JPH0914023A - Exhaust gas pressure detection device and excess air factor detection device for turbosupercharged engine - Google Patents

Abstract

PURPOSE: To provide a device capable of accurately detecting a exhaust gas pressure of a turbosupercharged diesel engine or the like, as well as an excess air factor detection device using principle of an exhaust gas pressure detecting device under application of relatively simple device configuration. CONSTITUTION: ECU 8 first finds an intake volume map value from output of a sensor 10 of a rotation speed Ne and a sensor 17 of boost pressure, and corrects intake air temperature. Also. the ECU 8 continues retrieval using various maps, and calculates a total intake volume, turbine acceleration energy by an exhaust gas flowrate ratio, load resistance and turbine speed. Then, after calculating actual exhaust pressure of this time from a conversion factor and the turbine speed, a pressure correction factor is retrieved from the map on the basis of a difference between the actual exhaust gas pressure and an atmospheric pressure. Then, the ECU 8 calculates a post-correction current value from an output current value of a linear air-fuel ratio sensor(LAFS) 26 and the pressure correction factor, and finds an excess air factor from the map on the basis of the post-correction current value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pressure detection device and an excess air ratio detection device for a turbocharged engine, which is used in a fuel supply system and an exhaust purification system for a diesel engine equipped with a turbocharger for automobiles. Regarding

[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 LAFs
The EGR device that feedback-controls the EGR amount using S also has the following problems. As is well known, L
The AFS has a structure in which a porous platinum electrode is coated on the inner and outer surfaces of a test tubular zirconia element and the atmosphere is introduced into the interior while the outer surface is exposed to exhaust gas. The principle of the oxygen concentration battery is used in which the movement of oxygen ions occurs and a current proportional to the oxygen concentration (excess air ratio) in the exhaust gas flows. The LAFS has a characteristic that even if the oxygen concentration in the exhaust gas is the same, the movement of oxygen ions depends on the oxygen partial pressure in the exhaust gas, so that the output current value varies depending on the exhaust pressure. . Further, the LAFS does not operate normally unless the ambient temperature rises above a predetermined value (activation temperature), so it is usually attached to the collecting portion of the exhaust manifold or the like. Therefore, in an engine with a turbocharger in which the exhaust pressure on the upstream side of the turbine varies greatly, the output current value of the LAFS also varies greatly depending on the operating state of the turbocharger or EGR device, and the excess air ratio can be accurately detected. There was a problem of disappearing.

As a solution to this problem, Japanese Patent Publication No.
No. 41821, LAFS is provided on the upstream side of the turbine.
A discharge pressure sensor is attached together with it, and L is detected according to the detection signal.
It has been proposed to correct the comparison current value to be compared with the output current value of the AFS. However, the exhaust pressure sensor is an expensive component including an element for converting pressure into an electric signal, an amplifier for amplifying the electric signal, and the like, and is also durable because it is used in an environment of high temperature and severe pressure fluctuations. Not only is it low and the initial cost is high, but there is also the problem that the running cost is high due to periodic inspections and replacements.

The present invention has been made in view of the above circumstances, and provides an exhaust pressure detecting device and its principle capable of accurately detecting the exhaust pressure of a diesel engine with a turbocharger while adopting a relatively simple device configuration. It is an object to provide an excess air ratio detecting device used.

[0008]

Therefore, in claim 1 of the present invention, the intake pressure detecting means for detecting the intake pressure of the engine mounted on the vehicle, and the turbine driven by the exhaust gas of the engine, A turbocharger for supercharging intake air to the engine, a fuel supply amount detecting means for detecting a fuel supply amount of the engine, an intake pressure detected by the intake pressure detecting means, and a fuel supply amount detecting means for detecting the fuel supply amount. Based on the fuel supply amount, the steady exhaust pressure estimating means for estimating the steady exhaust pressure which is the exhaust pressure when the engine is in the steady operating state, and the steady exhaust pressure estimated by the steady exhaust pressure estimating means. Based on the turbine speed estimating means for estimating the turbine speed of the turbocharger, and the turbine speed estimated by the turbine speed estimating means. Based on the speed, we propose an exhaust pressure detecting apparatus turbocharged engine equipped with the actual exhaust pressure estimation means for estimating an actual exhaust pressure in the exhaust pressure in the current operating state of the engine.

A second aspect of the present invention proposes the exhaust pressure detecting device according to the first aspect, wherein the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake amount estimated from the intake pressure. A third aspect of the present invention proposes that the exhaust pressure detecting device according to the second aspect is such that the total intake air amount is corrected by the intake air temperature.

According to a fourth aspect, in the exhaust pressure detecting device according to the first to third aspects, the steady exhaust pressure estimating means is
It is proposed to estimate the steady exhaust pressure based on the total intake amount and the fuel supply amount estimated from the intake pressure. According to a fifth aspect of the present invention, in the exhaust pressure detection device according to the first to fourth aspects, the turbine speed estimating means calculates based on the total intake air amount and an estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. We propose a method for estimating turbine speed using exhaust gas flow rate ratio.

