JPH0458026A - Intake air quantity control device - Google Patents

Abstract

PURPOSE:To increase the quantity of intake air of an engine to reduce consumption of lubricating oil when the operation of a fuel injection valve is stopped, and the engine speed is above a specified value larger than the fuel cut-off minimum engine speed. CONSTITUTION:Whether the present engine speed NE is larger than the fuel cut-off minimum engine speed NC or not is judged, and when NE>NC is established, it is then judged whether A/N is smaller than the second fuel cu-off intake air quantity A/N2 or not, where, A/N2 is a value larger than the fuel cut-off minimum intake air quantity A/N1. When A/N<A/N2 is established, it is judged whether the engine speed NE is larger than a high speed region-fuel cut-off engine speed NS higher than the fuel cut-off minimum engine speed NC, or not. When NE>NS is established, a flag FOC of increasing of the quantity of intake air is taken as 1, and increasing of the quantity of intake air is performed by opening both an EGR valve 28 and an ISC valve 10.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an intake air amount control device employed in automobile engines and the like.

<Prior art> Generally, electronic fuel injection devices (ElectronicC
Controlled Fuel Injection
In an engine system equipped with a device (hereinafter referred to as ECI), fuel injection valves are driven and controlled so that the mixture ratio during normal driving is close to the stoichiometric air-fuel ratio. During deceleration driving on a downhill slope, etc., fuel cut-off, that is, driving of the fuel injection valve is stopped, in order to prevent melting of the catalyst due to excessive temperature rise and to reduce fuel consumption.

FIG. 5 shows an engine speed-output diagram in a conventional engine system.

The fuel cut is performed when the driver does not press the accelerator pedal at all or presses it lightly (deceleration state). In addition, the area of fuel cut is indicated by hatching in the figure.

In the figure, Nc is the minimum fuel cut rotation speed, and if the engine speed is below this, there is a risk of stalling, so fuel cut is not performed, and A/N is the fuel cut minimum intake amount. Therefore, fuel cut is not performed even if the intake air amount per cycle of one cylinder, that is, the filling efficiency (hereinafter referred to as A/N) is greater than this. This means that when the engine load increases, the A/N This is because the magnitude of the load is determined by A/H since the load also increases.

<Problem to be Solved by the Invention> In designing an engine system, reducing the amount of lubricating oil consumed per unit mileage is an important issue.

In particular, when driving at high speeds where the engine speed is high, the amount of lubricating oil consumed increases, necessitating frequent refueling, and improvements have been desired.

FIG. 6 is a graph showing the relationship between engine load and lubricant consumption in a bench test. As shown in the figure, the amount of lubricating oil consumed is greater in all operating ranges when fuel is injected (indicated by the solid line) than when fuel is cut (indicated by the broken line).

Therefore, it can be said that fuel cut is an effective means of reducing lubricant consumption.

However, in a fuel cut in a low load range, the amount of intake air is small and no combustion occurs, so the negative pressure inside the combustion chamber becomes large. As a result, there is a problem in that the lubricating oil in the crankcase is sucked up into the combustion chamber, impairing the effect of reducing lubricating oil consumption. Therefore, it has been considered to increase the amount of intake air and reduce the negative pressure during fuel cut.

However, when this was done in the low rotation range, there was a different problem in that the engine brake became less effective.

The present invention was made in view of the above situation, and an object of the present invention is to provide an intake air amount control device that increases the intake air amount when fuel is cut in a high rotation range, thereby reducing lubricating oil consumption.

Means for Solving the Problem> Therefore, in the present invention, in order to solve this problem, the drive of the fuel injection valve is stopped, and the engine speed is equal to or higher than a predetermined value that is higher than the minimum fuel cut speed. We propose an intake air amount control device that increases the intake air amount of the engine when The pressure inside the combustion chamber increases and lubricant consumption due to suction is reduced. Additionally, since the intake air volume is not increased in the low rotation range, engine braking can be used as before.

Practical example An embodiment of the present invention will be specifically described based on the drawings.

