JPH02283832A - Fuel injection amount control device for 2-cycle engine - Google Patents

Abstract

PURPOSE:To prevent an air-fuel ratio from being brought into a transient state during failure in ignition by a method wherein during failure in ignition of a cylinder, a control map is immediately switched from a control map responding to normal operation to a control map responding to operation during failure in ignition to decide an amount of fuel injected during failure in ignition. CONSTITUTION:In a 2-cylinder engine, fuel indication sensors 181 and 182 and fuel injection valves 81 and 82 are mounted to each cylinder, and detected indication signals Pi1 and Pi2 are inputted, in order, to a failure in ignition detecting means 20 through a cylinder discriminating means 19. A number of revolutions signal Ne and a throttle valve opening signal thetath are inputted to a normal fundamental injection map 21 and a failure in ignition period fundamental injection amount map 22. The maps 21 and 22 are selectively used by a switching means 23 switched by means of an output from a failure in ignition detecting means 20. A fundamental fuel injection amount Tif or Tim determined according to the presence of failure in ignition is corrected by a injection amount correcting means 24 according to the values of input signals A-C, and the fuel injection valves 81 and 82 are controlled by means of a fuel injection amount Ti after correction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection device for a two-stroke engine, and more particularly to an electronic fuel injection device (EFI) in which the fuel injection device is controlled by an electronic control circuit.

In the publication No. 63-40257, the crank chamber preload type 2
The internal cycle engine includes a pressure detector that detects a crank chamber pressure, and a control device that controls a fuel injection amount based on the output of the pressure detector, and detects an intake air amount based on a variation in the crank chamber pressure. A fuel injection device for an internal combustion engine is shown in which the amount of fuel to be injected is determined by the following steps.

This fuel injection device is a so-called mass flow type EF that controls the fuel injection amount depending on the intake air amount and engine rotation speed.
EFI is a speed density method in which the fuel injection amount is controlled by intake pipe pressure and engine speed.
is also conventionally known.

Further, a so-called throttle speed type EFI is known in which the fuel injection amount is controlled by the throttle valve opening and the engine rotation speed. In this method, depending on the combination of engine speed and throttle valve opening,
A control map is prepared in which the necessary fuel injection time is stored in memory in advance, and during operation, the fuel injection time is determined from the control map based on the engine speed and throttle valve opening detected by the sensor. read and output,
This controls the amount of fuel supplied. The control map measures exhaust gas, horsepower, fuel efficiency, etc. by operating the actual machine and changing the fuel injection amount, or fuel injection time, while keeping the engine speed and throttle valve opening constant, and then calculates these measured values. The fuel injection time storage method and device is created by comprehensively determining the optimal fuel injection time and storing the time in a memory address determined by a combination of engine speed and throttle valve opening. is disclosed in Japanese Patent Publication No. 62-8624.

The present invention is intended to solve the following problems that occur when the above-mentioned throttle speed type EFI is applied to a high-performance two-stroke engine such as that used in a racer.

These high-performance two-stroke engines highly utilize the exhaust pulsation in the exhaust pipe during operation to increase charging efficiency, so the amount of intake air during operation and during motoring, where exhaust pulsation cannot be utilized, are reduced. There is a significant difference between the two. Figure 1 shows the engine speed N0 and intake air amount GA in a high-performance two-stroke engine as described above.
In this graph, curve F shows the intake air amount at the throttle valve opening during operation, that is, when combustion is occurring in the cylinder, and curve M shows the amount of intake air at the throttle valve opening during motoring, that is, when combustion is occurring in the cylinder. The difference between the intake air amounts F and M is small in the low rotation speed range, which shows the amount of intake air at the same throttle valve opening when the throttle valve is not opened.
In a high rotation speed range, there is a large difference between the intake air amount F during operation that utilizes exhaust pulsation and the intake air amount M during motoring that does not utilize exhaust pulsation. Note that if a misfire occurs during operation, the intake air amount falls from the value of curve F to the value of curve M.

The control map is naturally created based on the curve F, and stores the optimal fuel injection amount for the intake air amount F. Therefore, if a misfire occurs during operation, fuel corresponding to the intake air amount F is injected even though the intake air amount decreases to M, and the air-fuel ratio becomes excessively rich, and this state continues.
Once the engine misfires, it becomes impossible to re-ignite or restart the engine. For this reason, the fuel injection amount control device for a two-stroke engine according to the present invention includes a control map corresponding to normal operation, a control map corresponding to misfire, and a misfire detection means for detecting misfire. During normal operation, the fuel injection amount is controlled based on a control map corresponding to the normal operation, and when the misfire detection means detects a misfire, the fuel injection amount is controlled based on the control map corresponding to the misfire.

