JPH0316498B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically controlled fuel injection method for an internal combustion engine, and particularly to an engine intake injection method suitable for use in an automobile engine equipped with an intake pipe pressure type electronically controlled fuel injection device. An electronically controlled fuel injection method for an internal combustion engine, in which the basic injection amount is determined according to pipe pressure and engine speed, and the fuel injection amount is determined by correcting the basic injection amount according to the engine operating state. Regarding the improvement of

2. Description of the Related Art One of the methods for supplying an air-fuel mixture at a predetermined air-fuel ratio to the combustion chamber of an internal combustion engine such as an automobile engine uses an electronically controlled fuel injection device. In this method, an injector for injecting fuel into the engine is installed in the intake manifold or throttle body of the engine, for example, in several or one engine cylinder, and the valve opening time of the injector is adjusted depending on the operating state of the engine. By controlling the air-fuel mixture, a mixture having a predetermined air-fuel ratio is supplied to the engine combustion chamber. This electronically controlled fuel injection system can be roughly divided into two types: one that calculates the basic injection amount according to the intake air amount and engine speed of the engine;
There are a so-called intake air amount type electronically controlled fuel injection device and a so-called intake pipe pressure type electronically controlled fuel injection device which determines a basic injection amount according to the intake pipe pressure and engine speed of the engine.

Among these, the former allows for precise control of the air-fuel ratio, and has come to be widely used in automobile engines equipped with exhaust gas purification measures. However, in this intake air volume type electronically controlled fuel injection system, the intake air volume changes by about 50 times between idle and high load, and the dynamic range is wide, so the intake air volume is converted into an electrical signal. Not only does this result in lower accuracy, but if you try to improve the calculation accuracy in the digital control circuit at the subsequent stage, the bit length of the electrical signal becomes longer, and it becomes necessary to use an expensive computer as the digital control circuit. Furthermore, in order to measure the amount of intake air, it is necessary to use a measuring device with a very precise structure, such as an air flow meter, resulting in problems such as high equipment costs.

On the other hand, in the latter type of intake pipe pressure type electronically controlled fuel injection system, the amount of change in intake pipe pressure is small, about 2 to 3 times, and the dynamic range is narrow.
Not only is the arithmetic processing in the subsequent digital control circuit easy, but the pressure sensor for detecting the intake pipe pressure is also inexpensive.

However, if a blind plug or the like comes off due to a backfire or the like on the downstream side of the throttle valve, causing an abnormal flow of air into the intake manifold, etc., this intake pipe pressure-type electronically controlled fuel injection system will be able to detect the air abnormality. Since the amount of fuel to be injected is determined to match the intake pipe pressure that has increased due to the inflow, the output increases by the amount of air flow, which may cause the engine speed to rise abnormally against the driver's will. The sex was hot. On the other hand, in the former type of electronically controlled fuel injection device that uses an intake air amount, the fuel injection amount is not increased in response to an abnormal inflow of air that occurs downstream of the air flow meter that detects the intake air amount. The air-fuel ratio became over-lean, and the above-mentioned problems did not occur.

The present invention has been made to solve the above-mentioned conventional drawbacks, and is an electronically controlled fuel injection method for an internal combustion engine that prevents the engine speed from increasing abnormally even if air abnormally inflows downstream of the throttle valve. The purpose is to provide

The present invention provides an internal combustion engine which determines the fuel injection amount by determining the basic injection amount according to the intake pipe pressure and engine rotation speed of the engine, and by correcting the basic injection amount according to the engine operating condition. In an electronically controlled fuel injection method for an engine, the value of the intake pipe pressure is assumed from the throttle valve opening and the engine speed, and when the detected value of the intake pipe pressure is larger than the assumed value, the basic injection amount is changed. The above object is achieved by fixing the value to a predetermined value.

Further, the predetermined value is a constant value to facilitate calculation.

Alternatively, the predetermined value is determined from the throttle valve opening degree and the engine rotational speed, so that relatively smooth engine rotation can be continued even in the event of abnormal air inflow.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an intake pipe pressure type electronically controlled fuel injection device employing the electronically controlled fuel injection method for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, this embodiment includes an air cleaner 12 for taking in outside air, and the air cleaner 1.
An intake air temperature sensor 14 for detecting the temperature of the intake air taken in by 2, and an intake air temperature sensor 14 are disposed in the intake passage 16, and are opened and closed in conjunction with an accelerator pedal (not shown) disposed in the driver's seat. throttle valve 18 for controlling the flow rate of intake air
and a throttle sensor 20 including an idle switch for detecting whether or not the throttle valve 18 is at an idle opening, and a potentiometer that generates a voltage output proportional to the opening of the throttle valve 18.
and a surge tank 22 to prevent intake interference.
, an intake pipe pressure sensor 23 for detecting intake pipe pressure from the pressure in the surge tank 22, and a bypass passage 2 that bypasses the throttle valve 18.
4, disposed in the middle of the bypass passage 24,
By controlling the opening area of the bypass passage 24, fuel is injected toward the idle rotation control valve 26 for controlling the idle rotation speed and the intake port of the engine 10 disposed in the intake manifold 28. an oxygen concentration sensor 34 disposed in the exhaust manifold 32 for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas; Three-way catalytic converter 3 installed
8, a distributor 40 having a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10, and the distributor 40.
A top dead center sensor 42 and a crank angle sensor 44, which respectively output a top dead center signal and a crank angle signal in accordance with the rotation of the distributor shaft, are built in, and an engine cooling water temperature sensor is installed in the engine block. Cooling water temperature sensor 4 for detecting
6, the basic injection amount per engine stroke is determined according to the engine rotation speed determined from the intake pipe pressure output from the intake pipe pressure sensor 23 and the crank angle signal output from the crank angle sensor 44, and this is The fuel injection amount is determined by correcting the output of the torque sensor 20, the air-fuel ratio of the output of the oxygen concentration sensor 34, the engine cooling water temperature of the output of the cooling water temperature sensor 46, and the like. It outputs a valve time signal, determines the ignition timing according to the engine operating state, and outputs an ignition signal to the igniter-equipped coil 52;
In the intake pipe pressure type electronically controlled fuel injection system for the automobile engine 10, which includes a digital control circuit 54 that controls the idle rotation control valve 26 during idle, the output of the throttle sensor 20 is controlled within the digital control circuit 54. The value of the intake pipe pressure is assumed from the throttle valve opening and the engine speed obtained from the crank angle signal output from the crank angle sensor 44, and the detected value of the intake pipe pressure output from the intake pipe pressure sensor 23 is determined to be the assumed value. When it is larger than , the basic injection amount is fixed at a predetermined constant value.

As shown in detail in FIG. 2, the digital control circuit 54 is a central processing unit (hereinafter referred to as CPU) consisting of a microprocessor that performs various arithmetic operations.
60, the intake temperature sensor 14, the potentiometer of the throttle sensor 20, and the intake pipe pressure sensor 2.
3. An analog input port 62 with a multiplexer for converting analog signals input from the oxygen concentration sensor 34, cooling water temperature sensor 46, etc. into digital signals and sequentially inputting them to the CPU 60; and an idle switch for the throttle sensor 20; Digital signals input from the top dead center sensor 42, crank angle sensor 44, etc. are sent to the CPU 60 at a predetermined timing.
A digital input port 64 for importing programs or various constants, etc., and a read-only memory (hereinafter referred to as ROM) 66 for storing programs or various constants, etc.
Random access memory (hereinafter referred to as RAM) for temporarily storing calculation data etc. in the CPU 60
) 68, a backup random access memory 70 which can be supplied with power from an auxiliary power source and retain its memory even when the engine is stopped, and the calculation results of the CPU 60 are transmitted to the idle rotation control valve 26, injector 30, and coil with igniter at a predetermined timing. 52, etc., and a common bus 74 that connects each of the above-mentioned component devices.