According to a sixth aspect of the present invention, in the exhaust pressure detecting device according to the fifth aspect, the exhaust gas recirculation amount is calculated using an orifice coefficient obtained from a differential pressure between the actual exhaust pressure on the turbine upstream side and the intake pressure. Suggest what will be done. Also,
A seventh aspect of the present invention proposes the exhaust pressure detecting device according to the fifth or sixth aspect, wherein the exhaust gas recirculation amount is corrected by the exhaust gas temperature.

Further, according to an eighth aspect, in the exhaust pressure detecting device according to the first to seventh aspects, the turbine speed estimating means comprises:
We propose a method to estimate turbine speed using turbine acceleration energy. Further, in claim 9, claims 1 to 8
In the exhaust pressure detecting device, the turbine speed estimating means estimates the turbine speed using the turbine load resistance.

According to a tenth aspect of the present invention, in the exhaust pressure detecting device of the first to ninth aspects, the turbine speed estimating means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow rate ratio. We propose to estimate the turbine speed by integrating the deviation between the turbine acceleration energy and the turbine load resistance and dividing it by the turbine inertia coefficient.

Further, in claim 11, it is proposed that in the exhaust pressure detecting device according to any one of claims 1 to 10, the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. Further, a twelfth aspect of the present invention proposes that, in the exhaust pressure detection device according to the first to eleventh aspects, the actual exhaust pressure estimating means estimates the actual exhaust pressure for each stroke of the engine.

Further, according to a thirteenth aspect, an intake pressure detecting means for detecting an intake pressure of an engine mounted on a vehicle and a turbo for supercharging the intake air to the engine by driving a turbine by the exhaust gas of the engine. Supercharger,
Based on the fuel supply amount detecting means for detecting the fuel supply amount of the engine, the intake pressure detected by the intake pressure detecting means, and the fuel supply amount detected by the fuel supply amount detecting means, the engine is in steady operation. A steady exhaust pressure estimating means for estimating a steady exhaust pressure which is an exhaust pressure in a state, and a turbine for estimating a turbine speed of the turbocharger based on the steady exhaust pressure estimated by the steady exhaust pressure estimating means. A speed estimating means, an actual exhaust pressure estimating means for estimating an actual exhaust pressure which is an exhaust pressure in a current operating state of the engine based on the turbine speed estimated by the turbine speed estimating means, and a turbo in an exhaust passage of the engine. It is installed on the upstream side of the turbocharger, and continuously maintains the excess air ratio of the engine in a predetermined excess air region. Air of an engine provided with an air-fuel ratio sensor capable of outputting, and an air excess ratio correction means for correcting the excess air ratio detected by the air-fuel ratio sensor based on the actual exhaust pressure estimated by the actual exhaust pressure estimation means. An excess rate detector is proposed.

In a fourteenth aspect of the present invention, it is proposed that in the air excess ratio detecting device of the thirteenth aspect, the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake amount estimated from the intake pressure. Further, in claim 15,
In the excess air ratio detecting device according to claim 14, it is proposed that the total intake air amount is corrected by the intake air temperature.

In the sixteenth aspect, the thirteenth to fifteenth aspects are included.
In the excess air ratio detecting device, the steady exhaust pressure estimation means estimates the steady exhaust pressure based on the total intake amount and the fuel supply amount estimated from the intake pressure.
According to a seventeenth aspect, in the air excess ratio detecting device according to the thirteenth to sixteenth aspects, the turbine speed estimating means is calculated based on the total intake air amount and the estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. We propose a method to estimate the turbine speed using the exhaust gas flow rate ratio.

In the eighteenth aspect of the present invention, in the excess air ratio detecting device of the seventeenth aspect, the exhaust gas recirculation amount uses an orifice coefficient obtained from the differential pressure between the actual exhaust pressure on the turbine upstream side and the intake pressure. Suggest what is calculated.
Further, claim 19 proposes that the exhaust gas recirculation amount is corrected by the exhaust gas temperature in the air excess ratio detecting device according to claim 17 or 18.

Further, in claim 20, claims 13 to 19 are provided.
In the excess air ratio detection device, the turbine speed estimating means estimates the turbine speed using the turbine acceleration energy. A twenty-first aspect of the present invention proposes that, in the air excess ratio detection device of the thirteenth to twentieth aspects, the turbine speed estimating means estimates the turbine speed by using a turbine load resistance.

Further, in claim 22, claims 13 to 21 are provided.
In the air excess ratio detection device, the turbine speed estimation means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow rate ratio, and integrates the deviation between the turbine acceleration energy and the turbine load resistance, We propose to estimate the turbine speed by dividing this by the turbine inertia coefficient.

