JPH0615831B2 - Combustion control device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for an internal combustion engine that prevents torque fluctuation during deceleration.

(Prior Art) Generally, the main purpose of fuel cut is to improve fuel efficiency and reduce unnecessary exhaust gas, and it is necessary to consider engine drivability while achieving these efficiently.

In a conventional combustion control apparatus for an internal combustion engine having such a fuel cut function, a deceleration state is detected from an engine speed and an idle switch, and a fuel cut is performed when a predetermined deceleration state is reached. Such a mode is not limited to the above-mentioned device, but is often used for those which supply fuel by electronic control.

Further, generally, in idle control of the engine, a solenoid valve (so-called AAC valve) is provided in the auxiliary intake passage that bypasses the throttle valve.
Is provided, the air flow rate in the auxiliary air intake passage (hereinafter referred to as "auxiliary air flow rate") is finely controlled while electronically controlling the opening time ratio of the AAC valve.

The opening time ratio of the AAC valve is given by, for example, the following equation.

ISC _ON = (various correction values) + α ... where α is a feedback correction value, and this α is
When the throttle valve is fully closed and the vehicle speed is extremely low, the value depends on the deviation between the engine speed and the target idle speed. In other cases, for example, when performing deceleration fuel cut control Is fixed at zero.

For this reason, the auxiliary air flow rate during deceleration fuel cut control is maintained at an amount equivalent to that during idle control by ISC _ON (where α = 0).

By the way, in order to prevent deterioration of drivability due to fuel cut, there are restrictions such as avoiding fuel cut at low speed, and avoiding fuel cut at high speed to prevent catalyst deterioration due to a large flow rate of O _2. It is being appreciated. Further, recently, from the viewpoint of further improving drivability, it is considered to delay the fuel cut for a predetermined time.

(Problems to be Solved by the Invention) However, in such a conventional combustion control device for an internal combustion engine, during deceleration fuel cut control, the fuel is shut off at the same time as the throttle valve is fully closed, but immediately before the fuel cut. The torque is sufficiently large according to the running resistance, so there is a feeling of stepped torque before and after fuel cut (fuel cut shock).
There is a problem that cannot be denied.

At the time of recovery from fuel cut (during recovery), torque of a magnitude corresponding to the auxiliary air flow rate equivalent to idle control is generated at the same time as fuel resupply, but the torque immediately before recovery is almost zero. Therefore, similarly, there is a problem that the stepped feeling of torque (recovery shock) before and after the return cannot be denied.

Therefore, an object of the present invention is to reduce the fuel cut shock and the recovery shock by optimizing the auxiliary air flow rate at the time of returning at the start of deceleration fuel cut.

(Means for Solving Problems) In order to achieve the above object, the present invention provides a basic concept diagram
As shown in the figure, an opening degree detection means a for detecting the opening degree of a throttle valve interposed in the intake passage of the engine, an operation state detection means b for detecting the operation state of the engine, and an operation state detection means based on the operation state of the engine. Supply means c for supplying fuel to the engine
Determining means d for determining the shift to the deceleration fuel cut state when the throttle valve is in the fully closed state; To output a control signal for increasing the intake air amount to the engine to an idle-time equivalent when returning from the deceleration fuel cut state, and an auxiliary passage communicating the upper and lower flow paths of the throttle valve. Intake operation means f, which is interposed and increases / decreases the intake air amount to the engine based on the control signal output from the intake control means e, and the intake air amount when shifting to the deceleration fuel cut state. The signal value is compared with a predetermined reference value corresponding to the intake air amount that does not cause torque shock, and when the signal value falls below the reference value, the fuel supply means c is burned. And a command means g for outputting a command signal for instructing the fuel supply means c to resume fuel supply when the signal value exceeds a reference value. Characterize.

(Operation) At the time of shifting to the deceleration fuel cut state, first, the absorbed air amount is operated to a lower side than at the time of idling, and the fuel is cut off when the intake air amount decreases to the extent that torque shock is not generated. Therefore, the amount of decrease in the generated torque at that time is sufficiently small, and the step feeling (fuel cut shock) before and after the fuel cut is reduced.

Further, at the time of returning from the deceleration fuel cut state, the fuel supply is restarted when the intake air amount increases to such an extent that torque shock is not generated. Therefore, the amount of increase in the generated torque at that time is sufficiently small, and the step feeling (recovery shock) before and after the return of the fuel cut is reduced.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 10 are views showing an embodiment of the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an engine, intake air is supplied to each cylinder from an air cleaner 2 through an intake pipe 3, and fuel is injected by an injector 4 based on an injection signal (supply signal) Si. The air-fuel mixture in the cylinder is ignited and exploded at a predetermined ignition timing, becomes exhaust gas, and is discharged through the exhaust pipe 5.

