JPH04109042A - Electronically controlled fuel injection system for two-stroke internal combustion engines - Google Patents

Abstract

PURPOSE:To attempt early recovery of misfire condition by setting fuel injection quantities applicable to ignition and misfire respectively, and selecting the fuel injection quantity applicable to misfire or the fuel injection quantity applicable to the ignition according to the existence of generation of the misfire detected individually at each cylinder so as to make driving control of a fuel injection valve. CONSTITUTION:An engine rotational speed is detected by an engine rotational speed detection means A in an electronic control fuel injection device during the operation of a two-cycle internal combustion engine, and an opening area of an engine intake system variably controlled by an opening area detection means B is detected. A fuel injection quantity applicable to ignition is set by a fuel injection quantity setting means C based on the engine rotational speed and the opening area, and the fuel injection quantity applicable to misfire is set by a fuel injection quantity setting means D applicable to misfire similary misfire based on the rotational speed of engine and the opening area. Either one of the above mentioned fuel supply quantity applicable to ignition or the fuel supply quantity applicable to misfire individually at each cylinder is selected by a fuel supply control means E based on the result of a misfire detection means F, so as to make driving control of a fuel injection means G for each cylinder based on the result of selection.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an electronically controlled fuel injection device for a two-stroke internal combustion engine. The present invention relates to fuel control technology in the event of a misfire in a device configured to set a fuel injection amount.

<Prior art> As an electronically controlled fuel injection system for an internal combustion engine, a fuel injection amount is set from the opening area of the engine intake system represented by the throttle valve opening and the engine rotational speed, and the fuel injection amount is set based on the fuel injection amount. There has been a conventional device configured to drive and control an injection valve (see Japanese Patent Laid-Open No. 63-29039, etc.).

<Problems to be Solved by the Invention> By the way, when the engine is running at deceleration, the air-fuel ratio may become rich due to fuel adhering to the walls or delays in fuel control, resulting in a misfire, or misfires may occur between cylinders due to variations in the fuel injection system. Due to variations in the air-fuel ratio, the air-fuel ratio of a particular cylinder may become richer, causing a misfire in that cylinder.

Conventionally, even when such a misfire occurs, fuel continues to be injected as usual, so the ignition plug becomes wet with fuel, making it difficult to ignite and burn it again.

In particular, in a two-stroke internal combustion engine, a misfire makes it impossible to perform scavenging properly, resulting in a sharp decrease in the amount of intake air.However, as mentioned above, the amount of fuel injection is set and controlled based on the opening area of the intake system and the engine speed. Even if the actual amount of intake air is drastically reduced due to a misfire as described above, if the conditions of the opening area and rotational speed do not change, the same fuel as in normal combustion (good scavenging due to combustion) will be produced. Since the amount of fuel (fuel commensurate with the amount of air obtained by the engine) is injected, if a misfire occurs, an overrich mixture is sucked in and there is a high probability that the ignition plug will become wet with fuel and become unable to ignite. .

The present invention has been made in view of the above-mentioned problems, and is intended to suppress wetting of the ignition plug when a misfire occurs in a two-stroke internal combustion engine in which the fuel injection amount is set based on the opening area of the intake system and the engine rotation speed. An object of the present invention is to provide an electronically controlled fuel injection device that can quickly recover from a misfire condition.

<Means for Solving the Problems> Therefore, an electronically controlled fuel injection device for a two-stroke internal combustion engine according to the present invention is configured as shown in FIG.

In FIG. 1, the engine rotational speed detection means detects the engine rotational speed, and the opening area detection means detects the opening area of the engine intake system which is variably controlled.

The ignition fuel injection amount setting means sets the ignition fuel injection amount based on the engine rotational speed and the opening area detected by each of the detection means, and the misfire fuel injection amount setting means Similarly, the misfire fuel injection amount is set based on the rotational speed and the opening area.

On the other hand, the misfire detection means detects whether a misfire has occurred in each cylinder of the internal combustion engine.

The fuel supply control means selects either the ignition fuel supply amount or the misfire fuel supply amount for each cylinder based on the result of the misfire detection means, and sets the fuel supply amount for each cylinder based on the selection result. drive control of each fuel supply means.

