JPS62150046A - Fuel control device of multi-cylinder engine - Google Patents

Abstract

PURPOSE:To prevent after-burn which occurs at fuel resumption by guiding replenishment air into partial cylinders at fuel cut for deceleration and to prevent an abrupt torque fluctuation at fuel resumption by augmentatively correcting the fuel feed quantity to these cylinders at fuel resumption. CONSTITUTION:During the engine operation, when an engine is judged to be in a fuel cut condition for deceleration by a control unit 100 based on outputs of a throttle opening sensor 24 and a rotating speed sensor 30, fuel injection to cylinders 2, 3 is cut. A solenoid control valve 31 is controlled to feed replenishment air to partial cylinders 2, 3 for a predetermined time via an air guide passage 32 and branch passage sections 12b, 12c. When it is subsequently judged that the fuel resumption condition is resumed, the solenoid control valve 31 is closed, and fuel injection valves 25b, 25c are controlled to feed augmented fuel to these cylinders 2, 3 as compared with other cylinders 1, 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to controlling the amount of fuel supplied to each cylinder during engine operation in order to maintain a predetermined air-fuel ratio of the air-fuel mixture combusted in each cylinder of the engine. Is the fuel side of a multi-cylinder engine controlled according to the state? Regarding B device.

(Prior Art) Conventionally, as a technology related to engines installed in automobiles, etc., for example, when the engine rotation speed is above a predetermined value,
In addition, when the throttle valve linked to the accelerator pedal is brought to a substantially fully closed state (idling opening state), the fuel supply is stopped, so-called deceleration fuel cut, and after such deceleration fuel cut, the engine speed is reduced to a predetermined value. When it is less than
Alternatively, it is known to improve fuel efficiency and reduce harmful components contained in exhaust gas by restarting fuel supply when the throttle valve is opened from a substantially closed state, so-called fuel recovery. It is being

However, in an engine in which the deceleration fuel is cut and the subsequent fuel restoration JM is performed as described above, when the deceleration fuel is cut, the deceleration fuel that adheres to the intake passage and remains is supplied before the deceleration fuel is cut. A part of the fuel f4 will evaporate, but the air-fuel mixture formed by this evaporated fuel ratc will not be exhausted in the combustion chamber, but will be discharged to the exhaust passage and remain there, causing subsequent fuel recovery. At the time of W, the raw air-fuel mixture remaining in the exhaust passage is ignited by the high-temperature combustion gas that is burned in the combustion chamber and discharged into the exhaust passage, causing rapid combustion in the exhaust passage, resulting in so-called afterburn. There is a risk that this will occur. The occurrence of such afterburn not only reduces the operating performance of the engine, but also causes problems in that it reduces the durability of various parts forming the exhaust system of the engine.

Therefore, in order to suppress the afterburn that occurs when the fuel is restored as described above, for example,
As shown in the publication, when fuel is cut during deceleration, supplementary air is introduced into the cylinder through the downstream part of the intake passage from the throttle valve, thereby reducing the amount of non-QJ that remains in the exhaust system and causes afterburn. It is known to reduce aiki by 9j%. When implementing this kind of replenishment air exclusively for the cylinders that open during deceleration fuel cut in a multi-cylinder engine used in practical use, replenishment air is not introduced to all cylinders, but only to some cylinders. It has been considered to suppress the occurrence of afterburn as described above by introducing supplementary air.

(Problem to be Solved by the Invention) However, as described above, in a multi-cylinder engine, when supplementary air is introduced only into some cylinders during deceleration fuel cut, the air-fuel ratio is not set to a predetermined value. In order to avoid this problem, if the fuel supply amount was set according to the engine operating condition when the fuel was restored, that is, based on the engine speed and the amount of intake air detected by the air flow meter, supplementary air would be introduced during deceleration fuel cut. In the cylinder, when the fuel is restored, the air that was introduced immediately before remains, and the air-fuel ratio of the mixture combusted in the cylinder may shift to the lean side compared to other cylinders. arise. and,
As a result, combustibility in the cylinders into which supplementary air was introduced during the deceleration fuel cut is deteriorated, and shocks (torque fluctuations) are more likely to occur when the fuel is restored, which may result in deterioration of driving performance.

