JPH02119671A - Fuel injection device for engine - Google Patents

Abstract

PURPOSE:To equally supply fuel to all of the cylinders by providing the first injector in an intake passage and also providing, upstream from the first injector, the second injector for injecting fuel with a timing shifted from the injection timing of the first injector. CONSTITUTION:An air cleaner 11, air flow meter 12, throttle valve 13 and surge tank 15 are provided in a common intake passage 9 in order from the upstream side. The second injector 14 is disposed downstream from the throttle valve 13 in such a way that the injection port is located downstream from the throttle valve 13 while being inclined toward the surge tank 15. The surge tank 15 is connected with an independent intake passage 17 intercommunicated with the intake port 2 of each cylinder through an intake manifold 22 and in the independent intake passage 17, the first injector 18 is arranged with the injection port inclined toward the downstream side. The second injector is controlled to perform the fuel injection with a timing shifted from the fuel injection timing of the first injector 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device for an engine with improved acceleration response.

(Prior art) A fuel injection system that is equipped with an air flow meter that detects the intake air amount and an injector (fuel injection valve) that injects fuel into the intake air, and controls the fuel injection amount (air-fuel ratio) according to the intake air amount. BACKGROUND ART Engines have been known in the past, and in such fuel injection engines, an injector is usually arranged facing the intake boat, and fuel is injected toward the intake valve. However, in the above-mentioned conventional fuel injection type engine, due to layout constraints, etc., the length of the intake path between the air flow meter and the throttle valve must be increased to some extent, so the amount of intake air generated as the throttle valve opens and closes. It takes some time for the change to reach the air flow meter, and it also takes some time to calculate the output value of the air flow meter, so there is a response delay in detecting the intake air amount. During acceleration, there is a problem in that the increase in the fuel injection amount is slightly delayed relative to the increase in the intake air amount, and the air-fuel ratio (A/F) of the intake air becomes lean at the beginning of acceleration, deteriorating the acceleration response. Also,
A portion of the fuel injected from the injector adheres to the wall of the intake port, so during sudden acceleration when the amount of fuel injection increases rapidly, the amount of fuel adhering to the wall also increases, and the air-fuel mixture supplied to the combustion chamber is reduced. There were problems such as the fuel ratio becoming leaner, causing hesitation and deterioration of acceleration performance.

Therefore, the injector (
In addition to the main injector, a second injector is installed as an assist injector upstream of the main injector, and during acceleration, fuel is injected from both injectors to temporarily enrich the air-fuel ratio of the mixture, resulting in acceleration. For example, an engine fuel supply system designed for responsiveness was developed in the 1980s.
= Proposed in Publication No. 102467.

By the way, for example, as shown in FIG.
cylinder - 3rd cylinder - 4th cylinder - 2nd cylinder, and the fuel injection timing is synchronized just before the intake stroke of the 1st cylinder and 4th cylinder, so that every revolution of the crankshaft (2 cylinders in 1 cycle).
In an inline four-cylinder engine that performs fuel injection at time points M1, M2, M3, M4, ... This will be done in the latter half of the intake stroke. Therefore, the second injector on the upstream side (
(assist injector) fuel injection timing to the first downstream side.
If the fuel injection timing is made to match the fuel injection timing of the injector (main injector), the intake flow velocity in the second and third cylinders will be low and the intake valve will close soon, even though the assist injector has been installed. Since the fuel adheres to the wall of the intake port and is not sufficiently brought into the cylinder, the air-fuel ratio A/F becomes lean, so the expected acceleration performance improvement effect cannot be achieved and a large amount of No. There were some drawbacks.

(Object of the Invention) In view of the above-mentioned circumstances, an object of the present invention is to provide a fuel injection device for a multi-cylinder engine that improves acceleration response by supplying fuel equally to all cylinders. With the goal.

(Structure of the Invention) The present invention is characterized in that the timing of injecting fuel from the second injector on the upstream side is shifted from the fuel injection timing of the first injector on the downstream side.

(Effects of the Invention) According to the present invention, fuel can be injected from the second injector immediately before the intake stroke of the cylinder where the air-fuel ratio becomes lean, so the effect of providing the second injector can be fully exhibited. This makes it possible to improve acceleration response and reduce noise in the exhaust gas.

(Example) Examples of the present invention will be specifically described below.

As shown in FIG. 1, when the intake valve 1 is opened, the engine E sucks intake air (mixture) into the combustion chamber 3 from the intake port 2, compresses this intake air with the piston 4, and ignites it. A plug (not shown) ignites and burns the combustion gas, and the combustion gas is passed through the exhaust valve 5.
When opened, the air is discharged into an exhaust passage 7 via an exhaust boat 6.

