JPH01110859A - Fuel control method at time of pressure sensor trouble - Google Patents

Abstract

PURPOSE:To restrain shock from occurring on account of rapid variation in a fuel injection quantity, by gradually converging a normal intake pressure immediately before the trouble to a pseudo value, and performing fuel injection on the basis of the convergence value in the case of the trouble of a pressure sensor. CONSTITUTION:An electronic controller 6 detects the real trouble of a pressure sensor 7 and as well, it sets a normal intake pressure immediately before the trouble in such a way as to be gradually converged to a pseudo value, and thereat, it sets the pseudo value at a value corresponding to an intake air quantity required for moving a vehicle, when the pressure sensor 7 shifts fuel control under the normal condition to another preliminary fuel control under the troubled condition. And then, the controller determines the intake air quantity and fuel injection quantity for every cycle so as to perform fuel injection till the intake pressure reaches the pseudo value, on the basis of the respective convergence values. Therefore, it is possible to remarkably restrain shock from occurring, following rapid variation in the fuel injection quantity caused by some trouble of the pressure sensor 7 and to surely move the vehicle by a required distance.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention can be suitably applied to an electronically controlled engine configured to detect the amount of intake air into the combustion chamber from the engine speed and intake pressure. This invention relates to a fuel control method when a pressure sensor fails.

[Prior Art] In this type of electronically controlled engine, for example, as a prior art of the present invention, as shown in Japanese Patent Application Laid-Open No. 57-52642, the pressure value when the pressure sensor that detects the intake pressure fails In many cases, a certain pseudo value is set. In the event of a pressure sensor failure, the above pseudo value is used to calculate the intake air amount, which is the basis of the fuel supply amount, to prevent the vehicle from malfunctioning and to ensure that the vehicle can move within the necessary limits. I have to.

[Problems to be Solved by the Invention] However, the above-mentioned pseudo value is often set to a relatively low value that allows the vehicle to move within necessary limits. In most cases, when the detected intake pressure reaches a failure determination value and it is determined that the pressure sensor has failed, it suddenly switches to a pseudo value. Therefore, when the differential pressure between the intake pressure before the failure and the pseudo value is relatively large, such as when the vehicle is accelerating, the calculated intake air amount changes rapidly. As a result, the amount of fuel supplied to the combustion chamber, which is determined according to the amount of intake air, also changes rapidly, and this change causes shocks such as shaking in the vehicle.

In particular, in engines equipped with a supercharger, the fluctuation range of the intake pressure from negative pressure to positive pressure is large, so the above-mentioned problems become noticeable.

In order to prevent such problems, it has been devised that the intake pressure immediately before the failure of the pressure sensor is used as a pseudo value after failure determination, thereby preventing the vehicle from shaking at the time of switching. However, according to this method, if there is a large difference between the intake pressure immediately before the failure and the intake pressure required to move the vehicle, the amount of fuel supplied will be excessive or small compared to the actual amount of intake air. , it may become difficult to drive the vehicle.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel control method when a pressure sensor fails, which can solve the above-mentioned problems without causing such problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention, when a failure of a pressure sensor that detects intake pressure is detected, sets the detected value of the pressure sensor to a pseudo value at the time of failure. In the fuel control method when a pressure sensor malfunctions, which is configured to replace the pressure sensor and adjust the amount of fuel supplied to the combustion chamber, when a malfunction of the pressure sensor is detected, the normal intake pressure before the malfunction is set to the pseudo value. If it is determined that it exceeds the above, a minute intake pressure correction value is calculated from the normal intake pressure before the failure of the pressure sensor at regular intervals or every fuel injection. Fuel injection is performed based on the value subtracted until the value is reached, and if it is determined that the value has not been exceeded, the intake pressure correction value is added to the normal intake pressure before the failure at regular intervals or every fuel injection. The present invention is characterized in that fuel injection is executed based on the value added until a pseudo value is reached.

[Operation] According to this configuration, if it is determined that the normal intake pressure before the failure of the pressure sensor exceeds the pseudo value substituted after the failure, the normal intake pressure before the failure will be changed immediately after the determination. The intake pressure is gradually subtracted by a small intake pressure correction value at every fixed time or every fuel injection until the intake pressure reaches the pseudo value.