The operation will be explained below with reference to FIG.

The digital control circuit 54 first starts at step 101.
The engine speed NE calculated from the crank angle signal output from the crank angle sensor 44 and the intake pipe pressure detection value output from the intake pipe pressure sensor 23.
Take in PM. Next, in step 102, the basic injection time TP is determined according to the engine speed NE and the intake pipe pressure PM. Then, in step 103,
The throttle valve opening TA output from the throttle sensor 20 is taken. Furthermore, in step 104, depending on the throttle valve opening TA and the engine speed NE,
The assumed value PMO of the intake pipe pressure is determined from a map showing the relationship as shown in FIG. 4, for example, which is stored in advance in the ROM 66. Further, the process proceeds to step 105, where the detected intake pipe pressure value PM is equal to the expected value PMO.
Determine whether or not it exceeds. If the determination result is positive, it is determined that air is abnormally flowing in, and the process proceeds to step 106, where a predetermined constant value TO is set as the basic injection time TP. After the completion of step 106, or when the judgment result in step 105 is negative and it is judged that the system is in a normal state with no abnormal inflow of air, the process proceeds to step 107, where the constant injection amount TO or basic injection is performed. Execute fuel injection based on the amount TP and end this program.

As a result, the detected intake pipe pressure value PM becomes the expected value.
When it is larger than PMO, the basic injection amount TP is fixed to a constant injection amount TO, thereby preventing an abnormal increase in engine speed.

In this embodiment, the detected intake pipe pressure value PM
is larger than the expected value PMO, the basic injection amount
Since TP is fixed at a predetermined constant value TO, calculation is relatively easy. Note that the method of fixing the basic injection amount TP to a predetermined value when the detected value PM of the intake pipe pressure is larger than the expected value PMO is not fixed to this method.
is larger than the assumed value PMO, the basic injection amount
TP, throttle valve opening TA and engine speed
It is also possible to fix it to a predetermined value determined from NE. In this case, since the basic injection amount is fixed to a predetermined value depending on the engine operating state, it is possible to continue the engine rotation relatively smoothly.

As described above, the present invention has the excellent effect of being able to prevent an abnormal increase in engine speed due to abnormal inflow of air downstream from the throttle valve.

[Brief explanation of drawings]

FIG. 1 includes a partial block diagram showing the configuration of an embodiment of an intake pipe pressure type electronically controlled fuel injection device for an automobile engine in which the electronically controlled fuel injection method for an internal combustion engine according to the present invention is adopted. 2 is a block diagram showing the configuration of the digital control circuit used in the embodiment, and FIG. 3 is a flowchart showing a program for determining the basic injection amount in the digital control circuit. , FIG. 4 is a diagram showing the relationship between the maps used in the program for determining the assumed value of the intake pipe pressure from the throttle valve opening and the engine speed. 10...Engine, 14...Intake temperature sensor, 1
8... Throttle valve, 20... Throttle sensor, 23... Intake pipe pressure sensor, 30... Injector, 40... Distributor, 44...
Crank angle sensor, 54...digital control circuit.

Claims (1)

[Scope of Claims] 1. The fuel injection amount is determined by determining the basic injection amount according to the intake pipe pressure of the engine and the engine speed, and correcting the basic injection amount according to the engine operating condition. In the electronically controlled fuel injection method for internal combustion engines, the value of intake pipe pressure is assumed from the throttle valve opening and engine speed,
An electronically controlled fuel injection method for an internal combustion engine, characterized in that the basic injection amount is fixed at a predetermined value when the detected value of the intake pipe pressure is larger than the assumed value. 2. The electronically controlled fuel injection method for an internal combustion engine according to claim 1, wherein the predetermined value is a constant value. 3. The electronically controlled fuel injection method for an internal combustion engine according to claim 1, wherein the predetermined value is a value determined from the throttle valve opening and the engine speed.