JPS6181547A - Feedback control method for number of idle revolutions of internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve filling efficiency and to prevent worsening of emission due to failure in ignition, by a method wherein the initial value of an operation amount during the starting of feedback control is set at a specified time, and an auxiliary air amount responding to the initial value is fed to an engine. CONSTITUTION:When the number Ne of revolutions of an engine is below the given number NA of revolutions, progress is made to a step 6. In the step 6, when the number Ne of revolutions becomes below an upper limit valve NH of the number of idle revolutions, an engine is shifted to a feedback mode during idle running. Based on a valve opening time DXREP, set in a step 8, serving as an initial value, feedback control is started. During a time lapsing till feedback control is started, an auxiliary air amount responding to the initial value is fed to an engine. This, even during a low temperature time in that the temperature of cooling water for the engine is low, enables improvement of filling efficiency of the engine during release of fuel cut, and improvement of emission.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for controlling an idle rotation speed feed pack of an internal combustion engine, and in particular, a method for preventing an engine stall by distinguishing between an engine deceleration operating state and an idle rotation speed feedback control operating state. The present invention relates to an idle rotation speed feedback control method that achieves this.

(Prior art and its problems) In an internal combustion engine, when idling is performed when the engine cooling water temperature is low, or when an electrical load such as a headlight or an air conditioner is applied to the engine during idling, the load on the engine increases. increases, the idle speed decreases, and engine stall is likely to occur.For this reason, conventionally, a target idle speed is set according to the engine load condition, and the difference between this target idle speed and the actual engine speed is determined. There is no known idle speed feedback control method that detects the difference and controls the engine speed to maintain the target idle speed by supplying auxiliary air to the engine in response to the magnitude of the difference so that the difference becomes zero. ing.

On the other hand, if the auxiliary air amount control is started using the feedback control described above only when the engine speed falls below the target idle speed when transitioning from the throttle valve fully open deceleration state to the idling state, the engine speed will be In order to solve the inconvenience that the engine speed drops below the target idle speed due to control delay, and if this drop is large, engine stall occurs, the amount of auxiliary air necessary to maintain the engine speed at the target idle speed is determined. A method has been proposed (this is called a "control method using deceleration mode") in which the engine speed is supplied to the engine in advance from when the engine speed drops below a predetermined speed before starting feedback control (for example, when the Kaisho 5
No. 8-124052).

Furthermore, in an internal combustion engine equipped with an electronic fuel control device, when the engine is decelerating and the throttle valve is close to fully open, the supply of fuel to the engine is cut off (
When the engine speed drops to a predetermined speed set near the idle speed, that is, the fuel cut release speed, normal fuel supply control is resumed to improve fuel efficiency. That's what I do.

In this case, the start point of supply of auxiliary air to increase the amount of air-fuel mixture by the aforementioned deceleration mode control may be made to coincide with the time when the fuel cut is released, but generally speaking, when decelerating with the throttle valve fully open, the filling efficiency of the engine is low. Therefore, it is necessary to increase the filling efficiency of the auxiliary air before the fuel cut release rotation is reached.

In particular, when the engine suddenly decelerates with the flottle valve fully open, the charging efficiency is significantly reduced. In such a situation, if the fuel cut-off (hereinafter referred to as fuel cut) is canceled and the normal fuel control is resumed, the air-fuel mixture required to obtain the required engine output cannot be secured, resulting in an engine stall. . Therefore, it is required to prevent the engine from stalling after the fuel cut is canceled by increasing the filling efficiency of intake air when the fuel cut is canceled. Additionally, a control method is known in which the engine is operated smoothly when the fuel cut is canceled by changing the fuel cut release rotation speed according to the engine coolant temperature, and the fuel cut is canceled depending on the engine water temperature. When the rotational speed is changed, the time point at which the intake air filling efficiency is increased needs to be changed accordingly.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and is concerned with the filling efficiency of the auxiliary air when the fuel cut is canceled, especially when the fuel cut is canceled by sudden deceleration with the throttle valve fully closed. In order to achieve the above object, the present invention improves the filling efficiency in advance and improves the emissions caused by misfire when the fuel cut is canceled. During idling, the throttle valve of the intake system of the engine is controlled in accordance with the deviation between the target idle rotation speed and the actual rotation speed by controlling the actuation amount of a control valve provided in the bypass bypass passage to control the amount of auxiliary air, thereby reducing the deviation. In the idle speed feedbank control method, when the internal combustion engine is in a predetermined operating state during deceleration, fuel supply to the engine is cut off, and when the engine speed is higher than the target idle speed, the engine The initial value of the operation amount at the time of starting the feedback control is set to a value higher than a predetermined fuel cut release rotation speed that changes according to the cooling water temperature, and when the rotation speed becomes lower than the predetermined rotation speed that changes according to the cooling water temperature. setting, supplying the auxiliary air amount corresponding to the initial value to the engine until the feedback control is started, and canceling the fuel cut after increasing the charging efficiency, thereby preventing a misfire after the fuel cut is canceled. The present invention provides an idle rotation speed feedback control method for an internal combustion engine that prevents deterioration of emissions due to engine speed.