FIG. 1 conceptually shows an embodiment of hardware in a gasoline engine system that employs the intake air amount control device according to the present invention, and FIGS. 2 and 3 show control flowcharts of this embodiment. It is. Further, FIG. 4 shows an engine rotation speed-output diagram in this embodiment.

In FIG. 1, E is an in-line 4-cylinder DOHC-type automotive engine with ECI, and an intake pipe 3 with an air cleaner box 2 attached to the upstream side of the intake manifold 1 is connected via a surge chamber 4. ing. The air cleaner box 2 houses an air cleaner 5, and is also provided with a Karman vortex type air flow sensor 7 in which an atmospheric pressure sensor 6 is integrated, and an intake air temperature sensor 8. The intake pipe 3 includes a throttle valve 9 driven by an accelerator wire (not shown), and a bypass type IS.
C (Idle 5peed Control) Valve 1
0 is provided. In the figure, 11 is FI AV (Fast Idl-e A) for promoting warm-up operation.
ir Valve) and is incorporated into the ISC valve 10.

The throttle valve 9 is provided with a potentiometer-type throttle position sensor 12 and an idle switch 13, and the opening degree information and idle state detection information of the throttle valve 9 are sent to the ECU, which is the control center in this embodiment.
(Electronic Control Unit
) is sent to 14. Incidentally, detection signals from each of the aforementioned sensors 6, 7, and 8 are also sent to the ECU 14. The ISC valve 10 is configured such that a built-in step motor 10a rotates in response to commands from the ECU 14, and the amount of intake air during idling operation is increased or decreased.

The engine E of this embodiment is a so-called MPI (Multi
The intake manifold 1 is equipped with as many fuel injectors (hereinafter abbreviated as injectors) 15 for the number of cylinders. The injector 15 is duty-driven by a command from the ECU 14 via an injector driver (not shown). Coolant temperature sensor 16 for engine E
．． In addition to the knock sensor 17, the crank angle sensor 18 and T
DC (Top Ded Center) sensor 19
Detection signals from these sensors 16 to 19 are also input to the ECU 14.

An 02 sensor 21 that detects the oxygen concentration in exhaust gas is attached to the exhaust manifold 20, and its detection signal is
Sent to CU14.

A main muffler 24 is connected to the downstream side of the exhaust manifold 20 via an ohm-up catalytic converter 22 and a catalytic converter (catalyst) 23 .

In the figure, 25 is a spark plug, and 26 is a spark plug 25.
This is an ignition coil that supplies high-voltage current to the ignition coil. Note that the ignition coil 26 is driven by the ECU 14 via an ignition driver (not shown).

Next, in FIG. 1 for explaining the EGR (exhaust gas recirculation) system in this embodiment, 27 is an exhaust gas extraction pipe, which communicates the exhaust manifold 20 and the EGR valve 28.

The EGR valve 28 is a valve for supplying exhaust gas to the intake manifold 1 via an exhaust gas introduction pipe 29, and is operated by negative pressure from a negative pressure extraction pipe 30 connected to the surge chamber 4. A solenoid valve 31 that is duty-driven by the ECU 14 is provided in the conduit of the negative pressure outlet pipe 30, and an appropriate amount of exhaust gas is introduced into the intake pipe 3. In the figure, reference numeral 32 denotes an atmospheric air outlet pipe that communicates the EGR valve 28 with the upstream side of the throttle valve 9. An orifice 33 is provided in the pipe to gradually introduce atmospheric air into the negative pressure intake by the solenoid valve 31. It is provided.

The control of this embodiment will be explained below with reference to the flowcharts of FIGS. 2 and 3. Note that symbols indicating control step stages in the flowchart (Sl, S2..., Ml, M
2...) corresponds to the symbol written at the end of the explanatory text.

In the engine system of this embodiment, control is started by turning on an ignition key (not shown).

Immediately after the engine starts, the ECU 14 receives signals from the crank angle sensor 18 and TDC sensor 19, and controls fuel injection for each cylinder (crank interrupt routine) as shown in FIG.
will be held.