Further, in claim 23, claims 13 to 22 are provided.
In the excess air ratio detecting device, the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. A twenty-fourth aspect of the present invention proposes that the excess air ratio detecting device according to the thirteenth to twenty-third aspects corrects the excess air ratio for each stroke of the engine.

[0022]

In the exhaust pressure detecting device of the present invention, after the steady exhaust pressure estimating means estimates the steady exhaust pressure from the intake pressure detected by the intake pressure detecting means and the fuel supply amount detected by the fuel supply amount detecting means, The turbine speed estimating means estimates the turbine speed from the steady exhaust pressure, and finally the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed.

According to the exhaust pressure detecting device of claim 2,
The steady exhaust pressure estimation means estimates the total intake air amount from the intake pressure, and estimates the steady exhaust pressure from the total intake air amount. Also,
In the exhaust pressure detection device according to the third aspect, the steady exhaust pressure estimation means corrects the estimated total intake air amount by the intake air temperature in order to prevent the estimation of the excessive amount or the excessive amount due to thermal expansion or the like.

According to the exhaust pressure detecting device of claim 4,
The steady exhaust pressure estimation means estimates the total intake amount from the intake pressure and the engine rotation speed, and then estimates the steady exhaust pressure from the total intake amount and the fuel supply amount. Further, in the exhaust pressure detecting device according to claim 5, the turbine speed estimating means calculates the exhaust gas flow rate ratio by dividing the total intake air amount by subtracting the exhaust gas recirculation amount from the total intake air amount, and using it for this. Estimate turbine speed.

According to the exhaust pressure detecting device of claim 6,
The orifice coefficient is calculated from a map or the like based on the differential pressure, and the exhaust gas recirculation amount is calculated using this. Further, in the exhaust pressure detection device of the seventh aspect, the calculated exhaust gas recirculation amount is corrected by the exhaust gas temperature in order to prevent excessive estimation due to thermal expansion. Further, in the exhaust pressure detecting device of claim 8,
The turbine speed estimation means calculates the turbine acceleration energy from the exhaust gas flow rate ratio and the steady exhaust pressure, and estimates the turbine speed using this.

According to the exhaust pressure detecting device of claim 9,
The turbine speed estimation means calculates the turbine load resistance from the previous value of the turbine speed and the like, and uses this to estimate the turbine speed. Further, in the exhaust pressure detection device according to claim 10, the turbine speed estimation means calculates the turbine acceleration energy by multiplying the steady exhaust pressure by the exhaust gas flow rate ratio, and integrates the deviation between the turbine acceleration energy and the turbine load resistance. , This is divided by the turbine inertia coefficient to obtain the turbine speed.

Further, in the exhaust pressure detecting device of the eleventh aspect, the actual exhaust pressure estimating means calculates the actual exhaust pressure by multiplying the turbine speed by the conversion coefficient. Further, in the exhaust pressure detection device according to claim 12, the actual exhaust pressure estimation means is
Based on the output signal from the crank angle sensor etc., for example,
The actual exhaust pressure is estimated at the start of the intake stroke of each cylinder.

Further, in the excess air ratio detecting device of the thirteenth aspect, the steady exhaust pressure is estimated from the intake pressure detected by the intake pressure detecting means by the steady exhaust pressure estimating means and the fuel supply amount detected by the fuel supply amount detecting means. After that, the turbine speed estimation means estimates the turbine speed from this steady exhaust pressure, and then the actual exhaust pressure estimation means estimates the actual exhaust pressure from this turbine speed.After that, the excess air ratio correction means uses the air-fuel ratio sensor. The detected excess air ratio is corrected by the actual exhaust pressure.

Further, in the excess air ratio detecting device of the fourteenth aspect, the steady exhaust pressure estimating means estimates the total intake amount from the intake pressure, and estimates the steady exhaust pressure from the total intake amount. Further, in the excess air ratio detecting device of the fifteenth aspect, the steady exhaust pressure estimating means corrects the estimated total intake air amount by the intake air temperature in order to prevent the estimation of the excessive amount or the excessive amount due to the thermal expansion or the like.

Further, in the excess air ratio detecting device of the sixteenth aspect, the steady exhaust pressure estimating means estimates the total intake air amount from the intake pressure and the engine rotation speed, and then steady from the total intake air amount and the fuel supply amount. Estimate exhaust pressure. Claim 1
In the air excess ratio detection device of No. 7, the turbine speed estimation means calculates the exhaust gas flow rate ratio by dividing the total intake air amount by subtracting the exhaust gas recirculation amount by the total intake air amount, and uses this to calculate the turbine speed. presume.

