pulse and the current pulse of the TDC signal. However, in such a case, the process proceeds to step 47, which will be described later.

When the value Me is larger than the discrimination value M S At in both the previous pulse and the current pulse generation of the TDC signal, that is,
When the Ne value is less than or equal to the value NSA□, it is determined in steps 43 and 44 whether or not the engine rotation speed has decreased across the second determination rotation speed N5A2, similarly to steps 41 and 42. That is, the value M when the TDC signal pulse is generated this time
en is the second discrimination rotation speed N8A2 (for example, 10100
When it is larger than the value MsA2 proportional to the reciprocal of 0rp (M e n > M s A - not established in step 43), this subprogram is ended.

M e n >M S Az and Man-, (MsA,
(If the determination result in step 44 is affirmative (Yes)), the process proceeds to step 47.

Similarly, when the value Me is larger than the discrimination value MSA in both the previous pulse and the current pulse generation of the TDC signal, that is, when the Ne value is less than or equal to the value NSA, steps 45 and 46
Then, as in steps 43 and 44, it is determined whether the engine speed has decreased across the third determination speed N s A. That is, when the value Men at the time of the current TDC signal pulse generation is larger than the value M 8A1 proportional to the reciprocal of the third discrimination rotation speed N s A (for example, goOrpm) (in step 45, Men > MsA
a), this subprogram ends. Men
>MSA3 and Men-□<MsAz (Step 46
When the determination result is affirmative (Yes), the step 47
Proceed to.

In step 47, the Man value detected when the current TDC signal pulse is generated and the value Men-* (the detected value Men-, is (stored in the storage means 9c of the ECU 9), determine the deceleration amount ΔMe (=M e n -M e n-4) of the engine speed, and this value ΔMe corresponds to the reciprocal of the predetermined judgment value ΔN s A. It is determined whether or not it is larger than a predetermined determination value ΔMesA. To find the deceleration amount ΔMe, the value Men- before the 47 DC signal is used.

is used to calculate the AMe value by eliminating manufacturing errors and installation errors of the Ne sensor 14. If these errors are within the allowable range, the previous value Men-4 is used instead of the Men-4 value.
□ may also be used. The determination result in step 47 is affirmative (Y
In the case of es), that is, when the deceleration amount ΔMe of the engine rotational speed reaches a predetermined determination value and is larger than MesA, it is determined that the engine is in a rapid deceleration state. In this case, the process proceeds to step 48, where the value of the electrical load term DI: is calculated, and shot air control is performed according to the value of the electrical load term DE, that is, according to the operating state of the electrical device 15. The set time TsAE is determined from the D11 knee TSAIE table.

FIG. 7 shows a DE-TSAE table, and as is clear from this table, the TsAi: value is set to increase as D6 increases. Furthermore, step 49
8, a set time T8AM corresponding to the rotation speed determination value MSA and the ΔMe value is determined from the MSA-ΔMe map shown in FIG. The N8A-ΔMe map in FIG. 8 shows each rotation speed discrimination value M S A1. ΔMe for M s A□ and M S A3, respectively (for example, the difference ΔN in engine speed
The value corresponding to the value where e is 40 rpm/TDC) to 8Me, (for example, the difference in engine speed ΔNe
is 20Orpm/TDC)
The value of TsAi,j is set to be smaller as i increases and j decreases.

The reference setting time T'SA of the shot air timer ts4 is determined from the following equation (5) from the TSAE value and the TSA III value determined in steps 48 and 49 (step 50).

T' 5A=TsAy+TsAE++ (7) In step 51, the correction value KDX*EF is changed to D XRE shown in FIG.
It is determined from the F-K DXREF table, and corrections are made in response to changes in engine performance characteristics during shot air control. D XREF K DX+l! The EF table is the average value D X+! A predetermined width of tEF (e.g. 25%
) KD bran E corresponding to a plurality of predetermined values set for each
A predetermined value (1,0 to 5.0) of F is set,
As the average value DXREF decreases, the inflow amount of auxiliary air is reduced.

In the next step 52, the correction value KDXIIEF thus obtained and the atmospheric pressure correction value KPAD described above are calculated using the following equation (8).
is multiplied by the base LJ constant time T'SA calculated in step 50, and the result is set as the set time TsA of the shot timer tsA.

T 5A=T' SAX KPADX KDXREF
(8) Next, in step 53, the shot air timer tSA is started to operate for the set time TSA, and the process proceeds to step 54. In step 54, it is determined whether the set time TSA of the tsA timer has elapsed.

