JPH01155046A - Electronic control fuel injection system for internal combustion engine - Google Patents

Abstract

PURPOSE:To make an air-fuel ratio variation at highland quickly avoidable by compensating a proportional constant and an integration constant in an air-fuel ratio feedback control system for augmentation when atmospheric pressure varies at the rate of more than the specified value. CONSTITUTION:Each detected value of a throttle sensor 8, an intake pressure sensor 9, a water temperature sensor 12, an oxygen sensor 14, a crank angle sensor 15 or the like is inputted into a control unit 11, and thereby the valve opening time for a fuel injection valve 10 is operated and controlled. In addition, the control unit 11 sets a fundamental fuel injection quantity on the basis of intake pressure and engine speed, while on the basis of the engine speed and the fundamental fuel injection quantity, it performs air-fuel ratio feedback control on the basis of the detected value of the oxygen sensor 14 at low and medium load driving areas. Then, it detects atmospheric pressure with output of the intake pressure sensor 9 at the high load area where an intake air quantity is not varied, and when the rate of the variation is more than the specified value, it compensates a proportional constant and an integration constant in the air-fuel ratio feedback control for augmentation.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an electronically controlled fuel injection device for an internal combustion engine, and in particular, the present invention relates to an electronically controlled fuel injection device for an internal combustion engine. The present invention relates to an electronic side 'a fuel injection device configured to set a fuel injection amount based on a detected value of.

<Prior art> In this type of device, when setting the basic fuel injection amount Tp corresponding to the amount of air taken into the combustion chamber, a two-dimensional map is created according to the intake pressure PB and the engine rotation speed N. From the data of the basic fuel injection amount 'rp stored in advance, data of the basic fuel injection amount Tp corresponding to the relevant operating state is searched and determined based on the detected values of the intake pressure PB and the engine rotation speed N. (See Japanese Unexamined Patent Publication No. 59-206624, etc.).

Then, the basic fuel injection amount Tp is corrected according to the engine operating state such as the engine temperature, and also corrected by the feedback correction value of the air-fuel ratio to set the final fuel injection amount Ti. By outputting an injection pulse signal with a pulse width corresponding to , to the electromagnetic fuel injection valve and opening the valve for a predetermined time, fuel corresponding to the fuel injection amount Ti is injected and supplied to the engine.

<Problems to be Solved by the Invention> By the way, when going to a high altitude and the atmospheric pressure decreases, the volumetric efficiency of fresh air increases due to the effect of a decrease in exhaust pressure, especially in operating conditions where the intake air flow rate Q is small. Even if the intake pressure and engine rotation speed are the same as at low altitudes, the amount of air actually taken into the engine increases at high altitudes, but the setting of the basic fuel injection amount 'rp for intake pressure PB and engine rotation speed N is based on the low altitudes. As a result, the base air-fuel ratio becomes over-lean at high altitudes, especially in low air volume regions.

In order to avoid such a lean air-fuel ratio at high altitudes, Japanese Patent Application Laid-Open No. 58-133432 and Japanese Patent Application Laid-open No. 58-13343 have been proposed.
There is a method of correcting according to atmospheric pressure or exhaust pressure as disclosed in Publication No. 3, etc., but it is necessary to always accurately correct the air-fuel ratio due to variations in filling efficiency in the low air volume region of the engine due to manufacturing variations. Therefore, in low air flow ranges such as idling, it is necessary to avoid over-leaning of the air-fuel ratio based on the air-fuel ratio feedback correction value (in combination with air-fuel ratio learning control).

However, it is necessary to rely on feed pump control for air-fuel ratio control until air-fuel ratio learning is established in low air flow ranges such as idling, and it becomes possible to cope with the increase in fresh air volumetric efficiency at high altitudes. However, as shown in Figure 9, during deceleration at high altitudes, there was a short transition from an operating state in which the increase in fresh air volumetric efficiency was small (high air volume region) to an operating state in which the increase was large (low air volume region). In such cases, there is a problem in that due to a delay in control response, the over-lean air-fuel ratio cannot be fully corrected by feedback control, leading to the engine stalling.