The flow rate Qa of the intake air is detected by the air flow meter 6 and controlled by the throttle valve 7 in the intake pipe 3. The opening Cv of the throttle valve 7 is detected by a throttle valve opening sensor (opening detecting means) 8. The throttle valve 7 is in a fully closed state during idling and during deceleration fuel cut, and the air flow during idling and deceleration fuel cut passes through the auxiliary passage 9 and the flow control valve (AAC valve) 1 mounted there.
Adjusted by 0. The flow rate control valve 10 duty-controls the flow passage area of the sub-passage 9 based on the control signal Sv having the duty control value MAD to control the state of transition from the deceleration fuel cut state to the return and the air flow rate during idling. To do. The throttle valve 7, the flow control valve 10, the main passage 11
The sub passage 9 constitutes the intake operation means 12 as a whole.

Further, the operating state of the engine 1 is detected by the sensor group 13, and the sensor group 13 uses the engine speed N, the vehicle speed Ss, the oxygen concentration Vs, as parameters indicating the operating state of the engine 1.
Cooling water temperature Tw, battery voltage V _B , air conditioner operation Ac
c, the depression of the clutch or the neutral position NT of the gear is detected, and signals corresponding to these are output. Air flow meter 6, throttle valve opening sensor 8 and sensor group 13
Constitutes an operating state detecting means 14, and a signal from the operating state detecting means 14 is inputted to the control unit 20.

The control unit 20 independently has a function as a determination unit, a command unit, and an intake control unit, and also has a function as a fuel supply unit together with the injector 4.
It is composed of U21, ROM22, RAM23, A / D converter 24, input port 25 and output port 26. The MPU 21 takes in the required external data from the input port 25 and the A / D converter 24 according to the program written in the ROM 22, and transfers the data to and from the RAM 23 to perform the processing required for deceleration control. The value is arithmetically processed, and the processed data is output to the output port 26 as necessary. The above-mentioned injection signal Si and control signal Sv are output from the output port 26, and the ignition signal Sp is output to the ignition means 27 for igniting the air-fuel mixture. Further, the signal from the operating state detecting means 14 is input to the input port 25 and the A / D converter 24, and the A / D converter 24 converts the input signal to the A / D converter.
D-convert. The ROM 22 stores a calculation program in the MPU 21, and the RAM 23 stores data used for calculation in the form of a map or the like.

Next, the operation will be described.

FIGS. 3, 4, 7, and 8 are flowcharts showing a program for fuel cut control written in the ROM 22, and P _{1 to} P _{58 in the} drawings show respective steps of the flow.

FIG. 3 is a flow chart showing a basic injection amount calculation routine, and this routine is executed once every 1/2 revolution of the engine.

First, at P ₁ , the output signal of the air flow meter 6 is smoothed to suppress the fluctuation of the pulsating component, and then A / D converted to obtain the intake air amount Qa, and at P ₂ , the basic injection amount Tp is calculated according to the following equation.

Tp = K × Qa / N, where K: constant The processing up to this point is the same as the conventional so-called L-Jetro fuel injection control, but in this embodiment, the following steps P _{3 and} below are performed. different.

That is, the smoothed value LTp of the basic injection amount Tp is calculated in P ₃ according to the following equation.

However, LTp ': the previous smoothed value n: an integer, for example, a value of several hundreds to several thousands. Therefore, the smoothed value LTp is n with respect to the basic injection amount Tp.
It is a value that follows with a time constant determined by. Then, at P ₄ , the difference value DTp is calculated according to the following equation.

DTp = LTp-Tp ... Such LTp and DTp are used when calculating the duty value MAD of the control signal Sv in a routine described later, and serve as data for proper combustion during deceleration or the like.

FIG. 4 is a flowchart showing an air flow rate control routine, and this routine is executed once every predetermined time.

First, at P ₁₁ , it is determined whether or not the throttle valve 7 is fully closed. If not fully closed, the learning result GMAD of the duty value MAD of the control signal Sv during the idle control stored for the cooling water temperature Tw representing the warm-up of the engine 1 at P ₁₂ is set to R.
The data is read from a predetermined address of AM23 and is corrected according to the electric load such as an air conditioner. Next, at P ₁₃ , the correction value of GMAD, which is the calculation result of P ₁₂ , is set as the current duty value MAD, the control signal S _V corresponding to this is output, and the current routine is ended. As a result, the throttle valve 7
Even when is open, the flow passage area of the sub-passage 9 is maintained at an appropriate opening, for example, to prepare for the next fuel cut start. This is also the reason why the cooling water temperature Tw and the electric load such as the air conditioner are taken into consideration, and it is intended to further improve the drivability.

