JPH0689700B2 - Fuel injection valve diagnostic device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fuel injection valve diagnostic device for diagnosing clogging of a fuel injection valve provided for each cylinder in an engine intake passage.

<Prior Art> In an electronically controlled fuel injection device for an internal combustion engine, an electromagnetic fuel injection valve is provided for each cylinder in an engine intake passage, and a fuel is supplied by a drive pulse signal from a control unit to open the fuel. Is being supplied by injection.

The control of the fuel injection amount is based on the intake air flow rate Q and the engine speed N, which are state quantities related to the amount of air taken into the engine.
While calculating the basic fuel injection amount Tp = K · Q / N (K is a constant), the air-fuel ratio feedback correction coefficient α is set based on the signal from the oxygen sensor provided in the engine exhaust system, and is corrected by this. As a result, the final fuel injection amount Ti = Tp
This is performed by calculating α and applying a drive pulse signal having a pulse width corresponding to this to each fuel injection valve at the same timing as the intake stroke of the cylinder.

By the way, when an abnormality occurs in the fuel injection valve, it is necessary to promptly detect this.

As a conventional method for diagnosing a fuel injection valve abnormality, there have been the following methods.

The air-fuel ratio is detected during fuel cut to detect a leak in the fuel injection valve.

The leak of the fuel injection valve is detected by comparing the air-fuel ratios of the two regions.

Disconnection is detected by comparing the output of the CPU and the ON / OFF output of the fuel injection valve.

<Problems to be Solved by the Invention> However, this is a diagnosis of a failure or disconnection on the leak side, and there is a problem that an abnormality due to clogging of the fuel injection valve cannot be detected.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel shift valve diagnostic device capable of diagnosing clogging of a fuel injection valve.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention provides an internal combustion engine including a fuel injection valve for each cylinder in an engine intake passage,
A basic fuel injection amount calculation means for calculating a basic fuel injection amount based on a state amount related to the amount of air taken into the engine, and a rich / lean air-fuel ratio based on a signal from an oxygen sensor provided in the engine exhaust system. And the air-fuel ratio feedback correction coefficient setting means for increasing / decreasing the air-fuel ratio feedback correction coefficient according to the judgment result, and the fuel to be instructed to each fuel injection valve by multiplying the basic fuel injection amount by the air-fuel ratio feedback correction coefficient at that time. In the fuel injection valve diagnosis device including the fuel injection amount calculation means for calculating the injection amount, the following means (a) to (c) are provided to configure the fuel injection valve diagnostic device.

(A) Fixed switching means for sequentially setting the fuel injection amount of the fuel injection valve of one cylinder to a value obtained by fixing the air-fuel ratio feedback correction coefficient to a predetermined value under predetermined diagnostic conditions (b) The fixed switching When the fuel injection amount of one cylinder is set to a value obtained by fixing the air-fuel ratio feedback correction coefficient to a predetermined value, the air-fuel ratio feedback correction coefficient set by the air-fuel ratio feedback correction coefficient setting means is stored. Air-fuel ratio feedback correction coefficient storage means (c) Comparison determination means for comparing the feedback correction coefficients stored each time in the storage means to determine whether or not there is an abnormality in each fuel injection valve. It is good to provide.

(D) Correction means for correcting the fuel injection amount instructed to the fuel injection valve of the cylinder determined to be abnormal by the comparison / determination means <Operation> The basic fuel injection amount is Tp, the air-fuel ratio feedback correction coefficient is α, and the fuel injection is performed. The operation will be described in the case of four cylinders with the amount Ti = Tp · α.

At the time of diagnosis, first, the fuel injection amount instructed to the fuel injection valve of the # 1 cylinder is set to Ti = Tp · α ₀ (where α ₀ is a predetermined value), and the fuel injection amount instructed to the fuel injection valve of the other cylinder is Ti = Tp · α. Then, the air-fuel ratio feedback correction coefficient α at this time is stored as α ₁ .

Next, the fuel injection amount instructed to the fuel injection valve of the # 2 cylinder is Ti =
Tp · α _0, and the fuel injection amount instructed to the fuel injection valve of another cylinder is Ti = Tp · α. Then, the air-fuel ratio feedback correction coefficient α at this time is stored as α ₂ .

Next, the fuel injection amount instructed to the fuel injection valve of the # 3 cylinder is Ti =
Tp · α _0, and the fuel injection amount instructed to the fuel injection valve of another cylinder is Ti = Tp · α. Then, the air-fuel ratio feedback correction coefficient α at this time is stored as α ₃ .

Next, the fuel injection amount instructed to the fuel injection valve of the # 4 cylinder is Ti =
Tp · α _0, and the fuel injection amount instructed to the fuel injection valve of another cylinder is Ti = Tp · α. Then, the air-fuel ratio feedback correction coefficient α at this time is stored as α ₄ .

Then, α _{1 to} α ₄ are compared.

