JP2001132521A - Control method when pressure detector of internal combustion engine is out of order - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent possible adverse effect to a catalyst cased by air-fuel ratio sometimes inclining toward a rich side or a lean side if fuel quantity is calculated using alternative fixed value of intake pipe pressure when an intake pressure sensor is out of order. SOLUTION: An internal combustion engine is provided with a pressure detector detect the pressure of an intake system 1. A flow rate control valve 16 is attached in a detour to go around a throttle valve 2 prepared in the intake system 1. At least during idling operation, the opening of the flow rate control valve 1b is control so that the number of engine revolution agrees with the target number of idling revolutions. The number of engine revolutions and the opening of the throttle valve 2 are detected when a trouble is cased in the pressure detector. The pressure in the intake system 1 is predicted based on the detected number of engine revolutions and the opening of the throttle valve 2. The predicted pressure is corrected based on the opening of the flow rate control valve 1b and the quantity of fuel is controlled based on the corrected pressure and the number of engine revolutions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a fuel amount based on an engine speed and an intake system pressure.
The present invention relates to a pressure detector abnormality control method for an internal combustion engine that controls a fuel amount by predicting an intake system pressure when an abnormality occurs in a pressure detector.

[0002]

2. Description of the Related Art Heretofore, there has been known an internal combustion engine whose fuel injection amount is controlled by an electronic control unit, using a pressure sensor for detecting an intake pipe pressure to control the fuel injection amount. That is, the intake pipe pressure is detected by the pressure sensor, and the fuel injection amount is determined based on the detected intake pipe pressure and the engine speed. In such an internal combustion engine, when the pressure sensor indicates a failure or abnormality, the fuel injection amount cannot be controlled.For example, it is assumed that an idle switch that detects the open / closed state of the throttle valve is on and off. The intake pipe pressure corresponding to each case is set in advance, and the fuel injection amount is determined based on the set intake pipe pressure, which is a fixed value, and the engine speed.

[0003] Further, when the pressure sensor fails, as in Japanese Patent Application Laid-Open No. 11-82132, for example, the intake pipe pressure is estimated from the opening of the throttle valve,
It is also known to determine the fuel injection amount from the estimated intake pipe pressure, engine speed, and throttle valve opening.

[0004]

However, in the case where the fuel injection amount is controlled based on the preset intake pipe pressure when the pressure sensor fails, there are cases where the air-fuel ratio becomes rich depending on the operation state of the internal combustion engine. The case where it becomes thin occurs. That is, when the throttle valve is slightly opened, the air-fuel ratio becomes rich, and when the throttle valve is fully opened, the air-fuel ratio becomes thin. For this reason,
In addition to creating a factor that degrades the catalyst, such as the temperature of the catalyst attached to the exhaust system becoming too high, it also reduced drivability.

By the way, in an internal combustion engine in which a flow control valve is provided in a bypass that bypasses the throttle valve and the flow control valve is opened and closed to control the intake air amount during idling operation, the temperature of the internal combustion engine and the air conditioner When the flow control valve whose control amount is determined according to the state of the load such as the above is opened, the intake pipe pressure may be different. When the above-mentioned publication is applied to such an internal combustion engine, when estimating the intake pipe pressure from the opening degree of the throttle valve, the change in the intake pipe pressure due to the opening degree of the flow control valve is not reflected, and the catalyst deterioration is accelerated. May be.

An object of the present invention is to solve such a problem.

[0007]

In order to achieve the above object, the present invention takes the following measures. That is, the control method for an abnormality in the pressure detector of the internal combustion engine according to the present invention estimates the pressure of the intake system based on the opening degree of the throttle valve and the engine speed when an abnormality or the like occurs in the pressure detector. In this configuration, the estimated pressure is corrected based on the opening degree of the flow control valve in the bypass that bypasses the throttle valve, and the fuel amount is controlled based on the corrected pressure.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has a pressure detector for detecting the pressure of an intake system, and a flow control valve is provided in a bypass which bypasses a throttle valve provided in the intake system. In an internal combustion engine in which the opening of the flow control valve is controlled such that the engine speed becomes the idle target speed, the engine speed and the throttle valve opening when an abnormality occurs in the pressure detector are detected, Predict the pressure of the intake system based on the detected engine speed and the opening of the throttle valve, correct the predicted pressure based on the opening of the flow control valve, and based on the corrected pressure and the engine speed. This is a control method for an internal combustion engine when a pressure detector is abnormal, which controls a fuel amount.