Further, in the air excess ratio detecting device of the eighteenth aspect, the orifice coefficient is obtained from a map or the like based on the differential pressure,
Using this, the exhaust gas recirculation amount is calculated. Further, in the excess air ratio detecting device of the nineteenth aspect, the calculated exhaust gas recirculation amount is corrected by the exhaust gas temperature in order to prevent excessive estimation due to thermal expansion. Further, in the excess air ratio detecting device of the twentieth aspect, the turbine speed estimating means calculates the turbine acceleration energy from the exhaust gas flow rate ratio and the steady exhaust pressure, and estimates the turbine speed using this.

Further, in the excess air ratio detecting device of the twenty-first aspect, the turbine speed estimating means calculates the turbine load resistance from the previous value of the turbine speed and the like, and estimates the turbine speed using this. Further, in the excess air ratio detection device of claim 22, the turbine speed estimation means calculates the turbine acceleration energy by multiplying the steady exhaust pressure by the exhaust gas flow rate ratio,
The deviation between the turbine acceleration energy and the turbine load resistance is integrated, and this is divided by the turbine inertia coefficient to obtain the turbine speed.

Further, in the excess air ratio detecting device of the twenty-third aspect, the actual exhaust pressure estimating means calculates the actual exhaust pressure by multiplying the turbine speed by the conversion coefficient. Further, in the excess air ratio detecting device of the twenty-fourth aspect, the excess air ratio estimating means estimates the excess air ratio, for example, at the start of the intake stroke of each cylinder based on the output signal from the crank angle sensor or the like.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust pressure detecting device and an excess air ratio detecting 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 a 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 fuel injection timing and injection period are set by the electronic governor 5 controlled by the ECU (engine control unit) 8. In the figure, 9 is a water temperature sensor attached to the cylinder head 2 to detect the cooling water temperature Tw, and 10 is a Ne sensor attached to the fuel injection pump 6 to detect the engine rotation speed Ne.

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 to 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 intake pressure (Manifold Absolute
Pressure) Pb is a boost pressure sensor that detects Pb, both of which 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. In the engine 1 of the present embodiment, the LAFS 26 that continuously outputs a current according to the air-fuel ratio A / F on the lean side of the stoichiometric air-fuel ratio and the exhaust temperature Te that detects the exhaust gas temperature are provided to the exhaust manifold 20. An exhaust gas temperature sensor 27 for detecting is attached.

On the other hand, the exhaust manifold 20 and the intake manifold 11 are communicated with each other via an EGR pipe 30, and the conduit of this EGR pipe 30 is the intake manifold 1.
Opened by the valve element 32 of the EGR valve 31 provided on the first side.
It is designed to be shut off. The EGR valve 31 is a negative pressure actuation type, and includes a valve body 32, a diaphragm 33, a return spring 34, and a negative pressure chamber 35. In the figure, 36 is EG
The EGR position sensor detects the opening A _E of the R 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.
Block 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.) for incorporating a control program, a central processing unit (CPU), and the like. Detection information from various sensors and switches including the above-described sensors is input to the input side of the ECU 8, and the ECU 8 starts with the electronic governor 5 based on the detection information and the control map.
The drive control of the GR solenoids 42, 45 and the like is performed.

The exhaust pressure detection procedure and the excess air ratio detection procedure in this embodiment will be described below. The driver turns on the ignition key and engine 1 starts,
Predetermined conditions (in this embodiment, the water temperature TW is 70 ° C or higher,
30 seconds or more after starting, boost pressure sensor 17 and EGR
If the position sensor 36 is normal, etc.), the ECU 8 repeatedly executes the exhaust pressure detection subroutine shown in the flowcharts of FIGS. 2 and 3 and the block diagram of FIG. 4 for each stroke of the engine 1. To do. When this subroutine is started, the ECU 8 first in step S2 of FIG. 2, outputs the engine speed Ne (rpm) and the intake pressure P output from the Ne sensor 10 and the boost pressure sensor 17.
Based on b (mmH ₂ O), the intake air amount map value Qao is shown in FIG.
Search from the map of. Next, the ECU 8 executes step S
4, the intake air temperature Tb detected by the intake air temperature sensor 16
Based on (° C.), the intake air temperature correction for the intake air amount map value Qao is performed by the following formula to calculate the total intake air amount Qa (g / st) sucked into the engine 1.

Qa = Qao273 / (273 + Tb) When the calculation of the total intake air amount Qa is completed, the ECU 8 determines in step S6 that the steady intake air amount Qa and the fuel supply amount Qf output from the electronic governor 5 are steady. Exhaust pressure Pw (mmHg)
Is searched from a map not shown. Next, the ECU 8
In step S8, the total intake air amount Qa and the previous EGR described later
Based on the quantity Qe _(i-1) and the exhaust gas flow rate ratio K according to the following formula
Calculate g.

