JPH04194349A - Intake air quantity detector of internal combustion engine with supercharger - Google Patents

Abstract

PURPOSE:To enable an intake air quantity to be compensatingly controlled by the minimum number of sensors by correctively setting the intake air quantity based on a variation amount of charged intake air quantity inside a charging chamber between a compressor and a throttle valve estimated based on supercharging pressure. CONSTITUTION:An intake air quantity of an internal combustion engine 2 is directly detected by an air flow meter upstream from a compressor 6. Supercharging pressure by an exhaust turbocharger 1 is directly detected by a supercharging pressure sensor 21 between an intercooler 19 and a throttle valve 12. A variation amount of a charging air quantity inside a supercharging chamber 22 between the compressor 6 and the throttle valve 12 is estimated based on the supercharging pressure detected the supercharging pressure sensor 21. The intake air quantity detected by an air flow meter 11 is correctively set based on the estimated result. Consequently, an intake air quantity detected error at the transient time particularly in the system provided with the intercooler 19 can be compensated with good response. The compensating control is performed by the minimum number of the sensors.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an intake air amount detection device for a supercharged internal combustion engine, and more specifically, to detect transient air flow in a supercharged internal combustion engine, particularly an engine equipped with an intercooler. The present invention relates to a technology for suppressing the occurrence of errors in detecting intake air amount.

<Prior art> Conventionally, in control devices that electronically control the amount of fuel supplied to an internal combustion engine, an air flow meter that directly detects the intake air amount of the engine has been installed, and based on the intake air amount detected by the air flow meter, A system configured to variably set the fuel supply amount is generally known as the L-JETRO system (see Japanese Patent Laid-Open No. 58-150040, Japanese Patent Laid-Open No. 59-49334, etc.).

<Problems to be Solved by the Invention> By the way, in a naturally aspirated internal combustion engine, if the volume between the air flow meter and the throttle valve is relatively small, the amount of air detected by the air flow meter is equal to or smaller than the air passing through the throttle valve. It almost matches the amount.

On the other hand, in an internal combustion engine equipped with a supercharger, the amount of air filled in the supercharging chamber between the compressor and the throttle valve changes depending on changes in supercharging pressure due to transient operation. For this reason, in a supercharged engine, during transient operation, the air flow meter (AFM) simultaneously detects changes in the amount of air filling the supercharging chamber, and the amount of air actually passing through the throttle valve is different from the amount of air detected by the air flow meter. As shown in FIG. 9, the amount of air differs by the amount of change in the amount of air charged in the supercharging chamber. Therefore, during transient operation of a supercharged engine,
The detection accuracy of the intake air amount deteriorates, and the fuel control accuracy (
Air-fuel ratio control accuracy) deteriorated, causing the air-fuel ratio of the engine intake air-fuel mixture to deviate from the target, which adversely affected driveability and exhaust properties.

In addition, in the acceleration state shown in Fig. 9, when the throttle valve starts to open (initial acceleration), the air in the supercharging chamber is sucked into the intake manifold side, reducing the amount of air charged in the supercharging chamber. Then, there is a delay in the detection of the air flow meter, and the increase control of the fuel supply is delayed, causing the air-fuel ratio to become lean. Then, as the boost pressure rises, the amount of charged air in the supercharging chamber increases, or the air flow meter detects this increased amount of air as the amount of air passing through the throttle valve. or become overrich.

By the way, in supercharged engines equipped with an intercooler for intake air cooling, supercharging pressure control has conventionally been performed based on the supercharging pressure between the intercooler and the compressor. Since such a detection error of an air flow meter is caused by a change in supercharging pressure, consideration was given to detecting the supercharging pressure directly below the compressor and correcting the detected value of the intake air amount based on the change in the supercharging pressure. However, although the supercharging pressure detected directly below the compressor can accurately detect the state of supercharging by the compressor, there is a problem in that it cannot accurately detect changes in the amount of charged air in the supercharging chamber during transients. Ta.

In addition, in a system configured to have multiple turbochargers in each independent intake system and detect the intake air amount at the upstream confluence of these multiple intake systems, air amount correction based on the boost pressure is performed. However, since there are variations in boost pressure for each intake system, there is a problem in that it becomes necessary to provide a boost pressure sensor for each intake system.