On the other hand, when the throttle valve 7 is fully closed at P ₁₁ , it is determined that the vehicle is decelerating or idling. In this case, to look up from the table map to first parameter the rotational speed N and the coolant temperature Tw as shown in Figure 5 a basic duty value NMA control signal S _V at P _14, such as an air conditioner this with P ₁₅ Correct according to the electric load. Next, at P ₁₆ , the deceleration air increase coefficient KFD is looked up from a table map having N and Tw as parameters, as shown in FIG. Here, KFD is a coefficient that determines the value of the air flow rate increase in the section immediately after deceleration.

At P ₁₇ , the multiplication value DK of this KFD and the difference value DTp calculated in the routine shown in FIG. 3 (DK = DTp × KFD)
As the value that determines the air flow rate immediately after deceleration,
At P ₁₈ , this is compared with the constant LLG which is the linear attenuation determination level. When DK ≧ LLG, the duty value is M at P _19.
The above multiplication value DK is adopted as AD, and when DK <LLG, the duty value MAD is calculated according to the following equation at P ₂₀ .

MAD ← MAD-IFD ... However, IFD: a constant indicating the linear damping speed. In the formula, MAD = 0 is the lower limit.

Then, the duty value MAD compared to the base duty value NMA at P _21, when the MAD ≧ NMA and ends the current routine, when the MAD <NMA proceeds to step subsequent P _22. Therefore, MAD is D when the difference value DTp immediately after deceleration is large under the condition of MAD ≧ NMA.
Given by Tp × KFD, DTp × KFD is a predetermined value LL
If it becomes less than G, it will decrease by the value of IFD each time this routine is executed, and will linearly approach zero.

Comparing the NMA in P ₂₂ to a predetermined value LID of idle determination, when the NMA <LID ends the routine is limited to NMA the minimum value of MAD at the MAD = NMA at P _23. On the other hand, when NMA ≧ LID, it is determined at P ₂₄ whether or not the drive system is connected (whether the engine and wheels are connected), and when connected, it is determined that the vehicle is running. to end the routine through the P ₂₃ Te. When not connected, it is determined that the engine is idling, and idle control is performed in steps after P ₂₅ .

First, it is determined whether or not idle transition at P ₂₅ is a first time, proceeds to P ₂₇ is set to 3 seconds delay feedback timer DFT at P ₂₆ is the first time, as it is P ₂₇ when not the first time move on. The DFT is a timer that counts the delay time when starting the feedback control of the idle speed. The count value of the DFT in P ₂₇ it is determined whether or not the elapsed 3 seconds, 3 seconds to jump elapsed have unless the P ₁₂ terminates the routine after a P _12, P _13. On the other hand, when 3 seconds have passed, the process proceeds to P ₂₈ because the feedback control of the idle speed is performed. At P ₂₈ , the target value Ni of the idle speed is set to the cooling water temperature T
Calculated based on w, air conditioner, electric load, etc.

Next, at P ₂₉ , the current rotational speed N is compared with the target value Ni, and N>
When it is Ni, the change amount I of the idle correction coefficient HID is set at P _30.
Correct the weight loss by N. When N ≦ Ni, the coefficient HID is increased and corrected by IN at P ₃₁ . Then, at P ₃₂ , the duty value MAD at idle is calculated according to the following equation.

MAD = NMA + HID ...... Then, it is determined whether a learning condition is satisfied at P _33. Here, the learning conditions are all stable conditions such as air conditioner OFF, electric load is small, 10 seconds or more have passed from the start of idle control, and | N-Ni | ≦ 20r.pm. Is satisfied. When the learning conditions are established learns the duty during the MAD at the time of the idle at P _34. As the learning value, the average value of MAD is calculated, and R is assigned to this value according to the cooling water temperature Tw.
Store at a predetermined address of AM23.

In this way, the duty value MAD of the control signal Sv is appropriately corrected according to the electric load at that time before the idle shift, and after the idle shift, the feedback control of the rotation speed N is executed and learned as necessary. Will be corrected.

FIG. 7 is a flow chart showing the final injection amount calculation routine, and this routine is also executed once every 1/2 rotation.