Here, if each fuel injection valve is normal, when the air-fuel ratio feedback correction coefficient of each cylinder is fixed, the air-fuel ratio feedback correction coefficient α is set to be compensated by the other three cylinders of the air-fuel ratio feedback portion F of the fixed cylinder. Changes only by an amount corresponding to F / 3, and there is no significant change in α _{1 to} α ₄ .

However, if the # 1 cylinder is clogged, the air-fuel ratio feedback correction coefficient α is set to X / 3 from the beginning in order to supplement the injection amount X (>> F) of the # 1 cylinder with the other three cylinders.
Is increased by an amount equivalent to, and the injection amount of the # 1 cylinder is Ti = Tp
・ Even if fixed to α ₀ , the injection amount of the # 1 cylinder does not substantially change, so the air-fuel ratio feedback correction coefficient α is X / 3.
Is increased by the amount corresponding to, and becomes α ₁ .

On the other hand, if any of the # 2 to # 4 cylinders is fixed, for example, if the injection amount of the # 2 cylinder is fixed to Ti = Tp · α ₀ ,
It is necessary to supplement X / 3 of the burden of the two cylinders with the other # 3 and # 4 cylinders, and the air-fuel ratio feedback correction coefficient α is increased to the amount corresponding to X / 2, which becomes α _2. . α
_{The same} applies to ₃ and α ₄ .

Therefore, when the # 1 cylinder is clogged, α ₁ has a smaller value than α _{2 to} α ₄ and can be detected by comparing these.

For the cylinder in which the clogging of the fuel injection valve is detected in this way, it is advisable to add a special correction to the fuel injection amount instructed to the fuel injection valve.

<Examples> Examples of the present invention will be described below.

Referring to FIG. 2, in the intake passage 2 of the engine 1 (4 cylinders), electromagnetic fuel injection valves 11 to 14 are provided for each cylinder.
A drive pulse signal output for each cylinder from the control unit 3 with a built-in microcomputer is energized to open the valve, and fuel is injected and supplied.

A signal from the air flow meter 4 and a signal from the crank angle sensor 5 are input to the control unit 3.

Further, an oxygen sensor 7 is provided at the collecting portion of the exhaust passage 6 or at the downstream thereof. These oxygen sensors 7 are for detecting the air-fuel ratio of the air-fuel mixture drawn into the engine 1 via the oxygen concentration in the exhaust gas, and the output thereof is input to the control unit 3.

The control and diagnosis of fuel injection are performed by the microcomputer in the control unit 3 according to the flowcharts of FIGS.

FIG. 3 is a fuel injection control routine.

In step 1 (indicated as S1 in the figure, and so on)
Based on a signal from the air flow meter 4, the intake air flow rate Q
The engine speed N is detected based on the signal from the crank angle sensor 5.

In step 2, the basic fuel injection amount Tp = K · Q / N (K is a constant) is calculated from the intake air flow rate Q and the engine speed N. This portion corresponds to the basic fuel injection amount calculation means.

In step 3, the correction coefficient α is set which is set by the routine shown in FIG. 4 which will be described later.

In step 4, it is judged whether or not the abnormality flag is set,
In step 5, it is determined whether the fixed flag is set.

Normally, the abnormality flag = 0 and the fixed flag = 0, so the process proceeds to step 8.

In step 8, the basic fuel injection amount Tp is multiplied by the air-fuel ratio feedback correction coefficient α to calculate the fuel injection amount Ti = Tp · α. This portion corresponds to the fuel injection amount calculation means.

When the fuel injection amount Ti is calculated, a drive pulse signal having a pulse width corresponding to Ti is output at a predetermined timing to the fuel injection valve of the cylinder in the intake stroke of the fuel injection valves 11 to 14. Inject fuel.

FIG. 4 is an air-fuel ratio feedback correction coefficient setting routine, which is executed every predetermined time. This routine corresponds to the air-fuel ratio feedback correction coefficient setting means.

In step 11, the output voltage of the O ₂ sensor 7 is read.

In step 12, the output voltage is compared with the slice level voltage to determine rich / lean of the air-fuel ratio.

In the case of rich, the routine proceeds to step 13, where it is judged whether or not it is the first inversion from lean to rich, and in the case of the first inversion, in step 14, the air-fuel ratio feedback correction coefficient α is decreased by a predetermined proportional amount P. Step 15 if not the first flip
Then, the air-fuel ratio feedback correction coefficient α is set to a predetermined integral amount ΔI.
Reduce.

In the case of lean, the routine proceeds to step 16, where it is judged whether or not it is the first inversion from rich to lean, and in the case of the first inversion, in step 17, the air-fuel ratio feedback correction coefficient α is increased by a predetermined proportional amount P. Step 18 if not the first flip
Then, the air-fuel ratio feedback correction coefficient α is set to a predetermined integral amount ΔI.
Increase.

FIG. 5 shows a diagnostic routine.