The present invention has been made in view of the above problems, and is an electronically controlled fuel injection system in which the basic fuel injection amount is set based on intake pressure and engine rotation speed, which allows air-fuel ratio fluctuations when going to high altitudes. so that it can be suppressed as quickly as possible,
The purpose is to improve the stability of idling operation at high altitudes.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. a basic fuel injection amount setting means for setting a basic fuel injection amount based on the engine rotational speed and intake pressure detected by the detection means; an air-fuel ratio detection means for detecting an air-fuel ratio of an engine intake air-fuel mixture; a feedback correction value setting means for setting a feedback correction value for correcting the basic fuel injection amount by comparing the set air-fuel ratio with a target air-fuel ratio so as to bring the actual air-fuel ratio closer to the target air-fuel ratio, using proportional-integral control; , atmospheric pressure detection means for detecting atmospheric pressure, and control in proportional integral control of the feedback correction value by the feedback correction value setting means when the atmospheric pressure detected by the atmospheric pressure detection means is changing at a predetermined rate or more. A control constant increase correction means for increasing the constant; a fuel injection amount setting means for setting the fuel injection amount based on the basic fuel injection amount and the feedback correction value set by the respective setting means; and the fuel injection amount setting means. An electronically controlled fuel injection device is configured to include: fuel injection control means for driving and controlling the fuel injection means according to the fuel injection amount set by the means;

Effect> In this configuration, the basic fuel injection amount setting means sets the basic fuel injection amount based on the engine rotational speed and intake pressure detected by the engine operating state detection means.

The feedback correction value setting means uses proportional-integral control to set a feedback correction value for correcting the basic fuel injection amount so that the air-fuel ratio of the engine intake air-fuel mixture detected by the air-fuel ratio detection means approaches the target air-fuel ratio. Here, when the atmospheric pressure detected by the atmospheric pressure detection means is changing at a rate higher than a predetermined rate, that is, when the change in altitude is large, the control constant increase correction means performs proportional integral calculation of the feedback correction value by the feedback correction value setting means. The control constant of the control is increased to improve the responsiveness of the feedback correction value.

The fuel injection amount setting means sets the fuel injection amount based on the feedback correction value and the basic fuel injection amount, and the fuel injection control means drives and controls the fuel injection means in accordance with this fuel injection amount.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 2 showing the configuration of an embodiment, an internal combustion engine 1 includes an air cleaner 2. Intake duct 3. Air is drawn in via the throttle chamber 4 and the intake manifold 5.

The throttle chamber 4 is provided with a throttle valve 7 (not shown) which is interlocked with an accelerator pedal and controls the intake air flow rate Q. The throttle valve 7 has its opening T.
A throttle sensor 8 is attached that detects VO and includes an idle switch 8A that is turned on at the idle position. Intake manifold 5 downstream of the throttle valve 7
is provided with an intake pressure sensor 9 that detects the intake pressure PB (note that the intake pressure sensor 9 also detects atmospheric pressure as described later, so it also serves as atmospheric pressure detection means), and An electromagnetic fuel injection valve 1° is provided as a fuel injection means for each cylinder.

The fuel injection valve 10 is driven to open by an injection pulse signal from a control unit 11 incorporating a microcomputer, which will be described later, and receives fuel, which is pressure-fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator, into the intake manifold 5. Supply injection to.

Further, a water temperature sensor 2 for detecting the cooling water temperature Tw in the cooling jacket of the engine is provided, and an exhaust passage 13 is also provided.
An oxygen sensor 4 is provided as an air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas. Further, a rotation speed sensor 5 such as a crank angle sensor for detecting the engine rotation speed N is provided. The intake pressure sensor 99, rotational speed sensor 5, etc. correspond to engine operating state detection means.

