JPH0233433A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To keep the air-fuel ratio constantly in the most adequate state regardless of the fluctuation of fuel pressure by retrieving the fuel pressure correction factor to the fuel injection pulse width memorized by a memory means from the output value of a fuel pressure sensor for detecting the delivery pressure of a fuel pump. CONSTITUTION:In a control means 24, each kind of sensor signals are inputted from a running state parameter detecting means 25, and the basic fuel injection pulse width is calculated from the engine speed and the intake air quantity by means of a calculating means 32. The fuel pressure correction factor is further obtained at a fuel pressure correction factor retrieving means 35 by map retrieval using the signals outputted from a fuel pressure sensor 22 and the output value from an O2 sensor 16. The basic fuel injection pulse width is corrected at a fuel injection pulse width calculating means 36 using the fuel pressure correction factor, the voltage correction, the air-fuel ratio correction factor and the air-fuel ratio feedback correction factor so as to control the running of an injector 11. As a result, the air-fuel ratio can be constantly controlled in the most adequate state regardless of the fluctuation of the fuel pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air-fuel ratio control device for an engine that takes into account a fuel pressure coefficient according to fuel pressure fluctuations of a fuel pump to a fuel injection pulse width.

[Prior art and problems to be solved by the invention] Conventionally, mass flow (L-jetronic) method or
In those that use the speed density (D-Jetronic) method to perform intermittent fuel injection control, the engine speed N detected by a crank angle sensor or the like, and the engine speed N detected by an air flow meter or suction pressure sensor are detected. The basic fuel injection pulse width Tp (Tp=
KXQ/N K...constant) is calculated, and this basic fuel injection pulse width To is calculated using the air-fuel ratio correction coefficient C0FF such as cooling water temperature and intake air temperature, and the air-fuel ratio feedback correction coefficient KFB detected by the 02 sensor etc. The actual fuel injection pulse width Ti is calculated by correcting various correction terms and the voltage correction pulse width (Ts) term (Ti - Tp
KFB+C0EF) +Ts).

On the other hand, in the fuel system, the fuel pumped from the fuel tank by the fuel pump is constantly adjusted to a pressure a predetermined level higher than the internal pressure of the intake pipe by the pressure regulator, and then supplied to the injector.

Therefore, the timing of fuel injection from this injector is determined by the fuel injection pulse width Ti. Regarding this fuel pressure control, for example, Japanese Unexamined Patent Publication No. 1986-13
It is disclosed in Japanese Patent No. 2460.

By the way, the voltage correction pulse width Ts is derived from the relationship between the injector drive power supply voltage and the injector operation delay, and when the injector drive power supply voltage decreases, the operation delay time, that is, after the drive voltage is applied, increases. The difference (T) between the delay time To until the injector opens and the delay time TC from when the drive voltage is turned off until the valve closes.

TC> also becomes long, and on the other hand, when the injector drive power supply voltage is high, the opposite characteristic appears, so the activation delay is interpolated by the fuel pulse width.

However, the fuel injection fll from the injector does not depend only on the substantial valve opening time (pulse width) of the injector, but is also affected by fluctuations in fuel pressure. For example, if the driving voltage of the fuel pump decreases due to a drop in battery voltage, etc., when fishing on a boat, the pressure regulator will keep the fuel pressure constant even if the driving voltage of the fuel pump decreases to some extent, but it will be significantly lower. If the pressure changes, the pressure regulator will not be able to cope with it. Further, if the operating part of the pressure regulator becomes stuck and its operation becomes slow, the fluctuation range of the fuel pressure gradually increases.

When the fuel pressure fluctuates due to the above-mentioned causes, even if the fuel injection pulse width Ti is constant, the fuel injection amount determined thereby fluctuates, resulting in a problem that the air-fuel ratio becomes unstable.

[Objective of the Invention] The present invention has been made in view of the above circumstances, and provides an engine air-fuel ratio control device that can always control the air-fuel ratio to an optimal state without making the air-fuel ratio unstable even when the fuel pressure fluctuates. It is intended to.