In view of the above, the present invention provides a system in which deceleration fuel is cut and then fuel is restored under operating conditions that satisfy predetermined conditions, thereby improving fuel efficiency and purifying exhaust gas. This is due to the fact that supplementary air is introduced into some cylinders at the time of cut, suppressing afterburn that occurs when fuel is restored, and supplementary air is introduced into some cylinders during deceleration fuel cut. It is an object of the present invention to provide a fuel control device for a multi-cylinder engine that avoids the occurrence of rapid torque fluctuations when the fuel is restored.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a fuel control device for a multi-cylinder engine according to the present invention is provided with an engine fuel control device having a plurality of cylinders, as shown in FIG. Based on the operating state detection means that detects the operating state of the engine, and the detection output obtained from the operating state detection means, the amount of fuel supplied according to the operating state of the engine is set, and the amount of fuel supplied to multiple cylinders with the set amount of fuel supplied is set. a fuel supply means that supplies fuel to the engine and stops the fuel supply when the operating state of the engine represented by the detection output obtained from the operating state detection means satisfies a predetermined condition; and the fuel supply means stops the fuel supply. In this case, the fuel increase correction means includes an air introduction means for introducing supplementary air into some of the plurality of cylinders, and a fuel increase correction means provided in association with the fuel supply means, and the fuel increase correction means adjusts the fuel supply. When the means restarts fuel supply after stopping, it is configured to perform control such that the amount of fuel supplied to some cylinders is larger than the amount of fuel supplied to other cylinders.

(Function) In the fuel control device for a multi-cylinder engine according to the present invention configured as described above, when the fuel supply means stops supplying fuel to each cylinder, the air introducing means supplementary air is supplied to the When the fuel supply means resumes fuel supply to each cylinder, the fuel increase correction means increases the amount of fuel supplied to some cylinders to which supplementary air is supplied. This prevents the air-fuel ratio of the air-fuel mixture in some cylinders to which supplementary air has been supplied from shifting toward the lean side when fuel supply is restarted, that is, when fuel is restored.
Afterburn and sudden torque fluctuations that occur when fuel is restored can be suppressed.

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

FIG. 2 shows an example of a fuel control device for a multi-cylinder engine according to the present invention, together with an engine to which the device is applied.

In FIG. 2, the engine body 10 has four cylinders 1.
2.3 and 4 are provided, and each of these cylinders 1 to 4 has a branch passage portion 12 forming a downstream portion of the intake passage 12.
a, 12b, 12c, and 12d are connected via an intake valve (not shown), and a branch passage forming the upstream portion of the exhaust passage 14 in which the catalytic converter 15 and the silencer 16 are provided is connected to the exhaust valve (not shown). ) are connected through.

An air filter 17 is provided on the upstream side of the intake passage 12, and the intake air that is purified by the air filter 17 and introduced into the intake passage 12 is filtered through the intake passage 12. The air is guided to each of the branch passages 122 to 12d through an air flow meter 18 that detects the intake air amount, a throttle valve 20 that is linked to an accelerator pedal, and a surge tank 22. Each branch passage section 122
At predetermined positions of ~12d, injection pulse signals Cp and Cp' supplied from the control unit 100, which will be described later.
The fuel injection valve 25a opens and closes according to the fuel supply system, and injects pressure-regulated fuel from the fuel supply system toward the intake boat at a predetermined timing.

25b, 25c and 25d are temporarily installed.

Further, each cylinder 1 to 4 is provided with a spark plug 27, and each spark plug 27 receives a predetermined ignition from a distributor 28 whose rotating shaft is rotationally driven by the crankshaft of the engine body 10. High-pressure pulses are distributed and supplied according to the order, and each spark plug 27 emits a spark when this high-pressure pulse is supplied to each cylinder 1.
-4 is adapted to ignite the air-fuel mixture supplied.

The distributor 28 is provided with a rotation speed sensor 30 that detects the engine rotation speed corresponding to the rotation speed and rotation angle of the rotating shaft.

In addition to this configuration, a four-person air passage 32 that is opened and closed by an electric CD control valve 31 is connected to the branch passages 12b and 12C, and the opening and closing of this four-person air passage 32 is controlled and the fuel injection valves 25a to 25a are controlled. 25d opening/closing side? A control unit 100 for performing 1ff is provided.

The control unit 100 includes an air flow meter 1
A detection signal Sa corresponding to the intake air amount obtained from the rotation speed sensor 30, a detection signal Sn corresponding to the engine rotation speed and crank angle obtained from the rotation speed sensor 30, and a throttle opening sensor 24 that detects the opening of the throttle valve 20. A detection signal 3t corresponding to the open/closed state of the throttle valve 20 obtained from the throttle valve 20 is supplied.

