JPH0458041A - Fuel injection control device - Google Patents

Abstract

PURPOSE:To increase the intervals of maintenance and to reduce the running cost by cutting fuel in a low load revolutional range of an engine so as to reduce the consumption of lubrication oil. CONSTITUTION:Just after starting of an engine, an ECU receives signals from a crank angle sensor 18 or a TDC sensor 19, and accordingly, controls fuel injection for each cylinder. When the fuel injection control is started, the ECU 14 at first calculates a charge efficiency from output signals from an air-flow sensor 7 and the crank angle sensor 18, and determines whether fuel is cut or not. Further, when the speed of the engine E is above a predetermined value which is a minimum revolutional speed at which fuel is cut, but below a predetermined value with which the intake-air volume of the engine E is larger than an intake-air volume with which fuel is cut, the drive of a fuel injection is stopped. Accordingly, since fuel is cut even in a high revolutional speed but low load range, it is possible to reduce the consumption of lubrication oil.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel injection control device employed in automobile engines and the like.

<Prior art> In general, electronic fuel injection
Controlled Fuel Injection
In an engine system equipped with a device (hereinafter referred to as ECI), the drive control of fuel injection valves is performed 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 rotation speed is lower than this, there is a risk of stalling, so the fuel cut is not performed. In addition, A/N+ is the minimum intake air amount for fuel cut, and 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, fuel cut is not performed. This is because - as the engine load increases, the A/N also increases, so the magnitude of the load is determined by A/H.

<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, lubricant consumption is relatively small in the medium load range.
It increases in the high load area and the low load area. Furthermore, the amount of lubricating oil consumed is greater when fuel is injected (indicated by the solid line) than when fuel is cut (indicated by the broken line). Therefore, it is effective to cut fuel as much as possible in high load ranges and low load ranges in order to reduce lubricant consumption. However, since the high load range occurs during acceleration and when the vehicle is on the pitch, it was naturally impossible to cut fuel. On the other hand, when the engine is rotating at a low speed, the increase rate when fuel is injected again after the fuel cut is large, causing an acceleration shock that causes discomfort to the occupants.

The present invention was made in view of the above situation, and an object of the present invention is to provide a fuel injection control device that cuts fuel in an operating range where there are no problems in terms of performance and experience, thereby reducing lubricating oil consumption. .

Means for Solving the Problem> Therefore, in the present invention, in order to solve this problem, the engine rotation speed is equal to or higher than a predetermined value that is greater than the fuel cut minimum rotation speed, and the intake air amount of the engine is set to a fuel cut-off value. The present invention proposes a fuel injection control device characterized in that a fuel injection valve is stopped when the intake air amount is below a predetermined value that is larger than the minimum intake air amount.

<Function> In addition to the normal fuel cut, the fuel cut rate is also performed in the high rotation and low load operating range, so lubricating oil consumption is reduced.

<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 a fuel injection 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. An air cleaner 5 is housed in the air cleaner box 2, and an air flow sensor 7 of Karman vortex type in which an atmospheric pressure sensor 6 is integrated, and an intake air temperature sensor 8 are provided. The intake pipe 3 includes a throttle valve 9 driven by an accelerator wire (not shown) and a bypass type I
In Figure 0, an SC (Idle 5peed Control) valve 10 is provided, and 11 is a FI AV (Fast Ide Ai) valve for promoting warm-up operation.
r 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 rsc valve 10 is configured such that a built-in step motor 10a rotates in response to commands from the ECU 14, and the intake air amount 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 a warm-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. 0 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. This is an atmosphere-takeout pipe that communicates with the upstream side of the valve 9, and an orifice is provided in the pipe to gradually introduce the atmosphere into the EGR valve 28 when the negative pressure takeout pipe 30 is closed by the solenoid valve 31. 33 are provided.

The control of this embodiment will be explained below with reference to the flowcharts of FIGS. 2 and 3. In addition, 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.・
...Once s1A/N is determined, the ECU 14 next determines whether or not a fuel cut flag FFC, which will be described later, is 1, that is, whether or not a fuel cut should be performed.

---s2 If Fpc 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 is determined, and the basic drive time T8 of the injector 15 is calculated so that the air-fuel mixture has the stoichiometric air-fuel ratio.
...S3 Next, the basic driving time T
Multiply B by an air-fuel ratio correction coefficient K, which will be described later, and further add the operation delay time To of the injector 15 to obtain the target drive time T I
Calculate NJ.

TINJ=KXTB+To−
S 4 When the target drive time T I N J is obtained, E
The CU 14 drives the injector 15 via an 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 fuel cut control, the ECU 14 first reads operating data from various sensors, calculates an air-fuel ratio correction coefficient based on AT such as cooling water temperature W and intake temperature, and then calculates an air-fuel ratio correction coefficient based on AT such as engine speed N5 and cooling E based on 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 N6 and the state of the idle switch 13. Configure settings.