Kg = 1-Qe_(i-1)/ Qa Next, in step S10, the ECU 8 determines the exhaust gas flow rate.
From the quantity ratio Kg and the steady exhaust pressure Pw previously obtained,
Then, the turbine acceleration energy F is calculated. F = Kg.Pw Next, in step S12, the ECU 8 converts the conversion coefficient KL into
Last turbine speed V _(i-1)From the
Calculate anti-FL.

FL = KL.V^Two _(i-1) Next, in step S14, the ECU 8 determines the turbine inertia coefficient.
Number It, turbine acceleration energy F, load resistance FL
, The turbine speed V_(i)Calculate (rad / s)
Put out. V_(i)= 1 / It.∫ (F-FL) dt Next, in step S16 of FIG.
Kp and turbine speed V _(i)And from the following formula
The exhaust pressure Pex (mmHg) is calculated.

Pex = Kp.multidot.V _{(i) Although the} exhaust pressure estimation is finished, the ECU 8 next proceeds to step S18 to find out the actual exhaust pressure Pex and the atmospheric pressure Pa (760 m).
Based on the differential pressure ΔP _{1 from} m Hg), the pressure correction coefficient Kaf is searched from the map of FIG. 7. The pressure correction coefficient Kaf is
Of course, when the differential pressure ΔP ₁ is 0, it is 1.0, but in the case of this embodiment, 100 mm H in accordance with the pressure characteristics of the LAFS 26.
It is set to decrease by 7% for every increase in g.

Next, the ECU 8 determines in step S20 the differential pressure ΔP ₂ between the actual exhaust pressure Pex and the intake pressure Pb (ie,
The front-rear pressure of the EGR valve 31) is calculated, and the orifice coefficient K _O is searched from the map of FIG. 8 based on this differential pressure ΔP ₂ in step S22. In this way, the orifice coefficient K _O
Then, the ECU 8 calculates the basic EGR amount Qeo this time by the following equation in step S24. In the formula below, A _E is E
EGR valve 3 detected by GR position sensor 36
The opening degree is 1 (%), and Ks is a flow coefficient (constant value).

Qeo = Ko * Ks * _AE / (Ne / 120) When the basic EGR amount Qeo is obtained, the ECU 8 determines in step S
26, the exhaust temperature T detected by the exhaust temperature sensor 27
Using e (that is, the EGR gas temperature), the basic EGR amount Qeo is temperature-corrected by the following equation to obtain the EGR amount Q this time.
Calculate e _(i) (g / st). The EGR obtained here
The quantity Qe _(i) is stored in the RAM, and the above-mentioned step S8 is performed.
It is used for the calculation of the exhaust gas flow rate ratio Kg.

Qe _(i) = Qeo.273 / (273 + Te) Now, in this embodiment, in parallel with the exhaust pressure detection subroutine, the ECU 8 causes the air shown in the flow chart of FIG. The excess rate detection subroutine is repeatedly executed. When you start this subroutine, EC
First, in step S30, the U8 reads the output current value Ipo of the LAFS 26. Next, the ECU 8 executes step S3.
In step 2, the corrected current value Ip is calculated by the following equation using the pressure correction coefficient Kaf obtained in the exhaust pressure detection subroutine.

Ip = Kaf · Ipo After that, the ECU 8 obtains the excess air ratio λ from the map of FIG. 9 in step S34, and terminates the subroutine. When the excess air ratio λ is obtained by the excess air ratio detection subroutine, the ECU 8 drives and controls the EGR valve 31 and the electronic governor 5 by the EGR control subroutine and the fuel injection control subroutine according to the deviation from the target excess air ratio λobj. , Its details are not mentioned here.

As described above, in the above embodiment, since the exhaust pressure is detected in real time from the intake pressure, the fuel supply amount, etc., the excess air ratio by LAFS is eliminated without using an expensive and poor exhaust pressure sensor. Can be detected accurately and quickly. Then, by controlling the drive of the EGR valve and the electronic governor based on the detected excess air ratio, the EGR gas recirculation and fuel injection can be appropriately performed even during acceleration and deceleration, and black smoke and NO _x It was possible to keep the amount of emissions of extremely low.

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, the specific configuration and control procedure of the engine control system can be changed without departing from the spirit of the present invention.

[0050]

According to the exhaust pressure detecting device of the first aspect of the present invention, the intake pressure detecting means for detecting the intake pressure of the engine mounted on the vehicle and the turbine driven by the exhaust gas of the engine are provided. A turbocharger for supercharging intake air to the engine, a fuel supply amount detecting means for detecting a fuel supply amount of the engine, an intake pressure detected by the intake pressure detecting means, and a fuel supply amount detecting means. Based on the detected fuel supply amount, the steady exhaust pressure estimating means for estimating the steady exhaust pressure which is the exhaust pressure when the engine is in the steady operating state, and the steady exhaust pressure estimated by the steady exhaust pressure estimating means. Based on the turbine speed estimating means for estimating the turbine speed of the turbocharger, and the turbine speed estimating means for estimating the turbine speed. Since the actual exhaust pressure estimation means for estimating the actual exhaust pressure, which is the exhaust pressure in the current operating state of the engine, is provided based on the speed, the turbo overpass without using the exhaust temperature sensor with high cost and poor durability is used. The exhaust pressure of the engine with a feeder can be detected accurately and quickly, and the LAFS pressure can be corrected.

