JPH02301641A - Fail-safe device in internal combustion engine control device - Google Patents

Abstract

PURPOSE:To enhance fail-safe characteristic by correcting the opening area of an engine intake system, when failure is caused due to the disconnection of the piping leading to an intake pressure sensor, as much as the amount, and by setting an engine control quantity on the basis of the engine rotating speed. CONSTITUTION:A failure detecting means detects the failure of an intake pressure detecting means while dividing it into two cases, one due to the disconnection of connecting piping to an intake passage and the other. If the failure other than the disconnection of piping is detected, an in-case-of-failure control means outputs an engine control quantity being determined by an in-case-failure engine control quantity setting means to a control means on the basis of the opening area of the intake system and the engine rotating speed, which are detected by respective detecting means. On the other hand, when the disconnection of a piping is detected, the opening area of the intake system detected by an opening area detecting means is corrected by an opening area correcting means as much as the amount of disconnection of the piping, and an in-case-of-failure engine control quantity is determined on the basis of the corrected opening area to output it to the control means. Thus, fail-safe characteristic at the time of intake pressure sensor failure can be enhanced.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a fail-safe device in a control device for an internal combustion engine, and more specifically, to a fail-safe device in a control device for an internal combustion engine. This invention relates to improving fail-safe control in the case of failure of a sensor that detects intake pressure in a door device.

<Prior art> As a control device for an internal combustion engine, a sensor for detecting an intake pressure PB is provided, and the intake pressure P detected by the intake pressure sensor is
A fuel supply control device that controls fuel supply by setting a basic fuel supply amount based on B and the engine rotational speed detected from a crank angle sensor, etc. is widely known as the D-JETRO system. (Refer to JP-A-58-1.50040, etc.).

(Problems to be Solved by the Invention) By the way, in the D-JETRO type fuel supply control device described above, if the sensor that detects the intake pressure PB fails, desired fuel control cannot be performed. It had fail-safe control.

In other words, if the value detected by the intake pressure sensor becomes an abnormal value and a failure of the sensor is detected, setting the fuel supply amount based on the value detected by the intake pressure sensor is prohibited, and instead, detection is performed using the throttle valve opening, etc. The fuel supply amount is set based on the opening area of the engine intake system and the engine rotational speed, and the fuel supply is controlled based on this fuel supply amount for failure.

However, if the failure of the intake pressure sensor is due to a break in the signal line, etc., it is possible to perform the desired fail-safe control using the fail-safe control described above, but if the piping that leads the intake pressure to the intake pressure sensor is disconnected, the sensor cannot detect the sensor. If the value becomes abnormal, the increase in the opening area of the intake system due to this piping disconnection will not be included in the fuel supply amount in case of failure, so the fuel supply amount during fail-safe control will be lower than the engine required amount. There was a problem in that the air-fuel ratio became lean and the engine became unstable.

Furthermore, in a configuration in which the engine ignition timing is variably set and controlled based on the intake pressure (or the basic fuel supply amount based on the intake pressure) and the engine rotation speed, the intake In the event of a pressure sensor failure, fail-safe control is performed in which the ignition timing is set using parameters such as engine volumetric efficiency based on the opening area and engine speed instead of intake pressure. If the failure is due to a pipe being dislocated, there is a problem in that desired ignition timing control cannot be performed.

The present invention has been made in view of the above-mentioned problems, and is provided in a control device in which engine control variables such as fuel supply amount and ignition timing are set and controlled based on detected values of intake pressure. It is an object of the present invention to enable fail-safe control based on the opening area of an intake system to be performed with high accuracy even if the problem is caused by a disconnection of piping.

