JP3161288B2 - Exhaust pressure detection device and excess air ratio detection device for turbocharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pressure detecting device and an excess air ratio detecting device for a turbocharged engine used in a fuel supply system or an exhaust purification system of an automobile turbocharged diesel engine or the like. About.

[0002]

2. Description of the Related Art The main harmful emission components of diesel engines include black smoke and unburned HC due to uneven fuel distribution.
Other like include NO _X due to combustion at high temperatures. The NO _X reduction means in a diesel engine, can not be reduced catalyst applications, such as gasoline engine for surplus oxygen is large, the fuel injection timing delay (timing retard) or water injection is studied. However, in the former case, the output and fuel consumption are inevitably reduced and CO and HC are increased. In the latter case, there are problems such as mounting of a water injection device and a water tank and mixing of water into lubricating oil. Therefore, practical use of an exhaust gas recirculation (EGR) device for recirculating exhaust gas, which is an inert substance, as EGR gas to a combustion chamber is being promoted because of its relatively simple structure and little adverse effect.

In an EGR device for a diesel engine,
When the recirculation amount of the EGR gas (hereinafter, referred to as EGR amount) becomes excessive, smoke emission is deteriorated due to a decrease in the excess air ratio, a sudden increase in HC, fuel consumption is reduced, and engine oil due to mixing of free carbon and particulates is reduced. Deterioration causes a decrease in engine durability and the like. Therefore, in order to the reduce of the NO _X while suppressing these problems as much as possible, by detecting the excess air ratio, electronically controlled for feedback controlling the EGR amount it is desirable. As a method of detecting the excess air ratio, there are a method using a CO ₂ analyzer and a method using a linear air-fuel ratio sensor (hereinafter, LA).
FS) is generally used.

However, as is well known, the CO ₂ analyzer can be used for bench tests and the like because of its large size and weight, but is not practical for use in vehicles. On the other hand, L
Japanese Patent Application Laid-Open No. 55-79 discloses an EGR device using AFS.
No. 64 and JP-A-63-201356. In the former EGR device, LA is added to the exhaust system.
The FS is mounted, and when the output current exceeds a predetermined threshold, the EGR valve is driven in the opening direction, and when the output current falls below the predetermined threshold, the EGR valve is driven in the closing direction. In the latter EGR device, the EGR amount is controlled based on an EGR amount control map using the lever opening of the fuel injection pump and the engine speed as parameters.
LAFS attached to exhaust system while driving R valve
The correction of the EGR valve opening degree (control map) is performed by the following.

[0005]

However, these LAFs
The EGR device that performs feedback control of the EGR amount using S also has the following problems. As is well known, L
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 inside is introduced into the atmosphere while the outer surface is exposed to exhaust gas. Utilizing the principle of an oxygen concentration cell, in which oxygen ions move and a current flows in proportion to the oxygen concentration (excess air ratio) in the exhaust gas. LAFS has a characteristic that, even when 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 differs depending on the level of the exhaust pressure. . Further, the LAFS does not operate normally unless the ambient temperature becomes equal to or higher than a predetermined value (activation temperature). Therefore, the LAFS is usually mounted on a collection portion of the exhaust manifold. Therefore, in an engine with a turbocharger having a large fluctuation in exhaust pressure on the upstream side of the turbine, the output current value of the LAFS also fluctuates greatly depending on the operation state of the turbocharger and the EGR device, and the excess air ratio can be accurately detected. There was a problem that it disappeared.

To solve this problem, Japanese Patent Publication No.
In Japanese Patent No. 41821, LAFS is provided upstream of the turbine.
Together with an exhaust pressure sensor, and according to the detection signal, L
A device that corrects a comparison current value to be compared with an AFS output current value has been proposed. However, the exhaust pressure sensor is an expensive component consisting of an element for converting pressure into an electric signal, an amplifier for amplifying the electric signal, and the like. In addition to the low initial cost and the high initial cost, there is also a problem that the running cost increases due to periodic inspection and replacement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an exhaust pressure detecting device and a principle thereof 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 of the present invention to provide an air excess ratio detecting device used.

[0008]

Therefore, according to the present invention, an intake pressure detecting means for detecting an intake pressure of an engine mounted on a vehicle and a turbine driven by 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 detected by the fuel supply amount detecting means A steady-state exhaust pressure estimating means for estimating a steady-state exhaust pressure which is an exhaust pressure when the engine is in a steady-state operating state, based on the supplied fuel supply amount, and a steady-state exhaust pressure estimated by the steady-state exhaust pressure estimating means. Turbine speed estimating means for estimating the turbine speed of the turbocharger based on 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.

