JPH06100123B2 - Failure determination device in fuel supply device of internal combustion engine for vehicle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a sensor failure determination device for detecting the concentration of a mixed fuel in which methyl alcohol or the like is mixed in gasoline.

<Prior Art> As a fuel supply device for an internal combustion engine of this type, there is the following one (see JP-A-56-98540).

That is, the detected engine speed N and intake air flow rate Q
Based on and, the basic injection amount T _P (= KQ / N: K is a constant) is calculated. Then, the calculated basic injection amount T _P is adjusted to various correction coefficients COEF based on the water temperature, the air-fuel ratio feedback correction coefficient α based on the detection value of the oxygen sensor that detects the oxygen concentration in the exhaust gas, and the alcohol concentration in the mixed fuel. a density correction coefficient K _MET by the detection value of the alcohol concentration sensor of an electrostatic capacitance type for detecting a voltage correction amount T _S by the battery voltage,
The fuel injection amount T _i (= T _P × COEF ×
Calculate α × K _MET + T _S ).

Then, an injection pulse signal corresponding to the fuel injection amount T _i is output to the fuel injection valve to supply the fuel to the engine.

<Problems to be Solved by the Invention> However, in such a conventional fuel supply device, the basic injection amount T _P is corrected based on the detection value of the alcohol concentration sensor to calculate the fuel injection amount T _i. Therefore, if the alcohol concentration sensor fails, the air-fuel ratio changes abruptly, making it impossible to operate the vehicle, and giving the driver a discomfort. In particular, the concentration correction coefficient K _MET changes from 1 to _1.94, so if the alcohol concentration sensor fails, the air-fuel ratio changes greatly.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a failure determination device capable of highly accurately determining a failure of the concentration detecting means.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention supplies a mixed fuel, which is a mixture of two types of fuel, to an engine, and the fuel supply is based on the engine operating state. Fuel supply amount setting means A for setting the amount, concentration detection means B for detecting one fuel concentration in the mixed fuel, and fuel for correcting the set fuel supply amount based on the detected fuel concentration The supply amount correcting means C, the air-fuel ratio detecting means D for detecting the actual air-fuel ratio of the engine, and the actual air-fuel ratio based on the detected actual air-fuel ratio so that the actual air-fuel ratio becomes the target air-fuel ratio in a predetermined operating range. The corrected fuel supply amount is corrected by the air-fuel ratio feedback correction amount, while the air-fuel ratio feedback control means E that holds the air-fuel ratio feedback correction amount fixed at a predetermined value under a predetermined engine operating condition, and the corrected fuel Drive control means G for controlling the drive of the fuel supply means F based on the amount of fuel supply
A shift position detecting means H for detecting a shift position of the transmission, a vehicle speed detecting means I for detecting a vehicle speed, and a load detecting means J for detecting an actual engine load.
And a target engine load setting means K for setting a target engine load based on the detected shift position and vehicle speed when the air-fuel ratio feedback correction amount is fixedly held at a predetermined value, and the set target. And a determination unit L that determines that the concentration detection unit B has failed when the detected actual engine load differs from the engine load by a predetermined value or more.

<Operation> In this way, the target engine load is set from the shift position and the vehicle speed, and the target engine load and the actual engine load (for example, required for combustion in one cycle of one cylinder obtained from the engine speed and the intake air amount) The failure of the concentration detecting means is determined with high accuracy from the basic injection amount).

<Examples> The present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, the control device 1 including a microcomputer includes a signal from the crank angle sensor 2 (corresponding to the rotation speed), an intake air flow rate signal from the air flow meter 3, and a vehicle speed sensor as vehicle speed detecting means. 4 from the vehicle speed signal, the oxygen concentration signal in the exhaust gas from the oxygen sensor 5 as the air-fuel ratio detecting means, and the alcohol from the alcohol concentration sensor 6 as the concentration detecting means provided in the fuel supply passage (not shown). The density signal and are input.

The control device 1 operates according to the flowchart of FIG. 3 and determines whether or not the alcohol concentration sensor 6 has a failure.