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. 1, an intake pressure detection means is provided which is connected to the intake passage downstream of the intake throttle valve via piping and detects the intake pressure of the engine. , an engine control amount setting means for setting the engine control wJI based on the intake pressure detected by the intake pressure detection means; and a control means for controlling the engine based on the engine control amount set by the engine control amount setting means. A control device for an internal combustion engine configured to include a failure detection means for detecting a failure of the intake pressure detection means by distinguishing between a disconnection of piping connected to the intake passage and other failures, and a variable control system. An opening area detection means for detecting the opening area of the engine intake system, an engine rotational speed detection means for detecting the engine rotational speed, and a failure detection means detect the opening area of the engine intake system due to the piping displacement when the piping is detected by the failure detection means. an opening area correction means for correcting and setting the opening area by adding the increased amount to the opening area detected by the opening area detection means; and a failure time engine control amount for setting an engine control amount for failure based on the opening area and the engine rotational speed. failure detection means for controlling the engine based on the failure engine control amount with priority over the control means when a failure of the intake pressure detection means is detected by the failure detection means; The fail-safe device is configured by including the following.

In the control device for an internal combustion engine according to the present invention, the intake pressure detection means is connected to the intake passage downstream of the intake throttle valve via piping to detect the intake pressure of the engine, and the engine control amount setting means The engine control amount is set based on the detected intake pressure value. The control means controls the engine based on an engine control amount corresponding to the intake pressure.

Here, in the fail-safe device of the present invention, the failure detection means detects failure of the intake pressure detection means by distinguishing between disconnection of piping connected to the intake passage and other failures, and the opening area detection means detects the opening area of the engine intake system which is variably controlled, and furthermore, the engine rotational speed detection means detects the rotational speed of the engine.

The opening area correction means calculates the opening area by adding an increase in the opening area of the engine intake system due to the piping deviation to the opening area detected by the opening area detection means when the piping is detected by the failure detection means. Correction settings are made to compensate for the increase due to piping misalignment that is not detected by the opening area detection means. The engine control lII setting means for failure is based on the opening area detected by the opening area detection means or the opening area corrected by the piping displacement by the opening area correction means, and the engine rotation speed. Set engine control amount.

The failure control means controls the engine based on the failure engine control amount with priority over the control means when the failure detection means detects a failure of the intake pressure detection means. Therefore, when a failure other than a pipe disconnection is detected, the engine control amount is set based on the opening area detected by the opening area detection means and the engine rotational speed, and when the piping of the intake pressure detection means is disconnected, The setting control of the engine control amount is performed based on the opening area and the engine rotation speed, taking into account the increase in the opening area due to the disconnection of the piping.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing the system configuration of one embodiment, an internal combustion engine 1 includes an air cleaner 2. Air is taken in through the intake duct 3, the throttle chamber 4, and the intake manifold 5. The air cleaner 2 has an intake air (atmospheric) temperature TA (
An intake air temperature sensor 6 is provided to detect 'C).

The throttle chamber 4 is provided with a throttle valve (intake throttle valve) 7 that variably controls the opening area of the throttle chamber 4 in conjunction with an accelerator pedal (not shown).
Control the intake air flow i1Q.

The throttle valve 7 has a potentiometer that detects its opening degree TVO, as well as a potentiometer that detects its fully open position (idle position).
A throttle sensor 8 is attached that includes an idle switch 8A that is turned on when the vehicle is turned on.

This throttle sensor 8 corresponds to the opening area detection means in this embodiment.

The intake manifold 5 downstream of the throttle valve 7 is provided with an intake pressure sensor 9, which serves as an intake pressure detection means for detecting the intake pressure PB, and is connected to the intake manifold 5 via a pipe 9a. A valve 10 is provided.

The fuel injection valve 10 is driven to open by a drive noise signal output from a control unit 11 containing a microcomputer (to be described later) in synchronization with engine rotation, and is pressurized from a fuel pump (not shown) to a predetermined pressure by a pressure regulator. Controlled fuel is injected and supplied into the intake manifold 5. That is, the amount of fuel supplied by the fuel injection valve 10 is controlled by the valve opening drive time of the fuel injection valve 10.