On the other hand, if it is determined that the normal intake pressure before the failure of the pressure sensor is less than the pseudo value, immediately after the determination, the normal intake pressure before the failure will be changed at regular intervals or every fuel injection. The atmospheric pressure correction value is added one by one until the pseudo value is reached.

As a result, the amount of fuel supplied to the combustion chamber when switching from the normal fuel control area to the fuel control area when the pressure sensor fails is as follows:
The supply amount gradually changes in accordance with the stepwise corrected intake pressure, and finally changes to the supply amount corresponding to the pseudo value.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a motor vehicle engine with an electronically controlled fuel injection device. The electronically controlled fuel injection device 2 installed in the engine 1 shown in the drawing is of the D-dietronic type, which is configured to calculate the amount of intake air into the combustion chamber 3 from the intake pressure PM and the engine speed. The fuel injection valve 5 includes a fuel injection valve 5 attached to a pipe 4 and an electronic control device 6 that controls the opening time of the fuel injection valve 5. A pressure sensor 7 for detecting the intake pressure PM is provided in a surge tank 9 interposed between the intake pipe 4 and the throttle body 8, and a crank angle sensor 10 for detecting the engine speed is provided in the distributor 11. It is a provision.

The fuel injection valve 5 has a built-in electromagnetic coil, and when an injection signal a is applied from the electronic control device 6 to the electromagnetic coil, an amount of fuel corresponding to the injection signal a is returned from the nozzle at the tip to the intake port. It is designed to be injected into the air.

The electronic control unit 6 includes a central processing unit 12, a storage device 13, input/output interfaces 14, 15, and the like. The input interface 14 includes at least a signal from the pressure sensor t7 and a crank angle sensor 1.
The signal C from 0 is input, and the output interface 1
5 outputs an injection signal a toward the fuel injection valve 5. Then, based on the information input from the pressure sensor 7, it is determined whether the pressure sensor 7 is normal or not. If the pressure sensor 7 is normal, based on the input latest intake pressure PMNEW and engine rotation speed, The intake air amount into the combustion chamber 3 is calculated, and the fuel supply amount for each fuel injection timing is determined based on the calculated intake air amount.

On the other hand, due to a short circuit or disconnection in the circuit connecting the pressure sensor 7 and the electronic control device 6, or an abnormality in the pressure sensor 7 itself,
If the input intake pressure PM is outside the specified upper limit setting value PMf or lower limit setting value, it is determined that the pressure sensor 7 is malfunctioning, and the input intake pressure PM is used as a substitute for the failure of the pressure sensor 7. The engine 1 is controlled by switching to the pseudo value PMo. Note that the pseudo value PMo is set to a value corresponding to the amount of intake air required for movement of the vehicle.

The electronic control device 6 also detects the actual failure of the pressure sensor 7 when the pressure sensor 7 transitions from normal fuel control to preliminary fuel control in the event of a failure.
The normal intake pressure PM immediately before the failure is sequentially converted to the pseudo value P.
It is set to converge to Mo.

To be more specific, the intake pressure PM detected when the pressure sensor 7 fails changes rapidly and reaches the failure judgment value of the pressure sensor 7. 7 actual failure times will intervene. For example, as schematically shown in FIG. 2, a failure occurs in the pressure sensor 7 while the intake pressure PM is rising, and the detected value PM
exceeds the actual intake pressure PMr and suddenly the failure judgment value PM
When f is reached, a failure determination of the pressure sensor 7 is made at the reaching time t1. However, if the actual failure time tn of the pressure sensor 7 is interposed between the intake pressure detection time to immediately before the failure and the failure determination time t1, the failure time tn will not be detected. Therefore, the intake pressure is detected at the time t immediately before the time tn when the intake pressure PM actually suddenly changes, that is, when a failure occurs in the pressure sensor 7.

The intake pressure PMI detected immediately before the failure is determined as the normal intake pressure immediately before the failure, and
and the pseudo value PMo are compared.

If the intake pressure PMI of the pressure sensor 7 immediately before the failure exceeds the pseudo value PMo, then the intake pressure PMI immediately before the failure
A minute intake pressure correction value δPM is subtracted from MI for each fuel injection, and the subtracted value is the pseudo value PM.

The intake air amount and fuel injection amount are determined each time based on the subtracted intake pressure PM until reaching the amount.