[Means and Effects for Solving the Problems] The air-fuel ratio control device for an engine according to the present invention includes a control means that calculates a fuel injection pulse width for an injector based on an output signal of an operating state parameter detection means. A fuel pressure correction coefficient retrieval means is provided for retrieving a fuel pressure correction coefficient that corresponds to the fuel injection pulse width stored in the storage means from an output value of a fuel pressure sensor that detects the discharge pressure of the fuel pump provided in the detection means. It is something that exists.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

The drawings show an embodiment of the present invention, in which Fig. 1 is a block diagram of an air-fuel ratio control device, Fig. 2 is a schematic diagram of an engine control system, Fig. 3 is a conceptual diagram of a fuel pressure correction coefficient map, and Fig. 4 is a schematic diagram of an engine control system. 7 is a flowchart showing a means for searching a fuel pressure correction coefficient.

(Configuration) Reference numeral 1 in the figure is the engine body, and the figure shows a horizontally opposed four-cylinder engine. Further, an intake manifold 3 and an exhaust manifold 4 are connected to an intake boat 2a1 and an exhaust boat 2b formed on the cylinder head 2 of the engine body 1, respectively.

Further, a throttle chamber 6 is communicated with the upstream side of the intake manifold 3 via an air chamber 5, and the upstream side of the throttle chamber 6 is communicated with an air cleaner 8 via an intake pipe 7.

Further, an intake air ff1L sensor (in the figure, a hot wire air flow meter) 9 is installed immediately downstream of the air cleaner 8 in the intake pipe 7, and a throttle valve 6a provided in the throttle chamber 6 is connected to a throttle valve 6a provided in the throttle chamber 6. A sensor 10 is arranged in series, and an injector 11 is arranged immediately upstream of each intake boat 2a that communicates with the combustion chamber 1a of each cylinder of the intake manifold 3.

Furthermore, a cooling water temperature sensor 12 is installed in a cooling water passage (not shown) forming a riser formed in the intake manifold 3.
is coming.

Further, a crank rotor 13 is fixed to the crankshaft 1b of the engine main body 1, and a crank angle sensor 14 is provided on the outer periphery of the crank rotor 13. The crank angle sensor 14 extracts an alternating current voltage generated by a change in magnetic flux when the protrusion 13a formed on the outer periphery of the crank rotor 13 passes the pickup of the crank angle sensor 14, and outputs it to a control means 24, which will be described later.

Further, an 02 sensor 16 is provided facing an exhaust pipe 15 communicating with the exhaust manifold 4. In addition, the code|symbol 16a is a catalytic converter.

Also, to explain the configuration of the fuel system, a fuel pump 19, a fuel filter 20, and a pulsation damper 21 are connected from the fuel tank 17 side to a fuel supply passage 18a that communicates the outlet 17a of the fuel tank 17 with the injector 11. Further, a fuel pressure sensor 22 is provided in order to face the fuel supply passage 18a on the downstream side of the fuel filter 20. Note that each injector 11 is communicated with each other via a delivery passage 18b.

Further, a fuel chamber 23a of a pressure regulator 23 is interposed in a fuel return passage 18c that communicates the injector 11 and the inlet 17b of the fuel tank 17, and a spring chamber 23b of the pressure regulator 23 is connected to the intake manifold 3. communicated with,
The fuel pressure is set constant with respect to the negative pressure inside the intake manifold 3.

On the other hand, reference numeral 24 is a control means, and on the input side of this control means 24, each sensor 9, 10, 12, 14, 16° 22 constituting the operating state parameter detection means 25 and a voltage connected to the battery BV are connected. In addition, the injector 11 is connected to the output side of the control means 24.
is connected.