Furthermore, a water temperature sensor 12 for detecting the cooling water temperature Tw in the cooling jacket of the engine 1 is provided, and the exhaust passage 1
An oxygen sensor 14 is provided within the engine 3 to detect the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas.

The control unit 11 counts a crank unit angle signal PO3 outputted from a crank angle sensor 15 as an engine rotational speed detection means for a certain period of time, or a crank reference angle signal R outputted at every predetermined crank angle position.
The engine rotation speed N is detected by measuring the cycle of EF (every 180 degrees in the case of a 4-cylinder engine).

In addition, the transmission attached to the engine 1 is provided with a vehicle speed sensor 16 for detecting vehicle speed and a neutral sensor 17 for detecting a neutral position, and these detection signals are input to the control unit 11'.

Additionally, an auxiliary air passage 18 bypassing the throttle valve 7
is provided with an electromagnetic idle control valve 19 that controls the idle rotation speed via the amount of auxiliary air. Furthermore,
An ignition plug 20 is provided facing the combustion chamber of each cylinder.

The control unit 11 calculates the basic fuel injection ITpPB based on the intake pressure PB detected by the intake pressure sensor 9, and also calculates the basic fuel injection amount Tp.
The final fuel injection 11Ti is calculated by applying various corrections to PB according to the engine operating state, and the opening drive of the fuel injection valve 10 is controlled based on this fuel injection amount Ti (engine control amount), while the intake pressure PB The ignition timing ADV (ignition advance angle) is set based on the engine rotation speed N and the ignition timing AD
V (controls the ignition timing by the spark plug 20 based on engine control).

Further, the control unit 11 controls the opening degree of the idle control valve 19 during the idle operation detected based on the idle switch 8A and the neutral sensor 17 by feedback controlling the duty ratio DUTY of the drive pulse signal supplied to the idle control valve 10. By doing so, the idle rotation speed is feedback-controlled to the target speed through variable control.

Furthermore, the control unit 11 includes an intake pressure sensor 9
When it is determined that the intake pressure sensor 9 has failed, predetermined fail-safe control is executed.

Next, various calculation processes performed by the control unit 11 will be explained according to the routines shown in the flowcharts of FIGS. 3 to 7, respectively.

In this embodiment, the functions of the engine control amount setting means, the control means, the failure detection means, the opening area correction means, the engine control amount setting means for failure, and the failure control means are as shown in FIGS.
The software is provided as shown in the flowchart of FIG.

The routine shown in the flowchart of FIG.
This is a 1Ti calculation routine and is executed every 10m5.

First, step l (indicated as Sl in the figure).

The analog detection signal output from the throttle sensor 8 corresponding to the opening degree TVO of the throttle valve 7 is converted into a digital signal (A/D conversion) and input.

In the next step 2, the opening area S of the throttle chamber 4 is searched from a map based on the throttle valve opening degree TVO input in step 1.

Further, in step 3, the auxiliary air passage 1 is variably controlled by the idle control valve 19 based on the duty ratio DUTY of the drive pulse signal supplied to the idle control valve 19.
Find the opening area 5ISC of No. 8 by searching the map. The duty ratio DIITY includes, for example, a basic part based on the cooling water temperature Tw detected by the water temperature sensor 12, a correction part (idle up part) for when an external load such as an air conditioner compressor increases, and an idle rotation speed feedback correction part. etc. is set.

In step 4, when the piping 9a that guides the intake pressure (intake negative pressure) PB to the intake pressure sensor 9 is disconnected, the piping disconnection flag FPSR is set to 1 in the routine shown in the flowchart of FIG. 6, which will be described later. do.

Here, the pipe disconnection flag FPSR is 1 and the pipe 9
When a is disconnected, the outside air is directly introduced from the opening in the middle of the throttle chamber 4 to which the pipe 9a was connected, so the opening area searched based on the throttle valve opening degree TVO in step 2 is Piping 9a to S
It is necessary to add the increase due to deviation. Therefore, when the pipe dislocation flag FPSR is 1, the process proceeds to step 5, where the preset opening area ΔS corresponding to the cross-sectional area of the pipe 9a is added to the search data S in step 2 for correction. The result is newly set to the opening area S of the throttle chamber 4.