With such a configuration, since the pressure of the intake system is predicted from the engine speed and the opening of the throttle valve, the pressure of the intake system according to the operating state at that time can be accurately predicted. It will be. Then, since the predicted intake system pressure is corrected based on the opening degree of the flow control valve of the detour bypassing the throttle valve, reflecting that the pressure of the intake system changes depending on the opening degree of the flow control valve, It becomes possible to predict the pressure of the intake system. Therefore, even when the pressure detector is abnormal, it is possible to suppress the air-fuel ratio from being biased toward the rich side or vice versa. Moreover, since the pressure of the intake system is predicted in consideration of the degree of opening of the flow control valve in the detour, the fuel amount can be accurately controlled even though the pressure detector is abnormal. . Therefore, it is possible to reduce the influence that leads to the deterioration of the catalyst provided in the exhaust system, and to prevent the drivability from lowering.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. The engine whose one-cylinder structure is schematically shown in FIG. 1 is a four-cylinder engine for an automobile, and an intake system 1 of the engine is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown). The surge tank 3 is provided on the downstream side, and the intake air from the surge tank 3 is sucked into the cylinder via the intake valve 37. The intake system 1 is provided with a bypass passage 1a which is a detour bypassing the throttle valve 2. The bypass passage 1a has a flow control valve (hereinafter, referred to as a flow control valve) for controlling the amount of air passing through the bypass passage 1a. An "ISC valve" is abbreviated.) 1b is provided. The ISC valve 1b performs control at the time of executing idle rotation control (hereinafter, abbreviated as "ISC") for correcting the intake air amount so that the engine speed NE at least in the idle operation state becomes the idle target speed. Opening control is performed when a load acting on the engine such as an air conditioner or a headlight is activated. A fuel injection valve 5 is further provided near an end of the intake manifold 4 of the intake system 1 communicating with the surge tank 3 on the cylinder head side. The fuel injection valve 5 is controlled by an electronic control unit 6. ing. Also, the exhaust system 20
The O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas discharged from the combustion chamber via the exhaust valve 36 is provided with a three-way catalyst 2 disposed in a pipe to a muffler (not shown).
2 upstream.

The electronic control unit 6 is mainly composed of a microcomputer system including a central processing unit 7, a storage device 8, an input interface 9, and an output interface 11. The input interface 9 receives an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure (intake pipe pressure) in the surge tank 3 and a rotational speed sensor 14 for detecting an engine rotational speed NE. The output rotation speed signal b, the crank angle signal m and the cylinder discrimination signal n output from the cam position sensor 25, the throttle opening signal output from the throttle sensor 16a corresponding to the opening of the throttle valve 2, the throttle valve 2, an IDL signal d output from the idle switch 16 for detecting the open / close state of the engine ₂ , a water temperature signal e output from the water temperature sensor 17 for detecting the engine coolant temperature, and an output from the O ₂ sensor 21 described above. The voltage signal h and the like are input. On the other hand, from the output interface 11, a drive pulse INJ, which is a fuel injection signal f, to the fuel injection valve 5,
, An ignition signal g is output.

The electronic control unit 6 uses the intake pressure signal a output from the intake pressure sensor 13 and the rotational speed signal b output from the rotational speed sensor 14 as main information and is determined according to the operating state of the engine. The basic injection time, that is, the basic injection amount TAUB is corrected with various correction coefficients to determine the final injection time, that is, the fuel injection amount TAU, which is the fuel injection valve opening time, and the fuel injection valve 5 is controlled based on the determined time. In addition, a program for injecting the fuel fuel amount TAU according to the operating state of the engine from the fuel injection valve 5 to the intake system 1 is incorporated. In the fuel injection amount control program, when an abnormality occurs in the intake pressure sensor 13, instead of the intake pipe signal a, a basic injection amount pressure prediction value PM to be described later is used.
The fuel injection amount TAU is calculated using TP.

The electronic control unit 6 detects the engine speed NE, which is the engine speed, and the opening of the throttle valve 2 when the intake pressure sensor 13, which is a pressure detector, becomes abnormal. The pressure of the intake system 1, that is, the intake pipe pressure PM is predicted based on the rotational speed NE and the opening degree of the throttle valve 2, and the predicted intake pipe pressure PM is corrected based on the opening degree of the ISC valve 1b. Pipe pressure P
A program for controlling the fuel amount based on M and the engine speed NE is stored.

