JPH025725A - Engine fuel injection device - Google Patents

Abstract

PURPOSE:To prevent the intake charge sucked into a combustion chamber from becoming excessively rich or lean, by injecting fuel only from a main injector upon start of an engine at least in a high intake-air temperature condition. CONSTITUTION:An engine CE incorporates a main injector 18 disposed in an independent intake-air passage 17 in the vicinity of an intake-air port 2, and an assist injector 14 disposed in a common intake air passage 9 in the vicinity of a surge tank 15 upstream of the main injector 18. In a predetermined operating range, a lean mixture is created in the vicinity of the intake-air port 2 while a rich mixture is created in the surge tank 15. Further, a control unit 24 controls the injectors 14, 18 so that fuel is injected only from the main injector 18 during start of the engine in at least a high intake-air temperature condition. With this arrangement, the rich mixture in the surge tank 15 is prevented from further becoming rich, thereby it is possible to enhance the startability of the engine CE.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a fuel injection device for an engine, and is intended to improve acceleration response from a light load range. A fuel injection device for an engine, comprising a main injector for supplying a lean mixture near an intake port, and an assist injector for supplying a rich mixture to a surge tank upstream of the main injector. It is related to.

[Prior art] A fuel system that is equipped with an air flow meter that detects the amount of intake air and an injector (fuel injection valve) that injects fuel into the intake air, and controls fuel injection collapse (air-fuel ratio) according to the amount of intake air. Injection type engines have been known for a long time (for example, see Japanese Patent Laid-Open No. 59-29733), and in such fuel injection type engines, the injector is usually arranged facing the intake port or the combustion chamber. However, in the conventional fuel injection type ennon, the length of the intake path between the air flow meter and the throttle valve must be increased to some extent due to layout constraints, etc. It takes some time for the change to reach the airflow meter, and it also takes some time to calculate the output value of the airflow meter, so there is a delay in response in detecting the amount of intake air. Therefore, when the engine accelerates, the increase in fuel injection amount is slightly delayed compared to the increase in intake air amount, and the intake air-fuel ratio (A/F) changes at the beginning of acceleration.
There is a problem in that the acceleration response becomes leaner and the acceleration response deteriorates, and this deterioration of the acceleration response becomes particularly noticeable under light loads.

In order to prevent this, a fuel injection device has been proposed in which a means for rapidly detecting acceleration is provided separately, and the fuel injection amount is increased when the engine accelerates. However, even if the amount of fuel is suddenly increased during acceleration, not all of the fuel will be vaporized, so this conventional system has not been able to sufficiently improve acceleration response.

Therefore, while a main injector that injects fuel into the intake port is provided, an assist injector is provided in the intake passage upstream of the main injector, preferably immediately upstream of the surge tank, and an assist injector is provided in the intake passage upstream of the throttle valve and in the vicinity of the main injector. A bypass intake passage is provided to communicate with the main injector, and during light loads, the intake air supplied through the bypass intake passage (hereinafter simply referred to as bypass intake air) and the fuel injected from the main injector form a slightly lean mixture. , a slightly rich mixture of intake air (hereinafter simply referred to as throttle side intake air) supplied through the intake passage downstream of the branch from the bypass intake passage according to the opening of the throttle valve and fuel injected from the unstuck injector. A fuel injection device for an engine has been proposed that generates air and supplies a mixture of the above-mentioned rich air-fuel mixture and lean air-fuel mixture to the combustion chamber at a predetermined air-fuel ratio. . In this case, when the throttle valve is suddenly opened during acceleration from a light load range, the intake air in the surge tank (throttle side intake) is -
However, as mentioned above, the intake air on the throttle side is already a slightly rich mixture, so a slightly rich mixture is supplied to the combustion chamber without response delay, and the engine output increases. It is now possible to sufficiently increase the acceleration performance.

[Problem to be solved by the invention] However, in the above-mentioned conventional engine in which an unstopped injector is provided immediately upstream of the surge tank, a small amount of liquid fuel always adheres to the inner wall of the surge tank, but it is difficult to stop the engine. Immediately after, the adhering fuel is vaporized by the residual heat of the engine, while the flow of intake air in the surge tank is stopped, so a rich air-fuel mixture is formed in the surge tank. When the ENON is started in such a case, fuel is further injected from the anost injector into the rich air-fuel mixture, so a very rich air-fuel mixture is sucked into the combustion chamber, which improves engine startability. The problem was that it worsened.