On the other hand, when it is determined in step 4 that the pipe disconnection flag FPSR is zero and the pipe 9a is not disconnected,
Intake pressure sensor9. However, since the opening area S of the throttle chamber 4 can be detected by the throttle valve opening TVO, the process skips step 5 and proceeds to step 6.

In step 6, the opening area 5ISC obtained in step 3 is added to the opening area S obtained in step 2 or the opening area S corrected in step 5, and the opening area A of the intake system of the engine 1 is calculated as the auxiliary air passage. 18, and also include the increase in opening when the pipe 9a is disconnected.

In step 7, the basic volumetric efficiency QHφ is calculated based on the value obtained by dividing the opening area A obtained in step 6 by the engine rotation speed N.
Find it by searching from the map.

In step 8, a value obtained by multiplying the weighted average value PBAVE of the intake pressure PB set in the routine shown in the flowchart of FIG. 4 by the engine rotational speed N (value equivalent to the intake air flow rate Q) is determined.
Based on this, in the next step 9, the weighting weight 2 used for weighted averaging of the basic volumetric efficiency QHφ is searched from the map.

In step 9, the basic volumetric efficiency QH obtained in step 7 is
φ and the volumetric efficiency QCYL calculated in step 9 during the previous execution of this routine are weighted averaged using 2 for the weighting weight determined in step 8, and the volumetric efficiency QCYL of engine 1 is calculated.
Find L (←QHφXK2+QCYL (1- to 2)). The weighted average of the weighted weight by 2 allows the volumetric efficiency QCYL, which is set based on the throttle valve opening TVO and the engine rotational speed N, to follow the true engine load change.

In step 10, the volumetric efficiency QC is calculated according to the following formula:
A basic fuel injection amount ANTp based on YL is calculated.

A N T p -KCONA X QCYL X K
FLATA X KLALT X KTAHere, KC
ONA is a constant based on the injection characteristics of the fuel injection valve 10, KF
LATA is a volumetric efficiency minute correction coefficient set in a background job to be described later, KLALT is an altitude correction coefficient also set in a background job, and KTA is also an intake temperature correction coefficient set in a background job.

Incidentally, the volumetric efficiency QCYL calculated in step 9 or the basic fuel injection amount ANTp calculated in step IO is as follows:
As will be described later, this is also data for searching the map for comparison data for determining failure of the intake pressure sensor 9.

In the next step 11, the basic volumetric efficiency correction coefficient KPB is searched from the map based on the weighted average value PBAVH of the sampling values of the intake pressure PB detected by the intake pressure sensor 9 at each minute time.

The weighted average value PBAVE is calculated according to the routine shown in the flowchart of FIG.

The routine shown in the flowchart of FIG. 4 is executed every 4as. First, in step 21, the intake pressure PB detected by the intake pressure sensor 9 is input,
In the next step 22, the weighted average value PBAVE obtained during the previous execution and the latest sampling value are weighted averaged according to the following formula, and the result is newly calculated as the weighted average value 4a P
Set it to B A V E.

The reason why the weighted average of the intake pressure PB is performed as described above is to avoid the detected value of the intake pressure PB used for setting the engine control amount from pulsating due to intake pulsation regardless of the true engine load state. .

Returning to the flowchart of FIG. 3 again, in step 11, the basic volumetric efficiency correction coefficient KPB is searched based on the weighted average value PBAVH of the intake pressure PB, and in the next step 12, this basic volumetric efficiency correction coefficient KPB is searched. is multiplied by the volumetric efficiency small correction coefficient KFLAT set in the background job described later to obtain the volumetric efficiency correction coefficient K.
Set QCYL (←KPB XKFLAT).

Then, in the next step 13, the intake pressure PBAV
The basic fuel injection amount TpPB is calculated according to the following formula using E, volumetric efficiency correction coefficient KQCYL, etc.