When fuel injection control is started, the ECU 14 first calculates the A/N based on the output signals of the air flow sensor 7 and the crank angle sensor 18.
...When S1A/N is calculated, ECtJ 14
Next, it is determined whether or not a fuel cut flag FFo, which will be described later, is 1, that is, whether or not a fuel cut should be performed. ...s2 If FFo is not 1 in step S2, the ECU 14 uses A based on data from the air flow sensor 7, crank angle sensor 18, etc.
/N, and calculate the basic drive time T8 of the injector 15 so that the air-fuel mixture has the stoichiometric air-fuel ratio.
...=S3 Next, the basic drive time TB
is multiplied by the air-fuel ratio correction coefficient K, which will be described later, and then the injector 1
5 activation delay time T. Add to target drive time T I N
Calculate J.

T INJ = K X Ta + Tc,
-1, S4 When the target drive time T I N J is obtained, the ECU 14 drives the injector 15 via the injector driver.

...S5 Note that if FFC=1 in step S1, EC
U14 does not drive the injector 15, and fuel is cut.

The fuel cut control shown in FIG. 3 will be explained below.

After starting the fuel cut control, the ECU 14 first reads operating data from various sensors, and calculates an air-fuel ratio correction coefficient based on the cooling water temperature WT, intake air temperature, etc. AT. Then, E is calculated based on engine speed N, cooling water temperature WT, etc.
The opening degree of the GR valve 28, that is, the target drive duty ratio of the solenoid valve 31 is calculated, and the amount of bypass air, that is, the target opening amount P of the ISO valve 10 is determined based on the engine speed NE and the state of the idle switch 13. Configure settings.

--M1 to M4 Next, in the ECU 14, the current engine rotation speed N is the fuel cut minimum rotation speed N. Determine whether the value is greater than or not.
...M5 step NE>N in M5
c, the ECU 14 next determines whether A/N is smaller than the second fuel cut intake air amount A/N2. The second fuel cut intake amount A/N2 is the fuel cut minimum intake amount A/N.
, which is a larger value and is a value for determining a load state that cannot be felt even if a fuel cut is performed at a high speed range fuel cut rotation speed Ns, which will be described later. In this embodiment, as shown in FIG. 4, the second fuel cut intake air amount A/
N2 is the output O1, that is, the current state is maintained.・-・M6 step A/N at M6
<A/N 2, the ECU 14 next determines that the engine speed NE is higher than the fuel cut minimum speed Nc (
For example, it is determined whether or not the high speed range fuel cut rotation speed N5 (about 3000 rpm) is higher than the high speed range fuel cut rotation speed N5.

...M7 If N,>N5 in step M7, ECU1
In step 4, the intake air increase flag F0° is set to 1. In this embodiment, the intake air amount is increased by opening both the EGR valve 28 and the ISC valve 10.
- M8 Next, the ECTJ14 sets the value of a built-in fuel cut timer (hereinafter abbreviated as "timer"), not shown, to a set value T5 (for example, 10 to 20 seconds), while setting the fuel cut flag FF.

Let be 1. Then, in the interrupt routine of the fuel injection control described above, the injector 15 is not driven and the fuel is cut.

--M9. MIO Next, the ECU 14 determines whether the intake air increase flag F0° is 1 or not. ...-Mll Here, since the intake air increase flag F0° is set to 1 in step M8 described above, the ECU 14 changes the drive duty ratio I)ou of the solenoid valve 31 to the preset opening duty ratio D.
OPEN and drive the EGR valve 28.

Further, the opening amount P5 of the ISC valve 10 is also the target opening amount P.

A predetermined value ΔP is added to the step motor 10.
Drive a. As a result, the negative pressure inside the combustion chamber is reduced and oil leakage is prevented. In addition, here ISC valve 10
The valve opening amount P5 may be a predetermined valve opening amount P1 set in advance. -・M12. M13 If Nl:≦No in step M5, or step M6
If A/N≧A/N2, there is a risk of engine stalling and acceleration shock after fuel cut, so fuel cut is not performed, and intake air amount increase is not necessary, so naturally, it is not performed.

ECU 14 first sets intake increase flag F. C is set to 0, the value of timer T is reset to T5, and then the fuel cut flag FFc is set to 0. As a result, in the above-described fuel injection control interrupt routine, steps 83 to
In S5, the injector 15 is driven and fuel is injected.