Here, the control device 1 constitutes fuel supply amount correction means, air-fuel ratio feedback control means, target engine load setting means, load detection means, and determination means. Further, the control device 1 and the drive circuit 8 constitute drive control means. The crank angle sensor 2 and the vehicle speed sensor 4 form a shift position detecting means.

Next, the operation will be described with reference to the flowchart of FIG.

First, the fuel injection control will be described. The crank angle sensor 2
Engine speed N and air flow meter 3 detected by
The basic injection amount T _P is calculated in the same manner as in the conventional example based on the intake air flow rate Q detected by. Then, the calculated basic injection amount T _{P is set} to various correction factors COEF based on the water temperature and the like.
And the air-fuel ratio feedback correction coefficient α based on the detection value from the oxygen sensor 5, the concentration correction coefficient K _MET based on the detection value from the alcohol concentration sensor 6, and the voltage correction amount T _S based on the battery voltage, Fuel injection amount T _i (=
T _P × COEF × α × K _MET + T _S ) is calculated in the same manner as in the conventional example.

Then, the injection pulse signal corresponding to the calculated fuel injection amount T _i is output to the fuel injection valve 7 as the fuel supply means via the drive circuit 8 to supply the fuel to the engine. In this way, the air-fuel ratio feedback control is performed based on the oxygen concentration in the exhaust gas detected by the oxygen sensor 5 so that the air-fuel ratio becomes a predetermined air-fuel ratio (for example, λ = 1). During such air-fuel ratio feedback control, for example, when the state in which the air-fuel ratio deviates from the target air-fuel ratio to the lean side or the rich side by a predetermined value (for example, ± 25%) or more continues for a predetermined time (for example, 3 seconds),
By fixing and holding the air-fuel ratio feedback correction coefficient α at a constant value (for example, 1) regardless of the value detected by the oxygen sensor 5, the air-fuel ratio is clamped near the target air-fuel ratio (hereinafter, referred to as a clamp for air-fuel ratio feedback control. I call it).

During such fuel injection control, the routine shown in the flowchart of FIG. 3 is executed.

That is, in S1, it is determined whether or not the alcohol concentration sensor 6 is currently determined to be defective. If YES, the routine is ended, and if NO, the process proceeds to S2.

In S2, it is determined whether or not the air-fuel ratio feedback control based on the detection value of the oxygen sensor 5 is being performed. If YES, the process proceeds to S3, where N
When O, terminate the routine.

In S3, the current shift position of the transmission determined based on the engine rotation speed detected by the crank angle sensor 2 and the vehicle speed detected by the vehicle speed sensor 4 is Top (for example, 4
It is determined whether or not it is a speed stage. If YES, the process proceeds to S4, and if NO, the routine ends.

In S4, it is determined whether or not the current operating state is a steady operating state. If YES, the process proceeds to S5, and if NO, the routine ends. The determination of the steady operation state is made when the engine speed is within an allowable range of 50 _rpm or less for 3 seconds and the engine load such as the basic injection amount T _P is within a permissible range of 50 _mmHg corresponding to negative pressure. Then, it is determined that the operation is in steady operation.

After the determination of the steady operation state is performed in this way, or during the determination, the following control is performed.

That is, in S5, it is determined whether or not the air-fuel ratio feedback control is clamped, and if YES, the process proceeds to S6 and NO
When, the routine is ended.

In S6, the maximum allowable basic injection amount T _PMAX and the minimum allowable basic injection amount T _PMIN are searched from the table based on the vehicle speed detected by the vehicle speed sensor 4 and interpolation calculation is performed. Specifically, the maximum permissible basic injection amount T _PMAX and the minimum permissible basic injection amount T _iMIN are assigned to the table in a stepwise manner in correspondence with the set vehicle speed and stored. Then, the maximum allowable basic injection quantity T _PMAX corresponding to the actual vehicle speed below the set vehicle speed, the maximum permissible basic injection quantity T _PMAX corresponding to the set vehicle speed exceeding the actual vehicle speed
Is calculated by interpolation to obtain the maximum allowable basic injection amount T _PMAX corresponding to the actual vehicle speed. The minimum allowable basic injection amount T _PMIN is similarly obtained by interpolation calculation. Here, the maximum allowable basic injection amount T _PMAX and the minimum allowable basic injection amount T _PMIN are target engine loads.