According to the present invention, when the engine is operating normally, the operation shown in FIG. The optimal fuel injection amount for the time intake air amount curve F is read, and the fuel supply amount is controlled based on this. When the engine misfires, the misfire detection means detects this and issues a misfire detection signal, and this signal causes the control map to be switched from a control map corresponding to normal operation to a control map corresponding to the misfire. As a result, the next fuel injection amount is determined by the control map corresponding to the misfire, and becomes the optimum fuel injection amount for the intake air amount curve M during motoring, that is, at the time of misfire, as shown in FIG. This will not happen, and in the next cycle the mixture will ignite and the engine will be back in operation.

1 Oboro■ Figure 2 is a schematic diagram showing an embodiment of the present invention, in which 1 is a two-stroke engine, 2 is a crank chamber thereof, 3 is a cylinder, 4 is a piston, 5 is a connecting rod, and 6 is a crankshaft. Fuel is injected from the fuel injection valve 8 into the air flowing through the intake pipe 7 to create an air-fuel mixture, and this air-fuel mixture is sucked into the crankcase 2 through the reed valve 9. crank case 2
The air-fuel mixture therein is sent into the cylinder chamber above the piston via a scavenging passage 10 and an intake passage (not shown), compressed by the piston 4, and then ignited by the spark plug 11 and combusted. Combustion gases are exhausted through the exhaust pipe 12.

A throttle valve 13 is provided in the intake pipe 7, and the amount of intake air is adjusted by the opening degree of the throttle valve 13, and an amount of fuel commensurate with this amount of intake air is injected from the fuel injection valve 8. Fuel at a constant pressure is supplied to the fuel injection valve 8 from a fuel tank 14 via a fuel pump 15 and a pressure regulating valve 16. The fuel injection valve 8 is an electromagnetic fuel injection valve that opens in response to a fuel supply signal I output from the arithmetic unit 17, and remains open during the duration of the signal I. Therefore, the fuel injection valve 8
The fuel injection amount is determined by the time width of signal I, that is, the fuel injection time.

The arithmetic device 17 is constituted by a microcomputer, and a throttle valve opening signal θ and a rotation speed signal N are inputted to the arithmetic device 17 from each sensor provided on the throttle valve 13 and the crankshaft 6, respectively. Ru. Further, the cylinder 3 is provided with a fuel shiatsu sensor I8, from which a shiatsu pressure signal P is inputted to the arithmetic unit 17, and a misfire is determined based on the peak level of the signal P. An exhaust pressure sensor, a combustion light sensor, or the like may be provided in place of the fuel finger pressure sensor 18, and misfires may be detected using input signals from these sensors.

The calculation device 17 is further inputted with a cooling water temperature signal A, a crankcase temperature signal B, a transmission position signal C, etc., and the calculation device 17 calculates the required fuel injection amount based on these input signals and injects the fuel for an appropriate amount of time. Outputs a fuel supply signal I of width.

FIG. 3 is an explanatory diagram showing the functions of the arithmetic unit 17 in blocks. In this figure, the engine 1 is shown as a two-cylinder engine, and each cylinder is provided with a fuel pressure sensor i8+, t8□, and a fuel injection valve 8.18□. Fuel finger pressure sensor 18. ．． The finger pressure signals Pil and Pig from 182 are sequentially sent to the misfire detection means 20 via the cylinder discrimination means 19, and it is judged one after another whether each cylinder is in a normal operating state or a misfire state. The rotational speed signal N and the throttle valve opening signal θ are manually input to two control maps, namely, a normal basic injection amount map 21 and a basic injection amount map 22 in the event of a misfire. The map 21 stores the basic fuel injection amount (fuel injection time) for each combination of N8 and θ during normal operation, that is, the fuel injection amount corresponding to the intake air amount curve F in Fig. 1. Map 21 is searched by N, and θ, and the normal basic injection amount TiF is determined.
is selected. Map 22 shows N2 and θ at the time of misfire.
The basic fuel injection amount corresponding to the intake air amount curve M shown in FIG. ;, 4 are selected.

Either TiF or T1 is sent to the injection amount correction means 24 via the control map switching means 23 shown in the form of a switch, but when the detection means 20 does not detect a misfire, that is, during normal operation, The basic injection amount map 21 is connected to the injection amount correction means 24, and TiF is sent to the injection amount correction means 24. When the detection means 20 detects a misfire, the control map switching means 23 changes the misfire basic injection amount map 22 to the injection amount. It is connected to the correction means 24 and TiH is sent to the injection amount correction means 24. The signals A, B, and C are also input to the injection amount correction means 24, and the basic injection amount T or T sent via the control map switching means 23 is inputted to the injection amount correction means 24.
in is corrected according to the values of the human input signals A, B, and C, and the fuel injection amount T is calculated. Then, this fuel injection amount T is sent to the fuel supply signal forming means 25, and the means 25 generates a fuel supply signal 1. , L are sequentially formed and the fuel injection valve 8. Sent to 8□.