When this determination result is negative (No), the process moves to step 55, and the valve opening duty ratio DouT of the control valve 6 set in step 6 or 8 of FIG. 3 is set to a predetermined value DSA (10
0%) and exit this program. and,
In step 11 in FIG. 3, the control valve 6 is driven to open based on the valve opening duty ratio DouT set as described above, and shot air control is executed (t in FIG.
'2).

In the next loop, in step 40 of FIG.
In this case, the process immediately proceeds to step 54, where it is determined whether or not the set time has elapsed. Then, if the set time TsA has not elapsed, step 55 is repeatedly executed and the valve opening duty ratio Do
ur is set to a predetermined value DsA, and shot air control is continued.

If it is determined in step 54 that the set time TSA of the tsA timer has elapsed, step 55 is skipped and the program ends. That is, in this case,
In step 11 of FIG. 3, steps 2, 6, 8 .
and the valve opening duty ratio DOu set in either of 9.
Valve opening control of the control valve 6 is executed based on T.

Incidentally, when it is determined in step 47 of FIG. 4 that the AMe value is smaller than the determination value ΔMesA, it means that the engine is in the t1 deceleration state at the determined rotation speed NSA, and the process proceeds to step 54. In such a case, since the tsA timer in step 53 is not operating, the determination result in step 54 is '$8 fixed (Yes), and step 5
You will end this program by skipping step 5.
The valve opening duty ratio Dour is never rewritten to the predetermined value DsA.

(Effects of the Invention) As described above in detail, according to the idle speed feedback control method for an internal combustion engine of the present invention, a predetermined determination speed higher than the starting speed of feedback control is set, and the engine speed is detected. and determining whether or not the engine rotational speed has decreased across the predetermined determination rotational speed during deceleration toward the feedback control start rotational speed of the engine, and when the engine rotational speed has decreased across the predetermined determination rotational speed. The deceleration amount of the engine rotation speed is detected, and when the deceleration amount thus detected is larger than a predetermined value, the valve opening time of the control valve is determined according to the control setting used for the feedback control, and the valve opening time determined in this way is determined. Since the control valve is opened over a period of time, when the engine suddenly decelerates to the idle speed feedback control area, regardless of changes in the performance characteristics of the engine over time, etc., the control valve is opened over time. Idle rotation speed feedback control is achieved that allows the engine to smoothly transition and obtain a stable idle rotation speed at an early stage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of an internal combustion engine idle speed control device to which the method of the present invention is applied;
The figure is a timing chart showing temporal changes in the engine speed Ne and the valve opening duty ratio DouT of the auxiliary air amount control valve to explain the idle speed control method of the present invention. FIG. 4 is a program flowchart of the shot air subroutine according to the present invention; FIG. 5 is a graph showing a table of the relationship between power generation status signal value E and valve opening duty ratio Dx; FIG. 6 is a graph showing atmospheric pressure detection Graph showing a table of the relationship between value PA and atmospheric pressure correction coefficient KPAD, seventh
The figure shows the electric load term DE and shot air timer setting time T.
A graph showing a table of SAE relationships, Fig. 8 is a map diagram for setting the shot timer setting time TSAM, and Fig. 9 shows average value DXREF and correction value KDXIIIEF.
It is a graph showing a table of relationships. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 5... Throttle valve (throttle valve) 6... Control valve, 9... Electronic control unit (ECU), 9b... CPU, 10... Fuel injection valve, 14...Engine speed (Ne) sensor, 15.
...Atmospheric pressure (PA) sensor, 16...Electrical device.

Claims (1)

[Claims] 1. A control valve that is disposed in an auxiliary air passage that bypasses a throttle valve in the intake system of an internal combustion engine and that adjusts the amount of auxiliary air supplied to the engine via the auxiliary air passage is set to a target idle. In an idle rotation speed feedback control method that performs feedback control according to the deviation between the rotation speed and the actual engine rotation speed, a predetermined discrimination rotation speed higher than the starting rotation speed of the feedback control is set, and the engine rotation speed is detected;
It is determined whether or not the engine rotation speed has decreased across the predetermined determination rotation speed during deceleration toward the feedback control start rotation speed of the engine, and when the engine rotation speed has decreased across the predetermined determination rotation speed, the engine rotation speed is determined. When the detected deceleration ratio is larger than a predetermined value, the valve opening time of the control valve is determined according to the control amount used for the feedback control, and the valve opening time is adjusted to the determined valve opening time. A method for feedback controlling an idle rotation speed of an internal combustion engine, characterized in that the control valve is opened over the period of time. 2. The opening time of the control valve is determined based on the average value of the control amount of feedback control after the engine finishes warming up.
The idle speed feedback control method for an internal combustion engine as described in .