According to a second aspect of the present invention, there is provided 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 air amount estimated from the intake pressure. In a preferable embodiment, the exhaust pressure detecting apparatus according to claim 2, said total intake air amount may be between those correction by the intake air temperature were performed.

According to a third aspect of the present invention, in the exhaust pressure detecting device according to the first or second aspect , the steady exhaust pressure estimating means determines the steady exhaust pressure based on the total intake air amount and the fuel supply amount estimated from the intake air pressure. Suggest what to estimate. According to a fourth aspect , in the exhaust pressure detecting device of the first to third aspects, the turbine speed estimating means is calculated based on the total intake amount and an estimated value of the exhaust gas recirculation amount by the exhaust gas recirculation device. A method for estimating turbine speed using the exhaust gas flow ratio is proposed.

[0011] In a preferable embodiment, the exhaust pressure detecting apparatus according to claim 4, said exhaust gas recirculation amount is calculated using the orifice coefficient obtained from the differential pressure between the actual exhaust pressure and intake pressure of the turbine upstream Is good . Also,
As a further preferred aspect , in the exhaust pressure detecting device according to the fourth aspect , the exhaust gas recirculation amount may be corrected based on the exhaust gas temperature.

In a preferred embodiment , claims 1 to 4 are provided.
In the exhaust pressure detecting device, the turbine speed estimating means, it is preferable is to estimate the turbine speed using the turbine acceleration energy. Also, other preferred embodiments
As, in the exhaust pressure detecting apparatus according to claim 1-4, the turbine speed estimating means, it is preferable is to estimate the turbine speed using the turbine load resistance.

In a further preferred aspect , in the exhaust pressure detecting apparatus according to any one of claims 1 to 4 , the turbine speed estimating means calculates a turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow ratio. integrating the deviation between the turbine acceleration energy of the turbine load resistor, which may be between those by dividing the turbine inertia coefficient estimating a turbine speed.

According to a fifth aspect of the present invention, there is provided the exhaust pressure detecting device according to the first to fourth aspects, wherein the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. Moreover, a further preferred embodiment, the exhaust pressure detecting apparatus according to claim 1 to 5, the actual exhaust gas pressure estimating means, it is preferable to estimate the actual exhaust pressure is performed for each one stroke of the engine.

According to a sixth aspect of the present invention , there is provided an intake pressure detecting means for detecting an intake pressure of an engine mounted on a vehicle, and a turbo for supercharging intake air to the engine by driving a turbine with exhaust gas of the engine. A supercharger, a fuel supply amount detecting means for detecting a fuel supply amount of the engine, and a fuel supply amount detected by the intake pressure detection means and the fuel supply amount detected by the fuel supply amount detection means, A steady-state exhaust pressure estimating means for estimating a steady-state exhaust pressure that is an exhaust pressure when the engine is in a steady-state operating state, and a turbine of the turbocharger based on the steady-state exhaust pressure estimated by the steady-state exhaust pressure estimating means. Turbine speed estimating means for estimating the speed, and the engine speed based on the turbine speed estimated by the turbine speed estimating means. Actual exhaust pressure estimating means for estimating the actual exhaust pressure which is the exhaust pressure in the current operating state of the engine, and an exhaust air ratio of the engine provided in the exhaust passage of the engine upstream of the turbocharger in a predetermined excess air region. And an excess air ratio correction means for correcting the excess air rate detected by the air-fuel ratio sensor based on the actual exhaust pressure estimated by the actual exhaust pressure estimation means. We propose a device for detecting excess engine air ratio.

According to a seventh aspect of the present invention, there is provided the air excess ratio detecting device according to the sixth aspect , wherein the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake air amount estimated from the intake pressure. In a preferred embodiment , in the air excess ratio detecting device according to claim 7 , the total intake air amount is corrected based on intake air temperature .
No.

According to an eighth aspect of the present invention, in the excess air ratio detecting device according to the sixth or seventh aspect , the steady exhaust pressure estimating means is configured to determine the steady exhaust pressure based on the total intake air amount and the fuel supply amount estimated from the intake air pressure. We propose something to estimate. According to a ninth aspect , in the air excess ratio detecting device according to the sixth to eighth aspects, the turbine speed estimating means is calculated based on the total intake amount and an estimated value of an exhaust gas recirculation amount by an exhaust gas recirculation device. A method for estimating the turbine speed using the exhaust gas flow ratio is proposed.