Tp PI3-KCONDXKQCYLXPBAVEX
KTA Here, KCOND is a constant determined from the injection characteristics of the fuel injection valve 10 similarly to KCONA, and KTA is the same intake temperature correction coefficient as used in calculating the basic fuel injection amount ANTp.

In the next step 14, when the intake pressure sensor 9 fails,
It is determined whether the failure determination flag FPSNG is set, and if the failure determination flag FPSNG is 0 and the intake pressure sensor 9 is normal, the process proceeds to step]5.

In step 15, in step 13, the intake pressure PBAVE
Using the basic fuel injection amount TPPB calculated based on , the final fuel injection amount Ti (engine control amount) is calculated according to the following formula.

Ti←2XTpPBXLAMBDAXCOEF+Ts Here, LA? IBDA is a feedback correction coefficient C0EF for feedback controlling the air-fuel ratio of the engine intake air-fuel mixture detected through the oxygen concentration in the exhaust gas detected by the oxygen sensor 14 to a target air-fuel ratio (for example, stoichiometric air-fuel ratio).
are various correction coefficients that are mainly set based on the cooling water temperature Tw detected by the water temperature sensor 12, and Ts is the fuel injection valve 1.
This is an opening/closing valve delay correction bone that is set according to voltage changes of the battery that serves as the driving power source. In addition, the basic fuel injection amount 'r
p PB multiplied by 2 is the sequential injection control that is performed in timing with the intake stroke of each cylinder,
This is to enable the basic fuel injection 1iTpPB to be used in common during all-cylinder simultaneous injection control in which fuel is supplied to each cylinder simultaneously, and the above calculation formula corresponds to sequential injection control.

On the other hand, when it is determined in step 14 that the failure determination flag FPSNG is 1, the failure of the intake pressure sensor 9 (
(including the disconnection of the piping 9a), therefore, if the fuel injection amount Ti is set using the basic fuel injection amount 'rpPB set based on the detected value of the intake pressure sensor 9, it will meet the engine requirements. In this case, the basic fuel injection amount ANT set in step 10 based on the opening area A and the engine rotational speed N cannot be performed.
The process proceeds to step 16 to set the final fuel injection amount Ti using p.

In step 16, a fuel injection amount Ti is calculated using the basic fuel injection amount ANTp according to the following formula.

T i←2XANTpXLAMBDAXCOEF+Ts
The above calculation formula is the same as the calculation formula for the fuel injection amount Ti in step 15 above, except that the basic fuel injection IANTp is different.

In this way, if the fuel injection amount Ti is set as the engine control amount without using the detected value of the intake pressure sensor 9 when the intake pressure sensor 9 fails, fuel supply control can be performed even if the intake pressure sensor 9 fails. Fail-safe control can be performed to ensure performance and supply fuel that meets engine requirements.

However, as will be described later, malfunctions of the intake pressure sensor 9 are detected by distinguishing between those caused by a disconnection of the piping 9a and those caused by other failures, and when the piping 9a is disconnected, it is possible that the malfunction of the intake system due to the disconnection is detected. Since the increase in aperture area is corrected (
In step 5), even when the sensor malfunctions due to the disconnection of the pipe 9a, the same fail-safe controllability as in the case where the disconnection of the pipe 9a is not the cause is ensured.

The fuel injection amount Ti set as described above is set in the output register of the control unit 11, and when a predetermined injection timing is reached, driving is performed with a pulse width equivalent to the latest fuel injection amount Ti set in this output register. A pulse signal is output to the fuel injection valve 10, and the fuel injection valve 10
is controlled to open for a predetermined period of time, and fuel is intermittently injected and supplied to the engine 1.