(I-plane configuration of control means 24) This control means 24 includes an engine rotation speed calculation means 26, an intake air amount calculation means 27, a voltage correction pulse width calculation means 28
, 2 throttle opening calculation means, 3 cooling water temperature calculation means
0, fuel pressure value calculation means 31, basic fuel injection pulse width calculation means 32, air-fuel ratio correction coefficient calculation means 33, air-fuel ratio feedback correction coefficient calculation means 34, fuel pressure correction coefficient search means 3
5. Fuel pressure correction coefficient map M P PFVO1 stored in storage means such as ROM (not shown) Fuel injection pulse width calculation means 36 and injector drive means 37 are comprised.

Engine speed calculation means 26, intake air amount calculation means 27
Now, the engine rotation speed N and the intake air ff1Q are calculated from the output signals of the crank angle sensor 14 and the intake air level sensor 9, respectively.

The voltage correction pulse width calculation means 28 calculates the invalid injection time (
A voltage correction pulse width TS for interpolating the invalid injection time is calculated by reading the pulse width) from a table (not shown).

Throttle opening calculation means 29, cooling water temperature calculation means 30
Now, from the output signals of the throttle sensor 10 and the coolant temperature sensor 12, the throttle distance θ 1 and the coolant temperature Tw are calculated, respectively.

The fuel pressure value calculation means 31 calculates the discharge pressure of the fuel pump 19, that is, the fuel pressure PF, by taking in the output terminal voltage of, for example, a digital voltmeter installed in the fuel pressure sensor 22.

The basic fuel injection pulse width calculation means 32 uses the engine rotation speed N calculated by the engine rotation speed calculation means 26 and the intake air ff1Q calculated by the intake air amount calculation means 27.
Basic fuel injection as a function! )lr! Calculate lTp (
Tp=to-Q/N K...constant).

The air-fuel ratio correction coefficient calculation means 33 calculates an air-fuel ratio correction coefficient KBLRC based on the throttle distance 0TH1 closed by the throttle opening calculation means 29, the cooling water temperature Tw calculated by the cooling water temperature calculation means 3o, etc. .

In the air-fuel ratio feedback correction coefficient calculation means 34, o2
An air-fuel ratio feedback correction coefficient α is calculated based on the output signal VO2 of the sensor 16.

The fuel pressure correction coefficient search means 35 uses the air-fuel ratio feedback value VO2 of the O2 sensor 16 and the fuel pressure value calculation means 3.
The fuel pressure correction coefficient PFVO stored in the fuel pressure correction coefficient map M P PFVO is searched using the fuel pressure value P" calculated in step 1 as a parameter.

As shown in FIG. 3, the fuel pressure correction coefficient map M P
PFVO is composed of a fuel pressure (P') grid and an air-fuel ratio feedback (VO2) grid, and has a fuel pressure upper limit reference value pFrefH1 a fuel pressure lower limit reference value PFrefL,
Each area A surrounded by air-fuel ratio feedback upper limit reference value VO2refl (, air-fuel ratio lower limit reference value V 02r + JL
, B, C, and D are, for example, A>B;A>C>D: Bf-C, and the corrected pulse width of each region is the discharge pressure of the fuel pump 19, i.e. , the fuel pressure applied to the injector 11 is estimated from the fuel pressure PF, and based on the estimated value, it is determined in advance through experiments or the like.

Note that each area A, B, C, and D in the figure is set at 1/16 of each of the four corners of the entire map, and other areas are considered to be within the range of variation errors, so the correction coefficient PFV
O = set to O.

In the fuel injection pulse width calculation means 36, each of the above calculation means 3
Basic fuel pulse width Tp calculated in 2.28.33.34
, voltage correction pulse width Ts, air-fuel ratio correction coefficient K BLIt
C1 air-fuel ratio feedback correction coefficient α and fuel pressure correction coefficient PFV searched by the fuel pressure correction coefficient search means 35
The fuel injection pulse width Ti is calculated based on O.

That is, the fuel injection pulse width Ti is Ti = Tp
Calculate by ×a (KBLRC+PFVO) +Ts.