The present invention has been made in view of the above problems, and is capable of responsively compensating for transient intake air amount detection errors in a supercharged internal combustion engine, particularly in a system equipped with an intercooler. The purpose is to enable control using the minimum number of sensors.

<Means for Solving the Problems> Therefore, the intake air amount detection device for a supercharged internal combustion engine according to the present invention is configured to include a throttle valve downstream of a compressor of a supercharger, and A supercharged internal combustion engine including an intercooler for cooling intake air between the compressor and the throttle valve is configured as shown in FIG.

In Fig. 1, the intake air amount detection means directly detects the intake air amount of the engine on the upstream side of the compressor, and the supercharging pressure detection means detects the supercharging pressure from the supercharger between the intercooler and the throttle valve. Detect directly between.

The intake air amount correcting means estimates the amount of change in the filling air amount in the supercharging chamber between the compressor and the throttle valve based on at least the supercharging pressure detected by the supercharging pressure detecting means, and Based on the results, the intake air amount detected by the intake air amount detection means is corrected and set.

Here, if a plurality of supercharging intake systems consisting of a compressor, an intercooler, and a throttle valve are branched downstream of the intake air amount detecting means and are arranged in parallel, the supercharging pressure detecting means is connected to each intake system. Preferably, the supercharging pressure is detected as a composite pressure of the pressure between the intercooler and the throttle valve.

<Operation> According to such a configuration, the amount of charged air due to a change in the supercharging pressure in the supercharging chamber between the compressor and the throttle valve is determined based at least on the supercharging pressure detected between the intercooler and the throttle valve. The amount of change in the intake air amount is estimated, and the detected value of the intake air amount is corrected based on the estimation result. Therefore, the amount of filling air in the supercharging chamber changes during a transient period, and the intake air amount detection means includes the amount of change as well. Even if detected, the true engine intake air amount can be determined by correcting the amount.

In addition, since the detected value of boost pressure used when performing correction according to the change in the amount of charged air as described above is detected between the intercooler and the throttle valve, the value upstream of the intercooler The intake air amount can be corrected based on the detected boost pressure value, which responds more sensitively to the movement of the throttle valve during transients than the side boost pressure. I can make corrections.

Furthermore, when a plurality of supercharging intake systems are provided, if the supercharging pressure detection means detects the supercharging pressure as a composite pressure of the pressure between the intercooler and the throttle valve of each intake system, the supercharging pressure can be detected. There is no need to provide means for each intake system.

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

In FIG. 2 showing one embodiment, an internal combustion engine 2 equipped with an exhaust turbocharger 1 as a supercharger rotates an exhaust turbine 4 of the exhaust turbocharger 1 using the energy of exhaust gas discharged through an exhaust passage 3. By doing so, a compressor 6 provided in the intake passage 5 and connected to the exhaust turbine 4 is rotated to supercharge the intake air.

At 22, the intake pressure in the intake passage 5 downstream of the compressor 6 is applied to the diaphragm actuator 8 via the pressure passage 7.
has been introduced into the pressure chamber of The diaphragm actuator 7 controls an exhaust bypass valve (wastegate valve) 10 that opens and closes an exhaust bypass passage 9 provided to bypass the exhaust turbine 3, by controlling the pressure introduced into its pressure chamber (
It is driven to open and close depending on the supercharging pressure.

The control unit 15 includes an intake air flow rate signal Q directly detected by an air flow meter 11 such as a hot wire type installed in the intake passage 5 on the upstream side of the compressor 6;
Throttle valve opening signal TVO detected by a throttle sensor 13 attached to a throttle valve 12 installed in the intake passage 5 downstream of the compressor 6, and engine rotational speed detected by a rotational speed sensor 14 such as a crank angle sensor. Signal N1 A cooling water temperature signal Tw, etc. detected by a water temperature sensor 17 disposed in the water jacket 16 of the engine 2 is input.

The control unit 15 calculates and sets the basic fuel injection amount Tp based on the intake air flow rate Q detected by the air flow meter 11 and the engine rotational speed N detected by the rotational speed sensor 14, and also calculates and sets the basic fuel injection amount Tp. The final fuel injection amount Ti is set by correcting the amount Tp based on the coolant temperature Tw detected by the water temperature sensor 17, etc.

Then, a drive pulse signal with a pulse width corresponding to the fuel injection amount Ti is output to the electromagnetic fuel injection valve 18 at a predetermined timing synchronized with the engine rotation, and the fuel injection valve 18 is operated for a time corresponding to the pulse width. It is intermittently opened and driven to inject and supply fuel to the engine 2.

In FIG. 2, 19 is an intercooler for cooling the intake air supercharged by the exhaust turbocharger l, and 20 is a spark plug provided in each combustion chamber.

Here, on the downstream side of the intercooler 19 and the upstream side of the throttle valve 12, there are provided a supercharging pressure sensor 21 that directly detects the supercharging pressure PB, an air temperature sensor 23 that detects the air temperature TB, and a control unit. Reference numeral 15 indicates the inside of the supercharging chamber 22 provided between the compressor 6 and the throttle valve 12 based on the supercharging pressure PB detected by the supercharging pressure sensor 21 and the air temperature TB detected by the air temperature sensor 23. The air density ρ is set, the change in the filling air amount in the supercharging chamber 22 is estimated based on the change in the air density ρ and the volume of the supercharging chamber 22, and the air flow meter 11 is used based on the estimation result. It is configured to correct the detected intake air flow rate Qa, and based on the data of the intake air flow rate Qs corrected in this way, the basic fuel injection amount Tp is determined.
This is how it is set.

Such correction control of the intake air flow rate Qa will be explained below according to the programs shown in the flowcharts of FIGS. 3 to 6, respectively.

In this embodiment, the function of the intake air amount correcting means is provided in the control unit 15 in the form of software, as shown in the flowcharts of FIGS. 3 to 6. In this embodiment, the intake air amount detection means corresponds to the air flow meter 11, and the boost pressure detection means corresponds to the boost pressure sensor 21.

The flowchart in FIG. 3 shows an overall outline of the correction control of the intake air flow rate Q'a detected by the air flow meter 11.

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

The same applies hereafter), the change Δρ in the air density ρ in the supercharging chamber 22 is based on the supercharging pressure PB detected by the supercharging pressure sensor 21 and the air temperature TB detected by the air temperature sensor 23.
Calculate.

In the next step 2, the intake air flow rate Qa detected by the air flow meter 1 is corrected based on the change in the amount of charged air estimated from the air density change Δρ and the volume of the supercharging chamber 22. Calculate the value Qtc.

Then, in step 3, the intake air flow rate Qa detected by the air flow meter 11 is determined based on the correction value Qtc.
is corrected, and the intake air flow rate Qs thus corrected is set as the final detected value for calculating the basic fuel injection amount Tp.

Next, detailed processing contents in each step 1 to 3 outlined above will be explained below according to the flowcharts of FIGS. 4 to 6.

The details of the air density change Δρ calculation in step 5 and step 1 are shown in the flowchart of FIG.

Here, in step 11, the latest detection values PB, TB, of the boost pressure and air temperature detected by the boost pressure sensor 21 and the air temperature sensor 23, respectively, are read.

In step 12, based on the reference boost pressure P, reference air temperature T, and reference air density ρ, the air density ρ1 at the current boost pressure PB1 and air temperature T B + is calculated according to the following formula.

Then, in step 13, the air density ρ1 calculated this time in step 12 and the air density ρ similarly calculated in step 12 during the previous execution of this program. Which difference is the air density change Δρ per program execution cycle?
(=ρ1−ρ.) is calculated.

Here, since the supercharging pressure sensor 21 detects the supercharging pressure PB between the intercooler 19 and the throttle valve 12, it can detect the air density change Δρ during transient operation with good responsiveness. That is, intercooler 19
If the boost pressure is detected on the upstream side of the compressor 6, check whether it is suitable for detecting the supercharging state by the compressor 6 or buffer pressure changes between the throttle valve I2 and the boost pressure sensor. Since the intercooler 19 is involved, as shown in FIG. 7, there is a delay in the detection response to the pressure change in the supercharging chamber 22 in response to the change in throttle valve opening at the initial stage of the transition.

On the other hand, if the configuration is such that the supercharging pressure is detected between the intercooler 19 and the throttle valve 12 as in this embodiment, the pressure change in the supercharging chamber 22 due to the change in the opening of the throttle valve 12 will be detected by the intercooler 19 and the throttle valve 12. Since it occurs early on the downstream side of the cooler 19, changes in supercharging pressure during transient operation can be detected with good response.

Therefore, in a supercharging system including an intercooler 19 as in this embodiment, the air density change Δ in the supercharging chamber 22 is
ρ can be detected with good responsiveness, and the intake air amount correction, which will be described in detail later, can be performed with good responsiveness.

In step 14, it is determined whether the air density change Δρ calculated in step 13 is positive or negative. Here, if the air density change Δρ is a positive value and the air density ρ is increasing, the process proceeds to step 15 and the flag Flugdp is set to 1.
is set, or the air density change Δρ is a negative value,
When the air density ρ is decreasing, step 16
Proceed to and set the flag Flugdp to 0. On the other hand, if the air density change Δρ is determined to be approximately zero in step 14, and the air density ρ is approximately constant, then step 1
7 and sets the flag Flugdp to 1,
In step 18, the correction value Qtc is set to zero to cancel the correction of the intake air flow rate Qa.

That is, when the air density ρ in the supercharging chamber 22 is changing, while the amount of air filling in the supercharging chamber 22 is changing,
Although an error occurs in the detected value by the air flow meter 11,
When the air density ρ in the supercharging chamber 22 is constant, the filling air amount is constant and matches the air amount detected by the air flow meter 11 or the air amount passing through the throttle valve 12, so no correction is performed. .

The calculation of the correction value Qtc corresponding to step 2 in the flowchart of FIG. 3 is shown in the flowchart of FIG.

In the flowchart of FIG. 5, in step 21,
A correction value Qtc is calculated according to the following formula.

Qtc=lΔD I By multiplying the change Δρ, a correction value Qtc corresponding to a change in the amount of air filled in the supercharging chamber 22 per unit time can be obtained.

Next, based on the correction value Qtc, the air flow meter 11
The correction of the detected value Qa will be explained according to the flowchart of FIG.

First, in step 41, the flag Flugdp, which is set based on the direction of air density change in the flowchart of FIG. 4, is determined.

Here, when it is determined that the flag Flugdp is set to zero, it means that the air density ρ is increasing,
At this time, the air flow meter 11 also detects the amount of air that actually increases the amount of charged air in the supercharging chamber 22, and the air flow meter 11 detects the amount of air that is actually an increase in the amount of charged air in the supercharging chamber 22. is being detected, the process proceeds to step 32, where a correction value Qtc corresponding to the increase in the amount of charged air is subtracted from the detected value Qa, and the result of the subtraction is set as the final detected value Qs.

On the other hand, when it is determined in step 31 that the flag Flugdp is set to 1, the air density ρ is in a decreasing state, and at this time, the decrease in the amount of filling air in the supercharging chamber 22 is also equal to the amount of air passing through the throttle valve. However, since the air flow meter 11 does not detect the decrease in the amount of filled air,
Proceeding to step 33, a correction value Qtc corresponding to the decrease in the amount of filled air is added to the detected value Qa, and the addition result is set as the final detected value Qs.

The basic fuel injection amount Tp is calculated based on the intake air flow rate Qs corrected in step 32 or step 33, and the fuel injection valve 18 is drive-controlled based on this basic fuel injection amount Tp, and the fuel supply amount is calculated electronically. It will be controlled.

In this way, the detected value Qa of the air flow meter 11 is corrected based on the change in the filling air amount in the supercharging chamber 22 predicted from the air density change Δρ in the supercharging chamber 22 and the volume of the supercharging chamber 22. Then, even if an error occurs in the detected value Qa of the air flow meter 11 during engine transients when the charged air amount changes, it is possible to compensate for this and set the true amount of air passing through the throttle valve 12. , it is possible to improve the accuracy of fuel supply control based on air amount detection.

In the above embodiment, the engine 2 is provided with one system of supercharging intake systems, but for example, in a V-type machine, each bank is provided with an independent supercharging intake system,
In a system including an air flow meter 11 at the upstream confluence of the supercharging silver absorption systems for each bank, the supercharging pressure is detected as shown in FIG. It is preferable to correct the intake air amount based on the change.

In FIG. 8, the intake passage is branched into two systems downstream of the air flow meter 11, and each production system includes a compressor 6, an intercooler 19. A throttle valve 12 is provided for each, and air is sent to one bank of the engine 2 independently.

Here, pressure introduction pipes 2 are branched and extended from between the intercooler 19 and the throttle valve 12 of each intake system.
4 are combined and connected to a supercharging pressure sensor 21, and the supercharging pressure sensor 21 detects the supercharging pressure as a combined pressure in the two supercharging intake systems.

In this way, the supercharging pressure of each intake system is combined and the supercharging pressure sensor 2
1, it is not necessary to provide separate sensors for each bank, which saves the number of sensors.As shown in FIG.
By detecting the composite pressure, it is possible to reduce the pulsation of the detected supercharging pressure value.

If the configuration is configured to detect the combined pressure of both banks as described above, the pressure introduction pipe 24 that leads the boost pressure to the boost pressure sensor 21 will become long. Since the supercharging pressure that responds to the movement of the throttle valve 12 with good responsiveness is detected on the downstream side of the intercooler 19, the delay due to the length of the pressure introduction pipe 24 is compensated for, and necessary and sufficient responsiveness is achieved. It is possible to ensure that

In this embodiment, an engine equipped with an exhaust turbocharger l as a supercharger has been described, but the supercharger may be a supercharger that is directly driven by the engine.

In addition, in this embodiment, based on the supercharging pressure PB and air temperature TB detected between the intercooler 19 and the throttle valve 12, the change in the amount of charged air in the supercharging chamber is estimated or the supercharging The change in the amount of filled air may be estimated based only on the pressure.

<Effects of the Invention> As explained above, according to the present invention, in a supercharged internal combustion engine equipped with an intercooler, the detection error of the intake air amount due to changes in boost pressure is estimated, and based on the estimation result, Since the detected value is corrected, the detection accuracy of the intake air amount during transient times is improved, and since the detected value of the boost pressure used for the correction can be obtained with good responsiveness, the correction control is Responsiveness can be ensured.

Furthermore, when a plurality of supercharging intake systems are branched downstream of the intake air amount detecting means and are arranged in parallel, there is no need to detect the supercharging pressure individually, and the number of sensors can be reduced.

[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 an embodiment of the present invention, and Figs. 3 to 6 show intake air based on changes in boost pressure in the above embodiment. FIG. 7 is a time chart showing the detection characteristics of boost pressure in the above embodiment. FIG. 8 is a system schematic diagram showing another embodiment of the present invention. 3 is a time chart for explaining problems with conventional intake air amount detection control. 1...Exhaust turbocharger 2...Internal combustion engine 4
...Exhaust turbine 6...Compressor 11...
・Air flow meter 12...Throttle valve 15・
...Control unit 19...Intercooler 21...Supercharging pressure sensor 22...Supercharging chamber
23... Air temperature sensor patent applicant Fujio Sasashima Patent attorney Representative of Japan Electronics Co., Ltd. Figure 3 Figure 5 ' Figure 6 Figure 4

Claims (2)

[Claims] (1) A supercharged internal combustion engine configured with a throttle valve downstream of a compressor of a supercharger, and an intercooler for cooling supercharged intake air between the compressor and the throttle valve. The intake air amount detection device includes an intake air amount detection means for directly detecting the intake air amount of the engine on the upstream side of the compressor, and a supercharging pressure from the supercharger between the intercooler and the throttle valve. a supercharging pressure detecting means that directly detects the supercharging pressure; and estimating a change in the amount of charged air in the supercharging chamber between the compressor and the throttle valve based on at least the supercharging pressure detected by the supercharging pressure detecting means. , intake air amount correction means for correcting and setting the intake air amount detected by the intake air amount detection means based on the estimation result, and an intake air amount correction means for an internal combustion engine with a supercharger. Air amount detection device. (2) The supercharging intake system consisting of the compressor, intercooler, and throttle valve is branched downstream of the intake air amount detection means and is arranged in parallel, and the supercharging pressure detection means is connected to the interface of each intake system. 2. The intake air amount detection device for a supercharged internal combustion engine according to claim 1, wherein the device is configured to detect supercharging pressure as a composite pressure of pressures between the cooler and the throttle valve.