In S7, it is determined whether or not the current basic injection amount T _P is between the maximum allowable basic injection amount T _PMAX and the minimum allowable basic injection amount T _PMIN obtained in S6, and if YES, the routine ends. If NO, it is determined that the alcohol concentration sensor 6 is out of order, and the process proceeds to S8.

In S8, 1 is added to the failure determination number of the alcohol concentration sensor 6 to count up, and the process proceeds to S9.

The count-up under the same operating condition will be accepted up to twice. This same operating condition is ± 5km / h at vehicle speed
Is the range.

In S9, it is determined whether or not the number of failure determinations counted in S8 is a predetermined value (a value of 3 or more) or more. If YES, the process proceeds to S10, and if NO, the routine ends.

In S10, it is determined that the alcohol concentration sensor 6 has failed.
Then, the driver is warned of the determination of this failure by a display or a horn.

If the alcohol concentration sensor fails, the fuel injection amount T obtained by correcting the basic injection amount T _P based on the detected alcohol concentration value
_i becomes an abnormal value. Therefore, the engine output becomes too large or too small. In order to correct this, the driver operates the throttle valve, so the intake air amount changes. When the intake air amount Q changes, T _P changes. As described above, when the alcohol concentration sensor 6 malfunctions and an abnormal value is output, the basic injection amount T _P changes greatly. Therefore, by comparing the basic injection amount T _P with the set value, the abnormality of the alcohol concentration sensor is detected. it can.

As described above, during the clamp of the air-fuel ratio feedback setting, the maximum allowable basic injection amount T _PMAX and the minimum allowable basic injection amount T _PMIN are searched in correspondence with the shift position and the vehicle speed,
Since the failure of the alcohol concentration sensor 6 is determined when the actual basic injection amount T _P is not allowed between them, the presence or absence of the failure of the alcohol concentration sensor 6 can be determined with high accuracy, and thus the engine The deterioration of drivability can be suppressed.

The target engine load corresponding to the vehicle speed may be set for each shift position.

<Effects of the Invention> As described above, the present invention compares the target engine load set from the shift position and the vehicle speed with the actual engine load to determine the failure of the concentration detecting means. The failure of the concentration detecting means can be determined with high accuracy, and deterioration of the drivability of the engine can be suppressed.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 3 is a flowchart of the same. 1 ... Control device, 2 ... Crank angle sensor, 3 ... Air flow meter, 4 ... Vehicle speed sensor, 5 ... Oxygen sensor, 6 ... Alcohol concentration sensor, 7 ... Fuel injection valve,
8 ... Driving circuit

Claims (1)

[Claims] 1. A fuel supply amount setting means for supplying a fuel mixture, which is a mixture of two kinds of fuel, to an engine, and a fuel supply amount setting means for setting a fuel supply amount based on an engine operating state. Concentration detecting means for detecting a fuel concentration, fuel supply amount correcting means for correcting the set fuel supply amount based on the detected fuel concentration, and air-fuel ratio detecting means for detecting an actual air-fuel ratio of the engine. , The corrected fuel supply amount is corrected by the air-fuel ratio feedback correction amount so that the actual air-fuel ratio becomes the target air-fuel ratio in the predetermined operating region based on the detected actual air-fuel ratio, while the predetermined engine operating conditions And an air-fuel ratio feedback control means for fixing and holding the air-fuel ratio feedback correction quantity at a predetermined value, and a drive control means for drivingly controlling the fuel supply means based on the corrected fuel supply quantity. In a fuel supply device for an internal combustion engine for a vehicle, a shift position detecting means for detecting a shift position of a transmission, a vehicle speed detecting means for detecting a vehicle speed, a load detecting means for detecting an actual engine load, and the air-fuel ratio feedback Target engine load setting means for setting a target engine load based on the detected shift position and vehicle speed when the correction amount is fixedly held at a predetermined value, and the target engine load setting means for detecting the set target engine load. And a determination unit that determines that the concentration detection unit has a failure when the actual engine load differs by a predetermined value or more.