<Operation> According to this configuration, the fuel injection amounts for ignition and misfire are set separately based on the engine rotational speed and the opening area of the engine intake system, and the amount of fuel injection for ignition and misfire is determined based on the presence or absence of misfire detected for each cylinder. Accordingly, the misfire fuel injection amount is selected for the misfire cylinder, and the ignition fuel injection amount is selected for the non-misfire cylinder, and the fuel injection amount is set for each cylinder based on the selection result for each cylinder. Since the fuel injection valve is controlled, fuel can be injected into the misfiring cylinder in an amount commensurate with the decrease in the amount of intake air due to the misfire. It is possible to recover from a misfire state by injecting fuel commensurate with the true amount of air while suppressing the misfire.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, an internal combustion engine 1 is a two-stroke gasoline engine of a crank chamber compression type in which air-fuel mixture compressed in a crank chamber 2 flows into a cylinder 3 for scavenging.

Here, the wall surface of the cylinder 3 includes an intake hole 4°, a scavenging hole 5. An exhaust hole 6 is provided, and the piston 7 is
Due to the low pressure generated at the bottom of the cylinder, the air-fuel mixture is sucked into the crank chamber 2 through the intake hole 4, and when the piston 7 passes the exhaust hole 6 at the end of the working stroke, the combustion gas in the cylinder 3 flows through the exhaust hole 6. When the piston 7 is further lowered, the scavenging hole 5 and the crank chamber 2 communicate with each other, and the air-fuel mixture compressed in the crank chamber 2 flows into the cylinder 3 to scavenge the exhaust gas.

A throttle valve 9 is provided at a gathering portion of the intake manifold 8 that communicates with the intake hole 4 to control the intake air flow rate by variably controlling the opening area of the intake manifold 8. Further, in the branch section that branches and extends for each cylinder on the downstream side of the throttle valve 9, an electromagnetic fuel injection valve 10 is installed for each cylinder (two cylinders #l and #2 in this embodiment). An air-fuel mixture is formed by the fuel injected from the fuel injection valve 10 and flows into the crank chamber 2 from the intake hole 4 .

The fuel injection valve IO provided for each cylinder opens in response to a valve opening drive signal sent from a control unit 11 containing a microcomputer, and injects and supplies fuel adjusted to a predetermined pressure. The fuel injection amount can be controlled via the opening time of the valve IO.

The control unit 11 includes a rotation sensor 12 as an engine rotation speed detection means built in a distributor (not shown). A throttle sensor 13 is attached to the throttle valve 9 and serves as an opening area detection means for detecting the opening degree α of the throttle valve 9 using a potentiometer. Each branch of the exhaust manifold 14 is provided with an exhaust temperature T#1. Detection signals from exhaust temperature sensors 15 and the like serving as misfire detection means for detecting T#2 are respectively input.

In FIG. 2, reference numeral 16 indicates a spark plug provided for each cylinder.

Here, the state of fuel injection control by the control unit 11 will be explained according to the program shown in the flowchart of FIG.

In this embodiment, the fuel injection amount setting means for ignition,
The functions of the misfire fuel injection amount setting means and the fuel injection control means are provided in the control unit 11 in the form of software, as shown in the flowchart of FIG. 3 above.

In the flowchart in Figure 3, first, step 1
(In the figure, it is referred to as SL. The same applies hereinafter.) The opening degree α of the throttle valve 9 detected by the throttle sensor 13 (the opening area of the engine intake system that is variably controlled) and the engine speed detected by the rotation sensor 12 are Input the rotation speed N.

In the next step 2, it is determined whether the engine l is in a starting state or has just been started. If it is determined that the engine is in a starting state or just after starting, the operating state is unstable and a misfire diagnosis based on exhaust temperature, which will be described later, cannot be performed with high accuracy. Executes fuel injection control.

In step 13, the throttle valve opening α input in step 1 is selected from a map in which the basic fuel injection amount Tp is stored in advance for each operating region divided into a plurality of regions based on the throttle valve opening α and the engine rotational speed N. The basic fuel injection amount Tp corresponding to the engine rotational speed N is searched and determined, and this is set as the basic fuel injection amount Tp common to the #1 cylinder and the #2 cylinder.

Here, the basic fuel injection amount Tp retrieved from the map in step 13 is set as a fuel amount commensurate with the cylinder intake air amount in a state of normal combustion without misfire. The final fuel injection amount Ti is set by applying various corrections to the amount Tp according to operating conditions such as engine cooling water temperature, and the fuel injection amount Ti
An opening drive pulse signal having a pulse width corresponding to 1 is output to each fuel injection valve IO at a predetermined timing to cause fuel injection to be performed.

On the other hand, if it is determined in step 2 that the engine is not starting or immediately after starting, the process proceeds to step 3, where it is determined whether fuel cut during deceleration is being performed or immediately after such fuel cut.

When the fuel is cut during deceleration or immediately after the fuel cut, misfire detection based on the exhaust temperature cannot be performed with high precision as in the case of starting, so in this case as well, the process proceeds to step 13 to execute normal fuel injection control.

Then, the process proceeds to step 4 only when the engine is not starting, immediately after starting, during fuel cut, or immediately after fuel cut.

In step 4, the exhaust temperature of the #l cylinder detected by the exhaust temperature sensor 15 provided for the #1 cylinder is set to T#l, and in the next step 5, the exhaust temperature sensor 15 provided for the #2 cylinder is set to T#l. The exhaust temperature of #2 cylinder detected in 15 is T#
Set to 2.

In step 6, the basic fuel injection amount T, which indicates the engine load in advance, is
The slice level temperature corresponding to the current engine load and rotation speed is determined from a map that stores the slice level temperature Tm for misfire detection based on the exhaust temperature for each operating region divided into a plurality of regions according to the engine speed N and the engine speed N. Search and find Tm.

The basic fuel injection amount Tp indicating the engine load is determined from a map (step 13.
Please refer to the map (referenced in 9.12).

In step 7, T#l, which is the set exhaust temperature of cylinder #l, is compared with the slice level temperature Tm.

Here, if the exhaust temperature T#l of the #1 cylinder exceeds the slice level temperature Tm, it is assumed that the #1 cylinder is combusting normally without misfire, and the process proceeds to step 9. Similarly to No. 13, the map in which the basic fuel injection amount Tp corresponding to the air amount corresponding to the normal combustion state is stored is referred to, and the reference result is set as the basic fuel injection amount Tp for the #I cylinder.

On the other hand, if the exhaust temperature T#1 of the #1 cylinder is less than the slice level temperature Tm, it is assumed that the exhaust temperature has decreased in the #1 cylinder due to a misfire, as shown in FIG. Proceed to step 8.

Note that in determining whether or not the exhaust gas temperature is below the slice level temperature Tm, the actual exhaust gas temperature remains below the slice level temperature Tm for a predetermined period of time (for example, 0.
5m5), the actual exhaust temperature reaches Tm for the first time.
Preferably, the configuration is such that it is determined that the value has decreased.

In step 8, the basic fuel injection amount Tp corresponding to the intake air amount in the misfire state is determined in advance by referring to a map stored for each operating region divided into a plurality of regions according to the throttle valve opening α and the engine rotation speed N. , a misfire fuel injection iTp corresponding to the current throttle valve opening α and engine rotational speed N is searched, and this is set as the basic fuel injection amount Tp for the #1 cylinder.

That is, in a two-stroke internal combustion engine l that performs scavenging, when a misfire occurs, the amount of intake air is drastically reduced. Therefore, when referring to a map in which the basic fuel injection amount Tp is stored in anticipation of the amount of intake air in a normal combustion state, Since the basic fuel injection amount Tp is set to match the amount of air that is larger than the actual amount, the amount of air when a misfire occurs and the amount of intake air is drastically reduced is determined based on the throttle valve opening α and the engine speed N. In this case, when a misfire occurs, a basic fuel injection amount Tp corresponding to the drastically reduced amount of air is set.

Therefore, even under the same throttle valve opening α and engine speed N conditions, the map that refers to the basic fuel injection amount Tp is changed depending on whether a misfire has occurred in each cylinder. This prevents the air-fuel ratio of the intake air-fuel mixture from becoming overrich even if the amount of air drastically decreases due to a misfire, thereby preventing the ignition plug 16 from getting wet with the fuel. By continuing injection, it is possible to quickly recover from a misfire condition.