According to a second aspect, in the exhaust pressure detecting device according to the first aspect, the steady exhaust pressure estimating means is
Since the steady exhaust pressure is estimated based on the total intake amount estimated from the intake pressure, the steady exhaust pressure can be estimated accurately and quickly. Further, according to claim 3, in the exhaust pressure detecting device according to claim 2, since the total intake air amount is corrected by the intake air temperature, it is possible to prevent an overestimation or an underestimation due to thermal expansion or the like. , The total intake air amount can be estimated more accurately.

According to a fourth aspect of the present invention, in the exhaust pressure detecting device according to the first to third aspects, the steady exhaust pressure estimating means comprises the steady exhaust based on the total intake amount and the fuel supply amount estimated from the intake pressure. Since the pressure is estimated, the steady exhaust pressure can be estimated accurately and quickly. Further, according to claim 5, in the exhaust pressure detecting device according to any one of claims 1 to 4, the turbine speed estimating means calculates based on the total intake air amount and an estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. Since the turbine speed is estimated by using the exhaust gas flow rate ratio, the turbine speed can be estimated accurately and quickly.

According to a sixth aspect of the present invention, in the exhaust pressure detecting device of the fifth aspect, the exhaust gas recirculation amount uses an orifice coefficient obtained from a differential pressure between the actual exhaust pressure on the turbine upstream side and the intake pressure. The turbine speed can be estimated more accurately because the calculation is performed by Further, according to claim 7, in the exhaust pressure detecting device according to claim 5 or 6, the exhaust gas recirculation amount is corrected by the exhaust gas temperature, so that the estimation of the turbine speed is more accurate. You can do it.

According to the eighth aspect, in the exhaust pressure detecting device according to the first to seventh aspects, the turbine speed estimating means estimates the turbine speed by using the turbine acceleration energy. Therefore, the turbine speed is estimated. Can be done more accurately. Further, according to claim 9, in the exhaust pressure detection device according to any one of claims 1 to 8, the turbine speed estimating means estimates the turbine speed using the turbine load resistance, so that the estimation of the turbine speed is more accurate. You can do it.

According to claim 10, claims 1 to 9 are
In the exhaust pressure detection device of, the turbine speed estimating means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow rate ratio, integrates the deviation between the turbine acceleration energy and turbine load resistance, Is divided by the turbine inertia coefficient to estimate the turbine speed, so that the turbine speed can be estimated more accurately.

According to claim 11, claims 1 to 1
In the zero exhaust pressure detection device, the actual exhaust pressure estimation means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient, so that the actual exhaust pressure can be estimated more accurately. According to claim 12, claims 1 to 11
In the exhaust pressure detection device, since the actual exhaust pressure estimating means estimates the actual exhaust pressure for each stroke of the engine, the estimation can be performed more accurately during transient operation or the like.

Further, according to the excess air ratio detecting device of the thirteenth aspect, the intake pressure detecting means for detecting the intake pressure of the engine mounted on the vehicle and the engine by driving the turbine by the exhaust gas of the engine. Turbocharger for supercharging the intake air to the engine, fuel supply amount detecting means for detecting the fuel supply amount of the engine, intake pressure detected by the intake pressure detecting means and the fuel supply amount detecting means Based on the fuel supply amount, the steady exhaust pressure estimating means for estimating the steady exhaust pressure which is the exhaust pressure when the engine is in the steady operating state, and the steady exhaust pressure estimated by the steady exhaust pressure estimating means , A turbine speed estimating means for estimating the turbine speed of the turbocharger, and a turbine speed estimated by the turbine speed estimating means. Based on the speed, an actual exhaust pressure estimating means for estimating an actual exhaust pressure, which is the exhaust pressure in the current operating state of the engine, and an exhaust passage of the engine, which is provided upstream of the turbocharger, in a predetermined excess air region. An air-fuel ratio sensor that can continuously detect the excess air ratio of the engine, and an excess air ratio that corrects the excess air ratio detected by the air-fuel ratio sensor based on the actual exhaust pressure estimated by the actual exhaust pressure estimation means. Since the ratio correction means is provided, the excess air ratio can be accurately and quickly performed, and the NO _x emission amount and the black smoke emission amount in the diesel engine or the like can be reduced.