[0018] As a preferred mode, calculates the excess air rate detecting apparatus according to claim 9, the exhaust gas recirculation amount, using the orifice coefficient obtained from the differential pressure between the actual exhaust pressure and intake pressure of the turbine upstream Good to be . Moreover, a further preferred embodiment, the excess air rate detecting apparatus according to claim 9, the exhaust gas recirculation amount, it is preferable in which the correction by the exhaust gas temperature has been performed.

In a preferred embodiment , claims 6 to 9 are provided.
In the excess air ratio detecting device, the turbine speed estimating means may estimate the turbine speed using turbine acceleration energy. In another preferred embodiment ,
In the excess air rate detecting apparatus according to claim 6-9, the turbine speed estimating means, it is preferable to estimate the turbine speed using the turbine load resistance.

[0020] Further , as a further preferred embodiment ,
In the excess air rate detecting apparatus 6-9, the turbine speed estimating unit calculates the turbine acceleration energy based on the above stationary exhaust pressure and the exhaust gas flow rate, the deviation between the turbine acceleration energy of the turbine load resistor The turbine speed may be estimated by integrating and dividing this by the turbine inertia coefficient.

According to a tenth aspect of the present invention , in the air excess ratio detecting device of the sixth to ninth aspects, the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. In a further preferred embodiment
In the air excess ratio detecting device according to any one of claims 6 to 10 , it is preferable that the correction of the air excess ratio is performed for each stroke of the engine .
No.

[0022]

[Action] In the exhaust pressure detecting apparatus according to claim 1, after the steady exhaust pressure estimation means to estimate the steady exhaust gas pressure from a fuel supply amount detected by the intake pressure and the fuel supply quantity detecting means has detected that the intake pressure 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.

Also, in the exhaust pressure detecting device of the second aspect,
The steady exhaust pressure estimating means estimates a total intake air amount from the intake air pressure, and estimates a steady exhaust pressure from the total intake air amount. Also,
In a preferred aspect of the exhaust pressure detecting device of the second aspect , the steady exhaust pressure estimating means corrects the estimated total intake air amount based on the intake air temperature in order to prevent an excessive or underestimation due to thermal expansion or the like.

Further, in the exhaust pressure detecting device of the third aspect ,
The steady exhaust pressure estimating means estimates the total intake air amount from the intake air pressure and the engine rotation speed, and then estimates the steady exhaust pressure from the total intake air amount and the fuel supply amount. Further, the exhaust pressure detecting apparatus according to claim 4, turbine speed estimation means, the minus the exhaust gas recirculation amount from the total amount of intake air divided by the total intake air amount calculates the exhaust gas flow ratio, using to this Estimate turbine speed.

Further, the exhaust pressure detecting device according to claim 4 is preferable.
In a preferred embodiment , the orifice coefficient is obtained from a map or the like based on the differential pressure, and the exhaust gas recirculation amount is calculated using the orifice coefficient. In a further preferred aspect of the exhaust pressure detecting device according to claim 4 , the calculated exhaust gas recirculation amount is corrected based on the exhaust gas temperature in order to prevent excessive estimation due to thermal expansion. In a preferred aspect of the exhaust pressure detecting device according to claims 1 to 4 , the turbine speed estimating means calculates a turbine acceleration energy from an exhaust gas flow ratio and a steady exhaust pressure, and uses this to calculate a turbine acceleration energy. Estimate speed.

Further, the exhaust pressure detecting device according to the first to fourth aspects of the present invention
In another preferred aspect , the turbine speed estimating means calculates a turbine load resistance from a previous value of the turbine speed or the like, and estimates the turbine speed using the calculated load resistance. Claims 1 to
In a further preferred aspect of the exhaust pressure detecting device of 4 , the turbine speed estimating means calculates turbine acceleration energy by multiplying the steady exhaust pressure by an exhaust gas flow ratio, and integrates a deviation between the turbine acceleration energy and turbine load resistance. ,
This is divided by the turbine inertia coefficient to obtain the turbine speed.

Further, in the exhaust pressure detecting device according to the fifth aspect ,
The actual exhaust pressure estimating means calculates the actual exhaust pressure by multiplying the turbine speed by a conversion coefficient. Claims 1 to
In a further preferred aspect of the exhaust pressure detecting device of No. 5 , the actual exhaust pressure estimating means estimates the actual exhaust pressure at the start of the intake stroke of each cylinder, for example, based on an output signal from a crank angle sensor or the like.