In order to supply intake air to the combustion chamber 3, a common intake passage 9 is provided, and in this common intake passage 9, in order from upstream, there is an air cleaner 11 that removes floating dust in the intake air, and an air cleaner 11 that detects the amount of intake air. An air flow meter 12 and a throttle valve 13 that opens and closes in conjunction with an accelerator pedal (not shown).
In a predetermined light load range, as will be explained in detail later, a second injector (assist injector) injects fuel into the intake air (hereinafter simply referred to as throttle side intake air) supplied to the combustion chamber 3 via the throttle valve 13. 14, and a surge tank 15 for stabilizing the amount of intake air.

For the second injector 14, in order to promote mixing of the fuel and the intake air, it is preferable to use an injector that atomizes the fuel well, such as a swirl type, and
The second injector 14 is arranged at a position slightly upstream of the surge tank 15 and immediately downstream of the throttle valve 13 with its injection port tilted toward the surge tank 15 so that the injected fuel is uniformly diffused into the surge tank 15. It has become.

In the surge tank 15, each cylinder (in FIG. 1, the first
An independent intake passage 17 that communicates with the intake port 2 of the cylinder (only cylinders shown) is connected by an intake manifold 22, and a first injector (main injector) 18 has an injection port in this independent intake passage 17 immediately upstream of the intake port 2. It is placed with the slanted toward the downstream side. This first injector 18 is a normal injector used in general fuel injection type engines.

A bypass intake passage 21 is provided that communicates the common intake passage 9 slightly upstream of the throttle valve 13 with the independent intake passage 17 immediately upstream of the first injector 18 . The opening opens toward the injection port of the first injector 18 so as to promote atomization of the fuel injected from the first injector 18. The bypass intake passage 21 is provided with an electromagnetic flow control valve lO that opens and closes it. The flow rate of intake air supplied to the bypass intake air (hereinafter simply referred to as bypass intake air) is controlled. The flow rate control valve 10 controls the bypass intake air amount in order to maintain the idle rotation speed at a predetermined value during idle, while
When fuel is injected from the second injector 14 during non-idling, the bypass intake air amount is controlled to maintain a constant ratio of the bypass intake air amount to the total intake air amount.

The control unit 23 is a general control device for the engine E configured with a microcomputer, and is a second
As shown in the functional block diagram in the figure, the intake IIQ, engine speed N, idle switch signal, and crank angle sensor are controlled. As the In information, various calculations and determinations are performed to control the first injector 18, the second injector 14, and the flow rate control valve 10.

Note that the above zone determination includes determining whether the area is one of an area where fuel is injected only from the first injector, an area where fuel is injected from both the first and second injectors, and a determination of the fuel cut area. including. FIG. 3 is a diagram showing the characteristics of the operating region of the second injector 14 and the fuel cut region with respect to the engine load and engine speed N, where region (■) is the region where only the main injector 18 is operated, and region (2) is the region where only the main injector 18 is operated. The assist injection region (region) in which both the first and second injectors 18 and 14 are operated is a fuel cut region in which the operation of the first injector 18 is stopped, and in this region (i), the throttle valve 10 is in a fully closed state. Although the idle switch operates, the duty ratio of the flow control valve IO is increased, the amount of intake air passing through the bypass intake passage 21 increases, and a small amount of fuel is injected from the second injector 14.

Next, the fuel injection control of the first injector 18 and the second injector 14 and the duty control of the flow rate control valve 10 will be explained according to the functional block diagram of FIG. 2 and the flowchart shown in FIG. 4.

When control is started, in step S1, engine rotational speed N, intake air amount Q, idle switch signal, crank angle, and other control information are read.

In step S2, the basic injection pulse width TP is calculated based on the intake air amount Q and the engine speed N. Next, in step S3, it is determined whether the operating state of the engine E is in the fuel cut region (region ■) in FIG. ), in the next step S4, the duty ratio DT for operating the flow rate control valve 10 is calculated as DT=DT.

In step S5, it is determined whether the operating state of the engine E is in region (2) or (2) in FIG. Then, when it is determined that the area is in the assist injection area of area (■), the injection pulse width TA of the assist injector 14 is T.
A = T A + is calculated, and when it is determined that it is in the region ■, TA is set to 0 in step S7.Next, in step s8, various corrections are made to correct the basic injection pulse width TP of the first injector 18. Correction coefficients are calculated, and the final injection pulse width T corrected by these correction coefficients
M is calculated in step S9, and in the next step SIO,
The flow control valve IO is driven with a duty ratio DT.

On the other hand, when it is determined in step S3 that the fuel cut region is reached, the process proceeds to step Sll, and the duty ratio DT of the flow rate control valve 10 is set as DT=DT, (DT,>D
T, ). Then, in step S12, the second
The injection pulse width TA of the injector 14 is T A = T
It is calculated as A t (T A z > T A + ). This injection pulse width TA is the surge tank 1
The air-fuel ratio A/F within 5 is the stoichiometric air-fuel ratio (A/F = 14.7)
A/F=13 is set to a certain value (for example, A/F=13). After the injection pulse width TM of the first injector 18 is set to O in the next step 513, step S
Proceeding to IO, the flow control valve 10 sets the above-mentioned duty ratio DT.
, and is driven with a duty ratio DT larger than .