Next, the routine shown in the flowchart of FIG. 5 will be explained. This routine is executed as a background job (BGJ), and first, in step 31,
Based on the intake air temperature TA detected by the intake air temperature sensor 6, an intake air temperature (air density) correction coefficient KTA is searched from a map and determined. This intake air temperature correction coefficient KTA is the basic fuel injection amount AN in step 10 and step 13 described above.
It is used to calculate Tp and TpPB.

In the next step 32, the basic fuel injection amount TpPBO ratio e to the basic fuel injection amount ANTp calculated every 10 ms according to the routine shown in the flowchart of FIG.
(=ANTp/TpPB) is calculated.

In step 33, the altitude m is calculated from the map based on the ratio e calculated in step 32 and the intake air flow rate Q equivalent value obtained by multiplying the intake pressure PBAVH by the engine speed N.
Find it by searching. The basic fuel injection amount ANTP is set without being affected by the altitude m, but the basic fuel injection amount TpPB decreases as the altitude m increases and the air density becomes thinner. is increasing from the reference altitude (the altitude at which the basic fuel injection amount ANTp is matched). Also, since the above tendency is large in the region where the intake air flow rate Q is small, a map along the above relationship is prepared in advance. The altitude m can be found by setting it in advance.

In step 34, a correction value (hereinafter referred to as upper limit hos) for correcting the upper limit data of intake pressure PB (hereinafter referred to as NG upper limit PB) used for determining a failure of the intake pressure sensor 9 according to the altitude m. ) is obtained by searching from the map based on the altitude m obtained in step 33.

As the altitude m increases, the detection value of the intake pressure sensor 9 also decreases overall due to the decrease in air density (decrease in atmospheric pressure), so it is necessary to lower the NG upper limit PB level for failure determination accordingly. Therefore, as will be described later, the NG upper limit PB that meets the above request is corrected by subtracting the upper limit hos, which is set to increase as the altitude m increases, from the NG upper limit PB, which is the basic pressure.

Similarly, in the next step 35, a correction value (hereinafter referred to as NG lower limit PB) for correcting the lower limit data of intake pressure PB (hereinafter referred to as NG lower limit PB) used for determining a failure of the intake pressure sensor 9 according to the altitude m. , lower limit has) is determined by searching the map based on the altitude m determined in step 33.

In step 36, based on the volumetric efficiency QCYL calculated in step 9 and the engine rotational speed N, the volumetric efficiency correction coefficient KFLATA used in calculating the basic fuel injection amount ANT p in step 10 is searched from the map and determined. , based on the weighted average value PBAVE of the intake pressure PB and the engine rotational speed N, the volumetric efficiency minute correction coefficient (FLAT used in the calculation of the volumetric efficiency correction coefficient KQCYL in step 12) is determined by searching the map.

In step 37, the failure determination flag FPSNG is determined in the same manner as in step 14. Failure determination flag FPS
When NG is 0 and the intake pressure sensor 9 is normal, the process advances to step 38 and the ignition timing AD is determined as an engine control amount based on the intake pressure PBAVE and the engine rotational speed N.
Find V (ignition advance value) by searching from the map.

On the other hand, when the failure determination flag FPSNG is 1 and the intake pressure sensor 9 is out of order, the intake pressure PBAVE
Since it is not possible to set the ignition timing ADV based on the ignition timing ADV, the process proceeds to step 39 and searches for the ignition timing ADV from the map based on the volumetric efficiency QCYL and the engine rotational speed N calculated in step 9.

The volumetric efficiency QCYL is determined from the opening area A of the intake system and the engine rotational speed N without using the detected value of the intake pressure sensor 9, so even if the intake pressure sensor 9 fails, the engine 1 An ignition timing ADV that substantially meets the request is set. However, when the pipe 9a that guides the intake pressure PB to the intake pressure sensor 9 is disconnected and malfunctions, the opening area A is
This setting takes into account the increase in opening area due to the dislocation of the pipe 9a, so if the intake pressure sensor 9 fails, the pipe 9a
Even if the cause is a misalignment of the pipe 9a, it is possible to perform the same fail-safe control of the ignition timing ADV setting as in the case of a failure not caused by the dislocation of the pipe 9a.