According to the fourteenth aspect of the invention, in the air excess ratio detecting device of the thirteenth aspect, the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake air amount estimated from the intake pressure. The steady exhaust pressure can be estimated accurately and quickly. Further, according to claim 15, in the excess air ratio detecting device according to claim 14, since the total intake air amount is corrected by the intake air temperature, the total intake air amount can be estimated more accurately. .

In addition, according to claim 16, claim 13 to.
In the excess air ratio detection device of No. 15, the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake air amount and the fuel supply amount estimated from the intake pressure, so that the steady exhaust pressure is accurately estimated. And it can be done quickly. According to a seventeenth aspect, in the air excess ratio detecting device according to the thirteenth to sixteenth aspects, the turbine speed estimating means is based on the total intake air amount and the estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. Since the turbine speed is estimated using the calculated exhaust gas flow rate ratio, the turbine speed can be estimated accurately and quickly.

According to the eighteenth aspect, in the excess air ratio detecting device according to the seventeenth aspect, the exhaust gas recirculation amount is
Since the calculation is performed using the orifice coefficient obtained from the differential pressure between the actual exhaust pressure on the turbine upstream side and the intake pressure, the turbine speed can be estimated more accurately. Further, according to claim 19, in the air excess ratio detection device according to claim 17 or 18, since the exhaust gas recirculation amount is corrected by the exhaust gas temperature, the turbine speed can be estimated more. Can be done accurately.

In addition, according to claim 20, claim 13-.
In the excess air ratio detection device of 19, the turbine speed estimating means estimates the turbine speed by using the turbine acceleration energy, so that the turbine speed can be estimated more accurately. Further, according to claim 21, in the excess air ratio detecting device according to claims 13 to 20, the turbine speed estimating means estimates the turbine speed by using the turbine load resistance. Can be done accurately.

Further, according to claim 22, claims 13 to
21. In the air excess ratio detection device of No. 21, the turbine speed estimating means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow rate ratio, and integrates a deviation between the turbine acceleration energy and turbine load resistance. Since the turbine speed is estimated by dividing this by the turbine inertia coefficient, the turbine speed can be estimated more accurately.

Further, according to claim 23,
In the air excess ratio detection device No. 22, the actual exhaust pressure estimation means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient, so that the actual exhaust pressure can be estimated more accurately. According to Claim 24, Claim 13
In the excess air ratio detection device of Nos. 23 to 23, the excess air ratio is corrected every stroke of the engine, so that the estimation can be performed more accurately during the transient operation or the like.

[Brief description of the 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 exhaust pressure detection subroutine.

FIG. 3 is a flowchart showing a procedure of an exhaust pressure detection subroutine.

FIG. 4 is a block diagram showing a flow of exhaust pressure detection.

FIG. 5 is a flowchart showing a procedure of an excess air ratio detection subroutine.

FIG. 6 is a map for obtaining a total intake amount from intake pressure and engine speed.

FIG. 7 is a map for obtaining a pressure correction coefficient from a deviation between exhaust pressure and atmospheric pressure.

FIG. 8 is a map for obtaining an orifice coefficient from a deviation between exhaust pressure and intake pressure.

FIG. 9 is a map for obtaining an excess air ratio from the LAFS output current.

[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 26 LAFS 27 Exhaust Temperature Sensor 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 location F02M 25/07 550 F02M 25/07 550M 570 570P

Claims (24)