In the next step S14, it is determined whether or not it is the injection timing for the second injector 14. This second injector 1
The injection timings of No. 4 are shown in Fig. 7 as A1, A2, A3, A4, -
As shown by -------, the fuel injection timings M1, M2, M3, M4, etc. of the first injector 18 are at different positions, and the combustion starts from the second injector 14. Considering the fuel arrival delay based on the difference between the distance to the chamber 3 and the distance from the first injector 18 to the combustion chamber,
Injection timings A1, A2, A3, A of the second injection engine 14
4. is the injection timing ML M2 of the first injector 18;
It is set at a position a predetermined angle ahead of the midpoint between M3, M4, and so on. Then, in step S14, the injection timing Ah of the second injector 14 is determined as A2, A3, A4, -
- If it is determined that m-, the second injector 14 is driven with the injection pulse width TA in step S15 (TA=O1 in area ①; T in area ②).
A = T A +, in area ■ T A = T A 2
).

In the next step 316, it is determined whether or not it is injection timing for the first injector 18. And the injection timing AI of the first injector 18, A2, A3, A4, etc.
If it is determined that the first injector 18 is driven with the injection pulse width TM in step S16 (
In the SN region■, TM=O).

Figure 5 shows the fuel cut HJlili (nJi area)
) when returning to the assist injector area (area ■), the fuel cut flag, the amount of intake air passing through the first III path 21, and the injection pulse width TA of the second injector 14.
and a timing chart showing a state of change in the injection pulse width TM of the first injector 18.

Further, FIG. 6 shows the transition from the area where only the first injector 18 is operated (area
Flag indicating area ■ when moving to J area ■), first
The amount of intake air passing through the passage 21 and the injection pulse width TA, TM
3 is a timing chart showing a state of change.

The above is an explanation of the configuration and operation of the embodiment of the present invention. As is clear from FIG. 7, in this embodiment, the injection timings AI, A2, A3,
A4, ------- is set at a position that is a predetermined angle ahead of the midpoint of the injection timings M1, M2, M3, M4, . . . of the first injector 18, and the second injector 1
Since the fuel injected from No. 4 reaches the intake boats of the second and third cylinders immediately before the intake strokes of the second and third cylinders, the effect of providing the second injector is fully demonstrated. This makes it possible to improve acceleration response and reduce NOx in exhaust gas.

Further, in this embodiment, in region (3) of FIG. 3, which is the fuel cut region, the throttle valve 13 is fully closed and the operation of the first injector 18 is stopped, and at the same time, the flow control valve 10 of the bypass intake passage 21 is closed. The duty ratio is increased to increase the amount of intake air passing through the bypass intake passage 21, and fuel is supplied from the second injector 14 so that the air-fuel ratio A/F in the surge tank 15 remains constant and richer than usual. Therefore, if the throttle valve 13 is suddenly opened from this state and the transition to region I occurs, the rich mixture in the surge tank 15 may occur even though the intake boat 2 is drier than during normal acceleration. By compensating for this, it is possible to prevent changes in combustion due to lean air-fuel ratio A/F and further improve acceleration.

The above-mentioned embodiment is a case in which the present invention is applied to an in-line four-cylinder engine configured to inject fuel from the first injector 18 every revolution of the crankshaft. The present invention can also be applied to a multi-cylinder engine configured to inject fuel from the first injector 18 to each cylinder immediately before the injection.

[Brief explanation of drawings]

Fig. 1 is a system configuration diagram of an engine equipped with a fuel supply device according to the present invention, Fig. 2 is a functional block diagram, and Fig. 3 is a diagram showing the operating range of the first and second injectors with respect to engine load and engine speed. , Fig. 4 is a flowchart showing the control routine for the first and second injectors and the flow rate control valve, Figs. 5 and 6 are timing charts showing changes in the injection pulse width of each injector, and Fig. 7 is a flowchart showing the control routine for the first and second injectors and the flow rate control valve. 5 is a timing chart showing the relationship between each stroke and the injection timing of each injector. E--Engine 2.-Intake port 3-Combustion chamber 10-Flow control valve 12-Air flow meter throttle valve 14-Second injector surge tank
18-First injector bypass intake passage control unit,

Claims (1)

[Claims] 1. A first injector that injects fuel at a predetermined timing to supply fuel to each cylinder, and an injector that is disposed upstream of the intake of the first injector and that injects fuel at a timing shifted from the fuel injection timing of the first injector. A fuel injection device for an engine, comprising: a second injector that injects fuel.