Also, if you start the engine when the intake temperature is low,
This increases the proportion of fuel injected from the unstuck injector that adheres to the inner wall surface of the surge tank, resulting in a lean air-fuel mixture supplied to the combustion chamber, which poses a problem in that the startability of the ennon deteriorates.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to improve acceleration response from a light load range using a simple control method in an engine provided with a main injector and an assist injector. To provide a fuel injection device for an engine, which can improve startability by effectively preventing intake air taken into a combustion chamber from becoming excessively lynchy or lean when starting the engine. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a main injector arranged in an intake passage near an intake port, and a main injector arranged in an intake passage near a surge tank upstream from the main injector. In an engine that is equipped with an assist injector and that generates a lean mixture near the intake port and a rich mixture in the surge tank in a predetermined operating range, at least the engine from a high intake temperature state There is provided a fuel injection device for Ennon, characterized in that it is provided with a fuel injection control means for controlling the fuel injection device so that fuel is injected only from the main injector at the time of startup.

[Operations and Effects of the Invention] According to the present invention, when starting the engine from a high intake temperature state,
In other words, if the engine is started immediately after the engine has stopped and a rich mixture is generated in the surge tank, fuel injection from the assist injector is stopped, and the rich mixture in the surge tank becomes even richer. Since this is prevented, the startability of the engine can be improved.

In addition, when starting the engine, if the intake temperature is lower than a predetermined value, the fuel injection from the assist injector is stopped and all fuel is injected only from the main injector. Since it is possible to prevent the fuel from adhering to the combustion chamber, it is possible to effectively prevent the air-fuel mixture supplied to the combustion chamber from becoming lean, thereby improving the startability of the engine.

[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 CE sucks intake air (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) is used to ignite and burn the combustion gas, and when the exhaust valve 5 is opened, the combustion gas is discharged into the exhaust passage 7 through the exhaust port 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. Air flow meter! 2, 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, an injector 14 injects fuel into the intake air supplied to the combustion chamber 3 via the throttle valve 13 (hereinafter simply referred to as throttle side intake air), and an intake air amount. A surge tank 15 is provided for stabilizing. In order to promote mixing of the fuel and intake air, it is preferable to use the unstuck injector 14, for example, a swirl type injector that can effectively atomize the fuel. The assist injector 14 has an injection port located in the surge tank 15 at a position slightly upstream of the surge tank 15 and immediately downstream of the throttle valve 13.
It is arranged so as to be inclined toward the surge tank 15 side, so that the injected fuel is uniformly diffused toward the surge tank 15 side.

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, and a main injector 18 is disposed in this independent intake passage 17 immediately upstream of the intake port 2 with its injection port tilted toward the downstream side. . This main injector 18 is a normal injector used in general fuel injection type engines.

A bypass intake passage 21 is provided which communicates the common intake passage 9 slightly upstream of the throttle valve I3 and the independent intake passage I7 immediately upstream of the main injector 18.
This bypass intake passage 21 is an independent intake passage! The opening to the main injector 7 opens toward the injection port of the main injector +8 so as to promote atomization of the fuel injected from the main injector 18. The bypass intake passage 21 includes
An idle speed control valve 22 that opens and closes this is provided,
The opening degree of the idle speed control valve 22 is controlled in response to a signal from the control unit 23, and the intake air (hereinafter referred to as
It is designed to control the flow rate of air (simply referred to as bypass intake air). The idle speed control valve 22 controls the bypass intake air amount in order to maintain the idle speed at a predetermined value during idle, while when fuel is injected from the idle 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 comprehensive control device for the engine CE configured with a microcomputer, including the fuel injection control means described in the claims of the present application, and controls intake air ff1Q, engine rotation speed N1, intake temperature ta, and throttle opening. Predetermined control is performed using the degree TV θ, starter switch signal, etc. as control information, but in the following, only the fuel injection 1 control of the main injector I8 and the assist injector 14 related to the present application will be explained as shown in FIG. ), The control method will be explained according to the flowchart shown in (b).

When the control is started, in step Sl, the engine speed N, intake air ff1Q, intake air temperature ta, and throttle opening TVθ are determined.
, starter switch signals, and other control information are read.

Next, step S2. In S3, it is determined whether the engine CE is being started.

In step S2, it is compared whether the starter switch is turned on or not. If the starter switch is turned on (YES), the engine GE is cranking, so the control is performed at the time of starting in steps s4 to S6. Proceed to control routine.

As a result of the comparison in step S2, if the starter switch is not turned on (No), then in step S3 it is compared whether the engine speed N is 40 Orpm or more. Engine speed N even after cranking
When the engine CE has not reached the idle rotation speed (4QOrpm), the engine CE is still being started, so a start-up control routine is executed. As a result of comparison, N<40Orp
If m (NO), the engine speed N has not yet risen to the idle speed, and therefore the engine is being started, so the control proceeds to the start control routine of steps s4 to s6.