Then, the fuel injection pulse width T1 calculated by the fuel injection pulse width calculating means 36 is output to the injector 11 via the injector driving means 37.

(Operation) Next, the search procedure performed by the fuel pressure correction coefficient search means 35 will be explained according to the flowchart shown in FIG.

First, in step 5101, the air-fuel ratio feedback value V
After reading O2 and fuel pressure value PF, a map search is executed.

In step 5102, the air-fuel ratio feedback value ■02 is compared with the air-fuel ratio feedback lower limit value VO2r+JL, and if VO2≦VQ2re4L, step 510
If VO2>VO2refL, the process advances to step 5104.

Then, in step 5103, the fuel pressure value PF and the fuel pressure lower limit value PFrerL are compared, and if PF≦pFrefL,
The process advances to step 5105 and specifies the area. Also, p
If F>PFrcfL, the process advances to step 3106.

In step 8106, the fuel pressure value PF is compared with the fuel pressure upper limit value P FrefH. If PF≧p Fre4H, the process advances to step 5107, and region C is specified. In addition, in the case of p F < P FrefH, it is considered to be within the range of variation error, so the fuel pressure correction coefficient PFVO=
Set to 0 (step 3108).

Further, in step 5104, the air-fuel ratio feedback value VO2 and the air-fuel ratio feedback upper limit 1vQ2ref
If VO2≧VO2refH, the process advances to step 5109. Also, VO2<VO2re
In the case of fH, the process proceeds to step 8108, where the fuel pressure correction coefficient PFVO is set to O.

In step 3109, the fuel pressure value PF is compared with the fuel pressure upper limit value P FrefH.

If PF≦pFrefL, the process advances to step 5110 and region B is specified. Also, P F > P Frcf
In the case of L, in step 5111, the fuel pressure value P" is compared with the fuel pressure upper limit value PFrefll, and PF≧p FrefH
If so, the process advances to step 5112 to identify the area.

In addition, if PF<pFrefll, the above step 81
Proceed to step 08 and set the fuel pressure correction coefficient PFVO=O.

It should be noted that the present invention is not limited to the above-described embodiment, and for example, the fuel pressure correction coefficient map M P PFVO may be configured using the intake pipe negative pressure and the air-fuel ratio feedback value as parameters.

[Effects of the Invention] As described above, according to the present invention, the control means for calculating the fuel injection pulse width for the injector based on the output signal of the operating state parameter detecting means is provided in the operating state parameter detecting means. Since fuel pressure correction coefficient retrieval means is provided for retrieving a fuel pressure correction coefficient for the fuel injection pulse width stored in the storage means from the output value of a fuel pressure sensor that detects the discharge pressure of the fuel pump, the fuel pressure does not fluctuate. The air-fuel ratio does not become unstable even when the air-fuel ratio is changed, and the air-fuel ratio can always be controlled to an optimum state.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which Fig. 1 is a block diagram of an air-fuel ratio control device, Fig. 2 is a schematic diagram of an engine control system, Fig. 3 is a conceptual diagram of a fuel pressure correction coefficient map, and Fig. 4 is a schematic diagram of an engine control system. 7 is a flowchart showing a means for searching a fuel pressure correction coefficient. 11... Indicator I, 19... Fuel pump, 22
...Fuel pressure sensor, 24...Control means, 25...Operating state parameter detection means, 35...Fuel pressure correction coefficient search means, M P PFVO...Fuel pressure correction coefficient map,
PFVO...Fuel pressure correction coefficient. Figure 3

Claims (1)

[Scope of Claims] The control means for calculating the fuel injection pulse width for the injector based on the output signal of the operating state parameter detecting means includes a fuel pressure sensor for detecting the discharge pressure of the fuel pump, which is provided in the operating state parameter detecting means. An air-fuel ratio control device for an engine, comprising: a fuel pressure correction coefficient retrieval means for retrieving a fuel pressure correction coefficient for the fuel injection pulse width stored in a storage means from an output value of the fuel injection pulse width.