The control unit 11 sets the basic fuel injection amount 'rp based on the engine rotational speed N and the intake pressure PB detected as described above, and also sets the basic fuel injection amount Tp based on the engine speed N and the intake pressure PB detected as described above. Air-fuel ratio feedback correction coefficient LAM set based on the air-fuel ratio
The final fuel injection amount Ti is set by correcting it according to various correction coefficients C0EF, etc. set based on BDA, cooling water temperature Tw, etc., and an injection pulse signal with a pulse width corresponding to this fuel injection amount Ti is generated. The fuel injection valve 10 is driven and controlled by outputting the signal to the fuel injection valve 10.

That is, in this embodiment, the control unit 11 also serves as feedback correction value setting means, control constant increase correction means, fuel injection amount setting means, and fuel injection control means.

Next, the operation will be explained according to various control routines shown in the flowcharts of FIGS. 3 to 5 and 8.

FIG. 3 shows an intake pressure detection routine that is executed every set period (for example, 4 times), and the output voltage from the intake pressure sensor 9 is detected at step (indicated as "S" in the figure, and the same applies hereinafter). In step 2, the intake pressure PB is calculated from a one-dimensional map stored in the ROM according to the output voltage VpB.
(mmHg) is obtained by searching.

FIG. 4 shows a fuel injection amount calculation routine that is executed every set period (for example, 10 IIIS). In step E1, in addition to the intake pressure PB obtained as described above, detection signals from various sensors are do.

In step 12, the intake pressure PB and the engine rotational speed N are set in advance.
Based on the detected values input in step 11, the basic fuel injection amount Tp is searched from a two-dimensional map stored in the ROM in advance.

In the next step 13, various correction coefficients C0E are determined according to the cooling water temperature Tw detected by the water temperature sensor 12, the engine transient operating state detected by the throttle sensor 8, etc.
F is set, and in step 14, a correction numerator s is set for correcting a change in the effective valve opening time of the fuel injection valve 1o due to a change in battery voltage.

In step E5, the air-fuel ratio feedback correction coefficient LAMBDA is read as the feedback correction value set in the feed puncture correction coefficient setting routine of FIG.
The learning correction coefficient KLRN, which is learned for each area of the engine operating state, is read based on the deviation from the reference value (1) of AMBDA.

The learning correction coefficients KL and IN are for obtaining the stoichiometric air-fuel ratio, which is the target air-fuel ratio, without the air-fuel ratio feedback correction coefficient LAMBDA, and perform air-fuel ratio feedback correction for each of multiple areas of the engine operating state. Coefficient L
The deviation from the standard value of AMBDA is learned, and the RN is sequentially rewritten and stored in the learning correction coefficient of the area based on the deviation indicating the air-fuel ratio change including the altitude change and component variation. .

Then, in the next step 17, the final fuel injection amount T
i is calculated according to the following equation.

T i =T p XCOEFXLAMBDAX KL
IIN +T sIn step 18, the fuel injection amount Ti calculated in step 17 is set in the output register. As a result, at a predetermined fuel injection timing synchronized with the engine rotation, a drive pulse signal having a pulse width equivalent to Tf is output to the fuel injection valve 1o, and fuel injection is performed.

The routine shown in the flowchart of FIG. 5 is a routine for setting a coefficient K for increasing/decreasing control constants (proportional constant and integral constant) in proportional/integral control of the air-fuel ratio feedback correction coefficient LAMBDA.
Then, it is determined whether the current operating state is in the Q flat region.

This Q flat region is a high-load operating state in which the intake air flow rate Q of the engine does not change in response to changes in the throttle valve opening, and as shown in FIG. The determination is made based on the detected value of TVO.

Here, when it is determined that the current engine operating state is in the Q flat region, the intake pressure PB currently detected by the intake pressure sensor 9 is in a state that substantially matches the atmospheric pressure, so the process proceeds to step 23. Set the intake pressure PB as atmospheric pressure. This is because in the Q flat region, the intake air flow rate Q does not increase even when the throttle valve 7 is opened, and this is because the pressures on the upstream and downstream sides of the throttle valve 7 are approximately the same. It can be considered that the intake pressure PB detected by the intake pressure sensor 9 in the Q flat region substantially matches the atmospheric pressure.