First, various correction coefficients C for correcting the basic injection amount Tp at P ₄₁
Calculate OEF. COEF is a coefficient for performing correction based on the cooling water temperature Tw, full open correction, start correction, and the like. Next, at P ₄₂ , the air-fuel ratio feedback correction coefficient α is calculated for feedback control of the air-fuel ratio to the target value based on the oxygen sensor output. Incidentally, since the calculation of COEF and α is well known in the art, the details are omitted.

Next, at P ₄₃ , the duty value MAD of the control signal Sv is compared with the fuel cut determination level LFC, and MAD ≧ LF
When the C ends the routine after calculating the final injection amount Ti in accordance with the following equation by P _44.

Ti = Tp + COEF × α + Ts ...... However, one TS ...... voltage correction amount, MAD <placed at P ₄₅ it is determined that the fuel cut condition when the LFC and Ti = Ts, the zero injection quantity of substantially ( That is, the fuel cut is performed) and the routine ends.

Here, the fuel cut determination level LFC is a predetermined reference value that corresponds to the intake air amount that does not cause torque shock, and together with MAD that represents the auxiliary air flow rate, fuel supply stop timing and resumption of fuel supply during deceleration fuel cut. Is an important parameter that determines timing,
By setting this LFC to an appropriate value, it is possible to change the torque so that each shock during fuel cut and during recovery can hardly be felt.

That is, when shifting to the deceleration fuel cut state, M
It is possible to perform the fuel cut after the AD (auxiliary air flow rate) decreases from the time of idling and the torque sufficiently decreases, and it is possible to suppress the torque step feeling (fuel cut shock) before and after the fuel cut. Also, when recovering, MA
The fuel supply can be restarted before the magnitude of D (auxiliary air flow rate) increases to the level equivalent to idling, and a lower torque is generated, and a stepped feeling of torque when recovering from fuel cut (recovery shock). ) Can be suppressed.

It should be noted that the proper value of LFC can be obtained by setting the upper limit to about 1/2 of the auxiliary air flow rate at the time of idling, but the important point is that fuel cut shock and recovery shock are not generated. It suffices to correspond to the appropriate auxiliary air flow rate of
It is rational to obtain it by experiment.

FIG. 8 is a flowchart showing an ignition timing correction routine, and this routine is executed once every 1/2 rotation.

This routine is intended to improve the feeling of deceleration when the engine 1 is cold or in the middle of warming up so as to be slower than that after warming up.

First, at P ₅₁ , the basic ignition timing ADV ₀ is obtained by performing a table lookup with the rotation speed N and the basic injection amount Tp as parameters, and at P ₅₂ , it is determined whether or not the throttle valve 7 is fully closed. When fully closed, the duty value MAD of the control signal Sv is compared with the ignition correction determination level LAH at P ₅₃ , and MAD ≧ LAH
In this case, the ignition correction amount HADV is calculated in P ₅₄ according to the following equation.

HADV = KA * (MAD-LAH) ... However, KA is set to a constant value in the ignition correction coefficient formula, and matching is performed to the extent that deceleration feeling immediately after the throttle valve is fully closed is obtained. Also, MAD <LA
When H, HADV = 0 at P ₅₅ . On the other hand, the process proceeds to P ₅₅ when the throttle valve 7 in step P ₅₂ is not fully closed. Next, at P ₅₆ , the ignition timing ADV is calculated according to the following equation.

ADV = ADV _0- HADV ... Further, at P ₅₇ , this ignition timing ADV is compared with −15 °,
ADV <When the -15 ° to ADV = -15 ° at P _58, A
If DV ≧ −15 °, the routine is ended as it is. The reason why the ADV is limited to -15 ° or more is to prevent abnormal heating of the exhaust purification catalyst because retardation may cause misfire.

In this way, by correcting the ignition timing as well, the engine 1
It is possible to obtain a comfortable feeling of deceleration even in deceleration under conditions such as cold where warm-up has not ended. Fig. 9
As shown in (a) and (b) in comparison with the conventional example, it is found that the torque difference between hot and cold is small. Incidentally, conventionally, the feeling of deceleration is delayed as compared with the present embodiment, as shown in FIG.

FIGS. 10 (a) to 10 (e) are timing charts of air flow rate control.