Further, in the excess air rate detecting apparatus according to claim 6, the stationary exhaust pressure from the fuel supply quantity is constant exhaust pressure estimation means detects the intake pressure and the fuel supply quantity detecting means has detected that the intake pressure detecting means After the estimation, the turbine speed estimation means estimates the turbine speed from the steady exhaust pressure,
The actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed, and thereafter, the excess air ratio correcting means corrects the excess air ratio detected by the air-fuel ratio sensor with the actual exhaust pressure.

Further, in the excess air rate detecting apparatus according to claim 7, the constant exhaust pressure estimating means estimates the total amount of intake air from the intake pressure, estimates the steady exhaust pressure from the total intake air amount. In a preferred embodiment of the excess air ratio detecting device according to claim 7 , the steady exhaust pressure estimating means uses the intake air temperature based on the estimated total intake air amount so as to prevent an excessive or underestimation due to thermal expansion or the like. Make corrections.

Further, in the air excess ratio detecting device according to claim 8 , the steady exhaust pressure estimating means estimates the total intake air amount from the intake air pressure and the engine rotational speed, and then calculates a steady state from the total intake air amount and the fuel supply amount. Estimate exhaust pressure. Claim 9
In the excess air ratio detection device, the turbine speed estimating means includes:
Those from total intake air quantity by subtracting the exhaust gas recirculation amount by dividing the total intake air amount calculates the exhaust gas flow rate, estimates the turbine speed using the same.

The excess air ratio detecting device according to claim 9 is advantageous.
In a preferred embodiment , an orifice coefficient is obtained from a map or the like based on the differential pressure, and the exhaust gas recirculation amount is calculated using the orifice coefficient.
Further, the excess air ratio detection device according to claim 9 is more preferable.
In the aspect , the calculated exhaust gas recirculation amount is corrected based on the exhaust gas temperature in order to prevent excessive estimation due to thermal expansion.
Further, a preferable state of the excess air ratio detection device according to claims 6 to 9 is described.
In this method, the turbine speed estimating means calculates the turbine acceleration energy from the exhaust gas flow ratio and the steady exhaust pressure, and estimates the turbine speed using the calculated energy.

Further, the excess air ratio detecting device according to claims 6 to 9 is provided.
In another preferred aspect , the turbine speed estimating means calculates a turbine load resistance from a previous value of the turbine speed or the like,
This is used to estimate the turbine speed. Claim 6
In a further preferred embodiment of the air excess ratio detecting device of Nos. To 9 ,
The turbine speed estimating means calculates the turbine acceleration energy by multiplying the steady exhaust pressure by the exhaust gas flow ratio, integrates the deviation between the turbine acceleration energy and the turbine load resistance, and divides this by the turbine inertia coefficient to obtain the turbine speed. Ask for.

Further, in the air excess ratio detecting apparatus according to the tenth aspect , the actual exhaust pressure estimating means calculates the actual exhaust pressure by multiplying the turbine speed by a conversion coefficient. Claims
In a further preferred aspect of the air excess ratio detecting device of 6 to 10 , the air excess ratio estimating means is configured to output the air excess at the start of the intake stroke of each cylinder based on an output signal from a crank angle sensor or the like. Estimate the excess rate.

[0034]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an exhaust pressure detecting device and an excess air ratio detecting device according to an embodiment of the present invention; FIG. 1 is a schematic configuration diagram of an engine control system to which an EGR device is attached. In FIG. 1, reference numeral 1 denotes an in-line four-cylinder diesel 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. The engine 1 is provided with a distribution type fuel injection pump 6 having an electronic governor 5, 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 a fuel injection timing and an injection period are set by an electronic governor 5 controlled by an ECU (engine control unit) 8. In the figure, 9 is a water temperature sensor attached to the cylinder head 2 for detecting the cooling water temperature Tw, and 10 is a Ne sensor attached to the fuel injection pump 6 for detecting 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 the pipeline is connected to a compressor 14 of a turbocharger 13 and an interface. A cooler 15 is provided. In the figure, 16 is an intake air temperature sensor for detecting the intake air temperature Ta, and 17 is an intake pressure (Manifold Absolute).
Pressure) is a boost pressure sensor that detects Pb, and both are attached to the intake manifold 11. The 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, reference numeral 23 denotes a wastegate valve for releasing exhaust gas from the exhaust manifold 20 to the downstream of the turbine 21 when the boost pressure is excessively increased, and reference numeral 24 denotes a wastegate actuator. An oxidation catalyst 25 purifies CO and HC in the exhaust gas. In the engine 1 of this embodiment, the LAFS 26 that continuously outputs a current corresponding to the air-fuel ratio A / F on the lean side from the stoichiometric air-fuel ratio and the exhaust temperature Te that detects the exhaust gas temperature are set in the exhaust manifold 20. An exhaust gas temperature sensor 27 to be detected is attached.