The control unit 100 controls each detection signal Sa, Sn
and St, when the engine is in a normal operating state, the detection signal Sa is set to the current intake air amount so that the air-fuel ratio of the air-fuel mixture supplied to each of cylinders 1 to 4 is set to a predetermined value. The fuel injection amount is calculated based on the engine rotational speed at which the detection signal Sn is detected, and injection pulse signals Cp and Cp' having pulse widths corresponding to the calculated fuel injection amount are formed. fuel injection valve 2
5a and 25d, and also supplies the injection pulse signal Cp'' to the fuel injection valves 25b and 25c at a predetermined timing.As a result, the fuel injection valves 25a and 25d respond to the pulse width of the injection pulse signal Cp. Open only for the time,
Further, the fuel injection valves 25b and 25c are opened for a time corresponding to the pulse width of the injection pulse signal Cp'', and an amount of fuel corresponding to the operating state of the engine is injected into each fuel injection valve 25a to 25c.
It is injected from 25d toward the intake boat section.

Furthermore, based on the detection signals St and Sn, the control unit 100 controls the fuel injection valves 25a to 25d when the throttle valve 20 is in a substantially fully closed state and the engine speed is above a predetermined value. The supply of injection pulse signals Cp and Cp' is stopped. As a result, cylinders 1 to 4
The fuel supply to the engine is cut off and a deceleration fuel cut is performed. Control unit 100 further supplies air introduction signal CO to electromagnetic control valve 31 for a predetermined period of time in synchronization with the start of this deceleration fuel cut. As a result, the electromagnetic control valve 31 is opened, and supplementary air is blown into the branch passages 12b and 12C via the air introduction passage 32, and introduced into the cylinders 2 and 3 via the branch passages 12b and 12C. Ru.

In this way, when the throttle valve 20 is changed from a substantially fully closed state to an open state while supplementary air is being introduced into cylinders 2 and 3 during deceleration fuel cut, or when the engine speed is less than a predetermined value. When this happens, the control unit 100 stops supplying the air introduction signal Co to the electromagnetic control valve 31, and calculates the fuel injection amount to perform fuel recovery. At this time, the control unit 100
For cylinders 1 and 4 to which supplementary air is not introduced via the air introduction passage 32, the fuel injection amount Qf is calculated based on the intake air amount and engine speed as described above. For cylinders 2 and 3 into which supplementary air has been introduced via the introduction passage 32, the corrected fuel injection amount is obtained by increasing the fuel injection amount Qf, which is set based on the intake air amount and the engine rotation speed. Calculate Qf'. Then, the control unit 100 controls the fuel injection amount Qf
An injection pulse signal Cp having a pulse width corresponding to the corrected fuel injection amount Ql is formed and supplied to the fuel injection valves 25a and 25d at a predetermined timing, and an injection pulse signal Cp having a pulse width corresponding to the corrected fuel injection amount Ql is generated. ' and supplies it to the fuel injection valves 25b and 25c at a predetermined timing for a predetermined period of time. As a result, an amount of fuel corresponding to the actual amount of intake air introduced into each of the cylinders 1 to 4 is supplied from each of the fuel injection valves 25a to 25d. The air-fuel ratio of the air-fuel mixture supplied to each of the air-fuel mixtures is prevented from deviating significantly from the target air-fuel ratio.

The control unit 100 that performs the above-described control is configured using, for example, a microcomputer, and an example of a program for fuel injection control executed by the microcomputer in such a case is shown in the flowchart shown in FIG. Refer to and explain.

This program starts when the engine is started, and after starting, first, initial settings are performed in process 101, and the deceleration flag Fa and increase flag Ft are set to 0, and the process proceeds to process 102. In the process 102, various detection signals Sa', Sn, and SL are manually generated. Subsequent decisions 103 and 104 determine whether the throttle valve 20 is substantially fully closed based on the detection signals St and Sn, respectively.
Then, it is determined whether the engine speed N is equal to or higher than a predetermined value N0, and when it is determined that the throttle valve 20 is in a substantially fully closed state and the engine speed N is equal to or higher than the predetermined value N0. In order to perform deceleration fuel cut, process 10
Proceed to step 5.