[Claims] 1. An intake pressure detecting means for detecting an intake pressure of an engine mounted on a vehicle, and a turbocharger for supercharging intake air to the engine by driving a turbine with exhaust gas of the engine, Based on the fuel supply amount detecting means for detecting the fuel supply amount of the engine, the intake pressure detected by the intake pressure detecting means, and the fuel supply amount detected by the fuel supply amount detecting means, the engine is in steady operation. Steady exhaust pressure estimating means for estimating the steady exhaust pressure which is the exhaust pressure in the state, and a turbine for estimating the turbine speed of the turbocharger based on the steady exhaust pressure estimated by the steady exhaust pressure estimating means. Based on the speed estimation means and the turbine speed estimated by the turbine speed estimation means, the current operating state of the engine is determined. Exhaust pressure detecting apparatus turbocharged engine characterized in that an actual exhaust pressure estimation means for estimating an actual exhaust pressure, which is the kicking exhaust pressure. 2. The exhaust pressure detection for a turbocharged engine according to claim 1, wherein the steady exhaust pressure estimation means estimates the steady exhaust pressure based on the total intake amount estimated from the intake pressure. apparatus. 3. The exhaust pressure detecting device for a turbocharged engine according to claim 2, wherein the total intake air amount is corrected by an intake air temperature. 4. The steady exhaust pressure estimating means estimates the steady exhaust pressure based on a total intake amount and a fuel supply amount estimated from the intake pressure. An exhaust pressure detection device for an engine with a turbocharger according to the item. 5. The turbine speed estimating means estimates the turbine speed using an exhaust gas flow rate ratio calculated based on the total intake air amount and an estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. The exhaust pressure detection device for an engine with a turbocharger according to any one of claims 1 to 4, which is characterized in that. 6. The exhaust gas recirculation amount is calculated by using an orifice coefficient obtained from a differential pressure between an actual exhaust pressure on the upstream side of the turbine and an intake pressure.
An excess air ratio detecting device for an engine with a turbocharger as described above. 7. The excess air ratio detecting device for an engine with a turbocharger according to claim 5, wherein the exhaust gas recirculation amount is corrected by the exhaust gas temperature. 8. The exhaust gas of a turbocharged engine according to claim 1, wherein the turbine speed estimation means estimates the turbine speed using turbine acceleration energy. Pressure detector. 9. The exhaust gas of the turbocharged engine according to claim 1, wherein the turbine speed estimating means estimates the turbine speed using a turbine load resistance. Pressure detector. 10. The turbine speed estimating means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow rate ratio, integrates a deviation between the turbine acceleration energy and turbine load resistance, and calculates the turbine acceleration energy. The exhaust pressure detection device for a turbocharged engine according to any one of claims 1 to 9, wherein the turbine speed is estimated by dividing the turbine speed by an inertia coefficient. 11. The turbocharger according to claim 1, wherein the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. Exhaust pressure detection device for engine. 12. The turbocharger according to claim 1, wherein the actual exhaust pressure estimation means estimates the actual exhaust pressure for each stroke of the engine. Exhaust pressure detection device for engine. 13. An intake pressure detecting means for detecting intake pressure of an engine mounted on a vehicle, and a turbocharger for supercharging intake air to the engine by driving a turbine by exhaust gas of the engine, Based on the fuel supply amount detecting means for detecting the fuel supply amount of the engine, the intake pressure detected by the intake pressure detecting means, and the fuel supply amount detected by the fuel supply amount detecting means, the engine is in steady operation. Steady exhaust pressure estimating means for estimating the steady exhaust pressure which is the exhaust pressure in the state, and a turbine for estimating the turbine speed of the turbocharger based on the steady exhaust pressure estimated by the steady exhaust pressure estimating means. Based on the speed estimation means and the turbine speed estimated by the turbine speed estimation means, the current operating state of the engine An actual exhaust pressure estimating means for estimating an actual exhaust pressure, which is the exhaust pressure in the engine, and an exhaust air passage of the engine, which is provided upstream of the turbocharger to continuously determine the excess air ratio of the engine in a predetermined excess air region. It is provided with a detectable air-fuel ratio sensor and an excess air ratio correction means for correcting the excess air ratio detected by the air-fuel ratio sensor based on the actual exhaust pressure estimated by the actual exhaust pressure estimation means. An excess air ratio detection device for a turbocharged engine. 14. The excess air ratio of the turbocharged engine according to claim 13, wherein the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake amount estimated from the intake pressure. Detection device. 15. The excess air ratio detecting device for a turbocharged engine according to claim 14, wherein the total intake air amount is corrected by an intake air temperature. 16. The steady exhaust pressure estimation means estimates the steady exhaust pressure based on the total intake amount and the fuel supply amount estimated from the intake pressure.
15. The excess air ratio detection device for an engine with a turbocharger according to any one of 15. 17. The turbine speed estimating means estimates the turbine speed using an exhaust gas flow rate ratio calculated based on the total intake air amount and an estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. Characteristic 13 to 1 characterized
7. An excess air ratio detection device for a turbocharged engine according to any one of 6 above. 18. The turbocharger according to claim 17, wherein the exhaust gas recirculation amount is calculated using an orifice coefficient obtained from a differential pressure between an actual exhaust pressure on the turbine upstream side and an intake pressure. Excessive air ratio detection device for engine with feeder. 19. The excess air ratio detection device for a turbocharged engine according to claim 17, wherein the exhaust gas recirculation amount is corrected by the exhaust gas temperature. 20. The air for a turbocharged engine according to claim 13, wherein the turbine speed estimation means estimates the turbine speed using turbine acceleration energy. Excess rate detector. 21. The air for a turbocharged engine according to claim 13, wherein the turbine speed estimating means estimates the turbine speed using a turbine load resistance. Excess rate detector. 22. The turbine speed estimating means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow rate ratio, integrates a deviation between the turbine acceleration energy and turbine load resistance, and calculates the turbine acceleration energy. 22. The turbo excess engine air excess ratio detection device according to claim 13, wherein the turbine speed is estimated by dividing the turbine speed by an inertia coefficient. 23. The turbocharger according to claim 13, wherein the actual exhaust pressure estimation means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. Excess air ratio detector for engine. 24. The turbocharger according to claim 13, wherein the excess air ratio correction means corrects the excess air ratio for each stroke of the engine. Excess air ratio detector for engine.