-・-M14 to M16 Next, the process moves to step Mll, but since Foo-○, EC1J 14 is the drive duty ratio of the solenoid valve 31. EG as the target drive duty ratio obtained earlier by UT
Drive the R valve 28 to open the ISC valve 10 by the opening amount P5.
is the target valve opening amount P obtained earlier. Close step motor 10
Drive a.・-M17. M2S On the other hand, if N≦N5 in step M7, that is, the engine speed NE is the minimum fuel cut speed N. and the high-speed range fuel cut rotation speed N5, the ECU 14 first sets the intake increase flag F. Let 0 be O. This is because the amount of intake air is not increased during fuel cut outside the high speed range.

...M19 Next, the ECU 14 determines whether or not the idle switch 13 is in the ON state, and if it is in the ON state, the driver does not press the accelerator pedal at all, so the process moves to step M9. Fuel cut is performed through steps MIO to M13. -M20 When the idle switch 13 is in the OFF state in step M20, the ECU 14 next sets the A/N to the minimum intake air amount A/N for fuel cut.

Determine whether it is smaller. And A/N≧A/N
, the process moves to step M15, and the timer T
The value of is reset to T5 and fuel is injected.
-M21 In step M21, A/N<A/N.

If so, the ECU 14 next determines whether the value of the timer T is 0, that is, whether the countdown has ended, and if T>0, the process moves to step M16 to inject fuel. I do. When entering this operating range from another operating range, the initial value of timer T is always T5 as described above. ...M22 Step M22 When the countdown ends and T=O, the fuel cut flag FFc is set to 1 and the fuel is cut.In this operating range, the fuel is cut to prevent the catalyst 23 from melting. By providing a timer T, the start of the timer is delayed, thereby preventing acceleration delay when the accelerator is depressed and acceleration shock when returning.・・・
・M23 In this example, the operating range in which fuel cut is performed is the fourth
As a result of expanding the engine speed-output diagram as shown in the figure, and increasing the amount of intake air during fuel cut in the operating range above the high speed range fuel cut speed Ns,
Lubricating oil consumption has been significantly reduced.

Although the description of the specific embodiment is completed above, the aspect of the present invention is not limited to this embodiment.

For example, in the above embodiment, the ISC valve 10 and the EGR valve 28 are used to increase the amount of intake air when fuel is cut in the high rotation range, but it is also possible to use a method such as driving the throttle valve 9 in the opening direction. Good too. Alternatively, the operating range in which fuel is cut may not be expanded, and the intake air amount may be increased only when fuel is cut at a predetermined engine speed or higher. In this case, the second fuel cut intake air amount A/N2 is not set, and step M6 in the fuel cut control in FIG.
etc. are of course unnecessary.

<Effects of the Invention> According to the present invention, since the amount of intake air is increased when fuel is cut in the high engine speed range, lubricating oil consumption is reduced, and maintenance intervals are extended and running costs are reduced. It has the following effects.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram showing the hardware configuration of an embodiment of a gasoline engine system employing an intake air amount control device according to the present invention, and FIGS. 2 and 3 are control flowcharts in the embodiment. FIG. 4 is an engine rotational speed output diagram in the embodiment. FIG. 5 is a conventional engine speed-output diagram, and FIG. 6 is a graph showing the correlation between load and lubricating oil consumption. In the drawing, E is the engine, 1 is the intake manifold, 3 is the intake pipe, 10 is the ISC valve, 10a is the step motor, 14 is the ECU, 15 is the fuel injector, 28 is the EGR valve, 31 is the solenoid valve, A/Nl is the fuel cut minimum intake amount, A/N2 is the second fuel cut intake amount, Nc is the fuel cut minimum rotation speed, and N5 is the fuel power rotation speed. is high speed range

Claims (1)

[Claims] An intake air amount control device that increases the intake air amount of the engine when the drive of the fuel injection valve is stopped and the engine rotational speed is equal to or higher than a predetermined value that is greater than the minimum fuel cut rotational speed. .