(Example of the invention) The method of the present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram schematically showing the entire idle speed feedback control device for an internal combustion engine to which the method of the present invention is applied. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and the engine 1 includes: An intake pipe 3 having an air cleaner 2 attached to its open end is connected to an exhaust pipe 4. intake pipe 3
A throttle valve 5 is disposed in the middle of the throttle valve 5, and an air passage 8 that opens into the intake pipe 3 downstream of the throttle valve 5 and communicates with the atmosphere is disposed. 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 solenoid valve,
When the solenoid 6a and the solenoid 6a are energized, the air passage 8
The solenoid 6a is electrically connected to an electronic control unit (hereinafter referred to as rECUJ) 9.

A fuel injection valve 10 is provided between the engine 1 of the intake pipe 3 and the opening 88 of the air passage 8.
o is connected to a fuel pump (not shown) and EC
Electrically connected to U9.

A throttle valve opening sensor 17 is connected to the throttle valve 5, and a pipe 11 is installed downstream of the opening 8a of the air passage 8 of the intake pipe 3.
An intake pipe absolute pressure sensor 12 communicating with the intake pipe 3 via
However, an engine cooling water temperature sensor 13 and a rotation speed sensor 14 are respectively attached to the engine 1 body, and each sensor is
It is electrically connected to CU9. Reference numeral 15 indicates an electrical device such as a headlight or a near conditioner.

This electric device 15 is electrically connected to the ECU 9 via a switch 16.

ECU9 shapes input signal waveforms from various sensors,
An input circuit 9a having functions such as correcting the voltage level to a predetermined level and converting analog signal values into digital signal values.
, central processing circuit (hereinafter referred to as r (, PUJ) 9b
, a storage means 9c for storing various calculation programs executed by the CPU 9b, calculation results, etc., and the fuel injection valve 1.
0 and an output circuit 9d that supplies a drive signal to the control valve 6.

Next, the operation of the idle rotation speed feedback control device configured as described above will be explained.

Engine operating state parameter signals from the throttle valve opening sensor 17, absolute pressure sensor 12, water temperature sensor 13, and engine speed sensor 14 are input to the input circuit 9 of the ECU 9.
a to the CPU 9 b, and the CPU 9 b inputs the values of these engine operating state parameter signals and the electric device 1
The engine operating state and engine load state are determined based on electrical load state B (No. 8) from No. 5, and the amount of fuel supplied to the engine 1, that is, the opening time of the fuel injection valve 10 is uT and the auxiliary air amount, that is, the valve opening time duty ratio DouT of the control valve 6, are calculated, and the fuel injection valve 10 and the control valve 6 are adjusted according to each calculated value.
A control signal for operating the circuits is supplied to each of them via an output circuit 9d.

The solenoid 6a of the control valve 6 is energized for a valve opening time corresponding to the calculated value, and opens the valve 6b to open the air passage 8, and a predetermined amount of air according to the valve opening time is supplied to the air passage 8 and the intake air. It is supplied to the engine 1 via a pipe 3.