Here, the set ignition timing ADV is detected based on the detection signal from the crank angle sensor 15, and the ignition timing ADV is detected based on the detection signal from the crank angle sensor 15.
When the DV is reached, an ignition signal is output to the ignition plug 20 to cause the ignition plug 20 to ignite at the ignition timing ADV.

In step 40, based on the altitude m, the altitude correction coefficient H,
Search for ALT from the map. This altitude correction coefficient KLALT is used to calculate the basic fuel injection amount ANTp in step 10 above.

Next, the intake pressure sensor (P
/S) Explain the diagnostic routine. This intake pressure sensor diagnostic routine is executed as a background job (BGJ).

First, in step 51, it is determined whether or not the engine rotational speed N is not zero, and if the engine 1 is in a stopped state where the rotational speed N is zero, this routine is directly terminated.

On the other hand, when the engine rotational speed N is not zero and the engine 1 is in an operating state including cranking, the process advances to step 52.

In step 52, the volumetric efficiency QCYL or the volumetric efficiency Q
Based on CYL (based on the basic fuel injection amount ANTp), search and find the NG lower limit PB, which is the basic intake pressure value for failure determination, from the map, and subtract the lower limit hos, which is the correction value based on the altitude m, from this NG lower limit PB. and the final NG lower limit PB
Set.

Similarly, in step 53, the NG upper limit PB is searched and determined from the map based on the volumetric efficiency QCYL or the basic fuel injection 1iANTp based on the volumetric efficiency QCYL.
The final NG upper limit PB is set by subtracting the upper limit hos, which is a correction based on the altitude m, from the upper limit PB.

Then, in step 54, the NG obtained in step 52 is
The lower limit PB is compared with the latest intake pressure PBAVE calculated by the routine shown in Figure 4, and the intake pressure PBAVE is determined to be N.
When the G lower limit PB is exceeded (for example, when the power supply harness is disconnected), it is assumed that the intake pressure sensor 9 is malfunctioning, and the process proceeds to step 58, where a failure determination flag FPSNG is set to 1.

On the other hand, when the intake pressure PBAVE is equal to or higher than the NO lower limit PB, the process proceeds to step 55 where the intake pressure PBAVE and the NO
Compare with G upper limit PB. Here, the intake pressure PBAVE
When exceeds the NG upper limit PB, there is a high possibility that the intake pressure sensor 9 is detecting atmospheric pressure due to the piping 9a being disconnected, so the detected value of the intake pressure sensor 9 is an abnormal value due to the piping 9a being disconnected. It is assumed that this is the case, and the process proceeds to step 57, where the piping disconnection flag FPSR is set to 1, and the process then proceeds to step 58, where the failure determination flag FPSNG is set to 1.

Therefore, even if the failure determination flag FPSNG is 1 when determining the failure of the intake pressure sensor 9, the piping disconnection flag FPSNG is 1.
From PSRζ, it can be determined whether the cause of the problem is a disconnection of the pipe 9a.

Also, in step 55, the intake pressure PBAVE is determined to be NG upper limit P.
If it is determined that the intake pressure PBAvE is below B and the intake pressure PBAvE is within the normal range sandwiched between the NG lower limit PB and the NG upper limit PB, it is assumed that the intake pressure sensor 9 is normal, and the process proceeds to step 56 to determine a failure. The flag FPSNG is set to zero, and the piping disconnection flag FPSR is also set to zero, so that both flags determine that the intake pressure sensor 9 is in a normal state.

Failure determination flag FPSNG set as above
However, as described above, the fuel injection amount Ti and ignition timing ADV
Fail-safe control is executed by switching the setting of engine control variables such as
When setting the opening area A, PSR switches whether or not to add an amount corresponding to the piping displacement.