...M1 to M4 Next, in the ECU 14, the current engine rotation speed Nl: is the fuel cut minimum rotation speed N. Determine whether the value is greater than or not.

...N at M5 step M5
If E>Nc, 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 air amount A/N2 is a value larger than the fuel cut minimum intake air amount A/Nl, and is a value for determining a load condition 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. It is. In this embodiment, as shown in FIG. 4, the second fuel cut intake air amount A/N2 is at the output O1, that is, the current load state is maintained. ...M6 If A/N<A/N2 in step M6, the ECU 14 next changes the engine speed N6. is the fuel cut minimum rotation speed N. taller than(
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 step In M7, N, >
If it is Ns, the ECU 14 next sets the intake increase flag F.
. Let C be 1. The intake air amount increase prevents oil from rising in the combustion chamber by reducing the negative pressure in the combustion chamber during fuel cut.

In this embodiment, the intake air amount is increased by opening both the EGR valve 28 and the SC valve 10.
...M8 Next, the ECU 14 sets the value of a built-in fuel cut timer (hereinafter abbreviated as "timer"), not shown, to a set value TS (for example, 10 to 20 seconds), while setting the fuel cut flag F'.

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 sets the intake increase flag F. Determine whether 0 is 1 or not. ...M11 Here, the intake air amount increase flag F is set in step M8 described above. 0 is 1
Therefore, the ECU 14 sets the drive duty ratio Dour of the solenoid valve 31 to the preset opening duty ratio DOPE□, and drives the EGR valve 28.

Further, the valve opening amount P5 of the ISC valve 10 is also the target valve opening amount PO.
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 P, , may be a predetermined valve opening amount P set in advance...M12. M13 step M
5, if N6≦No, or step M
If A/N≧A/N2 in 6, there is a risk of engine stall or acceleration shock after fuel cut.
There is no fuel cut, and there is no need to increase the amount of intake air, so of course there is no need to do so.

The ECU 14 first sets the intake air increase flag F0° to 0, resets the value of the timer T to TS, and then sets the fuel cut flag FFc to O. 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 it is Foc-〇, the ECU 14 uses the drive duty ratio of the solenoid valve 31. U
, the EGR valve 28 is driven with the target drive duty ratio determined earlier, and the step motor 10a is driven with the valve opening amount P5 of the ISC valve 10 also being set as the target valve opening amount P0 determined earlier. , -M17. On the M2S-1 side, if N≦N5 in step M7, that is, if the engine speed N is between the minimum fuel cut speed NC and the high speed range fuel cut speed N5, the ECU 14 first sets the intake increase flag. F. Let 0 be O. This is because, in this embodiment, 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. - M20 If the idle switch 13 is in the OFF state in step M20, the ECU 14 next determines whether A/N is smaller than the minimum intake air amount A/N for fuel cut. judge. And A
If /N≧A/N, the process moves to step M15, where the value of the timer T is reset to Ts and fuel is injected. -...M21 If A/N<A/N in step M21, the ECU 14 then uses the timer T.
It is determined whether the value of T is O, that is, whether the countdown has ended or not, and if T>0, the process moves to step M16 and fuel injection is performed. If the timer T
The initial value of is always T5. ...M22 Step M22, the countdown ends and T=O
In this case, a fuel cut is performed by setting the fuel cut flag FFo to 1. In this operating range, a fuel cut is performed to prevent melting of the catalyst 23, but by delaying the start by providing a timer T, the accelerator is This prevents delays in acceleration when stepping on the pedal and shock caused by acceleration when returning. ...M23 In this embodiment, the operating range in which the fuel is cut is expanded as shown in the engine speed-output diagram in FIG. 4, and as a result, the lubricating oil consumption is 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 during fuel cut in the high speed range, but other methods may be used.
It is not necessary to increase the amount of intake air itself.

<Effects of the Invention> According to the present invention, since fuel is cut in the low-load, high-speed range of the engine, lubricating oil consumption is reduced, and maintenance intervals are extended and running costs are reduced. be effective.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram showing the hardware configuration of an embodiment of a gasoline engine system employing the fuel injection control device according to the present invention, and Figures 2 and 3 are control flowcharts in the embodiment. , FIG. 4 is an engine rotation speed-output diagram in the example. 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/N , is the minimum fuel cut intake amount, A/N2 is the second fuel cut intake amount, Nc' is the minimum fuel cut rotation speed, and Ns is the high speed range fuel cut rotation speed. Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] Stops the driving of the fuel injection valve when the engine rotational speed is greater than a predetermined value that is greater than the fuel cut minimum rotational speed, and the intake air amount of the engine is less than or equal to a predetermined value that is greater than the fuel cut minimum intake air amount. A fuel injection control device characterized by: