JPS62258147A - Fuel control device for electronic fuel injection engine - Google Patents

Abstract

PURPOSE:To prevent damage of an engine and the like due to erroneous control of fuel, by a method wherein, when a load detecting means is mechanically failed in a high intake air flow rate area, a fuel injection amount is decided based on an intake air flow rate and the number of revolutions of an engine as in a low intake air flow rate to perform control of fuel injection. CONSTITUTION:In a fuel control device 30, a pulse computing circuit 32 for an L-J system outputs a given fuel injection injector drive pulse based on an intake air flow rate and the number of revolutions of an engine. A pulse difference learning circuit 33 outputs a difference between the two pulses. In this casea D-J system trouble deciding circuit 34 outputs a D-J system failure in operation deciding signal based on a pulse difference and boost. When a failure in operation is decided, a selection release signal is outputted to a pulse selecting circuit 36, and a drive pulse signal by the L-J system is substantially outputted to a fuel injection injector 12.

Description

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

(Prior Art) Conventionally, as a fuel control device for an electronic fuel injection engine, an engine intake air flow rate detector, an intake pipe internal pressure detector as an engine load detection means, and an engine rotation speed detector are connected to a fuel control means, When the intake air flow rate is detected to be less than a predetermined intake air amount, the intake air flow rate detector and engine rotation speed detection +! The air flow rate sensing method (the so-called L-Jetronic method, which generally has a narrow measurement target flow rate range but has excellent measurement accuracy, hereinafter abbreviated as L-J method), also allows the intake air flow rate detector to detect a predetermined intake air amount. If the above is detected, the speed density method (generally known as the flow rate to be measured, which has a wide range but has some accuracy on the needle side) creates a fuel injector based on the output signal of the intake pipe pressure detector and engine speed detector. Inferior D-
Jetronic method (hereinafter abbreviated as D-J method)
There are known fuel injection systems that perform fuel injection control using various methods (see, for example, Japanese Patent Publication No. 7017/1983).

However, with this type of conventional fuel control device, when the intake pipe pressure detector fails, the fuel is erroneously controlled, resulting in excessive knocking and misfire, which can damage the engine and the exhaust purification catalytic converter. However, no special measures were taken to prevent such failures.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems in the conventional art, and is an intake air intake system that detects intake negative pressure downstream of a throttle valve used in a high intake flow rate region where the intake air flow rate or load is equal to or higher than a predetermined value. If the load detection means such as the pipe pressure detector breaks down,
As in the low intake flow area, the 3PY fuel injection amount is determined based on the intake air flow rate and engine speed, and fuel injection control is performed to prevent the engine and catalytic converter from being damaged by strong knocks or misfires. The purpose is to

(Structure of the Invention) The structure of the present invention for achieving the above object will be explained using FIG. 1 and FIG. 2 corresponding to the embodiment. A detection means (air flow make 13), a load detection means (boost measurement sensor 18) that detects a signal related to the intake negative pressure downstream of the throttle valve 14 or the throttle valve opening, and an engine rotation speed detection means (boost measurement sensor 18) that detects the engine rotation speed. engine rotation speed detector 23), and first fuel injection amount calculation means (L-J system pulse calculation circuit 31) that determines the fuel injection amount based on the outputs of the intake air flow rate detection means and engine rotation speed detection means. and a second fuel injection amount calculation means (D-J method pulse calculation circuit 32) that determines the fuel injection amount based on the outputs of the load detection means and the engine rotation speed detection means, and The fuel injection valve is actuated based on the output of the first fuel injection amount calculation means in a low intake flow rate region below the predetermined value, and based on the output of the second fuel injection amount calculation means in a high intake flow rate region equal to or higher than the predetermined value. A fuel control device for an electric fuel injection engine is provided, which has a switching control means (pulse selection circuit 36) for determining the load detection means, and a failure determination means (DJ system failure determination means 34) for determining a failure of the load detection means, and the failure determination means 34 for determining a failure of the load detection means. The present invention is characterized by comprising a switching canceling unit (selection canceling circuit 37) which receives the output of the determining unit and cancels the switching of the switching control unit to select the first fuel injection amount calculation unit regardless of the intake air flow rate. .

That is, 1 the present invention uses the first fuel injection amount calculation means used in the low intake flow rate region also in the high intake flow rate region to perform fuel injection based on the determination of failure of the load detection means used in the high intake flow rate region. It is for controlling.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, a fuel injector 12 installed in an intake manifold 11 that supplies intake air to the engine body 1o is supplied with fuel whose pressure is regulated to a constant level relative to the pressure inside the intake manifold 11. , current flows through the solenoid coil section for a period of time controlled by the fuel control device 30, and fuel is injected from the nozzle section. A hot wire type air flow make 13 using platinum that changes temperature resistance in response to the intake air flow rate is installed in the intake pipe 15 upstream of the throttle 1pr4, and is capable of measuring the intake air amount in the entire load range. However, the intake air b1 is mainly measured in the low intake flow rate region during medium and low load operation. On the other hand, the throttle of intake manifold 11 is 1
A boost measurement sensor 18 is provided downstream Δ11 of No. 4 to measure the intake negative pressure, that is, the booth i· mainly in the high intake flow rate region. Reference numeral 20 denotes an exhaust pipe, which includes an oxygen concentration detector 21 for detecting an air-fuel ratio and a catalytic converter 22 for purifying exhaust gas. Further, an engine rotation speed detector 23 is mounted on the distributor (not shown), and a crank angle detector 2 as a pulse signal generator that generates five pulses at a predetermined angle position of the crankshaft is mounted on the end of the crankshaft.
4 are provided respectively.

As shown in the block diagram of FIG. 2, in the fuel control device 30 of this embodiment, the L-J method pulse calculation circuit 31 receives the input of the intake air amount signal from the air flow meter 13 and the engine rotation speed detector. 23 receives an engine rotation speed signal and outputs an optimal fuel injection injector drive pulse (τL) signal in the L-J method. On the other hand, the pulse calculation circuit 32 for the D- and J methods receives the input of the booth I signal from the boost measurement sensor 18 and the input of the engine revolution speed signal from the engine revolution speed detector 23, and receives the input of the booth I signal from the boost measurement sensor 18 and the input of the engine revolution speed signal from the engine revolution speed detector 23. Outputs an injector drive pulse (τD, ) signal.

The pulse difference learning circuit 33 uses the L-J method and the D-
11 In response to the input of the respective fuel injection injector driving pulse (τL, τD,) signals on the two sides, a difference (ΔτD) signal between the two human power pulses is output. I]-J method failure f+1
The constant circuit 34 inputs the pulse difference (ΔτD) signal and the boost signal to determine the experimentally determined failure 'i!' at each load stage. 1 Compares the predetermined value with the predetermined value and outputs a D-, J method failure determination signal. Further, the pulse correction circuit 35 for the DJ method inputs the fuel injection injector drive pulse (τ0.) signal and the pulse difference (D at Δ) signal in the above-mentioned J method, and adjusts the pulse correction circuit 35 to correspond to the pulse difference ΔτD. Outputting the corrected optimal injector drive pulse (τD) signal 6
The pulse selection circuit 36 selects the corrected fuel injection injector drive pulse (τ0) signal in the -J method and the L
- Fuel injection in the J method - Injector drive pulse (τL) signal, D A 1 selection cancellation circuit 37 that amplifies a J-type or L-J type fuel injection injector drive pulse signal with an amplifier as appropriate and outputs it to the fuel injection injector 12 receives a failure determination signal and selects it to the pulse selection circuit 36 in the event of a failure. Outputs a release signal.

However, when the selection cancellation signal is input to the pulse selection circuit 36, the intake air amount signal from the air flow meter 13 is input in place of the boost measurement sensor 18 that has been determined to be malfunctioning even in the high intake flow rate range, and an emergency Fuel injection injector drive pulse signal.

A driving pulse (τL) signal substantially based on the L-J method is output to the injector 12. For the L-J method and D
- Each of the J method pulse calculation circuits 31 and 32 stores in advance a program for determining the fuel injection amount in accordance with the intake air amount or boost and the engine rotation speed in its read-only memory section, Further, the DJ system Levals correction circuit 35 stores in advance a program for correcting the fuel injection injector drive pulse τD in the DJ system in accordance with the pulse difference ΔτD input at each load.

The air flow meter 13 as an intake air flow meter also includes a measuring plate that uses a measuring plate that rotates in response to the dynamic pressure of the intake air flow over the entire load range and generates an output voltage that corresponds to the rotation angle. It is also possible to use a ring plate type air flow meter or a Karman vortex flow meter that utilizes the principle that the number of Karman vortices available on the needle side increases in response to an increase in the intake flow rate.

Next, the operation of this embodiment will be explained based on the flowchart shown in FIG. First, the crank angle detector 24
A command signal to start the calculation is issued by the above command, and when engine starting is confirmed by the solenoid terminal voltage of the starting motor, J, 1. The main fuel injection amount is set, and then the intake air amount signal, engine speed signal, and boost signal are read in the pulse calculation circuits 31 and 32 for [, -j method and DJ method.
Steps ■), ), the L-J method fuel injection injector drive pulse τL is set in the former, and the D-
Fuel injection injector drive pulse τD in J method,
are calculated respectively (steps P,, P,). These driving pulses τL, τD are input to the pulse difference learning circuit 33, where D is calculated using the pulse difference Δ.
Step P4). after that.