Based on the same misfire determination (switching of the basic fuel injection amount Tp map is also performed for the #2 cylinder, the exhaust temperature T#2 of the #2 cylinder is compared with the slice level temperature Tm in step lO, and the exhaust temperature When a misfire occurs in the #2 cylinder where T#2 is lower than the slice level temperature Tm, the process proceeds to step II, and the misfire map in which the basic fuel injection amount Tp corresponding to the misfire is set is referenced to determine the misfire in the #2 cylinder. The basic fuel injection amount Tp corresponding to is determined.

On the other hand, when it is determined in step 10 that the exhaust temperature T#2 of the #2 cylinder exceeds the slice level temperature Tm, it is assumed that combustion is occurring normally in the #2 cylinder,
Proceeding to step 12, the basic fuel injection amount Tp corresponding to the #2 cylinder is determined with reference to the map for ignition in which the basic fuel injection amount Tp corresponding to normal combustion is set.

In this way, by comparing the exhaust temperature detected for each cylinder with the slice level, it is determined whether a misfire has occurred for each cylinder, and the basic fuel injection amount Tp is referred to for each cylinder according to the determination. By switching the map, even if the actual air amount decreases drastically due to a misfire compared to the air amount corresponding to the throttle valve opening α and engine speed N during normal combustion, the air-fuel ratio of the intake mixture will exceed It is possible to avoid enrichment, thereby suppressing the fuel temperature of the ignition plug 16 and recovering from a misfire condition.

In this embodiment, the map for determining the basic fuel injection amount Tp from the throttle valve opening α and the engine rotational speed N is changed based on the misfire determination for each cylinder, or the map for calculating the basic fuel injection amount Tp from the throttle valve opening α and the engine speed Data on the intake air flow rate Q is stored in a map with the rotational speed N as a parameter, and two such maps are provided, one for normal combustion and one for misfire, and these are switched and referenced based on misfire determination. You can do it like this.

Furthermore, the basic fuel injection amount Tp or the intake air flow rate Q may be determined by calculation from the throttle valve opening α and the engine speed N. In this case, the calculation formula may be switched depending on the misfire determination. good.

In addition to detecting the occurrence of a misfire in each cylinder, in addition to the above-mentioned detection results of the exhaust gas temperature in each cylinder, it is also possible to detect The occurrence of a misfire in each cylinder may be detected based on the detection result of the intake pressure pulsation level, etc., and the misfire detection means is not limited.

<Effects of the Invention> As explained above, according to the present invention, misfire occurrence is prevented in an electronically controlled fuel injection device that controls the fuel injection amount in a two-stroke internal combustion engine based on the opening area of the engine intake system and the engine rotation speed. Even if the amount of intake air is drastically reduced compared to normal combustion, it is possible to inject fuel that is approximately commensurate with the change in air amount, thereby suppressing the fuel temperature at the ignition plug in the event of a misfire, and preventing a misfire. This has the effect of helping to recover the

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system schematic diagram showing an embodiment of the present invention, FIG. 3 is a flowchart showing details of fuel control in the above embodiment, and FIG.
The figure is a time chart showing how misfire detection is performed based on exhaust temperature in the above embodiment. 1... Internal combustion engine (2-stroke gasoline engine) 9...
Throttle valve 10... Fuel injection valve 11... Control unit 12... Rotation sensor 13...
Throttle sensor 15...Exhaust temperature sensor Patent applicant: Japan Electronics Co., Ltd. Patent attorney: Fujio Sasashima

Claims (1)

[Scope of Claims] An engine rotation speed detection means for detecting an engine rotation speed; an opening area detection means for detecting an opening area of an engine intake system that is variably controlled; ignition fuel injection amount setting means for setting the ignition fuel injection amount based on the detected engine rotational speed and opening area; and a misfire fuel injection amount for setting the misfire fuel injection amount based on the detected engine rotational speed and opening area. a setting means; a misfire detection means for detecting whether a misfire has occurred in each cylinder of the engine; and a misfire detection means that determines either the ignition fuel injection amount or the misfire fuel injection amount for each cylinder based on the result of the misfire detection means. an electronic control unit for a two-stroke internal combustion engine, comprising: fuel injection control means for selecting either one of the two and controlling the drive of fuel injection valves provided for each cylinder based on the selection result; Control fuel injector.