On the other hand, the exhaust manifold 20 and the intake manifold 11 communicate with each other via an EGR pipe 30, and the pipeline of the EGR pipe 30 is connected to 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 of a negative pressure operation 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
An EGR position sensor that 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
The vacuum pump 43 is connected to the vacuum pump 43 via the negative pressure side EGR solenoid 42 and the negative pressure side EGR solenoid 42, and is connected to the atmosphere via a hose 44 and the atmosphere side EGR solenoid 45. The vacuum pump 43 is driven by the rotating shaft of the alternator 46, and always generates a negative pressure during operation of the engine 1. The negative pressure side EGR solenoid 42 communicates with the hoses 40 and 41 in the ON state, and connects the hoses 40 and 4 in the OFF state.
Block 1 The atmosphere side EGR solenoid 45 is O
The hose 44 communicates with the atmosphere in the FF state, and is shut off in the ON state. Therefore, both EGR solenoids 4
By turning on and off 2 and 45 as appropriate,
The negative pressure or the atmosphere is introduced into the negative pressure chamber 35 of the EGR valve 31, and the opening _AE of the EGR valve 31 is controlled.

The above-described ECU 8 is installed in the vehicle interior, and includes an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing a control program and the like, a central processing unit (CPU), and the like. On the input side of the ECU 8, detection information from various sensors and switches including the above-described sensors is input. Based on the detection information and the control map, the ECU 8 starts the electronic governor 5 and the other ECUs.
The drive control of the GR solenoids 42 and 45 is performed.

Hereinafter, the procedure for detecting the exhaust pressure and the procedure for detecting the excess air ratio in this embodiment will be described. The driver turns on the ignition key and the engine 1 starts,
Under a predetermined condition (in the case of this embodiment, the water temperature TW is 70 ° C. or more,
30 seconds or more after starting, boost pressure sensor 17 or EGR
When 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. I do. When this subroutine is started, the ECU 8 first determines the engine speed Ne (rpm) and the intake pressure P output from the Ne sensor 10 and the boost pressure sensor 17 in step S2 in FIG.
b (mmH ₂ O), the intake air amount map value Qao is shown in FIG.
Search from map. Next, the ECU 8 determines in step S
4, the intake air temperature Tb detected by the intake air temperature sensor 16
Based on (° C.), the intake air temperature is corrected for the intake air amount map value Qao by the following equation to calculate the total intake air amount Qa (g / st) sucked into the engine 1.

Qa = Qao · 273 / (273 + Tb) After calculating the total intake air amount Qa, the ECU 8 determines a steady state based on the total intake air amount Qa and the fuel supply amount Qf output from the electronic governor 5 in step S6. Exhaust pressure Pw (mmHg)
From a map (not shown). Next, the ECU 8
In step S8, the total intake air amount Qa and the previous EGR
Based on the quantity Qe _(i-1) , the exhaust gas flow ratio K
Calculate g.

Kg = 1-Qe_(i-1)/ Qa Next, the ECU 8 determines in step S10 that the exhaust gas flow
From the quantitative ratio Kg and the previously determined steady exhaust pressure Pw,
Then, the turbine acceleration energy F is calculated. F = Kg · Pw Next, in step S12, the ECU 8 calculates the conversion coefficient KL
Previous turbine speed V _(i-1)From the following formula,
Calculate anti-FL.

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

Pex = Kp · V _(i) The estimation of the exhaust pressure is now completed, but the ECU 8 then proceeds to step S18 where the actual exhaust pressure Pex and the atmospheric pressure Pa (760 m
Based on the differential pressure [Delta] P ₁ and m Hg), to find the pressure correction coefficient Kaf map of FIG. The pressure correction coefficient Kaf is
When the pressure difference ΔP ₁ is 0, the pressure difference is naturally 1.0. However, in the case of the present embodiment, 100 mm H
g It is set to decrease by 7% for each increase.