On the other hand, if the intake pressure PMI of the pressure sensor 7 immediately before the failure does not exceed the pseudo value PMo, the intake pressure P just before the failure
A minute intake pressure correction value δPH is added to MI for each fuel injection, and the intake air amount and fuel injection amount are adjusted for each injection based on each correction value until the intake pressure PM after addition reaches the pseudo value PMo. I am trying to decide.

In order to execute the above-mentioned control, the electronic control device 6 also has a built-in program as schematically shown in FIG. First, in step 51, it is determined whether the latest intake pressure PMNEW successively inputted from the pressure sensor "7" is a failure judgment value outside the specified value, and if it is determined that it is within the specified value, step 52 is performed. If it is determined that the value is a failure determination value, the process advances to step 53.

In step 52, it is determined whether the amount of change in intake pressure PM within a specified value exceeds a determination value A.

That is, from the latest intake pressure PMNEW to the previous intake pressure P
Absolute value of the value obtained by subtracting MOLD I PMNEW −PM
If it is determined that OLD I does not exceed the determination value A of the amount of change in intake pressure PM, the process proceeds to step 54, and if it is determined that it does, the process proceeds to step 55.

In step 54, the previous intake pressure PMOLD is set to the address PMI for setting the intake pressure PMI immediately before the sudden change in the intake pressure PM, and the process proceeds to step 55.

In step 55, the latest intake pressure PMNEW is set to the address PMINJ for setting the value for fuel injection amount calculation, and the process proceeds to step 62.

In step 53, the intake pressure PMI immediately before the failure is set to a pseudo value P
Value PM obtained by subtracting the intake pressure correction value δPH from Mo.

It is determined whether or not it is larger than -δPM. If it is judged to be larger, the process moves to step 56, and if it is judged to be smaller, the process moves to step 58. In step 56, it is determined whether or not the intake pressure PH1 immediately before the failure is smaller than the value PMo+δPM, which is the sum of the pseudo value PMo and the intake pressure correction value δPH.If it is judged to be small, the process moves to step 57; If it is determined, the process advances to step 58. In step 57, the pseudo value PMo is set to address PMI, and the process moves to step 61.

In step 58, the intake pressure PMI immediately before the failure is set to a pseudo value P
It is determined whether or not it exceeds Mo. If it is determined that it is exceeded, the process proceeds to step 59, and if it is determined that it is not exceeded, the process proceeds to step 60. In step 59, the value PMI-δPH obtained by subtracting the intake pressure correction value δPM from the intake pressure PH1 immediately before the failure is set to the address PMI, and the process proceeds to step 61. In step 60, the intake pressure is set to the intake pressure PM1 immediately before the failure. Value PHI added with correction value δPH
+δPH is set in the address PMI and the process moves to step 61. In step 61, the intake pressure PM immediately before the failure is set to the address PMINJ for setting the value for calculating the fuel injection amount.
Set L and proceed to step 62. In step 62, the intake pressure PMINJ, which is actually used for calculating the injection amount, is set at the address PMOLD, and the process moves to the main routine.

According to such a configuration, when the pressure sensor 7 is normal, the intake air amount to the combustion chamber 3 is calculated based on the latest intake pressure PMNEW and engine rotation speed that are input sequentially, and the calculated intake air amount is The amount of fuel supplied each time is determined according to the amount of air (steps 51 → 52 → 54 → 55
). In this case, if the intake pressure PM suddenly changes within the specified value and the amount of change is within the judgment value A, the previous intake pressure P)IOLD
is updated sequentially, and if it is larger than the judgment value ^, the intake pressure PM
The intake pressure PH1 immediately before the sudden change in the intake pressure PH1 is temporarily held and taken into consideration in the next injection amount calculation.

On the other hand, due to a failure of the pressure sensor 7, the intake pressure PM suddenly changes outside the specified value, and the normal intake pressure PMI immediately before the failure becomes the value PMo-δ obtained by subtracting the intake pressure correction value δPM from the pseudo value PMo.
PH and pseudo value opening. The value PM that is obtained by adding the intake pressure correction value δ state to
o+δPH, the intake air amount and fuel supply amount are calculated using the pseudo value PMo immediately after the failure determination (steps 51→53→56→57).
→61).