The fuel injection valve 1o injects fuel into the intake pipe 3 by opening the valve for a valve opening time according to the above-mentioned calculated value, and the injected fuel is mixed with the intake air to always maintain the required air-fuel ratio (for example, stoichiometric air-fuel ratio). The air-fuel mixture is supplied to the engine 1.

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 in this manner, the engine speed during idling can be controlled.

Next, details of the idle speed control action of the above-mentioned idle speed feedback control device will be explained with reference to FIG. 1 and FIGS. 2 to 4 described above.

First, FIG. 2 shows the rotational speed control method of the present invention. During deceleration, the throttle valve 5 shown in FIG.
Or, when the rotation speed becomes lower than the second predetermined rotation speed NAL (<NAH) (Fig. 2 (a)), the control valve 6 opens and auxiliary air is supplied through the air passage 8, which will be described later. Air deceleration mode control is started. When the engine speed further decreases to below a predetermined idle speed upper limit value NH, the auxiliary air amount is controlled by the feedback motor to maintain the engine speed Ne between the upper limit value NH and the lower limit value N. The upper limit value NH and lower limit value N of these predetermined idle speeds are set to optimal values for the engine each time according to changes in the engine cooling water temperature, the electrical load state of the electric device 15, etc.

Fuel cut release rotation speed N in deceleration operation mode
pc changes according to the engine coolant temperature Tw, and pc changes depending on the engine coolant temperature Tw.
0° C.) or less, the first predetermined rotation speed NpcH (for example, 17000 pm) is set, and when the temperature is below, the second predetermined rotation speed NpcL (for example, 900 rpm) is set. Further, the first and second predetermined rotational speeds NA H and NAL are set to slightly higher rotational speeds than the first and second fuel cut release rotational speeds N p H and N FL, respectively, and the engine cooling It is set to change according to the water temperature Tw, and as shown by the solid line in FIG. 3, when the predetermined temperature Tw is lower than the first value N.
AH (for example, 2000 rpm) or above, the second value NAL (for example, 1200 rpm) is obtained. That is, each of the first and second predetermined values NA)1. NAL is the above-mentioned 1. Second fuel cut release rotation speed NPQH,N
pa, - changes according to the engine cooling water temperature Tw, and each of these fuel cut release rotation speeds NP
H, NFL always has a predetermined rotation ΔNe (=30Orp
m) is set to a higher rotation speed.

In the deceleration mode, the supply amount of auxiliary air is
), when the engine speed Ne becomes below the first or second predetermined rotation speed NAH or NAL, the control valve 6 opens for a predetermined valve opening time and duty ratio DXREP to provide a predetermined amount of assistance. Air is supplied. This predetermined time DXR
As described later, EP is the average value of the control amount of the control valve 6 during idle rotation speed feedback control. When the engine speed Ne decreases and reaches the predetermined idle speed upper limit value NH, feedback control of the control valve 6 is started using the value DXREP as the initial value of the operating amount.

When the engine speed Ne falls below the predetermined engine speed NAH or N set according to the engine cooling water temperature during deceleration with the throttle valve fully closed, DXI!
By increasing the auxiliary air by the amount of EP, the filling efficiency of the auxiliary air can be increased when the fuel cut is released, and even if the clutch is disengaged during deceleration, the engine speed will drop suddenly and the engine speed will be reduced. It is possible to avoid a situation where the auxiliary air control using the feedback mode during idle, which starts at a few NH or less, cannot follow suit, resulting in deterioration of emissions due to misfire.

The idle speed control in the feedback mode detects the difference between the idle target speed set by the ECU 9 according to the engine load state and the actual speed Ne from the engine speed sensor 14, and controls the idle speed so that this difference becomes zero. This consists of controlling the opening time of the control valve to increase or decrease depending on the magnitude of the difference.

During feedback control of auxiliary air during idling, the engine load may be reduced due to disturbance or electrical load interruption, and the engine speed Ne may exceed the idle speed upper limit NH (Sn in FIG. 2(a)).