Next, a schematic procedure of the control program at the time of abnormality of the intake pressure sensor will be described with reference to FIGS. In the case of this four-cylinder engine, abnormality determination of the intake pressure sensor 13 is performed, for example, four times in two revolutions, that is, once per cylinder. First, in FIG. 2, in step S1, it is determined whether or not the intake pressure sensor 13 is abnormal.
The abnormality of the intake pressure sensor 13, for example, when the intake pressure sensor 13 is disconnected, the intake pressure signal a becomes 0,
In the case of a short circuit, a certain intake pressure signal a is output, so that the detection is performed by confirming the presence or absence of the intake pressure signal a. If it is determined in step S1 that there is no abnormality, the execution of this routine is terminated. If it is determined that there is an abnormality, the process proceeds to step S2, and it is determined whether or not the throttle sensor 16a is abnormal. If it is determined that the throttle sensor 16a is normal, the process proceeds to step S3, and the basic injection amount pressure prediction value PMTP
Is determined by the intake pipe pressure final predicted value PMFFS. on the other hand,
If it is determined that the throttle sensor 16a is abnormal, the process proceeds to step S4, and the intake pipe pressure PM is determined by a preset fixed value.

The intake pipe pressure final predicted value PMFFS is calculated by the following procedure. This intake pipe pressure final predicted value PM
The calculation of the FFS is performed, for example, every 8 ms. First, in step S11, a two-dimensional map of the throttle opening is searched based on the throttle opening TA and the engine speed NE to obtain a basic intake pipe pressure predicted value TAPMB based on the throttle opening TA. In this two-dimensional throttle opening degree map, the basic intake pipe pressure predicted value TAPMB is set based on a representative value of the throttle opening degree TA and the engine speed NE. In cases other than the representative value, interpolation calculation is performed. Is what you want.

In step S12, the learning value DLRN of the opening of the ISC valve 1b is set to 50% of the opening of the ISC valve 1b.
Based on the throttle opening TA and the engine speed NE at the value added to the above, the opening degree correction two-dimensional map is searched to obtain the intake pipe pressure ISC opening basic predicted value ISCPMB. The learning value DLRN is a learning value in the ISC, and is updated in order to absorb variations in characteristics of the ISC valve 1b and changes with time. In step S13, the interpolation coefficient map for correcting the ISC valve opening is searched based on the actual ISC valve opening when the intake pressure sensor 13 is abnormal, and the interpolation coefficient KISCPM is obtained. In each of these maps, since the representative value is set,
Other values are obtained by performing interpolation calculations. Next, in step S14, the intake pipe pressure ISC opening basic predicted value ISPPM obtained in step S12 is obtained.
B and the interpolation coefficient KISC obtained in step S13
PM and the intake pipe pressure ISC opening predicted value ISCP
Calculate M.

In step S15, the intake pipe pressure basic predicted value TAPMB and the intake pipe pressure ISC open predicted value ISPPM are added, and the sum is multiplied by an atmospheric pressure correction coefficient KPA to correct the atmospheric pressure. Is calculated. In step S16, it calculates the following equation a current 8m seconds after the intake pipe pressure estimated value PMFs _n. PMFS _n = PMFS _n-1 + TCON _n × (TAPM _n
−PMFS _n−1 ) Here, TCON _n is a charge delay time constant of the intake system 1 and is obtained by searching a map set by the engine speed NE and the throttle opening TA. This time, n-1 indicates the one calculated last time.
This predicted intake pipe pressure PMFS after 8 ms is the same as the intake pipe pressure predicted value TAPM calculated this time, if the intake pipe pressure predicted value PMFS _n-1 calculated last time is the same as the intake pipe pressure predicted value TAPM calculated this time. The predicted pipe pressure value PMFS _n-1 is set as the predicted intake pipe pressure value PMFS _n after 8 msec this time.

In step S17, the engine speed NE
The time until the next intake is calculated, and the intake pipe pressure final predicted value PMFF is calculated from the intake pipe pressure predicted value PMFS after 8 ms.
Calculate S. In such a configuration, when the throttle sensor 16a is normal and the intake pressure sensor 13 is abnormal, the control proceeds to steps S1, S2, and S3, and the final estimated intake pipe pressure value PMFFS is used for the basic injection amount. The fuel injection amount is determined based on the basic injection amount pressure prediction value PMTP and the engine speed NE as the pressure prediction value PMTP. In this case, the intake pipe pressure final predicted value PMFF
S is the engine speed NE at this time and the throttle opening T
The calculation is based on A and the ISC valve opening. That is, Steps S11 to S17 are executed, taking into account the correction due to the atmospheric pressure and the charge delay of the intake system 1, and calculating the time until the next intake based on the engine speed NE at the time of this calculation. This is to calculate the intake pipe pressure final predicted value PMFFS.