In addition, the normal intake pressure PMI immediately before the failure of the pressure sensor 7 is a value P obtained by subtracting the intake pressure correction value δPH from the pseudo value PMo.
Mo-δPH and pseudo value PM. If the value PMo+64 is the sum of the intake pressure correction value δPH and the intake pressure PMI, control is performed to gradually converge the intake pressure PMI to the pseudo value PMo. That is, if the intake pressure PMI immediately before the failure is larger than the pseudo value PMo, the intake pressure correction value δPM is subtracted from the intake pressure PMI immediately before the failure at each injection amount calculation time, and the subtracted intake pressure PM becomes the pseudo value PMo. The intake air amount and fuel injection amount are determined based on the gradually changed intake pressure PM until reaching the value PMo (step 51).
-53 (-5[3)58→59→61). If the intake pressure PMI immediately before the failure is smaller than the pseudo value PMo, the intake pressure correction value δPM is added to the intake pressure PMI immediately before the failure at each injection amount calculation time, and the added intake pressure P
The intake pressure PM is gradually changed until M reaches the pseudo value PHO.
Based on this, the intake air amount and fuel injection amount are determined (steps 51→53 (→5B) 58→6
0 → 61).

Note that the above control is repeatedly performed while the engine 1 is operating.

Therefore, according to such a configuration, during the transition period from the normal fuel control executed when the pressure sensor 7 is normal to the preliminary fuel control in the event of a failure, the intake pressure increases by a minute value δPM. Since it changes gradually, the amount of fuel supplied to the combustion chamber 3 determined according to the intake pressure PM also changes gradually, and finally becomes a pseudo value PM.

The amount of fuel supplied will shift to correspond to the amount of fuel supplied. As a result, even if a failure of the pressure sensor 7 is detected, such as during acceleration when the differential pressure between the intake pressure PMI immediately before the failure of the pressure sensor 7 and the pseudo value PMo is large, the amount of fuel supplied to the combustion chamber 3 will suddenly decrease. Since it does not change, the shock when switching to fuel control when the pressure sensor fails can be greatly alleviated.

In addition, in the above embodiment, the intake pressure immediately before the failure of the pressure sensor was changed for each fuel injection, but the intake pressure immediately before the failure was changed at regular intervals to reach a pseudo value. Good too.

[Effects of the Invention] As described above, in the present invention, when switching from normal fuel control to fuel control in the event of a pressure sensor failure, the amount of fuel supplied to the combustion chamber is gradually changed and the amount of fuel supplied to the combustion chamber is finally changed to a pseudo value. Since we are trying to converge to the fuel supply amount corresponding to
A highly reliable fuel control method in the event of a pressure sensor failure that can significantly suppress the shock that occurs due to a sudden change in fuel supply due to a pressure sensor failure, and ensure that the vehicle can move within the required limits. can be provided.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being an explanatory diagram of the system, FIG. 2 being a diagram showing control setting conditions, and FIG. 3 being a flowchart showing the control procedure. 2...Electronically controlled fuel injection device 3...Combustion chamber 6...Electronic control device 7...Pressure sensor PMI...Intake pressure just before failure PMo...pseudo value PMr...actual Intake pressure δPM... Intake pressure correction value to... At the time of intake pressure detection immediately before failure t1... At the time of failure determination tn... At the time of pressure sensor failure

Claims (1)

[Claims] When a pressure sensor that detects intake pressure is detected to have failed, the pressure sensor is configured to replace the detected value of the pressure sensor with a pseudo value at the time of failure and adjust the amount of fuel supplied to the combustion chamber. In the fuel control method, when a failure of the pressure sensor is detected, it is determined whether the normal intake pressure before the failure exceeds the pseudo value, and if it is determined that the normal intake pressure exceeds the pseudo value, the Fuel injection is performed based on the value obtained by subtracting a small intake pressure correction value from the normal intake pressure before the failure of the pressure sensor at regular intervals or every fuel injection until the pseudo value is reached, and it is determined that the intake pressure has not exceeded the value. In this case, the fuel injection is performed based on the value obtained by adding the intake pressure correction value to the normal intake pressure before the failure at regular intervals or every fuel injection until the pseudo value is reached. A fuel control method in the event of a pressure sensor failure.