In step S4, it is compared whether the intake air temperature ta is 80° C. or higher. If the intake air temperature ta is 80 degrees Celsius or higher when the engine is started, the engine CE may not have had much time since the previous stop, and the residual heat of the engine CE may cause the fuel to adhere to the inner wall surface of the surge tank 15. is vaporized and a rich air-fuel mixture is formed in the surge tank 15, so fuel injection from the assist injector 14 is stopped to prevent the air-fuel mixture in the surge tank +5 from becoming excessively rich. . As a result of the comparison, ta<
If the temperature is 80° C. (No), it is considered that the air-fuel mixture in the surge tank +5 is not excessively rich, so the control proceeds to step S5 and normal startup control is performed.

In step S5, the injection pulse width Ta of the assist injector 14 (hereinafter referred to as assist injector pulse width Ta) and the injection pulse width Tl11 of the main injector I8 (hereinafter referred to as main injector pulse width Tm) are calculated using the following formula. be done.

Ta=K ・Ts Tm=(1-K)・Ts In the above equation, Ts is the total fuel injection pulse width at the time of engine startup, and it is not changed by intake air ff1Q, engine speed N, etc., and is kept at a predetermined constant value. Fixed.

In addition, K is the assist injector 14 in the total fuel injection amount.
This is a constant that indicates the ratio of the fuel injection amount from . In this embodiment, although detailed explanation is omitted, the idle speed control valve 2
2, the bypass intake air amount is controlled to be a constant ratio with respect to the total intake air filQ, so the ratio between the throttle side intake air amount and the bypass intake air amount is kept constant, and therefore, the unstuck injector 14
The ratio between the fuel injection amount and the main injector 18 only needs to be maintained at a constant value K, and there is no need to change it depending on the load. Therefore, the control unit is greatly simplified. After this, control proceeds to step SI5.

On the other hand, as a result of the comparison in step S4, if ta≧80°C (YES), the control proceeds to step S6, and fuel injection from the assist injector 14 is stopped (Ta
=0), all fuel is injected from the main injector 18. At this time, the supply of intake air on the throttle side is stopped, and intake air is supplied only from the bypass intake passage 22 (Tn+=Ts').

Note that since the fuel in the surge tank +5 slightly flows into the combustion chamber 3, the total fuel injection pulse width in this case is Ts' (constant value), which is slightly smaller than Ts explained in step S5.
is set to . In this way, the air-fuel mixture is prevented from becoming excessively rich, and the hot startability of the engine CE is improved. In this case, the main injector 18
The characteristics of the fuel injection amount of the assist injector 14 with respect to time are as shown by the polygonal lines G- and Gs in FIG. 5, respectively, and engine starting is completed at time t. After this, control proceeds to step Sl'5.

By the way, as a result of the comparison in step S3, N≧lI Q
If Orpll (YES), the engine CE has already reached the idle speed and starting of the engine CE has been completed, so the control proceeds to the normal control routine of steps S7 to S14.

In step S7, the basic injection pulse width Tp is calculated using the following equation.
is calculated.

Tp = -Q/N In the above equation, k is the total fuel injection amount required to set the air-fuel ratio of the mixture in the combustion chamber 3 to the stoichiometric air-fuel ratio (A/P = 14.7). This is a coefficient for calculating the corresponding injection pulse width, and is calculated by the method of Tadori.

Step S8. In S9, it is determined whether the operating state of the ENON GE falls within a region where fuel injection should be performed from the assist injector 14 (hereinafter referred to as an assist injector region).

In this embodiment, N≦N as shown in area I in FIG.
1 and in a light load range where Tp≦Tp+, fuel is injected from two injectors, the main injector 18 and the assist injector 14, in order to improve acceleration response.

In this case, the bypass intake air and the fuel injected from the main injector 18 generate a slightly lean mixture, while the throttle side intake air and the fuel injected from the assist injector 14 generate a slightly rich mixture (for example, A /
F=13) is generated, and a predetermined amount of this slightly rich mixture is retained in the surge tank 15. Then, when the engine CE is in such a state and the throttle valve I3 is operated in the opening direction and acceleration is started,
The slightly rich air-fuel mixture in the surge tank 15 is sucked into the combustion chamber 3 all at once. Therefore, the intake air taken into the combustion chamber 3 after the start of acceleration is prevented from becoming lean, and acceleration responsiveness is improved. In this case, for example, when the throttle valve 13 is operated in the opening direction as shown by the line G1 in FIG. 4, the response delay time becomes dl as shown by the curve G according to this embodiment, and the curve The response delay time d is significantly shorter than the response delay time d of a fuel-injected engine without an assist injector as shown in , and therefore the acceleration response is significantly improved.