On the other hand, when it is determined in step 21 that the current operating state is not in the Q flat region, the process proceeds to step 22, where it is determined whether or not the engine l is in a state before starting. Before starting and when the piston is not reciprocating, both the upstream and downstream sides of the throttle valve 7 are at atmospheric pressure. Therefore, when it is determined in step 22 that the state is before starting, the process advances to step 23 to determine the current state. The intake pressure PB detected value is set as atmospheric pressure.

Note that when the current operating state is not in the Q-flunt region and is not before starting, the intake pressure sensor 9 provided downstream of the throttle valve 7 cannot detect atmospheric pressure, so step 23 Jump to step 24. Further, in this embodiment, the atmospheric pressure is also detected using the intake pressure sensor 9, but a pressure sensor exclusively for atmospheric pressure detection may be provided.

In step 24, the difference between the latest value of atmospheric pressure set in step 23 and the previous set value is determined, and it is determined whether the atmospheric pressure (altitude) is changing rapidly.

When the atmospheric pressure is approximately constant and the vehicle is traveling at a constant altitude, the process proceeds to step 28 where the coefficient K
By setting 1.0 to 1.0, the control constants (proportional and integral) in the proportional-integral control of the air-fuel ratio feedback correction coefficient LAMBDA are set to initial values.

On the other hand, if it is determined that the altitude is changing rapidly, the process proceeds to step 25 where it is determined whether the current operating state is in an operating region where the intake air flow rate Q is small (hereinafter referred to as the low Q region). As shown in FIG. 7, the determination is made based on the current intake pressure PB and engine rotational speed N.

In general, as altitude increases and atmospheric pressure becomes lower (lower exhaust pressure decreases, fresh air volumetric efficiency increases compared to lower altitudes).Especially in the low Q region, this increase in fresh air volumetric efficiency is large, and the intake pressure PB The basic fuel injection amount Tp, which is set based on In the Q region, the control constant is corrected to increase the responsiveness of the feedback control.In addition, increasing the control constant in an operating state where the intake air flow rate Q is large may cause surge generation. Therefore, the increase correction of the control constant is performed only in the low Q?il range.

Therefore, even if it is determined in step 24 that the altitude change is rapid, if it is determined in step 25 that it is not in the low Q region, the process proceeds to step 28 and the coefficient K is set to 1.0.

On the other hand, if it is determined that the atmospheric pressure (altitude) change is rapid but in the low Q region, the process proceeds to step 26 and the average value LA of the air-fuel ratio feedback correction coefficient LAMBDA is calculated.
It is determined whether MBDA is close to the reference value (1). Here, the air-fuel ratio feed puncture correction coefficient LAMBD
When the average value LAMBDA of A is close to the reference value, the air-fuel ratio is controlled to approximately the target air-fuel ratio even without the air-fuel ratio feedback correction coefficient LAMBDA, so there is no need to increase the control constant. Proceed to step 28 and set the coefficient K to 1.0.

On the other hand, in step 26, the air-fuel ratio feedback correction coefficient L
When the average value LAMBDA of AMBDΔ is different from the reference value, the actual air-fuel ratio is controlled to the target air-fuel ratio by the air-fuel ratio feedback correction coefficient LAMBDA. Since the air-fuel ratio is in the low-Q region where changes have a large effect on the air-fuel ratio, the process proceeds to step 27 and the coefficient K is set to 1.3, which is larger than normal, thereby adjusting the air-fuel ratio feedback correction coefficient LA? IBD
The control constant in the proportional-integral control of A is increased and corrected to improve the responsiveness of the feedback correction control.

FIG. 8 shows a routine for setting the air-fuel ratio feedback correction coefficient LAMBDA, which is used to set the fuel injection amount Ti, by proportional-integral control, and is corrected based on the coefficient K set in the routine shown in the flowchart of FIG. Proportional-integral control is performed using control constants. Note that this routine is executed in synchronization with engine rotation.