The above calculation of the fuel injection amount is performed as shown in Fig. 4 for each cylinder (hereinafter, to distinguish between the two cylinders, one cylinder is indicated as N1 and the other cylinder as N2) at every crank angle of 360°. This is done by the fuel injection routine. In step (]), the i-th cylinder (in this example, cylinder #1
or N2), the calculation start time is determined. During this period, two sets of T with a phase difference of 180'' are emitted from the crank angle sensor for each cylinder at every 360 degrees of crank angle.
For example, the TD of cylinder #1 is determined based on the DC pulse.
When the C pulse arrives, calculation for cylinder #1 is started. First, in step (2), it is determined whether or not the previous cycle of cylinder #1 was a misfire. This is determined by whether or not a misfire detection signal is output from the misfire detection means 20. If no misfire is detected, step (
Proceed to 3) and find N8, θ, at that time.

The normal basic injection amount map 21 is searched and the normal basic injection amount Tit is read, and this TiF is read in step (4).
), the fuel injection amount T is calculated by being corrected by the signal input A, BSC, etc. This T.

Next, in step (5), the fuel supply signal 11 is formed and sent to the fuel injection valve 81.

If a misfire is detected in step (2), the process proceeds to step (6), the misfire basic injection amount map 22 is searched, the misfire basic injection amount TiM is read, and these T and I are used in step (4). ) and then processed to form a fuel supply signal in step (5).
The fuel supply signal 11, which has a shorter duration than during normal operation, is applied to the fuel injector 8. sent to. In this way, a small amount of fuel is supplied to the misfired cylinder in accordance with the amount of intake air at the time of the misfire, so the misfire state can be easily escaped without the mixture becoming too rich.

When the fuel injection to cylinder #1 is completed in this way, the process returns to step (1) and waits for the TDC pulse of cylinder #2 to arrive. When this TDC pulse arrives, the same process is performed for cylinder #2. The calculation is performed and the fuel supply signal I2 is sent to the fuel injection valve 8□.

As mentioned above, the present invention is equipped with a control map in which the optimum fuel injection amount for each combination of engine rotation speed and throttle valve opening is stored in advance, and the fuel injection amount is determined based on the engine rotation speed and throttle valve opening. In a fuel injection amount control device for a two-stroke engine that performs control based on the control map according to the valve opening degree, there is provided a control map corresponding to normal operation, a control map corresponding to a misfire, and a misfire detection for detecting a misfire. and means for controlling the fuel injection amount based on the control map corresponding to the normal operation during normal operation, and controlling the fuel injection amount based on the control map for the misfire when the misfire detection means detects a misfire. Therefore, when a cylinder misfires, the control map is immediately switched from the control map corresponding to normal operation to the control map corresponding to the misfire, and the fuel injection amount is determined by the latter control map, which prevents the misfire from occurring. The air-fuel ratio is controlled to an appropriate level. Therefore, the air-fuel ratio will not become too rich in the event of a misfire.
It is possible to quickly return to a normal operating state from a misfire state.

[Brief explanation of drawings]

Fig. 1 is a graph illustrating the relationship between engine speed and intake air amount in a high-performance two-stroke engine, Fig. 2 is an overall schematic diagram showing an embodiment of the present invention, and Fig. 3 is a block diagram of the functions of the arithmetic unit. FIG. 4 is a flowchart showing the fuel injection routine of the device. 1...Engine, 2...Crankcase, 3...
Cylinder, 4... Piston, 5... Connecting rod, 6
...Crankshaft, 7...Intake pipe, 8...Fuel injection valve, 9...Reed valve, 10...Scavenging passage, 11...
・Spark plug, 12...Exhaust pipe, 13...Throttle valve, 14...Fuel tank, 15...Fuel pump,
16... Pressure regulating valve, 17... Arithmetic device, 18... Fuel finger pressure sensor, 19... Cylinder discrimination means, 20... Misfire detection means, 21... Normal basic injection amount map, 22.
. . . Basic injection amount map at the time of misfire, 23 . . . Control map switching means, 24 . . . Injection amount correction means, 25 . . . Fuel supply signal forming means.

Claims (1)

[Claims] A control map is provided in which the optimal fuel injection amount for each combination of engine speed and throttle valve opening is stored in advance, and the fuel injection amount is controlled based on the control map according to the engine speed and throttle valve opening. In the fuel injection amount control device for a two-stroke engine, a control map corresponding to normal operation, a control map corresponding to a misfire,
a misfire detection means for detecting a misfire; during normal operation, the fuel injection amount is controlled based on the control map corresponding to the normal operation, and when the misfire detection means detects a misfire, the fuel injection amount is controlled based on the control map corresponding to the misfire. A fuel injection amount control device that controls a fuel injection amount based on the fuel injection amount.