In step 21, it is judged whether or not the condition is a predetermined diagnosis condition. Here, the diagnosis condition is, for example, a predetermined region divided by the engine speed N and the basic fuel injection amount Tp, and when an abnormality has elapsed for a predetermined time.

In step 22, i is set to 1, and steps 23 and 24 are first executed for the # 1 cylinder.

In step 23, the fixed flag is set for the # 1 cylinder.

Then, in the routine of FIG. 3, the routine proceeds from step 5 to step 6, and when the injection timing of the fixed cylinder # 1 is reached, the routine proceeds to step 9 to set the fuel injection amount Ti = Tp. In other words, α = 1 (predetermined value).

Thus, the air-fuel ratio feedback correction coefficient α for the # 1 cylinder
Is fixed to a predetermined value 1.

In step 24, the air-fuel ratio feedback control is continued only in the other cylinders in the # 1 cylinder fixed state, the average air-fuel ratio feedback correction coefficient is detected, and this is set to α ₁ .

In this case, a plurality of average values from the peak to the peak of the air-fuel ratio feedback correction coefficient α are sampled, and the average value of these sampling values is used.

Next, in step 25, it is determined whether i = 4. If not,
By incrementing i by 1 in step 26 and returning to step 23, steps 23 to 24 are sequentially executed for cylinders # 2 to # ₄ to obtain α _{2 to} α ₄ .

Here, the part of step 23 corresponds to the fixed switching means, and the part of step 24 corresponds to the air-fuel ratio feedback correction coefficient storage means.

When α _{1 to} α ₄ are stored, the routine proceeds to step 27, where the average value α _AVE (see the following equation) is calculated.

α _AVE = (α ₁ + α ₂ + α ₃ + α ₄ ) / 4 Next, steps 28 to 32 are executed.

In step 28, i is set to 1, and step 29 is first executed for the # 1 cylinder.

In step 29, the absolute value of the difference between α _AVE and α ₁ is compared with a predetermined value.
The abnormality flag is set for one cylinder.

If α ₁ is smaller than α _AVE by a predetermined value or more,
If α ₁ is larger than α _AVE by a predetermined value or more, it can be diagnosed as a leak.

Next, in step 31, it is determined whether i = 4. If not,
By incrementing i by 1 in step 32 and returning to step 29, step 29 is sequentially executed for the # 2 to # 4 cylinders to perform diagnosis.

Here, the portions of steps 29 and 30 correspond to the comparison / determination means.

Further, for example, if the abnormality flag is set for the # 1 cylinder, then, in the routine of FIG. 3, the process proceeds from step 4 to step 7, and if the injection timing of the abnormal cylinder # 1 is reached, further steps are performed. proceed to 10, a fuel injection quantity _{Ti = Tp · α · α K} . α _K is a correction coefficient and is set to increase in the case of, and decrease in the case of leak. This portion corresponds to the correction means.

<Effects of the Invention> As described above, according to the present invention, it is possible to diagnose an abnormality due to the clogging of the fuel injection valve, and to improve the self-diagnosis ability.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the present invention, and FIGS. 3 to 5 are flowcharts. 1 ... Engine, 2 ... Intake passage, 3 ... Control unit, 4 ... Air flow meter, 5 ... Crank angle sensor, 6 ... Exhaust passage, 7 ... Oxygen sensor

Claims (2)

[Claims] 1. An internal combustion engine having a fuel injection valve for each cylinder in an engine intake passage, and a basic fuel injection amount calculation for calculating a basic fuel injection amount based on a state amount related to an amount of air taken into the engine. Means, and an air-fuel ratio feedback correction coefficient setting means for determining the rich / lean of the air-fuel ratio based on a signal from an oxygen sensor provided in the engine exhaust system, and increasing / decreasing the air-fuel ratio feedback correction coefficient according to the determination result, and the basic fuel. A fuel injection amount calculation means for calculating the fuel injection amount instructed to each fuel injection valve by multiplying the injection amount by the air-fuel ratio feedback correction coefficient at that time. Fixed switching means for setting the fuel injection amount of the fuel injection valve of one cylinder to a value obtained by fixing the air-fuel ratio feedback correction coefficient to a predetermined value, and one fixed switching means When the fuel injection amount is set to a value obtained by fixing the air-fuel ratio feedback correction coefficient to a predetermined value, the air-fuel ratio feedback correction stores the air-fuel ratio feedback correction coefficient set by the air-fuel ratio feedback correction coefficient setting means. A fuel injection valve diagnostic device, comprising: coefficient storage means; and comparison determination means for comparing the air-fuel ratio feedback correction coefficients stored in the storage means each time to determine whether or not there is an abnormality in each fuel injection valve. 2. The fuel injection valve diagnostic device according to claim 1, further comprising correction means for correcting the fuel injection amount instructing the fuel injection valve of the cylinder determined to be abnormal by the comparison determination means.