In process 105, after setting the deceleration flag Fa to 1, the process proceeds to decision 106. In decision 106, it is determined whether or not the deceleration flag Fa has changed from 0 to 1. If it is determined that the deceleration flag Fa has changed from 0 to 1, process 107
Proceed to. In process 107, a built-in timer (2) is started to start measuring a period (replenishment air introduction period) Ta during which supplementary air is introduced into cylinders 2 and 3 via the air introduction passage 32, and in subsequent process 108, an increase flag Ft is started. After setting it to O, proceed to decision 109. On the other hand, if it is determined in decision 106 that the deceleration flag Fa has not changed from 0 to 1, processes 107 and 10
Proceed to decision 109 without going through step 8. In decision 109, it is determined whether or not the replenishment air introduction period Ta has elapsed. If it is determined that the replenishment air introduction period Ta has not elapsed, the process proceeds to process 110. Process 1
10, an air introduction signal C is sent to the electromagnetic control valve 31.

and returns to process 102. As a result, the air introduction passage 32 and the branch passage portions 12b and 1 are connected to the cylinders 2 and 3.
Supplementary air is introduced via 2c.

Also, in decision 109, the supplementary air introduction period T
If it is determined that a has elapsed, process 1.11
, the supply of the air introduction signal Co to the electric drum control valve 31 is stopped, and the process returns to process 102. As a result, the supply of supplementary air to the cylinders 2 and 3 is blocked by the electromagnetic control valve 31.

On the other hand, in decision 103, the throttle valve 20
If it is determined that the engine is in an open state rather than a substantially fully closed state, or if it is determined in decision 104 that the engine speed N is less than a predetermined value No, process 112 is performed to restore fuel. Proceed to. Process 11
2, after stopping the supply of the air introduction signal Co to the electromagnetic control valve 31, the process proceeds to process 113, where the increase flag FL is set to 1, and the subsequent decision 11
4, it is determined whether the increase flag Ft has changed from O to 1. Here, if it is determined that the increase flag F has changed from 0 to 1, the process proceeds to process 115, and the built-in timer 2 is set to 1-star. The timer ■ is loaded with the fuel increase time T' in advance, and measures the remaining time Tf' to decrease as time passes after the fuel is restored.In the subsequent process 116, the deceleration flag Fa is set to O. After that, the process proceeds to process 117. If it is determined in decision 114 that the increase flag Ft has not changed from O to 1, the process proceeds to process 117 without going through processes 115 and 116.

In process 117, the fuel injection iQf is calculated based on the intake air amount that is detected by the detection signal Sa and the engine rotational speed that is detected by the detection signal Sn, and the process proceeds to decision 118. In decision 11, it is determined whether or not the fuel increase time T'f has elapsed. If it is determined that the fuel increase time T'f has not elapsed, the process proceeds to process 119. In the process 119, the remaining time Tf' of the fuel increase time Tf is read, and in the subsequent process 120, the remaining time Tf' of the fuel increase time Tf is read.
For example, the fuel injection amount Qf calculated in step 7 is added to the increase value.
After calculating the corrected fuel injection amount Qf' by adding Tl (K is a positive constant), the process proceeds to process 121. Here, since the remaining time Tf'' decreases with the passage of the fuel increase time, the increase value -Tf'' also decreases with the passage of the fuel increase time.

Then, in process 121, the fuel injection amount iQa for cylinders 1 and 4 is set to the fuel injection amount Qf calculated in process 117, and the fuel injection amount Qb for cylinders 2 and 3 is set to the corrected fuel injection amount Qf calculated in process 120. After setting the injection lQf', proceed to decision 122.

In decision 122, it is determined whether or not it is fuel injection time based on the crank angle at which the detection signal Sn appears. If it is determined that it is not fuel injection time, this determination is repeated and it is determined that it is fuel injection time. If so, proceed to process 123.

In process 123, an injection pulse signal C having a pulse width according to the fuel injection iQa set in process 121 is used.
After forming p and supplying it to the fuel injectors 25a and 25d, proceed to process 124. In process 124, an injection pulse signal Cp' having a pulse width corresponding to the fuel injection 11Qb set in process 121 is formed and supplied to the fuel injection valves 25b and 25c, and the process returns to process 102. As a result, cylinders 2 and 3 have cylinder 1
and 4, an increased amount of fuel is supplied.

On the other hand, in decision 118, fuel increase time Tf
If it is determined that the period has elapsed, the process proceeds to process 125, where both the fuel injection amount Qa for cylinders l and 4 and the fuel injection lQb for cylinders 2 and 3 are set to the fuel injection lQf calculated in process 117. , and sequentially executes the process 122 and subsequent steps described above. In this case, cylinders 1 to 4
The same amount of fuel will be supplied to each.

Fuel injection control by the control unit 100 and supplementary air introduction side 1ffO according to the program as described above.
For example, suppose that the throttle valve 20 is changed as shown in FIG. 4 while the engine is running, and the engine speed is accordingly changed as shown in FIG. 4B. , intake air amount (air flow meter 18
(detected amount horn).