Next, if the altitude m (atmospheric pressure) and the upper limit hos and lower limit hos based on the altitude m are set before starting the engine 1 according to the routine shown in the flowchart of FIG. 7, the intake pressure sensor 9 If the intake pressure sensor 9 is out of order at the time of starting, the settings of engine control variables such as fuel injection fiTi at the time of starting are shifted to fail-safe control that does not use the intake pressure PB. This ensures engine startability.

The routine shown in the flowchart of FIG. 7 is interruptedly executed when an ignition switch (IGN SW), not shown, is turned on, and in step 61, the intake pressure PB detected by the intake pressure sensor 9 is input. Here, since the engine 1 is not operating before the start switch is turned on, the intake pressure sensor 9 detects atmospheric pressure, so in the next step 62, the altitude m is mapped based on the detected intake pressure PB. Find it by searching.

In the next step 63.64, the steps 34, 3
Similarly to 5, the upper limit hos and the lower limit hos are each searched from the map according to the altitude m set based on the detected atmospheric pressure value.

As a result, when the engine 1 is started, before the upper limit has and the lower limit hos are set in the routine shown in FIG.
Upper limit hos and lower limit h set in the routine shown in Figure 7 above
Based on the os, the intake pressure sensor 9 is detected in the routine shown in FIG.
Since a failure determination is made, it is possible to quickly shift to fail-safe control from the time of startup, such as setting the fuel injection amount Ti based on the basic fuel injection @ANTp,
The engine 1 does not become unable to start due to a failure of the intake pressure sensor 9.

<Effects of the Invention> As explained above, according to the present invention, in a control device for an internal combustion engine that sets engine control variables such as fuel supply amount and ignition timing based on a detected value of intake pressure, intake pressure is detected. When a sensor malfunctions, the engine control amount is set based on the opening area of the engine intake system and the engine rotational speed instead of the intake pressure, and the malfunction is caused by a disconnection in the piping that leads the intake pressure to the sensor. When a failure occurs due to a pipe coming off, the detected value of the opening area is corrected by the increase in the opening area due to the pipe coming off.

As a result, when the sensor that detects intake pressure fails, it is possible to obtain almost the same fail-safe controllability, regardless of whether the failure is due to a pipe disconnection or another cause. This improves engine controllability when the sensor that detects intake pressure fails.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system schematic diagram showing the configuration of an embodiment of the present invention, and FIGS. 3 to 7 are flowcharts showing various calculation processes in the above embodiment, respectively. It is. 1...II section 4...Throttle chamber 7...
・Throttle valve (intake throttle valve) 8... Throttle sensor 9... Intake pressure sensor 9a... Piping 10... Fuel injection valve 11... Control unit 15... Crank angle sensor 18...
・Auxiliary air passage 19...Idle control valve 20
...Spark plug patent applicant Fujio Sasashima, agent of Japan Electronics Co., Ltd., patent attorney Figure 1 Figure 2

Claims (1)

[Scope of Claims] An intake pressure detection means for detecting the intake pressure of the engine, which is connected to the intake passage downstream of the intake throttle valve via piping, and engine control based on the intake pressure detected by the intake pressure detection means. An internal combustion engine control device comprising: an engine control amount setting means for setting an amount of intake air; and a control means for controlling the engine based on the engine control amount set by the engine control amount setting means. A failure detection means for detecting a failure of the pressure detection means by distinguishing between a disconnection of piping connected to an intake passage and other failures; an opening area detection means for detecting an opening area of an engine intake system that is variably controlled; an engine rotational speed detection means for detecting an engine rotational speed; and when a piping dislocation is detected by the failure detection means, an increase in the opening area of the engine intake system due to the piping displacement is determined by an opening area detected by the opening area detection means. an opening area correction means for correcting and setting an opening area by adding to the opening area; a failure engine control amount setting means for setting an engine control amount for failure based on the opening area and the engine rotational speed; and the failure detection means. failure control means for controlling the engine based on the failure engine control amount with priority over the control means when a failure of the intake pressure detection means is detected in Fail-safe device for internal combustion engine control equipment.