In step 61, based on the latest engine rotational speed N and basic injection amount Tp, it is determined from a two-dimensional map stored in the ROM whether the air-fuel ratio feedback control is performed (low/medium load operating state of the engine). Determine.

If it is determined that the operating range is outside the range, this routine is not executed (it is terminated).

That is, the air-fuel ratio feedback correction coefficient LAMBDA is clamped to the current value (or reference value 1), and the air-fuel ratio feedback control is stopped.

If it is determined that it is in the operating region, step 62
Based on the engine rotational speed N and the basic injection amount Tp, the proportional bone P and the integral ■ in the feedback control are determined by searching from the map.

In step 63, the signal voltage Vo from the oxygen sensor 14 is
2, and in step 64 the signal voltage ■. 2 is compared with a reference voltage VREF corresponding to a target air-fuel ratio (stoichiometric air-fuel ratio) to determine whether the air-fuel ratio is rich or lean.

When the air-fuel ratio is lean (Voz<VRty), the process proceeds to step 65, where it is determined whether or not it is the time of reversal from rich to lean (immediately after the reversal), and when the air-fuel ratio is reversed, the process proceeds to step 66, where the current feedback correction coefficient is After storing the value of LAMBDA as a (lower peak value), step 67
Then, the air-fuel ratio feedback correction coefficient LAMBDA is increased from the previous value by the value obtained by multiplying the proportional bone P set in step 62 by the coefficient K.

Otherwise, the process proceeds to step 68, where the feed puncture and punch correction coefficient LAMBDA is increased from the previous value by the value obtained by multiplying the integral I set in step 62 by the coefficient K, and thus the feedback correction coefficient LA? 'Increase 1BDA at a constant slope. Note that P>>1.

At this time, if the coefficient K is set to 1.0, the air-fuel ratio feedback correction coefficient LAMBDA is increased at the normal rate, but in the routine shown in the flowchart of FIG.
．． When set to 3, the air-fuel ratio feedback correction coefficient LAMBDA is increased at a rate larger than the normal rate. In other words, the variation is large, but
Air-fuel ratio feedback correction coefficient LAMBDA in low Q region
When the average value LAMBDA has a deviation from the reference value 1, the coefficient K is set larger than usual, and the air-fuel ratio feedback correction coefficient LAMBDA changes at a large rate. It can quickly control the air-fuel ratio to the stoichiometric air-fuel ratio, which is the target air-fuel ratio, and as shown in Figure 9, it can suppress air-fuel ratio fluctuations due to the influence of exhaust pressure in the low Q region as soon as possible during deceleration driving at high altitudes. The air-fuel ratio can be controlled to the target air-fuel ratio.

On the other hand, when the air-fuel ratio is rich (VO2>VR):F), the process proceeds from step 64 to step 69, where it is determined whether or not it is the time of reversal from lean to rich.When the air-fuel ratio is reversed, the process proceeds to step 70, where the current state is determined. After storing the value of LAMBDΔ as b (upper peak value), the process proceeds to step 71, where the feedback correction coefficient LAMBDA is decreased by the value obtained by multiplying the proportional bone P set to the previous value by the coefficient K. Otherwise, the process proceeds to step 72, where the feedback correction coefficient LAMBDA is decreased by the value obtained by multiplying the integral I set to the previous value by the coefficient K, thereby decreasing the feedback correction coefficient LAMBDA at a constant slope. At this time, as well as when the air-fuel ratio is determined to be lean, when the coefficient K is set larger than normal, the slope of the change is large, the responsiveness of feedback control becomes large, and the Rich avoidance control can be performed.