Next, the ECU 8 determines in step S20 that the pressure difference ΔP ₂ between the actual exhaust pressure Pex and the intake pressure Pb (ie,
The pressure in the EGR valve 31 is calculated, and in step S22, the orifice coefficient K _O is retrieved from the map shown in FIG. 8 based on the pressure difference ΔP ₂ . Thus, the orifice coefficient K _O
Is obtained, the ECU 8 calculates the current basic EGR amount Qeo by the following equation in step S24. In the following formula, A _E is E
EGR valve 3 detected by GR position sensor 36
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 proceeds to step S
At 26, the exhaust gas temperature T detected by the exhaust gas temperature sensor 27
e (that is, EGR gas temperature), the basic EGR amount Qeo is temperature-corrected by the following equation to obtain the current EGR amount Qeo.
e _(i) Calculate (g / st). The EGR calculated here
The quantity Qe _(i) is stored in the RAM, and is stored in the above-described step S8.
Is used to calculate the exhaust gas flow rate ratio Kg.

Qe _(i) = Qeo · 273 / (273 + Te) In the present embodiment, in parallel with the exhaust pressure detection subroutine, the ECU 8 sets the air pressure shown in the flowchart of FIG. The excess rate detection subroutine is repeatedly executed. When this subroutine starts, EC
U8 first reads the output current value Ipo of the LAFS 26 in step S30. Next, the ECU 8 determines in 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.

After that, the ECU 8 calculates the excess air ratio λ from the map shown in 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 controls the drive of 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. The details are not described here.

As described above, in the above-described 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 can be obtained without using an expensive and inferior exhaust pressure sensor. Can be detected accurately and quickly. Then, by performing the drive control of the EGR valve and electronic governor based on the detected excess air ratio, it can also be performed appropriately with a reflux and the fuel injection of the EGR gas in acceleration or deceleration, etc., black smoke and NO _X Emissions were extremely low.

Although the description of the concrete embodiment has been completed above, embodiments of the present invention are not limited to this embodiment. For example,
In the above embodiment, the present invention is applied to a diesel engine having 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 gist of the present invention.

[0050]

According to the exhaust pressure detecting apparatus 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 is driven by the exhaust gas of the engine. A turbocharger for supercharging the 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. A steady-state exhaust pressure estimating means for estimating a steady-state exhaust pressure which is an exhaust pressure when the engine is in a steady-state operation state based on the detected fuel supply amount; and a steady-state exhaust pressure estimated by the steady-state exhaust pressure estimating means. Turbine speed estimating means for estimating the turbine speed of the turbocharger based on An actual exhaust pressure estimating means for estimating the actual exhaust pressure, which is the exhaust pressure in the current operating state of the engine, based on the speed is provided. 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 of the present invention, in the exhaust pressure detecting device of the first aspect, the steady exhaust pressure estimating means includes:
Since the steady-state exhaust pressure is estimated based on the total intake air amount estimated from the intake pressure, the steady-state exhaust pressure can be accurately and quickly estimated. Further, the 請 Motomeko second exhaust pressure detecting device
In a preferred embodiment , the total intake air amount is preferably corrected based on the intake air temperature , whereby an excessive or underestimation due to thermal expansion or the like is prevented, and the total intake air amount can be estimated more accurately. .

Further, according to claim 3, claim 1 or
In the exhaust pressure detecting device of 2, 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 air pressure.
The steady exhaust pressure can be accurately and quickly estimated. According to a fourth aspect of the present invention, in the exhaust pressure detecting device of the first to third aspects, the turbine speed estimating means calculates the turbine speed based on the total intake amount and an 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 ratio, the turbine speed can be accurately and quickly estimated.

[0053] In addition, preferred the exhaust pressure detecting apparatus of the 請 Motomeko 4
As Shii embodiment, the exhaust gas recirculation amount, to be calculated using the orifice coefficient obtained from the differential pressure between the actual exhaust pressure and intake pressure of the turbine upstream well, to
The turbine speed can be estimated more accurately. Further, a more preferable aspect of the exhaust pressure detecting device according to claim 4 is provided.
It is preferable that the exhaust gas recirculation amount is corrected based on the exhaust gas temperature , whereby the turbine speed can be estimated more accurately.

[0054] Further, the exhaust pressure detecting apparatus 請 Motomeko 1-4
In a preferred embodiment, the turbine speed estimation means may to to estimate the turbine speed using the turbine acceleration energy, thereby estimating the turbine speed can be performed more accurately. Moreover, a further preferred embodiment of the exhaust pressure detecting apparatus 請 Motomeko 1-4, the turbine speed estimating unit may have to be estimated turbine speed using the turbine load resistor, thereby estimating turbine speed Can be performed more accurately.