In step S8, a comparison is made to see if the engine speed N exceeds a predetermined value N1, and in step S9, a comparison is made to see if the basic injection pulse width Tp exceeds a predetermined value Tp+. As a result of these comparisons, N≦N, (No
), and if Qp≦Qp+(NO), then engine C
Since the operating state of E is in the light load region as shown by region I in FIG. 3, the control proceeds to step SIO in order to inject fuel from both the main injector 18 and the idle injector 14.

In step SIO, the unstuck injector pulse width Ta is calculated using the following equation.

Ta=to-Tp In the above equation, K is the assist injector! This is a constant indicating the ratio of the fuel injection amount from No. 4 to the total fuel injection amount, and is the same as K described in step S5. As mentioned above, flow 1 control is performed such that the bypass intake air amount is a constant ratio to the total intake flow ff1Q, so the ratio between the throttle side intake air amount and the bypass intake air amount is constant, and therefore the assist The ratio of the fuel injection amounts of the injector I4 and the main injector 18 only needs to be maintained at a constant value K.

In step S11, the main injector pulse width Tm is calculated using the following equation.

Tm=(+-K)·'rp In the above equation, K is the same constant as explained in step SIO. In addition, in order to avoid affecting steady-state performance,
It is preferable to minimize the share of assist injector I4.

In step SI2, the main injector pulse width Tm is corrected using the following equation.

Tm=Tm-C+Tv In the above equation, Tv is a correction value for the battery voltage, and C is a correction coefficient for the intake air temperature ta, etc., and these corrections are performed in the usual manner.

After this, control proceeds to step S15.

On the other hand, as a result of the comparison in step S8 and step S9, N
>Nl (step S8 is YES) or Tp
>Tp+ (YES in step S9), the operating state of the engine CE is in the high rotation range or high load range as shown by region ■ in FIG. 4, and the acceleration response is hardly deteriorated. In order to stop the fuel injection of the assist injector I4 and inject all the fuel using only the main injector I8, control proceeds to step SI3.

In step 913, the assist injector pulse width Ta is set to 0 in order to stop fuel injection from the assist injector 14.

In step SI4, the main injector pulse width Tm is calculated using the following equation.

Tm=Tm-C+Tv In the above equation, Tv and C are a correction value for battery voltage and a correction coefficient for intake air temperature, etc., respectively, and are the same as those explained in step S12.

After this, control proceeds to step S15.

In step SI5, the main injector pulse width Tm
and assist injector pulse width Ta are output, and fuel injection is performed at a predetermined timing in synchronization with the rotation of the crankshaft.

In step S16, it is compared whether the ignition switch is turned off. As a result of the comparison, if the ignition switch is not turned off (NO), the engine CE
Since the engine continues to operate, the control returns to step S1 and continues.

On the other hand, as a result of the comparison in step SI6, if the ignition switch is turned off, the operation of the engine CE has been stopped, and the control proceeds to the control end routine of steps S17 and S18.

In step S17, the ignition is turned on for a predetermined period of time.
will continue. When the ignition switch is turned off, fuel injection from the assist injector 4 and the main injector 18 has already been stopped, but even after the fuel injection is stopped, the ignition is continued for a predetermined time to rotate the engine CE and inject the fuel into the surge tank 15. The air-fuel mixture inside the surge tank 15 is scavenged, and the fuel adhering to the inner wall surface of the surge tank 15 is removed. Thereby, when starting the engine CE next time, even if the engine CE is hot, enrichment of the intake air at the time of starting the engine can be suppressed.

Next, in step SI8, the ignition is stopped and the control ends.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an Ennon equipped with a fuel injection device according to the present invention. FIGS. 2(a) and 2(b) are flowcharts showing a method for controlling the main injector and the assist injector, respectively, by the control unit. FIG. 3 is a diagram showing the characteristics of the assist injector operating range with respect to engine load and engine speed. FIG. 4 is a diagram showing acceleration response characteristics from a light load range of an engine equipped with an assist injector and an Ennon without an assist injector. FIG. 5 is a diagram showing the characteristics of the fuel injection amount of the main injector and the assist injector with respect to time at the time of starting a hot engine. CE...Engine, 2...Intake port, 3...Combustion chamber, 9...Common intake passage, 12...Air flow meter, 13...Throttle valve, 14...Anst injector, 15... ...Surge tank, 17...Independent intake passage, 18...Main injector, 2! ... Bypass intake passage, 22 ... Idle rotation speed control valve, 23
··control unit.

Claims (1)

[Claims] (1) The main injector is arranged in the intake passage near the intake port, and the assist injector is arranged in the intake passage near the surge tank on the upstream side of the main injector. In an engine designed to generate a lean mixture as well as a rich mixture in the surge tank, the fuel injection device is designed to inject fuel only from the main injector, at least when starting the engine from a high intake temperature state. 1. A fuel injection device for an engine, comprising a fuel injection control means for controlling.