In addition, by increasing the control constant by the coefficient K,
The air-fuel ratio can be controlled to the target air-fuel ratio, but if this state is learned and the learning correction coefficient KLRN is set, the air-fuel ratio can be controlled to the target air-fuel ratio by the learning correction coefficient KLRH even if the air-fuel ratio feedback correction coefficient LAMBD is not set. The air-fuel ratio feed adjustment coefficient LAMBD
Since the average value LAMBDA of A settles around the reference value, LAMBDAζ1 is determined in step 26 in FIG. 5, the coefficient K is set to 1.0, and the routine returns to the proportional-integral control.

In this way, the air-fuel ratio feedback correction coefficient LAM
After setting the BDA, proceed to step 73 and calculate the average value of the latest value a at the time of reversal from rich to lean stored in step 66 and the latest value a at the time of reversal from lean to rich stored in step 70. Calculate (a+b)/2.

This average value (a+b)/2 is the control center value of the air-fuel ratio feedback correction coefficient LAMBDA, and is used for determination in step 26 of the routine shown in the flowchart of FIG.

As described above, in the low QTJ region where atmospheric pressure changes are large and the influence of this atmospheric pressure change is large, the air-fuel ratio feedback correction coefficient LAMBDA is set to a value that has a deviation from the reference value, thereby achieving the target air pressure. When attempting to control the fuel ratio, increasing the control constants (proportional bone and integral) in the proportional integral control of the air-fuel ratio feedback correction coefficient LAMBDA increases the responsiveness of the air-fuel ratio feedback control, and improves the air-fuel ratio. Since the engine can be controlled to the target air-fuel ratio as quickly as possible, driving stability in low Qeff ranges such as idling at high altitudes is improved, and engine stalling during deceleration at high altitudes can be avoided. .

<Effects of the Invention> As explained above, according to the present invention, when the atmospheric pressure is changing at a rate higher than a predetermined rate, the control constant in the proportional-integral control of the feedback correction value is increased. Since air-fuel ratio fluctuations in the engine can be avoided as quickly as possible by feedback control, there is an effect that driving stability can be improved, especially in low Q ranges such as idling at high altitudes.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the structure of the present invention, Fig. 2 is a block diagram showing the structure of an embodiment of the present invention, and Figs. 3 to 5 and 8 are the same as above. Flowcharts showing various control routines of the embodiment, FIGS. 6 and 7 are graphs showing various control areas in the control routine shown in the flowchart of FIG. 5, and FIG. 9 shows details of conventional problems and the present invention. It is a time chart for explanation. 1...II section 7...Throttle valve 8...
Throttle sensor 9... Intake pressure sensor 10.
・・Fuel injection resistance 11・・Control unit
12...Water temperature sensor 14...Oxygen sensor
15... Crank angle sensor patent applicant Fujio Sasashima, agent of Japan Electronics Co., Ltd., patent attorney Figure 5 5TART Q flat? No szz ES Nyoichi Kamae 523 YES? O head 'FLPB - fire, repulsion. Figure 6 Group Bo leap times 9 pitches N Figure 7 Sailiang (Kan times Ossoji force LN

Claims (1)

[Scope of Claims] Engine operating state detection means for detecting an engine operating state including at least engine rotational speed and intake pressure; A basic fuel injection amount setting means for setting the injection amount, an air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture, and an actual air-fuel ratio by comparing the air-fuel ratio detected by the air-fuel ratio detection means with a target air-fuel ratio. feedback correction value setting means for setting a feedback correction value for correcting the basic fuel injection amount by proportional-integral control so as to bring the air-fuel ratio of the air fuel ratio closer to the target air-fuel ratio; and atmospheric pressure detection means for detecting atmospheric pressure. control constant increase correction means for increasing a control constant in proportional-integral control of the feedback correction value by the feedback correction value setting means when the atmospheric pressure detected by the atmospheric pressure detection means is changing at a rate equal to or higher than a predetermined rate; a fuel injection amount setting means for setting the fuel injection amount based on the basic fuel injection amount and the feedback correction value; and a fuel injection amount setting means for driving and controlling the fuel injection means according to the fuel injection amount set by the fuel injection amount setting means. An electronically controlled fuel injection device for an internal combustion engine, comprising: an injection control means;