[0055] Further, the exhaust pressure detecting apparatus 請 Motomeko 1-4
As a further preferred aspect , the turbine speed estimating means calculates a turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow ratio, integrates a deviation between the turbine acceleration energy and a turbine load resistance, and calculates well that by dividing the inertia coefficient to estimate the turbine speed, thereby estimating the turbine speed can be performed more accurately.

According to a fifth aspect of the present invention, in the exhaust pressure detecting device of the first to fourth aspects, the actual exhaust pressure estimating means estimates the actual exhaust pressure from the turbine speed and the conversion coefficient. The actual exhaust pressure can be estimated more accurately. Also, further exhaust pressure detecting apparatus 請 Motomeko 1-5
As a preferred embodiment , the actual exhaust pressure estimating means performs the estimation of the actual exhaust pressure for each stroke of the engine.
Therefore, the estimation at the time of transient operation or the like can be performed more accurately.

According to a sixth aspect of the present invention, there is provided an air-excess-ratio detecting device for detecting an intake pressure of an engine mounted on a vehicle, and driving the turbine with exhaust gas from the engine to drive 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 detected by the fuel supply amount detecting means. A steady exhaust pressure estimating means for estimating a steady exhaust pressure which is an exhaust pressure when the engine is in a steady operation state, based on the steady exhaust pressure estimated by the steady exhaust pressure estimating means. Turbine speed estimating means for estimating the turbine speed of the turbocharger, and a turbine estimated by the turbine speed estimating means. Based on the degree, the actual exhaust pressure estimating means for estimating the actual exhaust pressure which is the exhaust pressure in the current operating state of the engine, and provided on the exhaust passage of the engine upstream of the turbocharger, and in a predetermined excess air region. An air-fuel ratio sensor capable of continuously detecting the engine excess air ratio; and an excess air ratio correcting the excess air ratio detected by the air-fuel ratio sensor based on the actual exhaust pressure estimated by the actual exhaust pressure estimating means. Because it has a rate correction means, the excess air rate can be accurately and quickly performed,
It is possible to reduce NOx emission and black smoke emission in a diesel engine or the like.

According to a seventh aspect of the present invention, in the air excess ratio detecting device according to the sixth aspect , the steady exhaust pressure estimating means estimates the steady exhaust pressure based on the total intake air amount estimated from the intake pressure. In addition, the steady exhaust pressure can be accurately and quickly estimated. In a preferable embodiment of the excess air rate detection device 請 Motomeko 7, the total intake air amount may that it is assumed that correction by the intake air temperature is performed, which
As a result, the total intake air amount can be estimated more accurately.

Further, according to claim 8 , claim 6 or
In the excess air ratio detection device of 7, 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 air pressure. And quickly. According to the ninth aspect , in the air excess ratio detecting device according to the sixth to eighth aspects, the turbine speed estimating means is configured to perform the operation based on the total intake 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 ratio, the turbine speed can be accurately and quickly estimated.

[0060] Further, good air excess ratio detecting apparatus 請 Motomeko 9
As preferable embodiments, the exhaust gas recirculation amount, is to be calculated using the orifice coefficient obtained from the differential pressure between the actual exhaust pressure and intake pressure of the turbine upstream well, this
Thus, the turbine speed can be estimated more accurately. Also ,
A further preferred embodiment of the excess air rate detection device 請 Motomeko 9
It is preferable that the exhaust gas recirculation amount is corrected based on the exhaust gas temperature , whereby the turbine speed can be estimated more accurately.

[0061] In addition, the excess air ratio detecting apparatus of the 請 Motomeko 6-9
In a preferred embodiment , the turbine speed estimating means includes:
The turbine speed may be estimated using the turbine acceleration energy , so that the turbine speed can be estimated more accurately. As another preferred embodiment of the excess air rate detection device 請 Motomeko 6-9, the turbine speed estimation means may to to estimate the turbine speed using the turbine load resistance, thereby turbine speed Can be estimated more accurately.

[0062] In addition, the excess air ratio detecting apparatus of the 請 Motomeko 6-9
As a further preferred aspect , the turbine speed estimating means calculates turbine acceleration energy based on the steady exhaust pressure and the exhaust gas flow ratio, integrates a deviation between the turbine acceleration energy and turbine load resistance, and calculates by dividing the turbine inertia factor often to to estimate the turbine speed, thereby estimating the turbine speed can be performed more accurately.