The boost measured by the boost measurement sensor 18 is compared with the predetermined pressure B1 (step P,), and if it is larger, it is in the low load range, so the process moves to step P,1.
If it is small, it is a high load area and a judgment zone, so the absolute value of the pulse difference ΔτD is 1ΔτD1.

In the DJ system failure determination circuit 34, it is determined whether or not the value is greater than or equal to a predetermined value A determined experimentally to determine a failure (step P), and if the value is greater than or equal to the predetermined value, a binary signal is sent to the fail flag. 1 is given (step P,),
Further, if it is below the predetermined value AJu, 0 is assigned (step P,). In this embodiment, the drive pulse τL is used to increase failure determination accuracy.

τDo is calculated in a low intake flow rate region. Then, it is determined whether or not the fail flag is set to 1 (step P). If the fail flag is set to 1, that is, the boost measurement sensor as the intake air amount needle at1 means adopted in the D- and J methods. 18 is out of order, fuel injection control is performed using the fuel injection injector drive pulse according to the L-J method in the low intake flow rate range even in the corrected intake flow rate range (steps P, , and '). In addition, if the fail flag is set to 0, that is, the boost measurement sensor 18
When there is no failure, the boost measured by the sensor 18 is compared with a predetermined intake pressure value B, which is determined experimentally as a criterion for determining a high intake flow rate region or a low intake flow rate region (step P1). ). When the intake pressure value is lower than the predetermined intake pressure value B2, that is, when the engine is operating in a low intake flow rate region with medium or low load, the drive pulse using the L-J method
In step 6, fuel injection control is performed on the injector 12 (step P1.). In addition, when the boost is higher than the predetermined intake pressure value B2, that is, when the engine is operating in a high load high intake flow rate region, the drive pulse τD by the D-J method is
, is corrected by the pulse difference ΔτD to perform efficient fuel injection control that is more suited to the operating state of the engine (step P1.). An oxygen concentration detector 21 in the exhaust pipe 20 constantly checks whether fuel injection control is being performed appropriately.

In the above embodiment, a boost measurement sensor is used in the D-J method, but it is also possible to calculate the intake air amount in a high intake flow rate region using a throttle opening detection sensor. It goes without saying that the failure determination routine of the present invention can be applied. Further, as the L-J type air flow meter, a vane type one that operates with intake negative pressure may be used.

(Effects of the Invention) As described above, according to the fuel control device for an electronic fuel injection engine of the present invention, when it is determined that the load detection means has failed, switching between the first and second fuel injection amount calculation means is performed. By controlling the fuel injection based on the output of the first fuel injection amount calculating means which determines the fuel injection amount based on the intake air flow rate and engine speed in the low intake flow rate region as well as in the low intake flow rate region. Effectively prevents damage to the engine and catalytic converter due to incorrect fuel control due to failure of the load detection means in the high intake flow rate range.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of an embodiment of a fuel control device for an electronic fuel injection engine according to the present invention, and FIG. 2 is a block diagram of the fuel control device of the same embodiment. FIG. 3 is a flowchart showing a fuel injection control program in the same embodiment. 10... Engine body, 13... Air flow meter, 14... Throttle valve, 18...
... Boost measurement sensor, 23 ... Engine speed detector, 30 ... Fuel control device, 31.
...Pulse calculation circuit for L-J method, 32...
・・Pulse calculation circuit for D-J method, 34・・・・D−
J method failure determination circuit, 36...pulse selection circuit,
37...Selection cancellation circuit.

Claims (1)

[Claims] (1) An intake air flow rate detection means that is interposed in the intake passage and detects the intake air flow rate supplied to the engine; a load detection means that detects a signal related to the intake negative pressure downstream of the throttle valve or the throttle valve opening; an engine rotation speed detection means for detecting the rotation speed; a first fuel injection amount calculation means for determining a fuel injection amount based on the outputs of the intake air flow rate detection means and the engine rotation speed detection means; the load detection means and the engine; a second fuel injection amount calculation means that determines the fuel injection amount based on the output of the rotation speed detection means; and a second fuel injection amount calculation means that determines the fuel injection amount based on the output of the rotation speed detection means; Based on the above, in the fuel control device for an electronic fuel injection engine having a switching control means for operating the fuel injection valve based on the output of the second fuel injection amount calculation means in a high intake flow rate region equal to or higher than the predetermined value, the load detection is performed. a failure determining means for determining a failure of the means; and a switching canceling means for receiving an output of the failure determining means and canceling the switching of the switching control means to select the first fuel injection amount calculating means regardless of the intake air flow rate. A fuel control device for an electronic fuel injection engine, comprising: