JPH08326595A - Excess air ratio detecting device for engine and exhaust gas recirculation control device - Google Patents

Abstract

PURPOSE: To perform rapid detection of an excess air ratio by a method wherein based on a detecting intake air amount, an excess air ratio estimated the given number of times beforehand, and an exhaust gas reflux amount, an equivalent intake fresh air amount is estimated and based on the equivalent intake fresh air amount and a fuel feed amount, the excess air ratio of an engine is estimated. CONSTITUTION: In an ECU 8, during operation of an engine 1, a intake air pressure is measured by an intake air pressure sensor 17, and from the intake air pressure, a fuel feed amount, and an engine rotation speed, an intake air amount is calculated. Meanwhile, after an exhaust gas pressure is directly measured by an exhaust pressure sensor or based on other parameter, estimation is effected, from a differential pressure between an exhaust pressure and an intake pressure, and an opening amount of an EGR valve 31 by an EGR position sensor 36, an EGR amount is estimated. From a determined intake air amount and an EGR amount and an excess air ratio a few processes before, an equivalent intake fresh air amount is estimated. From the equivalent intake fresh air amount and a differently detecting fuel feed amount, an excess air ratio is estimated, and according to the excess air ratio, a fuel injection amount is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine excess air ratio detection device and an exhaust gas recirculation control device used in a fuel supply system and an exhaust purification system of a diesel engine for automobiles.

[0002]

2. Description of the Related Art The main harmful emission components of diesel engines are black smoke and unburned HC due to uneven fuel distribution.
In addition to the above, NO _X due to combustion under high temperature can be mentioned. As a NO _X reducing means in a diesel engine, a reduction catalyst such as a gasoline engine cannot be applied because of a large amount of excess oxygen, and delay of fuel injection timing (timing retard) and water injection have been studied. However, the former cannot avoid reduction in output and fuel consumption and increases in CO and HC, and the latter has problems such as mounting a water injection device or a water tank and mixing water into lubricating oil. Therefore, an exhaust gas recirculation (EGR) device that recirculates exhaust gas, which is an inert substance, as EGR gas into the combustion chamber is being put into practical use because of its relatively simple structure and less harmful effects.

In an EGR device for a diesel engine,
If the recirculation amount of EGR gas (hereinafter, referred to as EGR amount) becomes excessive, deterioration of smoke due to decrease of excess air ratio, rapid increase of HC, decrease of fuel consumption, and engine oil due to mixing of free carbon and particulates The deterioration causes deterioration of engine durability. Therefore, in order to reduce NO _X while suppressing these problems as much as possible, it is desirable to use an electronic control system that detects the excess air ratio and feedback-controls the EGR amount. As a method of detecting the excess air ratio, a method using a CO ₂ analyzer and a linear air-fuel ratio sensor (hereinafter referred to as LA
A method using FS) is generally used.

However, as is well known, since the CO ₂ analyzer has a large size and weight, it can be used for a bench test or the like, but it is not realistic for a vehicle. On the other hand, L
An EGR device using an AFS is disclosed in JP-A-55-79.
64 and Japanese Patent Laid-Open No. 63-201356. In the former EGR device, LA is used in the exhaust system.
When the FS is attached and the output current exceeds a predetermined threshold value, the EGR valve is driven in the opening direction, and when the output current is below the predetermined threshold value, the EGR valve is driven in the closing direction. Further, in the latter EGR device, the EG based on the control map of the EGR amount with the lever opening of the fuel injection pump and the engine rotation speed as parameters.
LAFS attached to the exhaust system while driving the R valve
Thus, the EGR valve opening degree (control map) is corrected.

[0005]

However, these LAs
EGR for feedback control of EGR amount using FS
The device also had the following problems. For example, LAF
Since S is attached to the exhaust system, a transfer delay occurs before the exhaust gas reaches LAFS even if the excess air ratio actually changes. The LAFS has a structure that outputs a current according to the excess air ratio according to the principle of the oxygen concentration battery, and it takes time for the gas to reach the sensor element through the protective tube, so that the excess air ratio changes. The response itself to is low. Therefore, during acceleration or deceleration where the excess air ratio changes abruptly, as shown in FIG. 5, a delay (usually a dozen or more strokes) occurs before the LAFS detects the change in the excess air ratio. Note that FIG. 5 shows the case where the fuel injection amount is rapidly increased, the solid line shows the actual change in excess air ratio, and the two-dot chain line shows L.
The detection result by AFS is shown. Therefore, EG
Naturally, there was a delay in the control of the R device, and there was a problem that the NO _x emission amount or the black smoke emission amount increased. In particular, immediately after acceleration, where black smoke is easily emitted, there is a problem that the exhaust amount of black smoke further increases due to an excessive amount of EGR.

Further, in the diesel engine, since the exhaust gas contains a large amount of free carbon and particulates, the LAFS is contaminated in a short period of time, and there is a problem that the current corresponding to the excess air ratio is not output. Therefore, the detection accuracy gradually deteriorates, and the EGR amount cannot be controlled accurately. In addition to the high initial cost, LAFS itself is an expensive component, and the running cost due to regular inspection and replacement is also high. There was also the problem of becoming expensive.

The present invention has been made in view of the above circumstances, and uses an excess air ratio detecting device and its principle capable of quickly detecting the excess air ratio of a diesel engine or the like while adopting a relatively simple and inexpensive device structure. The present invention aims to provide a conventional exhaust gas recirculation control device.

[0008]

Therefore, according to claim 1 of the present invention, the exhaust gas recirculation device for the engine is supplied to the engine mounted on the vehicle while the exhaust gas recirculation device is operating based on the operating state of the engine. In an excess air ratio detecting device for repeatedly detecting the excess air ratio of the air-fuel mixture, an intake pressure detecting means for detecting the intake pressure of the engine, an exhaust pressure detecting means for detecting the exhaust pressure of the engine, and the intake pressure. Exhaust gas recirculation amount estimation means for estimating the recirculation amount of exhaust gas by the exhaust gas recirculation device based on the intake pressure detected by the detection means and the exhaust pressure detected by the exhaust pressure detection means, and the exhaust gas An intake air amount detection means for detecting the intake air amount of the engine including the exhaust gas recirculation amount by the recirculation device, and an intake air amount detected by the intake air amount detection means. Equivalent intake for estimating the equivalent intake fresh air amount of the engine based on the amount, the excess air ratio previously estimated a predetermined number of times, and the exhaust gas recirculation amount estimated by the exhaust gas recirculation amount estimating means. Fresh air amount estimating means, fuel supply amount detecting means for detecting the fuel supply amount of the engine, fuel supply amount detected by the fuel supply amount detecting means, and equivalence estimated by the equivalent intake fresh air amount estimating means An air excess ratio estimating means for estimating the excess air ratio of the engine based on the intake fresh air amount is proposed.

According to a second aspect of the present invention, in the air excess ratio detecting device according to the first aspect, the intake amount detecting means detects the intake amount based on the intake pressure detected by the intake pressure detecting means. suggest. According to a third aspect of the present invention, in the excess air ratio detection device according to the first or second aspect, the engine has a turbocharger, and the exhaust gas recirculation amount estimating means is based on the exhaust pressure upstream of the turbo. A method for estimating the exhaust gas recirculation amount is proposed.

According to a fourth aspect of the present invention, in the excess air ratio detecting device according to the first to third aspects, the exhaust pressure detecting means obtains a steady value of the exhaust pressure from the engine speed and the fuel supply amount, and the exhaust pressure is the same. The turbine acceleration pressure is calculated from the steady-state value and the exhaust gas recirculation amount and the intake amount several strokes before, and the load is obtained from the turbine acceleration pressure and the exhaust pressure steady-state value. It is proposed that the present value of the exhaust pressure is obtained from the acceleration pressure and the load.

According to a fifth aspect of the present invention, in the excess air ratio detection device according to the first to fourth aspects, the exhaust gas recirculation amount estimation means estimates the exhaust gas recirculation amount based on the valve opening degree of the exhaust gas recirculation device. Suggest what to do. Moreover, in Claim 6, in the air excess ratio detection apparatus of Claims 1-5,
The exhaust gas recirculation amount estimating means obtains an orifice coefficient from a pressure difference between exhaust pressure and intake pressure, obtains a recirculation exhaust gas temperature coefficient from an engine rotation speed and a fuel supply amount, and determines a valve of the exhaust gas recirculation device. It is proposed to estimate the exhaust gas recirculation amount from the opening degree, the throttling coefficient of the exhaust gas recirculation device, the orifice coefficient, and the recirculation exhaust gas temperature coefficient.

According to a seventh aspect of the present invention, in the excess air ratio detecting device according to any of the first to sixth aspects, the equivalent intake fresh air amount estimating means determines the recirculation amount of the exhaust gas from the intake amount as the excess air ratio. We propose to estimate the equivalent fresh air intake by subtracting the divided value. Further, in claim 8, the air excess ratio detecting device according to any one of claims 1 to 7 proposes that the excess air ratio estimating means estimates the excess air ratio for each stroke of the engine.

According to a ninth aspect of the present invention, the exhaust gas recirculation control device for controlling the valve opening amount of the exhaust gas recirculation device of the engine is supplied to the engine based on the operating state of the engine mounted on the vehicle. Excess air ratio detecting means for detecting an excess air ratio of the air-fuel mixture, target air excess ratio setting means for setting a target air excess ratio of the air-fuel mixture supplied to the engine, the air excess ratio and the target air excess. Rate setting means for setting a target valve opening amount of the exhaust gas recirculation device so that there is no deviation from the rate, and a drive control device for driving and controlling the exhaust gas recirculation device based on the target valve opening amount. Propose one with and.

According to a tenth aspect of the present invention, in the exhaust gas recirculation control device according to the ninth aspect, the target excess air ratio setting means sets the target excess air ratio based on the engine speed and the fuel supply amount. To propose. According to claim 11, in the exhaust gas recirculation control device according to claim 9 or 10, the valve opening amount setting means sets the valve opening amount by at least proportional integral control, and the absolute value of the deviation is set. If the value is larger than a predetermined value, it is proposed that the integral term in the proportional-plus-integral control is not integrated.

[0015]

In the excess air ratio detecting device of the present invention, after the intake pressure detecting means directly measures the intake pressure by the intake pressure sensor, the intake amount detecting means detects the intake pressure from the intake pressure, the fuel supply amount and the engine rotation speed. Calculate the amount. On the other hand, the exhaust pressure detecting means directly measures the exhaust pressure by the exhaust pressure sensor or estimates it based on other engine parameters, and then the exhaust gas recirculation amount estimating means determines the exhaust gas recirculation amount and the differential pressure between the exhaust pressure and the exhaust gas. The exhaust gas recirculation amount is estimated from the valve opening amount of the recirculation device. Next, the equivalent intake fresh air amount estimating means estimates the equivalent intake fresh air amount from the calculated or estimated intake air amount and exhaust gas recirculation amount and the excess air ratio several strokes ago, and the excess air ratio estimating means The excess air ratio is estimated from the equivalent intake fresh air amount and the fuel supply amount detected by the fuel supply amount detecting means.

Further, in the excess air ratio detecting device of the second aspect, the intake air amount detecting means performs the volumetric efficiency correction and the intake air temperature correction on the product of the intake pressure and the exhaust gas amount per cylinder to determine the intake air amount. To detect. Further, in the excess air ratio detecting device according to claim 3, the exhaust gas recirculation amount estimating means obtains a differential pressure between the exhaust pressure upstream of the turbo and the intake pressure, and multiplies the differential pressure by another control parameter to exhaust gas. Estimate the amount of reflux.

Further, in the excess air ratio detecting device of the fourth aspect, the exhaust pressure detecting means divides the turbine acceleration pressure minus the load by the turbine inertia coefficient, and adds this to the previous value of the exhaust pressure. , Exhaust pressure is detected. Further, in the excess air ratio detection device of claim 5, the exhaust gas recirculation amount estimation means detects the valve opening degree of the exhaust gas recirculation device,
The exhaust gas recirculation amount is estimated by multiplying this valve opening by another control parameter.

Further, in the excess air ratio detecting device of the sixth aspect, the exhaust gas recirculation amount estimating means multiplies the orifice coefficient by the valve opening degree of the exhaust gas recirculation device, and multiplies this by the throttling coefficient, the exhaust gas temperature coefficient, etc. The exhaust gas recirculation amount is estimated by further multiplying by. Further, in the excess air ratio detecting device of claim 7, the equivalent intake fresh air amount estimating means calculates the amount of inert gas in the recirculated exhaust gas by dividing the exhaust gas recirculation amount by the excess air ratio of several strokes ago. , The equivalent intake fresh air amount is estimated by subtracting that value from the intake amount.

Further, in the excess air ratio detecting device of the eighth aspect, the excess air ratio estimating means estimates the excess air ratio based on the output signal from the crank angle sensor or the like, for example, at the start of the intake stroke of each cylinder. To do. Further, in the exhaust gas recirculation control device according to claim 9, the deviation between the detected excess air ratio and the target excess air ratio is obtained, and if the current state is rich, the valve opening amount of the exhaust gas recirculation device is reduced. Increase fresh air,
On the contrary, in the lean state, the valve opening amount of the exhaust gas recirculation device is increased to reduce the fresh air amount.

Further, in the exhaust gas recirculation control device according to the tenth aspect, the target excess air ratio setting means sets the target excess air ratio on the basis of a map having the engine speed and the fuel supply amount as parameters, for example. Further, in the exhaust gas recirculation control device according to claim 11, the valve opening amount setting means stops integration of the integral term when the absolute value of the deviation is larger than a predetermined value, and the absolute value of the integral term does not become excessive. To do so.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an excess air ratio detection device and an exhaust gas recirculation control device according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an engine control system to which an EGR device is attached, in which FIG. 1 shows an in-line four-cylinder diesel engine engine (hereinafter simply referred to as engine) for an automobile. A swirl chamber 3 is formed in the cylinder head 2 of the engine 1, and
A fuel injection nozzle 4 for injecting fuel into the swirl chamber 3 is attached to each cylinder. A distributed fuel injection pump 6 having an electronic governor 5 is attached to the engine 1, and supplies fuel to each fuel injection nozzle 4 via a fuel injection pipe 7. The fuel injection pump 6 is driven by a crankshaft (not shown) of the engine 1 and
The electronic governor 5 controlled by the CU (engine control unit) 8 sets the fuel injection timing and injection period. In the figure, 9 is attached to the cylinder head 2 and the cooling water temperature Tw
Is a water temperature sensor for detecting the
Ne attached to the engine to detect the engine speed Ne
It is a sensor.

An intake pipe 12 for introducing fresh air from an air cleaner (not shown) is connected to the cylinder head 2 via an intake manifold 11, and a compressor 14 of a turbocharger 13 and an intake pipe 12 are connected in the pipe line. A cooler 15 is provided. In the figure, 16 is an intake air temperature sensor that detects the intake air temperature Ta, and 17 is an intake pipe pressure (Manifold Absolut
e Pressure) A boost pressure sensor that detects Pb,
Both are attached to the intake manifold 11. A turbine 21 of the turbocharger 13 and an exhaust pipe 22 are connected to the cylinder head 2 via an exhaust manifold 20. In the figure, 23 is a wastegate valve that allows exhaust gas to escape from the exhaust manifold 20 to the downstream of the turbine 21 when the boost pressure is excessively increased, and 24 is a wastegate actuator. Further, 25 is an oxidation catalyst for purifying CO and HC in the exhaust gas.

On the other hand, the exhaust manifold 20 of the engine 1
The intake manifold 11 and the intake manifold 11 are communicated with each other through an EGR pipe 30, and the conduit of the EGR pipe 30 is a valve body 32 of an EGR valve 31 provided on the intake manifold 11 side.
It is designed to be opened / closed by. EGR valve 3
Reference numeral 1 denotes a negative pressure actuating type, which includes a valve body 32, a diaphragm 33, a return spring 34, and a negative pressure chamber 35. In the figure, 36 is an EGR position sensor for detecting the opening A _E of the EGR valve 31.

The negative pressure chamber 35 of the EGR valve 31 is connected to the hose 4
It is connected to the vacuum pump 43 through 0 and 41 and the negative pressure side EGR solenoid 42, and is connected to the atmosphere through the hose 44 and the atmosphere side EGR solenoid 45. The vacuum pump 43 is driven by the rotating shaft of the alternator 46 and constantly generates a negative pressure while the engine 1 is operating. The negative pressure side EGR solenoid 42 communicates the hoses 40 and 41 in the ON state, and connects the hoses 40 and 4 in the OFF state.
Cut off 1. In addition, the atmosphere side EGR solenoid 45 is O
The hose 44 communicates with the atmosphere in the FF state, and shuts off the hose 44 in the ON state. Therefore, both EGR solenoids 4
By turning 2, 45 on or off as appropriate,
Negative pressure or the atmosphere is introduced into the negative pressure chamber 35 of the EGR valve 31, and the opening A _E of the EGR valve 31 is controlled.

The above-mentioned ECU 8 is installed in the passenger compartment, and includes an input / output device (not shown), a storage device (ROM, RAM, etc.) containing a control program, and a central processing unit (CP).
U) etc. On the input side of the ECU 8, detection information from various sensors and switches including the above-mentioned sensors is input, and the ECU 8 starts the electronic governor 5 and both EGRs based on the detection information and the control map. The drive control of the solenoids 42, 45 and the like is performed.

The procedure for detecting the excess air ratio and the control procedure for the EGR device in this embodiment will be described below. The driver turns on the ignition key to start the engine 1, and a predetermined control condition (in this embodiment, the water temperature TW is 70
℃ or more, 30 seconds or more after starting, boost pressure sensor 17
And that the EGR position sensor 36 is normal), the ECU 8
The excess air ratio detection subroutine shown in the flowchart of FIG. 2 is repeatedly executed. When this subroutine is started, the ECU 8 firstly proceeds to step S2, where the intake air temperature sensor 1
Based on the outputs of 6 and the boost pressure sensor 17, etc., the current total intake air amount Q _{IN (i)} (g / st) sucked into the engine 1 is calculated by the following equation. In the following formula, Pb is the intake pipe pressure (mmH
₂ O), V is the displacement per cylinder (l), and K _VE is the engine speed Ne (rpm) and intake pipe pressure P.
It is a volumetric efficiency correction coefficient obtained from a map not shown based on b, and Ta is the intake air temperature (° C) Q _{IN (i)} = (Pb / 760) ・ V ・ K _VE・ 1.2 ・ (293 / (273 + T
a)) Next, in step S4, the ECU 8 searches the turbine upstream pressure steady value P _TO from a map (not shown) based on the engine rotation speed Ne and the fuel injection amount Qf, and then in step S6.
Then, the turbine upstream pressure P _{T (i)} of this time is calculated by the following procedure.

In calculating the turbine upstream pressure P _{T (i)} ,
The ECU 8 first calculates the turbine acceleration pressure PA by the following formula. In the following equation, Q _{E (i-3)} and Q _{IN (i-3)} are the EGR amount and the total intake amount before three strokes, respectively. PA = P _TO · (1-Q _{E (i-3)} / Q _{IN (i-3)} ) Next, the ECU 8 calculates the load PL from the turbine acceleration pressure PA and the turbine upstream pressure steady value P _TO by the following equation. Calculate by

PL = PA ² / P _TO Finally, the ECU 8 uses the previous value P _{T (i-1)} , the turbine acceleration pressure PA and the load PL to calculate the turbine upstream pressure P _{T (i)} by the following equation. calculate. In the following formula, I _T is a turbine inertia coefficient. _{P T (i) = P T} (i-1) + in the (PA -PL) / I _T Thus, when obtaining the turbine upstream pressure P _{T (i),} E
In step S8, the CU 8 determines the current EGR amount Q _{E (i)} (g / s
t) is calculated by the following formula. In the following equation, A _E is the opening degree (%) of the EGR valve 31 detected by the EGR position sensor 36, Ks is the throttle coefficient (constant value), and K _O
Is the pressure difference ΔP between the turbine upstream pressure P _{T (i)} and the intake pipe pressure Pb.
Is an orifice coefficient retrieved from a map (not shown) based on the above, and K _ET is the engine speed Ne and the fuel injection amount Q.
It is an EGR temperature coefficient retrieved from a map (not shown) based on f.

[0029] When obtaining the _{Q E (i) = A E} · Ks · K O · K ET · 60 / (2 · Ne) EGR quantity Q _{E (i),} ECU 8 is, then the total intake air amount Q in step S10 Equivalent intake fresh air amount Qa _(i) is calculated by converting _{IN (i)} into fresh air. Here, λ _(i-3) is the estimated excess air ratio three strokes ago, and is set to a predetermined value (for example, 1.2) from the start of the subroutine to the second processing (that is, the second stroke). ing.

Qa _(i) = QIN _(i) -QE _(i) / λ _(i-3) Next, the ECU 8 controls the equivalent intake fresh air amount Qa _(i) thus obtained and the fuel. Based on the injection amount Qf, step S12
Then, the estimated excess air ratio λ _(i) at this time is calculated. Where 1
4.5 is the theoretical air-fuel ratio of the diesel engine. _{λ (i) = Qa (i} ) / (Qf · 14.5) Next, ECU 8, the estimated excess air rate stored in the RAM by using the estimated excess air ratio of the current lambda _(i) in step S14 lambda _(i) , Λ _(i-1) , λ _(i-2) ... are updated, and then the process returns to the start and the detection of the excess air ratio is repeated. When the detected estimated excess air ratio λ _(i) is less than or equal to the target λ,
The ECU 8 uses an EG described later to suppress the emission of black smoke.
In the R control subroutine, the EGR valve 31 is driven in the closing direction to increase the equivalent intake fresh air amount Qa _{(i). In the} fuel injection control subroutine not described here, the electronic governor 5 is also driven to control the fuel injection amount. It suppresses the increase of Qf.

On the other hand, in parallel with the excess air ratio detection subroutine, the ECU 8 executes the EGR control subroutine shown in the flowcharts of FIGS. When this subroutine is started, the ECU 8 firstly executes step S20.
Then, after the current estimated excess air ratio λ _(i) obtained by the excess air ratio detection subroutine is read from the RAM, in step S22, the engine speed Ne and the fuel injection amount Qf
Based on the
Search for rget.

Next, in step S24, the ECU 8 calculates the deviation Δλ between the target excess air ratio λ target and the estimated excess air ratio λ _(i) by the following equation. [Delta] [lambda] = [lambda] target- [lambda] _(i) Next, in steps S26 and S28, the ECU 8 uses the proportional gain Kp and the integral gain KI to calculate the proportional term EP and the integral term EI of the EGR control by the following equations, respectively.
In the calculation of the integral term EI, the absolute value of the deviation | Δλ |
Is larger than a predetermined upper limit value Dλ _O , Δλ is set to 0. This is because if the absolute value of deviation | Δλ | is too large,
If the deviation Δλ is integrated as it is, the absolute value of the integral term EI |
This is because EI | becomes too large and control followability with respect to changes in operating conditions deteriorates.

After calculating the proportional term EP and the integral term EI, the ECU 8 determines that EP = KP.multidot..DELTA..lambda.EI = KI.multidot..DELTA..lambda.
In step S30 of FIG. 4, the basic correction value EPI is calculated by the following equation. EPI = EP + EI Next, in step S32, the ECU 8 performs limiter processing for clipping the calculated basic correction value EPI to a predetermined upper and lower limit value to determine the opening correction value Eposc of the EGR valve 31.

Next, in step S34, the ECU 8 searches the map for the basic opening Eo of the EGR valve 31 based on the engine speed Ne and the fuel injection amount Qf, and then in step S34.
At 36, the target EGR valve opening Epos is calculated by the following equation. Epos = Eo + Eposc Next, the ECU 8 drives and controls the EGR valve 31 based on the target EGR valve opening degree Epos in step S38, then returns to the start and repeats the control.

As described above, in the above embodiment, the excess air ratio is estimated on the basis of the intake pressure, the fuel injection amount, etc., so that an expensive sensor such as LAFS is not used.
The excess air ratio can now be detected accurately and quickly. Further, based on the detected excess air ratio, the EGR valve 31
By controlling the driving of the EGR, the EGR is performed even during acceleration or deceleration.
Can be appropriately performed under reflux of the gas, it could be suppressed very low emissions of black smoke and NO _X.

Although the description of the specific embodiment has been completed, the embodiment of the present invention is not limited to this embodiment. For example,
The above-described embodiment applies the present invention to a diesel engine equipped with a turbocharger, but is also suitable for a naturally aspirated diesel engine, a lean-burn gasoline engine, and the like. Further, in the above-described air excess ratio detection subroutine, the turbine upstream pressure is calculated from the turbine acceleration pressure, the turbine upstream pressure steady value, or the like, but it may be measured using an exhaust pressure sensor or the like. Further, in the EGR control subroutine, the EGR control is performed using the excess air ratio λ estimated in the excess air ratio detection subroutine. However, the LAFS is attached to the intake pipe or the like and the EGR control is performed based on the detection result. You may Further, in the above-mentioned embodiment, the excess air ratio is estimated based on the operating parameters (EGR amount and total intake air amount) before three strokes, but the operating parameters before two strokes or after four strokes are determined depending on the operating condition. The variable method used may be adopted. In the above embodiment, the excess air ratio is estimated for each intake stroke, but it may be estimated asynchronously with the stroke.
Further, the specific configuration of the engine control system, the control procedure, and the like can be changed without departing from the gist of the present invention.

[0037]

According to the first aspect of the present invention, the air-fuel mixture supplied to the engine mounted on the vehicle while the exhaust gas recirculation system of the engine is operating is based on the operating state of the engine. In the excess air ratio detecting device for repeatedly detecting the excess air ratio, the intake pressure detecting means for detecting the intake pressure of the engine, the exhaust pressure detecting means for detecting the exhaust pressure of the engine, and the intake pressure detecting means are detected. An exhaust gas recirculation amount estimating means for estimating a recirculation amount of exhaust gas by the exhaust gas recirculation device based on the intake pressure and an exhaust pressure detected by the exhaust pressure detection device, and the exhaust gas recirculation device. Intake amount detecting means for detecting the intake amount of the engine including exhaust gas recirculation amount, intake amount detected by the intake amount detecting means, and a predetermined number of times And an equivalent intake fresh air amount estimating means for estimating the equivalent intake fresh air amount of the engine based on the excess air ratio estimated before the start and the exhaust gas recirculation amount estimated by the exhaust gas recirculation amount estimating means. A fuel supply amount detecting means for detecting a fuel supply amount of the engine, a fuel supply amount detected by the fuel supply amount detecting means, and an equivalent intake fresh air amount estimated by the equivalent intake fresh air amount estimating means. Based on the above, the air excess ratio estimating means for estimating the excess air ratio of the engine is provided, so that the excess air ratio in the diesel engine or the like can be accurately and promptly without using the LAFS or the like which is poor in reliability and costly. can be detected, it is possible to perform appropriate control of the fuel injection amount and the EGR amount in order to reduce NO _X emissions and black smoke emissions.

According to a second aspect, in the excess air ratio detecting device according to the first aspect, the intake air amount detecting means detects the intake air amount based on the intake air pressure detected by the intake air pressure detecting means. Therefore, it is not necessary to provide an expensive air flow sensor or the like. According to claim 3, in the excess air ratio detecting device according to claim 1 or 2, the engine has a turbocharger, and the exhaust gas recirculation amount estimating means is based on an exhaust pressure upstream of the turbo. Since the exhaust gas recirculation amount is estimated by using the exhaust gas recirculation amount, it is not necessary to provide a flow rate sensor for the recirculation exhaust gas, and the increase in cost and the number of parts can be suppressed.

According to a fourth aspect of the present invention, in the excess air ratio detecting device of the first to third aspects, the exhaust pressure detecting means obtains an exhaust pressure steady value from the engine speed and the fuel supply amount, and the exhaust pressure is the same. The steady-state pressure value, the turbine acceleration pressure is calculated from the exhaust gas recirculation amount and the intake amount several strokes ago, and the load is calculated from the turbine acceleration pressure and the steady-state exhaust pressure value. Because the exhaust pressure this time is calculated from the turbine acceleration pressure and the above load,
It is not necessary to provide an exhaust pressure sensor, and increase in cost and the number of parts can be suppressed.

According to a fifth aspect of the present invention, in the excess air ratio detecting device of the first to fourth aspects, the exhaust gas recirculation amount estimating means determines the exhaust gas recirculation amount based on the valve opening degree of the exhaust gas recirculation device. Since the estimation is performed, it is not necessary to provide a flow rate sensor for the recirculated exhaust gas, and the increase in cost and the number of parts can be suppressed. According to claim 6, in the excess air ratio detecting device according to claims 1 to 5, the exhaust gas recirculation amount estimating means obtains an orifice coefficient from a differential pressure between the exhaust pressure and the intake pressure to determine the engine rotation speed and , The recirculation exhaust gas temperature coefficient from the fuel supply amount, from the valve opening of the exhaust gas recirculation device, the throttle coefficient of the exhaust gas recirculation device, the orifice coefficient, and the recirculation exhaust gas temperature coefficient Since the exhaust gas recirculation amount is estimated, it is not necessary to provide a flow rate sensor for the recirculation exhaust gas and the like, and an increase in cost and the number of parts can be suppressed.

According to a seventh aspect of the present invention, in the air excess ratio detection device of the first to sixth aspects, the equivalent intake fresh air amount estimating means determines the recirculation amount of the exhaust gas from the intake air amount by the air excess ratio. Since the equivalent intake fresh air amount is estimated by subtracting the value divided by, the equivalent intake fresh air amount can be estimated accurately and in real time. According to claim 8, in the excess air ratio detecting device according to any one of claims 1 to 7, the excess air ratio estimating means estimates the excess air ratio for each stroke of the engine. The control responsiveness such as the amount and EGR amount is improved.

According to a ninth aspect, in the exhaust gas recirculation control device for controlling the valve opening amount of the exhaust gas recirculation device of the engine based on the operating state of the engine mounted on the vehicle, Excess air ratio detecting means for detecting the excess air ratio of the air-fuel mixture supplied, target air excess ratio setting means for setting the target air excess ratio of the air-fuel mixture supplied to the engine, the air excess ratio and the target A valve opening amount setting means for setting a target valve opening amount of the exhaust gas recirculation device so as to eliminate a deviation from an excess air ratio, and a drive for driving and controlling the exhaust gas recirculation device based on the target valve opening amount. Since the control device is provided, it is possible to reduce the NO _x emission amount and the black smoke emission amount in the diesel engine and the like.

According to a tenth aspect, in the exhaust gas recirculation control device according to the ninth aspect, the target excess air ratio setting means sets the target excess air ratio based on the engine speed and the fuel supply amount. Therefore, it is possible to reduce the NO _X emission amount and the black smoke emission amount even during the transient operation. Further, according to claim 11, claim 9 or 1
In the exhaust gas recirculation control device of No. 0, the valve opening amount setting means sets the valve opening amount by at least proportional integral control, and when the absolute value of the deviation is larger than a predetermined value, the proportional value is set. Since integration of the integration term is not performed in the integration control, deterioration of control response due to excessive integration term is prevented.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an engine control system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of an excess air ratio detection subroutine.

FIG. 3 is a flowchart showing a procedure of an EGR control subroutine.

FIG. 4 is a flowchart showing a procedure of an EGR control subroutine.

FIG. 5 is a graph showing changes in the excess air ratio when the fuel injection amount is rapidly increased and the detection results obtained by the conventional device.

[Explanation of symbols]

 1 Engine 2 Cylinder Head 4 Fuel Injection Valve 5 Electronic Governor 6 Fuel Injection Pump 8 ECU 11 Intake Manifold 13 Turbocharger 14 Compressor 17 Boost Pressure Sensor 20 Exhaust Manifold 21 Turbine 30 EGR Pipe 31 EGR Valve 42 Negative Pressure Side EGR Solenoid 43 Vacuum Pump 45 Atmosphere side EGR solenoid

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F02M 25/07 550 F02M 25/07 550P 570 570C 570P

Claims (11)

[Claims] 1. An air excess that repeatedly detects an air excess ratio of an air-fuel mixture supplied to the engine while the exhaust gas recirculation device of the engine is operating, based on an operating state of the engine mounted on the vehicle. In the rate detecting device, intake pressure detecting means for detecting the intake pressure of the engine, exhaust pressure detecting means for detecting the exhaust pressure of the engine, intake pressure detected by the intake pressure detecting means and exhaust pressure detecting means Exhaust gas recirculation amount estimating means for estimating a recirculation amount of exhaust gas by the exhaust gas recirculation device based on the exhaust pressure detected by the exhaust gas recirculation device, and intake air of the engine including the exhaust gas recirculation amount by the exhaust gas recirculation device. Intake air amount detecting means for detecting the intake air amount, the intake air amount detected by the intake air amount detecting means, and the air pressure estimated a predetermined number of times before. And an equivalent intake fresh air amount estimating means for estimating the equivalent intake fresh air amount of the engine based on the rate and the exhaust gas recirculation amount estimated by the exhaust gas recirculation amount estimating means, and the fuel supply amount of the engine. The excess air ratio of the engine based on the detected fuel supply amount detecting means, the fuel supply amount detected by the fuel supply amount detecting means, and the equivalent intake fresh air amount estimated by the equivalent intake fresh air amount estimating means. An excess air ratio detecting device for an engine, comprising: an excess air ratio estimating means for estimating. 2. The excess air ratio detecting device for an engine according to claim 1, wherein the intake air amount detecting means detects the intake air amount based on the intake pressure detected by the intake pressure detecting means. 3. The engine has a turbocharger, and the exhaust gas recirculation amount estimation means estimates the exhaust gas recirculation amount based on the exhaust pressure upstream of the turbo. Alternatively, the excess air ratio detecting device for the engine according to the item 2. 4. The exhaust pressure detection means obtains a steady value of exhaust pressure from an engine speed and a fuel supply amount, and a turbine value is obtained from the steady value of exhaust pressure and exhaust gas recirculation amount and intake amount several strokes ago. The acceleration pressure is obtained, the load is obtained from the turbine acceleration pressure and the exhaust pressure steady value, and the current value of the exhaust pressure is obtained from the previous value of the exhaust pressure, the turbine acceleration pressure, and the load. The excess air ratio detection device for an engine according to any one of claims 1 to 3. 5. The exhaust gas recirculation amount estimation means estimates the exhaust gas recirculation amount based on a valve opening degree of the exhaust gas recirculation device, according to any one of claims 1 to 4. Excess air ratio detector for the engine. 6. The exhaust gas recirculation amount estimating means obtains an orifice coefficient from a differential pressure between exhaust pressure and intake pressure, obtains a recirculation exhaust gas temperature coefficient from an engine rotation speed and a fuel supply amount, The exhaust gas recirculation amount is estimated from the valve opening of the recirculation device, the throttling coefficient of the exhaust gas recirculation device, the orifice coefficient, and the recirculation exhaust gas temperature coefficient. 5. The engine excess air ratio detection device according to claim 5. 7. The equivalent intake fresh air amount estimating means estimates the equivalent intake fresh air amount by subtracting a value obtained by dividing the recirculation amount of the exhaust gas by the excess air ratio from the intake amount. The excess air ratio detection device for an engine according to any one of claims 1 to 6. 8. The excess air ratio of the engine according to claim 1, wherein the excess air ratio estimating means estimates the excess air ratio for each stroke of the engine. Rate detector. 9. An exhaust gas recirculation control device for controlling a valve opening amount of an exhaust gas recirculation device of an engine based on an operating state of an engine mounted on a vehicle, wherein air of a mixture gas supplied to the engine. An excess air ratio detecting means for detecting an excess ratio, a target excess air ratio setting means for setting a target excess air ratio of the air-fuel mixture supplied to the engine, and a deviation between the excess air ratio and the target excess air ratio are A valve opening amount setting means for setting a target valve opening amount of the exhaust gas recirculation device so that the exhaust gas recirculation device is eliminated, and a drive control device for driving and controlling the exhaust gas recirculation device based on the target valve opening amount. An exhaust gas recirculation control device characterized by. 10. The exhaust gas recirculation control device according to claim 9, wherein the target excess air ratio setting means sets the target excess air ratio based on the engine speed and the fuel supply amount. 11. The valve opening amount setting means sets the valve opening amount by at least proportional integral control. When the absolute value of the deviation is larger than a predetermined value, the integral term in the proportional integral control is set. The exhaust gas recirculation control device according to claim 9 or 10, characterized in that the above is not integrated.