Further, according to claim 10 , claims 6 to 9
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, so that the actual exhaust pressure can be estimated more accurately. Further, the excess air rate detecting apparatus 請 Motomeko 6-10
As a further preferred aspect, good correction of the excess air ratio to be performed at every one stroke of the engine, in which
More it allows estimation more accurately in a 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 illustrating a procedure of an exhaust pressure detection subroutine.

FIG. 3 is a flowchart illustrating 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 illustrating a procedure of an excess air ratio detection subroutine.

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

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

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

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

[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 Atmospheric side EGR solenoid

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02M 25/07 550 F02M 25/07 550M 570 570P

Claims (10)

(57) [Claims] 1. An intake pressure detecting means for detecting an intake pressure of an engine mounted on a vehicle, a turbocharger for supercharging intake air to the engine by driving a turbine with exhaust gas of the engine, Fuel supply amount detection means for detecting the fuel supply amount of the engine; and steady operation of the engine based on the intake pressure detected by the intake pressure detection means and the fuel supply amount detected by the fuel supply amount detection means. A steady-state exhaust pressure estimating means for estimating a steady-state exhaust pressure which is an exhaust pressure in the state, and a turbine for estimating a turbine speed of the turbocharger based on the steady-state exhaust pressure estimated by the steady-state exhaust pressure estimating means. Speed estimating means, based on the turbine speed estimated by the turbine speed estimating means, 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 of a turbocharged engine according to claim 1, wherein said steady exhaust pressure estimation means estimates the steady exhaust pressure based on a total intake air amount estimated from the intake pressure. apparatus. Wherein said constant exhaust pressure estimating means, and estimates the steady exhaust pressure based on the total intake air amount and the fuel supply amount estimated from the intake pressure, according to claim 1 or
3. The exhaust pressure detecting device for an engine with a turbocharger according to 2 . 4. A turbine speed estimating means for estimating a turbine speed using an exhaust gas flow ratio calculated based on the total intake amount and an estimated value of an exhaust gas recirculation amount by an exhaust gas recirculation device. The exhaust pressure detection device for an engine with a turbocharger according to any one of claims 1 to 3 , characterized in that: Wherein said actual exhaust gas pressure estimating means, and estimates the actual exhaust pressure from the above turbine speed conversion coefficient, turbocharger according to any one of claims 1-4 Exhaust pressure detection device for an engine. 6. An intake pressure detecting means for detecting an intake pressure of an engine mounted on a vehicle; a turbocharger for supercharging intake air to the engine by driving a turbine with exhaust gas of the engine; Fuel supply amount detection means for detecting the fuel supply amount of the engine; and steady operation of the engine based on the intake pressure detected by the intake pressure detection means and the fuel supply amount detected by the fuel supply amount detection means. A steady-state exhaust pressure estimating means for estimating a steady-state exhaust pressure which is an exhaust pressure in the state, and a turbine for estimating a turbine speed of the turbocharger based on the steady-state exhaust pressure estimated by the steady-state exhaust pressure estimating means. Speed estimating means, based on the turbine speed estimated by the turbine speed estimating means, An actual exhaust pressure estimating means for estimating an actual exhaust pressure which is an exhaust pressure of the engine, provided on the exhaust passage of the engine upstream of the turbocharger, and continuously measuring an excess air ratio of the engine in a predetermined excess air region. A detectable air-fuel ratio sensor; and an excess air ratio correction unit 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 unit. An excess air ratio detection device for an engine with a turbocharger. 7. The constant exhaust pressure estimating means, and estimates the steady exhaust pressure based on the total intake air amount estimated from the intake pressure, an excess air ratio of the turbocharged engine of claim 6, wherein Detection device. 8. The constant exhaust pressure estimating means, and estimates the steady exhaust pressure based on the total intake air amount and the fuel supply amount estimated from the intake pressure, claim 6 or
7. An excess air ratio detection device for a turbocharged engine according to claim 7 . 9. The turbine speed estimating means estimates a turbine speed using an exhaust gas flow ratio calculated based on the total intake air amount and an estimated value of an exhaust gas recirculation amount by an exhaust gas recirculation device. The apparatus for detecting an excess air ratio of an engine with a turbocharger according to any one of claims 6 to 8 , wherein: 10. The actual exhaust gas pressure estimating means, and estimates the actual exhaust pressure from the above turbine speed conversion coefficient, turbocharger according to any one of claims 6-9 Detector for excess air ratio of engine with engine.