The amount of supplementary air introduced into the cylinders 2 and 3 through the air introduction passage 32 and the amount of fuel injection change, for example, as shown in FIG. 4C, D, and E, respectively.

That is, when the throttle valve 20, which was previously open, becomes almost fully closed at this point, the intake air amount becomes close to zero, and the engine changes from the normal operating state to the decelerated operating state. be forced to migrate. At this time, since the engine speed N is equal to or higher than the predetermined value N0, deceleration fuel cut is performed to reduce the fuel injection amount to zero, and the introduction of supplementary air via the air introduction passage 32 is started. In this case, the introduction of supplementary air is performed for the supplementary air period Ta, and is stopped when the required amount of supplementary air is introduced, so that the engine speed N decreases and becomes less than the predetermined value No. Supplementary air is no longer introduced at time L2 before fuel return start time L3. Therefore, in such a case, at the fuel return start time t3, no supplementary air has been introduced, and no fuel increase correction is performed, and the intake air and engine speed for each of cylinders 1 to 4 are Fuel is supplied with fuel injection lQf set based on N.

Subsequently, when the throttle valve 20 is opened at time L4, the engine speed N increases, and the intake air amount and fuel injection amount increase accordingly. Then, at time t, when the throttle valve 20 is again brought into the substantially fully closed state C and the engine is forced to shift to the deceleration operating state, the engine speed N is greater than the predetermined value N0, so the deceleration fuel cut is performed. The fuel injection amount is set to zero. This deceleration fuel cut continues until time t6 when the throttle/nottle valve 20 is next opened, but the deceleration fuel cut time Tc leading to this time t is shorter than the supplementary air introduction period Ta, and the fuel At the return start time T6, supplementary air is being introduced into the cylinders 2 and 3.

Therefore, during the period from time t6 to time t, E
The corrected fuel injection amount Qf' is set by increasing the fuel injection amount 4JQf, which is set based on the intake air amount and the engine rotational speed N, as shown by the dashed line in FIG. , cylinders 2 and 3 are supplied with fuel using the corrected fuel injection ffj-Of'. Then, during the fuel increase time Tf from time t6 to time t7, the increase value for the fuel injection amount Qf decreases with the passage of time and becomes zero at time t7, so that the state at the time of fuel restoration is This means that the transition from the state to the normal operating state will occur smoothly.

In this way, at the time of transition from deceleration fuel cut I to fuel return, if supplementary air was introduced into cylinders 2 and 3 at the time of deceleration fuel cut, when the fuel is returned to cylinders 2 and 3, Since the fuel injection amount is corrected to increase, the air-fuel ratio of the air-fuel mixture supplied to cylinders 2 and 3 is prevented from shifting toward the lean side.

(Effects of the Invention) As is clear from the above description, according to the fuel control device for a multi-cylinder engine according to the present invention, deceleration fuel cut and subsequent fuel recovery are performed under an operating state that satisfies predetermined conditions. This not only improves fuel efficiency and purifies exhaust gas, but also introduces supplementary air into some cylinders during deceleration fuel cut, which suppresses afterburn that occurs when fuel is restored. Sometimes, the amount of fuel supplied to some cylinders to which supplementary air was introduced at the time of deceleration fuel cut is increased, so the air-fuel ratio of the mixture combusted in some cylinders may change due to the introduction of supplementary air. This prevents the air-fuel ratio from deviating to the lean side from the target air-fuel ratio. As a result, the occurrence of sudden torque fluctuations when the fuel is restored is avoided, and the operating performance of the engine is improved.

[Brief explanation of drawings]

Claims (1)

[Claims] An operating state detecting means for detecting the operating state of an engine having a plurality of cylinders, and a fuel supply amount corresponding to the operating state of the engine based on a detection output obtained from the operating state detecting means. a fuel supply means that supplies fuel to the plurality of cylinders with a fuel supply amount determined by the amount of fuel supplied to the plurality of cylinders, and enters a fuel supply stop state when the operating state of the engine represented by the detected output obtained from the operating state detection means satisfies a predetermined condition; and an air introducing means for introducing supplementary air into some of the plurality of cylinders when the fuel supply means assumes the fuel supply stop state, and after the fuel supply means assumes the fuel supply stop state. fuel increase correction means for controlling the amount of fuel supplied to some of the cylinders to be larger than the amount of fuel supplied to other cylinders when restarting the fuel supply; Control device.