In this case, the ECU 9 determines whether or not the previous loop is in the feedback mode, and in the example of FIG.
Since n-1 is in the feedback mode, control is continued in the feedback mode. Furthermore, in the example of Fig. 2, if the engine speed Ne of the next time (Sn, etc.) exceeds the upper limit NH, the current speed (S
It is determined that the controller n) is controlled in the feedback mode, and will be controlled in the feedback mode next time as well.

That is, once the control in the deceleration mode is finished and the control in the feedback mode is started, as long as the throttle valve 5 is fully open, the engine rotational speed Ne will change due to disturbances etc.
Even if NH exceeds the upper limit value NH, control in the feedback mode continues to be performed, thereby achieving quick and accurate idle rotation speed control.

In the deceleration mode region, as long as the engine speed Ne takes a value larger than the upper limit NH (Sk in Fig. 2 (a)),
The ECU 9 determines whether the previous loop (S k-, ) is in the deceleration mode or not, and control in the deceleration mode is executed. As a result, for example, if the rotation speed is still high in deceleration mode and the feedback control is performed due to a misdiagnosis that the rotation speed is still high, the opening time of the control valve 6 becomes an extremely small value, and the clutch is disengaged in this state. It is possible to avoid a situation where the engine stalls when the engine stalls.

FIG. 4 is a flowchart of a program showing control procedures for deceleration control and idle rotation speed control using the above-mentioned auxiliary air control. This engine control program is EC
In the UQ, it is called when the throttle valve 5 is fully open (step 1), and first, a value proportional to the reciprocal of the first predetermined value NAH or the second predetermined value Nr is determined according to the engine coolant temperature Tw. MAH (CI: 1 / NAH
) or MAL (QCl /NAL) is selected (step 2).

For convenience of explanation, each of the first and second predetermined values NAH1N
AL is typically represented by the value NA, and accordingly the value MAH.
and MAL are also typically represented by the value MA, and will be described below. Note that the value MA is used for convenience of calculation processing within the ECUQ, and is the time interval between pulse signals generated corresponding to the engine speed from the engine speed sensor 14, and the higher the engine speed Na is, the more The two-hour interval Me is shortened.6 A value Me proportional to the reciprocal of the engine rotational speed Ne is compared with a value MA corresponding to the reciprocal of the predetermined rotational speed NA (
Step 3), when Me≧MA does not hold, that is, when the rotation speed Ne is larger than NA, the supply of auxiliary air is unnecessary, so the valve opening time duty ratio DouT of the control valve 6 is
is calculated as zero (step 4), and the execution of the program is ended (step 5).

When Me≧MA holds true in step 3, that is, when the engine speed Ne becomes smaller than the predetermined engine speed NA, the process proceeds to the next step 6, where the value Me, which is inversely proportional to the engine speed Ne, becomes the predetermined idle speed upper limit. It is compared with a value MH which is inversely proportional to NH. If Me≧MH does not hold,
That is, when the engine speed Ne is larger than the upper limit NH,
It is determined whether the control in the previous loop was in the feedback mode (step 7), and if NO, it is determined that the mode is the deceleration mode, and the valve opening time duty ratio DOut in the deceleration mode is set to DXREP (step 8
).

If Me≧MH holds true in the step 6, that is, if the engine speed Ne becomes smaller than the idle speed upper limit NH, the mode shifts to the idle feedback mode, and the valve opening time Dx*ip set in the step 8 is set to the initial value. Feedback control is started as follows, and the average value DxHp of the valve opening time duty ratio Dou T in the foot bank mode is newly calculated (step 9).

If the answer in step 7 is affirmative (Yes), that is, if the previous loop was controlled in the feedback mode, the process also proceeds to step 9 and continues to be controlled in the feedback mode.

This average value DXREP is calculated by the following formula.

Here, A and C (1≦C<A) are constants, D A I
N is the value of the feedback mode of this loop, and D
'x□2 is the average value of the valve opening duty ratios Dour obtained up to the previous loop. By changing the constant C, it is possible to change the weight of the value of D'XREP in calculating the average value.

Furthermore, the following equation may be used instead of the previous equation.