That is, the throttle opening degree T is determined according to the operating state of the engine when the intake pressure sensor 13 becomes abnormal.
A basic intake pipe pressure prediction value TA which is an intake pipe pressure based on A
PMB is predicted and its intake pipe pressure basic predicted value TAPMB
Is the intake pipe pressure IS predicted from the opening of the ISC valve 1b
The C opening predicted value ISCPMB is added to the bypass passage 1a.
Is for predicting the intake pipe pressure PM when is open. In addition, the time from when the intake pipe pressure PM is predicted to the next intake stroke is predicted from the engine speed NE at that time, and based on the predicted time, the intake pipe pressure PM during the next intake stroke, that is, the intake Pipe pressure final predicted value P
MFFS is calculated.

Therefore, even when the intake pressure sensor 13 has failed, the engine load and the engine speed N
The basic injection amount predicted pressure value PMTP corresponding to E can be calculated, and therefore the fuel injection amount TAU can be controlled with the predicted intake pipe pressure PM that reflects the operating state of the engine. As a result, even when the intake pressure sensor 13 is out of order, the fuel injection amount TAU is in accordance with the engine operating state. Therefore, the air-fuel ratio is biased toward the rich side or the lean side even during limp-home operation. Is suppressed,
The influence on the three-way catalyst 22 can be minimized, and a decrease in drivability can be prevented. In addition, the charge delay of the intake air in the intake system 1 is corrected by the charge delay time constant TCON, and the predicted intake pipe pressure value PMFS is corrected by the engine speed NE after 8 ms so as to correspond to the next suction stroke. Since the pipe pressure final predicted value PMFFS is set, even if there is a time delay between the calculation of the fuel injection amount TAU during a transition or the like, the time delay is taken into account, and the three-way catalyst 22 is used.
And the effect on drivability can be minimized.

On the other hand, when the intake pressure sensor 13 and the throttle sensor 16a indicate an abnormality, the control proceeds to steps S1, S2, S4, and sets the intake pipe pressure PM to a fixed value set in advance to change the fuel. The injection amount TAU is calculated. Therefore, even in such a case, since the intake pipe pressure PM is a fixed value, the air-fuel ratio is different from the actual one when acceleration / deceleration is performed. Can be implemented.

The present invention is not limited to the embodiment described above. In addition, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0023]

As described above, according to the present invention, since the pressure of the intake system is predicted from the engine speed and the opening of the throttle valve, the pressure of the intake system according to the operating state at that time can be accurately determined. Since the predicted intake system pressure is corrected based on the opening degree of the flow control valve in the detour bypassing the throttle valve, it is possible to predict that the intake system pressure changes depending on the opening degree of the flow control valve. The pressure of the intake system can be predicted by reflecting the pressure. Therefore, even when the pressure detector is abnormal, it is possible to suppress the air-fuel ratio from being biased toward the rich side or vice versa. In addition, since the pressure of the intake system is predicted in consideration of the opening of the flow control valve in the bypass, the fuel amount can be accurately controlled even though the pressure detector is abnormal. Therefore, it is possible to reduce the effect of deteriorating the catalyst provided in the exhaust system, and to prevent a decrease in drivability.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view showing one embodiment of the present invention.

FIG. 2 is a flowchart showing an outline of a control procedure of the embodiment.

FIG. 3 is a flowchart showing an outline of a control procedure of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Intake system 1a ... Bypass passage 1b ... Flow control valve 2 ... Throttle valve 6 ... Electronic control unit 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 11 ... Output interface 13 ... Intake pressure sensor 16a ... Throttle sensor

Continued on the front page F term (reference) 3G301 JB01 JB07 JB08 JB09 KA07 LA04 MA13 NB02 NB15 NC02 NC06 ND21 NE16 PA07B PA07Z PA09Z PA11Z PA14Z PA15A PD03A PE01Z PE03Z PE08Z PF13Z

Claims (1)

[Claims] 1. A pressure detector for detecting a pressure of an intake system, a flow control valve provided in a bypass route bypassing a throttle valve provided in the intake system, and an opening of the flow control valve at least at idle operation. In an internal combustion engine that is controlled so that the engine speed becomes the idle target speed, the engine speed and the throttle valve opening when an abnormality occurs in the pressure detector are detected, and the detected engine speed and Predicting the intake system pressure based on the throttle valve opening, correcting the predicted pressure based on the opening of the flow control valve, and controlling the fuel amount based on the corrected pressure and the engine speed. A control method for an internal combustion engine when a pressure detector is abnormal.