When the deceleration is started at a predetermined timing as shown in FIG. 10 (a), the basic injection amount Tp sharply decreases as shown in FIG. 10 (c) due to the sudden decrease in the intake air amount, As it approaches zero, the smoothed value LTp and the difference value DTp also change as shown. At this time, the duty value MAD of the control signal Sv is first set to DTp as shown in FIG.
It is given by × KFD, and when the value becomes less than LLG, it linearly approaches zero. As a result, the value of MAD that represents the auxiliary air flow rate during deceleration temporarily increases immediately after the start of deceleration, and then gradually decreases until it reaches a predetermined value that is smaller than the auxiliary air flow rate during idling. And MAD <
The fuel cut will be performed when it becomes LFC. Therefore, as shown in FIGS. 10 (b) and 10 (e), the fuel cut shock becomes extremely gentle as compared with the conventional case, and the jerky feeling of the vehicle is avoided, and the drivability is greatly improved. That is, the feeling of deceleration during deceleration becomes smooth.

Further, it is possible to prevent the problem that the air-fuel mixture is concentrated excessively due to the fuel adhering to the inside of the manifold during deceleration as the air flow rate increases, which also leads to the optimization of the combustion state. On the other hand, since the same air flow rate control is performed at the time of recovery, the recovery shock can be made smooth as shown in the comparison with the prior art.

Further, in the present embodiment, in the program shown in FIG. 4, the air amount at the time of idling is obtained by the calculation of MAD = NMA + HID, but NMA is given by the characteristic that it increases as the rotational speed decreases. Therefore, when the rotation speed decreases, the air flow rate automatically increases and the generated torque increases. As a result, in this embodiment, there is an effect that the engine stalling resistance and the idle stability can be enhanced.

In addition, in the above-described embodiment, since the air flow rate is smoothly increased and decreased in addition to the smooth change of the torque, it is possible to give a shock that is hardly felt by the driver. Therefore, it is not limited to the example in which the sub passage 9 is duty-controlled, and in many cases, for example, even if the sub-passage 9 is stepwise controlled, it may be practically acceptable. In that case, the flow rate control valve 10 may be a binary switch of ON / OFF instead of finely controlling the flow rate, and by doing so, a low cost system can be realized.

(Effect) According to the present invention, it is possible to sufficiently reduce the amount of reduction of the generated torque at the time of shifting to the deceleration fuel cut state, and reduce the feeling of step (fuel cut shock) before and after the fuel cut.

In addition, the amount of increase in the generated torque when returning from the deceleration fuel cut state can be made sufficiently small, and the step feeling (recovery / shock) before and after the fuel cut return can be reduced.

Therefore, both the fuel cut shock and the recovery shock can be reduced.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 10 are diagrams showing an embodiment of the present invention, and FIG.
FIG. 4 is a flow chart showing the basic injection amount calculation routine, FIG. 4 is a flow chart showing the air flow rate control routine, FIG. 5 is a diagram showing the characteristic of the basic duty value NMA, and FIG. 6 is a deceleration air increase coefficient KFD. 7 is a flow chart showing the final injection amount calculation routine, FIG. 8 is a flow chart showing the ignition timing correction routine, and FIG. 9 is a flow chart showing the operation when the ignition timing is corrected. FIG. 10 and FIG. 10 are views for explaining the action of the air flow rate control. DESCRIPTION OF SYMBOLS 1 ... Engine, 4 ... Injector (fuel supply means), 8 ... Valve opening degree sensor (opening degree detection means), 12 ... Intake operation means, 14 ... Operating state detection means, 20 ... Control unit (Fuel supply means, determination means, intake control means, command means).

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area F02D 41/12 315 8011-3G

Claims (1)

[Claims] 1. An a) opening detecting means for detecting an opening of a throttle valve interposed in an intake passage of the engine, b) an operating state detecting means for detecting an operating state of the engine, and c) an operating of the engine. Fuel supply means for supplying fuel to the engine based on the state; d) determination means for determining transition to the deceleration fuel cut state when the throttle valve is in the fully closed state; and e) transition to the deceleration fuel cut state. Occasionally, an intake control means that outputs a control signal to reduce the intake air amount to the engine from that at the time of idling, and outputs a control signal to increase the intake air amount to the engine at the time of idling when returning from the deceleration fuel cut state. F) is interposed in a sub-passage communicating with the upper and lower flow paths of the throttle valve,
Intake operation means for increasing / decreasing the intake air amount to the engine based on the control signal output from the intake control means; and g) a signal value representing the intake air amount when shifting to the deceleration fuel cut state, When compared with a predetermined reference value corresponding to the intake air amount that does not cause torque shock, and when the signal value falls below the reference value, the fuel supply means is instructed to stop the fuel supply, while the signal value A combustion control device for an internal combustion engine, comprising: a command means for outputting a command signal for instructing the fuel supply means to restart fuel supply when the value exceeds a reference value.