Here, DAIN-j is the value of the feedback mode type calculated in the loop j times before the current loop, and B is a constant. In this case, the average value DXREF' is equal to the arithmetic average value of the feedback modes from the previous loop B times to the current loop.

in this way. In the deceleration driving state, the engine speed N
When e falls below the predetermined value MA, the control valve 6 is opened by the operating amount of the control valve 6 during feedback of the idle rotation speed up to the previous time, that is, the average value DXREP of the valve opening time duty ratio Dour, and the target idle rotation is After increasing the filling efficiency by supplying the same amount of auxiliary air as during the feedback control,
The engine output is improved by canceling the fuel cut and securing the required amount of air-fuel mixture at the time of canceling the fuel cut, and then performing idle rotation speed feedback control after the fuel cut is canceled using the average value Dx as an initial value. to move to. Furthermore, since the predetermined value NA is always set to a value higher than the fuel cut release rotation speed Npc, deterioration of emissions due to misfire at low temperatures is prevented. (Effects of the Invention) As explained above, the present invention provides a bypass passage that bypasses the throttle valve of the intake system of the engine according to the deviation between the target idle rotation speed and the actual rotation speed when the internal combustion engine is idling. In the idle rotation speed feedback control method in which the amount of auxiliary air is controlled by controlling the actuation amount of a control valve, and the plan deviation is eliminated, when the internal combustion engine is in a predetermined operating state during deceleration, The fuel supply is cut off, and the rotational speed of the engine is set to a value higher than the predetermined fuel cut release rotational speed, which is higher than the target idle rotational speed and changes depending on the engine coolant temperature, and the predetermined speed changes depending on the coolant temperature. An initial value of the actuation amount at the time of starting the feedback control is set when the rotation speed becomes lower than the rotation speed, and an auxiliary air amount corresponding to the initial value is supplied to the engine 1 until the feedback control is started. Therefore, even when the engine cooling water temperature is low, it is possible to increase the filling efficiency of the engine when the fuel cut is released, and it is possible to prevent deterioration of emissions due to misfire.

4.Drawing ffff Description of the vehicle Fig. 1 is an overall configuration diagram of an internal combustion engine control device to which the idle speed feedback control method of the present invention is applied, and Fig. 2 is a diagram illustrating the idle speed feedback control method of the present invention. The same figure (,ll) is a diagram showing the range of engine speeds controlled in deceleration mode and feedback mode, and the same figure (b) shows the opening of the air amount control valve as the engine speed decreases. A diagram explaining how to increase the time D o u T, Figure 3 is a graph showing the relationship between engine cooling water temperature, fuel cut release rotation speed, and rotation speed for deceleration mode discrimination, and Figure 4 is a graph showing the relationship between engine cooling water temperature and rotation speed for determining deceleration mode. 5 is a flowchart showing feedback control means.

1... Internal combustion engine, 3... Intake passage (intake pipe).

Claims (1)

[Claims] 1. Controlling the operating amount of a control valve provided in a bypass passage that bypasses a throttle valve in the intake system of the engine according to the deviation between the target idle rotation speed and the actual rotation speed when the internal combustion engine is idling. In the idle rotation speed feedback control method in which the amount of auxiliary air is controlled by controlling the amount of auxiliary air to eliminate the deviation, when the internal combustion engine is in a predetermined operating state during deceleration, fuel supply to the engine is cut off; When the rotation speed is set to a value higher than the target idle rotation speed and higher than a predetermined fuel cut release rotation speed that changes depending on the engine coolant temperature, and becomes below the predetermined rotation speed that changes depending on the coolant temperature, the feedback is performed. An internal combustion engine characterized in that an initial value of the operating amount at the time of starting control is set, and an auxiliary air amount corresponding to the initial value is supplied to the engine until the feedback control is started. Idle speed feedback control method. 2. The idle rotation speed of the internal combustion engine according to claim 1, wherein the difference between the fuel cut release rotation speed and the predetermined rotation speed is constant regardless of changes in the engine cooling water temperature. Feedback control method. 3. Claim 1, wherein the target idle rotation speed changes according to the engine coolant temperature.
The idle speed feedback control method for an internal combustion engine as described in . 4. The idle speed feedback control method for an internal combustion engine according to claim 1, wherein the initial value is an average value of the operating amount during the feedback control.